Synergistic protective effect of cyclosporin A and rotenone against hypoxia-reoxygenation in cardiomyocytes.

Reperfusion of the heart after an ischemic event leads to the opening of a nonspecific pore in the inner mitochondrial membrane, the mitochondrial permeability transition pore (mPTP). Inhibition of mPTP opening is an effective strategy to prevent cardiomyocyte death. The matrix protein cyclophilin-D (CypD) is the best-known regulator of mPTP opening. In this study we confirmed that preconditioning and postconditioning with CypD inhibitor cyclosporin-A (CsA) reduced cell death after hypoxia-reoxygenation (H/R) in wild-type (WT) cardiomyocytes and HL-1 mouse cardiac cell line as measured by nuclear staining with propidium iodide. The complex I inhibitor rotenone (Rot), alone, had no effect on HL-1 and WT cardiomyocyte death after H/R, but enhanced the native protection of CypD-knocked-out (CypD KO) cardiomyocytes. Reduction of cell death was associated with a delay of mPTP opening challenged by H/R and observed by the calcein loading CoCl(2)-quenching technique. Simultaneous inhibition of complex I and CypD increased in a synergistic manner the calcium retention capacity in permeabilized cardiomyocytes and cardiac mitochondria. These results demonstrated that protection by complex I inhibition was CypD dependent.