vitamin-k-semiquinone-radical and 6-hydroxy-2-5-7-8-tetramethylchroman-2-carboxylic-acid

In studies into the oxidative burst in RAW 264 monocyte/macrophages, it was observed that capsaicin, a vanilloid receptor agonist, stimulated dichlorofluorescin (DCFH) oxidation in a concentration-dependent manner, which could be blocked by capsazepine, a vanilloid receptor antagonist. However, by use of a number of vanilloid agonists (including N-octyl-3-chloro-4-hydroxyphenylacetamide, 4m), we demonstrated that there was no relationship between vanilloid agonist potency and the capacity to stimulate DCFH oxidation. The oxidative burst stimulators Tween 20 and phorbol myristyl acetate (PMA) also stimulated reactive oxygen species generation, which again was inhibited by capsazepine. Use of the selective inhibitor diphenyliodonium iodide ruled out a role for plasma membrane NAD(P)H oxidase as the site of capsaicin- and 4m-stimulated DCFH oxidation. However, this DCFH oxidation was modulated by a number of inhibitors of mitochondrial respiration. Rotenone enhanced DCFH oxidation induced by capsaicin and 4m, whilst malonic acid and potassium cyanide inhibited this response. 2,4-Dinitrophenol, an inhibitor of oxidative phosphorylation, was without effect. The antioxidant trolox c inhibited DCFH oxidation stimulated by capsaicin, 4m, and PMA, whereas N-acetylcysteine, a precursor of glutathione, was without effect. Capsazepine inhibited DCFH oxidation in unstimulated cells and in cells treated with menadione, a redox-cycling quinone. Capsazepine was also a potent antioxidant when measured in a Fe3+ reduction assay. We concluded that DCFH oxidation stimulated by vanilloid analogues was not mediated via a vanilloid receptor, but rather by impairment of mitochondrial electron transport.

Topics: Acetylcysteine; Animals; Antioxidants; Capsaicin; Carcinogens; Chromans; Fluoresceins; Macrophages; Mice; Monocytes; Oxidation-Reduction; Polysorbates; Reactive Oxygen Species; Receptors, Drug; Surface-Active Agents; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Vitamin K

We reported previously that purpurogallin (PPG) markedly protects the cultured rabbit corneal endothelial cells (RCEC) against oxyradical damage generated with hypoxanthine (HX) and xanthine oxidase (XO)(1). In this study, we further compared the cytoprotective activities of PPG versus Trolox (TX, alpha-tocopherol, a water-soluble analogue of vitamin E) and ascorbate (Asc) in confluent cultured RCEC with phase contrast microscopy and confirmed by transmission electron microscopy. PPG prolonged survival of the oxyradical damaged cells longer than those without PPG present (18.6 +/- 1.4 min at 1.0 mM and 11.2 +/- 1.0 at 0.25 mM respectively vs. 7.3 +/- 0.8 min in control). At levels equimolar to PPG, TX, and Asc were less effective in delaying cell necrosis caused by HX and XO (p < 0.01). When exposed to superoxide radicals generated by menadione, RCEC necrosed at 29.8 +/- 1.5 min compared to PPG 47.2 +/- 1.0 min at 1.0 mM and 38.9 +/- 1.0 min at 0.25 mM. This was significantly different from TX and Asc at corresponding concentrations (p < 0.01). PPG scavenges not only HX-XO-generated oxyradicals, but also nonenzymatically produced superoxide radicals, more actively than two well known antioxidants--TX and Asc.

Topics: Animals; Antioxidants; Ascorbic Acid; Benzocycloheptenes; Cell Death; Cell Survival; Cells, Cultured; Chromans; Endothelium, Corneal; Free Radical Scavengers; Free Radicals; Hypoxanthine; Hypoxanthines; Rabbits; Reactive Oxygen Species; Solubility; Vitamin K; Xanthine Oxidase

Cultured rat glomerular mesangial cells were damaged when exposed to oxyradicals generated either from xanthine oxidase plus hypoxanthine, or by superoxide radicals formed from menadione. Morin hydrate is an antioxidant extracted from yellow Brazil wood. When morin hydrate was added to cultured rat glomerular mesangial cells which were attacked by oxyradicals generated by xanthine oxidase plus hypoxanthine, the survival time of the cells was doubled. However, this protective effect of morin hydrate was less marked when the cells were attacked by menadione. Note that the protective effects of Trolox which is a polar analogue of vitamin E were miniscule relative to those of morin hydrate with both oxidants.

Topics: Animals; Antioxidants; Cell Survival; Cells, Cultured; Chromans; Flavonoids; Free Radicals; Glomerular Mesangium; Hypoxanthine; Hypoxanthines; Microscopy, Electron; Rats; Reactive Oxygen Species; Superoxides; Vitamin K; Xanthine Oxidase

Morin is a yellowish pigment extractable from the wood of Chlorophora tinctoria. In the present study, we have determined that morin protects three types of human cells--ventricular myocytes, saphenous vein endothelial cells, and erythrocytes--against damage by oxyradicals generated in situ. In myocytes and endothelial cells, morin prolonged substantially and in a concentration-dependent manner the survival of cells exposed to either xanthine oxidase-generated oxyradicals or superoxide radicals produced with menadione. Morin protected erythrocytes from lytic attack by peroxyl radicals generated with 2,2'-azo-bis (2-amidinopropane) dihydrochloride. In all three types of human cells, the protective effect of morin clearly excelled that displayed by Trolox (a vitamin E analog), ascorbate, or mannitol, which are water-soluble antioxidants of similar molecular size. Chemically, we verified that morin behaves as an antioxidant by diminishing markedly the amount of malondialdehyde (lipid peroxidation product) found in human cardiocytes despite their exposure to oxyradicals. In agreement with related reports, we also observed that morin is non-toxic in rats even when used at concentrations 2-3 orders of magnitude higher than those in our in vitro studies. Thus, morin acts as a broad-spectrum and non-toxic antioxidant.

Topics: Ascorbic Acid; Cells, Cultured; Chromans; Endothelium, Vascular; Erythrocytes; Flavonoids; Free Radical Scavengers; Heart Ventricles; Humans; Malondialdehyde; Mannitol; Reactive Oxygen Species; Vitamin K; Wood