Elimination of Ascorbic Acid-Induced Membrane Lipid Peroxidation and Serotonin Receptor Loss by Trolox-c, A Water Soluble Analogue of Vitamin E

Abstract

Ascorbic acid is commonly used as an antioxidant to prevent the decomposition of ligands in neurotransmitter receptor studies, but may alter biological membranes by initiating lipid peroxidation in the presence of physiologic metal ions. The aim of the present study was to characterize the effect of ascorbic acid-induced lipid peroxidation on an applicable membrane receptor and to examine an appropriate antioxidant system. Ascorbic acid generated significant lipid peroxidation (5.5 to 45 fold increase in malonaldehyde levels) in three diverse tissues having different membrane properties: bovine brain, mouse teratoma, and rat kidney. In membranes from bovine cerebral cortex, ascorbate-induced lipid peroxidation was associated with a 26% decrease in [3H]-serotonin receptor binding (Bmax = 159 +/- 11 from control of 216 +/- 10 fmol/mg protein), with no significant change in KD. Trolox-C, a water soluble analogue of vitamin E, completely blocked the ascorbate-induced loss of serotonin receptor binding in brain membranes, and the combination of Trolox-C and ascorbate prevented [3H]-serotonin decomposition in solution. Trolox-C also prevented ascorbate-induced lipid peroxidation in brain, teratoma, and kidney membranes. Lipid peroxidation may be a significant factor in the ascorbate-induced alteration of brain membranes as reflected by reduced binding to serotonin receptors. The combination of Trolox-C (200 microM) and ascorbic acid (1.0 mM) maintains a protective environment for oxygen sensitive neurotransmitters while blocking the deleterious effects of ascorbic acid on lipid membranes.

Antioxidant Enzyme and Malondialdehyde Levels in Patients with Panic Disorder

“…It has been suggested that there may be a relationship between excessive production of FRs and increased monoamine oxidation [1]. Moreover, MDA exerts an inhibitory effect on serotonin binding sites on the receptor [19]. As a result, the relationships mentioned above may be considered to demonstrate a possible etiopathogenetic association between FRs and PD.…”

Inactivation of nitric oxide by rat cerebellar slices

“…In cerebellar cell suspensions, NO consumption is predominantly the result of ascorbate and iron together initiating the formation of lipid peroxyl radicals, which avidly react with NO (O'Donnell et al 1997;Keynes et al 2005a). To determine whether this process accounts for NO consumption in cerebellar slices, we tested the transition metal chelator, DTPA and the vitamin E analogue, Trolox (Britt et al 1992), both of which inhibit lipid peroxidation-dependent NO consumption in the cell suspensions (Keynes et al 2005a). Slices were stimulated with both a sub-EC 50 concentration of NO (240 ± 30 nm NO, n = 10; generated from 10 μm Sper/NO), and a maximal concentration (100 μm DEA/NO).…”

“…To determine whether this process accounts for NO consumption in cerebellar slices, we tested the transition metal chelator, DTPA and the vitamin E analogue, Trolox (Britt et al 1992), both of which inhibit lipid peroxidation-dependent NO consumption in the cell suspensions (Keynes et al 2005a). Slices were stimulated with both a sub-EC 50 concentration of NO (240 ± 30 nm NO, n = 10; generated from 10 μm Sper/NO), and a maximal concentration (100 μm DEA/NO).…”

Protection from Inflammation, Immunosuppression and Carcinogenesis Induced by UV Radiation in Mice by Topical Pycnogenol®¶

“…The oxidant dependence of 5‐HT receptor activation is supported by evidence for superoxide scavenging by the plant extract, Gingko biloba , which effectively blocked the mitogenic effect of serotonin in cultured fibroblasts and smooth muscle cells (29). The antioxidant vitamin E analogue, Trolox‐C, has also been shown to inhibit 5‐HT receptor binding in various rat tissues (30).…”