Xanthine Oxidase Enzyme Activity Research Articles

Xanthine Oxidase Inhibitory Activity, Chemical Composition, Antioxidant Properties and GC-MS Analysis of Keladi Candik (Alocasia longiloba Miq).

Alocasia longiloba, locally known as ‘Keladi Candik’, has been used traditionally to treat wounds, furuncle and joint inflammations. A. longiloba can be a new source of herbal medicine against hyperuricemia by inhibiting the activity of xanthine oxidase enzyme, the enzyme which is responsible for the development of hyperuricemia in human. Existing xanthine oxidase inhibitors (XOI drugs) show several side effects on gout patients. Therefore, an alternative herbal medicine from plants, with high therapeutic property and free of side effects, are greatly needed. This study was conducted to evaluate XO inhibitory activity, chemical composition, antioxidant activity and GC-MS profile of A. longiloba. Our results showed that ethanolic petiole extract exhibited the highest XO inhibitory activity (70.40 ± 0.05%) with IC50 value of 42.71 μg/mL, followed by ethanolic fruit extracts (61.44 ± 1.24%) with the IC50 value of 51.32 μg/mL. In a parallel study, the phytochemical analysis showed the presence of alkaloid, flavonoid, terpenoids, glycoside and saponin in petiole and fruit extracts, as well as higher total phenolic and flavonoid contents and strong scavenging activity on DPPH and ABTS antioxidant assay. The GC-MS analysis of fruit and petiole extracts revealed the presence of various compounds belonging to different chemical nature, among them are limonen-6-ol, α-DGlucopyranoside, paromomycin, aziridine, phenol, Heptatriacotanol, Phen-1,2,3-dimethyl and Betulin found in ethanolic fruit extract, and Phen-1,4-diol,2,3-dimethyl-, 1-Ethynyl-3,trans(1,1-dimethylethyl), Phenol,2,6-dimethoxy-4-(2-propenyl)- and 7-Methyl-Z-tetradecen-1-olacetate found in ethanolic petiole extract. Some compounds were documented as potent anti-inflammatory and arthritis related diseases by other researchers. In this study, the efficiency of solvents to extract bioactives was found to be ethanol > water, methanol > hexane > chloroform. Together, our results suggest the prospective utilization of fruit and petiole of A. longiloba to inhibit the activity of XO enzyme.

Antihyperurisemic Activity of Aqueous Celery Infusion by Xanthine Oxidase Enzyme Inhibition

Hyperuricemia is a metabolic disorder because of excessive uric acid production. The high prevalence of hyperuresemia in the world, especially in Indonesia makes the research of antihyperurisemia drugs very needed today. The purpose of this study was to determine the activity of water infusion extract from celery stems and leaves to inhibited xanthine oxidase enzyme. Xanthine oxidase enzyme plays a role in change of hypoxanthine to xanthine and then becomes uric acid. The activity of xanthine oxidase enzyme was determined by UV spectrophotometry method and using xanthine substrate. Absorption at 290 nm indicates the presence of a uric acid product from xanthine oxidation by the xanthine oxidase enzyme. Infused extract which has the smallest absorption at 290 nm showed a better inhibitory ability of the xanthine oxidase enzyme because the change of xanthine substrate to uric acid is inhibited. The result showed the celery stems water infusion extract had better inhibition activity than celery leaves water infusion extract. The best inhibition percentage of celery stems water infusion was 90,25%, while the celery leaves water infusion was 69.07% both of at 20% concentration. The type inhibition of celery stems water infusion extract to xanthine oxidase enzyme showed an uncompetitive inhibition type because showed change in Km and Vmax values. Km and Vmax values before the addition of water infusion of celery stems were 104.33 ppm and 3.83 U/mL respectively changed to 74.49 ppm and 2.69 U/mL after the addition of extract.

S-allyl cysteine as potent anti-gout drug: Insight into the xanthine oxidase inhibition and anti-inflammatory activity

S-allyl cysteine (SAC) is known for its various beneficial effects such as neuroprotection and immunomodulation. The beneficial effect of SAC against gout has not been explored. The present study aims to describe the two roles of SAC: (1) inhibitory effect against xanthine oxidase (XO) enzyme activity; and (2) anti-inflammatory property against MSU crystal-induced gouty inflammation in rat. The inhibitory effect of SAC against bovine XO enzyme activity was determined in vitro. In silico analysis was carried out to determine the intermolecular interaction between SAC and bovine XO. MSU crystal was injected in the right paw of the rat to induce gouty inflammation. SAC (40 mg/kg body weight) and colchicine (positive control; 1 mg/kg body weight) was given for 3 days. At the end of the treatment, the oxidative stress, antioxidant parameters and mitochondrial function were determined in the ankle joint tissue. The concentration of inflammatory cytokines such as TNF-α and IL-1β was measured in the serum using ELISA. SAC inhibited (IC50 value, 33 μg/ml) XO enzyme activity in a competitive mode with corresponding Ki value of 4 μg/ml. In silico analysis predicted the interaction of SAC with the amino acids such as Arg880, Phe798, Phe914 and Phe1009 of XO enzyme. The root mean square deviation, root mean square fluctuation and free energy calculation values confirmed the stable SAC-XO interaction. The inhibition of SAC on XO enzyme activity in in vivo was further confirmed by silkworm model. SAC through reducing oxidative stress, enhancing antioxidants, protecting mitochondrial function has shown anti-inflammatory effect against MSU crystal-induced gout which was observed as reduced level of inflammatory markers in the serum. The medicinal potential of SAC as a preventive agent through its XO inhibitory property as well as curative agent through its anti-inflammatory property against gout has been understood from the present study.

Atrial Infarction-Induced Spontaneous Focal Discharges and Atrial Fibrillation in Sheep: Role of Dantrolene-Sensitive Aberrant Ryanodine Receptor Calcium Release.

The mechanisms underlying spontaneous atrial fibrillation (AF) associated with atrial ischemia/infarction are incompletely elucidated. Here, we investigate the mechanisms underlying spontaneous AF in an ovine model of left atrial myocardial infarction (LAMI). LAMI was created by ligating the atrial branch of the left anterior descending coronary artery. ECG loop recorders were implanted to monitor AF episodes. In 7 sheep, dantrolene-a ryanodine receptor blocker-was administered in vivo during the 8-day observation period (LAMI-D, 2.5 mg/kg, IV, BID). LAMI animals experienced numerous spontaneous AF episodes during the 8-day monitoring period that were suppressed by dantrolene (LAMI, 26.1±5.1; sham, 4.3±1.1; LAMI-D, 2.8±0.8; mean±SEM episodes per sheep, P<0.01). Optical mapping showed spontaneous focal discharges (SFDs) originating from the ischemic/normal-zone border. SFDs were calcium driven, rate dependent, and enhanced by isoproterenol (0.03 µmol/L, from 210±87 to 3816±1450, SFDs per sheep) but suppressed by dantrolene (to 55.8±32.8, SFDs per sheep, mean±SEM). SFDs initiated AF-maintaining reentrant rotors anchored by marked conduction delays at the ischemic/normal-zone border. NOS1 (NO synthase-1) protein expression decreased in ischemic zone myocytes, whereas NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) oxidase and xanthine oxidase enzyme activities and reactive oxygen species (DCF [6-carboxy-2',7'-dichlorodihydrofluorescein diacetate]-fluorescence) increased. CaM (calmodulin) aberrantly increased [3H]ryanodine binding to cardiac RyR2 (ryanodine receptors) in the ischemic zone. Dantrolene restored the physiological binding of CaM to RyR2. Atrial ischemia causes spontaneous AF episodes in sheep, caused by SFDs that initiate reentry. Nitroso-redox imbalance in the ischemic zone is associated with intense reactive oxygen species production and altered RyR2 responses to CaM. Dantrolene administration normalizes the CaM response, prevents LAMI-related SFDs, and AF initiation. These findings provide novel insights into the mechanisms underlying ischemia-related atrial arrhythmias.

Salvia plebeia Extract Inhibits Xanthine Oxidase Activity In Vitro and Reduces Serum Uric Acid in an Animal Model of Hyperuricemia.

Hyperuricemia is a clinical condition characterized by an elevated level of serum uric acid and is a key risk factor for the development of gout and metabolic disorders. The existing urate-lowering therapies are often impractical for certain patient populations, providing a rationale to explore new agents with improved safety and efficacy. Here, we discovered that Salvia plebeia extract inhibited the enzyme activity of xanthine oxidase, which is a key enzyme generating uric acid in the liver. In an animal model of hyperuricemia, S. plebeia extract reduced serum urate to the levels observed in control animals. The urate-lowering effect of S. plebeia extract in vivo was supported by the identification of compounds that inhibit xanthine oxidase enzyme activity in vitro. Nepetin, scutellarein, and luteolin contributed significantly to S. plebeia bioactivity in vitro. These compounds showed the highest potency against xanthine oxidase with IC50 values of 2.35, 1.74, and 1.90 µM, respectively, and were present at moderate quantities. These observations serve as a basis for further elaboration of the S. plebeia extracts for the development of new therapeutics for hyperuricemia and related diseases.

IN VITRO AND IN SILICO EVALUATION OF XANTHINE OXIDASE INHIBITORY ACTIVITY OF QUERCETIN CONTAINED IN SONCHUS ARVENSIS LEAF EXTRACT

Objective: The aim of the present study was to examine the inhibiting effects of quercetin contained in Sonchusarvensis leaf extract on the activity of xanthine oxidase, an essential enzyme for uric acid synthesis.Methods: Activity test was conducted in vitro by measuring the activity of xanthine oxidase using UV spectrophotometry and in silico by determining the interaction of quercetin and allopurinol (as comparation drug) with xanthine oxidase enzyme in terms of hydrogen bonds and binding free energy. Docking simulations were performed by Autodock4.2 package.Results: The active fraction, using the solvent n-hexane, ethyl acetate and water, tested the inhibitory activity of the xanthine oxidase enzyme in vitro obtained respectively IC50 of 263.19, 16.20 and 141.80 μg/ml. Isolates with highest activity identified as quercetin. The xanthine oxidase enzyme inhibitory activity insilico by molecular docking showed quercetin has free energy binding ˗7.71 kcal/mol, more negative than that of allopurinol ˗5.63 kcal/mol.Conclusion: This shows the affinity of quercetin stronger than that of allopurinol; so that it can be predicted that quercetin was more potential to inhibit xanthine oxidase enzyme activity. Thus the extract of the S. arvensis leaves containing the active compound quercetin was a potential use as antihyperuricemia.

Exercise Training Prevents Diaphragm Contractile Dysfunction in Heart Failure.

Patient studies have demonstrated the efficacy of exercise training in attenuating respiratory muscle weakness in chronic heart failure (HF), yet direct assessment of muscle fiber contractile function together with data on the underlying intracellular mechanisms remains elusive. The present study, therefore, used a mouse model of HF to assess whether exercise training could prevent diaphragm contractile fiber dysfunction by potentially mediating the complex interplay between intracellular oxidative stress and proteolysis. Mice underwent sham operation (n = 10) or a ligation of the left coronary artery and were randomized to sedentary HF (n = 10) or HF with aerobic exercise training (HF + AET; n = 10). Ten weeks later, echocardiography and histological analyses confirmed HF. In vitro diaphragm fiber bundles demonstrated contractile dysfunction in sedentary HF compared with sham mice that was prevented by AET, with maximal force 21.0 ± 0.7 versus 26.7 ± 1.4 and 25.4 ± 1.4 N·cm, respectively (P < 0.05). Xanthine oxidase enzyme activity and MuRF1 protein expression, markers of oxidative stress and protein degradation, were ~20% and ~70% higher in sedentary HF compared with sham mice (P < 0.05) but were not different when compared with the HF + AET group. Oxidative modifications to numerous contractile proteins (i.e., actin and creatine kinase) and markers of proteolysis (i.e., proteasome and calpain activity) were elevated in sedentary HF compared with HF + AET mice (P < 0.05); however, these indices were not significantly different between sedentary HF and sham mice. Antioxidative enzyme activities were also not different between groups. Our findings demonstrate that AET can protect against diaphragm contractile fiber dysfunction induced by HF, but it remains unclear whether alterations in oxidative stress and/or protein degradation are primarily responsible.

High cholesterol diet leads to oxidant load and peroxidation in the rabbit kidney tissue.

The aim of this study was to investigate possible effects of high cholesterol diet on oxidant/antioxidant status in rabbit kidney tissues. Although a number of experimental animal models have suggested that hyperlipidemia is associated with progressive kidney failure data remain sparse on the role of dietary cholesterol intake on kidney disease. Twelve male New Zealand albino rabbits were randomly divided into two groups (control and cholesterol). Both groups were fed on a standard laboratory diet. Animals in the cholesterol group additionally received cholesterol (1 g/kg/day), orally. The study period was 12 weeks. Activities of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), nitric oxide synthase (NOS), xanthine oxidase (XO), paraoxonase (PON), adenosine deaminase (ADA) enzymes and levels of malondialdehyde (MDA) and nitric oxide (NO) were measured in kidney tissue samples. Histological examination of the kidney tissue samples was also done. SOD, GSH-Px and XO enzyme activities were found to be decreased and NOS and PON activities increased significantly in cholesterol group compared to controls. As an indication of oxidation, MDA levels were found to be increased in cholesterol group. Histological examination revealed some derangements in the kidney tissue. High cholesterol diet creates oxidant load and causes peroxidation, which in turn, leads derangements in the rabbit kidney tissue (Tab. 2, Fig. 2, Ref. 69).

Isolation of a bioactive flavonoid from Spilanthes calva D.C. in vitro xanthine oxidase assay and in silico study

An isoprenylated flavonoid was isolated from the aerial parts of the Spilanthes calva D.C. The structure of the isolated compound was ascertained by UV, IR, 1H NMR, 13C NMR and mass analyses. The structure was elucidated as 6-(3-methylbut-1-enyl)-5,7-dimethoxy-4′-hydroxy flavone. The isolated compound was further evaluated by in vitro xanthine oxidase enzyme activity. Molecular docking study was carried out to establish the binding mode of isolated compound in the inhibitor-binding cavity of enzyme. The isoprenylated flavonoid was found to be possess potent xanthine oxidase inhibition activity with an IC50 of 16.56μM. Molecular docking study revealed that the potent action of the compound was due to the hydrogen bonding to ALA 1079 and π–π stacking interaction with PHE 914 in the inhibitor-binding cavity of xanthine oxidase.

Oxidation of aldehydes by xanthine oxidase located on the surface of emulsions and washed milk fat globules

The enzymatic activity of xanthine oxidase (XO) located within the native and recombined milk fat globule membrane (MFGM) on emulsion surfaces was investigated after successive washing with deionised water (DW) or simulated milk ultrafiltrate (SMUF). DW was more effective than SMUF at removing non-MFMG proteins from the globule surface. Surface XO activity on a protein basis increased after three washes due to loss of MFGM proteins to the serum phase. Recombined emulsions had higher surface enzymatic activity than washed native fat globule samples. The oxidation of acetaldehyde, 3-methylbutanal, 2-methylpropanol and 2-methylbutanal to the corresponding acids by XO on the globule surface was analysed. A higher proportion of aldehydes were depleted at higher XO activity when the initial aldehyde concentration was constant, and for higher initial concentrations of aldehydes. The recovery of aldehydes and acids was above 79%, indicating that the depleted aldehydes were mostly converted to the corresponding acids.

Synthesis of Thiosemicarbazones as Substrates for Xanthine Oxidase Enzyme Activity

Synthesis of Thiosemicarbazones as Substrates for Xanthine Oxidase Enzyme Activity

In vitroeffect of novel β-lactam compounds on xanthine oxidase enzyme activity

Carbazole substituted imines (2a-l) were prepared from N-methyl-3-amino carbazole with different aldehydes. The imines compounds undergo (2+2) cycloaddition reactions with in situ ketenes to produce β-lactam compounds (3a-l). The β-lactam compounds were tested as inhibitors of the xanthine oxidase (XO) purified from bovine milk. The results show that these compounds exhibit inhibitory effects on XO at low concentrations with IC(50) values ranging from 21.65 to 58.04 µM. The most effective compound for XO was 4-(4-chlorophenyl)-1-(9-ethyl-9H-carbazol-3-yl)-3-phenylazetidin-2-one with IC(50) of 21.65 μM. The lactams investigated here showed effective XO inhibitory effects, in the same range as the clinically used allopurinol.

The effects of stobadine on purine metabolism in rats treated with carbon tetrachloride

The aim of the present study was to investigate the relationship between liver damage induced by carbon tetrachloride (CCl_4) and adenosine deaminase (ADA), 5'-nucleotidase (5'NT), xanthine oxidase (XO) enzyme activities, and malondialdehyde (MDA) levels. The effect of stobadine on purine metabolism was also evaluated. Materials and methods: This study measured the effect of CCl_4 on ADA, 5'NT, XO enzyme activities, and MDA levels, and measured the histopathologic changes in liver cells. Results: Our research found that ADA, XO activities, and MDA levels increased in the CCl_4 group when compared with the control group. This was also supported by the histopathological changes in the CCl_4 and CCl_4+stobadine group found when compared with the control group. Stobadine could not protect cells against CCl_4 damage. Conclusion: The present study helps explain the biochemical mechanisms of liver injury formed by CCl_4 and shows the relationship between the purine degradation pathway and CCl_4induced cellular toxic effect. Cellular damage is dependent upon the biochemical response to increased purine degradation pathway enzyme activities, which also may be responsible for decreasing liver cellular adenosine levels and S-adenosyl-methionine and increasing superoxide anion and hydrogen peroxide levels. It is suggested that the inhibition of key enzymes of the purine degradation pathway (particularly ADA and XO) may prevent liver damage.

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.

Uric Acid, Heart Failure Survival, and the Impact of Xanthine Oxidase Inhibition

Increasing evidence suggests that serum uric acid (UA), a product of xanthine oxidase (XO), may be a useful marker for metabolic, hemodynamic, and functional staging in heart failure (HF) and a valid predictor of survival in HF patients. Recent data support an expanded role for UA and the XO pathway in the pathogenesis of HF, as studies have shown that an elevation in the enzymatic activity of XO can lead to increases in oxidative stress, endothelial dysfunction, and reduced myocardial function. Numerous population studies have previously reported that elevated UA levels are an independent predictor of cardiovascular mortality, and recent evidence suggests that lowering serum levels of UA may lead to improved outcomes in HF patients. The question of whether UA is only a marker rather than a causal factor in the pathogenesis of HF remains. Regardless of whether UA levels are ready for routine clinical use, either as a prognostic factor or novel therapeutic target, further prospective studies are necessary to demonstrate that routine measurement or reduction of UA levels improves outcomes in HF patients.

In Vitro Anti-inflammatory and Xanthine Oxidase Inhibitory Activity of Tephrosia purpurea Shoot Extract

The methanolic extract of Tephrosia purpurea (Leguminosae) shoots was evaluated in-vitro for its anti-inflammatory and xanthine oxidase inhibitory activity. Anti-inflammatory activity was measured by the Diene-conjugate, HET-CAM and beta-glucuronidase methods. The enzyme inhibitory activity was tested against isolated cow milk xanthine oxidase. The average anti-inflammatory activity of T. purpurea shoot extract in the concentration range of 1-2 microg/mL in the reacting system revealed significant anti-inflammatory activities, which, as recorded by the Diene-conjugate, HET-CAM and beta-glucuronidase assay methods, were 45.4, 10.5, and 70.5%, respectively. Screening of the xanthine oxidase inhibitory activity of the extract in terms of kinetic parameters revealed a mixed type of inhibition, wherein the Km and Vmax values in the presence of 25 to 100 microg/mL shoot extract was 0.20 mM/mL and 0.035, 0.026, 0.023 and 0.020 microg/min, while, for the positive control, the Km and Vmax values were 0.21 mM/mL and 0.043 microg/min, respectively. These findings suggest that T. purpurea shoot extract may possess constituents with good medicinal properties that could be exploited to treat the diseases associated with oxidative stress, xanthine oxidase enzyme activity and inflammation.

Distinct mechanisms for rasburicase induced hemolytic anemia and methemoglobinemia in tumor lysis syndrome

To the Editor: I read with great interest the paper by Bauters et al. [1] titled ‘‘Methemoglobinemia and hemolytic anemia after rasburicase administration in a child with leukemia.’’ in which the authors describe the third case in the literature of simultaneous occurrence of these two entities after the use of recombinant form of urate oxidase and also manifestations of acute pancreatitis. It is well recognized that production of hydrogen peroxide as a byproduct of the enzymatic oxidation of uric acid into the more water-soluble allantoin by rasburicase may trigger hemolytic anemia and methemoglobinemia in a genetically susceptible host with glucose-6-phosphate dehydrogenase enzyme deficiency and therefore this drug is contraindicated in this type of situation [2]. However there are several points that should be highlighted in relation to the pathogenesis of these two entities that are not explainable simply because of rasburicase induced hydrogen peroxide production. First of all, tumor lysis syndrome may itself elicit a systemic inflammatory response that leads to activation of endothelial cells and neutrophils which in turn release free radicals and reactive oxygen species (ROS). Besides, pro-inflammatory cytokines released by cell lysis induces nitric oxide production (which is one of the substances that can cause methemoglobinemia) and may combine synergistically with hydrogen peroxide to promote acute hemolysis too [3]. Secondly, serum uric acid plays an important role in protection from oxidative damage since it is a potent free-radical scavenger and increases in response to oxidative stress. So, rapid reduction in uric acid levels by rasburicase can compromise an important anti-oxidant mechanism and facilitates the emergence of acute hemolysis and methemoglobinemia [4]. Thirdly, under normal circumstances, cells are able to defend themselves against ROS damage with enzymes such as superoxide dismutases, catalases, lactoperoxidases, glutathione peroxidases and peroxiredoxins. Small molecules such as ascorbic acid, alpha-tocopherol, beta-carotene, methionine and glutathione also play important roles as cellular antioxidants. Decreased enzymatic activity and low antioxidant levels lead to an increased concentration of ROS which may facilitate rasburicase induced hemolysis and formation of methemoglobin [5]. Fourthly, urate oxidase is an endogenous enzyme found in most mammals but not in humans. Since humans do not express urate oxidase, rasburicase potentially can instigate an immune response that can include anaphylaxis or drug-mediated immune hemolytic anemia [6]. And last but not least, the symptoms of pancreatitis presented by the patient probably should be related to increased oxidative stress. It is known that pancreatic cells are highly susceptible to the effects of ROS. The use of rasburicase leads to a rapid reduction in uric acid and consequently there is an increase of enzymatic activity of xanthine oxidase to convert xanthine into uric acid. It is known that xanthine oxidase generates ROS and this coupled to the production of hydrogen peroxide by rasburicase may potentiate pancreatic inflammation [7, 8]. In summary, various host factors (impaired antioxidative mechanisms), disease characteristics (tumoral burden, cytokine release and ROS generation) and drug-related hydrogen peroxide production combined together create an environment of oxidative stress that ultimately triggers methemoglobinemia, hemolytic anemia and even pancreatic injury. R. Lopes da Silva (&) Hospital Santo Antonio dos Capuchos—CHLC, Alameda Santo Antonio dos Capuchos, 1169-050 Lisbon, Portugal e-mail: ronolosi@gmail.com

Effect of Taurine on Liver Xanthine Oxidase Activity and 3-Nitrotyrosine Level in Endotoxemia

Objective: Taurine, a semi-essential and sulphur-containing β-amino acid, is not incorporated into proteins. It has been shown in many in vitro and in vivo studies to have cytoprotective effects, and these actions are often attributed to an antioxidant mechanism. The purpose of this study was to investigate the effect of taurine on 3-nitrotyrosine production and xanthine oxidase activity in hepatocytes during endotoxemia. Methods: In this study, 40 adult male Dunkin Hartley guinea pig were randomly divided into four groups: control, taurine, endotoxemia and taurine plus endotoxemia (n=10). Animals were administered taurine (300 mg/kg, a single dose), lipopolysaccharide (4 mg/kg), or taurine plus lipopolysaccharide intraperitoneally. After six hours of incubation, when the highest blood levels of taurine and endotoxin were attained, the animals were sacrificed and liver samples were collected. The amount of 3-nitrotyrosine was measured by HPLC and xanthine oxidase enzyme activity was measured spectrophotometrically. Results: Lipopolysaccharide administration significantly increased protein 3-nitrotyrosine levels and xanthine oxidase activity in hepatic tissue compared with the control group (p<0.05). In the taurine plus endotoxemia group, taurine and lipopolysaccharide administration significantly reduced protein 3-nitrotyrosine levels and xanthine oxidase activity compared with the endotoxemia group (p<0.05). Conclusion: It has been concluded that taurine prevented the formation of protein nitration in hepatocytes. Taurine may act as a biological antioxidant not only by decreasing xanthine oxidase activity but also by scavenging peroxynitrite. (Gazi Med J 2011; 22: 14-7)

MarR homologs with urate‐binding signature

Bacteria that associate with living hosts require intricate mechanisms to detect and respond to host defenses. Part of the early host defense against invading bacteria is the production of reactive oxygen species, and xanthine oxidase is one of the main producers of such agents. The end-product of the enzymatic activity of xanthine oxidase, urate, was previously shown to be the natural ligand for Deinococcus radiodurans-encoded HucR and it was shown to attenuate DNA binding by Agrobacterium tumefaciens-encoded PecS and Burkholderia thailandensis-encoded MftR, all members of the multiple antibiotic resistance regulator (MarR) family. We here show that residues involved in binding urate and eliciting the DNA binding antagonism are conserved in a specific subset of MarR homologs. Although HucR controls endogenous urate levels by regulating a uricase gene, almost all other homologs are predicted to respond to exogenous urate levels and to regulate a transmembrane transport protein belonging to either the drug metabolite transporter (DMT) or the major facilitator superfamily (MFS), as further evidenced by the presence of conserved binding sites for the cognate transcription factor within the respective promoter regions. These data suggest the use of orthologous genes for different regulatory purposes. We propose the designation UrtR (urate responsive transcriptional regulator) for this distinct subfamily of MarR homologs based on their common mechanism of urate-mediated attenuation of DNA binding.

Anti-oxidative effects of the biennial flower of Panax notoginseng against H2O2-induced cytotoxicity in cultured PC12 cells

BackgroundRadix notoginseng is used in Chinese medicine to improve blood circulation and clotting; however, the pharmacological activities of other parts of Panax notoginseng have yet to be explored. The present study reports the anti-oxidative effects of various parts of Panax notoginseng.MethodsVarious parts of Panax notoginseng, including the biennial flower, stem-leaf, root-rhizome, fiber root and sideslip, were used to prepare extracts and analyzed for their anti-oxidation effects, namely suppressing xanthine oxidase activity, H2O2-induced cytotoxicity and H2O2-induced ROS formation.ResultsAmong various parts of the herb (biennial flower, stem-leaf, root-rhizome, fiber root and sideslip), the water extract of the biennial flower showed the strongest effects in (i) inhibiting the enzymatic activity of xanthine oxidase and (ii) protecting neuronal PC12 cells against H2O2-induced cytotoxicity. Only the water extracts demonstrated such anti-oxidative effects while the ethanol extracts did not exert significant effects in suppressing xanthine oxidase and H2O2-induced neuronal cytotoxicity.ConclusionsThe present study demonstrates the biennial flower of Panax notoginseng to have neuroprotection effect on cultured neurons and the underlying protection mechanism may involve anti-oxidation.