Tanshinone IIA protects hypoxia-induced injury by preventing microRNA-28 up-regulation in PC-12 cells.

Cerebral ischemia is the second leading cause of death and disability worldwide. Despite the neuroprotective role of Tanshinone IIA has been widely reported, the molecular mechanisms involving miRNAs remains unclear. We aimed to figure out a novel regulatory mechanism of Tanshinone IIA associated with miRNAs. Rat pheochomocytoma PC-12 cells were exposed to hypoxia, followed by assays of cell viability and apoptosis using trypan blue exclusion and flow cytometry assay, respectively. Expression of proteins associated with apoptosis was measured by Western blot analysis. Effects of Tanshinone IIA on cell viability, apoptosis and expression of miR-28 were determined. Then, whether Tanshinone IIA functioned though miR-28 was analyzed. Finally, we explored the relationship between survivin and miR-28, and whether Tanshinone IIA activated the specificity protein 1 (Sp1)/survivin pathway though modulating miR-28. Hypoxia decreased cell viability and increased cell apoptosis though mitochondrial- and caspase-dependent pathways. Tanshinone IIA treatment prevented hypoxia-induced cell injury though preventing up-regulation of miR-28. Subsequently, we found survivin expression was down-regulated by miR-28 overexpression. In addition, expression of Sp1 and survivin was down-regulated by hypoxia, and the down-regulations were attenuated by Tanshinone IIA though miR-28. We confirmed that Tanshinone IIA prevented hypoxia-induced PC-12 cell injury though preventing the up-regulation of miR-28, along with activation of the Sp1/survivin pathway in PC-12 cells under hypoxia.