Lentinan protects cardiomyocytes against hypoxia-induced injury by regulation of microRNA-22/Sirt1.

Myocardial ischemia is a serious disease which threatens human's life. Lentinan (LEN) possesses multiple biological properties: anticancer, antibacterial, antiviral and antioxidant effects. Our study investigated the effects of LEN on hypoxia-stimulated cardiomyocytes and the underlying mechanism. Primary neonatal rat ventricular cardiomyocytes (PNCM) were isolated from neonate rat pups. PNCM and H9c2 cells were stimulated by hypoxia and treated by LEN. Cell viability and apoptosis were detected by cell counting kit-8 and flow cytometry, respectively. Moreover, apoptotic factors were examined by western blot. Phosphatidylinositol 3'-kinase (PI3K)/protein kinase B (AKT) and β-catenin pathways related proteins were analyzed by western blot. Furthermore, the expression of microRNA-22 (miR-22) was detected by qRT-PCR. Altered expression of miR-22 and silenced information regulator 1 (Sirt1) was achieved by transfection. The relationship between miR-22 and Sirt1 was verified by luciferase assay. We found that LEN promoted cell viability and decreased apoptosis which led to the contrary results with what hypoxia induced. Moreover, LEN decreased the ratio of Bax to Bcl-2 and the level of cleaved caspase-3, as well as activated PI3K/AKT and β-catenin. LEN decreased the expression of miR-22 which was upregulated by hypoxia. miR-22 overexpression broken the promoting effects led by LEN. Moreover, Sirt1 was verified to be a target of miR-22. Silence of Sirt1 led to the opposite results with LEN. In conclusion, LEN relieved hypoxia-induced cellular injuries evidenced by increasing viability and decreasing apoptosis via down-regulation of miR-22, which was accompanied by activation of PI3K/AKT and β-catenin pathways. Highlights Lentinan alleviates hypoxia-induced injuries of PNCM and H9c2 cells; microRNA-22 expression is decreased by lentinan; Lentinan reduces hypoxia-induced injury by microRNA-22 downregulation; Lentinan regulates PI3K/AKT and Wnt/β-catenin by regulation of microRNA-22/Sirt1.