Celastrol prevents cadmium‐induced neuronal cell death by blocking reactive oxygen species‐mediated mammalian target of rapamycin pathway

Background and Purpose Increasing evidence has suggested cadmium (Cd), as an inducer of reactive oxygen species (ROS), is a potential pathogenic factor in human neurodegenerative diseases. Thus, it is important to find effective interventions for Cd-induced oxidative stress in the central nervous system. The purpose of this study was to determine whether and how celastrol, a plant-derived triterpene, could mitigate Cd-induced ROS and cell death in neuronal cells. Experimental Approach PC12, SH-SY5Y cells and primary murine neurons were chosen as a model to study celastrol neuroprotection against Cd-poisoning. Cd-induced changes in cell viability, apoptosis, ROS, and AMPK/mTOR pathway in the cells were analyzed by trypan blue exclusion, DAPI and TUNEL staining, ROS imaging, immunofluorescence staining and Western blotting. Pharmacological and genetic approaches were employed to investigate the mechanisms underlying Cd neurotoxicity. Results Celastrol attenuated Cd-induced apoptosis by suppressing Cd activation of mTOR, which was attributed to preventing Cd inactivation of AMPK. Inhibition of AMPK with compound C or expression of dominant negative AMPKα prevented celastrol from hindering Cd-induced dephosphorylation of AMPKα, activation of mTOR, and apoptosis. Inhibition of mTOR with rapamycin or knockdown of mTOR potentiated celastrol's prevention of Cd-induced phosphorylation of S6K1/4E-BP1 and apoptosis. Moreover, we further demonstrated that celastrol attenuated Cd-induced cell death by suppressing induction of mitochondrial ROS. Conclusions and Implications Celastrol prevents mitochondrial ROS inactivation of AMPK, thus attenuating Cd-induced mTOR activation and neuronal apoptosis. Celastrol may be a promising agent for prevention of Cd-induced oxidative stress and neurodegenerative diseases.