Bax affects intracellular Ca2+ stores and induces Ca2+ wave propagation

In the present study, we evaluated proapoptotic protein Bax on mitochondria and Ca2+ homeostasis in primary cultured astrocytes. We found that recombinant Bax (rBax, 10 and 100 ng/ml) induces a loss in mitochondrial membrane potential (ΔΨm). This effect might be related to the inhibition of respiratory rates and a partial release of cytochrome c, which may change mitochondrial morphology. The loss of ΔΨm and a selective permeabilization of mitochondrial membranes contribute to the release of Ca2+ from the mitochondria. This was inhibited by cyclosporin A (5 μM) and Ruthenium Red (1 μg/ml), indicating the involvement of mitochondrial Ca2+ transport mechanisms. Bax-induced mitochondrial Ca2+ release evokes Ca2+ waves and wave propagation between cells. Our results show that Bax induces mitochondrial alteration that affects Ca2+ homeostasis and signaling. These changes show that Ca2+ signals might be correlated with the proapoptotic activities of Bax.