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["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nDual Specificity Phosphatase 3 (DUSP3) regulates the innate immune response, with a putative role in angiogenesis. Modulating inflammation and perfusion contributes to renal conditioning against ischaemia/reperfusion (I/R). We postulate that the functional loss of DUSP3 is associated with kidney resistance to I/R.\n\n\nMethods\nTen C57BL/6 male WT and Dusp3−/− mice underwent right nephrectomy and left renal I/R (30 min/48 hours). Renal injury was assessed based on serum levels of urea (BUN) and Jablonski score. The expression of CD31 and VEGF vascular markers was quantified by RT‐qPCR and immuno‐staining. Renal resistivity index (RRI) was measured in vivo by Doppler ultrasound. Comparative phosphoproteomics was conducted using IMAC enrichment of phosphopeptides. Inflammatory markers were quantified at both mRNA and protein levels in ischaemic vs non‐ischaemic kidneys in WT vs Dusp3−/−.\n\n\nResults\nAt baseline, we located DUSP3 in renal glomeruli and endothelial cells. CD31‐positive vascular network was significantly larger in Dusp3−/− kidneys compared to WT, with a lower RRI in Dusp3−/− mice. Following I/R, BUN and Jablonski score were significantly lower in Dusp3−/− vs WT mice. Phosphoproteomics highlighted a down‐regulation of inflammatory pathways and up‐regulation of phospho‐sites involved in cell metabolism and VEGF‐related angiogenesis in Dusp3−/− vs WT ischaemic kidneys. Dusp3−/− ischaemic kidneys showed decreased mRNA levels of CD11b, TNF‐α, KIM‐1, IL‐6, IL‐1β and caspase‐3 compared to controls. The numbers of PCNA‐, F4‐80‐ and CD11b‐positive cells were reduced in Dusp3−/− vs WT kidneys post‐I/R.\n\n\nConclusion\nGenetic inactivation of Dusp3 is associated with kidney conditioning against I/R, possibly due to attenuated inflammation and improved perfusion.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAims\nIt is unknown how β‐adrenergic stimulation affects calcium dynamics in individual RyR2 clusters and leads to the induction of spontaneous calcium waves. To address this, we analysed spontaneous calcium release events in green fluorescent protein (GFP)‐tagged RyR2 clusters.\n\n\nMethods\nCardiomyocytes from mice with GFP‐tagged RyR2 or human right atrial tissue were subjected to immunofluorescent labelling or confocal calcium imaging.\n\n\nResults\nSpontaneous calcium release from single RyR2 clusters induced 91.4% ± 2.0% of all calcium sparks while 8.0% ± 1.6% were caused by release from two neighbouring clusters. Sparks with two RyR2 clusters had 40% bigger amplitude, were 26% wider, and lasted 35% longer at half maximum. Consequently, the spark mass was larger in two‐ than one‐cluster sparks with a median and interquartile range for the cumulative distribution of 15.7 ± 20.1 vs 7.6 ± 5.7 a.u. (P < .01). β2‐adrenergic stimulation increased RyR2 phosphorylation at s2809 and s2815, tripled the fraction of two‐ and three‐cluster sparks, and significantly increased the spark mass. Interestingly, the amplitude and mass of the calcium released from a RyR2 cluster were proportional to the SR calcium load, but the firing rate was not. The spark mass was also higher in 33 patients with atrial fibrillation than in 36 without (22.9 ± 23.4 a.u. vs 10.7 ± 10.9; P = .015).\n\n\nConclusions\nMost sparks are caused by activation of a single RyR2 cluster at baseline while β‐adrenergic stimulation doubles the mass and the number of clusters per spark. This mimics the shift in the cumulative spark mass distribution observed in myocytes from patients with atrial fibrillation.\n\n"]

["Acta Physiologica, Volume 233, Issue 3, November 2021. ", "\nAbstract\n\nAim\nSubcellular fractionation is often used to determine the subcellular localization of proteins, including whether a protein translocates to the nucleus in response to a given stimulus. Examining nuclear proteins in skeletal muscle is difficult because myonuclear proteins are challenging to isolate unless harsh treatments are used. This study aimed to determine the most effective method for isolating and preserving proteins in their native state in skeletal muscle.\n\n\nMethods\nWe compared the ability of detergents, commercially available kit‐based and K+‐based physiological methodologies for isolating myonuclear proteins from resting samples of human muscle by determining the presence of marker proteins for each fraction by western blot analyses.\n\n\nResults\nWe found that following the initial pelleting of nuclei, treatment with 1% Triton‐X 100, 1% CHAPS or 0.5% Na‐deoxycholate under various ionic conditions resulted in the nuclear proteins being either resistant to isolation or the proteins present behaving aberrantly. The nuclear proteins in brain tissue were also resistant to 1% Triton‐X 100 isolation. Here, we demonstrate aberrant behaviour and erroneous localization of proteins using the kit‐based method. The aberrant behaviour was the activation of Ca2+‐dependent protease calpain‐3, and the erroneous localization was the presence of calpain‐3 and troponin I in the nuclear fraction.\n\n\nConclusion\nOur findings indicate that it may not be possible to reliably determine the translocation of proteins between subcellular locations and the nucleus using subcellular fractionation techniques. This study highlights the importance of validating subcellular fractionation methodologies using several subcellular‐specific markers and solutions that are physiologically relevant to the intracellular milieu.\n\n"]

["Acta Physiologica, Volume 233, Issue 3, November 2021. ", "\nAbstract\nChemically skinned fibres allow the study of human muscle contractile function in vitro. A particularly important parameter is specific force (SF), that is, maximal isometric force divided by cross‐sectional area, representing contractile quality. Although SF varies substantially between studies, the magnitude and cause of this variability remains puzzling. Here, we aimed to summarize and explore the cause of variability in SF between studies. A systematic search was conducted in Medline, Embase and Web of Science databases in June 2020, yielding 137 data sets from 61 publications which studied healthy, young adults. Five‐fold differences in mean SF data were observed. Adjustments to the reported data for key methodological differences allowed between‐study comparisons to be made. However, adjustment for fibre shape, swelling and sarcomere length failed to significantly reduce SF variance (I2 = 96%). Interestingly, grouping papers based on shared authorship did reveal consistency within research groups. In addition, lower SF was found to be associated with higher phosphocreatine concentrations in the fibre activating solution and with Triton X‐100 being used as a skinning agent. Although the analysis showed variance across the literature, the ratio of SF in single fibres containing myosin heavy chain isoforms IIA or I was found to be consistent across research groups. In conclusion, whilst the skinned fibre technique is reliable for studying in vitro force generation of single fibres, the composition of the solution used to activate fibres, which differs between research groups, is likely to heavily influence SF values.\n"]

["Acta Physiologica, Volume 233, Issue 3, November 2021. ", "\nAbstract\n\nAim\nThis study investigates the role of calcineurin for angiotensin II (AngII)‐induced vascular remodelling with the help of a mouse model lacking the catalytic beta subunit of calcineurin (PPP3CB KO).\n\n\nMethods\nWildtype (WT) and PPP3CB KO mice were treated for 4 weeks with AngII followed by assessment of blood pressure, histological evaluation of aortas and mRNA analysis of aortic genes PPP3CB‐dependently regulated by AngII. Primary murine vascular smooth muscle cells (VSMCs) were used for qPCR, ELISA and Western Blot experiments as well as wound healing and cell proliferation assays.\n\n\nResults\nUpon AngII treatment, PPP3CB KO mice showed less aortic media thickening, lumen dilation and systolic blood pressure compared to WT mice. Next‐generation sequencing data of aortic tissue indicated an increase in extracellular matrix components (EMCs), cell migration and cell proliferation. A PPP3CB‐dependent increase in EMC was confirmed by qPCR in aorta and VSMCs. PPP3CB‐dependent stimulation of VSMC migration could be verified by wound healing assays but markers of enhanced cell proliferation were only detectable in aortic tissue of WT mice but not in isolated WT or KO VSMCs. We could demonstrate in VSMCs with pharmacological inhibitors that PPP3CB leads to enhanced heparin‐binding EGF‐like growth factor (HB‐EGF) secretion, epidermal growth factor receptor (EGFR) activation and consecutive stimulation of transforming growth factor β(TGFβ) and connective tissue growth factor (CTGF) signalling that enhances collagen expression.\n\n\nConclusion\nAngII‐induced vascular remodelling involves PPP3CB, which leads to enhanced EMC production, VSMC migration and sustained increase in systolic blood pressure via HBEGF/EGFR‐TGFβ‐CTGF signalling.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nSlc26a9 is a member of the Slc26 multifunctional anion transporter family. Polymorphisms in Slc26a9 are associated with an increased incidence of meconium ileus and diabetes in cystic fibrosis patients. We investigated the expression of Slc26a9 in the murine pancreatic ducts, islets and parenchyma, and elucidated its role in pancreatic ductal electrolyte and fluid secretion and endocrine function.\n\n\nMethods\nPancreatic Slc26a9 and CFTR mRNA expression, fluid and bicarbonate secretion were assessed in slc26a9−/− mice and their age‐ and sex‐matched wild‐type (wt) littermates. Glucose and insulin tolerance tests were performed.\n\n\nResults\nCompared with stomach, the mRNA expression of Slc26a9 was low in pancreatic parenchyma, 20‐fold higher in microdissected pancreatic ducts than parenchyma, and very low in islets. CFTR mRNA was ~10 fold higher than Slc26a9 mRNA expression in each pancreatic cell type. Significantly reduced pancreatic fluid secretory rates and impaired glucose tolerance were observed in female slc26a9−/− mice, whereas alterations in male mice did not reach statistical significance. No significant difference was observed in peripheral insulin resistance in slc26a9−/− compared to sex‐ and aged‐matched wt controls. In contrast, isolated slc26a9−/− islets in short term culture displayed no difference in insulin content, but a significantly reduced glucose‐stimulated insulin secretion compared to age‐ and sex‐matched wt islets, suggesting that the impaired glucose tolerance in the absence of Slc26a9 expression these is a pancreatic defect.\n\n\nConclusions\nDeletion of Slc26a9 is associated with a reduction in pancreatic fluid secretion and impaired glucose tolerance in female mice. The results underline the importance of Slc26a9 in pancreatic physiology.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nArteriogenesis constitutes the most efficient endogenous rescue mechanism in cases of cerebral ischaemia. The aim of this work was to investigate whether angiotensin‐converting enzyme inhibitors (ACEi) stimulates, and angiotensin II receptor type 1 blockers (ARB) inhibits cerebral collateral growth by applying a three‐vessel occlusion (3‐VO) model in rat.\n\n\nMethods\nCerebral collateral growth was measured post 3‐VO (1) by assessing blood flow using the cerebrovascular reserve capacity (CVRC) technique, and (2) by assessing vessel diameters in the posterior cerebral artery (PCA) via the evaluation of latex angiographies. A stimulatory effect on arteriogenesis was investigated for ACEi administration ± bradykinin receptor 1 (B1R) and 2 (B2R) blockers, and an inhibitory effect was analysed for ARB administration. Results were validated by immunohistochemical analysis and mechanistic data were collected by human umbilical vein endothelial cell (HUVEC) viability or scratch assay and monocyte (THP‐1) migration assay.\n\n\nResults\nAn inhibitory effect of ARB on arteriogenesis could not be demonstrated. However, collateral growth measurements demonstrated a significantly increased CVRC and PCA diameters in the ACEi group. ACEi stimulates cell viability and migration, which could be partially reduced by additional administration of bradykinin receptor 1 inhibitor (B1Ri).\nACEi inhibits the degradation of pro‐arteriogenic bradykinin derivatives, but combined ACEi + B1Ri + B1Ri (BRB) treatment did not reverse the stimulatory effect. Yet, co‐administration of ACEi + BRB enhances arteriogenesis and cell migration.\n\n\nConclusion\nWe demonstrate a potent stimulatory effect of ACEi on cerebral arteriogenesis in rats, presumable via B1R. However, results imply a pleiotropic and compensatory effect of ACEi on bradykinin receptor‐stimulated arteriogenesis.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\nThe molecular link between SARS‐CoV‐2 infection and susceptibility is not well understood. Nonetheless, a bi‐directional relationship between SARS‐CoV‐2 and diabetes has been proposed. The angiotensin‐converting enzyme 2 (ACE2) is considered as the primary protein facilitating SARS‐CoV and SARS‐CoV‐2 attachment and entry into the host cells. Studies suggested that ACE2 is expressed in the endocrine cells of the pancreas including beta cells, in addition to the lungs and other organs; however, its expression in the islets, particularly beta cells, has been met with some contradiction. Importantly, ACE2 plays a crucial role in glucose homoeostasis and insulin secretion by regulating beta cell physiology. Given the ability of SARS‐CoV‐2 to infect human pluripotent stem cell‐derived pancreatic cells in vitro and the presence of SARS‐CoV‐2 in pancreatic samples from COVID‐19 patients strongly hints that SARS‐CoV‐2 can invade the pancreas and directly cause pancreatic injury and diabetes. However, more studies are required to dissect the underpinning molecular mechanisms triggered in SARS‐CoV‐2‐infected islets that lead to aggravation of diabetes. Regardless, it is important to understand the function of ACE2 in the pancreatic islets to design relevant therapeutic interventions in combatting the effects of SARS‐CoV‐2 on diabetes pathophysiology. Herein, we detail the function of ACE2 in pancreatic beta cells crucial for regulating insulin sensitivity, secretion, and glucose metabolism. Also, we discuss the potential role played by ACE2 in aiding SARS‐COV‐2 entry into the pancreas and the possibility of ACE2 cooperation with alternative entry factors as well as how that may be linked to diabetes pathogenesis.\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nWith diabetes comes a significant risk of macrovascular and microvascular complications. Circulating aldosterone levels increase in patients with diabetes. Aldosterone can directly affect vascular function via activation of the mineralocorticoid receptor (MR). We hypothesized that aldosterone via endothelial MR impairs endothelial function in a murine model of experimental diabetes.\n\n\nMethod\nEndothelial cell‐specific mineralocorticoid receptor knockout MRflox/flox;Tie2‐Cre mice (ECMR‐KO) and wild‐type FVB littermates were subjected to an experimental type‐1 diabetic model by low dose streptozotocin injections (55mg/kg/day) for five consecutive days. After 10 weeks of diabetes, second‐order mesenteric resistance arteries were perfused ex vivo to evaluate vessel contractility and endothelial function. The effect of ex vivo incubation with aldosterone with and without the antagonist, spironolactone was determined.\n\n\nResults\nDiabetic ECMR‐KO and wild‐type mice had similar, elevated, plasma aldosterone concentration while only diabetic wild‐type mice displayed elevated urine albumin excretion and cardiac and kidney hypertrophy at 10 weeks. There were no differences in contraction (Emax and EC50) to thromboxane receptor agonist (U46619) and elevated K+ between groups. Wild‐type diabetic mice showed impaired acetylcholine (ACh)‐dependent relaxation, while diabetic ECMR‐KO mice had intact ACh‐mediated relaxation. Aldosterone incubation ex vivo impaired ACh mediated relaxation and rendered responses similar to diabetic WT arteries. Direct, ex vivo aldosterone effects were absent in ECMR‐KO animals. Ex vivo inhibitory effects of aldosterone on endothelial relaxation in arteries from WT were abolished by spironolactone.\n\n\nConclusion\nThese findings show that endothelial cell mineralocorticoid receptor activation accounts for diabetes‐induced systemic endothelial dysfunction in experimental diabetes and may explain the cardiovascular protection by MR antagonists in diabetes.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nWe aimed at identifying potential roles of vesicular monoamine transporter 2, also known as Solute Carrier protein 18 A2 (SLC18A2) (hereafter, Vmat2), in brain monoamine regulation, their turnover, behaviour and brain development using a novel zebrafish model.\n\n\nMethods\nA zebrafish strain lacking functional Vmat2 was generated with the CRISPR/Cas9 system. Larval behaviour and heart rate were monitored. Monoamines and their metabolites were analysed with high‐pressure liquid chromatography. Amine synthesising and degrading enzymes, and genes essential for brain development, were analysed with quantitative PCR, in situ hybridisation and immunocytochemistry.\n\n\nResults\nThe 5‐bp deletion in exon 3 caused an early frameshift and was lethal within 2 weeks post‐fertilisation. Homozygous mutants (hereafter, mutants) displayed normal low locomotor activity during night‐time but aberrant response to illumination changes. In mutants dopamine, noradrenaline, 5‐hydroxytryptamine and histamine levels were reduced, whereas levels of dopamine and 5‐hydroxytryptamine metabolites were increased, implying elevated monoamine turnover. Consistently, there were fewer histamine, 5‐hydroxytryptamine and dopamine immunoreactive cells. Cellular dopamine immunostaining, in wild‐type larvae more prominent in tyrosine hydroxylase 1 (Th1)‐expressing than in Th2‐expressing neurons, was absent in mutants. Despite reduced dopamine levels, mutants presented upregulated dopamine‐synthesising enzymes. Further, in mutants the number of histidine decarboxylase‐expressing neurons was increased, notch1a and pax2a were downregulated in brain proliferative zones.\n\n\nConclusion\nLack of Vmat2 increases monoamine turnover and upregulates genes encoding amine‐synthesising enzymes, including histidine decarboxylase. Notch1a and pax2a, genes implicated in stem cell development, are downregulated in mutants. The zebrafish vmat2 mutant strain may be a useful model to study how monoamine transport affects brain development and function, and for use in drug screening.\n\n"]

["Acta Physiologica, Volume 232, Issue 4, August 2021. ", "\nAbstract\n\nAim\nMicroRNAs play an important role in the maintenance of cellular functions by fine‐tuning gene expression levels. The aim of the current study was to identify genetically caused changes in microRNA expression which associate with islet dysfunction in diabetic mice.\n\n\nMethods\nTo identify novel microRNAs involved in islet dysfunction, transcriptome and miRNome analyses were performed in islets of obese, diabetes‐susceptible NZO and diabetes‐resistant B6‐ob/ob mice and results combined with quantitative trait loci (QTL) and functional in vitro analysis.\n\n\nResults\nIn islets of NZO and B6‐ob/ob mice, 94 differentially expressed microRNAs were detected, of which 11 are located in diabetes QTL. Focusing on conserved microRNAs exhibiting the strongest expression difference and which have not been linked to islet function, miR‐205‐5p was selected for further analysis. According to transcriptome data and target prediction analyses, miR‐205‐5p affects genes involved in Wnt and calcium signalling as well as insulin secretion. Over‐expression of miR‐205‐5p in the insulinoma cell line INS‐1 increased insulin expression, left‐shifted the glucose‐dependence of insulin secretion and supressed the expression of the diabetes gene TCF7L2. The interaction between miR‐205‐5p and TCF7L2 was confirmed by luciferase reporter assay.\n\n\nConclusion\nMiR‐205‐5p was identified as relevant microRNA involved in islet dysfunction by interacting with TCF7L2.\n\n"]

["Acta Physiologica, Volume 232, Issue 4, August 2021. ", "\nAbstract\nGestational diabetes mellitus (GDM) shows a deficiency in the metabolism of D‐glucose and other nutrients, thereby negatively affecting the foetoplacental vascular endothelium. Maternal hyperglycaemia and hyperinsulinemia play an important role in the aetiology of GDM. A combination of these and other factors predisposes women to developing GDM with pre‐pregnancy normal weight, viz. classic GDM. However, women with GDM and prepregnancy obesity (gestational diabesity, GDty) or overweight (GDMow) show a different metabolic status than women with classic GDM. GDty and GDMow are associated with altered l‐arginine/nitric oxide and insulin/adenosine axis signalling in the human foetoplacental microvascular and macrovascular endothelium. These alterations differ from those observed in classic GDM. Here, we have reviewed the consequences of GDty and GDMow in the modulation of foetoplacental endothelial cell function, highlighting studies describing the modulation of intracellular pH homeostasis and the potential implications of NO generation and adenosine signalling in GDty‐associated foetal vascular insulin resistance. Moreover, with an increase in the rate of obesity in women of childbearing age worldwide, the prevalence of GDty is expected to increase in the next decades. Therefore, we emphasize that women with GDty and GDMow should be characterized with a different metabolic state from that of women with classic GDM to develop a more specific therapeutic approach for protecting the mother and foetus.\n"]

["Acta Physiologica, Volume 232, Issue 4, August 2021. ", "\nAbstract\n\nAim\nOur previous studies have demonstrated the importance of dietary factors in the determination of hypertension in Dahl salt‐sensitive (SS) rats. Since the gut microbiota has been implicated in chronic diseases like hypertension, we hypothesized that dietary alterations shift the microbiota to mediate the development of salt‐sensitive hypertension and renal disease.\n\n\nMethods\nThis study utilized SS rats from the Medical College of Wisconsin (SS/MCW) maintained on a purified, casein‐based diet (0.4% NaCl AIN‐76A, Dyets) and from Charles River Laboratories (SS/CRL) fed a whole grain diet (0.75% NaCl 5L79, LabDiet). Faecal 16S rDNA sequencing was used to phenotype the gut microbiota. Directly examining the contribution of the gut microbiota, SS/CRL rats were administered faecal microbiota transfer (FMT) experiments with either SS/MCW stool or vehicle (Vehl) in conjunction with the HS AIN‐76A diet.\n\n\nResults\nSS/MCW rats exhibit renal damage and inflammation when fed high salt (HS, 4.0% NaCl AIN‐76A), which is significantly attenuated in SS/CRL. Gut microbiota phenotyping revealed distinct profiles that correlate with disease severity. SS/MCW FMT worsened the SS/CRL response to HS, evidenced by increased albuminuria (67.4 ± 6.9 vs 113.7 ± 25.0 mg/day, Vehl vs FMT, P = .007), systolic arterial pressure (158.6 ± 5.8 vs 177.8 ± 8.9 mmHg, Vehl vs FMT, P = .09) and renal T‐cell infiltration (1.9‐fold). Amplicon sequence variant (ASV)‐based analysis of faecal 16S rDNA sequencing data revealed taxa that significantly shifted with FMT: Erysipelotrichaceae_2, Parabacteroides gordonii, Streptococcus alactolyticus, Bacteroidales_1, Desulfovibrionaceae_2, Ruminococcus albus.\n\n\nConclusions\nThese data demonstrate that dietary modulation of the gut microbiota directly contributes to the development of Dahl SS hypertension and renal injury.\n\n"]

["Acta Physiologica, Volume 232, Issue 4, August 2021. ", "\nAbstract\n\nAim\nThere is mounting evidence that TRPA1 has a role in cardiac physiology and pathophysiology. We aim to clarify the site of TRPA1 expression in the heart and in particular whether the channel is expressed in cardiomyocytes.\n\n\nMethods\nDue to the high calcium conductance of TRPA1, and marginal calcium changes being detectable, microfluorimetry in primary mouse cardiomyocytes, and in the cardiomyocyte cell lines H9c2 and HL‐1, was applied. TRPA1 mRNA in mouse and human hearts, primary cardiomyocytes, and the cardiac cell lines were quantified. Dorsal root ganglia served as control for both methods.\n\n\nResults\nIn addition to AITC, the more potent and specific TRPA1 agonists JT010 and PF‐4840154 failed to elicit a TRPA1‐mediated response in native and electrically paced primary cardiomyocytes, and the cardiomyocyte cell lines H9c2 and HL‐1. There were only marginal levels of TRPA1 mRNA in cardiomyocytes and cardiac cell lines, also in conditions of cell differentiation or inflammation, which might occur in pathophysiological conditions. Similarly, TRPV1 agonist capsaicin did not activate primary mouse cardiomyocytes, did not alter electrically paced activity in these, and did not activate H9c2 cells or alter spontaneous activity of HL‐1 cells. Human pluripotent stem cells differentiated to cardiomyocytes had no relevant TRPA1 mRNA levels. Also in human post‐mortem heart samples, TRPA1 mRNA levels were substantially lower compared with the respective dorsal root ganglion.\n\n\nConclusion\nThe results do not question a role of TRPA1 in the heart but exclude a direct effect in cardiomyocytes.\n\n"]

["Acta Physiologica, Volume 232, Issue 4, August 2021. ", "\nAbstract\n\nAim\nFluid and macromolecule transport from the interstitium into and through lymphatic vessels is necessary for tissue homeostasis. While lymphatic capillary structure suggests that passive, paracellular transport would be the predominant route of macromolecule entry, active caveolae‐mediated transcellular transport has been identified in lymphatic endothelial cells (LECs) in vitro. Caveolae also mediate a wide array of endothelial cell processes, including nitric oxide regulation. Thus, how does the lack of caveolae impact “lymphatic function”?\n\n\nMethods\nVarious aspects of lymphatic transport were measured in mice constitutively lacking caveolin‐1 (“CavKO”), the protein required for caveolae formation in endothelial cells, and in mice with a LEC‐specific Cav1 gene deletion (Lyve1‐Cre x Cav1flox/flox; “LyCav”) and ex vivo in their vessels and cells.\n\n\nResults\nIn each model, lymphatic architecture was largely unchanged. The lymphatic conductance, or initial tissue uptake, was significantly higher in both CavKO mice and LyCav mice by quantitative microlymphangiography and the permeability to 70 kDa dextran was significantly increased in monolayers of LECs isolated from CavKO mice. Conversely, transport within the lymphatic system to the sentinel node was significantly reduced in anaesthetized CavKO and LyCav mice. Isolated, cannulated collecting vessel studies identified significantly reduced phasic contractility when lymphatic endothelium lacks caveolae. Inhibition of nitric oxide synthase was able to partially restore ex vivo vessel contractility.\n\n\nConclusion\nMacromolecule transport across lymphatics is increased with loss of caveolae, yet phasic contractility reduced, resulting in reduced overall lymphatic transport function. These studies identify lymphatic caveolar biology as a key regulator of active lymphatic transport functions.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nWe aimed to evaluate whether the streptozotocin‐induced diabetic model can generate lung functional, histological and biochemical impairments and whether moderate exercise can prevent these changes.\n\n\nMethods\nWistar rats were assigned to control (CTRL), exercise (EXE), diabetic (D) and diabetic with exercise (D+EXE) groups. We used the n5‐STZ model of diabetes mellitus triggered by a single injection of streptozotocin (STZ, 120 mg/kg b.w., i.p.) in newborn rats on their 5th day of life. EXE and D+EXE rats were trained by running on a motorized treadmill, 5 days a week for 9 weeks. Blood glucose, body weight, food intake, exercise capacity, lung mechanics, morphology, and antioxidant enzymatic activity were analysed.\n\n\nResults\nOn the 14th week of life, diabetic rats exhibited a significant impairment in post‐prandial glycaemia, glucose tolerance, body weight, food intake, lung function (tissue viscance, elastance, Newtonian resistance and hysteresis), morphological parameters, redox balance and exercise capacity. Physical training completely prevented the diabetes‐induced alterations, except for those on fasting blood glucose, which nevertheless remained stable.\n\n\nConclusions\nMild diabetes in n5‐STZ‐treated rats jeopardized pulmonary mechanics, morphology and redox balance, which confirms the occurrence of diabetes‐induced pneumopathy. Moreover, moderate exercise completely prevented all diabetes‐induced respiratory alterations.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nCardiac arrhythmias and sudden deaths have diurnal rhythms in humans. The underlying mechanisms are unknown. Mice with cardiomyocyte‐specific disruption of the molecular clock genes have lower heart rate than control. Because changes in the QT interval on the electrocardiogram is a clinically used marker of risk of arrhythmias, we sought to test if the biological rhythms of QT intervals are dependent on heart rate and if this dependency is changed when the molecular clock is disrupted.\n\n\nMethods\nWe implanted radio transmitters in male mice with cardiomyocyte‐specific Bmal1 knockout (CBK) and in control mice and recorded 24‐h ECGs under diurnal and circadian conditions. We obtained left ventricular monophasic action potentials during pacing in hearts ex vivo.\n\n\nResults\nBoth RR and QT intervals were longer in conscious CBK than control mice (RR: 117 ± 7 vs 110 ± 9 ms, P < .05; and QT: 53 ± 4 vs 48 ± 2 ms, P < .05). The prolonged QT interval was independent of the slow heart rate in CBK mice. The QT interval exhibited diurnal and circadian rhythms in both CBK and control mice. The action potential duration was longer in CBK than in control mice, indicating slower repolarization. Action potential alternans occurred at lower pacing rate in hearts from CBK than control mice (12 ± 3 vs 16 ± 2 Hz, respectively, P < .05).\n\n\nConclusion\nThe bradycardic CBK mice have prolonged ventricular repolarization independent of the heart rate. Diurnal and circadian rhythms in repolarization are preserved in CBK mice and are not a consequence of the 24‐h rhythm in heart rate. Arrhythmia vulnerability appears to be increased when the cardiac clock is disrupted.\n\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\nCa2+ mishandling is a common feature in several cardiovascular diseases such as heart failure (HF). In many cases, impairment of key players in intracellular Ca2+ homeostasis has been identified as the underlying mechanism of cardiac dysfunction and cardiac arrhythmias associated with HF. In this review, we summarize primary novel findings related to Ca2+ mishandling in HF progression. HF research has increasingly focused on the identification of new targets and the contribution of their role in Ca2+ handling to the progression of the disease. Recent research studies have identified potential targets in three major emerging areas implicated in regulation of Ca2+ handling: the innate immune system, bone metabolism factors and post‐translational modification of key proteins involved in regulation of Ca2+ handling. Here, we describe their possible contributions to the progression of HF.\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\nIn arterial smooth muscle cells, changes in availability of integral membrane proteins influence the regulation of blood flow and blood pressure, which is critical for human health. However, the mechanisms that coordinate the trafficking and membrane expression of specific receptors and ion channels in vascular smooth muscle are poorly understood. In the vasculature, very little is known about microtubules, which form a road network upon which proteins can be transported to and from the cell membrane. This review article summarizes the impact of the microtubule network on arterial contractility, highlighting the importance of the network, with an emphasis on our recent findings regarding the trafficking of the voltage‐dependent Kv7 channels.\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\n\nAim\nGlial fibrillary acidic protein (GFAP) molecularly associates with aquaporin 4 (AQP4) in astrocytic plasticity. Here, we further examined how AQP4 modulates osmotic effects on vasopressin (VP) neurons in rat supraoptic nucleus (SON) through interactions with GFAP in astrocytes.\n\n\nMethods\nBrain slices from adult male rats were kept under osmotic stimulation. Western blot, co‐immunoprecipitation, immunohistochemistry and patch‐clamp recordings were used for analysis of expressions and interactions between GFAP and AQP4, astrocyte‐specific proteins in the SON, as well as their influence on VP neuronal activity. Data were analysed using SPSS software.\n\n\nResults\nHyposmotic challenge (HOC) of acute SON slices caused an early (within 5 minutes) and transient increase in the colocalization of AQP4 with GFAP filaments. This effect was prominent at astrocytic processes surrounding VP neuron somata and was accompanied by inhibition of VP neuronal activity. Similar HOC effect was seen in the SON isolated from rats subjected to in vivo HOC, wherein a transiently increased molecular association between GFAP and AQP4 was detected using co‐immunoprecipitation. The late stage rebound excitation (10 minutes) of VP neurons in brain slices subjected to HOC and the associated astrocytic GFAP’s ‘return to normal’ were both hampered by 2‐(nicotinamide)‐1,3,4‐thiadiazole, a specific AQP4 channel blocker that itself did not influence VP neuronal activity. Moreover, this agent prevented hyperosmotic stress‐evoked excitation of VP neurons and associated reduction in GFAP filaments.\n\n\nConclusion\nThese findings indicate that osmotically driven increase in VP neuronal activity requires the activation of AQP4, which determines a retraction of GFAP filaments.\n\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\n\nAim\nMitophagy is the regulated process that targets damaged or dysfunctional mitochondria for lysosomal‐mediated removal. This process is an essential element of mitochondrial quality control, and dysregulation of mitophagy may contribute to a host of diseases, most notably neurodegenerative conditions such as Parkinson's disease. Mitochondria targeted for mitophagic destruction are molecularly marked by the ubiquitination of several outer mitochondrial membrane (OMM) proteins. This ubiquitination is positively regulated, in part, by the mitochondrial‐targeted kinase PINK1 and the E3 ubiquitin ligase Parkin. In contrast, the reverse phenomenon, deubiquitination, removes ubiquitin from Parkin substrates embedded in the OMM proteins, antagonizing mitophagy. Recent evidence suggests that the mitochondrial deubiquitinase USP30 negatively regulates Parkin‐mediated mitophagy, providing opportunities to identify USP30 inhibitors and test for their effects in augmenting mitophagy. Here we will characterize a USP30 inhibitor and demonstrate how the pharmacological inhibition of USP30 can augment stress‐induced mitophagic flux.\n\n\nMethods\nWe have conducted mitophagy and mitochondrial analyses in cultured cells. We have determined the plasma pharmacokinetics of the USP30 inhibitor in mice and conducted analyses using the mt‐Keima mice to measure in vivo mitophagy directly.\n\n\nResults\nThe compound has minimal mitochondrial toxicity in cultured cells and is tolerated well in mice. Interestingly, we demonstrated tissue‐specific induction of mitophagy following USP30 pharmacological inhibition. In particular, pharmacological inhibition of USP30 induces a significant increase in cardiac mitophagy without detriment to cardiac function.\n\n\nConclusion\nOur data support the evidence that USP30 inhibition may serve as a specific strategy to selectively increase mitophagic flux, allowing for the development of novel therapeutic approaches.\n\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\n\nAim\nType A intercalated cells of the renal collecting duct participate in the maintenance of the acid/base balance through their capacity to adapt proton secretion to homeostatic requirements. We previously showed that increased proton secretion stems in part from the enlargement of the population of proton secreting cells in the outer medullary collecting duct through division of fully differentiated cells, and that this response is triggered by growth/differentiation factor 15. This study aimed at deciphering the mechanism of acid load‐induced secretion of Gdf15 and its mechanism of action.\n\n\nMethods\nWe developed an original method to evaluate the proliferation of intercalated cells and applied it to genetically modified or pharmacologically treated mice under basal and acid‐loaded conditions.\n\n\nResults\nGdf15 is secreted by principal cells of the collecting duct in response to the stimulation of vasopressin receptors. Vasopressin‐induced production of cAMP triggers activation of AMP‐stimulated kinases and of Na,K‐ATPase, and induction of p53 and Gdf15. Gdf15 action on intercalated cells is mediated by ErbB2 receptors, the activation of which triggers the expression of cyclin d1, of p53 and anti‐proliferative genes, and of Egr1.\n\n\nConclusion\nAcidosis‐induced proliferation of intercalated cells results from a cross talk with principal cells which secrete Gdf15 in response to their stimulation by vasopressin. Thus, vasopressin is a major determinant of the collecting duct cellular homeostasis as it promotes proliferation of intercalated cells under acidosis conditions and of principal cells under normal acid‐base status.\n\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\nSystemic arterial hypertension and heart failure are cardiovascular diseases that affect millions of individuals worldwide. They are characterized by a change in the autonomic nervous system balance, highlighted by an increase in sympathetic activity associated with a decrease in parasympathetic activity. Most therapeutic approaches seek to treat these diseases by medications that attenuate sympathetic activity. However, there is a growing number of studies demonstrating that the improvement of parasympathetic function, by means of pharmacological or electrical stimulation, can be an effective tool for the treatment of these cardiovascular diseases. Therefore, this review aims to describe the advances reported by experimental and clinical studies that addressed the potential of cholinergic stimulation to prevent autonomic and cardiovascular imbalance in hypertension and heart failure. Overall, the published data reviewed demonstrate that the use of central or peripheral acetylcholinesterase inhibitors is efficient to improve the autonomic imbalance and hemodynamic changes observed in heart failure and hypertension. Of note, the baroreflex and the vagus nerve activation have been shown to be safe and effective approaches to be used as an alternative treatment for these cardiovascular diseases. In conclusion, pharmacological and electrical stimulation of the parasympathetic nervous system has the potential to be used as a therapeutic tool for the treatment of hypertension and heart failure, deserving to be more explored in the clinical setting.\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\n\nAim\nHighly prevalent diseases such as insulin resistance and heart failure are characterized by reduced metabolic flexibility and reserve. We tested whether Na/K‐ATPase (NKA)‐mediated regulation of Src kinase, which requires two NKA sequences specific to the α1 isoform, is a regulator of metabolic capacity that can be targeted pharmacologically.\n\n\nMethods\nMetabolic capacity was challenged functionally by Seahorse metabolic flux analyses and glucose deprivation in LLC‐PK1‐derived cells expressing Src binding rat NKA α1, non‐Src‐binding rat NKA α2 (the most abundant NKA isoform in the skeletal muscle), and Src binding gain‐of‐function mutant rat NKA α2. Mice with skeletal muscle‐specific ablation of NKA α1 (skα1−/−) were generated using a MyoD:Cre‐Lox approach and were subjected to treadmill testing and Western diet. C57/Bl6 mice were subjected to Western diet with or without pharmacological inhibition of NKA α1/Src modulation by treatment with pNaKtide, a cell‐permeable peptide designed by mapping one of the sites of NKA α1/Src interaction.\n\n\nResults\nMetabolic studies in mutant cell lines revealed that the Src binding regions of NKA α1 are required to maintain metabolic reserve and flexibility. Skα1−/− mice had decreased exercise endurance and mitochondrial Complex I dysfunction. However, skα1−/− mice were resistant to Western diet‐induced insulin resistance and glucose intolerance, a protection phenocopied by pharmacological inhibition of NKA α1‐mediated Src regulation with pNaKtide.\n\n\nConclusions\nThese results suggest that NKA α1/Src regulatory function may be targeted in metabolic diseases. Because Src regulatory capability by NKA α1 is exclusive to endotherms, it may link the aerobic scope hypothesis of endothermy evolution to metabolic dysfunction.\n\n"]

["Acta Physiologica, Volume 232, Issue 3, July 2021. ", "\nAbstract\n\nAims\nTotal haemoglobin mass (tot‐Hb) increases during high‐altitude acclimatization. Normalization of tot‐Hb upon descent is thought to occur via neocytolysis, the selective destruction of newly formed erythrocytes. Because convincing experimental proof of neocytolysis is lacking, we performed a prospective study on erythrocyte survival after a stay at the Jungfraujoch Research Station (JFJRS; 3450 m).\n\n\nMethods\nNewly formed erythrocytes of 12 male subjects (mean age 23.3 years) were age cohort labelled in normoxia (110 m) and during a 19‐day high‐altitude sojourn by ingestion of 13C2‐ and 15N‐labelled glycine respectively. Elimination dynamics for erythrocytes produced in normoxia and at high altitude were measured by isotope ratio mass spectrometry of haem, by determining tot‐Hb, reticulocyte counts, erythrocyte membrane protein 4.1a/4.1b ratio and by mathematical modelling.\n\n\nResults\nTot‐Hb increased by 4.7% ± 2.7% at high altitude and returned to pre‐altitude values within 11 days after descent. Elimination of 13C‐ (normoxia) and 15N‐ (high altitude) labelled erythrocytes was not different. Erythropoietin levels and counts of CD71‐positive reticulocytes decreased rapidly after descent. The band 4.1a/4.1b ratio decreased at altitude and remained low for 3‐4 days after descent and normalized slowly. There was no indication of haemolysis.\n\n\nConclusion\nWe confirm a rapid normalization of tot‐Hb upon descent. Based on the lack of accelerated removal of age cohorts of erythrocytes labelled at high altitude, on patterns of changes in reticulocyte counts and of the band 4.1a/4.1b ratio and on modelling, this decrease did not occur via neocytolysis, but by a reduced rate of erythropoiesis along with normal clearance of senescent erythrocytes.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nThe phosphorylation level of the furosemide‐sensitive Na+‐K+‐2Cl− cotransporter (NKCC2) in the thick ascending limb (TAL) is used as a surrogate marker for NKCC2 activation and TAL function. However, in mice, analyses of NKCC2 phosphorylation with antibodies against phosphorylated threonines 96 and 101 (anti‐pT96/pT101) give inconsistent results. We aimed (a) to elucidate these inconsistencies and (b) to develop a phosphoform‐specific antibody that ensures reliable detection of NKCC2 phosphorylation in mice.\n\n\nMethods\nGenetic information, molecular biology, biochemical techniques and mouse phenotyping was used to study NKCC2 and kidney function in two commonly used mouse strains (ie 129Sv and in C57BL/6 mice). Moreover, a new phosphoform‐specific mouse NKCC2 antibody was developed and characterized.\n\n\nResults\nAmino acids sequence alignment revealed that C57BL/6 mice have a strain‐specific five amino acids deletion (ΔF97‐T101) in NKCC2 that diminishes the detection of NKCC2 phosphorylation with previously developed pT96/pT101 NKCC2 antibodies. Instead, the antibodies cross‐react with the phosphorylated thiazide‐sensitive NaCl cotransporter (NCC), which can obscure interpretation of results. Interestingly, the deletion in NKCC2 does not impact on kidney function and/or expression of renal ion transport proteins as indicated by the analysis of the F2 generation of crossbred 129Sv and C57BL/6 mice. A newly developed pT96 NKCC2 antibody detects pNKCC2 in both mouse strains and shows no cross‐reactivity with phosphorylated NCC.\n\n\nConclusion\nOur work reveals a hitherto unappreciated, but essential, strain difference in the amino acids sequence of mouse NKCC2 that needs to be considered when analysing NKCC2 phosphorylation in mice. The new pNKCC2 antibody circumvents this technical caveat.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nChronodisruption desynchronizes peripheral clocks and leads to metabolic diseases. Feeding cues are important synchronizers of peripheral clocks and influence rhythmic oscillations in intestinal microbiota and their metabolites. We investigated whether chronic jetlag, mimicking frequent time zone travelling, affected the diurnal fluctuations in faecal short‐chain fatty acid (SCFA) levels, that feed back to the gut clock to regulate rhythmicity in gut function.\n\n\nMethods\nRhythms in faecal SCFAs levels and in the expression of clock genes and epithelial markers were measured in the colonic mucosa of control and jetlagged mice. The entraining effect of SCFAs on the rhythm in clock gene mRNA expression was studied in primary colonic crypts. The role of the circadian clock in epithelial marker expression was studied in Arntl−/− mice.\n\n\nResults\nChronic jetlag increased body weight gain and abolished the day/night food intake pattern which resulted in a phase‐delay in the rhythm of faecal SCFAs that paralleled the shift in the expression of mucosal clock genes. This effect was mimicked by stimulation of primary colonic crypts from control mice with SCFAs. Jetlag abolished the rhythm in Tnfα, proglucagon and ghrelin expression but not in the expression of tight junction markers. Only a dampening in plasma glucagon‐like peptide‐1 but not in ghrelin levels was observed. Rhythms in ghrelin but not proglucagon mRNA expression were abolished in Arntl−/− mice.\n\n\nConclusion\nThe altered food intake pattern during chronodisruption corresponds with the changes in rhythmicity of SCFA levels that entrain clock genes to affect rhythms in mRNA expression of gut epithelial markers.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nMechanosensitive Piezo1 ion channels emerged recently as important contributors to various vital functions including modulation of the blood supply to skeletal muscles. The specific Piezo1 channel agonist Yoda1 was shown to regulate the tone of blood vessels similarly to physical exercise. However, the direct role of Piezo1 channels in muscle function has been little studied so far. We therefore investigated the action of Yoda1 on the functional state of skeletal muscle precursors (satellite cells and myotubes) and on adult muscle fibres.\n\n\nMethods\nImmunostaining, electrophysiological intracellular recordings and Ca2+ imaging experiments were performed to localize and assess the effect of the chemical activation of Piezo1 channels with Yoda1, on myogenic precursors, adult myofibres and at the adult neuromuscular junction.\n\n\nResults\nPiezo1 channels were detected by immunostaining in satellite cells (SCs) and myotubes as well as in adult myofibres. In the skeletal muscle precursors, Yoda1 treatment stimulated the differentiation and cell fusion rather than the proliferation of SCs. Moreover, in myotubes, Yoda1 induced significant [Ca2+]i transients, without detectable [Ca2+]i response in adult myofibres. Furthermore, although expression of Piezo1 channels was detected around the muscle endplate region, Yoda1 application did not alter either the nerve‐evoked or spontaneous synaptic activity or muscle contractions in adult myofibres.\n\n\nConclusion\nOur data indicate that the chemical activation of Piezo1 channels specifically enhances the differentiation of skeletal muscle precursors, suggesting a possible new strategy to promote muscle regeneration.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nKidney diseases constitute a major health challenge, which requires noninvasive imaging to complement conventional approaches to diagnosis and monitoring. Several renal pathologies are associated with changes in kidney size, offering an opportunity for magnetic resonance imaging (MRI) biomarkers of disease. This work uses dynamic MRI and an automated bean‐shaped model (ABSM) for longitudinal quantification of pathophysiologically relevant changes in kidney size.\n\n\nMethods\nA geometry‐based ABSM was developed for kidney size measurements in rats using parametric MRI (T2, T2* mapping). The ABSM approach was applied to longitudinal renal size quantification using occlusion of the (a) suprarenal aorta or (b) the renal vein, (c) increase in renal pelvis and intratubular pressure and (d) injection of an X‐ray contrast medium into the thoracic aorta to induce pathophysiologically relevant changes in kidney size.\n\n\nResults\nThe ABSM yielded renal size measurements with accuracy and precision equivalent to the manual segmentation, with >70‐fold time savings. The automated method could detect a ~7% reduction (aortic occlusion) and a ~5%, a ~2% and a ~6% increase in kidney size (venous occlusion, pelvis and intratubular pressure increase and injection of X‐ray contrast medium, respectively). These measurements were not affected by reduced image quality following administration of ferumoxytol.\n\n\nConclusion\nDynamic MRI in conjunction with renal segmentation using an ABSM supports longitudinal quantification of changes in kidney size in pathophysiologically relevant experimental setups mimicking realistic clinical scenarios. This can potentially be instrumental for developing MRI‐based diagnostic tools for various kidney disorders and for gaining new insight into mechanisms of renal pathophysiology.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nDisruption of the intestinal mucosal tolerance, that is, the immunological unresponsiveness to innocuous food antigens and the commensal microbiota, in the colon is associated with several chronic diseases including inflammatory bowel disease (IBD). Understanding the mechanisms responsible for intestinal mucosal tolerance has potential translational value for its therapy and management. Human intestinal mesenchymal cells (iMCs) play important roles in colonic mucosal tolerance, but further studies on their tissue regenerative and immunomodulatory capacities are necessary in order to fully understand their function in health and disease.\n\n\nMethods\nIn this study, we have isolated and analysed the capacity of human iMCs to promote wound healing and modulate immune responses in vitro and in vivo, using the dextran sulfate sodium (DSS)‐induced colitis model.\n\n\nResults\nCultured iMCs were CD45−CD73+CD90+CD105+ and accelerated the wound closure in a normal colon mucosa (NCM) 356 human epithelial cell wound healing assay. Furthermore, iMCs blocked the LPS‐mediated induction of TNF‐α in THP‐1 macrophages and inhibited the proliferation of peripheral blood mononuclear cells, partly through the induction of indoleamine‐2,3‐dioxygenase. In DSS colitic mice, iMCs administration reduced the disease activity index and ameliorated intestinal tissue damage and permeability. Furthermore, iMCs reduced intestinal inflammation, evidenced by a decreased mRNA expression of pro‐inflammatory cytokines, reduced IL‐1β secretion by intestinal explants and inhibited colonic iNOS protein expression.\n\n\nConclusions\nOur data show that human iMCs isolated from the noninflamed intestine possess tissue‐regenerative and immunomodulatory capacities that could potentially be harnessed/restored in order to reduce IBD severity.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nThe optimal exercise intensity to improve endothelial function remains unclear, as well as whether the addition of hypoxia could potentiate this function. Therefore, the aim of this study was to compare the effects of different exercise intensities in normoxia and hypoxia on vascular reactivity and nitric oxide (NO) bioavailability in mice.\n\n\nMethods\nC57BL/6 mice underwent treadmill running three times per week, for 4 weeks at either low, maximal or supramaximal intensity in normoxia or hypoxia (inspire oxygen fraction = 0.13). Vascular reactivity and expression of genes and proteins involved in NO production/bioavailability were assessed in aorta using isolated vessel tension experiments, RT‐qPCR and western blot, respectively. Circulating NO metabolites and pro‐/antioxidant markers were measured.\n\n\nResults\nHypoxic exercise improved both acetylcholine‐induced vasorelaxation and phenylephrine‐induced vasoconstriction compared to normoxic exercise, independently of intensity. In hypoxia, a higher acetylcholine‐induced vasorelaxation was observed with high intensities (supramaximal and maximal) compared to low intensity. Exercise protocols modulated endothelial nitric oxide synthase (eNOS) and α1‐adrenergic receptor (α1‐AR) mRNA level, but not superoxide dismutase 3 (SOD3) and p47phox. No significant differences were observed for protein expression of α1‐AR, total eNOS, phosphorylated eNOS, SOD isoforms and p47phox. However, plasma SOD and catalase activities were significantly increased in hypoxic supramaximal compared to hypoxic low intensity, while concentration of nitrotyrosine significantly decreased. The latter was also observed in hypoxic maximal and supramaximal compared to the same intensities in normoxia.\n\n\nConclusion\nHypoxic high‐intensity exercise increases NO bioavailability and improves vascular function, opening promising clinical perspectives for cardiovascular disease prevention.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\nO‐GlcNAcylation is a ubiquitous post‐translational modification that is extremely labile and plays a significant role in physiology, including the heart. Sustained activation of cardiac O‐GlcNAcylation is frequently associated with alterations in cellular metabolism, leading to detrimental effects on cardiovascular function. This is particularly true during conditions such as diabetes, hypertension, cardiac remodelling, heart failure and arrhythmogenesis. Paradoxically, transient elevation of cardiac protein O‐GlcNAcylation can also exert beneficial effects in the heart. There is compelling evidence to suggest that a complex interaction between O‐GlcNAcylation and phosphorylation also exists in the heart. Beyond direct functional consequences on cardiomyocytes, O‐GlcNAcylation also acts indirectly by altering the function of transcription factors that affect downstream signalling. This review focuses on the potential cardioprotective role of protein O‐GlcNAcylation during ischaemia‐reperfusion injury, the deleterious consequences of chronically elevated O‐GlcNAc levels, the interplay between O‐GlcNAcylation and phosphorylation in the cardiomyocytes and the effects of O‐GlcNAcylation on other major non‐myocyte cell types in the heart.\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nAbsorption of ammonia from the gut has consequences that range from encephalitis in hepatic disease to global climate change induced by nitrogenous excretions from livestock. Since patch clamp data show that certain members of the transient receptor potential (TRP) family are permeable to NH4+, participation in ammonium efflux was investigated.\n\n\nMethods\nDigesta, mucosa and muscular samples from stomach, duodenum, jejunum, ileum, caecum and colon of pigs were analysed via colourimetry, qPCR, Western blot, immunohistochemistry and Ussing chambers.\n\n\nResults\nqPCR data show high duodenal expression of TRPV6. TRPM6 was highest in jejunum and colon, with expression of TRPM7 ubiquitous. TRPM8 and TRPV1 were below detection. TRPV2 was highest in the jejunum but almost non‐detectable in the colon. TRPV4 was ubiquitously expressed by mucosal and muscular layers. TRPV3 mRNA was only found in the mucosa of the caecum and colon, organs in which NH4+ was highest (>7 mmol·L−1). Immunohistochemically, an apical expression of TRPV3 and TRPV4 could be detected in all tissues, with effects of 2‐APB and GSK106790A supporting functional expression. In symmetrical NaCl Ringer, removal of mucosal Ca2+ and Mg2+ increased colonic short circuit current (Isc) and conductance (Gt) by 0.18 ± 0.06 µeq·cm−2·h−1 and 4.70 ± 0.85 mS·cm−2 (P < .05, N/n = 4/17). Application of mucosal NH4Cl led to dose‐dependent and divalent‐sensitive increases in Gt and Isc, with effects highest in the caecum and colon.\n\n\nConclusion\nWe propose that TRP channels contribute to the intestinal transport of ammonium, with TRPV3 and TRPV4 promising candidate proteins. Pharmacological regulation may be possible.\n\n"]

["Acta Physiologica, Volume 232, Issue 2, June 2021. ", "\nAbstract\n\nAim\nPatients suffering from acute lung injury (ALI) are at high risk of developing cardiac arrhythmias. We hypothesized that stellate ganglia (SG) neural inflammation contributes to ALI‐induced arrhythmia.\n\n\nMethods\nWe created an ALI rat model using a single tracheal instillation of bleomycin (2.5 mg/kg), with saline as a sham control. We recorded ECGs by implanted radiotelemetry in male bleomycin and sham rats treated with and without oral minocycline (20 mg/kg/d), an anti‐inflammatory drug that inhibits microglia/macrophage activation. The SG neuronal excitability was assessed by electrophysiology experiments.\n\n\nResults\nECG data showed that bleomycin‐exposed rats exhibited significantly more spontaneous premature ventricular contractions (PVCs) from 1‐ to 3‐week post‐induction compared with sham rats, which was mitigated by chronic oral administration of minocycline. The bleomycin‐exposed rats displayed a robust increase in both the number of Iba1‐positive macrophages and protein expression of interferon regulatory factor 8 in the SG starting as early at 1‐week post‐exposure and lasted for at least 4 weeks, which was largely attenuated by minocycline. Heart rate variability analysis indicated autonomic imbalance during the first 2‐week post‐bleomycin, which was significantly attenuated by minocycline. Electrical stimulation of the decentralized SG triggered more PVCs in bleomycin‐exposed rats than sham and bleomycin + minocycline rats. Patch‐clamp data demonstrated enhanced SG neuronal excitability in the bleomycin‐exposed rats, which was attenuated by minocycline. Co‐culture of lipopolysaccharide (LPS)‐pretreated macrophages with normal SG neurons enhanced SG neuronal excitability.\n\n\nConclusion\nMacrophage activation in the SG contributes to arrhythmogenesis in bleomycin‐induced ALI in male rats.\n\n"]

["Acta Physiologica, Volume 232, Issue 2, June 2021. ", "\nAbstract\n\nAim\nA “leaky” gut barrier has been implicated in the initiation and progression of a multitude of diseases, for example, inflammatory bowel disease (IBD), irritable bowel syndrome and celiac disease. Here we show how pro‐hormone Chromogranin A (CgA), produced by the enteroendocrine cells, and Catestatin (CST: hCgA352‐372), the most abundant CgA‐derived proteolytic peptide, affect the gut barrier.\n\n\nMethods\nColon tissues from region‐specific CST‐knockout (CST‐KO) mice, CgA‐knockout (CgA‐KO) and WT mice were analysed by immunohistochemistry, western blot, ultrastructural and flowcytometry studies. FITC‐dextran assays were used to measure intestinal barrier function. Mice were supplemented with CST or CgA fragment pancreastatin (PST: CgA250‐301). The microbial composition of cecum was determined. CgA and CST levels were measured in blood of IBD patients.\n\n\nResults\nPlasma levels of CST were elevated in IBD patients. CST‐KO mice displayed (a) elongated tight, adherens junctions and desmosomes similar to IBD patients, (b) elevated expression of Claudin 2, and (c) gut inflammation. Plasma FITC‐dextran measurements showed increased intestinal paracellular permeability in the CST‐KO mice. This correlated with a higher ratio of Firmicutes to Bacteroidetes, a dysbiotic pattern commonly encountered in various diseases. Supplementation of CST‐KO mice with recombinant CST restored paracellular permeability and reversed inflammation, whereas CgA‐KO mice supplementation with CST and/or PST in CgA‐KO mice showed that intestinal paracellular permeability is regulated by the antagonistic roles of these two peptides: CST reduces and PST increases permeability.\n\n\nConclusion\nThe pro‐hormone CgA regulates the intestinal paracellular permeability. CST is both necessary and sufficient to reduce permeability and primarily acts by antagonizing PST.\n\n"]

["Acta Physiologica, Volume 232, Issue 2, June 2021. ", "\nAbstract\n\nAims\nRecent reports suggest that iron deficiency impacts both intestinal calcium and phosphate absorption, although the exact transport pathways and intestinal segment responsible have not been determined. Therefore, we aimed to systematically investigate the impact of iron deficiency on the cellular mechanisms of transcellular and paracellular calcium and phosphate transport in different regions of the rat small intestine.\n\n\nMethods\nAdult, male Sprague‐Dawley rats were maintained on a control or iron‐deficient diet for 2 weeks and changes in intestinal calcium and phosphate uptake were determined using the in situ intestinal loop technique. The circulating levels of the hormonal regulators of calcium and phosphate were determined by ELISA, while the expression of transcellular calcium and phosphate transporters, and intestinal claudins were determined using qPCR and western blotting.\n\n\nResults\nDiet‐induced iron deficiency significantly increased calcium absorption in the duodenum but had no impact in the jejunum and ileum. In contrast, phosphate absorption was significantly inhibited in the duodenum and to a lesser extent the jejunum, but remained unchanged in the ileum. The changes in duodenal calcium and phosphate absorption in the iron‐deficient animals were associated with increased claudin 2 and 3 mRNA and protein levels, while levels of parathyroid hormone, fibroblast growth factor‐23 and 1,25‐dihydroxy vitamin D3 were unchanged.\n\n\nConclusion\nWe propose that iron deficiency alters calcium and phosphate transport in the duodenum. This occurs via changes to the paracellular pathway, whereby upregulation of claudin 2 increases calcium absorption and upregulation of claudin 3 inhibits phosphate absorption.\n\n"]

["Acta Physiologica, Volume 232, Issue 2, June 2021. ", "\nAbstract\n\nAim\nWe examined if tonic γ‐aminobutyric acid (GABA)‐activated currents in primary hippocampal neurons were modulated by insulin in wild‐type and tg‐APPSwe mice, an Alzheimer's disease (AD) model.\n\n\nMethods\nGABA‐activated currents were recorded in dentate gyrus (DG) granule cells and CA3 pyramidal neurons in hippocampal brain slices, from 8 to 10 weeks old (young) wild‐type mice and in dorsal DG granule cells in adult, 5‐6 and 10‐12 (aged) months old wild‐type and tg‐APPSwe mice, in the absence or presence of insulin, by whole‐cell patch‐clamp electrophysiology.\n\n\nResults\nIn young mice, insulin (1 nmol/L) enhanced the total spontaneous inhibitory postsynaptic current (sIPSCT) density in both dorsal and ventral DG granule cells. The extrasynaptic current density was only increased by insulin in dorsal CA3 pyramidal neurons. In absence of action potentials, insulin enhanced DG granule cells and dorsal CA3 pyramidal neurons miniature IPSC (mIPSC) frequency, consistent with insulin regulation of presynaptic GABA release. sIPSCT densities in DG granule cells were similar in wild‐type and tg‐APPSwe mice at 5‐6 months but significantly decreased in aged tg‐APPSwe mice where insulin normalized currents to wild‐type levels. The extrasynaptic current density was increased in tg‐APPSwe mice relative to wild‐type littermates but, only in aged tg‐APPSwe mice did insulin decrease and normalize the current.\n\n\nConclusion\nInsulin effects on GABA signalling in hippocampal neurons are selective while multifaceted and context‐based. Not only is the response to insulin related to cell‐type, hippocampal axis‐location, age of animals and disease but also to the subtype of neuronal inhibition involved, synaptic or extrasynaptic GABAA receptors‐activated currents.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\n\nAim\nThe skeletal muscle Cl− channels, the ClC‐1 channels, stabilize the resting membrane potential and dampen muscle fibre excitability. This study explored whether ClC‐1 inhibition can recover nerve‐stimulated force in isolated muscle under conditions of compromised neuromuscular transmission akin to disorders of myasthenia gravis and Lambert–Eaton syndrome.\n\n\nMethods\nNerve‐muscle preparations were isolated from rats. Preparations were exposed to pre‐or post‐synaptic inhibitors (ω‐agatoxin, elevated extracellular Mg2+, α‐bungarotoxin or tubocurarine). The potential of ClC‐1 inhibition (9‐AC or reduced extracellular Cl−) to recover nerve‐stimulated force under these conditions was assessed.\n\n\nResults\nClC‐1 inhibition recovered force in both slow‐twitch soleus and fast‐twitch EDL muscles exposed to 0.2 µmol/L tubocurarine or 3.5 mmol/L Mg2+. Similarly, ClC‐1 inhibition recovered force in soleus muscles exposed to α‐bungarotoxin or ω‐agatoxin. Moreover, the concentrations of tubocurarine and Mg2+ required for reducing force to 50% rose from 0.14 ± 0.02 µmol/L and 4.2 ± 0.2 mmol/L in control muscles to 0.45 ± 0.03 µmol/L and 4.7 ± 0.3 mmol/L in muscles with 9‐AC respectively (P < .05, paired T test). Inhibition of acetylcholinesterase (neostigmine) and inhibition of voltage‐gated K+ channels (4‐AP) relieve symptoms in myasthenia gravis and Lambert–Eaton syndrome, respectively. Neostigmine and 9‐AC additively increased the tubocurarine concentration required to reduce nerve‐stimulated force to 50% (0.56 ± 0.05 µmol/L with 9‐AC and neostigmine) and, similarly, 4‐AP and 9‐AC additively increased the Mg2+ concentration required to reduce nerve‐stimulated force to 50% (6.5 ± 0.2 mmol/L with 9‐AC and 4‐AP).\n\n\nConclusion\nThis study shows that ClC‐1 inhibition can improve neuromuscular function in pharmacological models of compromised neuromuscular transmission.\n\n"]

["Acta Physiologica, EarlyView. ", "\nAbstract\nDevelopment of the Central Nervous System (CNS) is reliant on the proper function of numerous intricately orchestrated mechanisms that mature independently, including constant communication between the CNS and the peripheral immune system. This review summarizes experimental knowledge of how cerebral ischaemia in infants and children alters physiological communication between leucocytes, brain immune cells, microglia and the neurovascular unit (NVU)—the “microglia‐leucocyte axis”—and contributes to acute and long‐term brain injury. We outline physiological development of CNS barriers in relation to microglial and leucocyte maturation and the plethora of mechanisms by which microglia and peripheral leucocytes communicate during postnatal period, including receptor‐mediated and intracellular inflammatory signalling, lipids, soluble factors and extracellular vesicles. We focus on the “microglia‐leucocyte axis” in rodent models of most common ischaemic brain diseases in the at‐term infants, hypoxic‐ischaemic encephalopathy (HIE) and focal arterial stroke and discuss commonalities and distinctions of immune‐neurovascular mechanisms in neonatal and childhood stroke compared to stroke in adults. Given that hypoxic and ischaemic brain damage involve Toll‐like receptor (TLR) activation, we discuss the modulatory role of viral and bacterial TLR2/3/4‐mediated infection in HIE, perinatal and childhood stroke. Furthermore, we provide perspective of the dynamics and contribution of the axis in cerebral ischaemia depending on the CNS maturational stage at the time of insult, and modulation independently and in consort by individual axis components and in a sex dependent ways. Improved understanding on how to modify crosstalk between microglia and leucocytes will aid in developing age‐appropriate therapies for infants and children who suffered cerebral ischaemia.\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\nHumans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene‐related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\nThe molecular mechanisms underlying chronic kidney disease (CKD) are poorly understood and treatment options are limited, a situation underpinning the need for elucidating the causative molecular mechanisms and for identifying innovative treatment options. It is emerging that cyclic 3′,5′‐adenosine monophosphate (cAMP) signalling occurs in defined cellular compartments within nanometre dimensions in processes whose dysregulation is associated with CKD. cAMP compartmentalization is tightly controlled by a specific set of proteins, including A‐kinase anchoring proteins (AKAPs) and phosphodiesterases (PDEs). AKAPs such as AKAP18, AKAP220, AKAP‐Lbc and STUB1, and PDE4 coordinate arginine‐vasopressin (AVP)‐induced water reabsorption by collecting duct principal cells. However, hyperactivation of the AVP system is associated with kidney damage and CKD. Podocyte injury involves aberrant AKAP signalling. cAMP signalling in immune cells can be local and slow the progression of inflammatory processes typical for CKD. A major risk factor of CKD is hypertension. cAMP directs the release of the blood pressure regulator, renin, from juxtaglomerular cells, and plays a role in Na+ reabsorption through ENaC, NKCC2 and NCC in the kidney. Mutations in the cAMP hydrolysing PDE3A that cause lowering of cAMP lead to hypertension. Another major risk factor of CKD is diabetes mellitus. AKAP18 and AKAP150 and several PDEs are involved in insulin release. Despite the increasing amount of data, an understanding of functions of compartmentalized cAMP signalling with relevance for CKD is fragmentary. Uncovering functions will improve the understanding of physiological processes and identification of disease‐relevant aberrations may guide towards new therapeutic concepts for the treatment of CKD.\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\nMyocardial infarction (MI) occurs when coronary blood flow is decreased due to an obstruction/occlusion of the vessels, leading to myocardial death and progression to heart failure (HF). Cognitive impairment, anxiety, depression and memory loss are the most frequent mental health problems among patients with HF. The most common cause of cognitive decline is cardiac systolic dysfunction, which leads to reduced cerebral perfusion. Several in vivo and clinical studies provide information regarding the underlying mechanisms of HF in brain pathology. Neurohormonal activation, oxidative stress, inflammation, glial activation, dendritic spine loss and brain programmed cell death are all proposed as contributors of cognitive impairment in HF. Furthermore, several investigations into the effects of various medications on brain pathology utilizing MI models have been reported. In this review, potential mechanisms involving HF‐associated cognitive impairment, as well as neuroprotective interventions in HF models, are discussed and summarized. In addition, gaps in the surrounding knowledge, including the types of brain cell death and the effects of cell death inhibitors in HF, are presented and discussed. This review provides valuable information that will suggest the potential therapeutic strategies for cognitive impairment in patients with HF.\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nThe serine protease prostasin (Prss8) is expressed in the distal tubule and stimulates proteolytic activation of the epithelial sodium channel (ENaC) in co‐expression experiments in vitro. The aim of this study was to explore the role of prostasin in proteolytic ENaC activation in the kidney in vivo.\n\n\nMethods\nWe used genetically modified knockin mice carrying a Prss8 mutation abolishing proteolytic activity (Prss8‐S238A) or a mutation leading to a zymogen‐locked state (Prss8‐R44Q). Mice were challenged with low sodium diet and diuretics. Regulation of ENaC activity by Prss8‐S238A and Prss8‐R44Q was studied in vitro using the Xenopus laevis oocyte expression system.\n\n\nResults\nCo‐expression of murine ENaC with Prss8‐wt or Prss8‐S238A in oocytes caused maximal proteolytic ENaC activation, whereas ENaC was activated only partially in oocytes co‐expressing Prss8‐R44Q. This was paralleled by a reduced proteolytic activity at the cell surface of Prss8‐R44Q expressing oocytes. Sodium conservation under low sodium diet was preserved in Prss8‐S238A and Prss8‐R44Q mice but with higher plasma aldosterone concentrations in Prss8‐R44Q mice. Treatment with the ENaC inhibitor triamterene over four days was tolerated in Prss8‐wt and Prss8‐S238A mice, whereas Prss8‐R44Q mice developed salt wasting and severe weight loss associated with hyperkalemia and acidosis consistent with impaired ENaC function and renal failure.\n\n\nConclusion\nUnlike proteolytically inactive Prss8‐S238A, zymogen‐locked Prss8‐R44Q produces incomplete proteolytic ENaC activation in vitro and causes a severe renal phenotype in mice treated with the ENaC inhibitor triamterene. This indicates that Prss8 plays a role in proteolytic ENaC activation and renal function independent of its proteolytic activity.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nThe inorganic anions nitrate and nitrite are oxidation products of nitric oxide (NO) that have often been used as an index of NO generation. More than just being surrogate markers of NO, nitrate/nitrite can recycle to bioactive NO again. Nitrate is predominantly eliminated via the kidneys; however, there is less knowledge regarding tubular handling. The aim of this study, as part of a large randomized controlled trial, was to explore potential sex differences in renal nitrate handling during low and high dietary nitrate intake. We hypothesized that renal clearance and excretion of nitrate are higher in men compared to women.\n\n\nMethods\nIn prehypertensive and hypertensive individuals (n = 231), nitrate and nitrite were measured in plasma and urine at low dietary nitrate intake (baseline) and after 5 weeks supplementation with nitrate (300 mg potassium nitrate/day) or placebo (300 mg potassium chloride/day). Twenty‐four hours ambulatory blood pressure recordings and urine collections were conducted.\n\n\nResults\nAt baseline, plasma nitrate and nitrite, as well as the downstream marker of NO signalling cyclic guanosine monophosphate, were similar in women and men. Approximately 80% of filtered nitrate was spared by the kidneys. Urinary nitrate concentration, amount of nitrate excreted, renal nitrate clearance (Cnitrate) and fractional excretion of nitrate (FEnitrate) were lower in women compared to men. No association was observed between plasma nitrate concentrations and glomerular filtration rate (GFR), nor between FEnitrate and GFR in either sex. After 5 weeks of nitrate supplementation plasma nitrate and nitrite increased significantly, but blood pressure remained unchanged. FEnitrate increased significantly and the sex difference observed at baseline disappeared.\n\n\nConclusion\nOur findings demonstrate substantial nitrate sparing capacity of the kidneys, which is higher in women compared to men. This suggests higher tubular nitrate reabsorption in women but the underlying mechanism(s) warrants further investigation.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAims\nDiabetic nephropathy (DN) is a leading cause of end‐stage renal disease. BASP1 (brain acid‐soluble protein) is up‐regulated in podocyte‐specific protein phosphatase 2A knockout mice (Pod‐PP2A‐KO) that develop kidney dysfunction. Here, we explore the role of BASP1 for podocytes in DN.\n\n\nMethods\nBASP1 was assessed in kidneys from DN patients and DN mouse models, podocyte specific BASP1 knockout mice (Pod‐BASP1‐KO mice) were generated and studied in vivo. Furthermore, podocyte injury and apoptosis were measured after BASP1 knockdown and overexpression in a mouse podocyte cell line (MPC5). Potential signalling pathways involved in podocyte apoptosis were detected.\n\n\nResults\nBASP1 expression was up‐regulated in DN patients compared to normal controls. BASP1 specific deletion in podocytes protected against podocyte injury by reducing the loss of expression of slit diaphragm molecules and foot process effacement in the DN model. BASP1 promoted actin cytoskeleton rearrangements and apoptosis in the MPC5 podocyte line. Molecules involved in the p53 pathway were down‐regulated in BASP1 knockdown podocytes treated with high glucose compared to controls. BASP1 promoted podocyte apoptosis and P53 pathway activation through co‐repression with Wilms' tumour 1 transcription factor (WT1).\n\n\nConclusion\nBASP1 activates the p53 pathway through modulation of WT1 to induce podocyte apoptosis in diabetic nephropathy.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nWe have reported earlier that a high salt intake triggered an aestivation‐like natriuretic‐ureotelic body water conservation response that lowered muscle mass and increased blood pressure. Here, we tested the hypothesis that a similar adaptive water conservation response occurs in experimental chronic renal failure.\n\n\nMethods\nIn four subsequent experiments in Sprague Dawley rats, we used surgical 5/6 renal mass reduction (5/6 Nx) to induce chronic renal failure. We studied solute and water excretion in 24‐hour metabolic cage experiments, chronic blood pressure by radiotelemetry, chronic metabolic adjustment in liver and skeletal muscle by metabolomics and selected enzyme activity measurements, body Na+, K+ and water by dry ashing, and acute transepidermal water loss in conjunction with skin blood flow and intra‐arterial blood pressure.\n\n\nResults\n5/6 Nx rats were polyuric, because their kidneys could not sufficiently concentrate the urine. Physiological adaptation to this renal water loss included mobilization of nitrogen and energy from muscle for organic osmolyte production, elevated norepinephrine and copeptin levels with reduced skin blood flow, which by means of compensation reduced their transepidermal water loss. This complex physiologic‐metabolic adjustment across multiple organs allowed the rats to stabilize their body water content despite persisting renal water loss, albeit at the expense of hypertension and catabolic mobilization of muscle protein.\n\n\nConclusion\nPhysiological adaptation to body water loss, termed aestivation, is an evolutionary conserved survival strategy and an under‐studied research area in medical physiology, which besides hypertension and muscle mass loss in chronic renal failure may explain many otherwise unexplainable phenomena in medicine.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nRecent evidence suggests that arterial hypertension could be alternatively explained as a physiological adaptation response to water shortage, termed aestivation, which relies on complex multi‐organ metabolic adjustments to prevent dehydration. Here, we tested the hypothesis that chronic water loss across diseased skin leads to similar adaptive water conservation responses as observed in experimental renal failure or high salt diet.\n\n\nMethods\nWe studied mice with keratinocyte‐specific overexpression of IL‐17A which develop severe psoriasis‐like skin disease. We measured transepidermal water loss and solute and water excretion in the urine. We quantified glomerular filtration rate (GFR) by intravital microscopy, and energy and nitrogen pathways by metabolomics. We measured skin blood flow and transepidermal water loss (TEWL) in conjunction with renal resistive indices and arterial blood pressure.\n\n\nResults\nPsoriatic animals lost large amounts of water across their defective cutaneous epithelial barrier. Metabolic adaptive water conservation included mobilization of nitrogen and energy from muscle to increase organic osmolyte production, solute‐driven maximal anti‐diuresis at normal GFR, increased metanephrine and angiotensin 2 levels, and cutaneous vasoconstriction to limit TEWL. Heat exposure led to cutaneous vasodilation and blood pressure normalization without parallel changes in renal resistive index, albeit at the expense of further increased TEWL.\n\n\nConclusion\nSevere cutaneous water loss predisposes psoriatic mice to lethal dehydration. In response to this dehydration stress, the mice activate aestivation‐like water conservation motifs to maintain their body hydration status. The circulatory water conservation response explains their arterial hypertension. The nitrogen‐dependency of the metabolic water conservation response explains their catabolic muscle wasting.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAims\nAdult hippocampal neurogenesis plays an important role in neuronal plasticity and maintenance in mammals. Low‐threshold voltage‐gated T‐type calcium channels produce calcium spikes that increase fast action potentials in newborn cells in the hippocampal dentate gyrus (DG); however, their role in adult hippocampal neurogenesis remains unclear. Here, we demonstrate impaired adult hippocampal neurogenesis in Cav3.1T‐type calcium channel knockout mice.\n\n\nMethods and Results\nCav3.1T‐type calcium channel was predominantly localized in neuronal progenitor cells of the mouse hippocampal DG. By counting the number of 5‐bromo‐2′‐deoxyuridine‐labeled cells, decreased proliferation and survival of newly generated cells were observed in the adult hippocampal DG in Cav3.1 knockout mice as compared to wild‐type (WT) mice. Moreover, the degree of maturation of doublecortin‐positive cells in Cav3.1 knockout mice was lower than that in WT mice, suggesting that Cav3.1 deletion may impair neuronal differentiation. Consistent with impaired hippocampal neurogenesis, Cav3.1 knockout mice showed decreased social interaction. Reduced phosphorylation levels of calcium/calmodulin‐dependent protein kinase II and protein kinase B were closely associated with impaired hippocampal neurogenesis in Cav3.1 knockout mice. Moreover, the mRNA and protein expression levels of brain‐derived neurotrophic factor, important for neurogenesis, were significantly decreased in Cav3.1 knockout mice. Finally, gene ontology analysis revealed alterations in genes related to the promotion of cell death/apoptosis and suppression of cell proliferation/neuronal differentiation pathways, including Bdnf.\n\n\nConclusion\nThese results suggest that the Cav3.1T‐type calcium channel may be a key molecule required for cell proliferation, survival and neuronal differentiation in newly generated cells of the adult mouse hippocampus.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nThe use of calcineurin inhibitors such as cyclosporine A (CsA) for immunosuppression after solid organ transplantation is commonly limited by renal side effects. CsA‐induced deterioration of glomerular filtration rate and sodium retention may be related to juxtaglomerular dysregulation as a result of suppressed cyclooxygenase 2 (COX‐2) and stimulated renin biosynthesis. We tested whether CsA‐induced COX‐2 suppression is caused by hyperactive renin‐angiotensin system (RAS) and whether RAS inhibition may alleviate the related side effects.\n\n\nMethods\nRats received CsA, the RAS inhibitor candesartan, or the COX‐2 inhibitor celecoxib acutely (3 days) or chronically (3 weeks). Molecular pathways mediating effects of CsA and RAS on COX‐2 were studied in cultured macula densa cells.\n\n\nResults\nPharmacological or siRNA‐mediated calcineurin inhibition in cultured cells enhanced COX‐2 expression via p38 mitogen‐activated protein kinase and NF‐kB signalling, whereas angiotensin II abolished these effects. Acute and chronic CsA administration to rats led to RAS activation along with reduced cortical COX‐2 expression, creatinine clearance and fractional sodium excretion. Evaluation of major distal salt transporters, NKCC2 and NCC, showed increased levels of their activating phosphorylation upon CsA. Concomitant candesartan treatment blunted these effects acutely and completely normalized the COX‐2 expression and renal functional parameters at long term. Celecoxib prevented the candesartan‐induced improvements of creatinine clearance and sodium excretion.\n\n\nConclusion\nSuppression of juxtaglomerular COX‐2 upon CsA results from RAS activation, which overrides the cell‐autonomous, COX‐2‐stimulatory effects of calcineurin inhibition. Angiotensin II antagonism alleviates CsA nephrotoxicity via the COX‐2‐dependent normalization of creatinine clearance and sodium excretion.\n\n"]

["Acta Physiologica, Volume 232, Issue 1, May 2021. ", "\nAbstract\n\nAim\nThe worldwide increase in obesity and type 2 diabetes (T2D) represents a major health challenge. Chronically altered lipids induced by obesity further promote the development of T2D, and the accumulation of toxic lipid metabolites in serum and peripheral organs may contribute to the diabetic phenotype.\n\n\nMethods\nTo better understand the complex metabolic pattern of lean and obese T2D and non‐T2D individuals, we analysed the lipid profile of human serum, skeletal muscle and visceral adipose tissue of two cohorts by systematic mass spectrometry‐based lipid analysis.\n\n\nResults\nLipid homeostasis was strongly altered in a disease‐ and tissue‐specific manner, allowing us to define T2D signatures associated with obesity from those that were obesity independent. Lipid changes encompassed lyso‐, diacyl‐ and ether‐phospholipids. Moreover, strong changes in sphingolipids included cytotoxic 1‐deoxyceramide accumulation in a disease‐specific manner in serum and visceral adipose tissue. The high amounts of non‐canonical 1‐deoxyceramide present in human adipose tissue most likely come from cell‐autonomous synthesis because 1‐deoxyceramide production increased upon differentiation to adipocytes in mouse cell culture experiments.\n\n\nConclusion\nTaken together, the observed lipidome changes in obesity and T2D will facilitate the identification of T2D patient subgroups and represent an important step towards personalized medicine in diabetes.\n\n"]