The functional role of Bax/Bak in palmitate-induced lipoapoptosis

Induction of programmed cell death, mainly apoptosis (lipoapoptosis) is a major cellular consequence of the lipotoxicity, a harmful effect resulting from the overload of lipids. Both Endoplasmic reticulum (ER) stress and autophagy have been suggested to play important role in the regulation of lipoapoptosis. However, the exact mechanisms underlying lipoapoptosis remain unclear. In the present study, we aimed to investigate the functional role of Bax/Bak in lipoapoptosis using mouse embryonic fibroblasts (MEFs) cell culture model. Results showed that palmitate induced caspase-dependent apoptosis in wild-type Bax/Bak MEF cells, whereas a caspase-independent cell death was induced by palmitate in Bax/Bak knockout MEF cells, suggesting requirement of Bax/Bak in palmitate-induced caspase activation. More importantly, we found that the status of Bax/Bak is a determinant that governs the decision between the pro-survival or pro-death function of autophagy in response to palmitate exposure, and Bax/Bak is required for palmitate-induced activation of endoplasmic reticulum (ER) stress and subsequently ER stress-mediated apoptosis. The findings of the present study provided novel insights into understanding the mechanisms involved in the regulation of palmitate-induced lipoapoptosis.