LAUSR

This study investigated the role of NFAT/Fas/FasL axis in cardiomyocyte apoptosis following doxorubicin (DOX) treatment in rats and evaluated the involvement and regulation of all NFAT members in cardiac apoptosis. Forty adult male Wistar rats were divided equally into control or DOX‐treated groups (15 mg/kg over 2 weeks). Cardiomyocytes were cultured and pre‐incubated with various inhibitors and activators (10 μmol/L) prior to DOX exposure (1 μmol/L). In the left ventricles and cultured cells, DOX increased cytoplasmic protein levels of cytochrome C, Bax and increased the activities of caspase‐8, caspase3, ERK1/2, JNK, and P38 mitogen‐activated protein kinases (MAPKs), reducing levels of Bcl‐2 and the activity of mTOR, and inducing cell death. In addition, DOX enhanced mRNA and protein levels of Fas and FasL. Furthermore, the nuclear and cytoplasmic levels of NFAT1 and nuclear accumulation of NFAT2‐4were increased with DOX treatment. The inhibition of calcineurin with FK506 significantly inhibited the nuclear levels of NFAT2 and NFAT4 and the inhibition of P38 MAPK with SB203580 inhibited the nuclear and cytoplasmic accumulation of NFAT1. However, the activation of mTOR by IGF‐1 significantly lowered NFAT3. In conclusion, NFAT/Fas/FasL‐induced cell death in cardiac myocytes of DOX‐treated rats is regulated, at least, by the activation of calcineurin and P38 MAPK and inhibition of mTOR.