Dissipation of Mitochondrial Membrane Potential by Exogenous Phospholipid Monohydroperoxide and Protection against This Effect by Transfection of Cells with Phospholipid Hydroperoxide Glutathione Peroxidase Gene

Abstract

Two hours after its addition to cultures of a guinea pig cell line, 104C1, dilinoleoyl phosphatidylcholine monohydroperoxide (PCOOH) at concentrations of 5-160 μM induced a dissipation of the mitochondrial inner membrane potential (ΔΨm), without any apparent morphological changes, in the cells. The PCOOH-induced loss of ΔΨmwas restored 4 hr after the replacement of the medium with PCOOH-free fresh medium. In contrast, 104C1/O4C cells, a stable clone from 104C1 cells transfected with the human phospholipid hydroperoxide glutathione peroxidase (PHGPx) gene encoding a sequence including a signal peptide towards mitochondria, were resistant to the loss of ΔΨmafter a 2-hr exposure to PCOOH at concentrations up to 160 μM. Even after an 8-hr exposure to 80 μM PCOOH, the transfected cells retained their ΔΨmintact, though the parent cells were killed by the same treatment. The present results strongly suggest that the expression of PHGPx protected the host cells from PCOOH-mediated injury at least by protecting their mitochondria from lipid hydroperoxide-induced loss of ΔΨm.