Oxidative damage to mitochondria is mediated by the Ca2+-dependent inner-membrane permeability transition

Abstract

The ability of O2 metabolites derived from the xanthine-xanthine oxidase system to inhibit mitochondrial function was examined using freshly isolated rat liver mitochondria. Under 2,4-dinitrophenol-uncoupled conditions, mitochondria exposed to free radicals exhibited a significant decrease in O2 consumption supported by NAD(+)-linked substrates, but showed almost no change in O2 consumption in the presence of succinate and ascorbate. Oxidative stress caused the loss of intramitochondrial nicotinamide nucleotides, and addition of NAD+ fully prevented any fall in O2 consumption with NAD(+)-linked substrates. The activity of electron-transfer complex I (NADH oxidase and NADH-cytochrome c oxidoreductase) and the energy-dependent reduction of NAD+ by succinate were unaltered by oxidative stress. Exposure to free radicals also had an uncoupling effect at all three coupling sites. The degree of mitochondrial swelling was closely correlated with the inhibition of State-3 oxidation of site-I substrates and with the increase in State-4 oxidation of succinate. The immunosuppressive agent cyclosporin A completely prevented the mitochondrial damage induced by oxygen free radicals (swelling, Ca2+ release, sucrose trapping, uncoupling and selective inhibition of the mitochondrial respiration of site-I substrates). The same protective effect was found when Ca2+ cycling was prevented, either by chelating Ca2+ with EGTA or by inhibiting Ca2+ reuptake with Ruthenium Red. These findings suggest that the deleterious effect of free radicals on mitochondria in the present experimental system was triggered by the cyclosporin A-sensitive and Ca(2+)-dependent membrane transition, and not by direct impairment of the mitochondrial inner-membrane enzymes.

Intestinal mucosal alterations in rats with carbon tetrachloride-induced cirrhosis: Changes in glycosylation and luminal bacteria

“…Scraped intestinal mucosa from the duodenum and proximal part of the jejunum were used for preparation of mitochondria by differential centrifugation as described. 21 Mitochondrial function was assessed by oxygen uptake, 22 swelling, 23 and MTT reduction. 24 Isolation of Surfactant, Brush Border Membranes and Measurement of D-Glucose Uptake and Carbohydrate Content.…”

Ischemic Preconditioning Prevents Free Radical Production and Mitochondrial Depolarization in Small-for-Size Rat Liver Grafts

“…ROS directly damage mitochondrial membranes and trigger opening of PT pores (27)(28)(29). Free radical-scavenging polyphenols block mitochondrial depolarization in small liver grafts (26), indicating that MPT onset is a ROS-dependent phenomenon.…”

“…ROS trigger onset of the MPT (27)(28)(29). Accordingly, we investigated whether IP prevents ROS production after partial liver transplantation.…”

“…Our recent study showed that N-methyl-4-isoleucine cyclosporin, a specific inhibitor of the MPT, prevents mitochondrial depolarization and mitigates graft injury after small-for-size liver transplantation (26). Reactive oxygen species (ROS) promote opening of PT pores (27)(28)(29). Free radicals increase markedly after transplantation of small-for-size liver grafts, and potent antioxidant polyphenols prevent mitochondrial depolarization and decreased injury of small-for-size liver grafts (19,20,26).…”

Mechanism of cytotoxicity of paraquat

“…2+ -dependent inner-membrane permeability transition It was reported that oxidative damage to mitochondria was mediated by Ca 2+ -dependent inner-membrane permeability transition and that the deleterious effect of free radicals on mitochondria was triggered by the cyclosporin A-sensitive and Ca 2+ -dependent membrane transition (43). Another report also suggested that paraquat caused opening of the cyclosporin A-sensitive, Ca 2+ -dependent permeability transition pore synergistically with NO (44).…”