Notably, basal respiration was decreased in cells harboring HCV

proteins, yet oxygen consumption could still be stimulated by FCCP, suggesting that HCV protein expression affected ATP synthesis. This result is consistent with our recent report showing a significant inhibition of the FoF1 ATP-ase activity in HCV protein-expressing cells.23 Consistently, CypD was found to affect synthesis and hydrolysis of ATP by binding ATP synthase with CsA modulating this binding and, thereby, the activity of the ATP synthase.25 This could contribute to the observed rescue of resting respiration by alisporivir. A major trigger Target Selective Inhibitor Library solubility dmso of MPTP opening is mitochondrial calcium overload.15 By using the calcium probe Rhod-1, which specifically detects intramitochondrial calcium (mtCa2+), we previously found that HCV protein expression Selleck GSI-IX for 48 hours resulted in a significant increase of mtCa2+.19 Inhibitors of the mitochondrial calcium uniporter

or of the endoplasmic reticulum (ER) calcium channel efficiently prevented mitochondrial calcium overload.19, 20 Importantly, alisporivir prevented mtCa2+ accumulation in a dose-dependent fashion. As shown in Fig. 3, maximal protective effect was already observed at a concentration of 0.125 μM. Mounting evidence from experimental and clinical observations indicates that HCV infection is causally linked with alterations of the intracellular redox state and that these may be involved in the pathogenesis of hepatitis C.20 Notably, oxidative stress proved to be a condition favoring MPTP opening.26, 27 As reported previously,19 HCV protein expression resulted in a marked increase of cellular ROS

production, as assessed by the hydrogen peroxide-sensitive fluorescent probe dichlorofluorescein (Fig. 4A). Closer analyses by LSCM revealed a bright fluorescence signal in intracellular compartments corresponding to the mitochondrial network. Alisporivir prevented ROS production as a result of HCV protein expression at a concentration as low as 0.125 μM (Fig. 4B). The results above clearly demonstrate that alisporivir prevents HCV protein-mediated mitochondrial selleck kinase inhibitor dysfunction. Next, we asked whether alisporivir may also revert already established mitochondrial dysfunction. To this end, treatment with alisporivir at a concentration of 0.125 μM was initiated 36 hours after the induction of HCV protein expression. As shown in Fig. 5A-C, alisporivir reverted within 12 hours HCV protein-mediated collapse of the mtΔΨ, production of ROS and mitochondrial calcium overload of mtCa2+. Thus, alisporivir cannot only prevent but also revert already established mitochondrial dysfunction in this experimental setting. Opening of the MPTP elicits redistribution of small proapoptotic proteins located in the mitochondrial intermembrane space, such as cytochrome c, to the extramitochondrial compartment.12 As shown in Fig. 6A, inducible expression of the HCV polyprotein resulted in a marked change of the cytochrome c–related immunofluorescence detection.