Antioxidant enzymes and effects of tempol on the development of hypertension induced by nitric oxide inhibition

BACKGROUND: This study analyzed whether hypertension induced by N(omega)-nitro-l-arginine methyl ester (L-NAME) is associated with dysregulation of the main antioxidant enzymes (superoxide dismutase [SOD], catalase, glutathione peroxidase [GPX], and glutathione reductase [GR]) and whether chronic administration of tempol ameliorates this hypertension. METHODS: Four groups of male Wistar rats were used: 1) control rats; 2) rats treated with L-NAME (35 mg/100 mL in drinking fluid); 3) rats treated with tempol (18 mg/100 mL in drinking fluid); and 4) rats treated with L-NAME plus tempol. All treatments were maintained for 6 weeks. Body weight, systolic blood pressure (BP) determined by the tail-cuff method, and heart rate were measured once per week. At the end of the experimental period, direct BP and morphologic, metabolic, plasma, and renal variables were measured. Enzymatic activities were measured in the kidney (cortex and medulla) and heart (right and left ventricles). RESULTS: Rats with L-NAME-induced hypertension showed increased copper-zinc (Cu-Zn) SOD activity in the renal cortex and medulla and the left and right ventricles, which was reduced by tempol administration. The manganese (Mn) SOD activity was increased by L-NAME and reduced by tempol in the renal cortex but was unchanged in other tissues. Catalase activity was not affected by L-NAME or tempol treatments in any tissue. Both GPX and GR activities were increased by L-NAME and reduced by tempol in the renal cortex and medulla but were not affected in the ventricles. Tempol reduced BP and total urinary excretion of 8-hydroxy-2'-deoxyguanosine in L-NAME-treated animals but did not affect either variable in controls. CONCLUSIONS: We conclude that L-NAME-induced hypertension is associated with an upregulation of antioxidant SOD, GPX, and GR activities. Moreover, the results indicate that tempol attenuates hypertension on nitric oxide-deficient rats and that oxidative stress participates in the established phase of this type of hypertension.     

Tempol对过氧化氢致RAW264.7巨噬细胞氧化损伤的保护作用

目的:研究4-羟基-2,2,6,6-四甲基哌啶(Tempol)对过氧化氢(H_2O_2)引起的RAW264.7巨噬细胞氧化损伤的影响。方法:建立H_2O_2诱导的RAW264.7巨噬细胞氧化损伤模型,分为空白对照组、H_2O_2损伤组(0.2 mmol/L H_2O_2)、低剂量Tempol组(0.2 mmol/L H_2O_2+0.4 mmol/L Tempol)和高剂量Tempol组(0.2 mmol/L H_2O_2+0.8mmol/L Tempol),测定每组细胞培养上清液中丙二醛(MDA)含量、超氧化物歧化酶(SOD)和乳酸脱氢酶(LDH)活性。结果:与空白对照组相比,H_2O_2损伤组培养上清中MDA含量和LDH活性显著升高,SOD活性显著降低(P均0.05)。与H_2O_2损伤组相比,低剂量Tempol组与高剂量Tempol组细胞培养上清中MDA的含量[(7.27±0.35)nmol/mL和(7.27±0.26)nmol/mL对(9.55±0.31)nmol/mL,P均0.05]和LDH的活性[(509.36±38.73)U/L和(492.81±40.36)U/L对(706.24±48.46)U/L,P均0.05]均显著降低,而SOD的活性[(24.84±0.54)U/mL和(24.84±0.28)U/mL对(21.16±0.61)U/mL,P均0.05]均显著升高。低剂量Tempol组和高剂量Tempol组MDA含量、SOD和LDH活性无明显差异,Tempol的作用不呈剂量依赖性。结论:Tempol可能通过调节细胞氧化还原系统,对H_2O_2引起的RAW264.7氧化损伤起到保护作用。     

Acceleration of diabetic renal injury in the superoxide dismutase knockout mouse: effects of tempol

Indices of renal injury and oxidative stress were examined in mice with deficiency of cytosolic Cu(2+)/Zn(2+) superoxide dismutase (SOD1-/-, KO) and their wild-type (WT) littermates with streptozotocin-induced diabetes. After 5 weeks of diabetes, KO diabetic (D) but not WT-D mice developed marked albuminuria, increases in glomerular content of transforming growth factor beta, collagen alpha1(IV), and nitrotyrosine, and higher glomerular superoxide compared with corresponding values in nondiabetics. After 5 months of diabetes, increases in these parameters, mesangial matrix expansion, renal cortical malondialdehyde content, and severity of tubulointerstitial injury were all significantly greater, whereas cortical glutathione was lower, in KO-D than in WT-D. In contrast to WT-D, after 4 weeks of diabetes, KO-D mice did not develop the increase in inulin clearance (C(In)) characteristic of early diabetes. The nitric oxide synthase inhibitor N(omega)-nitro-l-arginine methylester suppressed C(In) in WT-D, but had no effect on C(In) in KO-D. Treatment of KO-D with the SOD mimetic tempol for 4 weeks suppressed albuminuria, increases in glomerular transforming growth factor beta, collagen alpha1(IV), nitrotyrosine, and glomerular superoxide, and concurrently increased C(In). The latter action of tempol in KO-D was blocked by the N(omega)-nitro-l-arginine methylester. The findings provide support for a role for superoxide and its metabolism by SOD1 in the pathogenesis of renal injury in diabetes in vivo, and implicate increased interaction of superoxide with nitric oxide as a pathogenetic factor.     

Acute effects of the superoxide dismutase mimetic tempol on split kidney function in two-kidney one-clip hypertensive rats

OBJECTIVE: To investigate the acute effects of the superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol) on split kidney function, and renal haemodynamics, in two-kidney, one-clip (2K1C) hypertensive rats. METHODS: Three weeks after clipping, or the sham procedure, the effects of intravenous tempol (200 micromol/kg per h) were evaluated on thiobutabarbital anaesthetized Sprague-Dawley rats. RESULTS: Mean arterial pressure (MAP; 152 +/- 3 versus 122 +/- 3 mmHg, P < 0.001), plasma renin activity (28.7 +/- 3.0 versus 9.5 +/- 0.6 ng/ml per h, P < 0.001) and urinary 8-iso-prostaglandin F2alpha excretion (124 +/- 4 versus 92 +/- 10 pmol/24 h, P = 0.003) were significantly elevated in 2K1C rats compared with sham. Tempol reduced MAP by 15 +/- 1% compared with baseline (P < 0.001) in 2K1C rats. In clipped kidneys, tempol increased the glomerular filtration rate (GFR; +50 +/- 15% from baseline) and the effective renal plasma flow (ERPF; +37 +/- 13%, from baseline), and reduced renal vascular resistance (RVR; -32 +/- 6% from baseline) compared with saline-treated controls (P < 0.05). In non-clipped kidneys, tempol reduced RVR (-24 +/- 5% from baseline) compared with saline-treated controls (P = 0.001). In sham-operated rats, tempol produced a modest reduction in MAP (-8 +/- 2% from baseline, P = 0.003), but did not significantly affect renal haemodynamics or function. CONCLUSION: Tempol reduced MAP and RVR in both clipped and non-clipped kidneys of 2K1C hypertensive rats. In addition, tempol increased ERPF and GFR in the clipped kidney. These findings suggest important roles for superoxide in the regulation of renal haemodynamics during the early maintenance phase of renovascular hypertension.     

Superoxide and its interaction with nitric oxide modulates renal function in prehypertensive Ren-2 transgenic rats

OBJECTIVE: The present study was performed to examine the role of superoxide (O2*) and its interaction with nitric oxide (NO) in the regulation of renal function in prehypertensive heterozygous Ren-2 transgenic rats (TGR). METHODS: Renal responses to the O2* scavenger, tempol (150 microg/min per 100 g), and/or the NO synthase inhibitor, nitro-L-arginine methylester (L-NAME; 5 microg/min per 100 g), infused alone or in combination directly into the renal artery were evaluated in anesthetized heterozygous male TGR and aged-matched Hanover Sprague-Dawley rats (HanSD). RESULTS: There were no differences in arterial pressure (122 +/- 3 versus 115 +/- 2 mmHg), renal plasma flow (RPF; 2.09 +/- 0.1 versus 2.07 +/- 0.1 ml/min per g), glomerular filtration rate (GFR; 0.73 +/- 0.1 versus 0.74 +/- 0.1 ml/min per g) or sodium excretion (0.63 +/- 0.13 versus 0.67 +/- 0.16 micromol/min per g) between TGR and HanSD. Tempol alone caused significant increases in RPF and GFR (10 +/- 4% and 12 +/- 2%, respectively) in TGR but not in HanSD. Tempol also caused greater sodium excretory responses in TGR compared to HanSD (112 +/- 16% versus 43 +/- 7%; P < 0.05). 8-Isoprostane excretion was significantly higher in TGR than in HanSD (10.2 +/- 0.8 versus 6.5 +/- 0.7 pg/min per g), which was attenuated by tempol. L-NAME caused greater decreases in RPF and GFR in TGR (-34 +/- 4% and -22 +/- 4%, respectively) than in HanSD (-19 +/- 3% and -10 +/- 4%, respectively). Co-infusion of tempol partially attenuated the renal hemodynamic and excretory responses to L-NAME in TGR. CONCLUSIONS: These data suggest that the enhanced O2* activity and its interaction with NO during the prehypertensive phase in TGR modulates renal hemodynamic and excretory function, which may contribute to the development of hypertension in this transgenic rat model.     

Activation of vascular BK channel by tempol in DOCA-salt hypertensive rats

Large-conductance Ca2+-activated potassium (BK) channels modulate vascular smooth muscle tone. Tempol, a superoxide dismutase (SOD) mimetic, lowers blood pressure and inhibits sympathetic nerve activity in normotensive and hypertensive rats. In the present study, we tested the hypotheses depressor responses caused by tempol are partly mediated by vasodilation. It was found that tempol, but not tiron (a superoxide scavenger), dose-dependently relaxed mesenteric arteries (MA) in anesthetized sham and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Tempol also reduced perfusion pressure in isolated, norepinephrine (NE) preconstricted MA from sham and DOCA-salt hypertensive rats. Maximal responses in DOCA-salt rats were twice as large as those in sham rats. The vasodilation caused by tempol was blocked by iberiotoxin (IBTX, BK channel antagonist, 0.1 micromol/L) and tetraethylammonium chloride (TEA) (1 mmol/L). Tempol did not relax KCl preconstricted arteries in sham or DOCA-salt rats, and Nomega-nitro-L-arginine methyl ester (L-NAME), apamin, or glibenclamide did not alter tempol-induced vasodilation. IBTX constricted MA and this response was larger in DOCA-salt compared with sham rats. Western blots and immunohistochemical analysis revealed increased expression of BK channel alpha subunit protein in DOCA-salt arteries compared with sham arteries. Whole-cell patch clamp studies revealed that tempol enhanced BK channel currents in HEK-293 cells transiently transfected with mslo, the murine BK channel a subunit. These currents were blocked by IBTX. The data indicate that tempol activates BK channels and this effect contributes to depressor responses caused by tempol. Upregulation of the BK channel alpha subunit contributes to the enhanced depressor response caused by tempol in DOCA-salt hypertension.     

Protective effect of resveratrol against endotoxemia-induced lung injury involves the reduction of oxidative/nitrative stress

BackgroundResveratrol, a natural plant polyphenol, has received increasing attention because its varied bioactivities, including the inhibition of tumorigenesis, lipid modification and calorie-restriction. We aimed to investigate the effect of resveratrol on oxidative/nitrative stress in endotoxemia-associated acute lung injury.MethodsMice were injected with lipopolysaccharide (LPS, 5 mg/kg, ip). Resveratrol at a dose of 0.3 mg/kg was administered alone or immediately before injection of LPS. Twenty four hours later, lung tissues were collected for histopathologic examination, and determination of malondialdehyde (MDA), H₂O₂, reduced/oxidized glutathione (GSH/GSSG) ratio, total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity, inducible nitric oxide synthase (iNOS) expression, nitric oxide (NO) and peroxynitrite production.ResultsResveratrol treatment improves histopathological changes in the lung during endotoxemia. Increased oxidative stress in endotoxemic lung was reversed by resveratrol treatment, as evidenced by the decreases of pro-oxidant biomarker (MDA and H₂O₂), and the increases of anti-oxidant biomarkers (GSH/GSSG ratio, T-AOC, CAT and SOD activity). Treatment with resveratrol inhibited endotoxemia-induced iNOS expression and NO production. Moreover, peroxynitrite formation in endotoxemic lung was significantly attenuated after resveratrol treatment.ConclusionsResveratrol exerts protective effects against acute endotoxemia-associated lung injury. These beneficial effects may be due to both the anti-oxidant and anti-nitrative properties of resveratrol. These findings support the potential for resveratrol as a possible pharmacological agent to reduce acute lung injury resulting from oxidative/nitrative damage.     

Tempol lowers blood pressure and sympathetic nerve activity but not vascular O2- in DOCA-salt rats

This study tested the hypothesis that depressor responses caused by tempol are not associated with reductions in vascular O2- levels in urethane-anesthetized deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We compared the effects of intravenous (IV) administration of tempol, apocynin, superoxide dismutase-polyethylene glycol (PEG-SOD), and SOD on mean arterial blood pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA). In DOCA-salt rats, tempol (30 to 300 micromol/kg) dose-dependently decreased RSNA, MAP, and HR. Tempol (300 micromol/kg) decreased MAP from 140+/-5 to 83+/-4 mm Hg (P<0.05). HR decreased from 435+/-15 to 390+/-12 bpm (P<0.05). RSNA was reduced by 54%+/-6% from baseline. However, in the same rats, tempol did not reduce dihydroethidium-induced fluorescent signals in the aorta and vena cava. Apocynin (200 micromol/kg) did not lower MAP (142+/-5 mm Hg versus 140+/-6 mm Hg) or HR (428+/-15 bpm versus 420+/-13 bpm) and apocynin did not potentiate depressor responses caused by tempol. PEG-SOD (10 000 U/kg, bolus or 5000 U/kg bolus followed by a 30-minutes infusion of 500 U/kg/min) or SOD (25 000 U/kg, bolus or 10 000 U/kg bolus followed by a 30-minutes infusion of 1000 U/kg per minute) did not alter MAP or HR. It is concluded that depressor responses and decreases in HR and RSNA caused by acute tempol treatment are caused by direct sympathetic nerve activity inhibition that is not accompanied by SOD-mimetic action in the aorta or vena cava.     

Generation of hydrogen peroxide and failure of antioxidative responses in pancreatic islets of male C57BL/6 mice are associated with diabetes induced by multiple low doses of streptozotocin

Aims/hypothesis We studied the impact of the reactive oxygen species hydrogen peroxide (H₂O₂) and antioxidative enzymes on the pathogenesis of diabetes induced by multiple low doses of streptozotocin (MLD-STZ).Methods We isolated the islets of C57BL/6 mice. For ex vivo analyses, mice had been injected with MLD-STZ. For in vitro analyses, islets were incubated with different concentrations of STZ, with either of the two moieties of STZ, methylnitrosourea and d-glucose, with H₂O₂ or with alloxan. Levels of H₂O₂ generation were measured by the scopoletin method. We assessed mRNA expression of Cu/Zn and Mn superoxide dismutase, catalase, and glutathione peroxidase (GPX) by semiquantitative polymerase chain reaction. GPX activity was measured spectrophotometrically. In vitro, beta cell function was assayed by measuring basal and d-glucose-stimulated release of immunoreactive insulin using an ELISA kit.Results Ex vivo, MLD-STZ significantly increased H₂O₂ generation in male but not in female mice. It also increased GPX activity and mRNA expression of catalase, Cu/Zn and Mn superoxide dismutase, and GPX in female but not in male mice. In vitro, STZ significantly stimulated H₂O₂ generation in islets of male mice only. In male islets, alloxan increased H₂O₂ generation at a highly toxic concentration, but d-glucose and methylnitrosourea did not. Both STZ and H₂O₂ dose-dependently inhibited the release of immunoreactive insulin after a d-glucose challenge.Conclusions/interpretation The results indicate that H₂O₂ participates in the pathogenesis of MLD-STZ diabetes in male C57BL/6 mice, which do not up-regulate antioxidative enzymes in islets. Conversely, female mice are protected, probably due to an increment of several enzymes with the potential to detoxify H₂O₂.Abbreviations GPX glutathione peroxidase - H₂O₂ hydrogen peroxide - HD-STZ high-dose streptozotocin - HRP horse radish peroxidase - IRI immunoreactive insulin - MLD-STZ multiple low doses of streptozotocin - NF-B nuclear factor kappa B - O₂^–· superoxide radical - ^·OH hydroxyl radicals - ROS reactive oxygen species - SOD superoxide dismutase N. T. E. Friesen and A. S. Büchau contributed equally to this work, it being part of their doctoral theses     

Age-related changes in renal expression of oxidant and antioxidant enzymes and oxidative stress markers in male SHR and WKY rats

Oxidative stress has been hypothesized to play a role in aging and age-related disorders, such as hypertension. This study compared levels of oxidative stress and renal expression of oxidant and antioxidant enzymes in male normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) at different ages (3 and 12 months). In the renal cortex of 3-month old SHR increases in hydrogen peroxide (H₂O₂) were accompanied by augmented expression of NADPH oxidase subunit Nox4 and decreased expression of antioxidant enzymes SOD1 and SOD3. A further increase in renal H₂O₂ production and urinary TBARS was observed in 12-month old WKY and SHR as compared with 3-month old rats. Similarly, expressions of NADPH oxidase subunit p22^phox, SOD2 and SOD3 were markedly elevated with age in both strains. When compared with age-matched WKY, catalase expression was increased in 3-month old SHR, but unchanged in 12-month old SHR. Body weight increased with aging in both rat strains, but this increase was more pronounced in WKY. In conclusion, renal oxidative stress in 12-month old SHR is an exaggeration of the process already observed in the 3-month old SHR, whereas the occurrence of obesity in 12-month old normotensive rats may partially be responsible for the age-related increase in oxidative stress.     

Antioxidant Function of Ambroxol in Mononuclear and Polymorphonuclear Cells in Vitro

This study quantifies the antioxidant function of ambroxol (2-amino-3,5-dibromo-N-[trans-4-hydroxycyclohexyl]benzylamine) in vitro. Polymorphonuclear cells (PMN) and mononuclear cells were isolated from the blood of healthy volunteers (n= 46) to determine reactive oxygen species (ROS) by luminol-enhanced chemiluminescence. Ambroxol or the controls N-acetylcysteine (NAC), nacystelyn (NAL), glutathione (GSH), superoxide dismutase (SOD), catalase, and the combination of SOD/catalase were incubated for 1 or 2 h with zymosan-activated cells in vitro using concentrations ranging from 10⁻⁶ to 10⁻³ mol/liter. Reduction of ROS-mediated luminescence was similar within the cell types. Ambroxol (10⁻⁴ mol/liter) reduced ROS about 75% (1-h incubation) and 98% (2-h incubation), respectively (p < 0.001). SOD and SOD/catalase, but not the H₂O₂-catalyzing substances (NAC, NAL, GSH, and catalase), reduced cellular ROS. This indicates that inflammatory cells predominantly generate O⁻ ₂, which can be scavenged by ambroxol. The antioxidant function of ambroxol with increasing incubation time suggests additional cellular antiinflammatory properties of this substance. Our results indicate that good antioxidant function of ambroxol is related mainly to direct scavenger function of reactive oxygen metabolites such as O⁻ ₂. However, an antioxidative effect of ambroxol may also be associated with the reduction of prooxidative metabolism in inflammatory cells. Concluding from this observation, and because of the well known high affinity of ambroxol for lung tissue, ambroxol may be an alternative in antioxidant augmentation therapy, particularly in pulmonary diseases characterized by an overburden of toxic oxygen metabolites. Accepted for publication: 5 December 1996     

Superoxide dismutase and catalase activity in naturally derived commercial surfactants

Despite the role of reactive oxygen species in the development of respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD) in preterm infants, the anti‐oxidant properties of commercial surfactants have never been studied. We measured the superoxide dismutase (SOD) and catalase (CAT) activity, the scavenger activity against hydrogen peroxide (H₂O₂), and its changes after the addition of SOD and CAT in four natural surfactants, namely Infasurf, Curosurf, Survanta, and Alveofact. We found that they contain measurable amount of SOD and CAT. Curosurf and Survanta seem to have higher antioxidant effect than Infasurf and Alveofact. Moreover, the highest phospholipid concentration and recommended dose of Curosurf imply that its scavenger activity for each treatment dose in preterm infants is likely higher than that of Survanta. Finally, the supplementation with SOD and CAT induced a remarkable increase of antioxidant action in all studied surfactants. Pediatr Pulmonol. 2009; 44:1125–1131. ©2009 Wiley‐Liss, Inc.     

RETRACTED ARTICLE: Angiotensin-II-induced oxidative stress elicits hypoadiponectinaemia in rats

Aims/hypothesis Hypertension, endothelial dysfunction and insulin resistance are associated conditions that share oxidative stress and vascular inflammation as common features. Adiponectin is an abundant plasma adipokine that plays a physiological role in modulating lipid metabolism and exerts a potent anti-inflammatory activity. We hypothesised that adiponectin levels decrease in response to oxidative stress and that this may promote the development of hypertension, endothelial dysfunction and insulin resistance.Methods Rats were infused with angiotensin II (AngII) or its vehicle, either alone or in combination with tempo1 (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl), a membrane-permeable metal-independent superoxide dismutase mimetic, or tetrahydrobiopterin (BH4), one of the most potent naturally occurring reducing agents and an essential cofactor for nitric oxide synthase activity. Heart rate, systolic blood pressure, body weight and serum levels of adiponectin were measured on day 7 of treatment, and then the animals were killed. Vessel tone and superoxide production were measured ex vivo in thoracic vascular rings. The expression of adiponectin mRNA in adipose tissue was assessed by Northern blotting, and in 3T3-L1 adipocytes exposed to H₂O₂ by real-time PCR. The expression of NAD(P)H oxidase subunit mRNAs in the rats was assessed by RT-PCR and real-time PCR.Results Hypertension and endothelial dysfunction were induced in rats by infusion of AngII and reversed by administration of tempol. Plasma concentrations of adiponectin and adipose tissue levels of adiponectin mRNA were decreased in AngII-infused rats, and this effect was prevented by cotreatment with tempol or BH4. The production of superoxide anions (O₂^–) was significantly increased in the aortae of AngII-treated rats, and this increase was prevented by the administration of tempol or BH4. Levels of mRNAs that encode NAD(P)H oxidase components, including p22phox, gp91phox, p47phox and Rac1, were similarly increased in adipose tissue, aortae and hearts of AngII-infused rats. Cotreatment of rats with tempol or BH4 reversed AngII-induced increases in NAD(P)H oxidase subunit mRNAs. Fully differentiated 3T3-L1 adipocytes, also exhibited diminished adiponectin mRNA levels when exposed to low concentrations of H₂O₂.Conclusions/interpretation Our results demonstrate that AngII-induced oxidative stress and endothelial dysfunction are accompanied by a decrease in adiponectin gene expression. Since antioxidants were observed to prevent the actions of AngII, and H₂O₂ on its own suppressed adiponectin expression, we conclude that adiponectin gene expression is negatively modulated by oxidative stress. Plasma adiponectin levels may provide a useful indicator of oxidative stress in vivo, and suppressed levels may contribute to the proinflammatory and metabolic derangements associated with type 2 diabetes, coronary artery disease and the metabolic syndrome.     

Evaluation of the effects of different supplementation on oxidative status in patients with rheumatoid arthritis

Rheumatoid arthritis is a chronic inflammatory disease. Reactive oxygen species have been considered as aggravating factors for autoimmune diseases. Fatty acids had been linked in reduction of various diseases by augment of their antioxidant potential and antiinflammatory mechanisms. The aim of this study was to assess the oxidative status in patients with rheumatoid arthritis who used concentrated fish oil only or concentrated fish oil in combination with evening primrose oil in a period of 3 months. Subjects were divided into three groups. The group I consists of patients who had been taking only their regular rheumatologic therapy; group II, patients who had been taking concentrated fish oil; and group III, patients who had been taking concentrated fish oil and evening primrose oil. Peripheral blood samples were used for all the assays. We assessed the following oxidative stress markers: index of lipid peroxidation (thiobarbituric acid-reactive substances (TBARS)), hydrogen peroxide (H₂O₂), superoxide anion radical (O₂ ^?), nitric oxide (NO), superoxide dismutase activity (SOD), catalase activity (CAT), and glutathione levels (GSH) in erythrocytes. There were no statistically significant changes for any of the oxidative stress parameters in group I. In group II, levels of TBARS, NO₂ ^?, and GSH were increased, while levels of H₂O₂ decreased. Increased values of TBARS, NO₂ ^?, and SOD were found in group III. Our findings indicate that intakes of fish oil and evening primrose oil may be of importance in mitigation of inflammation, disease activity, and oxidative stress biomarkers, through increased activities of antioxidant enzymes.     

Chronic treatment with a superoxide dismutase mimetic prevents vascular remodeling and progression of hypertension in salt-loaded stroke-prone spontaneously hypertensive rats

Oxidative stress has been implicated in the pathogenesis of hypertension. The aim of the present study was to determine whether increased generation of vascular superoxide anion (·O₂⁻) contributes to blood pressure elevation by influencing vascular function and structure in severely hypertensive rats. Sixteen-week-old stroke-prone spontaneously hypertensive rats (SHRSP) (n = 12) were randomly divided into two groups to receive the superoxide dismutase mimetic, tempol (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl) (1 mmol/L in drinking water) or tap water. Both groups were fed a high-salt diet (4% NaCl). Systolic blood pressure (SBP) was measured weekly for 6 weeks by the tail-cuff method. Rats were killed, and vascular structure (media:lumen ratio) and endothelial function (acetylcholine [Ach]–induced vasodilation) were assessed in small mesenteric arteries mounted as pressurized preparations. Vascular ·O₂⁻ concentration was measured by lucigenin (5 μmol/L) chemiluminescence. Plasma total antioxidant status was assessed spectrophotometrically. The SBP increased significantly (P < .01) in the control group, whereas progression of hypertension was prevented in the tempol-treated group. Tempol reduced (P < .01) the media:lumen ratio (7.2% ± 0.01%) compared with that in controls (12.0% ± 0.01%). Maximal Ach-induced dilation was altered in control rats (40% ± 9%) but was not influenced by tempol (57% ± 1 7%). Vascular ·O₂⁻ concentration was lower (P < .01) and plasma total antioxidant concentration was higher (P < .05) in the treated group compared with the control. In conclusion, tempol prevents progression of hypertension. These processes are associated with attenuated vascular remodeling, decreased vascular ·O₂⁻ concentration, and increased antioxidant status. Our data suggest that oxidative stress plays an important role in vascular damage associated with severe hypertension in salt-loaded SHRSP.     

Myocardial H2O2 production in the unanaesthetized rat Influence of fasting,myocardial load and inhibition of superoxide dismutase and monoamine oxidase

Summary Myocardial H₂O₂ production was studied by means of the in vivo administration of aminotriazole (AT), which inactivates the catalase-H₂O₂ complex compound I. Measurements of the residual catalase activity in male and female rats indicate that -oxidation of fatty acids in peroxisomes does not contribute in a substantial way to energy production in response to fasting or to an increased myocardial load, despite previous data on peroxisomes in myocardium.Superoxide dismutase (SOD) inhibition by diethyldithiocarbamate demonstrates that SOD participates in the production of H₂O₂ in physiological conditions. Such a role was not demonstrated for monoamine oxidase through inhibition by phenelzine.     

2-甲氧基雌二醇和2-乙氧基雌二醇减少老年肥胖糖尿病ZSF1大鼠的肾疾病进展

目的检查2-ME和其一个合成类似物2EE(2-ETHOXYESTRADIOL)对高血压、肥胖和肾脏病进展的影响。方法:实验在35周肥胖ZSF_1大鼠中进行。动物分对照组(PEG-400,0.5μl/ h)和治疗组,2ME,2EE(18μg/kg/h),在0周,3,6和9周时分别测定代谢和肾功能,在9周时评价肾血流动力学和排泄功能。结果2ME,2EE对肥胖和高血压无作用,但可降低糖化血红蛋白和糖尿,防止时间依赖的蛋白尿的增加。2ME和2EE显著增加肾血流和肾小球滤过,减少肾血管阻力;免疫标记肾皮质标本,肥胖动物比同窝出生雄瘦动物有显示增加PCNA,NF-KAPPA B和VEGF的表达。2ME,2EE减少PCNA,NF-KAPPA B和VEGF的表达。结论雌二醇的非雌性激素的代谢物2ME和2EE,对代谢病和肥胖相关的肾病有直接的肾脏保护作用。     

Mitochondrial complex I and NAD(P)H oxidase are major sources of exacerbated oxidative stress in pressure-overloaded ischemic-reperfused hearts

We tested the hypothesis that pressure overload exacerbates oxidative stress associated with augmented mitochondrial permeability transition (MPT) pore opening and cell death in ischemic-reperfused hearts. Pressure overload decreased the level of reduced glutathione but increased nitrotyrosine and 8-hydroxydeoxyguanosine levels in ischemic-reperfused hearts. The activity of catalase, but not superoxide dismutase (SOD), was lower in ischemic-reperfused hearts perfused at higher pressure. Mitochondria from ischemic-reperfused hearts subjected to higher perfusion pressure displayed significantly greater [³H]-2-deoxyglucose-6-P entrapment suggestive of greater MPT pore opening and consistent with greater necrosis and apoptosis. Tempol (SOD mimetic) reduced infarct size in both groups but it remained greater in the higher pressure group. By contrast, uric acid (peroxynitrite scavenger) markedly reduced infarct size at higher pressure, effectively eliminating the differential between the two groups. Inhibition of xanthine oxidase, with allopurinol, reduced infarct size but did not eliminate the differential between the two groups. However, amobarbital (inhibitor of mitochondrial complex I) or apocynin [inhibitor of NAD(P)H oxidase] reduced infarct size at both pressures and also abrogated the differential between the two groups. Consistent with the effect of apocynin, pressure-overloaded hearts displayed significantly higher NAD(P)H oxidase activity. Furthermore, pressure-overloaded hearts displayed increased nitric oxide synthase activity which, along with increased propensity to superoxide generation, may underlie uric acid-induced cardioprotection. In conclusion, increased oxidative and nitrosative stress, coupled with lack of augmented SOD and catalase activities, contributes importantly to the exacerbating impact of pressure overload on MPT pore opening and cell death in ischemic-reperfused hearts.     

Oxygen toxicity

The “free radical theory of oxygen toxicity” attributes the damaging effects of hyperoxia to highly-reactive metabolic products of oxygen (O₂) that can inactivate enzymes in the cell, damage DNA and destroy lipid membranes. To protect the organism from these cytotoxic O₂ metabolites, an array of cooperative antioxidant defense systems have evolved. These include the enzyme superoxide dismutase (SOD), catalase and glutathione peroxidase, plus other endogenous antioxidants such as ascorbate and vitamin E. The increased levels of O₂-free radicals produced during hyperoxia may overwhelm these normal antioxidant defense systems. The ability to respond rapidly to hyperoxic challenge with increased antioxidant activity has been shown repeatedly to be associated with relative tolerance to O₂-induced injury and lethality.Treatment with exogenous SOD or vitamin E has had some clinical success in combating O₂-free radical-mediated tissue injury. Treatment with small doses of bacterial endotoxin has provided almost complete protection to rats against pulmonary O₂ toxicity; this agent seems to act by facilitating rapid increases in endogenous antioxidant enzyme levels.An increased understanding of the molecular mechanisms of O₂ toxicity and of the endogenous defenses that organisms have evolved against O₂-free radical injury may lead to a more rational basis for the clinical use of O₂ and to the development of therapeutic measures effective in preventing or ameliorating O₂ toxicity. These measures may involve (1) tests aimed at estimating a person's tolerance to hyperoxia at any given time, (2) means to effectively deliver exogenous antioxidants and (3) methods to augment endogenous antioxidant defenses.