Hepatocyte susceptibility to glyoxal is dependent on cell thiamin content

Glyoxal, a reactive dicarbonyl, is detoxified primarily by the glyoxalase system utilizing glutathione (GSH) and by the aldo-keto reductase enzymes which utilizes NAD[P]H as the co-factor. Thiamin (Vitamin B(1)) is an essential coenzyme for transketolase (TK) that is part of the pentose phosphate pathway which helps maintain cellular NADPH levels. NADPH plays an intracellular role in regenerating glutathione (GSH) from oxidized GSH (GSSG), thereby increasing the antioxidant defenses of the cell. In this study we have focused on the prevention of glyoxal toxicity by supplementation with thiamin (3mM). Thiamin was cytoprotective and restored NADPH levels, glyoxal detoxification and mitochondrial membrane potential. Hepatocyte reactive oxygen species (ROS) formation, lipid peroxidation and GSH oxidation were decreased. Furthermore, hepatocytes were made thiamin deficient with oxythiamin (3mM) as measured by the decreased hepatocyte TK activity. Under thiamin deficient conditions a non-toxic dose of glyoxal (2mM) became cytotoxic and glyoxal metabolism decreased; while ROS formation, lipid peroxidation and GSH oxidation was increased.     

Protective effect of chelerythrine on gentamicin-induced nephrotoxicity

Despite their beneficial effects, aminoglycosides including gentamicin (GEN) have considerable nephrotoxic side-effects. The toxicity of GEN at the level of the kidney seems to relate to the generation of reactive oxygen species (ROS). ROS have been reported to be involved in the activation of protein kinase C (PKC). The unique structural aspects of PKC cause it to function as a sensor for oxidative stress. It seems likely that the increased NAD(P)H oxidase-derived superoxide (O2) production is at least in part mediated by PKC. We investigated the effects of chelerythrine, a commonly used PKC inhibitor, on GEN-induced changes of renal malondialdehyde (MDA), nitric oxide (NO) generation, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities, glutathione (GSH) content, and serum creatinine (Cr), blood urea nitrogen (BUN) levels. Morphological changes in the kidney were also examined. GEN administration to control rats increased MDA and NO generation but decreased CAT, SOD and GSH-Px activities, and GSH content. Chelerythrine administration with GEN caused significantly decreased MDA, NO generation and increased CAT, SOD and GSH-Px activities, and GSH content when compared with GEN alone. Chelerythrine also significantly decreased serum Cr and BUN levels. Morphological changes in the kidney including tubular necrosis were evaluated qualitatively. Both biochemical findings and histopathological evidence showed that administration of chelerythrine reduced the GEN-induced kidney damage. We propose that chelerythrine acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GEN via the inhibition of a PKC pathway.     

Superoxide-dependence of the short chain sugars-induced mutagenesis

Short chain sugars such as glycolaldehyde are produced at the initial stages of nonenzymatic glycosylation. Because their carbonyl groups cannot be blocked by cyclization, such compounds tautomerize to enediols, which are prone to autoxidation. Superoxide radical serves as an initiator and a propagator of this autoxidation. The biological importance of the involvement of superoxide in sugar autoxidation in vivo was examined using superoxide dismutase (SOD)-deficient and SOD-replete strains of Escherichia coli. Glycolaldehyde, glyceraldehyde, and dihydroxyacetone greatly enhanced the mutation rates in SOD-deficient E. coli. The effect was oxygen-dependent and was suppressed by SOD or by a SOD mimetic. The mutagenic effect of glycolaldehyde coincided with intracellular accumulation of glyoxal, a product of glycolaldehyde autoxidation.     

Comparison between the effects of normoxia and hypoxia on antioxidant enzymes and glutathione redox state in ex vivo culture of CD34(+) cells

Hypoxia maintained biological characteristics of CD34(+) cells through keeping lower intracellular reactive oxygen specials (ROS) levels. The effects of normoxia and hypoxia on antioxidant enzymes and glutathione redox state were compared in this study. Hypoxia decreased the mRNA expression of both catalase (CAT) and glutathione peroxidase (GPX), but not affected mRNAs expression of superoxide dismutase (SOD). While the cellular GPX activities under hypoxia were apparently less than those under normoxia, neither SOD activities nor CAT activities were affected by hypoxia. The analysis of glutathione redox status and ROS products showed the lower oxidized glutathione (GSSG) levels, the higher reduced glutathione (GSH) levels, the higher GSH/GSSG ratios, and the less O(2)- and H(2)O(2) generation under hypoxia (versus normoxia). Meanwhile more primary CD34(+)CD38(-) cells were obtained when cultivation was performed under hypoxia or with N-acetyl cysteine (the precursor of GSH) under normoxia. These results demonstrated the different responses of anti-oxidative mechanism between normoxia and hypoxia. Additionally, the present study suggested that the GSH-GPX antioxidant system played an important role in HSPCs preservation by reducing peroxidation.     

夜间低温胁迫对番茄叶片活性氧代谢及AsA-GSH循环的影响

以番茄品种‘辽园多丽’为试材,利用人工气候室模拟设施生产中的夜间低温胁迫环境,研究9℃和6℃夜低温对番茄叶片活性氧代谢和AsA-GSH循环的影响。结果显示:9℃和6℃夜间低温胁迫3～9d可诱导番茄叶片中超氧阴离子(O2.-)产生速率、过氧化氢(H2O2)和丙二醛(MDA)含量上升;抑制过氧化物酶(POD)、过氧化氢酶(CAT)的活性,增加超氧化物歧化酶(SOD)和AsA-GSH循环中抗坏血酸过氧化物酶(APX)、脱氢抗坏血酸还原酶(DHAR)、谷胱甘肽还原酶(GR)的活性,并提高还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)、氧化型谷胱甘肽(GSSG)的含量。研究表明,在夜间低温胁迫过程中,增加的番茄叶片中SOD活性和AsA-GSH循环清除活性氧的能力并未与氧还原的速率一致,从而导致番茄叶片中活性氧的累积,使细胞膜系统受到一定破坏,在6℃处理的植物中尤为明显。     

Reduction in molecular synthesis or enzyme activity of superoxide dismutases and catalase contributes to oxidative stress and neurogenic hypertension in spontaneously hypertensive rats

A balance between production and elimination of reactive oxygen species such as superoxide anion (O2*-) and hydrogen peroxide (H2O2) tightly regulates the homeostasis of cellular oxidative stress, which contributes to a variety of cardiovascular diseases, including hypertension. The present study assessed the hypothesis that O2*- or H2O2 levels augmented by the reduced molecular synthesis or enzyme activity of superoxide dismutase (SOD), catalase (CAT), or glutathione peroxidase (GPx) in the rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons that generate tonic vasomotor tone are located, contribute to the pathogenesis of hypertension. We found that copper/zinc SOD (SOD1), manganese SOD (SOD2), or CAT, but not GPx, mRNA or protein expression and enzyme activity in the RVLM of spontaneously hypertensive rats (SHR) were significantly lower than those in normotensive Wistar-Kyoto (WKY) rats, along with a significantly higher level of O2*- or H2O2. A causative relationship between these biochemical correlates of oxidative stress and neurogenic hypertension was established when gene transfer by microinjection of adenovirus encoding SOD1, SOD2, or CAT into the bilateral RVLM promoted a long-lasting reduction in arterial pressure in SHR, but not WKY rats, accompanied by an enhanced SOD1, SOD2, or CAT protein expression or enzyme activity and reduced O2*- or H2O2 level in the RVLM. These results together suggest that downregulation of gene expression and enzyme activity of the antioxidant SOD1, SOD2, or CAT may underlie the augmented levels of O2*- and H2O2 in the RVLM, leading to oxidative stress and hypertension in SHR.     

Induction of oxidative stress and DNA damage in cervix in acute treatment with benzo[a]pyrene

Benzo[a]pyrene [B(a)P] is one of the most prevalent environmental carcinogens and genotoxic agents. However, the mechanisms of B(a)P-induced oxidative damage in cervical tissue are still not clear. The present study was to investigate the oxidative stress and DNA damage in cervix of ICR female mice induced by acute treatment with B(a)P. Oxidative stress was assayed by analysis of malondialdehyde (MDA), superoxide anion and H(2)O(2), and antioxidant enzymes. The alkaline single-cell electrophoresis (SCGE) was used to measure DNA damage. The contents of MDA and glutathione (GSH), and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) were significantly increased in cervix 24, 48 and 72h after B(a)P treatment of a single dose of 12.5 and 25mg/kg, while GSH, CAT, SOD and GST had no significant difference with the dose of 50mg/kg B(a)P at post-treatment time 48 and 72h except for SOD activity at 48h which was significant. The maximum values of SOD, CAT, GST and GSH were peaked at 24h and then decreased gradually while GPx activities and MDA levels persisted for up to 72h. Superoxide anion, H(2)O(2) and DNA damage changed similarly as the activity of SOD, CAT or GST. Additionally, increases of formamidopyrimidine DNA glycosylase (FPG) specific DNA damage were observed and can be greatly rescued by vitamin C pretreatment. Overall, B(a)P demonstrated a time- and dose- related oxidative stress and DNA damage in cervix.     

Intracellular GSH level is a factor in As4.1 juxtaglomerular cell death by arsenic trioxide

Arsenic trioxide has been known to regulate many biological functions such as cell proliferation, apoptosis, differentiation, and angiogenesis in various cell lines. We investigated the involvement of GSH and ROS such as H(2)O(2) and O(2)(*-) in the death of As4.1 cells by arsenic trioxide. The intracellular ROS levels were changed depending on the concentration and length of incubation with arsenic trioxide. The intracellular O(2)(*-) level was significantly increased at all the concentrations tested. Arsenic trioxide reduced the intracellular GSH content. Treatment of Tiron, ROS scavenger decreased the levels of ROS in 10 microM arsenic trioxide-treated cells. Another ROS scavenger, Tempol did not decrease ROS levels in arsenic trioxide-treated cells, but slightly recovered the depleted GSH content and reduced the level of apoptosis in these cells. Exogenous SOD and catalase did not reduce the level of ROS, but did decrease the level of O(2)(*-). Both of them inhibited GSH depletion and apoptosis in arsenic trioxide-treated cells. In addition, ROS scavengers, SOD and catalase did not alter the accumulation of cells in the S phase induced by arsenic trioxide. Furthermore, JNK inhibitor rescued some cells from arsenic trioxide-induced apoptosis, and this inhibitor decreased the levels of O(2)(*-) and reduced the GSH depletion in these cells. In summary, we have demonstrated that arsenic trioxide potently generates ROS, especially O(2)(*-), in As4.1 juxtaglomerular cells, and Tempol, SOD, catalase, and JNK inhibitor partially rescued cells from arsenic trioxide-induced apoptosis through the up-regulation of intracellular GSH levels.     

The effect of melatonin on antioxidant enzymes in human diabetic skin fibroblasts

Melatonin plays several important physiological functions in mammals, such as immune enhancement and regulation of dark-light signal transduction. Melatonin is also known to be an endogenous free radical scavenger and an efficient antioxidant. It detoxifies a variety of free radicals and reactive oxygen intermediates, including the hydroxyl radical, singlet oxygen and nitric oxide. These radicals participate in many diseases, for example diabetes. This study determined the effect of melatonin on the antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), and the level of glutathione (GSH) in human diabetic (C2 line) skin fibroblasts. Confluent monolayers of control (S2 line) and diabetic (C2 line) skin fibroblasts were incubated with different concentrations of melatonin: 10, 50, 100 and 1000 micromol/l at 37 degrees C for 24 h. Next, the GSH level and SOD, CAT and GPx activities were measured colorimetrically. The activities of the antioxidant enzymes and the GSH level were lower in diabetic skin fibroblasts than in the control S2 line. Concentrations of melatonin of 100 and 1000 micromol/l caused a significant increase in the enzymes' activities and GSH level.     

Oxidants,antioxidants and carcinogenesis

Reactive oxygen metabolites (ROMs), such as superoxide anions (O2*-) hydrogen peroxide (H2O2), and hydroxyl radical (*OH), malondialdehyde (MDA) and nitric oxide (NO) are directly or indirectly involved in multistage process of carcinogenesis. They are mainly involved in DNA damage leading sometimes to mutations in tumour suppressor genes. They also act as initiator and/or promotor in carcinogenesis. Some of them are mutagenic in mammalian systems. O2*-, H2O2 and *OH are reported to be involved in higher frequencies of sister chromatid exchanges (SCEs) and chromosome breaks and gaps (CBGs). MDA, a bi-product of lipid peroxidation (LPO), is said to be involved in DNA adduct formations, which are believed to be responsible for carcinogenesis. NO, on the other hand, plays a duel role in cancer. At high concentration it kills tumour cells, but at low concentration it promotes tumour growth and metastasis. It causes DNA single and double strand breaks. The metabolites of NO such as peroxynitrite (OONO-) is a potent mutagen that can induce transversion mutations. NO can stimulate O2*-/H2O2/*OH-induced LPO. These deleterious actions of oxidants can be countered by antioxidant defence system in humans. There are first line defense antioxidants such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT). SOD converts O2*- to H2O2, which is further converted to H2O with the help of GPx and CAT. SOD inhibits *OH production. SOD also act as antipoliferative agent, anticarcinogens, and inhibitor at initiation and promotion/transformation stage in carcinogenesis. GPx is another antioxidative enzyme which catalyses to convert H2O2, to H2O. The most potent enzyme is CAT. GPx and CAT are important in the inactivation of many environmental mutagens. CAT is also found to reduce the SCE levels and chromosomal aberrations. Antioxidative vitamins such as vitamin A, E, and C have a number of biological activities such as immune stimulation, inhibition of nitrosamine formation and an alteration of metabolic activations of carcinogens. They can prevent genetic changes by inhibiting DNA damage induced by the ROMs. Therefore, these antioxidants may be helpful in the treatment of human cancer. However, detailed studies are required to draw a definite conclusion.     

Accumulation of Superoxide Radical in Corn Leaves During Waterlogging

The changes in superoxide (O2-) production, hydrogen peroxide (H2O2) content and active oxygen scavenging system in corn (Zea mays L. ) leaves under waterlogging stress were investigated to explore the relationship between O2- accumulation and waterlogging injury. Corn plants were grown in pots in a controlled environment. The results showed that prolonged waterlogging treatment conducted at 4-leaf stage caused a significant increase in the production of O2- and H2O2, while the extent of O2- change was more than that of H2O2. Malondialdehyde (MDA) accumulation, chlorophyll loss and electrolye leakage were positively correlated with O2- production in corn waterlogged leaves. Foliage spraying with 0. 1 mmol/L paraquat (02- producer) at the start of waterlogging treatment led to a significant increase in 02-, H202 and MDA levels. The addition of DDTC (SOD activity inhibitor) aggravated 02- formation in waterlogged leaves. Waterlogging apperantly reduced the activities of SOD. catalase (CAT), ascorbate peroxidase (AP) and the concentrations of ascorbic acid (ASA) and glutathione (GSH). It was noted that the decline in SOD activity proceeded the diminishment of H2O2 scavengers in chloroplasts (i. e. AP, AsA and GSH). The present findings suggest that O2- is involved in waterlogging damage, and excessive accumulation of 02- is due to the reduced SOD activity.     

A comparison of chemical systems for luminometric determination of antioxidant capacity towards individual reactive oxygen species.

The aim of the study was to investigate the reactive oxygen species (ROS) production in the hypoxanthine-xanthinoxidase (HX-XO), hydrogen peroxide-ferrous sulphate (H2O2-FeSO4) and hydrogen peroxide (H2O2) systems by using various concentrations of ROS scavengers, such as superoxide dismutase (SOD), dimethylthiourea (DMTU) or catalase (CAT). Luminol (0.8 mmol/L) was dissolved in a borate buffer, pH 9.0, and was used as a luminophor in the chemiluminescence (CL) measurements. In the HX-XO system SOD, CAT and DMTU deepened the CL signal, whereas in the H2O2-FeSO4 system, only CAT and DMTU deepened the CL signal, and in the H2O2 system SOD and CAT increased and DMTU deepened the CL signal. Electron spin resonance (ESR) measurements were performed only in the H2O2-FeSO4 system. 5,5-dimethyl-pyrroline-N-oxide (DMPO) was used as a spin trap. According to typical ESR spectra, .OH was produced in this chemical system. It can be concluded that the chemical systems do not produce single reactive oxygen species but a mixture of them.     

Regulation of reactive oxygen species by nerve growth factor but not Bcl-2 as a novel mechanism of protection of PC12 cells from superoxide anion-induced death

Although neurotrophins protect PC12 cells and neurons from oxidative stress-induced death, the molecular mechanism of this effect is largely unknown. Xanthine (XA)+xanthine oxidase (XO) increased the production of the superoxide anion (O2-) and hydrogen peroxide (H2O2), and the death of PC12 cells. Catalase but not superoxide dismutase (SOD) nor a NO scavenger protected PC12 cells from death, indicating that H2O2 is the main effector responsible for this cell death. Both nerve growth factor (NGF) and Bcl-2 protected PC12 cells from O2--induced toxicity. NGF enhanced the production of O2- and suppressed that of H2O2, suggesting that it inhibits the conversion of O2- to H2O2, while Bcl-2 had no such effect. These results suggested that NGF protected the cells from oxidative stress by altering the composition of the reactive oxygen species (ROS) without affecting their total level.     

Sesamol exhibits antimutagenic activity against oxygen species mediated mutagenicity

The effects of sesamol, a phenolic compound responsible for the high resistance of sesame oil to oxidative deterioration as compared with other vegetable oils, have been investigated after mutagen treatment in various strains of Salmonella typhimurium. Sesamol was shown to exhibit strong antimutagenic effects in the Ames tester strains TA100 and TA102. The TA102 strain has been shown to be highly sensitive to reactive oxygen species. Mutagenicity was induced by the generation of oxygen radicals by tert-butylhydroperoxide (t-BOOH) or hydrogen peroxide (H(2)O(2)); therefore, the antimutagenic property of sesamol was attributed to its antioxidant properties. The superoxide and hydroxyl radical scavenging capabilities have further been elucidated using in vitro test systems. It was further shown to have a desmutagenic effect on t-BOOH-induced mutagenesis in TA102 strain. Sesamol also inhibited the mutagenicity of sodium azide (Na-azide) in TA100 tester strain while it had no effect on nitroquinoline-N-oxide (NQNO)-induced mutagenesis in TA98 strain of Salmonella typhimurium. Since active oxygen species are involved in multiple stage processes of carcinogenicity, this compound may also exhibit anticarcinogenic properties.     

Changes in oxidative balance in rat pericytes exposed to diabetic conditions

Recent data indicate that the oxidative stress plays an important role in the pathogenesis of diabetes and its complications such as retinopathy, nephropathy and accelerated atherosclerosis. In diabetic retinopathy, it was demonstrated a selective loss of pericytes accompanied by capillary basement membrane thickening, increased permeability and neovascularization. This study was designed to investigate the role of diabetic conditions such as high glucose, AGE-Lysine, and angiotensin II in the modulation of antioxidant enzymes activities, glutathione level and reactive oxygen species (ROS) production in pericytes. The activity of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and total glutathione (GSH) was measured spectrophotometrically. The production of ROS was detected by spectrofluorimetry and fluorescence microscopy after loading the cells with 2'-7' dichlorofluoresceine diacetate; as positive control H2O2 was used. Intracellular calcium was determined using Fura 2 AM assay. The results showed that the cells cultured in high glucose alone, do not exhibit major changes in the antioxidant enzyme activities. The presence of AGE-Lys or Ang II induced the increase of SOD activity. Their combination decreased significantly GPx activity and GSH level. A three times increase in ROS production and a significant impairment of intracellular calcium homeostasis was detected in cells cultured in the presence of the three pro-diabetic agents used. In conclusion, our data indicate that diabetic conditions induce in pericytes: (i) an increase of ROS and SOD activity, (ii) a decrease in GPx activity and GSH level, (iii) a major perturbation of the intracellular calcium homeostasis. The data may explain the structural and functional abnormalities of pericytes characteristic for diabetic retinopathy.     

Glutathione regulates transforming growth factor-beta-stimulated collagen production in fibroblasts

Transforming growth factor-beta (TGF-beta) is a potent fibrogenic cytokine. The molecular mechanism underlying TGF-beta fibrogenesis, however, has not been completely elucidated. In this study, we showed that TGF beta decreased the intracellular GSH content in murine embryo fibroblasts (NIH 3T3), which was followed by an increase in collagen I mRNA content and collagen protein production. Prevention of GSH depletion with N-acetylcysteine (NAC), GSH, or GSH ester abrogated TGF-beta-stimulated collagen production, whereas a decrease in intracellular GSH content with L-buthionine-S,R-sulfoximine, an inhibitor of de novo GSH synthesis, enhanced TGF-beta-stimulated collagen production. These results suggest that GSH depletion induced by TGF-beta may mediate TGF-beta-stimulated collagen production. In addition, we showed that TGF-beta stimulated superoxide production and increased release of H2O2 from the cells, whereas GSH ester decreased basal and TGF-beta + glucose oxidase-stimulated H2O2 release. H2O2, exogenously added or continuously generated by glucose oxidase, enhanced TGF-beta-stimulated collagen production, whereas suppression of superoxide production by diphenyliodonium, an NAD(P)H oxidase inhibitor, blocked TGF-beta-stimulated collagen production. These data further suggest that reactive oxygen species are involved in TGF-beta-stimulated collagen production and that the effect of GSH depletion on TGF-beta-stimulated collagen production may be mediated by facilitating reactive oxygen species signaling.     

Effect of brahma rasayana on antioxidant system after radiation

Oral administration of brahma rasayana (BR; 50 mg/animal for 10 and 30 days) significantly increased the liver antioxidant enzymes such as superoxide dismutase (SOD), catalase(CAT) and tissue and serum levels of reduced glutathione (GSH). Whole body irradiation suppressed the levels of SOD, CAT and GSH. Reduced activity of SOD, CAT and GSH was significantly elevated by treatment with BR after radiation treatment. Similarly radiation exposure induced increase in serum and liver lipid peroxides was significantly reduced by further treatment with BR. The results indicate that BR could ameliorate the oxidative damage produced in the body by radiation and may be useful as an adjuvant during radiation therapy.     

黄连素预处理对6-羟基多巴胺所致PC12细胞损伤的影响

目的:观察黄连素(Berberine,BBR)预处理对6-羟基多巴胺(6-hydroxydopamine,6-OHDA)诱导的PC12细胞的影响,并探讨二型超氧化物歧化酶(Mn-SOD,SOD2)是否介导了BBR的保护作用。方法:将PC12细胞分为5组,分别为正常培养的对照组(Control)、25μM的6-OHDA损伤组、1μM的BBR预处理24 h组(BBR+6-OHDA)、SOD2-siRNA干扰组(SOD2-siRNA+BBR+6-OHDA)和乱序siRNA处理组(SC-siRNA+BBR+6-OHDA),孵育24 h后,采用噻唑蓝法(Methylthiazolyldiphenyl-tetrazolium bromide,MTT)检测细胞活力,试剂盒检测培养基乳酸脱氢酶(Lactic Dehydrogenase,LDH)、细胞内活性氧(Reactive Oxygen Species,ROS)、还原型谷胱甘肽(Glutathione,GSH)和过氧化氢酶(Catalase,CAT)的含量,使用流式细胞仪检测凋亡率,Western blot检测SOD2和凋亡蛋白Cleaved caspase-3的表达。结果:与Control组相比,6-OHDA诱导PC12细胞24 h后,细胞活力显著降低,SOD2表达、GSH和CAT的含量明显减少,培养基上清液LDH活力、细胞凋亡率、Cleaved caspase-3表达和ROS水平显著增加(P<0.05),而BBR预处理可显著恢复6-OHDA诱导的PC12细胞活力、SOD2表达、GSH和CAT水平,并降低细胞凋亡率、凋亡蛋白表达和细胞ROS水平(P<0.05),而SOD2-siRNA显著逆转了BBR预处理产生的上述保护作用(P<0.05),SC-siRNA则未对BBR预处理产生的上述作用造成明显影响(P>0.05)。结论:黄连素预处理可减轻6-OHDA诱导的PC12细胞损伤,而SOD2分子介导了BBR预处理对暴露于6-OHDA的PC12细胞的保护作用。     

Protective effect of butin against hydrogen peroxide-induced apoptosis by scavenging reactive oxygen species and activating antioxidant enzymes

The antioxidant property of butin was investigated for cytoprotective effect against H(2)O(2)-induced cell damage. This compound showed intracellular reactive oxygen species (ROS) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, inhibition of lipid peroxidation, and DNA damage. This radical scavenging activity of butin protected cell damage exposed to H(2)O(2). Also, butin reduced the apoptotic cells induced by H(2)O(2), as demonstrated by the decreased DNA fragmentation, apoptotic body formation, and caspase 3 activity. In addition, butin restored the activity and protein expression of cellular antioxidant enzymes, superoxide dismutase (SOD), and catalase (CAT) in H(2)O(2)-treated cells. Taken together, these findings suggest that butin protected cells against H(2)O(2)-induced cell damage via antioxidant property.     

Mechanisms of mutagenicity and toxicity of sodium selenite (Na2SeO3) in Salmonella typhimurium

The mechanisms of selenite toxicity and mutagenicity in S. typhimurium have been characterized. In contrast to previous reports, selenite toxicity was shown not to involve nonspecific incorporation into protein via the sulfur metabolic pathways. Selenite toxicity was, however, shown to involve its ability to act as an oxidizing agent, primarily through reactions with sulfhydryls. Strains which lack glutathione (GSH) are more sensitive to killing by sulfhydryl reagents. The selenite sensitivity of such a mutant was a biphasic phenomenon. The mutant was much more sensitive than a strain which contained GSH at lower selenite concentrations whereas, at higher concentrations, the mutant was much more resistant to selenite. The mechanism of selenite toxicity at lower concentrations in this mutant thus appeared to involve damage to intracellular sulfhydryls. The sensitization to higher doses of selenite by GSH could be explained by the generation of toxic oxygen species. The in vitro reactions of selenite with both cysteine and GSH readily produced H2O2 and O2-. A S. typhimurium strain which overproduces superoxide dismutase (SOD) and catalase was more resistant to high concentrations of selenite, but not killing by the lower doses. Pretreatment of cells with a nonlethal dose of selenite induced the synthesis of proteins which protected the cells from killing by H2O2 or high doses of selenite. Selenite was also a mutagen in the tester strain TA104, in which a number of other oxidizing agents have also been found to be mutagens. These results were consistent with a model in which the reactions of selenite and intracellular thiols with concomitant production of active oxygen species are the primary causal agents of selenite mutagenicity and toxicity in S. typhimurium.