Diphenylacetaldehyde-generated excited states promote damage to isolated rat liver mitochondrial DNA, phospholipids, and proteins

This work studies damage to rat liver mitochondrial protein, lipid, and DNA caused by electronically excited states generated by cytochrome c-catalyze d diphenylacetaldehyde enol oxidation to triplet benzophenone. The extensio n of lipid peroxidation was estimated by production of thiobarbituric acid- reactive substances and by formation of Schiff bases with membrane proteins , evaluated by SDS-polyacrylamide gel electrophoresis. Concomitant with DPA A-driven mitochondrial permeabilization, extensive mtDNA fragmentation occu rred and DNA adducts with aldehydes-products of fatty acid oxidation-were o bserved. The degree of lipid peroxidation and mtDNA alterations were signif icantly decreased by butylated hydroxytoluene, a potent peroxidation chain breaker. The lipid peroxidation process was also partially inhibited by the bioflavonoid rutin and urate totally prevented the mitochondrial transmemb rane potential collapse. In all cases, the mitochondrial damage was depende nt on the presence of phosphate ions, a putative bifunctional catalyst of c arbonyl enolization. These data are consistent with the notion that triplet ketones may act like alkoxyl radicals as deleterious reactive oxygen speci es on biologic structures. Involvement of singlet dioxygen formed by triple t-triplet energy transfer from benzophenone in the model reaction with DPAA /cytochrome c in the presence of DCP liposomes was suggested by quenching o f the accompanying chemiluminescence upon addition of histidine and lycopen e. (C) 1999 Elsevier Science Inc.