Danshensu protects against ischemia/reperfusion injury and inhibits the apoptosis of H9c2 cells by reducing the calcium overload through the p-JNK-NF-κB-TRPC6 pathway

Ischemia-reperfusion (I/R) plays an important role in myocardial injury. In the present study, we aimed to examine the protective effects of Danshensu (DSS) against I/R injury and to elucidate the underlying mechanisms. For this purpose, H9c2 cells were cultured in hypoxic solution in a hypoxic incubator for 2 h, and then cultured in a high oxygen incubator for various periods of time and pre-treated with or without DSS, ammonium pyrrolidine dithiocarbamate (PDTC) or SP600125 [a c-Jun N-terminal kinase (JNK) inhibitor]. Cell apoptosis and cytosolic free Ca²⁺ ([Ca²⁺]_i) levels were analyzed by flow cytometry. The protein expression levels of JNK, phosphorylated (p-)JNK, nuclear factor-κB (NF-κB) and transient receptor potential cation channel, subfamily C, member 6 (TRPC6) were measured by western blot analysis. The mRNA expression levels of JNK were measured by RT-qPCR. The results revealed that TRPC6 protein expression, the cell apoptotic rate and the [Ca²⁺]_i levels increased in a time-dependent manner in the H9c2 cells following the induction of I/R injury. The apoptotic rate and TRPC6 protein expression decreased when the cells were treated with DSS prior to the induction of I/R injury. The knockdown of JNK expression by siRNA decreased the p-JNK and TRPC6 protein expression levels in the H9c2 cells subjected to I/R injury. The protein expression levels of p-JNK and NF-κB in the nucleus increased significantly when the H9c2 cells were subjected to I/R injury, whereas NF-κB expression in the cytoplasm decreased in a time dependent manner. However, p-JNK, NF-κB and TRPC6 protein expression, the [Ca²⁺]_i level and cell apoptosis decreased when the H9c2 cells were pre-treated with DSS or SP600125. Therefore, our data suggest that DSS prevents myocardial I/R injury by inhibiting p-JNK activation and NF-κB translocation, which potentially upregulate TRPC6 expression, increase the [Ca²⁺]_i level, and result in the apoptosis of H9c2 cells.