Increased Xanthine Oxidase Research Articles

Oxidative stress in the pathogenesis of type 1 diabetes: the role of adipocyte xanthine oxidase

Rationale. According to modern understanding, oxidative stress plays an essential role in the underlying mechanisms for the emergence of type 1 and type 2 diabetes and development of complications in these conditions. The sources of reactive oxygen species in diabetes are protein glycosylation, mitochondrial respiratory chain, membrane-bound NADPH oxidase, and other enzymes. An important enzymatic source of the superoxide anion radical and Н2О2 is xanthine oxidoreductase. Under physiological conditions, it exists mainly in the xanthine dehydrogenase form and may be reversibly or irreversibly converted to xanthine oxidase, following oxidative modification with formation of disulfide bonds in the protein molecule. In rodents, xanthine oxidoreductase in adipose tissue is expressed at a higher rate, as opposed to in other tissues. The aim of the study was to establish the role of xanthine oxidase in development of oxidative stress in rat adipocytes in experimental type 1 diabetes. Materials and methods. The study was conducted in male Wistar rats with experimental diabetes induced by two different diabetogenic agents – alloxan and streptozotocin. Serum concentration of insulin in the control and experimental rats was determined by the immunoradiometric assay. The levels of glucose and uric acid were measured by the enzymatic methods. The concentration of lipid hydroperoxides, primary products of lipid peroxidation, was detected by the FOX-2 method. The activity of xanthine oxidase in isolated adipocytes of epididymal adipose tissue and the expression of xanthine dehydrogenase mRNA were determined by fluorometry. Results. The rats from the experimental group developed hyperglycemia-induced oxidative stress. The rise in the lipid hydroperoxide concentration in adipocytes was observed against the backdrop of the increased xanthine oxidase activity. The boost in the enzymatic activity under oxidative stress in adipocytes of the experimental rats was accompanied by the increase in the proportion of the xanthine oxidase activity in the total xanthine dehydrogenase plus oxidase activity. It resulted in the elevated xanthine oxidase/xanthine dehydrogenase activity ratio. Oxidative stress in rat adipocytes with experimental type 1 diabetes caused oxidative post-translational modification of the enzyme and its conversion from the xanthine dehydrogenase form to the xanthine oxidase one. It resulted in the subsequent increase in reactive oxygen species production. The inhibitor of xanthine oxidase reduced the level of lipid hydroperoxides in rat adipocytes. Thus, xanthine oxidase may be a potential target to protect from oxidative stress in rat adipose tissue in type 1 diabetes. Conclusions. Oxidative stress in adipose tissue of the rats with alloxan- and streptozotocin-induced diabetes is determined, to a certain extent, by the increased expression of xanthine dehydrogenase mRNA as well as by post-translational oxidative modification of the enzyme activity from dehydrogenase to oxidase. Allopurinol, the inhibitor of xanthine oxidase, decreases the alloxan-induced elevated level of lipid hydroperoxides in rat serum and isolated adipocytes. It indicates a crucial role of xanthine oxidase in development of oxidative stress in adipocytes in experimental type 1 diabetes.

IFN-γ regulates xanthine oxidase-mediated iNOS-independent oxidative stress in maneb- and paraquat-treated rat polymorphonuclear leukocytes.

Maneb (MB) and paraquat (PQ) provoke oxidative stress-mediated cell damage. Role of xanthine oxidase (XO) in oxidative stress and its association with nitric oxide (NO)/NO synthase (NOS) have been widely reported. While inducible NOS (iNOS) is implicated in MB+PQ-induced toxicity in rat polymorphonuclear leukocytes (PMNs), role of XO and its alliance with iNOS have not yet been established. The study investigated the role of XO in MB+PQ-induced oxidative stress in rat PMNs and its regulation by iNOS and inflammatory cytokines. MB+PQ-augmented reactive oxygen species (ROS), superoxide, nitro-tyrosine, lipid peroxidation (LPO), and nitrite levels along with the catalytic activity of iNOS, superoxide dismutase (SOD), and XO. XO inhibitor, allopurinol (AP), alleviated MB+PQ-induced changes except nitrite content and iNOS activity. Conversely, an iNOS inhibitor, aminoguanidine, mitigated MB+PQ-induced LPO, nitrite, iNOS, and nitro-tyrosine levels; however, no change was observed in ROS, SOD, and XO. Nuclear factor-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), tumor necrosis factor-alpha (TNF-α) inhibitor, pentoxyfylline, and an anti-inflammatory agent, dexamethasone, attenuated MB+PQ-induced increase in XO, superoxide, and ROS with parallel reduction in the expression of interferon-gamma (IFN-γ), TNF-α, and interleukin-1β (IL-1β) in rat PMNs. Exogenous IFN-γ, TNF-α, and IL-1β enhanced superoxide, ROS, and XO in the PMNs of control and MB+PQ-treated rats; however, IFN- γ was found to be the most potent inducer. Moreover, AP ameliorated cytokine-induced free radical generation and restored XO activity towards normalcy. The results thus demonstrate that XO mediates oxidative stress in MB+PQ-treated rat PMNs via iNOS-independent but cytokine (predominantly IFN-γ)-dependent mechanism.

Allopurinol as a therapeutic option in cardiovascular disease.

Epidemiological studies indicate that hyperuricaemia is an independent risk factor for cardiovascular disease. Alongside uric acid formation, increased xanthine oxidase activity also results in the formation of oxidative free radicals and superoxide particles. Oxidative stress significantly contributes to the development of cardiovascular disease, including endothelial cell dysfunction, atherosclerosis, vascular calcification and impaired myocardial energetics. Allopurinol, a competitive xanthine oxidase inhibitor, in addition to reducing serum uric acid levels, can act as a free radical scavenger. Although traditionally used for the management of gout, there has been renewed interest in the role of allopurinol in the management of cardiovascular disease. In this review, we summarise the role of the xanthine oxidase pathway in the generation of oxidative stress and evaluate the current body of evidence assessing the clinical effects of allopurinol in patients with cardiovascular disease. A number of small clinical studies have shown a beneficial effect of allopurinol in reducing ischemia-reperfusion injury in the setting of bypass surgery and coronary angioplasty. Additionally, studies in heart failure indicate a potential favourable effect of allopurinol on endothelial dysfunction, LV function and haemodynamic indices, particularly in those with raised serum uric acid levels. Whilst this cheap and readily available pharmacological option may offer a very cost effective therapeutic option, large-scale prospective studies are required to better delineate its role in reducing hard clinical end-points.

Metabolic Profiling of Systemic Lupus Erythematosus and Comparison with Primary Sjögren’s Syndrome and Systemic Sclerosis

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease which can affect most organ systems including skin, joints and the kidney. Clinically, SLE is a heterogeneous disease and shares features of several other rheumatic diseases, in particular primary Sjögrens syndrome (pSS) and systemic sclerosis (SSc), why it is difficult to diagnose The pathogenesis of SLE is not completely understood, partly due to the heterogeneity of the disease. This study demonstrates that metabolomics can be used as a tool for improved diagnosis of SLE compared to other similar autoimmune diseases. We observed differences in metabolic profiles with a classification specificity above 67% in the comparison of SLE with pSS, SSc and a matched group of healthy individuals. Selected metabolites were also significantly different between studied diseases. Biochemical pathway analysis was conducted to gain understanding of underlying pathways involved in the SLE pathogenesis. We found an increased oxidative activity in SLE, supported by increased xanthine oxidase activity and an increased turnover in the urea cycle. The most discriminatory metabolite observed was tryptophan, with decreased levels in SLE patients compared to control groups. Changes of tryptophan levels were related to changes in the activity of the aromatic amino acid decarboxylase (AADC) and/or to activation of the kynurenine pathway.

Weight Loss Mediated Reduction in Xanthine Oxidase Activity and Uric Acid Clearance in Adolescents with Severe Obesity.

Increased xanthine oxidase (XO) activity and uric acid levels are known to be associated with obesity and hypertension; however, it is not known if obesity is directly responsible for these associations in youth. This study investigated the effect of weight loss on XO activity, uric acid, and their relationship to blood pressure change in obese youth to provide greater insight on how obesity increases cardiovascular risk. This was an ancillary study in which 16 adolescents (mean age 15 ± 2 years) received meal replacement therapy over a period of four weeks. Outcomes measured at baseline and after intervention included weight, blood pressure, XO activity, plasma uric acid, uric acid clearance, and creatinine clearance. After the meal replacement intervention, participants experienced reductions in body weight (109.2 ± 16 kg vs. 105.2 ± 14 kg, p < 0.0001) and BMI (38.7 ± 4 kg vs. 37.4 ± 3 kg, p < 0.0001). Plasma XO activity was reduced by 9.8% (p = 0.016). Uric acid clearance was decreased by 39% (p = 0.006). SBP (systolic blood pressure) and plasma uric acid concentrations were reduced but did not achieve statistical significance (p = 0.34 and 0.38, respectively). DBP (diastolic blood pressure) was unchanged (p = 0.86). No significant relationships were found between changes in blood pressure and changes in either XO activity or plasma uric acid levels. Weight loss led to decreases in uric acid production by lowering XO activity and decreases in uric acid clearance by reducing glomerular filtration (GF) and increasing reabsorption. Changes in XO activity and uric acid levels did not correlate with changes in blood pressure.

Poor maternal nutrition and accelerated postnatal growth induces an accelerated aging phenotype and oxidative stress in skeletal muscle of male rats.

ABSTRACT‘Developmental programming’, which occurs as a consequence of suboptimal in utero and early environments, can be associated with metabolic dysfunction in later life, including an increased incidence of cardiovascular disease and type 2 diabetes, and predisposition of older men to sarcopenia. However, the molecular mechanisms underpinning these associations are poorly understood. Many conditions associated with developmental programming are also known to be associated with the aging process. We therefore utilized our well-established rat model of low birth weight and accelerated postnatal catch-up growth (termed ‘recuperated’) in this study to establish the effects of suboptimal maternal nutrition on age-associated factors in skeletal muscle. We demonstrated accelerated telomere shortening (a robust marker of cellular aging) as evidenced by a reduced frequency of long telomeres (48.5-8.6 kb) and an increased frequency of short telomeres (4.2-1.3 kb) in vastus lateralis muscle from aged recuperated offspring compared to controls. This was associated with increased protein expression of the DNA-damage-repair marker 8-oxoguanine-glycosylase (OGG1) in recuperated offspring. Recuperated animals also demonstrated an oxidative stress phenotype, with decreased citrate synthase activity, increased electron-transport-complex activities of complex I, complex II-III and complex IV (all markers of functional mitochondria), and increased xanthine oxidase (XO), p67phox and nuclear-factor kappa-light-chain-enhancer of activated B-cells (NF-κB). Recuperated offspring also demonstrated increased antioxidant defense capacity, with increased protein expression of manganese superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD), catalase and heme oxygenase-1 (HO1), all of which are known targets of NF-κB and can be upregulated as a consequence of oxidative stress. Recuperated offspring also had a pro-inflammatory phenotype, as evidenced by increased tumor necrosis factor-α (TNFα) and interleukin-1β (IL1β) protein levels. Taken together, we demonstrate, for the first time to our knowledge, an accelerated aging phenotype in skeletal muscle in the context of developmental programming. These findings may pave the way for suitable interventions in at-risk populations.

Antihyperuricemic activities of an ethanolic and aqueous extract of Walnut (Juglans regia L.) shell and a new aldehyde xanthine oxidase inhibitor

SummaryHyperuricemia is a common metabolic disorder disease in human and is associated with increased xanthine oxidase (XOD) activity. This study was aimed to evaluate the antihyperuricemic activities of an ethanolic and aqueous extract of walnut (Juglans regia L.) shell in vivo and obtain active compounds with high xanthine oxidase inhibitory (XOI) activities and distinct chemical structures form allopurinol in vitro. Finally, the structure–XOI activity relationship of the active compound was further discussed based on the molecular docking. The in vivo antihyperuricemic study indicated that the walnut shell extract (WSE) could decrease the serum uric acid levels significantly (20‐days treatment, P &lt; 0.05; 30‐days treatment, P &lt; 0.01). And a new aldehyde XOD inhibitor with high XOI activity was obtained through XOI activity‐guided purification in vitro. The studies of structure–XOI activity relationship and molecular docking indicated that the synergy of aldehyde group, double bond and hydroxyl group at C‐4 in p‐coumaric aldehyde was the critical contributor for its high XOI activity.

Study of serum uric acid and creatinine in hypertensive disorders of pregnancy.

BackgroundRenal dysfunction, increased xanthine oxidase activity and oxidative stress in placenta contributes to the elevated uric acid levels in preeclampsia (PE).ObjectiveTo determine serum uric acid and creatinine in hypertensive disorders of pregnancy and correlate with fetal outcome.Materials and MethodsPregnant women ≥32 weeks of gestation. Study population included 3 groups, 31 normotensive pregnant (NP) women as controls, 30 pregnant women with gestational hypertension (GH) and 30 with PE.ResultSerum uric acid and creatinine levels were significantly elevated in PE (6.26±1.19 and 0.94±0.26 mg/dL) when compared with Pregnancy induced hypertension (PIH) (4.27± 1.0 and 0.66 ±0.19 mg/dL) and NP (4.25 ± 0.8 and 0.63± 0.13 mg/dL) (P-value <0.001 and <0.001) respectively. Receiver operation characteristics curves demonstrated greater sensitivity and specificity for uric acid (86.7% and 83.9%, respectively) in PE than for creatinine (80% and 77.4%, respectively). Uric acid had strong and negative correlation with fetal birth weight in PE (r = −0.59, P = 0.006), where as creatinine had negative but weak correlation (r= −0.03, P=0.87).ConclusionSerum uric acid is a better diagnostic and predictive marker for PE and fetal outcome respectively.

Targeted antioxidant treatment decreases cardiac alternans associated with chronic myocardial infarction.

In myocardial infarction (MI), repolarization alternans is a potent arrhythmia substrate that has been linked to Ca2+ cycling proteins, such as sarcoplasmic reticulum Ca2+ ATPase (SERCA2a), located in the sarcoplasmic reticulum. MI is also associated with oxidative stress and increased xanthine oxidase (XO) activity, an important source of reactive oxygen species (ROS) in the sarcoplasmic reticulum that may reduce SERCA2a function. We hypothesize that in chronic MI, XO-mediated oxidation of SERCA2a is a mechanism of cardiac alternans. Male Lewis rats underwent ligation of the left anterior descending coronary artery (n=54) or sham procedure (n=24). At 4 weeks, optical mapping of intracellular Ca2+ and ROS was performed. ECG T-wave alternans (ECG ALT) and Ca2+ transient alternans (Ca2+ALT) were induced by rapid pacing (300-120 ms) before and after the XO inhibitor allopurinol (ALLO, 50 µmol/L). In MI, ECG ALT (2.32±0.41%) and Ca2+ ALT (22.3±4.5%) were significantly greater compared with sham (0.18±0.08%, P<0.001; 0.79±0.32%, P<0.01). Additionally, ROS was increased by 137% (P<0.01) and oxidation of SERCA2a by 30% (P<0.05) in MI compared with sham. Treatment with ALLO significantly decreased ECG ALT (-77±9%, P<0.05) and Ca2+ ALT (-56±7%, P<0.05) and, importantly, reduced ROS (-65%, P<0.01) and oxidation of SERCA2a (-38%, P<0.05). CaMKII inhibition and general antioxidant treatment had no effect on ECG ALT and Ca2+ ALT. These results demonstrate, for the first time, that in MI, increased ROS from XO is a significant cause of repolarization alternans. This suggests that targeting XO ROS production may be effective at preventing arrhythmia substrates in chronic MI.

Effect of smoking on serum xanthine oxidase, malondialdehyde, ascorbic acid and α-tocopherol levels in healthy male subjects.

Objective:To examine the effect of smoking on serum xanthine oxidase, malondialdehyde, α- tocopherol and ascorbic acid levels in healthy adult male subjects.Methods:This cross-sectional comparative study was carried out at Isra University Hyderabad from July 2012 to December 2012. One hundred and twenty apparently healthy adult male subjects (60 smokers and 60 non-smokers) included in present study, were recruited from Jaindal kot, a small village located midway between Hyderabad and Matiari. Serum samples from smokers and non-smokers were analyzed for xanthine oxidase and malondialdehyde levels by standard kit methods, while for ascorbic acid and alpha- tocopherol by spectrophotometric methods.Results:The mean xanthine oxidase and malondialdehyde levels measured in healthy smokers were 0.30±0.05 mg/dl and 37.50±4.05 µmoles/l respectively as against 0.25±0.04 mg/dl and 19.86±2.21µmoles/l in non-smokers. Both xanthine oxidase and malondialdehyde levels were significantly (p<0.001) raised in healthy smokers than in non-smokers. Likewise, mean vitamin E and vitamin C levels were respectively 0.69±0.37 mg/dl and 0.80±0.16 mg/dl in healthy smokers compared to 1.14±0.43 mg/dl and 1.22±0.29 mg/dl in non-smokers. The concentrations of both these vitamins were significantly (p<0.001) lower in smokers than in non-smokers.Conclusion:The results of present study demonstrate that smoking had significantly increased xanthine oxidase and malondialdehyde levels and decreased vitamins C and E (antioxidants) levels. These findings suggest that smokers have to take additional amounts of vitamins C and E in order to avoid deleterious effects of smoking on their health.

Activation of xanthine oxidase mediates intermittent hypoxia‐induced HIF‐2 degradation

We previously showed that IH leads to increased degradation of HIF‐2α via [Ca2+]i activated calpains, which contributes to IH‐induced oxidative stress via insufficient transcription of antioxidant enzymes (J. Nanduri et al. PNAS, 2009). In this study, we examined the mechanisms associated with activation of calpains by IH in PC12 cell cultures. In IH treated PC12 cells, ROS levels as well as calpain activity increased and anti‐oxidant treatment prevented these effects suggesting the involvement of ROS signaling. Pharmacological or genetic blockade of NADPH oxidase 2 (Nox2) had no effect on IH‐evoked calpain activation and HIF‐2α degradation. However, IH markedly increased xanthine oxidase (XO) activity. Allopurinol, a XO inhibitor or silencing of XO by siRNA prevented IH induced HIF‐2α degradation, increased intracellular calcium levels and calpain activity. Systemic adminsitration of allopurinol to rats during the IH exposure prevented the oxidative stress, rescued HIF‐2α degradation in the adrenal medulla and prevented hypertension. These results demonstrate that ROS generated by XO activation mediates IH‐induced HIF‐2α down regulation and suggest that ROS‐induced ROS as a potential mechanism contributing to IH‐induced cardiovascular morbidity.

6-Mercaptopurine-induced histopathological changes and xanthine oxidase expression in rat placenta

The placenta secures the embryo and fetus to the endometrium and releases a variety of steroid and peptide hormones that convert the physiology of a female to that of a pregnant female. Chemical-induced alteration or deviation of placental function in the maternal and extraembryonic tissue can ultimately lead to pregnancy loss, congenital malformation and fetal death. The 6-mercaptopurine (6-MP), an anti-leukemic drug, is known to produce undesired effects on some organs, then the placenta/embryo toxicity of 6-MP was investigated in pregnant rats given 60 mg/kg with two intraperitoneal injections on gestation days (GD) 11 and 12. The rats were sacrificed and their placentas were collected on GD13 or 15. On GD15 small and limb-defected embryos were found in the 6-MP-treated rats. Placental weights were significantly reduced on GD15, as well as a reduced number of cells was detected in the labyrinth zone with both the labyrinth and basal zones having thinned. Cleaved caspase-3-positive cells increased in number in the labyrinth zone, while in the basal zone, glycogen cells reduced with cytolysis. The number of spongiotrophoblasts and trophoblastic giant cells also increased by 6-MP treatment. The 6-MP-treatment resulted in the increased xanthine oxidase (Xdh) expression in the placenta, which gene is related to the ischemic condition of tissues. These data suggest that apoptosis of the labyrinth zone cells may lead to decreased materno-fetal exchange. Moreover, subsequent ischemia in the placental tissue may occur and induce Xdh expression.

Taurine exerts hypoglycemic effect in alloxan-induced diabetic rats, improves insulin-mediated glucose transport signaling pathway in heart and ameliorates cardiac oxidative stress and apoptosis

Hyperlipidemia, inflammation and altered antioxidant profiles are the usual complications in diabetes mellitus. In the present study, we investigated the therapeutic potential of taurine in diabetes associated cardiac complications using a rat model. Rats were made diabetic by alloxan (ALX) (single i.p. dose of 120 mg/kg body weight) and left untreated or treated with taurine (1% w/v, orally, in water) for three weeks either from the day of ALX exposure or after the onset of diabetes. Animals were euthanized after three weeks. ALX-induced diabetes decreased body weight, increased glucose level, decreased insulin content, enhanced the levels of cardiac damage markers and altered lipid profile in the plasma. Moreover, it increased oxidative stress (decreased antioxidant enzyme activities and GSH/GSSG ratio, increased xanthine oxidase enzyme activity, lipid peroxidation, protein carbonylation and ROS generation) and enhanced the proinflammatory cytokines levels, activity of myeloperoxidase and nuclear translocation of NFκB in the cardiac tissue of the experimental animals. Taurine treatment could, however, result to a decrease in the elevated blood glucose and proinflammatory cytokine levels, diabetes-evoked oxidative stress, lipid profiles and NFκB translocation. In addition, taurine increased GLUT 4 translocation to the cardiac membrane by enhanced phosphorylation of IR and IRS1 at tyrosine and Akt at serine residue in the heart. Results also suggest that taurine could protect cardiac tissue from ALX induced apoptosis via the regulation of Bcl2 family and caspase 9/3 proteins. Taken together, taurine supplementation in regular diet could play a beneficial role in regulating diabetes and its associated complications in the heart.

Ginsenoside-Rg1 Protects the Liver against Exhaustive Exercise-Induced Oxidative Stress in Rats

Despite regular exercise benefits, acute exhaustive exercise elicits oxidative damage in liver. The present study determined the hepatoprotective properties of ginsenoside-Rg1 against exhaustive exercise-induced oxidative stress in rats. Forty rats were assigned into vehicle and ginsenoside-Rg1 groups (0.1 mg/kg bodyweight). After 10-week treatment, ten rats from each group performed exhaustive swimming. Estimated oxidative damage markers, including thiobarbituric acid reactive substance (TBARS) (67%) and protein carbonyls (56%), were significantly (P < 0.01) elevated after exhaustive exercise but alleviated in ginsenoside-Rg1 pretreated rats. Furthermore, exhaustive exercise drastically decreased glutathione (GSH) content (∼79%) with concurrent decreased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities. However, these changes were attenuated in Rg1 group. Additionally, increased xanthine oxidase (XO) activity and nitric oxide (NO) levels after exercise were also inhibited by Rg1 pretreatment. For the first time, our findings provide strong evidence that ginsenoside-Rg1 can protect the liver against exhaustive exercise-induced oxidative damage.

The Xanthine Oxidase Inhibitor Allopurinol Results In A Loss Of Cytoprotection Conferred by Pharmacologic Pre-conditioning With Hydrogen Sulfide

Introduction: A growing body of literature has shown that pharmacologic pre-conditioning with hydrogen sulfide (HS) mitigates damage caused by ischemia-reperfusion injury (IRI). However, its protective mechanism remains unclear. As a reversible inhibitor of cytochrome c oxidase, HS reduces ATP synthesis by diminishing oxidative phosphorylation, resulting in increased xanthine oxidase (XO) activity and the generation of reactive oxygen species (ROS). It is hypothesized that this non-lethal level of free radicals is sufficient to upregulate cellular antioxidant enzymes and reduce IRI. Our laboratory has shown that a 10μM dose of the XO inhibitor allopurinol abrogates the protective effects of HS on skeletal muscle in the setting of IRI. However, other studies suggest that allopurinol protects from IRI by directly scavenging free radicals and decreasing ROS production. We hypothesize that higher concentrations of allopurinol are required to restore and complement the protective effects of pharmacologic preconditioning with HS in an in vitro model of IRI. Methods: Murine myoblasts were differentiated into myotubes and then treated with either 10μM HS, 100μM allopurinol, both 10μM HS and 100μM allopurinol, or vehicle alone (non-treated control). The experiment was replicated with a higher concentration of allopurinol (1mM). Cells were exposed to 3h of anoxia followed by 3h of normoxia (21% O2). Parallel control groups were exposed to normoxia for 6 hours. A TUNEL assay was performed to determine the apoptotic index (AI; number of TUNEL-positive cells divided by the total number of cells) for each group. Results: The AI of myotubes treated with 100μM allopurinol alone was unchanged from that of non-treated controls (9.1%±1.1% v. 10.2%±1.4%, p=0.194). For cells treated with 1mM allopurinol alone, the AI was similarly unchanged (9.5%±1.2%, p=0.317). Ten μM HS alone resulted in a significant decrease in AI when compared to non-treated controls (4.0%±0.4%, p<0.001). However, treatment with both 100μM allopurinol and HS resulted in an AI of 11.3%±0.8%, significantly greater than that of myotubes treated with HS alone (p<0.001) and unchanged from non-treated controls (p=0.974). Likewise, treatment with both 1mM allopurinol and HS resulted in an AI of 10.5%±0.9%, significantly greater than that of HS alone (p<0.001) and not significantly different from that of the untreated controls (p=0.448). Conclusions: Even in the presence of increased concentrations of allopurinol, the protective effects of HS in the setting of IRI are lost. Furthermore, in contrast to others' reports, allopurinol alone was found not to have a cytoprotective effect. These data suggest that the protective mechanism of HS is due at least in part to a xanthine oxidase-mediated pathway and the generation of low levels of ROS. These findings importantly expand our understanding of the pathophysiology of IRI and may help to delineate the clinical utility of HS.

Hyperuricaemia, chronic kidney disease, and outcomes in heart failure: potential mechanistic insights from epidemiological data

To determine if the association between hyperuricaemia and poor outcomes in heart failure (HF) varies by chronic kidney disease (CKD). Of the 2645 systolic HF patients in the Beta-Blocker Evaluation of Survival Trial with data on baseline serum uric acid, 1422 had hyperuricaemia (uric acid ≥6 mg/dL for women and ≥8 mg/dL for men). Propensity scores for hyperuricaemia, estimated for each patient, were used to assemble a matched cohort of 630 pairs of patients with and without hyperuricaemia who were balanced on 75 baseline characteristics. Associations of hyperuricaemia with outcomes during 25 months of median follow-up were examined in all patients and in those with and without CKD (estimated glomerular filtration rate of <60 mL/min/1.73 m(2)). Hyperuricaemia-associated hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause mortality and HF hospitalization were 1.44 (1.12-1.85, P = 0.005) and 1.27 (1.02-1.58, P = 0.031), respectively. Hazard ratios (95% CIs) for all-cause mortality among those with and without CKD were 0.96 (0.70-1.31, P = 0.792) and 1.40 (1.08-1.82, P = 0.011), respectively (P for interaction, 0.071), and those for HF hospitalization among those with and without CKD were 0.99 (0.74-1.33, P = 0.942) and 1.49 (1.19-1.86, P = 0.001), respectively (P for interaction, 0.033). Hyperuricaemia has a significant association with poor outcomes in HF patients without CKD but not in those with CKD, suggesting that hyperuricaemia may predict poor outcomes when it is primarily a marker of increased xanthine oxidase activity, but not when it is primarily due to impaired renal excretion of uric acid.

Allopurinol and global left myocardial function in heart failure patients

Background and Aim:Increased xanthine oxidase (XO) activity may contribute to heart failure pathophysiology. This study evaluated whether a XO inhibitor, allopurinol produces clinical and functional benefits in patients with New York Heart Association functional class III to IV heart failure due to systolic dysfunction receiving optimal medical therapy as estimated by global left myocardial function.Patients and Methods:Fifty-nine patients with a diagnosis of chronic heart failure due to coronary heart disease or idiopathic dilated cardiomyopathy and 20 healthy controls who attended the outpatient clinic of cardiology were subjected to full echocardiographic study including left ventricular diastolic and systolic function, and the combined index of myocardial performance [Tei index: isovolumetric relaxation time (IRT) + isovolumetric contraction time (ICT)/ejection time (ET)]. Patients were randomized to allopurinol (300 mg/day) or placebo. Improvement at 36 weeks was assessed using a composite end point comprising global left cardiac function as well as heart failure morbidity and mortality.Results:The percentage of patients characterized as improved, unchanged, or worsened did not differ between those receiving allopurinol or placebo. Allopurinol reduced serum uric acid (SUA) by 1.5 mg/dL (P = 0.001). In a subgroup analysis, patients with elevated SUA (more than 7mg/ dL) responded favorably to allopurinol whereas those with SUA less than 7mg/dL exhibited a trend toward no change. In addition, SUA reduction to allopurinol correlated with favorable clinical and functional response. Within the entire allopurinol patient cohort, those characterized as either improved or unchanged had significantly greater reductions in SUA compared with patients who did not change (P = 0.0007). In placebo patients, lower baseline SUA, but not change in SUA, correlated with improved clinical outcome.Conclusions:Allopurinol did not produce significant clinical and functional improvement in unselected patients with moderate-to-severe heart failure. However, it is suggested that it is useful in patients with elevated SUA in a manner according to degree of SUA reduction. SUA may serve as a valuable biomarker to target heart failure therapy.

The inhibitory effect of raloxifene on lipopolysaccharide-induced nitric oxide production in RAW264.7 cells is mediated through a ROS/p38 MAPK/CREB pathway to the up-regulation of heme oxygenase-1 independent of estrogen receptor

In this study, we demonstrate that raloxifene, a selective estrogen receptor modulator, is a potent inducer of the anti-inflammatory enzyme heme oxygenase-1 (HO-1). In RAW264.7 macrophages, raloxifene induced HO-1 mRNA and protein expression. Pretreatment of ICI182780, an estrogen receptor (ER) antagonist or knock-down of endogenous ERα or ERβ gene by RNA interference failed to reverse raloxifene-mediated HO-1 induction, indicating an estrogen receptor-independent mechanism. Interestingly, the raloxifene-induced HO-1 expression was suppressed by reactive oxygen species (ROS) scavengers, including glutathione, TEMPO, Me(2)SO, 1,10-phenanthroline, or allopurinol. In addition, buthionine sulfoximine, an inhibitor of reduced glutathione synthesis, or Fe 2+/Cu 2+ ions enhanced the positive effect of raloxifene on HO-1 expression. Consistent with these findings, raloxifene induced production of intracellular ROS and increased xanthine oxidase activity in vitro. Additional experiments revealed the involvement of mitogen-activated protein kinase (MAPK) kinase6 and p38 MAPK in the up-regulation of HO-1 by raloxifene and identified p38 MAPK as a downstream effector of ROS. Furthermore, the ROS-p38 MAPK cascade targeted the transcription factor cAMP-responsive element-binding protein (CREB). Finally, the functional significance of HO-1 induction was revealed by raloxifene-mediated inhibition of inducible nitric oxide synthase expression and nitric oxide production, a response reversed by the inhibition of HO-1 protein synthesis or blockade of p38 MAPK or xanthine oxidase activity. Therefore, identification of ROS-p38 MAPK-CREB-linked cascade as cellular relays in raloxifene-mediated HO-1 expression defines the signaling events that could participate in raloxifene-mediated anti-inflammatory response.

Effect of Serum Insulin on the Association Between Hyperuricemia and Incident Heart Failure

Increased serum uric acid (UA) is associated with incident heart failure (HF). However, whether it is a direct effect of UA or an effect of increased xanthine oxidase (XO) is unknown. Because hyperuricemia in hyperinsulinemia is primarily due to impaired renal UA excretion, its association with incident HF would suggest a direct UA effect. In contrast, hyperuricemia in normoinsulinemia is likely due to increased UA production and thus its association with incident HF would suggest an XO effect. To clarify this, we examined the association of hyperuricemia with centrally adjudicated incident HF in Cardiovascular Health Study participants with and without hyperinsulinemia. Of the 5,411 participants ≥ 65 years of age without baseline HF, 1,491 (28%) had hyperuricemia (serum UA ≥ 6 mg/dl for women and ≥ 7 mg/dl for men). Propensity scores for hyperuricemia were estimated using 63 baseline characteristics. Mean serum UA levels were 6.0 and 5.3 mg/dl in those with (n = 2,731) and those without (n = 2,680) hyperinsulinemia (median serum insulin ≥ 13 mU/L), respectively (p < 0.001). Propensity-adjusted hazard ratios (95% confidence intervals) for hyperuricemia-associated incident HF during 8 years of median follow-up were 0.99 (0.83 to 1.18, p = 0.886) and 1.32 (1.04 to 1.67, p = 0.021) for those with and without hyperinsulinemia respectively (p for interaction = 0.014). In conclusion, the absence of an association of hyperuricemia with incident HF in those with hyperinsulinemia (despite a significantly higher mean serum UA) and a significant association in normoinsulinemia suggest that UA has no intrinsic association with incident HF and that it may predict incident HF when it is a marker of increased of XO activity.

Anti-oxidative Effect Of Ginsenoside Rg1 Against Exhaustive Exercise-induced Proteins And Lipids Oxidation In Liver Of Rats

PURPOSE: Usage of ginsenoside Rg1 has been increased in the recent years to treat various metabolic abnormalities due to its pharmacological values. In this study we focused on hepato-protective effects of Rg1 compound against acute exercise-induced changes in glutathione, and proteins and lipids oxidation. METHODS: Healthy Sprague Dawley male rats (n=20) were equally divided into 2 groups. First group served as placebo and second group received purified Rg1 compound at the dose of 0.1 mg/kg b.w. for 8-week. Five rats from each group allowed for exhausted swimming exercise and sacrificed immediately after performance. RESULTS: Elevated protein carbonyls and malondialdehyde (MDA) levels, and decreased glutathione (GSH) levels were noticed after exhausted swimming in placebo group. However, elevated protein carbonyls were significantly (p <0.05) suppressed in Rg1 pretreated group after exercise. Oxidized GSH (GSSG) levels were not significantly changed after exercise in placebo and also in Rg1 treated groups. Interestingly, we found the increased xanthine oxidase (XO) activity after exercise in placebo group, which means increased free radical production in liver. However, XO activity was lowered after exhausted exercise in Rg1 treated rats compared to placebo exercised rats. CONCLUSIONS: This data supports that exhaustive exercise cause oxidative damage to vital organic molecules. In this study we found that this oxidative damage was reversed by Rg1 supplementation, which indicates herbal supplements like Rg1 compounds could be beneficial to recover from possible oxidative damages in athletes.