Xanthine Oxidase Activity Levels Research Articles

Beneficial Effects of Mild Hyperuricemia in Salt-Sensitive Hypertension

Hyperuricemia (HrU) or increased plasma uric acid (UA) is associated with worsening hypertension (HTN) and kidney damage. Paradoxically, UA is also known to be an endogenous antioxidant. Some studies suggest that only HrU with crystals, but not asymptomatic HrU promotes the progression of these diseases. We hypothesized that mild asymptomatic HrU is beneficial in controlling the progression of salt-sensitive (SS) HTN. Due to sex differences in urate handling and SS HTN, we used both male and female Dahl SS rats in this study. Radiotelemetry was used to measure blood pressure and various approaches, including RNA-Seq, were employed to assess kidney injury and identify potential molecular mechanisms. Mild HrU was induced using 2% oxonic acid in the diet, a uricase inhibitor that prevents the breakdown of UA further into more soluble allantoin. Groups: 1-2) male and female 4% NaCl high salt (HS) diet; 3-4) male and female HS + 2% oxonic acid (HS/oxo) diet. After 3 weeks, in response to oxonic acid supplementation, both sexes showed a significant increase of UA in plasma compared to their respective HS-only controls (Males: 0.63 ±0.07 vs. 2.17 ±0.34; Females 0.78 ±0.15 vs. 2.04 ±0.35 mg/dl, HS vs. HS/oxo). Interestingly, only male HS/oxo rats showed a significant increase in uricosuria (Males: 0.23 ±0.03 vs. 0.45 ±0.06; Femaels: 0.26 ±0.06 vs. 0.26 ±0.001 UA/Cre, HS vs. HS/oxo). Moreover, the mild HrU was associated with a significant attenuation of the progression and magnitude of the mean arterial pressure in male but not female rats (Males: 157 ±3 vs. 136 ±3; Females: 155 ±6 vs. 154 ±5 mmHg, HS vs. HS/oxo). Xanthine oxidase (XO) is one of the enzymes that produce UA, and its activity has been shown to affect HTN as well. Therefore, we examined the level of XO activity in the plasma after the treatment. While there was no difference in the activity based on the diet within each sex, females had significantly lower levels of XO activity compared to males in each of the diets. To further investigate the beneficial phenotype seen in male rats, we evaluate changes in the progression of renal pathology. The HS/oxo group compared to the HS group had a lower kidney weight/body weight ratio and lower protein cast accumulation, indicating lower kidney damage. RNA-Seq analysis showed that the attenuated HTN phenotype was associated with an increased expression in Mas1 (MAS receptor), Klk-1 (Kallikrein-1), and Pcsk6 (PCSK6 enzyme) which can all lead to the activation of different vasodilatory pathways. Our study showed that in male but not female Dahl SS rats, asymptomatic mild HrU accompanied by hyperuricosuria ameliorates the progression of SS HTN and protects kidneys from further damage. This work is supported by the American Society of Nephrology Ben J. Lipps Research Fellowship Program (Dimitrios G. Oreopoulos Research Fellowship Award to L.V.D.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

РАСПРЕДЕЛЕНИЕ ГЕНОТИПОВ ГЕНА SLC2A9, УРОВЕНЬ МОЧЕВОЙ КИСЛОТЫ И МЕТАБОЛИТЫ ПУРИНОВОГО ОБМЕНА У ПАЦИЕНТОВ С АРТЕРИАЛЬНОЙ ГИПЕРТЕНЗИЕЙ И ФИБРИЛЛЯЦИЕЙ ПРЕДСЕРДИЙ

The aim is to investigate the frequency of genotypes and alleles of the SLC2A9 gene rs734553 polymorphism, the level of serum uric acid (sUA) and metabolites of purine metabolism in patients with arterial hypertension (AH) and atrial fibrillation (AF), as well as in healthy individuals. Material and methods. The study included 154 patients: 50 were healthy individuals (group 0), of which 22 (44%) were men and 28 (56%) were women aged 50 [45;53] years and 104 were patients with AH and AF (main group), of which 94 (90.4%) were men and 10 (9.6%) were women aged 55 [45; 61] years. The main group was divided into subgroups: subgroup I – patients with AF without a history of AH and other rhythm disorders (n=13); subgroup II – patients with AH in combination with AF (n=68); subgroup III – patients with AH without a history of AF or other rhythm disturbances (n=23). Hyperuricemia was detected in 34 (22.1%) patients, normal uric acid levels were revealed in 120 (77.9%) patients. All patients were studied using clinical, laboratory, instrumental and molecular genetic research methods. The level of sUA was determined by the enzymatic colorimetric method. Serum xanthine oxidase was measured using a method based on a solid phase sandwich-type enzyme-linked immunosorbent assay. Metabolites of purine metabolism in blood plasma were measured using the method of high-performance liquid chromatography. The SLC2A9 gene rs734553 polymorphism was determined using the polymerase chain reaction with real-time detection of results. Results. The patients with AH and AF, as compared to healthy individuals, had more severe disturbances of purine metabolism, characterized by higher concentration of sUA (330 [283; 412] µmol/l and 197 [161; 229] µmol/l (p<0.001), respectively). Also, in contrast to the group of healthy individuals, the group of patients with AH and AF demonstrated an increase in the level of adenosine (p=0.001), and a decrease in the levels of hypoxanthine and xanthine (p<0.001). There were no statistically significant differences in xanthine oxidase activity level (p>0.05), however, in 54% of patients in the main group it was higher than normal values. The dominant allele A and the dominant genotype A/A of the SLC2A9 gene rs734553 polymorphism (75%, p=0.005; 64%, p=0.001, respectively) occurred significantly more often in healthy individuals, while the recessive allele C and the heterozygous genotype A/C were found significantly more often in the group of patients with AH and AF (41.3%, p=0.005; 48.1%, p=0.003, respectively). The C/C genotype (41.7%, p=0.001) was significantly more common in patients with AH in combination with AF and hyperuricemia, compared to patients with AH combined with AF without hyperuricemia as well as healthy individuals (6.8%; 14%, p=0.001, respectively). Patients with AH in combination with AF and the C/C genotype were characterized by a significantly higher level of sUA (p=0.003) compared to patients with the A/A genotype. Conclusions. A statistically significant predominance of the recessive allele C of the SLC2A9 gene rs734553 polymorphism was established in patients with AH and AF compared with healthy individuals (p=0.005). In patients with AH in combination with AF and hyperuricemia, the C/C genotype was significantly more common (41.7%, p=0.001). Patients with AH in combination with AF and the C/C genotype were characterized by a significantly higher level of sUA (p=0.003) compared to patients with the A/A genotype.

Purine metabolism state in patients with type 1 diabetes mellitus

The aim of the study. To carry out a comprehensive analysis of the purine metabolism (PM) state and assess its features in patients with type 1 diabetes mellitus (DM). Materials and methods. 181 patients with type 1 DM were examined (94 women and 87 men) aged 42.5 ± 12.1 years. Indicators of the carbohydrate metabolism state, creatinine (Cr) concentration by the method of Popper, purine bases (PBs) and the activity of xanthine oxidase (XO) by a photometric method, uric acid (UA) by a colorimetric method were determined in fasting venous blood. UA excretion was detected by the colorimetric method, Cr by an enzymatic method. Renal UA clearance (RCUA), fractional UA clearance (FCUA), total UA tubular reabsorption (TTRUA) and hypoxanthine-guanine-phosphoribosyltransferase (HGPRT) activity were calculated. The comparison group, representative in terms of age and sex, included 25 healthy volunteers. Results. PM changes in patients with type 1 DM were orientated towards an excessively increased catabolism and insufficient reutilization of PBs. The structure of the detected disorders was as follows: hyperuricemia (HU) (13.8 %), enhanced RCUA (42.8 %), increased XO activity (35.6 %) and inhibition of HGPRT activity (53.3 %). In about 56 % of the subjects, high concentrations of PBs were found, and HU was diagnosed only in every seventh subject. It was identified that PB concentrations were negatively correlated with the level of XO activity. RCUA and XO activity levels were revealed to be of the greatest informational value for assessing the PM state in patients with type 1 DM. RCUA was significantly associated with the level of UA excretion and HGPRT activity. Relationships of RCUA and FCUA with HbAc1 levels were established. The higher the level of HbAc1, the greater the clearance of RCUA was, especially FCUA, which led to a significant decrease in TTRUA. Conclusions. PM in type 1 DM is characterized by a high intensity, which is realized due to a decrease in anabolism, increased oxidation and suppression of PB reutilization. Uricemia inadequately reflects the level of UA production in patients with type 1 DM. The severity of PM disorders in type 1 DM patients is associated with the carbohydrate metabolism compensation state.

Antioxidation and Nrf2-mediated heme oxygenase-1 activation contribute to renal protective effects of hydralazine in diabetic nephropathy

Reactive oxygen species (ROS) and oxidative stress are associated with the progression of diabetic nephropathy (DN). Hydralazine is an antihypertensive agent and may act as a xanthine oxidase (XO) inhibitor to reduce uric acid levels in a mouse renal injury model. This study aimed to investigate the potential mechanisms of hydralazine in experimental DN. Streptozotocin-induced diabetic mice were fed a high-fat diet to generate DN. Human renal proximal tubular epithelial cells were used in vitro. Nitrendipine and allopurinol which can reduce blood pressure or XO activity levels, were used as two positive controls. Hydralazine downregulated NF-κB/p38 signaling pathways and reduced TNF-α/IL-6 expressions in high glucose-stimulated renal proximal tubular epithelial cells. Hydralazine reduced in vitro ROS production via XO inhibition and nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated heme oxygenase (HO)-1 activation. Furthermore, hydralazine reduced high glucose-induced apoptosis by downregulating PARP/caspase-3 signaling. Hydralazine and allopurinol but not nitrendipine reduced serum uric acid levels and systemic inflammation. Hydralazine and allopurinol treatment improved renal function with decreased urinary albumin-to-creatinine ratios, glomerular hypertrophy, glomerulosclerosis, and fibrosis in the kidney of DN mice. While both hydralazine and allopurinol downregulated XO and NADPH oxidase expression, only hydralazine upregulated Nrf2/HO-1 renal expression, suggesting the additional effects of hydralazine independent of XO/ NADPH oxidase inhibition. In conclusion, hydralazine protected renal proximal tubular epithelial cells against the insults of high glucose and prevented renal damage via XO/NADPH oxidase inhibition and Nrf-2/HO-1 activation, suggesting the comprehensive antioxidation and anti-inflammation mechanisms for the management of DN.

Integrative characterization of asymptomatic vs. symptomatic patients with moderate-severe primary mitral regurgitation

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by NHLBI and Specialized Centers of Clinically Oriented Research grant in cardiac dysfunction, by Department of Veteran Affairs for Merit Review and NIH Grant P01. Background Optimal timing for surgery in primary mitral regurgitation (PMR) is a subject of debate. Purpose Use a combination of imaging, circulating biomarkers and histology to define the transition from asymptomatic (asx) to symptomatic (sx) stage in moderate-severe PMR. Methods 57 controls, 82 sx and 47 asx patients with moderate to severe PMR underwent cardiac MR(CMR), plasma BNP, levels of xanthine oxidase (XO) activity, and circulating markers of collagen (Col) synthesis (propeptide of procollagen type I, PICP) and degradation (Col type I fibers, ICTP). Results A progressive worsening in the severity of adverse LV remodeling was noted based on CMR indices listed in Table 1. The 3D mid-wall LV endocardial curvature to wall thickness was lower in normal and similar in asx and sx patients.Plasma BNP was progressively higher in normal vs. asx vs sx (Figure 1A). The levels of XO activity were higher in sx vs. asx (Figure 1B,1C). Levels of PICP were similar among the three; levels of ICTP were significantly higher in the sx vs the asx (Figure 1D,1E). LV biopsies revealed large areas of patchy replacement fibrosis and areas devoid of interstitial Col (Figure 1F). From the subgroup of 56 patients who underwent CMR 6 months after surgery, 27% had LVEF < 50%. The preoperative LVEF, LVESV, LVESD and LA emptying fraction were predictors of postoperative drop in LVEF. Conclusion Increased COl breakdown coupled with markers of oxidative stress and CMR-based LV remodeling characterize the transition from asx to sx PMR. Longitudinal studies are needed to define cutoff"s for patient selection and optimal timing for MV surgery. CMR indices in normal, asx and sx PMR. Normal (57) Moderate/Severe MR Asymptomatic (56) Pre-Surgery MR Symptomatic (81) P-value Age 48 (34, 55) 54 (46, 62) * 57 (50, 67) * <0.0001 Female/Male 30(53%)/27(47%) 35(63%)/21(38%) 25(31%)/56(69%) LVEF (%) 64 (61, 67) 62 (59, 66) 63 (59, 67) 0.3482 LV EDV (mL/m2) 71 (61, 76) 89 (73, 103) * 100 (83, 123) *# <0.0001 LV ESV (mL/m2) 24 (21, 29) 32 (26, 38) * 36 (28, 47) * <0.0001 LVSV (mL/m2) 43 (37, 50) 54 (43, 66) * 60 (54, 77) *# <0.0001 LVED Mass/Volume 0.7 (0.6, 0.8) 0.6 (0.5, 0.7) * 0.6 (0.6, 0.7) * 0.0012 LVED Mass/Vol x SI 1.29 (1.05, 1.50) 0.97 (0.77, 1.15) * 0.94 (0.77, 1.14) * <0.0001 Regurgitant Volume (mL) ― 38 (26, 54) 57 (38, 83) # 0.001 Regurgitant Fraction (%) ― 39 (28, 50) 46 (36, 56) # 0.042 Table 1 shows the CMR indices of LV remodeling in normal, asymptomatic and symptomatic patients with moderate-severe PMR. p-values *vs. Normal; # vs. Asymptomatic. Kruskal-Wallis test or unpaired t-test Abstract Figure 1.

Xanthine oxidase enzyme activity in keratoconic corneal epithelium.

To assess the activity of xanthine oxidase (XO) enzyme in keratoconic corneal epithelium and to evaluate its relationship with the keratoconus (KC) severity. This prospective and randomized study included 66 eyes of 54 KC patients who received corneal collagen cross-linking treatment and 43 eyes of 32 patients who underwent photorefractive keratectomy due to their refractive error. During surgical procedures, the corneal epithelium was mechanically scraped and gathered to analyze the XO enzyme activity spectrophotometrically. The KC group was subdivided into three groups (stages 1, 2, and 3) according to the Amsler-Krumeich classification. The results were compared between the KC and the control group and in between KC subgroups. No significant differences in age and gender were found between the KC and control groups (p = 0.064 and p = 0.296, respectively). The mean XO activity levels of the KC and control groups were 173.57 ± 87.61 and 223.70 ± 99.52mIU/mg, respectively (p < 0.001). In KC group, 33 eyes were at stage 1, 19 were at stage 2, and 14 were at stage 3. No significant difference was observed between KC subgroups regarding XO activity levels (p = 0.681). In this study, our findings revealed that ultraviolet-related pro-oxidant XO enzyme may have a role in the etiopathogenesis of KC. Further studies are needed to support our result. When we started this study in 2018, we did not have a "Clinical Trials Registration." However, we have ethics committee approval (date: 21. 02. 2018/No: 22).

Uric acid increases IL-1β secretion and Caspase-1 activation in PBMCs of Behçet’s disease patients: The in vitro immunomodulatory effect of xanthine oxidase inhibitor Allopurinol

Behçet’s disease (BD) is a multisystem disease, which shares some features with other diseases belonging to the autoinflammatory disorders panel. Recent studies have postulated that IL-1β/Caspase-1 may play a cardinal role in autoinflammatory diseases. In this study, we aimed to (i) elucidate the mechanism underlying the involvement of xanthine oxidase (XO) and Uric Acid (UA) in BD (ii) study the direct effects of UA and XO inhibitor “Allopurinol” on nitric oxide (NO) and caspase-1-mediated IL-1β release in peripheral blood mononuclear cells (PBMCs) of BD patients. In this context, plasma of BD patients and healthy controls (HC) were used to measure XO activity, UA, advanced oxidized proteins products (AOPP) and NO levels. In Addition, PBMCs of BD patients and HC were treated or not with either UA or Allopurinol. Then we quantified NO and IL-1β levels, and Caspase-1 Activity in the supernatants and lysates of PBMCs, respectively. We showed that plasma levels of XO activity, UA, AOPP and NO are significantly increased in BD patients compared to those of HC. Interestingly, a significant positive correlation between XO and UA was observed in BD patients. Additionally, while UA has markedly increased NO, IL-1β, and Caspase-1 activity levels in PBMCs of BD patients, Allopurinol has exerted an immunomodulatory effect resulting in reduced NO, IL-1β and Caspase-1 levels in PBMCs of BD patients particularly during the active stages. Collectively, our results indicate a potential clinical use of XO as a tool for assessing BD activity, and suggest that the in-vitro immunomodulatory effect of Allopurinol may have a promising therapeutic value in BD management.

Xanthine Oxidase Activity in Patients with Sickle Cell Anaemia Presenting with Vaso-Occlusive Crises in University College Hospital, Ibadan

Recurrent bone pain or vaso-occlusive crisis (VOC) constitutes a major presentation in patients with sickle cell anaemia. This is partly attributable to vasospasm, oxidative stress and inflammation. Xanthine oxidase is released during VOC and it had been implicated in the pathogenesis of bone pain crisis in patients with sickle cell anaemia. This study was aimed at comparing the plasma levels of xanthine oxidase activity in adult patients with Sickle cell anaemia (SCA), during bone pain crisis (BPC) and steady state and correlating it with the severity of bone pain crisis. Thirty adult sickle cell anemia patients with BPC and 30 in steady state attending Haematology clinic at the University College Hospital, Ibadan, Nigeria and 30 normal haemoglobin A, age- and sex-matched controls were enrolled for this study. Severity of BPC was assessed with total summary pain score. Haematological parameters were determined by a 5-part autoanalyzer. Plasma xanthine oxidase activity was determined using enzyme linked immunosorbent assay (ELISA). Data obtained were analyzed using the Statistical Package for the Social Science (SPSS) version 20. Results were considered statistically significant if p<0.05. Biochemical parameters were correlated with the severity of bone pain crisis. Plasma xanthine oxidase activity was significantly elevated in the BPC group than in the steady state group (p=0.000) and HbA group (p=0.000). There steady state group plasma xanthine oxidase activity was also significantly higher than that of HbA group (p-0.032). Similarly, the plasma Plasma xanthine oxidase activity was significantly higher in all BPC severity group than steady state group with associated significantly low positive correlation of xanthine oxidase activity and bone pain severity. This study established that plasma xanthine oxidase activity was higher in patients with SCA presenting in bone pain crisis than steady state and HbA individual with associated positive correlation between plasma xanthine oxidase activity and bone pain severity.

Hydralazine improves ischemia-induced neovasculogenesis via xanthine-oxidase inhibition in chronic renal insufficiency

Oxidative stress is related to the progression of renal diseases and modulation of oxidative stress can lead to a reduction in vascular events in patients with chronic renal insufficiency (CRI). Indoxyl sulfate (IS) and xanthine oxidase (XO) are related to impaired neovasculogenesis in CRI. Hydralazine is suggested for blood pressure control in CRI. This study aimed to investigate whether hydralazine could improve ischemia-induced neovasculogenesis in CRI animals by reducing reactive oxygen species (ROS) levels. Mice underwent subtotal nephrectomy or sham surgery. Nitrendipine, probenecid, and allopurinol were used to reduce blood pressure, uric acid (UA), and XO activity levels, respectively, for comparison. Blood pressure, XO activity and UA levels that were increased after subtotal nephrectomy were reduced by hydralazine treatment. Allopurinol decreased blood XO activity and UA levels. Only hydralazine and allopurinol increased the number of circulating endothelial progenitor cells (EPCs) and improved neovasculogenesis in CRI mice. IS activated XO mRNA and ROS and inhibited the functions of EPCs and endothelial cells, which could be reversed by hydralazine. However, no additional beneficial effects were observed when XO was inhibited with both hydralazine and siRNA. In conclusion, hydralazine, as a potential XO inhibitor, not only reduced blood pressure and UA levels but also increased the number of circulating EPCs and improved neovasculogenesis in CRI animals. Hydralazine directly inhibited IS-induced ROS and XO activation in EPCs and endothelial cells, and restored their functions in vitro. Future studies should evaluate whether hydralazine could provide additional vascular protection in patients with CRI.

Oxidative stress in relation to adenosine deaminase, nitric oxide, nitric oxide synthase and xanthine oxidase in oral cavity cancer

Objective . Inflammation and oxidative stress are considered as the main pathways in oral cavity carcinoma . The aim of this study was to evaluate the activity levels of adenosine deaminase (ADA), nitric oxide (NO), nitric oxide synthase (NOS), and xanthine oxidase (XO) in oral cavity carcinoma, to determine their potential roles in carcinogenesis with relation to oxidative stress. Methods. Seventeen patients with oral cavity cancer underwent surgery as the primary therapy, were consisted in the study. Resected oral cavity carcinoma tissues were compared with the adjacent tumor-free control tissues of the same patients; ADA, NO, NOS, XO activity levels were evaluated in terms of difference. Results. There is a significant increase of ADA activity in squamous cell cancer tissues, which indicates a difference between the normal and tumor tissues at enzyme levels ( p <0.001). Conclusion. Elevated ADA activity might be an attempt to supress formation of the immunosupressed niche which promotes the onset of neoplasia and/or to inhibit tumor progression and metastasis.

0289 : Correlation of higher serum uric acid and severity of congestive heart failure in myocardial infarction: prospective study

Serum uric acid (SUA) reflects xanthine oxidase activity's level and oxidative stress’ production. Hyperuricemia has been identified as a marker of poor prognosis in patients with congestive heart failure (CHF) after acute myocardial infarction (AMI). To assess SUA levels determined on admission as a potential predictor of severity of the CHF in AMI patients. Data for this prospective observational study were collected from the ACS database register created on January 2015. We included consecutive patients with verified AMI admitted within 48 hours since the symptom onset during the period between January and November 2015. Clinical, biological and echocardiographic data were collected through direct contacts with patients during their hospitalization. The study was conducted on two groups: Fifty four patients (42.1%) with high level of SUA on admission were allocated to the group I and were compared to patients of group II (n=74, 57.9%) with normal SUA. Group I patients had less previous history of hypertension, dyslipidemia and smoking (37.8% vs 45.3%; 10.8% vs 17.6% and 51.3% vs 58.8% respectively) but more history of stroke 5.4% vs 1.96%. On admission, mean HR was higher in group 1 than in group 2 (83,73 +/– 17,19 vs 78,37+/–14,64 bpm). Mean SBP was lower in group 1 than in group 2. The mean LVEF was significantly lower in group 1 (40%+/–9,675 vs 45,67%+/–7,528 ; p= 0.03). This observational cohort identified a close relationship between SUA and Killip classification. Patients who developed short-term CHF had higher concentrations of SUA; the severity of the congestion was proportional to the value of SUA (Killip III-IV: 27.02% vs 7.8%; p =0.04). Our results suggest that hyperuricemia after myocardial infarction is associated with the severity of CHF. The serum level of uric acid is a suitable marker to predict adverse events related to myocardial infarction. The author hereby declares no conflict of interest

Possibility of Xanthine Oxidase and Malondialdehyde as a marker for Myocardial Infarction

Background: the serum markers of myocardial injury are used to help in establishing the diagnosis of myocardial infarction.Objective: to measure the levels of xanthine oxidase activity and malondialdehyde in myocardial infarction patients.Methods: 100 patients with myocardial infarction and 50 healthy persons were included in this study. Xanthine oxidase activity assayed according to the method described by bergmeyer, h.u. while malondialdehyde (MDA) estimation was carried by thiobarbituric acid (TBA) based colorimetric method.Results: significant increasing levels of xanthine oxidase activity and malondialdehyde were found in the blood of the patients with myocardial infarction when compared to healthy persons.Conclusions: we propose the measurement of the blood levels of xanthine oxidase as a marker of myocardial infarction.

Protective effects of allopurinol against acute liver damage and cirrhosis induced by carbon tetrachloride: Modulation of NF-κB, cytokine production and oxidative stress

Background The aim of this work was to evaluate the hepatoprotective ability of allopurinol to prevent the liver injury induced by carbon tetrachloride (CCl 4). Methods Acute liver damage was induced with CCl 4 (4 g/kg, by gavage); allopurinol (50 mg/kg, by gavage) was given 1 h before and 1 h after CCl 4 intoxication and two daily doses for the previous three days. Cirrhosis was established by CCl 4 administration (0.4 g/kg, i. p. three times a week, eight weeks); allopurinol was administered (100 mg/kg, by gavage, daily) during the long-term of CCl 4 treatment. Alanine aminotransferase (ALT), γ-glutamyl transpeptidase (γ-GTP), xanthine oxidase (XO), lipid peroxidation, reduced and oxidized glutathione (GSH, GSSG, respectively), hydroxyproline and histopathologycal analysis were performed. Nuclear factor-κB (NF-κB), pro-inflammatory and anti-inflammatory cytokines, transforming growth factor-β (TGF-β) and metalloproteinase-13 (MMP-13) were analyzed by Western blots. Results Acute injury increased ALT and γ-GTP activities, additionally enhanced NF-κB nuclear translocation and cytokines production such as tumor necrosis factor-α, interleukine-1β, and interleukine-6. Allopurinol partially prevented these effects, while increased interleukine-10. Acute and chronic CCl 4 treatments altered the levels of XO activity, lipid peroxidation, and GSH/GSSG ratio, while these remained within normal range with allopurinol administration. Necrosis, fibrosis and TGF-β production induced in chronic injury were partially prevented by allopurinol, interestingly, this drug induced MMP-13 activity. Conclusions Allopurinol possesses antioxidant, anti-inflammatory and antifibrotic properties, probably by its capacity to reduce NF-κB nuclear translocation and TGF-β expression, as well as to induce MMP-13. General significance Allopurinol might be effective treatment of liver diseases.

Immunobiochemical analysis of paraoxonase1 (anti‐oxidant), xanthine oxidase (oxidant) enzymes and lipid profile of cardiac disease patients in Lahore Metropolitan, Pakistan

Cardiac diseases are the major cause of death. Paraoxonase1 (PON1) is known as free radicals scavenger/anti-atherosclerosis, whereas xanthine oxidase (XO) is a free radicals generator. This study was undertaken to determine and compare the Paraoxonase and arylesterase activities of PON1 enzyme and activity of XO enzyme. The concentration of XO and PON1 enzymes along with lipid profile, lipid peroxides, and thiol level in plasma of cardiac patients (n=200) and healthy persons (n=200) of Lahore metropolitan, Pakistan was also determined. Anti-PON1 and anti-XO antibodies were developed, purified, and used to measure the concentration of PON1 and XO by competitive ELISA. It is observed that low paraoxonase (P=0.0073)/arylesterase activity (P=0.0038) of PON1 enzyme and its low concentration (P=0.0049) were observed in cardiac patients, whereas elevated level of XO activity (P=0.0129) and its concentration (P=0.0097) was observed in cardiac patients as compared with healthy persons. Low levels of HDL (P=0.0013), thiol (P=0.0014) and high level of cholesterol (P=0.0025), triglycerides (P=0.0018), LPO (P=0.0014), and LDL level (P=0.05) were observed in cardiac patients admitted in intensive care unit as compared with hypertensive patients and control subjects. It is concluded that overall low PON1 and high XO activities do cause imbalance of free radical system which ultimately leads to or enhance the cardiac pathological conditions.

Chronic xanthine oxidase inhibition following myocardial infarction in rabbits: Effects of early versus delayed treatment

Xanthine oxidase (XO) expression is increased in the failing heart, and animal studies in rodents and dogs showed that XO inhibition with allopurinol can improve left ventricular (LV) function and myocardial oxygen efficiency in the failing heart. The purpose of this study was to determine whether chronic XO inhibition by allopurinol or febuxostat, an investigational, potent non-purine, selective inhibitor of XO, could prevent or treat the progression of congestive heart failure (CHF) induced by coronary artery ligation in rabbits, a species that exhibits low intrinsic XO activity similar to humans. One day after coronary ligation, rabbits were assigned to one of four groups ( n = 7–8/group): control group (vehicle for 49 days), early treatment (prevention) group (febuxostat for 49 days), and two delayed-treatment groups (vehicle for 21 days followed by either febuxostat or allopurinol for 28 days). An echocardiogram of the LV was obtained on Days 0 (prior to surgery), 21, and 49. Control rabbits developed CHF by Day 21 (significant reduction in LV shortening fraction and ejection fraction, thinning of the LV posterior wall, and increases in LV internal dimensions and end-diastolic volume). Early preventive treatment with febuxostat significantly lessened the reduction of LV function when compared to vehicle on both Days 21 and 49. These cardiac functional improvements were accompanied by moderately less severe changes in LV dimensional parameters relative to vehicle controls. In contrast, when treatments with XO inhibitors were started after the establishment of CHF, no significant relative improvements in cardiac functional or dimensional parameters were observed. These results suggest that chronic preventive treatment with an XO inhibitor initiated shortly after myocardial infarction can delay or prevent the onset of CHF, and that XO inhibition initiated after establishment of the disease does not offer cardiac protection. In contrast to previous rodent studies which do suggest a cardiovascular (CV) benefit of delayed XO inhibition, the results of this rabbit study are in keeping with those of recently completed studies in severe CHF patients treated with oxypurinol, the active metabolite of allopurinol, in which no clinical benefit was observed. This may be due to the fact that rodents have relatively high levels of XO activity, while the levels in rabbits and humans are intrinsically low, suggesting that the rabbit may be the preferred model for investigating the role of XO in CV diseases.

Xanthine oxidase as a marker of myocardial infarction

In the present communication, we report remarkably elevated levels of xanthine oxidase activity in the blood of the patients with myocardial infarction when compared to age and sex matched healthy persons. Highly significant increase of malondialdehyde, serving as an index of lipid peroxidation and thus free radical mediated damage, has also been found in the patients. We propose the measurement of the blood levels of xanthine oxidase, a very simple, reliable and less time consuming method as an indicator of myocardial infarction.

Propofol attenuates reperfusion injury after testicular torsion and detorsion

Propofol, which is widely used as an intravenous anesthetic, has been shown to have an antioxidant activity on several tissues. This study was designed to investigate the prevention of reperfusion injury with propofol after testicular torsion. Five groups of rats (seven in each group) were used. Animals in the control group (group I) did not received any treatment, while animals in the sham group (group II) underwent scrotal incision and testicular fixation only. After 2 h of 720 degrees left testicular torsion in groups III, IV and V, subsequent detorsion was done for 2 h in groups IV and V. Propofol (50 mg/kg) was injected transperitoneally 30 min prior to detorsion in group V. Both testicles in all rats were retrieved and tissue malondialdeyhde (MDA) level, which is a measure of the amount of free oxygen radicals, and enzymatic activity of xanthine oxidase (XO), which converts hypoxanthine to xanthine and uric acid were studied. In addition, tissue catalase (CAT) and glutathione peroxidase (GSH-Px) activities, which are endogenous scavenger enzymes, protecting tissues against free radicals, were studied. Additionally, histological evaluations were performed after hematoxylin and eosin staining. Testicular MDA levels, and XO and CAT activities were higher in the torsion group compared to sham control group (P<0.05). Detorsion caused a further increase in MDA levels, contrasting with a decrease in the levels of XO activity, while CAT activity was not changed. Pretreatment with propofol prevented a further increase in MDA levels and significantly decreased CAT activity following detorsion. GSH-Px activities were not effected either by torsion/detorsion or propofol pretreatment. Histologically, torsion caused some separation between germinal cells in the seminiferous tubules, which became much more prominent in the detorsion group and attenuated with propofol pretreatment. There was no significant change in any of the above-mentioned enzymatic activities nor were there histopathological changes in the contralateral testicle in any groups. It is concluded that biochemically and histologically reperfusion injury occurs in the ipsilateral testis following detorsion up to 2 h. Preference of propofol for anaesthesia during the detorsion procedure may attenuate such reperfusion injury.

Xanthine oxidase activity in the dexamethasone-induced hypertensive rat

Hypertension may be associated with an increase in oxidative stress as a possible mechanism for the increased vascular tone and organ injury. Previously, we reported an increased production of reactive oxygen species and endothelial cell death in the microcirculation of hypertensive rats. We hypothesize that xanthine oxidase (XO) may be a potential source of oxidants induced by glucocorticoid-induced hypertension. Male Wistar rats were administered dexamethasone (0.5 mg/kg/day) for 5 days to induce hypertension. After general anesthesia, cremaster muscle was collected for analysis of XO and xanthine dehydrogenase (XDH) activities. The mean blood pressure and XO levels in cremaster muscle were significantly increased in the dexamethasone-treated rats compared with controls. There was a strong age-dependent rise in total XO + XDH activity in all groups. To inhibit XO, we administered allopurinol (ALLO, 0.4 mg/mL) in the drinking water to a subset of control and dexamethasone-treated rats during a 5-day treatment. The ALLO significantly reduced the mean arterial blood pressure in the dexamethasone-treated rats. Although in the cremaster muscle the total XO + XDH levels were not completely reduced with ALLO, the XO levels of the dexamethasone-treated + ALLO rats were reduced to levels of the control + ALLO group. These results suggest that dexamethasone induces an elevated level of XO activity in the cremaster muscle. The enhanced XO activity can be attenuated by chronic allopurinol treatment.

Accumulation of uric acid in plasma after repeated bouts of exercise in the horse

Plasma concentration of uric acid, total peroxyl radical-trapping antioxidative parameter (TRAP), blood lactate concentration and plasma activity of xanthine oxidase (XO) were measured in six Standardbreed trotters after six bouts of exercise with increasing intensity on two separate days three days apart. Blood samples were taken immediately, 5, 10, 15, 30 and 60 min after each heat and 2, 4, and 6 hr after the last heat. Exercise caused an increase in TRAP and in the concentrations of lactate and uric acid. Plasma uric acid concentration increased exponentially with respect to time after the last heat performed at maximal speed, indicating a rapid increase in the rate of purine degradation. Plasma XO activity increased during exercise, but the intensity of exercise had only a minor effect on the level of XO activity. In conclusion, these data suggest that a threshold for the plasma accumulation of uric acid in terms of the intensity of exercise may exist and that XO may play a role in the formation of uric acid in horse plasma. Intense exercise causes an increase in the plasma antioxidant capacity that in the horse is mainly caused by the increase in the plasma uric acid concentration.

The variation of superoxide dismutase (SOD) and xanthine oxidase (XO) activities in milk using an improved method to quantitate SOD activity

AbstractAn improved method for determination of superoxide dismutase (SOD) in milk has been developed. The interference of endogenously occurring xanthine oxidase (XO) has been subs'antially reduced by addition of an ultrafiltration step, which removed 61 ± 10 (mean ± SD) % of the XO activity. This method was used to determine the SOD activity in milk serum from 15 Swedish Red and White (SRW) cows and 18 Swedish Friesian (SF) cows at various stages of lactation. The XO activity in raw milk was also determined. The milk from these cows had a mean SOD activity of 0.83 ± 1.14 U ml−1 milk serum and a mean XO activity of 49 ± 22 mU ml−1 raw milk (n = 127). A difference between breeds could be noted in XO activity, ie milk from SF cows had significantly (P &lt; 0.05) higher mean XO levels compared with milk from SRW cows, 54 ± 23 mU ml−1 than 44 ± 21 mU ml−1. A significantly increased level of XO activity in milk from SRW cows during the lactation was found. No significant effect of breed or stage of lactation on SOD activity could be detected. Individual cows with high and low milk SOD levels during the entire lactation have been identified.