Age-related reduction of NO availability and oxidative stress in humans

Age-related endothelial dysfunction could be caused by an alteration in the L-arginine-NO system and the production of oxidative stress in both normotensive and hypertensive individuals. In 47 normotensive subjects and 49 patients with essential hypertension, we evaluated forearm blood flow (by strain-gauge plethysmography) modifications induced by intrabrachial sodium nitroprusside (1, 2, and 4 microg/100 mL per minute) and acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 microg/100 mL per minute), an endothelium-independent vasodilator and an endothelium-dependent vasodilator, respectively. Acetylcholine was repeated in the presence of the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA, 100 microg/100 mL per minute), the antioxidant vitamin C (8 mg/100 mL per minute), or both. Vasodilation to acetylcholine, but not to sodium nitroprusside, was lower (P<0.01) in hypertensive patients compared with control subjects. Moreover, in both groups, endothelium-dependent vasodilation declined with aging. In normotensive subjects, the inhibiting effect of L-NMMA on response to acetylcholine decreased in parallel with advancing age, whereas vitamin C increased vasodilation to acetylcholine in only the oldest group (age >60 years). In young hypertensive patients (age <30 years), vasodilation to acetylcholine was sensitive to L-NMMA, whereas in hypertensive patients age >30 years, vitamin C enhanced endothelium-dependent vasodilation and restored the inhibiting effect of L-NMMA on response to acetylcholine. In normotensive individuals, an earlier primary dysfunction of the NO system and a later production of oxidative stress cause age-related reduction in endothelium-dependent vasodilation. These alterations are similar but anticipated in hypertensive patients compared with normotensive subjects.     

Evidence of oxidative stress in chronic heart failure in humans

Chronic heart failure (CHF) due to coronary artery disease (CAD)has been shown to be associated with increased plasma thiobarbituricreactive substances (TBARS) and reduced plasma thiol (PSH) concentrations,suggesting oxidative stress (OS). The aims of the present studieswere (a) to determine whether OS is due to CAD or CHF per seand (b) to determine if a wider range of more specific markersof OS are abnormal in CHF. In the first study, two groups of patients (n = 15 each) werecompared. Group 1 (11 male, mean age 56 years) had CHF due toCAD and group 2 (12 male, mean age 53 years) had non-CAD CHF.Median plasma TBARS in controls was 7.6 nmol . ml^–1 ,10.0 nmol . m^–1 in group 1 and 9.3 nmol. ml^–1 ingroup 2 (P < 0.01 both groups vs control). Median PSH was505 384 and 364 nmol. ml^–1 (P < 0.05 and P < 0.01vs control) respectively. Fifty-three patients with CHF were recruited in the second study.Malondialdehyde and PSH were 10.3 and 409 nmol. ml^–1 respectively,compared to control values of 7.9 and 560 nmol. ml^.1 (both P< 0.001). The median values for the following additionalmeasures of OS in controls and patients were: erythrocyte superoxidedismustase 131 vs 114 U . l^–1 (P = 0.005); caeruloplasminoxidase 97 vs 197 U. l^–1 (P < 0.01); erythrocyte glutathione1.56 nmol . ml^–1 vs 1.77 nmol . ml^–1 (P < 0.02);plasma conjugated dienes 0.28 vs 0.33 optical density units(P = ns). Chronic heart failure, regardless of aetiology, is associatedwith abnormalities of a range of markers of OS.     

N-acetylcysteine attenuates alcohol-induced oxidative stress in the rat

AIM: There is increasing evidence that alcohol-induced liver damage may be associated with increased oxidative stress. We aimed to investigate free-radical scavenger effect of n-acetylcysteine in rats intragastrically fed with ethanol. METHODS: Twenty-four rats divided into three groups were fed with ethanol (6 g/kg/day, Group 1), ethanol and n-acetylcysteine (1 g/kg, Group 2), or isocaloric dextrose (control group, Group 3) for 4 weeks. Then animals were sacrificed under ether anesthesia, intracardiac blood and liver tissues were obtained. Measurements were performed both in serum and in homogenized liver tissues. Malondialdehyde (MDA) level was measured by TBARS method. Glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) levels were studied by commercial kits. Kruskal-Wallis test was used for statistical analysis. RESULTS: ALT and AST in Group 1 (154 U/L and 302 U/L, respectively) were higher than those in Group 2 (94 U/L and 155 U/L) and Group 3 (99 U/L and 168 U/L) (P=0.001 for both). Serum and tissue levels of MDA in Group 1 (1.84 nmol/mL and 96 nmol/100 mg-protein) were higher than Group 2 (0.91 nmol/mL and 64 nmol/100 mg-protein) and Group 3 (0.94 nmol/mL and 49 nmol/100 mg-protein) (P<0.001 for both). On the other hand, serum GSH-Px level in Group 1 (8.21 U/g-Hb) was lower than Group 2 (16 U/g-Hb) and Group 3 (16 U/g-Hb) (P<0.001). Serum and liver tissue levels of SOD in Group 1 (11 U/mL and 26 U/100 mg-protein) were lower than Group 2 (18 U/mL and 60 U/100 mg-protein) and Group 3 (20 U/mL and 60 U/100 mg-protein) (P<0.001 for both). CONCLUSION: This study demonstrated that ethanol-induced liver damage is associated with oxidative stress, and co-administration of n-acetylcysteine attenuates this damage effectively in rat model.     

Peroxyl-induced oxidative stress in aging erythrocytes of rat

This study aims at determining the possible changes in intracellular calcium (Ca_i²⁺), plasma membrane calcium ATPase (PMCA) activity and phosphatidylserine (PS) along with glutathione (GSH) level in response to an oxidant challenge in vitro. Erythrocytes were isolated on Percoll and incubated with 2, 2′azobis (2-aminopropane) hydrochloride (AAPH) as well as with vitamin C preceding AAPH incubation. Membrane integrity in terms of hemolysis was negatively related to acetylcholine esterase (AChE) activity with the extent of reduction under OS being higher in the old erythrocyte than in the young. A divergent pattern was seen towards lower PMCA and higher (Ca_i²⁺) in the young and old cells. However, the PMCA activity in the stressed young cell was high when pre-treated with vitamin C. PS externalization in the young under OS is perhaps analogous to normal aging, with vitamin C preventing premature death. These findings suggest that young erythrocytes may benefit from vitamin C in therapies addressed towards the mechanisms underlying the reduced effects of OS.     

Wine and oxidative stress: Up-to-date evidence of the effects of moderate wine consumption on oxidative damage in humans

Wine and alcohol consumption has been considered to be protective against coronary heart disease development, an oxidative stress associated disease. Wine contains polyphenols displaying antioxidant properties tested in in vitro and in vivo studies. Due to this, a general consensus exists, both among the general public and the scientific community, that wine, particularly red wine, is an antioxidant beverage. Alcohol consumption, however, is associated with oxidative damage. Several studies have been carried out on the antioxidant health benefits of wine and wine polyphenols. However, adequate scientific evidence (Level I or II) is required to be provided before recommendations or statements which can reach the general public can be formulated. Here, we summarize the state of the art of the up-to-date body of knowledge, and the extent to which there exists evidence of the benefits of moderate wine consumption on oxidative damage in humans. From the available data, there is no evidence, at present, that sustained wine consumption provides antioxidant benefits in healthy volunteers other than to counteract a possible pro-oxidative effect of the alcohol. On the contrary, data on the antioxidant protective effect of red wine in oxidative stress situations are promising. In this way, the postprandial oxidative stress after a meal, despite the diversity of biomarkers used for its evaluation, is counteracted by the ingestion of wine. Further studies are warranted.     

Hypothyroidism induces selective oxidative stress in amygdala and hippocampus of rat

The effects of hypothyroidism on lipid peroxidation (LP), reactive oxygen species (ROS), and nitric oxide synthase (NOS), levels and expression, in rat brain were examined. Hypothyroidism was induced by administering methimazole in drinking water (60 mg/kg/day). In striatum, motor cortex and cerebellum of hypothyroid rats LP was not modified, whereas LP and ROS increased in amygdala and hippocampus of hypothyroid rats at the third week of treatment with methimazole as compared to euthyroid group values. Regarding NOS participation, only hippocampal constitutive-NOS activity was increased, accompanied by an augmentation in nNOS expression. Results show that hypothyroidism induces selective oxidative stress in both the hippocampus and amygdala, where the nitrergic system is involved.     

Alterations in oxidative stress scavenger system in aging rat brain and lymphocytes

There is a large body of evidence indicating an age-related increase in the rate of mitochondrial O₂ ⁻ and H₂O₂ generation and huge amounts of oxidative damage leading to several neurodegenerative disorders, perhaps due to an imbalance between free radical generation and anti-oxidant defense system. The aim of the present study was to elucidate the effect of aging on free radical scavenger system profile in rat brain and lymphocytes. The enzyme activities of γ-GCS, GR, GPx, γ-GTP, GST, catalase, and SOD as well as GSH content were assayed from discrete brain areas viz., CH, CB,BS and DC along with lymphocytes from four different age group rats, namely, 1-month-oldyoung rats, 3–4-month-old young adults, 12-month-old adults and 24-month-old aged rats. Significant decline was observed in all the enzyme activities in 12- and 24-month-old rats as compared to 3–4-month-old young adult rats and also, 1-month-old rats showed lower levels of enzyme activities as compared to 3–4-month-old rats. The maximum scavenger system activity was found in the young adult rats (3–4 months) as compared to the remaining age groups. Lymphocytes and brain showed a parallel pattern of age-related alterations in the free radical scavenger system components. The analysis of such alterations is important in ultimately determining the basis of neuronal dysfunction associated with aging and also defining the nature of these changes may help to develop therapeutic means to cure not only elderly but also individuals suffering from certain organic or psychiatric disorders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evidence that 2-methylacetoacetate induces oxidative stress in rat brain

In the present study we investigated the effects of 2-methylacetoacetate (MAA) and 2-methyl-3-hydroxybutyrate (MHB), the major metabolites accumulating in mitochondrial 2-methylacetoacetyl-CoA thiolase (KT) and 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) deficiencies, on important parameters of oxidative stress in cerebral cortex from young rats. We verified that MAA induced lipid peroxidation (increase of thiobarbituric acid-reactive substances (TBA-RS) and chemiluminescence values), whereas MHB did not alter these parameters. MAA-induced increase of TBA-RS levels was fully prevented by free radical scavengers, indicating that free radicals were involved in this effect. Furthermore, MAA, but not MHB, significantly induced sulfhydryl oxidation, implying that this organic acid provokes protein oxidative damage. It was also observed that MAA reduced GSH, a naturally-occurring brain antioxidant, whereas MHB did not change this parameter. Furthermore, the decrease of GSH levels caused by MAA was not due to a direct oxidative action, since this organic acid did not alter the sulfhydryl content of a commercial solution of GSH in a cell free medium. Finally, MAA and MHB did not raise nitric oxide production. The data indicate that MAA induces oxidative stress in vitro in cerebral cortex. It is presumed that this pathomechanism may be involved in the brain damage found in patients affected by KT deficiency.     

Increased methylglyoxal and oxidative stress in hypertensive rat vascular smooth muscle cells

Methylglyoxal can yield advanced glycation end products via nonenzymatic glycation of proteins. Whether methylglyoxal contributes to the pathogenesis of hypertension has not been clear. The aim of the present study was to investigate whether the levels of methylglyoxal and methylglyoxal-induced advanced glycation end products were enhanced and whether methylglyoxal increased oxidative stress, activated nuclear factor-kappaB (NF-kappaB), and increased intracellular adhesion molecule-1 (ICAM-1) content in vascular smooth muscle cells from spontaneously hypertensive rats. Basal cellular levels of methylglyoxal and advanced glycation end products were more than 2-fold higher (P<0.05) in cells from hypertensive rats than from normotensive Wistar-Kyoto rats. This correlated with levels of oxidative stress and oxidized glutathione that were significantly higher in cells from hypertensive rats, whereas levels of glutathione and activities of glutathione reductase and glutathione peroxidase were significantly lower. Basal levels of nuclearly localized NF-kappaB p65 and ICAM-1 protein expression were higher in cells from hypertensive rats than from normotensive rats. Addition of exogenous methylglyoxal to the cultures induced a greater increase in oxidative stress and advanced glycation end products in cells from hypertensive rats compared with normotensive rats and significantly decreased the activities of glutathione reductase and glutathione peroxidase in cells of both rat strains. Methylglyoxal activated NF-kappaB p65 and increased ICAM-1 expression in hypertensive cells, which was inhibited by N-acetylcysteine. Our study demonstrates an elevated methylglyoxal level and advanced glycation end products in cells from hypertensive rats, and methylglyoxal increases oxidative stress, activates NF-kappaB, and enhances ICAM-1 expression. Our findings suggest that that elevated methylglyoxal and associated oxidative stress possibly contribute to the pathogenesis of hypertension.     

Angiotensin II and oxidative stress in Dahl Salt-sensitive rat with heart failure

Reactive oxygen species have an important pathogenic role in organ damage. We investigated the role of oxidative stress via nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase in the kidney of the Dahl salt-sensitive (DS) rats with heart failure (DSHF). Eleven-week-old DS rats fed an 8%-NaCl diet received either vehicle or imidapril (1 mg/kg per day) for 7 weeks. The renal expression of the NAD(P)H oxidase p47phox and endothelial NO synthase were evaluated. In DSHF rats, associated with increased renal angiotensin II, mRNA and protein expression of NAD(P)H oxidase p47phox were enhanced with an increase in renal lipid peroxidation production (0.33+/-0.03 versus 0.22+/-0.01 nmol/mg protein, P<0.05) and urinary excretion of hydrogen peroxide (26.9+/-6.6 versus 9.5+/-2.1 U/mg creatinine, P<0.01) compared with levels in Dahl salt-resistant rats. The endothelial NO synthase expression was decreased in the kidney. Treatment with imidapril reduced renal angiotensin II and NAD(P)H oxidase expression and the oxidative products (kidney lipid peroxidation product: 0.16+/-0.02, P<0.001; urinary hydrogen peroxide: 3.1+/-0.2, P<0.01 versus DSHF rats). Imidapril significantly decreased albuminuria and reduced glomerulosclerosis without changes in the blood pressure. In conclusion, DSHF rats showed increased oxidative stress in the kidney via NAD(P)H oxidase. Blockade of local angiotensin II with subpressor dose of imidapril inhibited NAD(P)H oxidase and prevented renal damage.     

Seasonal superoxide overproduction and endothelial activation in guinea-pig heart; seasonal oxidative stress in rats and humans

Seasonality in endothelial dysfunction and oxidative stress was noted in humans and rats, suggesting it is a common phenomenon of a potential clinical relevance. We aimed at studying (i) seasonal variations in cardiac superoxide (O₂⁻) production in rodents and in 8-isoprostane urinary excretion in humans, (ii) the mechanism of cardiac O₂⁻ overproduction occurring in late spring/summer months in rodents, (iii) whether this seasonal O₂⁻-overproduction is associated with a pro-inflammatory endothelial activation, and (iv) how the summer-associated changes compare to those caused by diabetes, a classical cardiovascular risk factor.Langendorff-perfused guinea-pig and rat hearts generated ~ 100% more O₂⁻, and human subjects excreted 65% more 8-isoprostane in the summer vs. other seasons. Inhibitors of NADPH oxidase, xanthine oxidase, and NO synthase inhibited the seasonal O₂⁻-overproduction. In the summer vs. other seasons, cardiac NADPH oxidase and xanthine oxidase activity, and protein expression were increased, the endothelial NO synthase and superoxide dismutases were downregulated, and, in guinea-pig hearts, adhesion molecules upregulation and the endothelial glycocalyx destruction associated these changes. In guinea-pig hearts, the summer and a streptozotocin-induced diabetes mediated similar changes, yet, more severe endothelial activation associated the diabetes.These findings suggest that the seasonal oxidative stress is a common phenomenon, associated, at least in guinea-pigs, with the endothelial activation. Nonetheless, its biological meaning (regulatory vs. deleterious) remains unclear. Upregulated NADPH oxidase and xanthine oxidase and uncoupled NO synthase are the sources of the seasonal O₂⁻-overproduction.     

Differential vulnerability to oxidative stress in rat cardiac myocytes versus fibroblasts

OBJECTIVES

This study was designed to test the hypothesis that cardiac myocytes have greater vulnerability to oxidative stress compared with cardiac fibroblasts.

BACKGROUND

The function of cardiac myocytes differs from that of fibroblasts in the heart, but differences in their response to oxidative stress have not been extensively studied.

METHODS

Cardiomyocytes and fibroblasts from F344 neonatal rat hearts were cultured and exposed to different concentrations of hydrogen peroxide (H_{2 2}) and menadione (superoxide generator). The mitogen-activated protein kinase (MAPK) proteins were assayed after oxidative stress; cell death was determined by trypan blue staining and deoxyribonucleic acid (DNA) ladder electrophoresis.

RESULTS

The cardiac myocytes were significantly more vulnerable than the fibroblasts to oxidative damage, showing substantial DNA fragmentation and consistently poor cell survival after exposure to H_{2 2} (100 to 800 μM), while the cardiac fibroblasts demonstrated little or no DNA fragmentation, and superior cell survival rates both over time (from 1 to 72 h after 100 μM) and across increasing doses of H_{2 2} (100 to 800 μM). The p42/44 extracellular signal-regulated kinases were phosphorylated in both cell types after exposure to H_{2 2}, but significantly more in cardiac fibroblasts. However, p38 MAPK and c-jun NH₂-terminal kinase were phosphorylated more in the cardiac myocytes compared to cardiac fibroblasts. This was also the case after exposure to menadione.

CONCLUSION

Taken together, these results suggest that oxidative stress causes greater injury and cell death in cardiac myocytes compared with cardiac fibroblasts. It is possible that the signaling differences via the MAPK family may partly mediate the observed differences in vulnerability and functional outcomes of the respective cell types.     

Melatonin protects against rotenone-induced oxidative stress in a hemiparkinsonian rat model

In the present study, we evaluated the effect of melatonin, a well-known free radical scavenger and neuroprotector, against rotenone-induced oxidative stress in a hemiparkinsonian rat model. The effect of melatonin on glutathione (GSH) depletion caused by unilateral, intranigral infusion of rotenone was investigated employing a spectrofluorimetric procedure. We also studied the effect of melatonin on rotenone-induced changes in the antioxidant enzymes superoxide dismutase (SOD) and catalase in the cytosolic fractions of substantia nigra (SN), employing spectrophotometric procedures. Rotenone-induced hydroxyl radicals (*OH) in the isolated mitochondria, as measured employing a sensitive HPLC-electrochemical method, were significantly scavenged by melatonin. Melatonin treatment restored the rotenone-induced decrease in GSH level and changes in antioxidant enzyme (SOD and catalase) activities in the SN. Our results strongly indicate melatonin's beneficial use in Parkinson's disease therapy as an antioxidant.     

Promotion of oxidative stress by 3-hydroxyglutaric acid in rat striatum

Summary The pathophysiology of the striatum degeneration characteristic of patients affected by the inherited neurometabolic disorder glutaryl-CoA dehydrogenase deficiency (GDD), also known as glutaric aciduria type I, is still in debate. We have previously reported that 3-hydroxyglutaric acid (3-OH-GA) considered the main neurotoxin in this disorder, induces oxidative stress in rat cerebral cotex. In the present work, we extended these studies by investigating the in vitro effect of 3-OH-GA, at concentrations ranging from 0.01 to 1.0 mmol/L on the brain antioxidant defences by measuring total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR) and glutathione (GSH) levels, and on the production of hydrogen peroxide (H₂O₂), nitric oxide (NO) and malondialdehyde in striatum homogenates from young rats. We observed that TRAP, TAR and GSH levels were markedly reduced (by up to 50%) when striatum homogenates were treated with 3-OH-GA. In contrast, H₂O₂ (up to 44%), NO (up to 95%) and malondialdehyde levels (up to 28%) were significantly increased by 3-OH-GA. These data indicate that total nonenzymatic antioxidant defences (TRAP) and the tissue capacity to handle an increase of reactive species (TAR) were reduced by 3-OH-GA in the striatum. Furthermore, the results also reflect an increase of lipid peroxidation, probably secondary to 3-OH-GA-induced free radical production. Thus, it may be presumed that oxidative stress is involved in the neuropathology in GDD.     

过量摄氟对大鼠脑组织氧化侵袭与细胞凋亡的影响

目的研究过量摄入氟对大鼠神经系统损伤过程脑细胞氧化应激相关指标和脑细胞周期变化与细胞凋亡率的关系。方法应用饮水加入氟化钠进行大鼠染毒实验,测定大鼠脑细胞谷胱甘肽过氧化物酶(GSH-Px)活性、超氧化物歧化酶(SOD)活性和脂质过氧化终产物丙二醛(MDA)产生水平以及脑细胞周期变化及细胞凋亡率。结果过量氟可使脑细胞氧化应激能力发生改变,SOD活力水平投氟实验组与对照组相比差异不明显(P>0.05),在投氟实验组MDA生成与对照组相比差异不明显(P>0.05),慢性氟中毒大鼠GSH-Px活力增高,在低钙投氟组高于低钙对照组差异显著(P<0.05);低钙饲养组脑细胞增殖能力普遍降低,S期细胞比例降低,脑细胞凋亡率高钙投氟组与高钙对照组相比差异不明显(P>0.05),低钙投氟组明显高于低钙对照组差异显著(P<0.001);低钙投氟组大鼠GSH-Px活力增高与脑细胞凋亡率呈正比。结论过量氟所致的大鼠脑细胞增殖能力下降和脑细胞凋亡率增高,与氟神经毒性作用机制有关,低钙营养可加重氟的神经毒性作用;过量氟可引起脑细胞抗氧化酶类发生不同程度的变化,其中抗氧化酶类活性增强可能是脑神经细胞对氧化侵袭的自身保护性生理调节作用的表现;氧化侵袭对神经系统损伤的确切机制尚需进一步研究。