Sasanquasaponin promotes cellular chloride efflux and elicits cardioprotection via the PKCε pathway

Sasanquasaponin (SQS) is an active component of Camellia oleifera Abel. A recent study by our group demonstrated that SQS was able to inhibit ischemia/reperfusion‑induced elevation of the intracellular chloride ion concentration ([Cl‑]i) and exerted cardioprotective effects; however, the underlying intracellular signal transduction mechanisms have yet to be elucidated. As protein kinase C ε (PKCε) is able to mediate Cl‑ homeostasis, the present study investigated its possible involvement in the effects of SQS on cardiomyocytes subjected to ischemia/reperfusion injury. Cardiomyocytes were pre‑treated with or without SQS or SQS plus εV1‑2, a selective PKCε inhibitor, followed by simulated ischemia/reperfusion (sI/R). The effects on cell viability, PKCε phosphorylation levels, [Cl‑]i, mitochondrial membrane potential and reactive oxygen species (ROS) production were assessed using an MTS assay, western blot analysis, colorimetric assays and flow cytometry. The results revealed that treatment with SQS prior to sI/R increased the viability of cardiomyocytes, and efficiently attenuated lactate dehydrogenase and creatine phosphokinase release induced by sI/R. In addition, SQS promoted PKCε phosphorylation and inhibited sI/R‑induced elevation of [Cl‑]i, paralleled by the attenuation of mitochondrial membrane potential loss and ROS generation. However, when the cardiomyocytes were treated with εV1‑2 prior to SQS pre‑conditioning, the cardioprotection induced by SQS was reduced and the inhibitory effects of SQS on sI/R‑induced elevation of [Cl‑]i, production of ROS and loss of mitochondrial membrane potential were also attenuated. These findings indicated that SQS may inhibit sI/R‑induced elevation of [Cl‑]i through the PKCε signaling pathway to elicit cardioprotection in cultured cardiomyocytes.