miR-21 regulates ischemic neuronal injury via the p53/Bcl-2/Bax signaling pathway

Focal cerebral ischemia leads to a large number of neuronal apoptosis, and secondary neuronal death is the main cause of cerebral infarction. MicroRNA-21 (miR-21) has been shown to be a strong anti-apoptosis and pro-survival factor in ischemia. However, the precise mechanism of miR-21 in ischemic neuroprotection remains largely unknown. In this study, miR-21 was down-regulated while p53 was up-regulated following ischemia in vitro and in vivo. Overexpression of miR-21 in vitro and in vivo substantially inhibited the expression of p53 following ischemia, while inhibition of miR-21 in vitro and in vivo promoted p53 expression following ischemia. Moreover, the miR-21/p53 axis regulated the expression of Bcl-2/Bax and abolished OGD/R-induced neuronal injury in vitro. Furthermore, overexpression of miR-21 in vivo reduced neuronal death, protected against ischemic damage, and improved neurological functions by inhibiting p53/Bcl-2/Bax signaling, while inhibition of miR-21 enhanced the p53/Bcl-2/Bax signaling and aggravated the ischemic neuronal injury in vivo. Our data uncover a novel mechanism of miR-21 in regulating cerebral ischemic neuronal injury by inhibiting p53/Bcl-2/Bax signaling pathway, which suggests that miR-21/p53 may be attractive therapeutic molecules for treatment of ischemic stroke.