The mechanism of the hypochlorite-induced lipid peroxidation

The article reviews data related to the role of exogenic hypochlorite (HOCl/OCl-) and hypochlorite produced by myeloperoxidase catalysis in initiation of lipid peroxidation (LPO) in phospholipid membranes and human blood lipoproteins (LP). It has been shown that HOCl/OCl- promotes free radical lipid oxidation in liposomes and LP that is followed by the formation of LPO products; hydroperoxides, conjugated dienes, TBARS, and fluorescent products. Water soluble reactive substances (.O2-, H2O2, Fe2+) which can be present in the reaction mixture as a dopant are not the source of free radicals and do not participate in HOCl/OCl(-)-induced LPO at the initiation step. The main reaction of HOCl/OCl- with unsaturated lipid is probably the generation of chlorohydrins. However, this reaction is not accompanied by generation of free radicals and LPO. HOCl/OCl- reacts efficiently with TBARS of aldehydic nature. It is likely that the reaction proceeds without the participation of free radicals. Among the compounds of a peroxide nature (hydro-, dialkyl-, diacyl-, alkyl-acyl-peroxide groups and epoxides) only hydroperoxides react with HOCl/OCl-. This reaction is accompanied by the production of free radicals (but not singlet oxygen), probably alkoxyl radicals, which may play a role in the initiation of HOCl/OCl(-)-induced LPO.