Physalin A induces apoptosis via p53-Noxa-mediated ROS generation, and autophagy plays a protective role against apoptosis through p38-NF-κB survival pathway in A375-S2 cells

Abstract Ethnopharmacological relevance Physalin A is a bioactive withanolide isolated from natural plant Physalis alkekengi L. var. franchetii (Mast.) Makino, a traditional Chinese herbal medicine named Jindenglong which has long been used for the treatment of cough, sore throat, hepatitis, eczema, dysuria and tumors in China. Aim of the study Based on the previous study that physalin A induced cytotoxic effect in human melanoma A375-S2 cells, this study was designed to further illustrate the molecular mechanisms underlying. Materials and methods Cell viability was evaluated in A375-S2 cells by MTT assay, and the mechanisms involved in physalin A-induced A375-S2 cell death were investigated by phase contrast microscopy and fluorescence microscopy, siRNA transfection, flow cytometry and western blot analysis. Results We demonstrated that physalin A decreased the proportion of viable A375-S2 cells in a time- and dose-dependent manner, and exposure of A375-S2 cells to physalin A led to both apoptosis and autophagy. Moreover, physalin A-induced apoptosis was triggered by activation of p53-Noxa pathway and intracellular reactive oxygen species (ROS) generation. The administration of ROS scavengers NAC and GSH resulted in the complete inhibition of physalin A-induced ROS generation and apoptosis. Application of p53 inhibitor PFT- α or transfection with Noxa-siRNA could also lead to the same results. Autophagy, demonstrated by the punctuate distribution of monodansylcadaverine staining, as well as the change of LC3-II/LC3-I proportion and Beclin 1 activation, played a protective role against apoptosis via up-regulation of the p38-NF-κB survival pathway in A375-S2 cells. Additionally, inhibition of autophagy by the specific autophagic inhibitor 3MA or blocking the p38-NF-κB pathway with p38 inhibitor SB203580 or NF-κB inhibitor PDTC obviously promoted physalin A-induced apoptosis. Conclusions Physalin A induced apoptotic cell death via p53-Noxa-mediated ROS generation, and autophagy played a protective role against apoptosis through up-regulating the p38-NF-κB survival pathway in A375-S2 cells. These results stated the possibility that physalin A would be a potential agent for the treatment of melanoma in the future.