To determine the expression and clinical significance of plasma miR-335 in patients with acute ischemic stroke (AIS) and investigate its association with calmodulin (CaM) expression.

Plasma miR-335 and CaM expression levels in patients with AIS and healthy controls were examined. Correlations between miR-335, CaM, and National Institutes of Health Stroke Scale scores were also analysed. Furthermore, the potential regulatory function of miR-335 on CaM expression was investigated.

Plasma miR-335 levels were significantly lower in AIS and negatively correlated with NIHSS scores. The converse was observed for plasma CaM levels. Plasma miR-335 and CaM levels were negatively correlated. Plasma miR-335 was confirmed as a novel biomarker for AIS diagnosis and an independent predictor of AIS. Up-regulation of miR-335 suppressed CaM protein expression, and CaM was confirmed as a direct target of miR-335.

Plasma miR-335 was down-regulated in AIS patients and represents a potential noninvasive circulating biomarker.