Intracellular superoxide induces apoptosis in VSMCs: role of mitochondrial membrane potential, cytochrome C and caspases.

Apoptosis of vascular smooth muscle cells (VSMCs) is an integral part of cardiovascular diseases including atherosclerosis, hypertension and restenosis. Here we studied the fate of VSMCs in response to intracellular superoxide stimulation. Diethyldithiocarbamic acid (DDC) was used to inhibit copper-zinc superoxide dismutase thereby increasing intracellular superoxide levels. The results show that DDC at a dose from 25-100 micro M is able to induce VSMC apoptosis. Superoxide was found to be responsible for DDC-induced apoptosis. In the apoptotic process mitochondrial membrane potential was decreased and caspase-3, -8 and -9 were activated. Surprisingly, neither cytochrome c release nor Bid cleavage could be observed. These data suggest a role for intracellular superoxide in the regulation of VSMCs apoptosis.