Anion exchanger 3 is required for sasanquasaponin to inhibit ischemia/reperfusion‐induced elevation of intracellular Cl − concentration and to elicit cardioprotection

Recent studies have shown that the cardioprotection of sasanquasaponin (SQS) against ischemia/reperfusion injury is related to inhibiting ischemia/reperfusion‐induced elevation of intracellular Cl − concentration ([Cl − ] i ). However, the mechanism of inhibition remains unclear. Anion exchanger 3 (AE 3 ) is an important regulatory protein for [Cl − ] i . This study investigated whether AE 3 plays the critical role in the inhibitory effect of SQS on elevation of [Cl − ] i induced by ischemia/reperfusion and mediates the cardioprotection of SQS in H9c2 cells. Normal and AE 3 ‐knockdown H9c2 cells were incubated for 24 h with or without various concentrations of SQS (0.1, 1, or 10 µM) followed by simulated ischemia/reperfusion (sI/R). AE 3 expression was detected by Western blot. Flow cytometer analysis was employed to determine [Cl − ] i, [Ca 2+ ] i , reactive oxygen species (ROS) production, and cell apoptosis. The results showed that SQS pretreatment concentration‐dependently attenuated sI/R‐induced viability loss and lactate dehydrogenase leakage in normal H9c2 cells. Additionally, SQS concentration‐dependently up‐regulated AE 3 protein expression, and inhibited sI/R‐induced the elevation of [Cl − ] i followed by the attenuation of Ca 2+ overload, ROS production, and cell apoptosis. However, the dose‐dependent cardioprotection induced by SQS was abolished in AE 3 ‐knockdown H9c2 cells, and the inhibitory effects of SQS on [Cl − ] i , Ca 2+ overload, ROS production, and cell apoptosis were also reversed. Our data indicate that AE 3 mediates the cardioprotective effect of SQS against sI/R injury. Importantly, AE 3 is required for SQS to inhibit sI/R‐induced elevation of [Cl − ] i , which subsequently inhibited sI/R‐induced Ca 2+ overload, ROS production, and cell apoptosis. J. Cell. Biochem. 112: 2803–2812, 2011. © 2011 Wiley‐Liss, Inc.