Mistletoe alkali inhibits peroxidation in rat liver and kidney

AIM： To explore the antioxidant and free radica scavenger properties of mistletoe alkali （MA）. METHODS： The antioxidant effect of mistletoe alkali on the oxidative stress induced by carbon tetrachloride （CCh） in rats was investigated. The rats were divided into four groups （n = 8）： CCh-treated group （1 mL/kg body weight）, MA -treated group （90 mg/kg）, CCh＋MA-treated group and normal control group. After 4 wk of treatment, the level of malondialdehyde （MDA）, a lipid peroxidation product （LPO） was measured in serum and homogenates of liver and kidney. Also, the level of glutathione （GSH）, and activities of glutathione reductase （GR）, glutathione peroxidase （GSPx）, superoxide dismutase （SOD）, and glutathione-S-transferase （GST） in liver and kidney were determined. Scavenging effects on hydroxyl free radicals produced in vitro by Fenton reaction were studied by ESR methods using 5,5-dimethyl-1-pyrroline-N-oxide （DMPO） as a spin trap reagent and H2O2/UV as the OH· source. Urinary 8-hydroxydeoxyguanosine （8-OHdG） was determined by competitive ELISA. RESULTS： In CCh-treated group, the level of LPO in serum of liver and kidney was significantly increased compared to controls. The levels of GSH and enzyme activities of SOD, GSPx and GR in liver and kidney were significantly decreased in comparison with controls. In CCl4＋MA-treated group, the changes in the levels of LPO in serum of liver and kidney were not statistically significant compared to controls. The levels of SOD, GSPx and GR in liver and kidney were significantly increased in comparison with controls. There was a significant differ- ence in urinary excretion of 8-OHdG between the CCh- treated and MA-treated groups. CONCLUSION： Oxidative stress may be a major mechanism for the toxicity of CCh. MA has a protective effect against CCl4 toxicity by inhibiting the oxidative damage and stimulating GST activities. Thus, clinical application of MA should be considered in cases with carbon tetrachloride-induced injury.

Novel Stilbene Glycosides from Polygonum multiflorum

Two new stilbene glycosides (1 and 2), together with nine known compounds (3-11), were isolated from the water extract of Polygonum multiflorum Thunb. The structures of the new compounds were elucidated by their chemical properties and spectroscopic analyses, including extensive 2D NMR experiments. Compound 2 showed strong DNA cleavage activity, and compounds 1, 2 and 10 (2, 3, 4′, 5_tetrahydroxy_ trans _stilbene_2_O_β_ D _glucopyranoside) exhibited significant inhibition of lipid peroxidation.

Neuroprotective effects of ganoderma lucidum polysaccharides against oxidative stress-induced neuronal apoptosis

Ganoderma lucidum polysaccharides have protective effects against apoptosis in neurons exposed to ischemia/reperfusion injury, but the mechanisms are unclear. The goal of this study was to investigate the underlying mechanisms of the effects of ganoderma lucidum polysaccharides against oxidative stress-induced neuronal apoptosis. Hydrogen peroxide（H_2O_2） was used to induce apoptosis in cultured cerebellar granule cells. In these cells, ganoderma lucidum polysaccharides remarkably suppressed H_2O_2-induced apoptosis, decreased expression of caspase-3, Bax and Bim and increased that of Bcl-2. These findings suggested that ganoderma lucidum polysaccharides regulate expression of apoptosis-associated proteins, inhibit oxidative stress-induced neuronal apoptosis and, therefore, have significant neuroprotective effects.

Mechanism of action of (-)-epigallocatechin-3-gallate:auto-oxidation-dependent activation of extracellular signal-regulated kinase 1/2 in Jurkat cells

AIM:(-)-Epigallocatechin-3-gallate(EGCG), a major compound of tea polyphenols, exhibited antitumor activity in previous studies. In these studies, EGCG usually inhibits EGFR, and impairs the ERK1/2 phosphorylation in tumor cells. The aim was to clarify the mechanism of ERK1/2 activation induced by EGCG. METHODS: Jurkat and 293 T cells were treated with EGCG in different culture conditions. Western Blotting(WB) was employed to analyze ERK1/2 and MEK phosphorylation. Cetuximab and FR180204 were used to inhibit cell signaling. The stability of EGCG was assessed by HPLC. The concentration of hydrogen peroxide generated by the auto-oxidation of EGCG was determined by photocolorimetric analysis. RESULTS: Activation of ERK1/2 was observed to be both time- and dose-dependent. Stimulation of cell signaling was dependent on MEK activity, but independent of EGFR activity. Unexpectedly, EGCG was depleted within one hour of incubation under traditional culture conditions. Auto-oxidation of EGCG generated a high level of hydrogen peroxide in the medium. Addition of catalase and SOD to the acidic medium inhibited the oxidation of EGCG. However, this particular condition also prevented the phosphorylation of ERK1/2. The generation of ROS by hydrogen peroxide may also induce ERK1/2 activation in Jurkat cells. CONCLUSION: ERK1/2 phosphorylation was caused by auto-oxidation of EGCG. Traditional culture conditions were determined to be inappropriate for EGCG research.