Targets of oxidative stress in cardiovascular system

Although oxidants such as superoxide (O₂.^-) and hydrogen peroxide (H₂O₂) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca²⁺ concentration. Oxidants cause cellular Ca²⁺ mobilization by modulating activities of a variety of regulators such as Na⁺/H⁺ and Na⁺/Ca²⁺ exchangers, Na⁺/K⁺ ATPase and Ca²⁺ ATPase and Ca²⁺ channels that are associated with Ca²⁺ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca²⁺ level by oxidants plays a pivotal role in indicing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxindant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditoins such as atherosclerosis, apoptosis and necrosis in the myocardium     

Renin-angiotensin-aldosterone system and oxidative stress in cardiovascular insulin resistance

Hypertension commonly occurs in conjunction with insulin resistance and other components of the cardiometabolic syndrome. Insulin resistance plays a significant role in the relationship between hypertension, Type 2 diabetes mellitus, chronic kidney disease, and cardiovascular disease. There is accumulating evidence that insulin resistance occurs in cardiovascular and renal tissue as well as in classical metabolic tissues (i.e., skeletal muscle, liver, and adipose tissue). Activation of the renin-angiotensin-aldosterone system and subsequent elevations in angiotensin II and aldosterone, as seen in cardiometabolic syndrome, contribute to altered insulin/IGF-1 signaling pathways and reactive oxygen species formation to induce endothelial dysfunction and cardiovascular disease. This review examines currently understood mechanisms underlying the development of resistance to the metabolic actions of insulin in cardiovascular as well as skeletal muscle tissue.     

Inflammation and oxidative stress in vertebrate host-parasite systems

Innate, inflammation-based immunity is the first line of vertebrate defence against micro-organisms. Inflammation relies on a number of cellular and molecular effectors that can strike invading pathogens very shortly after the encounter between inflammatory cells and the intruder, but in a non-specific way. Owing to this non-specific response, inflammation can generate substantial costs for the host if the inflammatory response, and the associated oxygen-based damage, get out of control. This imposes strong selection pressure that acts to optimize two key features of the inflammatory response: the timing of activation and resolution (the process of downregulation of the response). In this paper, we review the benefits and costs of inflammation-driven immunity. Our aim is to emphasize the importance of resolution of inflammation as a way of maintaining homeostasis against oxidative stress and to prevent the 'horror autotoxicus' of chronic inflammation. Nevertheless, host immune regulation also opens the way to pathogens to subvert host defences. Therefore, quantifying inflammatory costs requires assessing (i) short-term negative effects, (ii) delayed inflammation-driven diseases, and (iii) parasitic strategies to subvert inflammation.     

Differential protection against oxidative stress and nitric oxide overproduction in cardiovascular and pulmonary systems by propofol during endotoxemia

Background  

Both overproduction of nitric oxide (NO) and oxidative injury of cardiovascular and pulmonary systems contribute to fatal cardiovascular depression during endotoxemia. We investigated in the present study the relative contribution of oxidative stress and NO to cardiovascular depression during different stages of endotoxemia, and delineated their roles in cardiovascular protective effects of a commonly used anesthetic propofol during endotoxemia.     

Antioxidant S-allylcysteine prevents gentamicin-induced oxidative stress and renal damage

Acute renal failure (ARF) is a major complication of gentamicin (GM) treatment, which is effective against gram-negative infections. Since experimental evidence suggests a role of reactive oxygen species (ROS) in GM-induced ARF, in this work we studied the effect of a garlic-derived compound, S-allylcysteine (SAC), which is a free radical scavenger, on GM-induced nephrotoxicity. In rats treated with GM (70 mg/kg/12 h/4 days/s.c.), ARF was evident by the: (i) decrease in creatinine clearance and increase in blood urea nitrogen, (ii) decrease in blood glutathione peroxidase (GPx) activity and increase in urinary excretion of N-acetyl-beta-D-glucosaminidase and total protein, and (iii) necrosis of proximal tubular cells. These alterations were prevented by SAC treatment (250 mg/kg/i.p. 24 h before the first dose of GM and 125 mg/kg/12 h/4 days along GM-treatment). Furthermore, SAC prevented the GM-induced oxidative stress (protein carbonyl groups) and the decrease in manganese superoxide dismutase (Mn-SOD), GPx, and glutathione reductase (GR) activities in renal cortex. In conclusion, SAC ameliorates the GM-induced ARF by a mechanism related, at least in part, to its ability to decrease oxidative stress and to preserve antioxidant enzymes activity in renal cortex.     

Favorable balance of anti-oxidant/pro-oxidant systems and ablated oxidative stress in Brown Norway rats in renal ischemia-reperfusion injury

Oxidative stress is important in the pathogenesis of renal ischemia-reperfusion (IR) injury; however whether imbalances in reactive oxygen production and disposal account for susceptibility to injury is unclear. The purpose of this study was to compare necrosis, apoptosis, and oxidative stress in IR-resistant Brown Norway rats vs. IR-susceptible Sprague-Dawley (SD) rats in an in vivo model of renal IR injury. As superoxide (O₂^·−) interacts with nitric oxide (NO) to form peroxynitrite, inducible NO synthase (iNOS) and nitrotyrosine were also examined. Renal IR was induced in SD and BN rats by bilateral clamping of renal arteries for 45 min followed by reperfusion for 24 h (SD 24 and BN 24, respectively). BN rats were resistant to renal IR injury as evidenced by lower plasma creatinine and decreased acute tubular necrosis. TUNEL staining analysis demonstrated significantly decreased apoptosis in the BN rats vs. SD rats after IR. Following IR, O₂^·− levels were also significantly lower in renal tissue of BN rats vs. SD rats (P < 0.05) in conjunction with a preservation of the O₂^·− dismutating protein, CuZn superoxide dismutase (CuZn SOD) (P < 0.05). This was accompanied by an overall decrease in 4-hydroxynonenal adducts in the BN but not SD rats after IR. BN rats also displayed lower iNOS expression (P < 0.05) resulting in lower tissue NO levels and decreased nitrotyrosine formation (P < 0.01) following IR. Collectively these results show that the resistance of the BN rat to renal IR injury is associated with a favorable balance of oxidant production vs. oxidant removal. This work was supported in part by a Medical College of Wisconsin-Research Affairs Committee Grant to V. Nilakantan, and by divisional funds to V. Nilakantan and B.D. Shames.     

Developmental programming of cardiovascular dysfunction by prenatal hypoxia and oxidative stress

Fetal hypoxia is a common complication of pregnancy. It has been shown to programme cardiac and endothelial dysfunction in the offspring in adult life. However, the mechanisms via which this occurs remain elusive, precluding the identification of potential therapy. Using an integrative approach at the isolated organ, cellular and molecular levels, we tested the hypothesis that oxidative stress in the fetal heart and vasculature underlies the molecular basis via which prenatal hypoxia programmes cardiovascular dysfunction in later life. In a longitudinal study, the effects of maternal treatment of hypoxic (13% O(2)) pregnancy with an antioxidant on the cardiovascular system of the offspring at the end of gestation and at adulthood were studied. On day 6 of pregnancy, rats (n = 20 per group) were exposed to normoxia or hypoxia ± vitamin C. At gestational day 20, tissues were collected from 1 male fetus per litter per group (n = 10). The remaining 10 litters per group were allowed to deliver. At 4 months, tissues from 1 male adult offspring per litter per group were either perfusion fixed, frozen, or dissected for isolated organ preparations. In the fetus, hypoxic pregnancy promoted aortic thickening with enhanced nitrotyrosine staining and an increase in cardiac HSP70 expression. By adulthood, offspring of hypoxic pregnancy had markedly impaired NO-dependent relaxation in femoral resistance arteries, and increased myocardial contractility with sympathetic dominance. Maternal vitamin C prevented these effects in fetal and adult offspring of hypoxic pregnancy. The data offer insight to mechanism and thereby possible targets for intervention against developmental origins of cardiac and peripheral vascular dysfunction in offspring of risky pregnancy.     

Oxidative stress in patients with cardiovascular disease and chronic renal failure

Abstract

Oxidative response regulates many physiological response in human health, but if not properly regulated it could also lead to a number of deleterious effects. The importance of oxidative stress injury depends on the molecular target, the severity of the stress, and the mechanism by which the oxidative stress is imposed: it has been implicated in several diseases including cancer, neurodegenerative diseases, malaria, rheumatoid arthritis and cardiovascular and kidney disease. Most of the common diseases, such as hypertension, atherosclerosis, heart failure, and renal dysfunction, are associated with vascular functional and structural alterations including endothelial dysfunction, altered contractility, and vascular remodeling. Common to these processes is increased bioavailability of reactive oxygen species (ROS), decreased nitric oxide (NO) levels, and reduced antioxidant capacity. Oxidative processes are up-regulated also in patients with chronic renal failure (CRF) and seem to be a cause of elevated risk of morbidity and mortality in these patients.

In this review, we highlight the role of oxidative stress in cardiovascular and renal disease.     

Evaluation of oxidative stress markers and cardiovascular risk factors in Fabry Disease patients

Fabry Disease, an X-linked inborn error of metabolism, is characterized by progressive renal insufficiency, with cardio and cerebrovascular involvement. Homocysteine (Hcy) is considered a risk factor for vascular diseases, but the mechanisms by which it produces cardiovascular damage are still poorly understood. Regarding the vascular involvement in FD patients, the analysis of factors related to thromboembolic events could be useful to improving our understanding of the disease. The aim of this study was to evaluate plasma Hcy and other parameters involved in the methionine cycle, as well as oxidative stress markers. The sample consisted of a group of 10 male FD patients and a control group of 8 healthy individuals, paired by age. Venous blood was collected for Hcy determination, molecular analysis, identification of thiobarbituric acid reactive substances, total glutathione and antioxidant enzymes activity, as well as vitamins quantification. Comparative analysis of FD patients versus the control group indicated hyperhomocysteinemia in 8 of the 10 FD patients, as well as a significant increase in overall glutathione levels and catalase activity. It is inferred that FD patients, apart from activation of the antioxidant system, present increased levels of plasma Hcy, although this is probably unrelated to common alterations in the methionine cycle.     

Role of angiotensin II and oxidative stress on renal aquaporins expression in hypernatremic rats

The aim of this study was to assess whether endogenous Ang II and oxidative stress produced by acute hypertonic sodium overload may regulate the expression of aquaporin-1 (AQP-1) and aquaporin-2 (AQP-2) in the kidney. Groups of anesthetized male Sprague–Dawley rats were infused with isotonic saline solution (control) or with hypertonic saline solution (Na group, 1 M NaCl), either alone or with losartan (10 mg kg^?1) or tempol (0.5 mg min^?1 kg^?1) during 2 h. Renal function parameters were measured. Groups of unanesthetized animals were injected intraperitoneally with hypertonic saline solution, with or without free access to water intake, Na+W, and Na?W, respectively. The expression of AQP-1, AQP-2, Ang II, eNOS, and NF-kB were evaluated in the kidney by Western blot and immunohistochemistry. AQP-2 distribution was assessed by immunofluorescence. Na group showed increased natriuresis and diuresis, and Ang II and NF-kB expression, but decreased eNOS expression. Losartan or tempol enhanced further the diuresis, and AQP-2 and eNOS expression, as well as decreased Ang II and NF-kB expression. Confocal immunofluorescence imaging revealed labeling of AQP-2 in the apical plasma membrane with less labeling in the intracellular vesicles than the apical membrane in kidney medullary collecting duct principal cells both in C and Na groups. Importantly, our data also show that losartan and tempol induces a predominantly accumulation of AQP-2 in intracellular vesicles. In unanesthetized rats, Na+W group presented increased diuresis, natriuresis, and AQP-2 expression (112?±?25 vs 64?±?16; *p?<?0.05). Water deprivation increased plasma sodium and diuresis but decreased AQP-2 (46?±?22 vs 112?±?25; §p?<?0.05) and eNOS expression in the kidney. This study is a novel demonstration that renal endogenous Ang II–oxidative stress, induced in vivo in hypernatremic rats by an acute sodium overload, regulates AQP-2 expression.     

Lipoic acid ameliorates oxidative stress and renal injury in alloxan diabetic rabbits

The therapeutic potential of lipoic acid (LA) in diabetes and diabetic nephropathy treatment was elucidated. Alloxan diabetic rabbits were treated daily for three weeks with either 10 or 50 mg of LA per kg body weight (i.p.). The following parameters were measured: 1) serum glucose, urea, creatinine and hydroxyl free radical (HFR) levels; 2) blood glutathione redox state; 3) urine albumin concentration; 4) hepatic and renal HFR levels, GSH/GSSG ratios, cysteine contents and the activities of the enzymes of glutathione metabolism; and 5) the activity of renal NADPH oxidase. Histological studies of kidneys were also performed. The treatment of diabetic rabbits with 50 mg of LA resulted in lethal hypoglycaemia in 50% of animals studied. Although the low dose of LA did not change serum glucose concentration, it decreased serum urea and creatinine concentrations, attenuated diabetes-induced decline in GSH/GSSG ratio and abolished hydroxyl free radicals accumulation in serum, liver and kidney cortex. LA did not change the activities of the enzymes of glutathione metabolism, but it elevated hepatic content of cysteine, which limits the rate of glutathione biosynthesis. Moreover, LA lowered urine albumin concentration and attenuated glomerulopathy characteristic of diabetes. However, it did not affect diabetes-stimulated activity of renal NADPH oxidase. In view of these data, it is concluded that low doses of LA might be useful for the therapy of diabetes and diabetic nephropathy. Beneficial action of LA seems to result mainly from direct scavenging of HFR and restoring glutathione redox state due to elevation of intracellular cysteine levels.     

The JaICA-genox oxidative stress profile--an overview on the profiling technique in the oxidative stress assessment and management

It is widely accepted that oxidative stress (OS) is a major causative factor for many of the age-related dysfunctions and specific diseases. Since the oxidative stress state (OSS) of an individual depends on hereditary, dietary, and environmental factors, there is a large heterogeneity in the population that may be related to disease incidence and longevity. Hence there is a need to assess how well an individual is coping against OS. The Japan Institute for the Control of Aging (JaICA) and Genox have jointly developed a profiling technique to measure the "Oxidative Stress Profiles (JaICA-Genox OSP)" of individuals and laboratory test animals. The JaICA-Genox OSP consists of about 45 different assays measuring the levels of oxidative damage in lipids and nucleic acids, and the antioxidant defenses in the serum. In addition, several bio-markers for cardiovascular disease risk are also measured, and assays to measure specific age- and sex-related hormones in the serum and urine, and race elements in serum, urine, and drinking water are also undertaken. This overview discusses the designing of the JaICA-Genox OSP and its application in the testing of human subjects.     

The effects of progressive exercise on cardiovascular function in elite athletes: focus on oxidative stress

Some side-effects of excessive physical training are ascribed to reactive oxygen species production. In this work we investigated the effects of progressively imposed maximal physical effort (levels I to V), using progressive maximal exercise test, on peripheral blood lactate, NO (through NO2-), superoxide anion (O2-) and methemoglobin (MetHb) in a group of 19 elite soccer players. Blood lactate (mmol/L) was increased (4.55, level V vs. resting level, 1.95). The basal production of NO2- was in the direct relation with O2 consumption. Significant increase (p<0.05) in O2- values at effort level I (4.18) as compared to the resting value (4.01), and the significant increase (p<0.01 or p<0.05) in the MetHb (%) was found between II (18.79) and III (19.63) or between II and IV (19.24) effort levels, respectively. The regression lines of NO2- and O2- crossed at the level of the respiratory compensation point (RC), suggesting that RC could be of a crucial importance not only in the anaerobic and aerobic metabolism but in mechanisms of signal transductions as well. The results could be of the theoretical interest and also useful in designing an athlete training strategy.     

Effects of estradiol on renal cyclic guanosine monophosphate and oxidative stress in spontaneously hypertensive rats

Background: Evidence suggests that estradiol offers protection against the development of cardiovascular and renal pathologies, although the mechanisms involved are still under investigation. The nitric oxide (NO) pathway regulates blood pressure and kidney function, and estradiol is associated with increases in NO bioavailability. We hypothesized that in female spontaneously hypertensive rats (SHRs), estra-diol increases NO bioavailability, activates the NO synthase (NOS) pathway, and suppresses superoxide production compared with rats that underwent ovariectomy (OVX).Objective: The goal of this study was to determine whether estradiol regulates the NO/cyclic guanosine monophosphate (cGMP) pathway and superoxide levels in the kidneys of female SHR.Methods: Three types of SHRs were studied: gonad-intact females, OVX rats, and OVX rats with estra-diol replacement (OVX+E). Renal cortical cGMP levels were measured to assess NO bioavailability. NOS enzymatic activity, NOS protein expression, basal superoxide production, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity were measured in the renal cortex.Results: Fifty-six SHRs were included in the study (17 intact females, 21 OVX rats, 18 OVX+E rats). Mean (SEM) cGMP levels were significantly lower in the renal cortex of OVX rats (0.03 [0.008] pmol/mg, n = 5) than in intact females (0.1 [0.02] pmol/mg, n = 6; P < 0.05), and estradiol restored cGMP levels to those seen in intact females (0.1 [0.01] pmol/mg, n = 5; P < 0.05). Despite a decrease in cGMP following OVX, renal cortical NOS activity, NOS1 and NOS3 protein expression, and the phosphorylation status of NOS3 were comparable among the 3 groups (n = 7–9 per group). However, mean basal superoxide production in the renal cortex was higher in OVX rats (3.2 [0.3] cpm/mg, n = 12) than in intact females (1.9 [0.3] cpm/mg, n = 8; P < 0.05) and lower in OVX+E rats (1.3 [0.3] cpm/mg, n = 9; P < 0.05). Mean NADPH oxidase activity was comparable in the renal cortex of intact females and OVX rats (81 [4] and 83 [12] cpm/35 μg, respectively [n = 5 per group]). OVX+E rats had significantly lower mean renal cortical NADPH oxidase activity than did rats in the other groups (45 [6] cpm/35 μg, n = 6; P < 0.05), and the decrease in activity was accompanied by a decrease in p22^phox protein expression.Conclusions: In vivo manipulations of estradiol levels influenced renal cortical NO bioavailability, as assessed indirectly by cGMP measurements. The decrease in cGMP following OVX was not due to alterations in the activity or expression of NOS.     

Lipotoxicity in renal proximal tubular cells: Relationship between endoplasmic reticulum stress and oxidative stress pathways

Hyperlipidemia in the general population has been linked to the development of chronic kidney disease with both oxidative and endoplasmic reticulum stress implicated. Physiological levels (50-300 µmol/L) of saturated fatty acids such as palmitic acid (PA) cause cytotoxicity in vitro. We investigated cell type- and stimulus-specific signaling pathways induced by PA in renal proximal tubular cells and whether oxidative stress leads to ER stress or vice versa and which pathways predominate in signaling for PA-induced apoptosis and necrosis. NRK-52E cells were incubated with PA or hydrogen peroxide (H₂O₂) combined with SP600125 which blocks c-Jun N-terminal kinase (JNK) activation; salubrinal, which maintains eukaryotic initiation factor 2α in its phosphorylated state and the antioxidant EUK-134 - a superoxide dismutase mimetic with catalase activity. We found that (i) PA causes both oxidative and ER stress leading to apoptosis which is mediated by phosphorylated JNK; (ii) oxidant-induced apoptosis generated by H₂O₂ involves ER stress signaling and CHOP expression; (iii) the ER stress mediated by PA is largely independent of oxidative stress; (iv) in contrast, the apoptosis produced by PA is mediated partly via oxidative stress. PA-mediated cell signaling in renal NRK-52E cells therefore differs from that identified in neuronal, hepatic and pancreatic beta cells.     

Mitochondrial superoxide production during oxalate-mediated oxidative stress in renal epithelial cells

Crystals of calcium oxalate monohydrate (COM) in the renal tubule form the basis of most kidney stones. Tubular dysfunction resulting from COM-cell interactions occurs by mechanism(s) that are incompletely understood. We examined the production of reactive oxygen intermediates (ROI) by proximal (LLC-PK1) and distal (MDCK) tubular epithelial cells after treatment with COM (25–250 μg/ml) to determine whether ROI, specifically superoxide (O₂^•−), production was activated, and whether it was sufficient to induce oxidative stress. Employing inhibitors of cytosolic and mitochondrial systems, the source of ROI production was investigated. In addition, intracellular glutathione (total and oxidized), energy status (ATP), and NADH were measured. COM treatment for 1–24 h increased O₂^•− production 3–6-fold as measured by both lucigenin chemiluminescence in permeabilized cells and dihydrorhodamine fluorescence in intact cells. Using selective inhibitors we found no evidence of cytosolic production. The use of mitochondrial probes, substrates, and inhibitors indicated that increased O₂^•− production originated from mitochondria. Treatment with COM decreased glutathione (total and redox state), indicating a sustained oxidative insult. An increase in NADH in COM-treated cells suggested this cofactor could be responsible for elevating O₂^•− generation. In conclusion, COM increased mitochondrial O₂^•− production by epithelial cells, with a subsequent depletion of antioxidant status. These changes may contribute to the reported cellular transformations during the development of renal calculi.     

Impact of cardiovascular risk factors on oxidative stress and DNA damage in a high risk Mediterranean population

Abstract

The impact of classic cardiovascular risk factors on oxidative stress status in a high-risk cardiovascular Mediterranean population of 527 subjects was estimated. Oxidative stress markers (malondialdehyde, 8-oxo-7′8′-dihydro-2′-deoxyguanosine, oxidized/reduced glutathione ratio) together with the activity of antioxidant enzyme triad (superoxide dismutase, catalase, glutathione peroxidase) were analysed in circulating mononuclear blood cells. Malondialdehyde, oxidized glutathione and the ratio of oxidized to reduced glutathione were significantly higher while catalase and glutathione peroxidase activities were significantly lower in high cardiovascular risk participants than in controls. Statistically significant differences were obtained after additional multivariate control for sex, age, obesity, diabetes, lipids and medications. Among the main cardiovascular risk factors, hypertension was the strongest determinant of oxidative stress in high risk subjects studied at a primary prevention stage.