Interactions of Nitric Oxide with Lipid Peroxidation Products under Aerobic Conditions: Inhibitory Effects on the Formation of Malondialdehyde and Related Thiobarbituric Acid-Reactive Substances

Under aerobic conditions, exposure of peroxidized lipids to nitric oxide (NO) was found to result in a rapid decrease in the levels of thiobarbituric acid-reactive substances (TEARS), Addition of 10-100 mu M NO to rat brain homogenates preincubated for 2 h at 37 degrees C caused up to a 20% decrease in the levels of TEARS compared to controls. A similar inhibitory effect was observed on TEARS produced by Fe2+-induced decomposition of 15-hydroperoxyeicosatetraenoic acid (15-HPETE), due apparently to NO-induced decomposition of the hydroperoxide (ferrous oxidation/xylenol orange assay). Prostaglandin G(2) (PGG(2), 35 mu M), as a model bicyclic endoperoxide, and malondialdehyde (MDA, 20 mu M), the main component of TEARS, proved also susceptible to degradation by NO or NO donors (diethylamine NONOate, DEA/NO) at concentrations of 100 mu M or higher in 0.05 M phosphate buffer, pH 7.4, and at 37 degrees C, as indicated by the reduced response to the TEA assay. No significant effect on TEARS determination was caused by nitrite ions. These and other data indicate that NO can inhibit TEARS formation by decomposing primary lipid peroxidation products, chiefly 15-HPETE and related hydroperoxides, and, to a lesser extent, later stage TEARS precursors, including bicyclic endoperoxides and MDA, via nitrosation and other oxidative routes, without however affecting chromogenic reactions during the assay.