miR-335 promotes stress granule formation to inhibit apoptosis by targeting ROCK2 in acute ischemic stroke

Under harmful environmental conditions, stress granules (SGs), macromolecular aggregates that are associated with cell survival and death, are produced in the eukaryotic cytoplasm. However, whether and how microRNAs (miRNAs/miRs) modulate SG formation induced by acute ischemic stroke has not been investigated. In the present study, a rat model of middle cerebral artery occlusion (MCAO) was utilized and miRNA array profiling and reverse transcription-quantitative polymerase chain reaction were performed. The results revealed that miR-335 was downregulated during acute ischemic stroke, which was concomitant with reduced SG formation, enhanced apoptosis levels and increased Rho associated protein kinase 2 (ROCK2) expression. In the MCAO rat and serum-free cell models, miR-335 treatment upregulated SG formation, alleviated the ischemia-induced infarction, and decreased ROCK2 protein expression and apoptosis levels. By contrast, when compared with miR-335 treatment, the inhibition of miR-335 resulted in reduced SG formation and higher ROCK2 expression and apoptosis levels. Target prediction analysis and luciferase 3-untranslated region reporter assay identified ROCK2 as the direct target of miR-335. Furthermore, ROCK2 silencing enhanced SG formation and attenuated the level of apoptosis in the serum-free cell model. In addition, ROCK2 silencing markedly inhibited the effect of miR-335 on SG formation and apoptosis levels. Unexpectedly, the phosphorylation of T-cell intracellular antigen-1 was significantly inhibited by miR-335 in the MCAO rat model, which provides a reasonable explanation for the promotional effect of miR-335 on SG formation by specifically targeting ROCK2. In conclusion, these results demonstrate that miR-335 promotes SG formation and inhibits apoptosis by reducing ROCK2 expression in acute ischemic stroke, which provides a possible therapeutic target for brain injury.