Effect of Poria cocos on hypertonic stress‐induced water channel expression and apoptosis in renal collecting duct cells

Aquaporin‐2 (AQP2), a family of water channels, plays an important role in the urinary concentrating process and regulation of water balance in the kidney. The dried sclerotia of Poria cocos Wolf (WPC) has been used for chronic edema and nephrosis. This study was conducted to evaluate the effects of WPC on hypertonic stress (175 mM NaCl)‐induced AQP2 expression and apoptosis in murine inner medullary collecting duct cell line (mIMCD‐3). WPC significantly attenuated the hypertonicity‐induced AQP2 protein and mRNA levels and blocked the apical membrane insertion of AQP2 in a concentration‐dependent manner. Tonicity‐responsive enhancer binding protein (TonEBP) mRNA was also recovered by WPC under hypertonic stress. Furthermore, pretreatment with WPC presented the similar effect with KT5720 which was decreased hypertonic stress‐induced AQP2 expression. On the other hand, WPC significantly recovered hypertonic stress‐injured mIMCD‐3 viability and cell number. WPC markedly inhibited hypertonic stress‐induced Bax or caspase‐3 expression, whereas Bcl‐2 expression was increased. Besides, WPC attenuated the hypertonicity‐induced morphological changes in nuclei, resulting in anti‐apoptotic effect. Thus, these data suggests that WPC has beneficial effects on the therapeutic approach to renal disorder.