Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.6.1.2 (alanine aminotransferase)
26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxidant stress plays a major role in the pathophysiologic processes associated with ischemia-reperfusion injury. Xanthine oxidase (XO) is often implicated as a significant source of oxidants and increases in the circulation after hepatoenteric ischemia-reperfusion. We hypothesized that pulmonary injury is associated with hepatic ischemia-reperfusion resulting from descending thoracic aorta occlusion-reperfusion (AoOR). We also proposed that this remote pulmonary injury is attenuated through inactivation of circulating and tissue XO by tungstate, implicating an XO-dependent mechanism. Aortic occlusion was established in rabbits (standard or tungstate diet) for 40 min by 2 h reperfusion. Sham operated rabbits (standard or tungstate diet) served as controls. Hepatic reperfusion injury, as manifested by release of the hepatocellular enzyme alanine aminotransferase (ALT), was markedly increased after AoOR. Suprarenal-infrahepatic occlusion failed to increase ALT release. Tungstate pretreatment significantly (p < 0.05) reduced XO activity and ameliorated liver and intestinal injury (p < 0.05). Lung injury, manifested by increased bronchoalveolar lavage (BAL) protein concentration, BAL lactate dehydrogenase (LDH) activity and increased lung edema was significantly associated with liver injury (p < 0.05) and circulating XO activity (p < 0.001). XO inactivation significantly decreased BAL protein concentration, BAL LDH activity, and lung edema (p < 0.05). We conclude that remote pulmonary injury is significantly influenced by the extent of liver injury and circulating XO activity.
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PMID:Lung injury after hepatoenteric ischemia-reperfusion: role of xanthine oxidase. 891 49

The modulating effects of nitric oxide (NO) and reactive oxygen species on cocaine-induced hepatotoxicity were examined by measuring plasma alanine aminotransferase activity and by carrying out histological studies. Liver injury was induced by a single injection of cocaine in adult male ICR mice. Pretreatment with aminoguanidine (an inhibitor of NO synthase), N-methyl-D-glucamine dithiocarbamate complex with iron ion (II) (Fe2+(MGD)2, a trapping reagent of NO) or deferoxamine complex with iron ion (III) (Fe3+-deferoxamine, a scavenger of NO) produced a marked inhibition of the hepatotoxicity induced by cocaine. In addition, pretreatment with allopurinol (an inhibitor of xanthine oxidase) and 1,3-dimethylthiourea (a scavenger of hydroxyl radical) also produced a potent inhibition. These findings suggest that a hydroxyl radical produced by the reaction of NO and superoxide anion (O2-) via peroxynitrite may be involved in the pathogenesis of cocaine hepatotoxicity.
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PMID:Cocaine-induced liver injury in mice is mediated by nitric oxide and reactive oxygen species. 938 53

Oxidant stress has been implicated as playing a role in the pathogenesis of cholestatic liver injury. The objective of this study was to determine whether the xanthine oxidase/xanthine dehydrogenase enzyme system was involved in this oxidant stress. Adult Sprague-Dawley rats were treated with the xanthine oxidase inhibitor, oxypurinol, and randomized to bile duct ligation or sham surgery; vehicle-treated, sham-operated rats served as controls. After 5 d of bile duct ligation, serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and total and direct bilirubin concentrations were significantly elevated, and increased lipid peroxidation of hepatic mitochondria and microsomes was present. Treatment with oxypurinol reduced the aspartate aminotransferase, alanine aminotransferase, and bilirubin values by 26-47% but did not alter the increased lipid peroxidation of mitochondria and microsomes. Serum vitamin E:total lipids ratio was also reduced in both bile duct-ligated groups, consistent with oxidant injury. These data show that inhibition of xanthine oxidase reduces biochemical evidence of hepatocellular injury during bile duct ligation without affecting oxidant damage to intracellular hepatocyte organelles. Thus, in this model a component of cholestatic injury appears to have been caused by oxidant stress from a source outside of the hepatocyte.
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PMID:Effect of oxypurinol, a xanthine oxidase inhibitor, on hepatic injury in the bile duct-ligated rat. 972 20

Free radical formation caused by chronic ethanol administration could activate transcription factors such as nuclear factor-kappaB (NF-kappaB), which regulates production of inflammatory cytokines. Xanthine oxidase is one potential source of reactive oxygen species. Therefore, the purpose of this study is to determine whether allopurinol, a xanthine oxidase inhibitor and scavenger of free radicals, would affect free radical formation, NF-kappaB activation, and early alcohol-induced liver injury in rats. Male Wistar rats were fed a high-fat diet with or without ethanol (10-16 g/kg/day) continuously for up to 4 weeks with the Tsukamoto-French enteral protocol. Either allopurinol or saline vehicle was administered daily. Allopurinol had no effect on body weight or the cyclic pattern of ethanol in urine. Mean urine ethanol concentrations were 271 +/- 38 and 252 +/- 33 mg/dl in ethanol- and ethanol + allopurinol-treated rats, respectively. In the control group, serum aspartate aminotransferase and alanine aminotransferase levels were approximately 40 I.U./l and 25 U/l, respectively. Administration of enteral ethanol for 4 weeks increased serum transaminases approximately 5-fold. Allopurinol blunted these increases significantly by approximately 50%. Ethanol treatment also caused severe fatty infiltration, mild inflammation, and necrosis. These pathological changes also were blunted significantly by allopurinol. Furthermore, enteral ethanol caused free radical adduct formation, values that were reduced by approximately 40% by allopurinol. NF-kappaB binding was minimal in the control group but was increased significantly nearly 2.5-fold by ethanol. This increase was blunted to similar values as control by allopurinol. These results indicate that allopurinol prevents early alcohol-induced liver injury, most likely by preventing oxidant-dependent activation of NF-kappaB.
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PMID:Allopurinol prevents early alcohol-induced liver injury in rats. 1073 82

We have shown previously that rats subjected to tourniquet shock develop an acute form of remote organ injury of the liver that is both Kupffer cell (KC) and polymorphonuclear (PMN) leukocyte dependent. Circulating plasma xanthine oxidase (XO) has been shown to be responsible for the development of endothelial dysfunction and for remote organ injury of the lung and intestine after ischemia-reperfusion protocols. We now hypothesize that XO is released from rat hind limbs upon reperfusion and that it is responsible for KC and PMN leukocyte activation in this shock model. Our results show that about 30% of rat gastrocnemius muscle xanthine dehydrogenase (XD) is converted to XO during the 5-h tourniquet period and that it is released into the femoral vein within 10 min of reperfusion. Total muscle xanthine oxidoreductase activity (XO + XD) decreases within 30 min of reperfusion and is paralleled by a corresponding increase in femoral vein lactic dehydrogenase. In addition, liver tissue XO increases significantly within 30 min of reperfusion without a corresponding conversion of endogenous XD. Conversion of hepatic XD becomes evident 60 min after reperfusion is initiated, as does XO, and alanine aminotransferase (ALT) release into the hepatic vein, presumably from damaged hepatocytes as a consequence of oxidative stress. Tissue myeloperoxidase activity also increases significantly after the 60-min reperfusion period. That XO mediates KC and PMN activation is supported by the following observations: a) the close relationships between plasma XO and the time courses of tumor necrosis factor-alpha TNFalpha release into the hepatic vein and colloidal carbon clearance by KCs; b) that colloidal carbon clearance, TNFalpha and ALT release, loss of tissue free thiols, lipid peroxidation (TBARS), and liver infiltration by PMN neutrophils can also be induced by the administration of exogenous XO to normal rats; and c) pretreatment of rats with allopurinol inhibits KC activation and liver leukocyte infiltration. These results suggest that XO, released from the ischemic limb on reperfusion, is taken up by the liver were it mediates KC and PMN neutrophil activation and thus contributes to the development of multiple system organ failure after hind limb reperfusion.
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PMID:Xanthine oxidase released from reperfused hind limbs mediate kupffer cell activation, neutrophil sequestration, and hepatic oxidative stress in rats subjected to tourniquet shock. 1109 91

Plasma xanthine oxidase (XO) activity was defined as a source of enhanced vascular superoxide (O(2)( *-)) and hydrogen peroxide (H(2)O(2)) production in both sickle cell disease (SCD) patients and knockout-transgenic SCD mice. There was a significant increase in the plasma XO activity of SCD patients that was similarly reflected in the SCD mouse model. Western blot and enzymatic analysis of liver tissue from SCD mice revealed decreased XO content. Hematoxylin and eosin staining of liver tissue of knockout-transgenic SCD mice indicated extensive hepatocellular injury that was accompanied by increased plasma content of the liver enzyme alanine aminotransferase. Immunocytochemical and enzymatic analysis of XO in thoracic aorta and liver tissue of SCD mice showed increased vessel wall and decreased liver XO, with XO concentrated on and in vascular luminal cells. Steady-state rates of vascular O(2)( *-) production, as indicated by coelenterazine chemiluminescence, were significantly increased, and nitric oxide (( *)NO)-dependent vasorelaxation of aortic ring segments was severely impaired in SCD mice, implying oxidative inactivation of ( *)NO. Pretreatment of aortic vessels with the superoxide dismutase mimetic manganese 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin markedly decreased O(2)( small middle dot-) levels and significantly restored acetylcholine-dependent relaxation, whereas catalase had no effect. These data reveal that episodes of intrahepatic hypoxia-reoxygenation associated with SCD can induce the release of XO into the circulation from the liver. This circulating XO can then bind avidly to vessel luminal cells and impair vascular function by creating an oxidative milieu and catalytically consuming (*)NO via O(2)( small middle dot-)-dependent mechanisms.
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PMID:Oxygen radical inhibition of nitric oxide-dependent vascular function in sickle cell disease. 1180 11

Increasing evidence regarding free-radical generating agents and the inflammatory process suggests that accumulation of reactive oxygen species (ROS) can involve hepatotoxicity. Previously, we found that protocatechuic acid (PCA), a polyphenolic compound from Hibiscus sabdariffa L. possessing free radical-scavenging capacity, protected against oxidative damage induced by tert-butylhydroperoxide (t-BHP) in rat primary hepatocytes. In this study, first PCA was evaluated by its capacity of inhibiting xanthine oxidase (XO) and lipoxygenase (LO) activity in vitro, then it was used to induce hepatotoxicity to assess the antioxidant and anti-inflammatory bioactivity of PCA in vivo. Our investigation showed that pretreatment with PCA (50-100 mg/kg) by gavage for 5 days before a single dose of t-BHP (ip; 0.2 mmol/kg ) significantly lowered serum levels of the hepatic enzyme markers lactate dehydrogenase (LDH) and alanine (ALT) and aspartate (AST) aminotransferase, and reduced oxidative stress of the liver by evaluating malondialdehyde (MDA) and glutathione (GSH). Histopathological evaluation of the rat livers revealed that PCA reduced the incidence of liver lesions, including hepatocyte swelling, leukocyte infiltration, and necrosis induced by t-BHP. In addition, PCA inhibited t-BHP-induced tyrosine phosphorylation, an implication of the activation of a stress signal pathway, in the liver. These results indicate that PCA protects against t-BHP-induced hepatotoxicity by its antioxidant and anti-inflammatory characteristics accompanied by blocking of stress signal transduction.
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PMID:In vivo protective effect of protocatechuic acid on tert-butyl hydroperoxide-induced rat hepatotoxicity. 1195 69

Many studies indicate that oxygen free-radical formation after reoxygenation of liver may initiate the cascade of hepatocellular injury. It has been demonstrated that controlled ozone administration may promote an oxidative preconditioning or adaptation to oxidative stress, preventing the damage induced by reactive oxygen species (ROS) and protecting against liver ischaemia-reperfusion (I/R) injury. On the basis of those results we postulated that ozone treatment in our experimental conditions has biochemical parameters similar to the ischaemic preconditioning (IscheP) mechanism. Four groups of rats were classified as follows: (1) sham-operated animals subjected to anaesthesia and laparotomy, plus surgical manipulation; (2) I/R animals were subjected to 90 min of right-lobe hepatic ischaemia, followed by 90 min of reperfusion; (3) IscheP, previous to the I/R period (as in group 2): animals were subjected to 10 min of ischaemia and 10 min of reperfusion; (4) ozone oxidative preconditioning (OzoneOP), previous to the I/R period (as in group 2): animals were treated with ozone by rectal insufflation 1 mg kg (-1). The rats received 15 ozone treatments, one per day, of 5-5.5 ml at the ozone concentration of 50 microg ml (-1). The following parameters were measured: serum transaminases (AST, ALT) and 5'-nucleotidase (5 '-NT), with morphological determinations, as indicators or hepatocellular injury; total sulfhydryl groups, calcium levels and calpain activity as mediators which take part in xanthine deshydrogenase (XDH) conversion to xanthine oxidase (XO) (reversible and irreversible forms, respectively); XO activities and malondialdehyde + 4-hydroyalkenals as indicators of increased oxidative stress. AST, ALT levels were attenuated in the IscheP (130 +/- 11.4 and 75 +/- 5.7 U l (-1)) with regard to the I/R group (200 +/- 22 and 117 +/- 21.7 U l (-1)) while the OzoneOP maintained both of the enzyme activities ( 89.5 +/- 12.6 and 43.7 +/- 10 U l (-1)) without statistical differences (P< 0.05) in comparison with the sham-operated ( 63.95 +/- 11 and 19.48 +/- 3.2 U l (-1)). Protective effects of both the preconditioning settings on the preservation of total sylfhydryl groups (IscheP: 6.28 +/- 0.07, OzoneOP: 6.34 +/- 0.07 micromol mg prot (-1)), calcium concentrations (IscheP: 0.18 +/- 0.09, OzoneOP: 0.20 +/- 0.06 micromol mg prot (-1)), and calpain activity (IscheP: 1.04 +/- 0.58, OzoneOP: 1.41 +/- 0.79 U mg prot (-1)) were observed. Both of the preconditionings attenuated the increase of total XO associated to I/R injury. Generation of malondialdehyde + 4 hydroxyalkenals was prevented by IscheP and OzoneOP without statistical differences between the two protective procedures. These results provide evidence that both of the preconditioning settings share similar biochemical mechanisms of protection in the parameters which were measured. Although there were no differences from a biochemical point of view between Ischaemic and OzoneOPs, the histological results showed a more effective protection of OzoneOP than IscheP in our experimental conditions.
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PMID:Similar protective effect of ischaemic and ozone oxidative preconditionings in liver ischaemia/reperfusion injury. 1203 Jul 98

Fatty livers of obese fa/fa rats are vulnerable to injury when challenged by insults such as endotoxin, ischemia-reperfusion or acute ethanol treatment. The objective of this study was to evaluate whether a high-fat diet can act as a "second hit" and cause progression to liver injury in obese fa/fa rats compared with lean Fa/? rats. Accordingly, obese fa/fa rats and their lean littermates were fed a diet low in fat (12% of total calories) or a diet with 60% calories as lard for 8 weeks. Hyperglycemia and steatohepatitis occurred in the fa/fa rats fed the high-fat diet. This was accompanied by liver injury as assessed by alanine aminotransferase, hematoxilin and eosin staining, increased TNFalpha and stellate cell-derived TGFbeta, collagen deposition, and up-regulation of alpha-smooth muscle actin. Active MMP13 decreased in fa/fa rats independently of the diet, and TIMP1 expression increased with the high-fat diet, especially in fa/fa rats. Although UCP2 expression was higher in fa/fa rats regardless of the diet, minor changes in ATP levels were observed. Oxidative stress occurred in the fa/fa rats fed the high-fat diet as lipid peroxidation and protein carbonyls were elevated, while glutathione and antioxidant enzymes were very low. Expression and activity of cytochrome P450 2E1 and xanthine oxidase activity were down-regulated in fa/fa compared with Fa/? rats, and no effect was seen by the high-fat diet. However, NADPH oxidase activity increased 2.5-fold in fa/fa rats fed with the high-fat diet. In summary, a high-fat diet induces liver injury in fa/fa rats leading to periportal fibrosis. A role for oxidative stress is suggested via increased NADPH oxidase activity, lipid peroxidation, protein carbonyl formation, and low antioxidant defense.
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PMID:A high-fat diet leads to the progression of non-alcoholic fatty liver disease in obese rats. 1552 5

The aim of this study was to determine whether nuclear factor-kappaB (NF-kappaB) inhibitors are efficient against hepatic ischemia/reperfusion (I/R) injury. We previously demonstrated that xanthine oxidase-derived reactive oxygen species activate NF-kappaB during ischemia. However, the role of NF-kappaB activation during ischemia in post-reperfusion injury remains unclear. Therefore, while we examined the effects of NF-kappaB inhibitors, sulfasalazine and pyrrolidinedithiocarbamate on hepatic I/R injury using a rat lobar hepatic I/R model, we estimated the relationship between NF-kappaB activation during ischemia and following hepatic damage caused by reperfusion. The portal vein and the hepatic artery were clamped for 1 hr followed by reperfusion for up to 24 hr. NF-kappaB activation was determined by Western blot analysis. NF-kappaB activation was observed in the ischemic lobe of the liver, and the activation was prevented by pre-administration with NF-kappaB inhibitors. Although the serum ALT level, hepatic MPO activity and BSP clearance, as an index of hepatic injury, were increased after reperfusion, the increase was attenuated by pre-administration with NF-kappaB inhibitors. These findings suggest that NF-kappaB activation during ischemia is relevant to hepatic I/R injury. Moreover, we first showed that pre-administration with NF-kappaB inhibitors is effective against hepatic I/R injury.
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PMID:Inhibiton of NF-kappaB activation during ischemia reduces hepatic ischemia/reperfusion injury in rats. 1592 58


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