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)

The role of nitric oxide (NO) and peroxynitrite in the process of neutrophil adhesion and infiltration was investigated in a model of hepatic ischemia-reperfusion. Male Fischer rats were subjected to 30 min of hepatic no-flow ischemia followed by 4 h of reperfusion (I/R). I/R induced liver injury as evidenced by a 13.7-fold increase in plasma alanine aminotransferase activity. Induction of liver injury was associated with an increase in neutrophil accumulation in ischemic lobes of livers [215 +/- 27 polymorphonuclear neutrophil leukocytes/50 high-power field (HPF), P < .05 compared with sham control] and 8-fold augmentation of inducible NO synthase (NOS) activity. However, NO levels in the liver decreased; this decrease may be caused by peroxynitrite formation by the reaction of NO with superoxide. Sections of ischemic lobes of the liver tissue of I/R animals exhibited marked immunoreactivity with anti-nitrotyrosine antibody, which indicates the presence of nitrotyrosine. Administration of Nw-nitro-L-arginine methyl ester (10 mg/kg i.v. before reperfusion) attenuated total and inducible NOS activity in both ischemic and nonischemic lobes of liver, and reduced NO levels in plasma and liver. However, NOS inhibition aggravated liver injury as alanine aminotransferase increased by 61% compared with rats subjected to reperfusion injury. Neutrophil accumulation was enhanced in ischemic (436 +/- 48/50 HPF, P < .05 compared with I/R animal) and nonischemic lobes of livers (34 +/- 3.2/50 HPF, P < .05 compared with sham control). NOS inhibition also attenuated immunohistochemically detected nitrotyrosine formation, but increased superoxide production in the liver. The NO-dependent regulation of neutrophil accumulation in the liver may be linked closely to P-selectin and intracellular adhesion molecule-1 expression because inhibition of NOS resulted in significant increases in gene expression of these two adhesion molecules (determined by reverse transcription-polymerase chain reaction analysis). These results suggest that NO is important in attenuating neutrophil accumulation and liver damage in ischemia-reperfusion injury. Inhibition of NOS activity reduces peroxynitrite formation but aggravates liver injury and increases neutrophil accumulation, which suggests that the anti-inflammatory function of NO is more important than the cytotoxic potential of peroxynitrite in acute inflammation.
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PMID:Inhibition of nitric oxide synthase attenuates peroxynitrite generation, but augments neutrophil accumulation in hepatic ischemia-reperfusion in rats. 949 76

The anti-inflammatory role of nitric oxide (NO) was studied in a model of hepatic ischemia-reperfusion (I/R) in rats. Male Fischer rats were subjected to 30 min of no-flow ischemia of the left and median lobes of the liver, and animals were examined for a 4-h period of reperfusion. The animals were divided into the following groups: control-vehicle; I/R-vehicle; I/R-Nomega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv, 10 min before reperfusion); sham control-L-NAME, and I/R-S-nitroso-N-acetyl-penicillamine (SNAP, 25 micromol/kg iv, 10 min before reperfusion, followed by 20 micromol. kg-1. h-1 in 1.0 ml saline infused for 4 h). Results showed that mean arterial blood pressure was significantly increased in the sham control-L-NAME or I/R-L-NAME groups compared with either the I/R-vehicle or I/R-SNAP groups. However, cardiac index (CI) and stroke volume index (SVI) were markedly decreased, and systemic vascular resistance index (SVRI) was dramatically increased. Interestingly, the CI and SVI in rats treated with SNAP were markedly improved over that of the I/R group. Plasma nitrate and nitrite levels were significantly decreased in the I/R-L-NAME group; however, superoxide generation in the ischemic lobes and plasma alanine aminotransferase activity were higher compared with I/R-SNAP rats. The L-NAME-induced enhancement of hepatic injury in rats with I/R may be due in part to neutrophil infiltration, which was significantly increased compared with animals subjected to I/R or I/R-SNAP. The mechanism of L-NAME-enhanced neutrophil infiltration may be due to the fact that the ratios of P-selectin and intercellular adhesion molecule 1 (ICAM-1) mRNA to glyceraldehyde-3-phosphate dehydrogenase mRNA extracted from the ischemic lobes of I/R-L-NAME rats were significantly increased when compared with the I/R-SNAP group. These results suggest that 1) endogenous NO reduces the SVRI and permits an increased CI and SVI; 2) exogenous NO further improves CI and SVI; and 3) endogenous, but not exogenous, NO decreases P-selectin and ICAM-1 mRNA expression, thereby reducing polymorphonuclear neutrophil-dependent reperfusion tissue injury.
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PMID:NO modulates P-selectin and ICAM-1 mRNA expression and hemodynamic alterations in hepatic I/R. 984 19

Hyperacute rejection (HAR) occurring after transplantation within phylogenetically distant species is a severe reaction triggered by preexisting xenoreactive antibodies and complement activation, leading to the destruction of the donor organ. Expression of human complement inhibitors in transgenic pig organs prolongs the survival of xenograft in experimental models. Moreover, the extent of protection from hyperacute rejection is dependent on the level and site of expression of the transgenic molecules and, probably, on the combination of different molecules. In this regard a small animal model to test the efficacy of expression vectors and different human molecules could be very advantageous. A murine model developed in our laboratory was characterized by measurement of several parameters characteristic of HAR in the livers of control and transgenic mice expressing transgenic human DAF (CD55) or MCP (CD46) at the end of 2 h of perfusion with human plasma and after I day. The parameters studied were heamatological values of hepatic functions (GOT and GPT), induction of pro-inflammatory molecules and histopathological evaluation. Cytokines (IL-1alpha, IL-1beta, IL-6) induction and exposure of P-selectin on the endothelial cell surface, was only observed in control animals after 2 h of perfusion, as an early event. GOT and GPT values increase dramatically after 2 h perfusion and 1 day after the treatment according to the histopathological observation of liver damage. On the contrary, the livers of hDAF or hMCP transgenic mice, under the same treatment were significantly protected although the extent of this protection is dependent on the level of expression of transgenic human molecules.
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PMID:An in vivo model of hyperacute rejection: characterization and evaluation of the effect of transgenic human complement inhibitors. 1103 69

Neutrophils can cause parenchymal cell injury in the liver during ischemia-reperfusion and endotoxemia. Neutrophils relevant for the injury accumulate in sinusoids, transmigrate, and adhere to hepatocytes. To investigate the role of E- and L-selectin in this process, C3Heb/FeJ mice were treated with 700 mg/kg galactosamine and 100 microgram/kg endotoxin (Gal/ET). Immunogold labeling verified the expression of E-selectin on sinusoidal endothelial cells 4 hours after Gal/ET injection. In addition, Gal/ET caused up-regulation of Mac-1 (CD11b/CD18) and shedding of L-selectin from circulating neutrophils. Gal/ET induced hepatic neutrophil accumulation (422 +/- 32 polymorphonuclear leukocytes [PMN]/50 high power fields [HPF]) and severe liver injury (plasma alanine transaminase [ALT] activities: 4,120 +/- 960 U/L; necrosis: 44 +/- 3%) at 7 hours. Treatment with an anti-E-selectin antibody (3 mg/kg, intravenously) at the time of Gal/ET administration did not significantly affect hepatic neutrophil accumulation and localization. However, the anti-E-selectin antibody significantly attenuated liver injury as indicated by reduced ALT levels (-84%) and 43% less necrotic hepatocytes. In contrast, animals treated with an anti-L-selectin antibody or L-selectin gene knock out mice were not protected against Gal/ET-induced liver injury. However, E-, L-, and P-selectin triple knock out mice showed significantly reduced liver injury after Gal/ET treatment as indicated by lower ALT levels (-65%) and reduced necrosis (-68%). Previous studies showed that circulating neutrophils of E-selectin-overexpressing mice are primed and activated similar to neutrophils adhering to E-selectin in vitro. Therefore, we conclude that blocking E-selectin or eliminating this gene may have protected against Gal/ET-induced liver injury in vivo by inhibiting the full activation of neutrophils during the transmigration process.
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PMID:Pathophysiologic importance of E- and L-selectin for neutrophil-induced liver injury during endotoxemia in mice. 1105 49

In the present study, we examined the effects of peroxynitrite on reperfusion injury using a rat model of hepatic ischemia-reperfusion (HI/R). The left and median lobes of the liver were subjected to 30 min of ischemia, followed by 4 h of reperfusion. Groups A and B rats were sham-operated controls that received vehicle or peroxynitrite; groups C and D rats were subjected to HI/R and received peroxynitrite or vehicle, respectively. A dose of 2 micromol/kg body wt of peroxynitrite, diluted in saline (pH 9.0, 4 degrees C), was administered as a bolus through a portal vein catheter at 0, 60, and 120 min after reperfusion. Results showed that superoxide generation in the ischemic lobes of the liver and plasma alanine aminotransferase (ALT) activity of group C were decreased by 43% and 45%, respectively, compared with group D. Leukocyte accumulations in the ischemic lobes of liver and circulating leukocytes were decreased by 40% and 27%, respectively, in group C vs. D. The ratios of mRNA of P-selectin and intercellular adhesion molecule-1 (ICAM-1) to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA extracted from the ischemic lobes of the liver of group C were decreased compared with group D. There were no differences between the groups A and B in terms of plasma ALT activity, circulating leukocytes, superoxide generation, and leukocyte infiltration in the ischemic lobes of the liver. Moreover, hemodynamic parameters (i.e., mean arterial blood pressure, cardiac index, stroke index, and systemic vascular resistance) were not significantly different among groups B, C, and D. These results suggest that administration of peroxynitrite via the portal vein only has a local effect. Exogenous peroxynitrite at physiological concentrations attenuates leukocyte-endothelial interaction and reduces leukocyte infiltration. The mechanism of the reduction of leukocyte infiltration into ischemic lobes of the liver appears because of decreased expression of mRNA of P-selectin and ICAM-1. The net effect of administration of peroxynitrite may be to reduce adhesion molecule-mediated, leukocyte-dependent reperfusion injury.
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PMID:Peroxynitrite attenuates hepatic ischemia-reperfusion injury. 1107 13

The overall objective of this study was to determine whether genetically induced hypercholesterolemia alters the inflammatory and microvascular responses of mouse liver to ischemia-reperfusion (I/R). The accumulation of rhodamine 6G-labeled leukocytes and the number of nonperfused sinusoids (NPS) were monitored (by intravital microscopy) in the liver of wild-type (WT) and low-density lipoprotein receptor-deficient (LDLr(-/-)) mice for 1 h after a 30-min period of normothermic ischemia. Plasma alanine transaminase (ALT) levels were used to monitor hepatocellular injury. Microvascular leukostasis as well as increases in NPS and plasma ALT were observed at 60 min after hepatic I/R in both WT and in LDLr(-/-) mice; however, these responses were greatly exaggerated in LDLr(-/-) mice. Pretreatment of LDLr(-/-) mice with gadolinium chloride, which reduces Kupffer cell function, attenuated the hepatic leukostasis, NPS, and hepatocellular injury elicited by I/R. Similar protection against I/R was observed in LDLr(-/-) mice pretreated with antibodies directed against tumor necrosis factor-alpha, intercellular adhesion molecule-1 (ICAM-1), or P-selectin. These findings indicate that chronic hypercholesterolemia predisposes the hepatic microvasculature to the deleterious effects of I/R. Kupffer cell activation and the leukocyte adhesion receptors ICAM-1 and P-selectin appear to contribute to the exaggerated inflammatory responses observed in the postischemic liver of LDLr(-/-) mice.
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PMID:Hepatic microvascular responses to ischemia-reperfusion in low-density lipoprotein receptor knockout mice. 1109 49

Neutrophil adhesion and recruitment represents one of the early cellular events that occur during hepatic ischemia/reperfusion (IR) injury and plays a critical role in determining the extent of tissue damage. The adhesion molecules, such as selectins and intercellular adhesion molecules (ICAM), are important in mediating neutrophil-endothelial cell interactions and neutrophil emigration. The goal of this study was to evaluate the role of P-selectin and ICAM-1 in hepatic IR injury. Male wild-type and P-selectin/ICAM-1-deficient (P/I null) mice underwent 90 minutes of partial hepatic ischemia followed by reperfusion at various time points (0, 1.5, 3, and 6 hours). Reperfusion caused a time-dependent hepatocellular injury in both wild-type and P/I null mice as judged by plasma alanine aminotransferase (ALT) levels and liver histopathology examination. Although ALT levels were slightly lower in the P/I null mice compared with the wild-type mice the differences were not statistically significant. Neutrophil infiltration to the ischemic liver was observed in both mouse groups after 6 hours of reperfusion; however, the infiltration to the midzonal region of the ischemic liver was more pronounced in the wild-type group. This study suggests that hepatocellular injury induced after hepatic IR was independent of P-selectin and ICAM-1 in this model of acute inflammatory tissue injury.
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PMID:Hepatic ischemia/reperfusion injury in P-selectin and intercellular adhesion molecule-1 double-mutant mice. 1151 May 73

There is a close relationship between inflammatory bowel disease (IBD) and various hepatobiliary disorders. The objective of this study was to determine whether hepatic leukocyte recruitment occurs in experimental colitis. We used the murine model of colitis induced by 2,4-dinitrobenezenesulfonic acid (DNBS). Male C57Bl/6 mice received an intrarectal injection of 4 mg DNBS in 100 microl 50% ethanol. Controls received 100 microl 50% ethanol. The hepatic microcirculation was examined at 3 and 14 days post-DNBS by intravital video microscopy. Three days post-DNBS, when mice had developed acute colitis, there was associated hepatic leukocyte recruitment. Within the postsinusoidal venules there was a fourfold increase in the flux of rolling leukocytes that was P-selectin dependent but not alpha(4)-integrin dependent. There was also an increase in stationary leukocytes within the sinusoids, although this was not associated with an increase in serum alanine transaminase. By 14 days post-DNBS when macroscopic evidence of colonic inflammation was resolved, rolling within the postsinusoidal venules had returned to control levels. In this murine model of colitis, we describe a link between acute colonic inflammation and remote hepatic leukocyte recruitment that is P-selectin dependent. Active IBD may lead to remote hepatic inflammation.
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PMID:Hepatic leukocyte recruitment in a model of acute colitis. 1218 Nov 68

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear transcription factor that comprises the primary molecular target for thiazolidinedione (TZD) insulin-sensitizing drugs. Whilst expressed in many tissues in humans, its abundant expression in adipose tissue is believed to be the focal point through which TZDs regulate genes involved in glucose and lipid metabolism and via which these agents ultimately improve the hyperglycemia of type 2 diabetes. However, TZDs exhibit many additional properties, not least an array of effects which suggest a broad attack on the inflammatory process. Thus, TZDs have been shown to reduce plasma levels of the chemokine, monocyte chemotactic protein-1 (MCP-1), the anti-fibrinolytic protein, plasminogen activator inhibitor-1 (PAI-1), the endothelial cell adhesion molecules, e-selectin and inter-cellular adhesion molecule-1 (ICAM-1), the leucocyte-activating molecule, CD40L, and the tissue-remodeling enzyme, matrix metalloproteinase-9 (MMP-9). Further tangible evidence of a reduction by TZDs of systemic inflammation in patients with the classical metabolic syndrome stems from falls in the white blood cell count, P-selectin-positive platelets and in the acute-phase inflammatory proteins, C-reactive protein, serum amyloid A and fibrinogen. At the tissue level, TZDs improve vascular endothelial function, and reduce the rate of progression of intimal-medial thickening of the carotid artery and the microalbuminuria of type 2 diabetes. Further, TZDs have been shown to be efficacious in inflammatory diseases as wide-ranging as psoriasis, ulcerative colitis and non-alcoholic steatohepatitis (NASH). In the case of the latter, a broad spectrum of TZD-related properties is visible. Here, these drugs improve insulin sensitivity for glucose metabolism, reduce hyperinsulinemia, hepatic steatosis, inflammation and fibrosis, and lower the circulating levels of liver transaminases (ALT, AST), alkaline phosphatase and gamma glutamyl transferase. These effects in humans are also well-supported by investigative animal and in vitro studies. The ameliorative effects on liver fibrosis are of particular interest since they suggest that TZDs are able to activate a program of corrective tissue-remodeling. The basis for this action may be partly an ability to inhibit matrix protein secretion by hepatic stellate cells. An analogous action has also been seen in kidney mesangial cells. In conclusion, TZDs are important new drugs, presently indicated for the treatment of type 2 diabetes but with a spectrum of properties which suggests their potential for treating a number of degenerative inflammatory diseases, including NASH. However, full-scale, long-term clinical trials are needed with TZDs to test their potential to treat NASH, not least because of the (hepatotoxic) legacy of the prototype TZD, troglitazone, but also in view of the escalating burden of liver disease which is accompanying the increasing global prevalence of clinical obesity and type 2 diabetes.
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PMID:Thiazolidinediones: Pleiotropic drugs with potent anti-inflammatory properties for tissue protection. 1619 19

P-selectin glycoprotein ligand-1 (PSGL-1) mediates the initial tethering of leukocytes to activated platelets and endothelium. We report molecular cloning and characterization of the rat PSGL-1 gene. A neutralizing Ab was generated, and its binding epitope was mapped to the N-terminal binding region of rat PSGL-1. We examined the effects of early PSGL-1 blockade in rat liver models of cold ischemia, followed by ex vivo reperfusion or transplantation (orthotopic liver transplantation (OLT)) using an anti-PSGL-1 Ab with diminished Fc-mediated effector function. In the ex vivo hepatic cold ischemia and reperfusion model, pretreatment with anti-PSGL-1 Ab improved portal venous flow, increased bile production, and decreased hepatocellular damage. Rat pretreatment with anti-PSGL-1 Ab prevented hepatic insult in a model of cold ischemia, followed by OLT, as assessed by 1) decreased hepatocellular damage (serum glutamic oxaloacetic transaminase/glutamic-pyruvic transaminase levels), and ameliorated histological features of ischemia/reperfusion injury, consistent with extended OLT survival; 2) reduced intrahepatic leukocyte infiltration, as evidenced by decreased expression of P-selectin, ED-1, CD3, and OX-62 cells; 3) inhibited expression of proinflammatory cytokine genes (TNF-alpha, IL-1beta, IL-6, IFN-gamma, and IL-2); and 4) prevented hepatic apoptosis accompanied by up-regulation of antiapoptotic Bcl-2/Bcl-xL protective genes. Thus, targeting PSGL-1 with a blocking Ab that has diminished Fc-mediated effector function is a simple and effective strategy that provides the rationale for novel therapeutic approaches to maximize the organ donor pool through the safer use of liver transplants despite prolonged periods of cold ischemia.
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PMID:Molecular characterization of rat leukocyte P-selectin glycoprotein ligand-1 and effect of its blockade: protection from ischemia-reperfusion injury in liver transplantation. 1636 57


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