Relative significance of lipid peroxidation, DNA damage and ATP depletion in oxidant-induced early and late renal epithelial cell injury

Although reactive oxygen species (ROS), particularly H2O2, have been shown to mediate renal injury in several models, the exact mechanisms or the sequence of events by which oxidants cause cell injury is not clearly defined. We have previously demonstrated a critical role for lipid peroxidation in oxidant-induced early renal epithelial cell injury (Am J Physiol 268:F30-F38, 1995). Two recent studies confirm this observation, but in one, preliminary results were provided to suggest that additional targets or mechanisms might be involved in the late stage of H2O2-induced cell injury (Am J Physiol 272:F729-55, 1997). We therefore examined the importance of lipid peroxidation in relation to oxidant-induced DNA damage and ATP depletion at 2-time points, immediately and 24 hours, after a 135-min incubation of LLC-PK1 cells with 250 μM H2O2. 2-Methyl aminochroman (2-MAC), a potent lipid radical scavenger, and deferoxamine (DFO) a chelator of catalytically active iron were used in an attempt to delineate the relative roles of cellular targets and mechanisms. Cell injury (% LDH release) immediately after H2O2-incubation was associated with lipid peroxidation (thiobarbituric acid method, nmoles/mg protein), ATP depletion (luciferin-luciferase method, nmoles/mg protein), and DNA damage (alkaline-unwinding assay, % residual double stranded DNA). 2-MAC suppressed LDH release along with inhibition of lipid peroxidation, but not DNA damage or ATP depletion. Suppression of LDH release with DFO was associated with inhibition of lipid peroxidation, DNA damage and ATP depletion At 24 hours, despite continued suppression of lipid peroxidation, only DFO, but not 2-MAC, maintained significant cytoprotection against H2O2. Furthermore, only DFO, but not 2-MAC, reduced DNA damage and maintained higher ATP levels. Our findings suggest that lipid peroxidation plays an important role in the early phase of oxidant-induced cell injury but in the later stage, alternate mechanisms may predominate.