Xanthine Oxidase Expression Research Articles

Corticosterone Inhibits LPS-Induced NLRP3 Inflammasome Priming in Macrophages by Suppressing Xanthine Oxidase.

Following traumatic insult and associated pathogen infection, innate immunity is activated during the perioperative period, especially the NLRP3 inflammasome in macrophages. The neuroendocrine response is also rapidly activated to regulate excessive inflammation; however, the molecular mechanisms are still not completely clear. This study is aimed at investigating the modulation of NLRP3 inflammasome priming by endogenous glucocorticoids (corticosterone, CORT) and its relationship with xanthine oxidase (XO). RAW264.7 murine macrophages were stimulated with LPS (1 μg/ml). LPS-induced NLRP3 expression was pretreated by CORT at different concentrations (0-900 ng/ml). Then, the effect of higher concentrations of CORT (700 ng/ml) on LPS-induced NLRP3 expression and the effect of allopurinol (250 μg/ml) were observed. Finally, the effects of a CORT antagonist (RU486) on XO expression and activity and NLRP3 expression in macrophages were further analyzed. Supernatant levels IL-1β and IL-18 were measured. The results showed that LPS-induced NLRP3 expression was upregulated further by pretreatment with CORT (300 ng/ml) (P < 0.05); however, higher concentrations of CORT (greater than 700 ng/ml) downregulated NLRP3 expression (P < 0.01) and the expression and activity of XO (P < 0.05 and P < 0.01, respectively). Allopurinol significantly inhibited NLRP3 expression. However, XO expression and activity, NLRP3 expression, and supernatant IL-1β and IL-18 levels were significantly increased in the RU486 group compared with the CORT group. In conclusion, our results suggested that CORT inhibits LPS-induced NLRP3 inflammasome priming in macrophages. The underlying mechanism is related to the modulation of XO expression and activity, which may be involved in priming and activating the NLRP3 inflammasome.

Hereditary hemochromatosis disrupts uric acid homeostasis and causes hyperuricemia via altered expression/activity of xanthine oxidase and ABCG2.

Hereditary hemochromatosis (HH) is mostly caused by mutations in the iron-regulatory gene HFE. The disease is associated with iron overload, resulting in liver cirrhosis/cancer, cardiomegaly, kidney dysfunction, diabetes, and arthritis. Fe2+-induced oxidative damage is suspected in the etiology of these symptoms. Here we examined, using Hfe−/− mice, whether disruption of uric acid (UA) homeostasis plays any role in HH-associated arthritis. We detected elevated levels of UA in serum and intestine in Hfe−/− mice compared with controls. Though the expression of xanthine oxidase, which generates UA, was not different in liver and intestine between wild type and Hfe−/− mice, the enzymatic activity was higher in Hfe−/− mice. We then examined various transporters involved in UA absorption/excretion. Glut9 expression did not change; however, there was an increase in Mrp4 and a decrease in Abcg2 in Hfe−/− mice. As ABCG2 mediates intestinal excretion of UA and mutations in ABCG2 cause hyperuricemia, we examined the potential connection between iron and ABCG2. We found p53-responsive elements in hABCG2 promoter and confirmed with chromatin immunoprecipitation that p53 binds to this promoter. p53 protein was reduced in Hfe−/− mouse intestine. p53 is a heme-binding protein and p53-heme complex is subjected to proteasomal degradation. We conclude that iron/heme overload in HH increases xanthine oxidase activity and also promotes p53 degradation resulting in decreased ABCG2 expression. As a result, systemic UA production is increased and intestinal excretion of UA via ABCG2 is decreased, causing serum and tissue accumulation of UA, a potential factor in the etiology of HH-associated arthritis.

XANTHINE OXIDASE EXPRESSION IN ATHEROSCLEROTIC CAROTID PLAQUE IS ASSOCIATED WITH PLAQUE VULNERABILITY AND EXPRESSION OF CD163

Xanthine oxidase (XO) expression in macrophages has been linked to pathogenesis of atherosclerosis. Recent studies have revealed that macrophages with increased expression of hemoglobin-haptoglobin receptor CD163 promote atherosclerotic plaque instability. We hypothesized that enhanced XO expression

Purine Catabolism Shows a Dampened Circadian Rhythmicity in a High-fat Diet-Induced Mouse Model of Obesity.

High-calorie diet, circadian rhythms and metabolic features are intimately linked. However, the mediator(s) between nutritional status, circadian rhythms and metabolism remain largely unknown. This article aims to clarify the key metabolic pathways bridging nutritional status and circadian rhythms based on a combination of metabolomics and molecular biological techniques. A mouse model of high-fat diet-induced obesity was established and serum samples were collected in obese and normal mice at different zeitgeber times. Gas chromatography/mass spectrometry, multivariate/univariate data analyses and metabolic pathway analysis were used to reveal changes in metabolism. Metabolites involved in the metabolism of purines, carbohydrates, fatty acids and amino acids were markedly perturbed in accordance with circadian related variations, among which purine catabolism showed a typical oscillation. What’s more, the rhythmicity of purine catabolism dampened in the high-fat diet group. The expressions of clock genes and metabolic enzymes in the liver were measured. The mRNA expression of Xanthine oxidase (Xor) was highly correlated with the rhythmicity of Clock, Rev-erbα and Bmal1, as well as the metabolites involved in purine catabolism. These data showed that a high-fat diet altered the circadian rhythm of metabolic pathways, especially purine catabolism. It had an obvious circadian oscillation and a high-fat diet dampened its circadian rhythmicity. It was suggested that circadian rhythmicity of purine catabolism is related to circadian oscillations of expression of Xor, Uox and corresponding clock genes.

Effects of psychological stress on xanthine oxidase expression, activity and related markers in adipose tissue of mice

To investigate the effects of psychological stress on xanthine oxidase (XO) expression, activity and related markers in adipose tissue of mice. Twenty male Kunming mice were randomly divided into two groups (10 in each group), stress group and control group (10 in each group). Stress group were restrained in self-made restraint device for 2 hours per day for 14 days, then blood samples and white adipose tissues(WAT) were collected. The expression levels of XO and NADPH oxidase-4 (Nox-4) in WAT were detected by immunohistochemistry. The expression of XO, Nox-4, antioxidant proteins (manganese superoxide dismutase (Mn SOD), glutathione peroxidase (GSH-Px), and catalase (CAT)), adipocytokines (adiponectin (ADPN), monocyte chemotactic protein 1 (MCP-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)) in WAT were further detected by quantitative PCR. Relative expressions of glucose metabolism (insulin receptor substrate-1(IRS-1) and glucose transporter type 4(GLUT-4)) and thrombin(tissue factor (TF) and plasminogen activator inhibitor 1 (PAI-1))were measured. XO activity and serum concentrations of (triglyceride (TG), total cholesterol (T-Cho), free fatty acid, (FFA), and uric acid (UA)) were detected by ELISA. XO expressed in stress mice inguinal WAT was deeper and more abundant than that of control group, mainly expressed in adipocytes. RT-PCR and ELISA results showed that the levels of XO mRNA, serum XO concentration and the activities of XO enzyme in WAT of stress group were significantly higher than those of control group(P ＜0.01). Compared with control group the concentrations of free fatty acid (FFA) and uric acid (UA) in stress group were increased significantly than in control group (P＜ 0.01). Nox-4 positive cells mainly expressed in adipocytes. The expression of Nox-4 in WAT of stress group was significantly higher(P ＜0.01); The levels of antioxidant proteins (Mn-SOD, GSH-Px, Catalase) in WAT of stress group were significantly lower (P＜ 0.01). WAT in stress group showed a large number of infiltration reactions and inflammatory changes of monocytes, neutrophils, eosinophils and plasma cells. Stress significantly decreased the expression of adiponectin in WAT, and significantly increased the expressions of MCP-1, IL-6 and TNF-α (P＜0.01). The levels of IRS-1 and GLUT-4 in WAT of stress mice were increased significantly (P＜ 0.01). The expressions of TF and PAI-1 in WAT of stress mice and blood concentrations were significantly higher (P＜0.01). Stress can induce excessive expressions of XO in adipose tissue, which eventaully can lead to adipose inflammation, glycometabolism and abnormal prothrombin.

Blueberry extract decreases oxidative stress and improves functional parameters in lungs from rats with pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a condition characterized by an increased resistance of pulmonary vasculature, culminating in an increase in pulmonary pressure. This process involves disturbances in lung redox homeostasis, causing progressive right heart failure. In this context, the use of natural antioxidants, such as those found in blueberries, may represent a therapeutic approach. The aim of this study was to evaluate the effect of blueberry extract (BB) on functional parameters and oxidative stress levels in rat lungs with induced PAH. Forty-eight male Wistar rats (weighing 200 ± 20 g) were randomized into five groups: control, monocrotaline, monocrotaline + BB 50, monocrotaline + BB 100, and monocrotaline + BB 200. PAH was induced by the administration of monocrotaline (60 mg/kg, intraperitoneal). Rats were treated with BB at doses of 50, 100, and 200 mg/kg via gavage for 5 wk (2 wk before monocrotaline and 3 wk after monocrotaline injection). At day 35, rats were submitted to echocardiography and catheterization. They were then sacrificed and lungs were harvested for biochemical analyses. BB increased the E/A ratio of blood flow across the tricuspid valve and tricuspid annular phase systolic excursion, as wells as decreased the mean pulmonary artery pressure of animals compared with the PAH group. Moreover, BB decreased total reactive species concentration and lipid oxidation, reduced activity of nicotinamide adenine dinucleotide phosphate oxidase and expression of xanthine oxidase, increased the activity of superoxide dismutase and restored sulfhydryl content in the animal lungs compared with those in the PAH group. Additionally, BB restored expression of the antioxidant transcriptional factor Nrf2 in the lungs of the animal subjects. Finally, BB normalized the endothelin receptor (ETA/ETB) expression ratio in the animal lungs, which were increased in the PAH group. Intervention with BB mitigated functional PAH outcomes through improvement of the pulmonary redox state. Our results provide a basis for future research on natural antioxidant interventions as a novel treatment strategy in PAH.

The Histone Methyltransferase Setdb2 Modulates Macrophage Phenotype and Uric Acid Production in Diabetic Wound Repair

Macrophage plasticity is critical for normal tissue repair to ensure transition from the inflammatory to the proliferative phase of healing. We examined macrophages isolated from wounds of patients afflicted with diabetes and of healthy controls and found differential expression of the methyltransferase Setdb2. Myeloid-specific deletion of Setdb2 impaired the transition of macrophages from an inflammatory phenotype to a reparative one in normal wound healing. Mechanistically, Setdb2 trimethylated histone 3 at NF-κB binding sites on inflammatory cytokine gene promoters to suppress transcription. Setdb2 expression in wound macrophages was regulated by interferon (IFN) β, and under diabetic conditions, this IFNβ-Setdb2 axis was impaired, leading to a persistent inflammatory macrophage phenotype in diabetic wounds. Setdb2 regulated the expression of xanthine oxidase and thereby the uric acid (UA) pathway of purine catabolism in macrophages, andpharmacologic targeting of Setdb2 or the UApathway improved healing. Thus, Setdb2 regulates macrophage plasticity during normal and pathologic wound repair and is a target for therapeutic manipulation.

Gender effect of hyperuricemia on the development of nonalcoholic fatty liver disease (NAFLD): A clinical analysis and mechanistic study

Background and aimsHyperuricemia is a risk factor for nonalcoholic fatty liver disease (NAFLD), however, the effect of gender on the hyperuricemia-related NAFLD development remains unclear. Here, we evaluated the clinical characteristics of NAFLD patients with hyperuricemia, and experimentally recapitulated this condition in male rats in order to gain insights on the possible impact of gender on the development of NAFLD in patients with hyperuricemia. MethodsThe clinical characteristics of 238 NAFLD patients, together with the impacts of hyperuricemia on the major parameters related to the development of NALFD were analysed. In animal studies, NAFLD with hyperuricemia was induced in male SD rats using high-yeast high-fat diet containing potassium oxonate. The impact of uric acids on liver pathology, and the expression patterns of key molecules involved in the development of NAFLD, including silent information regulator 1 (SIRT1), nuclear factor kappa B subunit p65 (NF-κB p65), fork-head box class O-3a (FOXO3a), androgen receptor (AR), and xanthine oxidase (XO) were analysed. ResultsMale NAFLD patients with hyperuricemia displayed more frequent and extensive liver injury than those in female patients. In male rats, hyperuricemia was associated with increased levels of insulin, alanine aminotransferase (ALT) and triglyceride (TG). At the molecular level, hyperuricemia was associated with decreased expression of SIRT1 and its phosphorylation, phosphorylation of FOXO3a, increased expression of AR and XO, and deacetylation of NF-κB P65. ConclusionsHyperuricemia is a compounding factor for NAFLD, particularly in males. The severer hepatic injury observed in male NAFLD patients may be attributed to the suppression of SIRT1 signalling induced by hyperuricemia.

Propolis relieves the cardiotoxicity of chlorpyrifos in diabetic rats via alleviations of paraoxonase-1 and xanthine oxidase genes expression

Pesticides cardiotoxicity in case of diabetic-induced cardiac complications is unidentified. The probable amelioration role of propolis is gauged against the cardiotoxic effects of chlorpyrifos in the diabetic rats through paraoxonase-1 (PON1) and xanthine oxidase (XO) genes dysregulation. Fifty-six male rats were distributed (n = 7) into eight groups. The first one saved as control whereas the 2nd, 3rd, and 4th were kept for propolis aqueous extract (100 mg/kg), diabetes (60 mg/kg streptozotocin) and chlorpyrifos (2.5 mg/kg), respectively. The 5th was diabetes/chlorpyrifos combination, while 6th, 7th, and 8th were intubated with propolis for four weeks after diabetic induction, chlorpyrifos intoxication, and their combination, respectively. The plasma glucose, lipid profiles, cardiac enzymes and interleukin-6 (IL-6) significantly elevated, while insulin decreased in the diabetic and combination groups. Although the cardiac acetylcholinesterase, total thiols, and PON1 significantly reduced after diabetic and/or chlorpyrifos gavage, the protein carbonyl, superoxide dismutase, catalase, and XO significantly elevated. The mRNA genes expression of PON1 and XO have also confirmed the enzymatic activities. Interestingly, propolis significantly restored the hyperglycemia, hypoinsulinemia, hyperlipidemia, IL-6 elevations, and antioxidant defense system disorder. These records revealed that the immunomodulatory, anti-diabetic and antioxidant tasks are fine pointers for the cardiovascular defender of propolis especially during diabetes and/or pesticides exposure.

503-P: Inhibition of Glucose Transporter 9 Increases Serum Uric Acid Level but Attenuates Renal Albumin Excretion in Streptozotocin-Induced Diabetic Rats: A Role of Hepatic Uric Acid Metabolism

Background: In previous studies, we confirmed that endogenous uric acid (UA) formation increases in the streptozotocin (STZ)-induced diabetic rats with renal injury. Yet changes of renal UA reabsorption and hepatic UA metabolism remain unclear in this model. Methods: STZ-induced diabetic rats and control rats were treated with benzbromarone (BZ), a glucose transporter 9 (GLUT9) inhibitor for 8 weeks. At baseline, 4 and 8 weeks after BZ treatment, blood samples were collected for fasting blood glucose (FBG), serum uric acid (SUA), serum creatinine (SCr), and blood urea nitrogen (BUN). Simultaneous urinary samples were tested and daily urinary amount of albumin (UAE), uric acid (UUA), creatinine (UCR), urea nitrogen (UUN) were calculated. Gene expressions of GLUT9, xanthine oxidase (XO), urate transporter 1 (URAT1) in the kidney and GLUT9, XO as well as uricase in the liver were detected by RT-PCR. Results: 1) Compared with normal rats, FBG, BUN, UUN, UAE and UUA were significantly increased, while SUA was significantly decreased in diabetic rats, while SCr and UCR levels were compared. Treatment with BZ did not change FBG in both rats. BZ significantly decreased SCr, BUN and UAE levels but increased SUA in diabetic rats. 2) In the kidney, expression of GLUT9 and XO was increased, while URAT1 was not altered in diabetic rats if compared with control rats. BZ treatment exerted no any effects on gene expression of GLUT9 and XO. 3) In the liver, gene expression of XO and uricase was compared between diabetic and normal rats, while GLUT9 was significantly upregulated in diabetic rats. BZ treatment remarkably inhibited GLUT9 expression but left XO and uricase unchanged in diabetic rats. Conclusions: 1) Inhibition of hepatic GLUT9 in STZ-induced diabetic rats increased SUA indicates that GLUT9 pathway for UA metabolism is critical in this model. 2) BZ treatment attenuates urinary albumin excretion in diabetes. Disclosure C. Chen: None. J. Ran: None. R. Zhang: None. G. Chen: None. P. Zhu: None. J. Qiu: None. R. Tan: None. Y. Liu: None.

Early Life Iron Excess Enhances Hippocampal Purine Catabolism Through Activation of Xanthine Oxidase in a Nursing Piglet Model (P11-072-19)

ObjectivesOur prior work demonstrated that dietary iron excess in early life results in iron overload in both liver and hippocampus in pre-weanling piglets. Herein, we aimed to identify metabolic processes altered by iron overload in liver and hippocampus. MethodsLiver and hippocampal tissues collected from 21-day old nursing piglets receiving high (HI; 50 mg iron/d · kg body weight), n = 5) or no oral iron supplementation (NI, n = 5) from birth to PD 21 were analyzed for non-targeted metabolomics, using gas chromatography mass spectrometry. Based on profiled changes in hippocampal metabolites, we further analyzed xanthine oxidase (XO), a rate limiting enzyme for purine degradation, for its mRNA, protein and enzyme activity by RT-qPCR, western blot, and ELISA. Results108 and 126 metabolites were identified in hippocampus and liver, respectively. In comparison with NI, HI altered abundance of 15 metabolites in hippocampus (P < 0.05, q < 0.2). Myo-inositol and N-acetylaspartic acid, two abundant metabolites in the CNS with broad implications in neuronal function and myelination, were decreased in response to hippocampal iron overload. Seven metabolites involved in purine and pyrimidine metabolism (e.g., hypoxanthine, xanthine and beta-alanine) in hippocampus were modulated in a coordinated pattern by HI, implicating a shift from purine salvage towards degradation, governed by XO. In support of these findings, up-regulation of XO mRNA expression (2.3-fold, P < 0.05) and activity (fold/stats?) was found in hippocampus but not in liver (P > 0.05). Despite overt iron loading, the hepatic metabolome remained stable (q > 0.2). ConclusionsOur findings suggest that iron overload increases hippocampal purine degradation via enhanced XO expression and activity, deleteriously altering tissue redox balance and ROS production. Purine salvage contributes to ATP production in the CNS, where a global shift from purine salvage to degradation due to HI may compromise energetics in the developing hippocampus. Funding SourcesUC Davis; NIFA.

Cholesterol crystals promote endothelial cell and monocyte interactions via H2O2-mediated PP2A inhibition, NFκB activation and ICAM1 and VCAM1 expression

In the present study, we show that cholesterol crystals induce NFκB activation, and ICAM1 and VCAM1 expression via xanthine oxidase-mediated H2O2 production and PP2A inhibition in influencing endothelial cell and monocyte interactions and all these adverse effects of cholesterol crystals could be attenuated by proresolving lipid mediator RvD1. In addition, feeding mice with cholesterol rich diet (CRD) increased xanthine oxidase expression, its activity and H2O2 production leading to PP2A inhibition, NFκB activation, and ICAM1 and VCAM1 expression and RvD1 attenuated all these effects of CRD substantially. Furthermore, peripheral blood mononuclear cells (PBMCs) from wild type mice when injected into mice that were fed with CRD or RvD1 + CRD showed increased leukocyte trafficking to arteries of CRD-fed mice as compared to RvD1 + CRD mice. These findings suggest that cholesterol crystals via promoting oxidant stress and inhibiting Ser/Thr phosphatases such as PP2A stimulate NFκB activation and ICAM1 and VCAM1 expression, and thereby enhance EC-monocyte interactions. In addition, proresolving lipid mediators such as RvD1 appear to exert their anti-inflammatory effects via countering the adverse effects of cholesterol crystals or CRD.

Cholesterol crystals increase vascular permeability by inactivating SHP2 and disrupting adherens junctions

To understand the adverse effects of cholesterol crystals on vascular homeostasis, we have studied their effects on endothelial barrier function. Cholesterol crystals increased endothelial barrier permeability in a dose and time‐dependent manner. In addition, cholesterol crystals induced tyrosine phosphorylation of VE‐cadherin and a‐catenin, disrupting endothelial AJ and its barrier function and these effects required xanthine oxidase‐mediated H2O2 production, SHP2 inactivation and Frk activation. Similarly, feeding C57BL/6 mice with cholesterol‐rich diet increased xanthine oxidase expression, H2O2 production, SHP2 inactivation and Frk activation leading to enhanced tyrosine phosphorylation of VE‐cadherin and a‐catenin, thereby disrupting endothelial AJ and increasing vascular permeability. Resolvin D1, a specialized pro‐resolving mediator, prevented all these adverse effects of cholesterol crystals and cholesterol‐rich diet in endothelial cells and mice, respectively. Based on these observations, it is likely that cholesterol crystals via disrupting AJ increase vascular permeability, a critical event of endothelial dysfunction and specialized pro‐resolving mediators such as Resolvin D1 exert protection against these effects.Support or Funding InformationHL074860 from NHLBI to GNR.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Monosodium Urate Contributes to Retinal Inflammation and Progression of Diabetic Retinopathy.

We have investigated the contributing role of monosodium urate (MSU) to the pathological processes associated with the induction of diabetic retinopathy (DR). In human postmortem retinas and vitreous from donors with DR, we have found a significant increase in MSU levels that correlated with the presence of inflammatory markers and enhanced expression of xanthine oxidase. The same elevation in MSU levels was also detected in serum and vitreous of streptozotocin-induced diabetic rats (STZ-rats) analyzed at 8 weeks of hyperglycemia. Furthermore, treatments of STZ-rats with the hypouricemic drugs allopurinol (50 mg/kg) and benzbromarone (10 mg/kg) given every other day resulted in a significant decrease of retinal and plasma levels of inflammatory cytokines and adhesion factors, a marked reduction of hyperglycemia-induced retinal leukostasis, and restoration of retinal blood-barrier function. These results were associated with effects of the hypouricemic drugs on downregulating diabetes-induced levels of oxidative stress markers as well as expression of components of the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome such as NLRP3, Toll-like receptor 4, and interleukin-1β. The outcomes of these studies support a contributing role of MSU in diabetes-induced retinal inflammation and suggest that asymptomatic hyperuricemia should be considered as a risk factor for DR induction and progression.

In vivo antioxidant activity of mackerel (Scomber japonicus) muscle protein hydrolysate.

Pacific chub mackerel (Scomber japonicus) is an important fish throughout the world, especially in East Asian countries, including Korea, China, and Japan. Protein hydrolysates from marine sources are commonly used as nutritional supplements, functional ingredients, and flavor enhancers in the food, beverage, and pharmaceutical industries. Antioxidants isolated from fish are relatively easy to prepare, are cost effective, and have no reported side effects. Hence, the present study aimed to investigate the in vivo antioxidant activities of mackerel muscle protein hydrolysate (MMPH) prepared using Protamex. The in vivo bioactivities of MMPH were investigated in alcoholic fatty liver mice (C57BL/6). Serum alanine aminotransferase and aspartate aminotransferase levels were comparable in test and control mice, whereas serum triglyceride and lipid peroxidation levels significantly (p < 0.05; p < 0.001) decreased after administration of MMPH (100–500 mg kg−1), especially at a concentration of 100 mg kg−1. A significant (p < 0.05) reduction in xanthine oxidase activity was observed in all groups treated with MMPH (100–500 mg kg−1), as compared with the control group. Significantly (p < 0.05) higher superoxide dismutase (SOD) activity/protein expression and regulated catalase (CAT) activity/protein expression levels were observed in groups administered MMPH (100–500 mg kg−1), especially at a concentration of 100 mg kg−1. These results show that the abundant amino acids of S. japonicus play an important role in the cytosol of the liver cells by directly participating in the expression of xanthine oxidase and the detoxifying SOD and CAT proteins, thereby enhancing antioxidant ability and ultimately, inhibiting lipid peroxidation. This study demonstrated that muscle protein hydrolysate from S. japonicus has strong antioxidant activities.

Lactobacillus brevis DM9218 ameliorates fructose-induced hyperuricemia through inosine degradation and manipulation of intestinal dysbiosis.

High fructose consumption exacerbates purine degradation and intestinal dysbiosis, which are closely related to the development of hyperuricemia. Probiotics are powerful weapons to combat metabolic disturbance and intestinal dysbiosis. Previously we isolated a Lactobacillus strain named DM9218 that could reduce the serum uric acid (UA) level by assimilating purine nucleosides. The present study aimed to evaluate the effects of DM9218 on high-fructose-induced hyperuricemia and to elucidate the underlying mechanisms. Mice were fed a normal diet, a high-fructose diet, or high-fructose diet with DM9218. Metabolic parameters, fructose- and UA-related metabolites, and fecal microbiota were investigated. Whole-genome sequencing of strain DM9218 was also conducted. In addition, an inosine hydrolase from DM9218 was heterologously expressed in Escherichia coli, and its inosine-degrading activity was detected. Our results indicated that DM9218 could decrease serum UA level and hepatic xanthine oxidase activity in fructose-fed mice. It could protect against high-fructose-induced liver damage and retard UA accumulation by degrading inosine. The modulation effect of DM9218 on high-fructose-induced intestinal dysbiosis resulted in enhancement of intestinal barrier function and reduction of liver lipopolysaccharide, which was closely correlated with the down-regulation of inflammatory cytokine-stimulated xanthine oxidase expression and activity. Lactobacillus brevis DM9218 is a probiotic strain with the potential to ameliorate fructose-induced hyperuricemia.

189 - Hepatic-specific ablation or whole-body inhibition of xanthine oxidase in mice corrects obesity-induced systemic hyperuricemia without improving metabolic abnormalities

Rationale: Systemic hyperuricemia (HyUA) in obesity/T2DM, facilitated by elevated xanthine oxidase (XO) activity, which is the sole source of UA in mammals, has been proposed to contribute to the pathogenesis of insulin resistance/dyslipidemia in obesity. However, this hypothesis has not been assessed directly. Objectives The effects of tissue-specific, genetic ablation of XO (a liver-specific knockout (LXO)) and whole-body pharmacologic inhibition of XO (febuxostat (FEBUX)) on obesity-induced insulin resistance/dyslipidemia were assessed. Findings Deletion of hepatic XO substantially lowered liver and plasma UA levels. When exposed to an obesogenic diet LXO and floxed (FLX, control) mice became equally obese. However, unlike obese floxed, liver and systemic HyUA in LXO mice was absent. Despite this, obese LXO mice became as insulin resistant and dyslipidemic as obese FLX mice. In obese C57BL/6J mice, FEBUX dramatically lowered plasma and tissue UA and XO activity compared to vehicle controls (CONT). However, obesity-associated insulin resistance/dyslipidemia were similar in FEBUX and CONT. Furthermore, neither pharmacologic inhibition nor hepatic ablation of XOR significantly altered indices of oxidant stress in the liver at 20 weeks of high-fat feeding compared with untreated controls. Conclusions These data demonstrate that liver XO expression is a critical determinant of blood UA homeostasis; that deletion of liver XO is sufficient to prevent the systemic HyUA of obesity, and that neither prevention nor correction of HyUA improve insulin resistance/dyslipidemia in obesity or diminish liver oxidant load. Thus, systemic HyUA, while clearly a biomarker of the metabolic abnormalities of obesity, does not appear to be a causative factor.

Xanthine Oxidase Inhibition by Febuxostat in Macrophages Suppresses Angiotensin II-Induced Aortic Fibrosis.

BACKGROUNDSeveral reports from basic researches and clinical studies have suggested that xanthine oxidase (XO) inhibitors have suppressive effects on cardiovascular diseases. However, the roles of a XO inhibitor, febuxostat (FEB), in the pathogenesis of vascular remodeling and hypertension independent of the serum uric acid level remain unclear.METHODSTo induce vascular remodeling in mice, angiotensin II (Ang II) was infused for 2 weeks with a subcutaneously implanted osmotic minipump. FEB was administered every day during Ang II infusion. Aortic fibrosis was assessed by elastica van Gieson staining. Mouse macrophage RAW264.7 cells (RAW) and mouse embryonic fibroblasts were used for in vitro studies.RESULTSFEB suppressed Ang II-induced blood pressure elevation and aortic fibrosis. Immunostaining showed that Ang II-induced macrophage infiltration in the aorta tended to be suppressed by FEB, and XO was mainly colocalized in macrophages, not in fibroblasts. Transforming growth factor-β1 (TGF-β1) mRNA expression was induced in the aorta in the Ang II alone group, but not in the Ang II + FEB group. Ang II induced α-smooth muscle actin-positive fibroblasts in the aortic wall, but FEB suppressed them. XO expression and activity were induced by Ang II stimulation alone but not by Ang II + FEB in RAW. FEB suppressed Ang II-induced TGF-β1 mRNA expression in RAW.CONCLUSIONSOur results suggested that FEB ameliorates Ang II-induced aortic fibrosis via suppressing macrophage-derived TGF-β1 expression.

BI1 alleviates cardiac microvascular ischemia-reperfusion injury via modifying mitochondrial fission and inhibiting XO/ROS/F-actin pathways.

Pathogenesis of cardiac microvascular ischemia-reperfusion (IR) injury is associated with excessive mitochondrial fission. However, the upstream mediator of mitochondrial fission remains obscure. Bax inhibitor 1 (BI1) is linked to multiple mitochondrial functions, and there have been no studies investigating the contribution of BI1 on mitochondrial fission in the setting of cardiac microvascular IR injury. This study was undertaken to establish the action of BI1 on the cardiac microvascular reperfusion injury and figure out whether BI1 sustained endothelial viability via inhibiting mitochondrial fission. Our observation indicated that BI1 was downregulated in reperfused hearts and overexpression of BI1 attenuated microvascular IR injury. Mechanistically, reperfusion injury elevated the levels of xanthine oxidase (XO), an effect that was followed by increasedreactive oxygen species (ROS) production. Subsequently, oxidative stress mediated F-actin depolymerization and the latter promoted mitochondrial fission. Aberrant fission caused mitochondrial dysfunction and ultimately activated mitochondrial apoptosis in cardiac microvascular endothelial cells. By comparison, BI1 overexpression repressed XO expression and thus neutralized ROS, interrupting F-actin-mediated mitochondrial fission. The inhibitory effect of BI1 on mitochondrial fission sustained endothelial viability, reversed endothelial barrier integrity, attenuated the microvascular inflammation response, and maintained microcirculation patency. Altogether, we conclude that BI1 is essential in maintaining mitochondrial homeostasis and alleviating cardiac microvascular IR injury. Deregulated BI1 via the XO/ROS/F-actin pathways plays a causative role in the development of cardiac microvascular reperfusion injury.

Konjac glucomannan improves hyperuricemia through regulating xanthine oxidase, adenosine deaminase and urate transporters in rats

To develop a more effective and safer treatment for Hyperuricemia (HUA), this research investigated the anti-hyperuricemic mechanism of KGM from the perspectives of uric acid (UA) production and excretion in rat model. After four-week experiment, KGM at 168 mg/kg did best in reducing serum UA level. The mechanism of KGM improving HUA was related to its inhibitory capacity to the activities and mRNA expression of xanthine oxidase (XOD) and adenosine deaminase (ADA) in liver. Meanwhile, KGM could also down-regulate the protein expression of uric acid transporters1 (URAT1) and up-regulate the mRNA and protein expression of urate transporter (UAT), organic anion transporter1 (OAT1) and organic anion transporter3 (OAT3) in kidney. Moreover, KGM could also alleviate the renal dysfunction caused by HUA by mitigating urate deposition, and reducing serum creatinine (Cr) and blood urea nitrogen (BUN) levels. KGM might complement existing therapies to improve HUA.