Vascular hyporeactivity to vasoconstrictor agents and hemodynamic decompensation in hemorrhagic shock is mediated by nitric oxide.

This study investigates the role of nitric oxide (NO) and the induction of a calcium-independent NO synthase (NOS) in development of vascular hyporeactivity to norepinephrine (NE) and vascular decompensation associated with hemorrhagic shock (HS) in the anesthetized rat. HS for 120 min caused a time-dependent reduction of the pressor responses to NE. This hyporeactivity is mediated by an enhanced release of NO by the constitutive NOS, for it was reversed by NG-nitro-L-arginine methyl ester (NO2Arg), an inhibitor of both constitutive and inducible NOS, but it was not prevented by dexamethasone, an inhibitor of NOS induction. Vascular decompensation following prolonged periods of HS was characterized by a failure of control animals to maintain arterial blood pressures despite reinfusion of blood. This progressive decrease in blood pressure is mediated by enhanced formation of NO by the inducible NOS, for it was prevented by NO2Arg or dexamethasone. A strong increase in calcium-independent (inducible) NOS activity was observed in several organs after 150 and 330 min of HS, being most pronounced in lung, liver, and spleen. HS for 330, but not 150, min also caused hyporeactivity of rat aortic rings to vasoconstrictors, which was associated with induction of calcium-independent NOS activity in this tissue. Aortic hyporeactivity was prevented by dexamethasone pretreatment in vivo and reversed by NO2Arg in vitro. HS was not associated with an increase in plasma endotoxin levels, showing that endotoxin does not account for induction of NOS in this model. Thus, excessive NO formation induces vascular hyporeactivity and decompensation in HS, indicating that NOS inhibitors, particularly of the inducible NOS, may improve the therapeutic outcome of patients suffering from HS.     

氧化应激对人淋巴细胞端粒长度的影响

目的　探讨人外周血淋巴细胞遭受过氧化氢 (H2O2 )损伤时,端粒长度的变化。　方法　体外培养人外周血淋巴细胞,分为正常对照组、氧化组和抗氧化组,然后应用Southern杂交技术检测不同时间端粒长度的变化。　结果　端粒长度随着时间的变化表现为缩短;且 3组之间均有显著差异(P<0 .05)。　结论　氧化应激在一定程度上可以引起人淋巴细胞端粒长度的缩短;维生素C具有一定的抗氧化作用,它能减低过氧化损伤,从而减缓端粒缩短的速率。     

Estrogen improves the hyperdynamic circulation and hyporeactivity of mesenteric arteries by alleviating oxidative stress in partial portal vein ligated rats

AIM:To evaluate the effects of estrogen(E2) on systemic and splanchnic hyperdynamic circulation in portal hypertensive rats.METHODS:Fifty castrated female Sprague-Dawley rats were divided into five groups:sham operation(SO),partial portal vein ligation(PPVL) + placebo(PLAC),PPVL + E2,PPVL + ICI and PPVL + E2 + ICI. Hemodynamic measurements were performed using ultrasonography. Mesenteric arteriole contractility in response to norepinephrine was determined using a vessel perfusion system. Oxidative stress in the mesenteric artery was investigated by in situ detection of the superoxide anion(O2) and hydrogen peroxide(H2O2) concentrations.RESULTS:Treatment with E2 resulted in a significant decrease of portal pressure(P < 0.01) and portal venous inflow(P < 0.05),and higher systemic vascular resistance(P < 0.05) and splanchnic arteriolar resistance(P < 0.01) in PPVL + E2 rats compared to PPVL+ PLAC rats. In the mesenteric arterioles of PPVL +E2 rats,the dose-response curve was shifted left,and the EC50was decreased(P < 0.01). E2 reduced O2 production and H2O2concentration in the mesenteric artery. However,ICI182,780 reversed the beneficial effects of E2,therefore,the systemic and splanchnic hyperdynamic circulation were more deteriorated in ICI182,780-treated rats.CONCLUSION:Treatment with estrogen improved the systemic and splanchnic hyperdynamic circulation in PPVL rats,in part due to the alleviation of oxidative stress.     

金属硫蛋白对氧化应激引起的糖尿病心肌病的保护作用

糖尿病心肌病（DC）发生的氧化应激（OS）学说成为当前研究热点,即高血糖引起的氧化和硝基化促使了DC的发生.金属硫蛋白（MT）是一种广泛存在于真核细胞的抗氧化蛋白,本文对DC的氧化损伤机制及MT的保护作用进行综述.     

Cyclophilin A is a secreted growth factor induced by oxidative stress

Reactive oxygen species have been implicated in the pathogenesis of atherosclerosis, hypertension, and restenosis, in part by promoting vascular smooth muscle cell (VSMC) growth. Many VSMC growth factors are secreted by VSMC and act in an autocrine manner. Here we demonstrate that cyclophilin A (CyPA), a member of the immunophilin family, is secreted by VSMCs in response to oxidative stress and mediates extracellular signal-regulated kinase (ERK1/2) activation and VSMC growth by reactive oxygen species. Human recombinant CyPA can mimic the effects of secreted CyPA to stimulate ERK1/2 and cell growth. The peptidyl-prolyl isomerase activity is required for ERK1/2 activation by CyPA. In vivo, CyPA expression and secretion are increased by oxidative stress and vascular injury. These findings are the first to identify CyPA as a secreted redox-sensitive mediator, establish CyPA as a VSMC growth factor, and suggest an important role for CyPA and enzymes with peptidyl-prolyl isomerase activity in the pathogenesis of vascular diseases.     

Pancreatic B-cell function is altered by oxidative stress induced by acute hyperglycaemia.

AIMS: Type 2 diabetes is preceded by a symptom-free period of impaired glucose tolerance (IGT). Pancreatic B-cell function decreases as glucose intolerance develops. In many patients with IGT, fasting blood glucose is within normal limits and hyperglycaemia occurs only postprandially. We examined whether pancreatic B-cell function changes during acute hyperglycaemia induced by oral glucose loading. METHODS: We calculated the insulinogenic index (I.I.) as an indicator of pancreatic B-cell function and measured serum levels of thioredoxin, a marker of cellular redox state, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative stress, during a 75-g oral glucose tolerance test (OGTT) in 45 subjects [24 patients with normal glucose tolerance (NGT), 14 with IGT and seven with Type 2 diabetes]. RESULTS: Thioredoxin levels decreased after glucose loading [66.1 +/- 23.7, *59.3 +/- 22.4, *49.3 +/- 21.2 and *37.7 +/- 18.0 ng/ml, fasting (0 min) and at 30, 60 and 120 min, respectively; *P < 0.001 vs. fasting]. In contrast, concentrations of 8-OHdG peaked at 30 min and then gradually decreased (0.402 +/- 0.123, *0.440 +/- 0.120, 0.362 +/- 0.119 and 0.355 +/- 0.131 ng/ml, *P < 0.05 vs. fasting, P < 0.01 vs. 30 min). The insulinogenic index correlated with the change in thioredoxin levels (r = 0.34, P < 0.05). However, there was no relationship with the change in 8-OHdG levels from 0 to 30 min. CONCLUSIONS: Hyperglycaemia in response to oral glucose impairs pancreatic B-cell function with decreasing thioredoxin levels. The augmented oxidative stress induced by hyperglycaemia may affect the cellular redox state. These findings strongly suggest that repeated postprandial hyperglycaemia may play an important role in the development and progression of diabetes mellitus.     

高游离脂肪酸血症所致胰岛素抵抗与氧化应激的关系

研究高游离脂肪酸(FFA)血症所致大鼠机体氧化应激及胰岛素抵抗之间的相互关系,以及其对机体抗氧化能力的影响,探讨胰岛素抵抗的病理生理机制.经研究证实大鼠高FFA血症不仅使组织活性氧簇生成增加[(886±105 vs 427±42)mmol/L,P<0.05],同时损伤机体抗氧化能力,细胞内还原捌谷胱甘肽生成减少[(272±47 vs 561±36)μmol/L,P<0.05],导致氧化应激,从而促进胰岛素抵抗的形成.     

Inflammation-induced tumorigenesis in the colon is regulated by caspase-1 and NLRC4

Chronic inflammation is a known risk factor for tumorigenesis, yet the precise mechanism of this association is currently unknown. The inflammasome, a multiprotein complex formed by NOD-like receptor (NLR) family members, has recently been shown to orchestrate multiple innate and adaptive immune responses, yet its potential role in inflammation-induced cancer has been little studied. Using the azoxymethane and dextran sodium sulfate colitis-associated colorectal cancer model, we show that caspase-1-deficient (Casp1(-/-)) mice have enhanced tumor formation. Surprisingly, the role of caspase-1 in tumorigenesis was not through regulation of colonic inflammation, but rather through regulation of colonic epithelial cell proliferation and apoptosis. Consequently, caspase-1-deficient mice demonstrate increased colonic epithelial cell proliferation in early stages of injury-induced tumor formation and reduced apoptosis in advanced tumors. We suggest a model in which the NLRC4 inflammasome is central to colonic inflammation-induced tumor formation through regulation of epithelial cell response to injury.     

Inflammation-induced endothelial dysfunction involves reduced nitric oxide bioavailability and increased oxidant stress

OBJECTIVES: Our aim was to investigate mechanisms of inflammation-induced endothelial dysfunction in humans. METHODS: Endothelial function in twenty-one healthy human volunteers was measured using forearm venous plethysmography before and 8 h after administration of typhoid vaccination to generate an inflammatory response. Basal and stimulated endothelial nitric oxide (NO) bioavailability was assessed by measurement of the responses to intra-arterial N(G)-monomethyl-l-arginine (l-NMMA) and bradykinin, respectively. The effects of supplementation with l-arginine or ascorbic acid were assessed to probe the effects of substrate deficiency and oxidative stress, respectively. Systemic effects were determined by measuring cytokine response, total anti-oxidant status (TAOS) and urinary protein excretion. RESULTS: Vaccination induced a cytokine response, a fall in total anti-oxidant status and increased urinary albumin excretion (UAE). There was a reduction in the response to bradykinin (BK, P<0.005) and l-NMMA (P<0.0001) with no effect on the response to glyceryl trinitrate (GTN) and norepinephrine (NE). Following vaccination blood flow response to BK (but not GTN) was partially returned to pre-vaccine levels by infusion of ascorbic acid (P=0.01). Supplementation with l-arginine had no effect. CONCLUSION: Inflammation causes widespread endothelial dysfunction, reduces vascular NO bioavailability and increases oxidative stress. These actions are partially reversible with local anti-oxidants. These findings suggest a role for reactive oxygen species in inflammation-induced endothelial dysfunction.     

Postprandial oxidative stress is modulated by dietary fat in adipose tissue from elderly people

We have investigated whether dietary fat modifies the postprandial oxidative stress in adipose tissue of elderly people. Twenty participants received three diets for 4 weeks each: SFA-rich diet, Mediterranean (Med) diet enriched in MUFA with virgin olive oil, and a low-fat, high-carbohydrate diet enriched in n-3 PUFA (α-linolenic acid from plant origin) (CHO-PUFA diet). After 12 h of fasting, volunteers received a breakfast reflecting the fatty acid composition of the diet ingested in the preceding dietary period. Med diet induced higher postprandial SOD2 and TrxR mRNA levels, and CHO-PUFA diet induced higher GPx1 and TrxR mRNA levels compared with SFA-rich diet. Med and CHO-PUFA breakfasts induced a postprandial increase in plasma reduced glutathione (GSH), and a greater postprandial GSH/oxidized glutathione ratio compared to the SFA-rich diet. Our study suggests that the consumption of Med and CHO-PUFA diets may reduce postprandial oxidative stress compared to an SFA-rich diet, which may be due to higher antioxidant enzymes gene expression in adipose tissue.     

Role of p47(phox) in vascular oxidative stress and hypertension caused by angiotensin II

Hypertension caused by angiotensin II is dependent on vascular superoxide (O2*-) production. The nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase is a major source of vascular O2*- and is activated by angiotensin II in vitro. However, its role in angiotensin II-induced hypertension in vivo is less clear. In the present studies, we used mice deficient in p47(phox), a cytosolic subunit of the NADPH oxidase, to study the role of this enzyme system in vivo. In vivo, angiotensin II infusion (0.7 mg/kg per day for 7 days) increased systolic blood pressure from 105+/-2 to 151+/-6 mm Hg and increased vascular O2*- formation 2- to 3-fold in wild-type (WT) mice. In contrast, in p47(phox-/-) mice the hypertensive response to angiotensin II infusion (122+/-4 mm Hg; P<0.05) was markedly blunted, and there was no increase of vascular O2*- production. In situ staining for O2*- using dihydroethidium revealed a marked increase of O2*-production in both endothelial and vascular smooth muscle cells of angiotensin II-treated WT mice, but not in those of p47(phox-/-) mice. To directly examine the role of the NAD(P)H oxidase in endothelial production of O2*-, endothelial cells from WT and p47(phox-/-) mice were cultured. Western blotting confirmed the absence of p47(phox) in p47(phox-/-) mice. Angiotensin II increased O2*- production in endothelial cells from WT mice, but not in those from p47(phox-/-) mice, as determined by electron spin resonance spectroscopy. These results suggest a pivotal role of the NAD(P)H oxidase and its subunit p47(phox) in the vascular oxidant stress and the blood pressure response to angiotensin II in vivo.     

Mitochondrial oxidative stress caused by Sod2 deficiency promotes cellular senescence and aging phenotypes in the skin

Cellular senescence arrests the proliferation of mammalian cells at risk for neoplastic transformation, and is also associated with aging. However, the factors that cause cellular senescence during aging are unclear. Excessive reactive oxygen species (ROS) have been shown to cause cellular senescence in culture, and accumulated molecular damage due to mitochondrial ROS has long been thought to drive aging phenotypesin vivo. Here, we test the hypothesis that mitochondrial oxidative stress can promote cellular senescence in vivo and contribute to aging phenotypes in vivo, specifically in the skin. We show that the number of senescent cells, as well as impaired mitochondrial (complex II) activity increase in naturally aged mouse skin. Using a mouse model of genetic Sod2 deficiency, we show that failure to express this important mitochondrial anti-oxidant enzyme also impairs mitochondrial complex II activity, causes nuclear DNA damage, and induces cellular senescence but not apoptosis in the epidermis. Sod2 deficiency also reduced the number of cells and thickness of the epidermis, while increasing terminal differentiation. Our results support the idea that mitochondrial oxidative stress and cellular senescence contribute to aging skin phenotypes in vivo.     

Melatonin protects against oxidative stress caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in the mouse nigrostriatum

We tested the hypothesis that melatonin acts as a powerful hydroxyl radical (*OH) scavenger in vivo in the brain, and interferes with oxidative stress caused by the parkinsonian neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We investigated the effect of melatonin on in vitro *OH production employing a Fenton-like reaction in test tubes, and ex vivo *OH generation in isolated mitochondria induced by 1-methyl-4-phenyl pyridinium (MPP+), as well as on in vivo *OH formation in the mouse striatum following systemic administration of MPTP. We also measured reduced glutathione (GSH) levels, and superoxide dismutase (SOD) activity in the nucleus caudatus putamen (NCP) and substantia nigra (SN), 7 days following MPTP and/or melatonin administration. Melatonin caused a significant and dose-dependent inhibition of the production of *OH in the in vitro, ex vivo and in vivo experimental conditions. Melatonin caused no changes in monoamine oxidase-B activity, in vitro in mitochondrial P2 fractions or in vivo following systemic administration. MPTP treatment in mice caused a significant depletion of GSH, and increased the specific activity of SOD both in SN and NCP on the seventh day. MPTP-induced GSH depletion was dose-dependently blocked in SN and NCP by melatonin. Higher doses of melatonin exhibited a synergistic effect on MPTP-induced increase in the SOD activity in the SN. These results suggest that while GSH inhibition is a direct consequence of *OH generation following neurotoxin administration, the increase in SOD activity is a compensatory mechanism for removing superoxide radicals generated as the result of MPTP. Our results not only point to the potency of melatonin in blocking the primary insults caused by MPTP, but also provide evidence for triggering secondary neuroprotective mechanisms, suggesting its use as a therapeutic agent in neurodegenerative disorders, such as Parkinson's disease.