Antioxidant activities of various extracts of lotus (Nelumbo nuficera Gaertn) rhizome.
(49/170)Lotus rhizome powder was extracted with solvents of different polarities. Antioxidant activities of the extracts were evaluated by a 2, 2'-diphenylpicrylhydrazyl (DPPH) assay and a beta-carotene bleaching assay, and compared with that of butylated hydroxyanisole (BHA) and ascorbic acid. Methanol showed the highest extract yield among all of solvents. Although acetone extract had the highest total phenolics content, methanol extract had the highest total phenolics recovery from lotus powder (20.1 mg catechin equivalents/100g lotus powder). Extract of either methanol or acetone demonstrated the highest DPPH scavenging activity at both 66.7 mg/L and 133.3 mg/L. All extracts exhibited higher antioxidant activity coefficient (AAC) than that of ascorbic acid, furthermore, dichloromethane and petroleum extracts had comparable AAC with BHA by the beta-carotene bleaching assay. The properties of the extracting solvents significantly affected the yield, total phenolics content and antioxidant activity of lotus rhizome extracts. (+info)
Hydrogen sulfide induces direct radical-associated DNA damage.
(50/170)Hydrogen sulfide (H(2)S) is produced by indigenous sulfate-reducing bacteria in the large intestine and represents an environmental insult to the colonic epithelium. Clinical studies have linked the presence of either sulfate-reducing bacteria or H(2)S in the colon with chronic disorders such as ulcerative colitis and colorectal cancer, although at this point, the evidence is circumstantial and underlying mechanisms remain undefined. We showed previously that sulfide at concentrations similar to those found in the human colon induced genomic DNA damage in mammalian cells. The present study addressed the nature of the DNA damage by determining if sulfide is directly genotoxic or if genotoxicity requires cellular metabolism. We also questioned if sulfide genotoxicity is mediated by free radicals and if DNA base oxidation is involved. Naked nuclei from untreated Chinese hamster ovary cells were treated with sulfide; DNA damage was induced by concentrations as low as 1 micromol/L. This damage was effectively quenched by cotreatment with butylhydroxyanisole. Furthermore, sulfide treatment increased the number of oxidized bases recognized by formamidopyrimidine [fapy]-DNA glycosylase. These results confirm the genotoxicity of sulfide and strongly implicate that this genotoxicity is mediated by free radicals. These observations highlight the possible role of sulfide as an environmental insult that, given a predisposing genetic background, may lead to genomic instability or the cumulative mutations characteristic of colorectal cancer. (+info)
TNF-induced activation of the Nox1 NADPH oxidase and its role in the induction of necrotic cell death.
(51/170)Tumor necrosis factor (TNF) is an important cytokine in immunity and inflammation and induces many cellular responses, including apoptosis and necrosis. TNF signaling enables the generation of superoxide in phagocytic and vascular cells through the activation of the NADPH oxidase Nox2/gp91. Here we show that TNF also activates the Nox1 NADPH oxidase in mouse fibroblasts when cells undergo necrosis. TNF treatment induces the formation of a signaling complex containing TRADD, RIP1, Nox1, and the small GTPase Rac1. TNF-treated RIP1-deficient fibroblasts fail to form such a complex, indicating that RIP1 is essential for Nox1 recruitment. Moreover, the prevention of TNF-induced superoxide generation with dominant-negative mutants of TRADD or Rac1, as well as knockdown of Nox1 using siRNA, inhibits necrosis. Thus our study suggests that activation of Nox1 through forming a complex with TNF signaling components plays a key role in TNF-induced necrotic cell death. (+info)
NADPH oxidases: new players in TNF-induced necrotic cell death.
(52/170)Necrosis is a caspase-independent cell death process involving the generation of reactive oxygen species (ROS). In a recent issue of Molecular Cell, Kim et al. (2007) reported on a novel TNF receptor 1 necrotic signaling complex inducing TRADD- and RIP1-dependent recruitment and activation of the ROS-generating Nox1 NADPH oxidase complex. (+info)
Endrin-induced histopathological changes and lipid peroxidation in livers and kidneys of rats, mice, guinea pigs and hamsters.
(53/170)Endrin toxicity may be due to an oxidative stress associated with increased lipid peroxidation, decreased glutathione content, and inhibition of glutathione peroxidase activity. Extensive interspecies variability exists in sensitivity towards endrin. Therefore, histopathological changes and lipid peroxidation in the livers and kidneys of rats, mice, hamsters, and guinea pigs were examined 24 hr after the administration of 4 mg endrin/kg body weight orally in corn oil. Degeneration and necrotic changes with inflammatory cell infiltration were observed in livers and kidneys, and interspecies variability occurred. Fatty changes in the form of hepatic foam cells with cytoplasmic vacuolation were present. Lipofuscin pigments, associated with lipid peroxidation, were observed in hepatocytes and Kupffer cells. These histopathological conditions were prevented in rats which had been pretreated with butylated hydroxyanisole, vitamins E and C, or cysteine, antioxidants and free radical scavengers which have previously been shown to inhibit lipid peroxidation. The extent of endrin-induced lipid peroxidation correlated well with the degree of histopathological changes. Thus, histological changes consistent with the induction of an oxidative stress were observed following the administration of endrin to various animal species. (+info)
Markers of electrophilic stress caused by chemically reactive metabolites in human hepatocytes.
Molecular characterization of Helicobacter pylori VacA induction of IL-8 in U937 cells reveals a prominent role for p38MAPK in activating transcription factor-2, cAMP response element binding protein, and NF-kappaB activation.
(55/170)Helicobacter pylori VacA induces multiple effects on susceptible cells, including vacuolation, mitochondrial damage, inhibition of cell growth, and enhanced cyclooxygenase-2 expression. To assess the ability of H. pylori to modulate the production of inflammatory mediators, we examined the mechanisms by which VacA enhanced IL-8 production by promonocytic U937 cells, which demonstrated the greatest VacA-induced IL-8 release of the cells tested. Inhibitors of p38 MAPK (SB203580), ERK1/2 (PD98059), IkappaBalpha ((E)-3-(4-methylphenylsulfonyl)-2-propenenitrile), Ca(2+) entry (SKF96365), and intracellular Ca(2+) channels (dantrolene) blocked VacA-induced IL-8 production. Furthermore, an intracellular Ca(2+) chelator (BAPTA-AM), which inhibited VacA-activated p38 MAPK, caused a dose-dependent reduction in VacA-induced IL-8 secretion by U937 cells, implying a role for intracellular Ca(2+) in mediating activation of MAPK and the canonical NF-kappaB pathway. VacA stimulated translocation of NF-kappaBp65 to the nucleus, consistent with enhancement of IL-8 expression by activation of the NF-kappaB pathway. In addition, small interfering RNA of activating transcription factor (ATF)-2 or CREB, which is a p38MAPK substrate and binds to the AP-1 site of the IL-8 promoter, inhibited VacA-induced IL-8 production. VacA activated an IL-8 promoter containing an NF-IL-6 site, but not a mutated AP-1 or NF-kappaB site, suggesting direct involvement of the ATF-2/CREB binding region or NF-kappaB-binding regions in VacA-induced IL-8 promoter activation. Thus, in U937 cells, VacA directly increases IL-8 production by activation of the p38 MAPK via intracellular Ca(2+) release, leading to activation of the transcription factors, ATF-2, CREB, and NF-kappaB. (+info)
Combined ascorbic acid and sodium nitrite treatment induces oxidative DNA damage-associated mutagenicity in vitro, but lacks initiation activity in rat forestomach epithelium.