Dynamic expressions of miR-34a and related target genes sirtuin 1 and nuclear factor-E2-related factor 2 and their significances in subependymal zone of rats with cerebral ischemia

Abstract

Objective To observe the expression changes of miR-34a and its related target genes sirtuin 1 (Sirt1) and nuclear factor-E2-related factor 2 (Nrf2) in subependymal zone (SVZ) of rats after cerebral ischemia, and to explore the effect of miR-34a on proliferation of endogenous neural stem cells (NSCs) after cerebral ischemia. Methods Forty SD rats were randomly divided into control group, cerebral ischemia one d group, cerebral ischemia three d group and cerebral ischemia 7 d group (n=10). Middle cerebral artery occlusion models were established by thread embolization in the latter three groups, and the SVZs were taken one, three and 7 d after model making, respectively. Immunofluorescence staining was used to detect the expression of nestin, real-time PCR was used to detect the mRNA expressions of miR-34a, Sirt1 and Nrf2, and Western blotting was used to detect the protein expressions of Sirt1 and Nrf2. Results (1) In SVZs of cerebral ischemia one d group, cerebral ischemia three d group and cerebral ischemia 7 d group, the number of nestin positive cells increased gradually ([2.013±0.526], [4.821±1.154], and [6.394±1.027]) cells/filed, with statistical differences (P< 0.05). (2) In SVZs of cerebral ischemia one d group, cerebral ischemia three d group and cerebral ischemia 7 d group, the expression levels of miR-34a mRNA increased gradually (0.295±0.145, 0.701±0.075, and 1.136±0.018), the Sirt1 mRNA expression levels showed a downward trend (0.835±0.024, 0.620±0.133, and 0.278±0.110), the Nrf2 mRNA expression levels obviously decreased (1.032±0.256, 0.833±0.187, and 0.630±0.123), the Sirt1 protein expression levels showed a downward trend (0.832±0.018, 0.731±0.156, and 0.454±0.132), and the Nrf2 protein expression levels obviously decreased (1.003±0.133, 0.813±0.111, and 0.671±0.071), with statistically significant differences (P<0.05). (3) Statistical correlation analysis showed that the number of nestin positive cells was positively correlated with miR-34a mRNA expression level and negatively correlated with Sirt1 and Nrf2 mRNA and protein expression levels after cerebral ischemia (r=0.887, P=0.003; r=-0.746, P=0.005; r=-0.521, P=0.013; r= -0.344, P=0.025; r=-0.863, P=0.000). Conclusions MiR-34a may regulate the proliferation of NSCs through Sirt1/Nrf2 pathway after cerebral ischemia. Key words: Cerebral ischemia; MiR-34a; Sirtuin 1; Nuclear factor-E2-related factor 2; Neural stem cell; Cell proliferation