Tanshinone IIA improves miR-133 expression through MAPK ERK1/2 pathway in hypoxic cardiac myocytes

Tanshinone IIA is a lipid-soluble pharmacologically active compound extracted from the rhizome of Chinese herb Salvia miltiorrhiza, a well-known traditional Chinese medicine used for the treatment of cardiovascular disorders. Previous studies have identified that tanshinone IIA inhibited overexpression of miR-1 in hypoxic neonatal cardiomyocytes. This study was designed to examine the effects of tanshinone IIA on miR-133 expression under hypoxic condition. Neonatal rat cardiomyocytes were cultured in a hypoxic environment (2% O(2)+93% N(2)+5% CO(2)) at 37°C for 24 hours. MTT, TUNEL assays, and Flow Cytometry (FCM) were performed to identify cell apoptosis. Western blot was used to examine the expression of ERK1/2 and miR-133 level was quantified by Real-time PCR. Our results showed that apoptosis was induced by hypoxia. Typical apoptotic cells were seen by TUNEL assay, and FCM showed an apoptosis rate of 13.32% in hypoxic group. Apoptosis rate in hypoxic cells was reduced significantly by tanshinone IIA. In addition, the expression level of miR-133 was increased in hypoxic cells and further upregulated by tanshinone IIA. The stress-activated protein kinase MAPK ERK1/2 was activated by hypoxia and further increased with tanshinone IIA treatment. The present study demonstrated that tanshinone IIA enhanced cell resistance to hypoxic insult by upregulating miR-133 expression through activating MAPK ERK1/2 in neonatal cardiomyocytes.