Effect of solution ionic strength on lipid peroxidation initiation by the perhydroxyl (xanthine oxidase-derived) and peroxyl radicals

Abstract

The role of solution ionic strength in perhydroxyl (HOO.) and peroxyl (ROO.) radical initiated lipid peroxidation has been defined and investigated. Xanthine oxidase activity was used as the source of superoxide (O2-) and its conjugate acid (HOO.) in these experiments. While the enzyme's activity varied with changes in ionic strength, the effect could be factored out of the lipid peroxidation studies. Both HOO.- and ROO.-initiated peroxidations of linoleic acid were promoted by increases in solution ionic strength: the inclusion of 0.1 M of various alkali metal salts in the reaction resulted in up to a 4-fold increase in the overall peroxidation rate. Significant differences between alkali metal cations (Li+, Na+, K+, Cs+) and halogen anions (F-, Cl-, Br-) were not observed. Thus, the increased rates of lipid peroxidation were attributable to changes in solution ionic strength rather than specific ion-reaction interactions. Ionic stimulation of lipid peroxidation occurred only in the presence of preexisting fatty acid hydroperoxides (LOOHs), which provided additional support for the hydrogen atom transfer mechanism previously proposed [Aikens, J., and Dix, T. A. (1991) J. Biol. Chem. 266, 15091] for the HOO./LOOH initiation process. Physiologically appropriate salt concentrations were used in these studies, hence the results may have biological significance.

Inactivation of bacteria using dc corona discharge: role of ions and humidity

“…It is well known that these reactions can create long chains for both positive and negative ions and these chains may be much longer than the OH oxidation of organic molecules discussed above. Careful biophysical studies [25] show that the greater catalytic effect of charged species is related to the various hydrogen atom transfer reactions, and could be due to both transition-state and product stabilization by increased solution ionic strength. At the same time, radicals derived from O 2 are believed to be important in the initiation of lipid peroxidation-associated oxidative damage in biological systems [25].…”

“…Careful biophysical studies [25] show that the greater catalytic effect of charged species is related to the various hydrogen atom transfer reactions, and could be due to both transition-state and product stabilization by increased solution ionic strength. At the same time, radicals derived from O 2 are believed to be important in the initiation of lipid peroxidation-associated oxidative damage in biological systems [25]. The role of water vapors in the plasma system may be related to charged water clusters which carry both charge and radicals (e.g.…”

Mechanisms and biological relevance of lipid peroxidation initiation

“…The Reaction of HOO* and LOOH. The initiating ability of HOO* is increased at least 3 orders of magnitude by the inclusion of LOOHs (e.g., 13-LOOH) in the lipids to be peroxidized (117,279). A hydrogen atom chain transfer between HOO* and LOOH has been implicated (Figure 13) (117,279), by direct analogy to the wellestablished ROO*, ROOH hydrogen atom transfer (eq 1).…”

Oxidation of DNA bases, deoxyribonucleosides and homopolymers by peroxyl radicals

“…Initial efforts in our laboratory along these lines involved determining the reactivity of each of the individual O # -derived oxidants with lipids and lipid hydroperoxides [9][10][11][12][13]. Both ROOd and O # d − \HOOd exhibited distinctly different patterns of re-dihydroxy derivatives that are formed by oxidative damage in cells.…”