The participation of reactive oxygen species and protein thiols in the mechanism of mitochondrial inner membrane permeabilization by calcium plus prooxidants.

We have recently shown that permeabilization of the inner mitochondrial membrane by calcium plus prooxidants is associated with oxidation of protein thiols forming cross-linked protein aggregates [Fagian, M. M., Pereira da Silva, L., Martins, I. S. and Vercesi, A. E. (1990) J. Biol. Chem. 265, 19955-19960]. In this study we show that mitochondria could regenerate and sustain a membrane potential (delta psi) comparable to the control experiment after the protein aggregates were cleaved by dithiothreitol. The addition of ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid, which removes Ca2+ but does not eliminate the protein aggregates, caused an incomplete and nonsustainable recovery of delta psi. Exogenous catalase prevented the disruption of membrane potential and decreased the production of membrane protein aggregates when mitochondria were incubated in the presence of Ca2+ alone or Ca2+ plus a prooxidant. This strongly indicates that H2O2 and possibly other H2O2-derived reactive oxygen species are involved in the mechanism of membrane protein aggregates production that may result in the process of membrane pore formation.