MiR-199a modulates autophagy and inflammation in rats with cerebral infarction via regulating mTOR expression

OBJECTIVE

The aim of this study was to investigate the roles of micro ribonucleic acid (miR)-199a in rats with cerebral infarction by regulating mammalian target of rapamycin (mTOR).

MATERIALS AND METHODS

A total of 36 Sprague-Dawley rats were randomly assigned into three groups, including: sham group (n=12), model group (n=12) and miR-199a mimics group (n=12). In sham group internal and external carotid arteries were exposed. The ischemia-reperfusion model was successfully established using suture embolization in the other two groups. After modeling, rats in sham group and model group were intraperitoneally injected with normal saline. However, rats in miR-199a mimics group were injected with miR-199a mimics. Following intervention for 3 d, sampling was conducted. Neurological deficit was evaluated in rats based on the Zea-Longa scoring system. Hematoxylin-eosin (HE) staining was performed to observe neuronal morphology. The expression of mTOR was detected using immunohistochemistry, and the relative expression level of tau protein was determined via Western blotting (WB). Besides, the messenger RNA (mRNA) expressions of mTOR and tau were detected by quantitative Polymerase Chain Reaction (qPCR). Finally, inflammatory factor content was measured through enzyme-linked immunosorbent assay (ELISA).

RESULTS

Model group and miR-199a mimics group exhibited a substantially higher Zea-Longa score than sham group (p<0.05). Compared with model group, the Zea-Longa score rose prominently in miR-199a mimics group (p<0.05). According to the results of HE staining, the structure of neurons in sham group was clear and intact, while the structure of neurons in model group was disordered. Meanwhile, neuronal morphology in miR-199a mimics group was significantly worse than that in model group (p<0.05). Immunohistochemistry results demonstrated that the positive expression level of mTOR was considerably upregulated in both model group and miR-199a mimics group in comparison with sham group (p<0.05). Moreover, its positive expression level in miR-199a mimics group was markedly higher that in model group (p<0.05). Based on the results of WB, model and miR-199a mimics groups exhibited a remarkably higher relative expression level of tau protein than sham group (p<0.05). However, the relative expression level of tau protein in miR-199a mimics group was prominently higher than that in model group (p<0.05). QPCR results manifested that the relative mRNA expression levels of mTOR and tau in model group and miR-199a mimics group were dramatically higher than those in sham group (p<0.05). Compared with those in model group, the relative mRNA expression levels of mTOR and tau increased significantly in miR-199a mimics group (p<0.05). ELISA results revealed that model group and miR-199a mimics group had prominently higher content of inflammatory factors than sham group (p<0.05). In addition, content of inflammatory factors in miR-199a mimics group was considerably higher than that in model group (p<0.05).

CONCLUSIONS

MiR-199a modulates mTOR expression to exert important regulatory effects on the autophagy and inflammation in rats with cerebral infarction.