Sulfoxides Superoxide dismutase

MPTP decreases glutathione levels and increases the levels of reactive oxygen species and the degree of lipid peroxidation in mouse brain slices in vitro and increases the levels of reactive oxygen species in mouse brain in vivo. MPTP neurotoxicity in vitro is reduced by glutathione. In vitro studies have shown that MPP neurotoxicity can be reduced by vitamin E, vitamin C, coenzyme Q, and mannitol (but not by superoxide dismutase, catalase, allopurinol, or dimethyl sulfoxide). P-Carotene, vitamin C, and /V-acctylcystcine partially protect against the neurotoxic effects of MPTP in mice, as do nicotinamide, coenzyme Q, and the free-radical spin trap A-tert-butyl-a-(sulfophenyl) nitrone. 

The generation of O2 from potassium superoxide was also applied to stop-flow procedures. In this method O2 was dissolved in dimethyl sulfoxide and stabilized in 18-crown-6-polyether. This method is useful for mechanistic studies indeed, McClune and Fee (1976) were able to obtain catalytic rate constants for bovine copper/zinc superoxide dismutase as a function of pH in various buffers. More recently the mechanism of catalysis and of anion inhibition of iron superoxide dismutase from E. coli have been examined by this method using a specially constructed stop-flow spectrophotometer (Bull and Fee, 1985). A limitation of the method is that the pre-equilibrium state cannot be properly investigated because of the time resolution of the stop-flow equipment (== 5 msec). 

Microglia, when stimulated by phorbol ester or opsonified zymosan, gave rise to electron paramagnetic resonance spectra characteristic of superoxide (Sankarapandi etal. 1998). Experiments performed in the presence of superoxide dismutase, catalase, deferoxamine, and dimethyl sulfoxide excluded generation of hydroxyl radicals in significant amounts. Microglial superoxide generation was blocked by the NADPH oxidase inhibitor di-phenylene iodonium in a manner similar to that... 

Figure 5 The integrated antioxidant defense system comprises both endogenous and dietary-derived antioxidants. GR, glutathione reductase (EC1.6.4.2) GSH, reduced glutathione GSH-Px, glutathione peroxidase (EC1.11.1.9) GSSG, oxidized glutathione GST, glutathione-S-transferase (EC 2.5.1.18) MSR, methionine sulfoxide reductase (EC1.8.4.5) NADPH and, NADP, are, respectively, the reduced and oxidized forms of the co-factor nicotinamide adenine dinucleotide phosphate PUFA, polyunsaturated fatty acid S-AA, sulfur amino-adds SH, sulfydryl SOD, superoxide dismutase (EC1.15.1.1).

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