Inhibition of mitochondrial permeability transition pores by cyclosporine a improves cytochrome c oxidase function and increases rate of ATP synthesis in failing cardiomyocytes

Background: We previously showed that mitochondrial respiratory function is abnormal in dogs with chronic heart failure (HF). Mitochondrial permeability transition pores (MPTP) can affect mitochondrial inner membrane potential (Delta Psi(m)) and mitochondrial function in normal cardiomyocytes. The potential impact of MPTP on Delta Psi(m) and mitochondrial respiratory function in HF has not yet been determined. We tested the hypothesis that cyclosporine A, a potent blocker of the MPTP, can improve mitochondrial function in HF. Methods: Cardiomyocytes were isolated from the left ventricular myocardium of 7 dogs with HF produced by intracoronary microembolizations and from 7 normal dogs. Cardiomyocytes were treated for 24 hours with cyclosporine A. Delta Psi(m), cytochrome c oxidase protein expression, mitochondrial cytochrome c oxidase-dependent respiration (CDOR) and ATP synthesis were measured. Results: Delta Psi(m), protein expression of cytochrome c oxidase, CDOR and the rate of ATP synthesis were decreased in HF compared to normal controls. Inhibition of MPTP in failing cardiomyocytes with low dose of cyclosporine A (0.2 mu M) increased Delta Psi(m), preserved expression of cytochrome c oxidase, improved CDOR and the rate of ATP synthesis. Conclusion: MPTP opening contributes to the loss of mitochondrial function observed in the failing heart. Inhibition of MPTP opening represents a potential therapeutic target for the treatment of HF.