Aspirin Induces Mitochondrial Ca2+ Remodeling in Tumor Cells via ROS-Depolarization-Voltage-Gated Ca2+ Entry

Aspirin (acetylsalicylic acid) and its metabolite salicylate, have an anti-melanoma effect by evoking mitochondrial dysfunction through poorly understood mechanisms. Depolarization of the plasma membrane potential leads to voltage-gated Ca2+ entry (VGCE) and caspase-3 activation. In the present study, we investigated the role of depolarization and VGCE in aspirin's anti-melanoma effect. Aspirin and to a lesser extent, salicylate (>= 2.5 mM) induced a rapid (within seconds) depolarization, while they caused comparable levels of depolarization with a lag of 2-4 h. Reactive oxygen species (ROS) generation also occurred in the two-time points, and antioxidants abolished the early ROS generation and depolarization. At the same concentrations, the two drugs induced apoptotic and necrotic cell death in a caspase-independent manner, and antioxidants and Ca2+ channel blockers prevented cell death. Besides ROS generation, reduced mitochondrial Ca2+ (Ca-m(2+)) and mitochondrial membrane potential preceded cell death. Moreover, the cells expressed the Ca(v)1.2 isoform of l-type Ca2+ channel, and knockdown of Ca(v)1.2 abolished the decrease in Ca-m(2+). Our findings suggest that aspirin and salicylate induce Ca-m(2+) remodeling, mitochondrial dysfunction, and cell death via ROS-dependent depolarization and VGCE activation.