Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.2 (alanine aminotransferase)
 26,722 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modulator is an endogenous low-molecular weight regulator of both glucocorticoid and mineralocorticoid receptors, as well as protein kinase C. Analogs of the putative modulator structure have been synthesized. These compounds include 1-O-(3'-carboxypropyl) or (5'-carboxypentyl)-L-glycero-3-phospho-L-serine or L-threonine, and the D-glycerol stereoisomers. These compounds were tested for in vitro modulator activity using the glucocorticoid-receptor complex activation inhibition and steroid-binding stabilization assays. One of the ether phosphoglycerides, 1-O-(5'-carboxypentyl)-L-glycero-3-phospho-L-threonine (H-GPT-1), partially inhibited steroid-receptor complex activation in a dose-dependent manner. However, none of the other compounds exhibited any modulator activity towards the glucocorticoid-receptor complex. Like modulator, H-GPT-1 did not inhibit activated glucocorticoid-receptor complex binding to DNA-cellulose. Surprisingly, in contrast to modulator, H-GPT-1 partially inhibited unoccupied receptor steroid-binding in a dose-dependent manner. These results suggest that although modulator is not exactly mimicked by this compound, H-GPT-1 is the first synthetic organic molecule to exhibit some modulator activity towards the glucocorticoid receptor.
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PMID:A new synthetic ether aminophosphoglyceride exhibits partial modulator activity towards the glucocorticoid receptor. 807 85

Exposure of rat cortical neurons to the human immunodeficiency virus type 1 (HIV-1) coat protein gp120 in vitro causes a rise in the intracellular Ca2+ level and a subsequent translocation of protein kinase C (PKC) from the cytosol to the membrane. Such a translocation persists for at least 2 h, but only in cultures with media not depleted of endogenous glutamate. Enzymatic degradation of glutamate in the medium by the enzyme glutamate-pyruvate transaminase (GPT) abolishes the long-lasting effect of gp120 on the association state of PKC; under this incubation condition the translocation period is < 1 h. Memantine and the ganglioside GM1 prevent N-methyl D-aspartate receptor-mediated long-term translocation of PKC and gp120-mediated neurotoxicity (in the absence of GPT); they have no effect on short-term translocation of PKC. We suggest that gp120-caused neuronal death involves an indirect sensitization step of the NMDA receptors, which ultimately induces neuronal death.
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PMID:HIV-1 gp120 and NMDA induce protein kinase C translocation differentially in rat primary neuronal cultures. 845 39

The effects of calcitonin (CT) on oxyradical generation and cellular damage induced by carbon tetrachloride (CCl4) were investigated in rat hepatocytes. Addition of CCl4 to the cells concentration dependently increased intracellular production of hydroperoxides and release of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). The hepatocytes expressed mRNA for a CT receptor, C1b. Coaddition of CT to the cells concentration dependently suppressed the CCl4-induced increase in hydroperoxide production and also decreased the release of AST and ALT. The suppressive effect of CT on hydroperoxide production was reversed by further addition of H7 or by pretreatment with phorbol 12-myristate 13-acetate for 24 h. These results suggest that CT prevents CCl4-induced oxyradical production and cellular damage through activation of protein kinase C in hepatocytes.
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PMID:Calcitonin prevents CCl4-induced hydroperoxide generation and cytotoxicity possibly through C1b receptor in rat hepatocytes. 857 6

We have investigated the accumulation of diacylglycerol (DAG) induced by carbon tetrachloride (CCl4)-derived radicals in the liver of female Sprague-Dawley (SD) rats after intraperitoneally injecting CCl4. DAG is an intracellular activator of protein kinase C (PKC) which regulates cell proliferation and differentiation. The electron spin resonance (ESR) study gave the signal of the PBN-CCl3 adduct in the liver of the rats which were pretreated with PBN, confirming that CCl4 was metabolized into CCl3. radicals with cytochrome P450 enzyme and indicating that PBN could trap them. The blood biochemical assay supported the trapping of the CCl3. radicals; the pretreatment of rats with PBN inhibited the increase in the GOT and GPT values upon exposure to CCl4. The Fourier transform-infrared (FT-IR) study indicated in comparison with the model compounds that the CCl4-injected rats accumulated DAG in addition to phosphatidylcholine, phosphatidylethanolamine and triglyceride (TG) in the lipid membrane fraction of the liver homogenate. DAG was found to be ca. 10-15% of the membrane phospholipids by weight. However, DAG was not found in the lipid of the liver microsomes, suggesting that it is formed only in the cell membrane of liver. Also, neither DAG nor TG was found in the lipid membrane of the rats that were pretreated with PBN followed by an injection of CCl4. The formation of DAG was confirmed by an HPLC study. The activation of PKC was observed in liver homogenate in the rats that were injected with CCl4. On the basis of the above findings, it was concluded that the CCl4-derived radicals stimulate PKC through the accumulation of DAG in the liver membrane of the rats. Furthermore, it was shown that PBN has a protective and therapeutic effect against CCl4-induced damage.
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PMID:Accumulation of diacylglycerol induced by CCl4-derived radicals in rat liver membrane and its inhibition with radical trapping reagent--FT-IR spectroscopic and HPLC chromatographic observations. 1084 20

Effects of the dietary addition of orotic acid to a diet containing casein as a sole protein source on lipid levels in the liver and serum, activities of antioxidant enzymes in the liver, and some enzyme activities in serum, were compared with other diets containing egg protein, soy protein, or wheat gluten, respectively. 1. The contents in the liver of each lipid were increased by the addition of orotic acid as compared with those values without it. The orotic acid added to the casein diet caused accumulation of more liver total lipids, triacylglycerol, 1,2-diacylglycerol, and phospholipids than those fed three other diets. 2. The addition of orotic acid to the casein, but not to the other three diets, lowered the activities of liver superoxide dismutase and increased the activities of both serum ornithine carbamoyltransferase and alanine aminotransferase. Thus, the significant increase in serum ornithine carbamoyltransferase activities as the marker of liver lesions may result from the marked accumulation of liver lipids, decreased activities of hepatic superoxide dismutase, and the increased level of hepatic 1,2-diacylglycerol, followed by possibly the increased level of superoxide anion and increased activity of protein kinase C in rats fed the casein diet with orotic acid added.
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PMID:Orotic acid added to casein, but not to egg protein, soy protein, or wheat gluten diets increases 1,2-diacylglycerol levels and lowers superoxide dismutase activities in rat liver. 1175 5

The aim of this study was to evaluate the effect of cariporide, a selective Na(+)/H(+) exchange inhibitor, on isolated and cultured hepatic stellate cells (HSCs) and in 2 in vivo models of rat liver fibrosis. Platelet-derived growth factor (PDGF)-induced HSC proliferation, evaluated by measuring the percentage of bromodeoxyuridine-positive cells, was significantly inhibited by cariporide, with a maximal effect at 10 micromol/L. Incubation with cariporide did not inhibit PDGF-induced extracellular-regulated kinase 1/2 (ERK1/2), Akt (a downstream component of the phosphatidylinositol [PI]-3 kinase pathway), and protein kinase C (PKC) activation but reduced PDGF-induced activation of the Na(+)/H(+) exchanger, with a maximal effect at 10 micromol/L. Rats treated with dimethylnitrosamine (DMN; 10 mg/kg) for 1 and 5 weeks received a diet with or without 6 ppm cariporide. Treatment with cariporide reduced the degree of liver injury, as determined by alanine aminotransferase (ALT) values, also when administered after the induction of hepatic damage. This was associated with reduced HSC activation and proliferation and reduced collagen deposition, as determined by morphometric evaluation of alpha-smooth muscle actin (SMA)/proliferating cell nuclear antigen-positive cells and percentage of Sirius red-positive parenchyma, respectively. Moreover, cariporide was also able to reduce alpha(1)I procollagen messenger RNA (mRNA) expression. Similar effects were observed in bile duct-ligated (BDL) rats. In conclusion, selective inhibition of the Na(+)/H(+) exchanger by cariporide may represent an effective therapeutic strategy in the treatment of hepatic fibrosis.
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PMID:Selective Na+/H+ exchange inhibition by cariporide reduces liver fibrosis in the rat. 1254 Jul 75

Troglitazone was studied in pH-sensitive LLC-PK1-F+ cells to determine the effect on pHi and glutamine metabolism as well as the role of peroxisome proliferator-activated receptor (PPARgamma)-dependent and PPARgamma-independent signaling pathways. Troglitazone induces a dose-dependent cellular acidosis that occurs within 4 min and persists over 18 h as a result of inhibiting Na+/H+ exchanger-mediated acid extrusion. Cellular acidosis was associated with glutamine-dependent augmented [15N]ammonium production and decreased [15N]alanine formation from 15N-labeled glutamine. The shift in glutamine metabolism from alanine to ammoniagenesis appears within 3 h and is associated after 18 h with both a reduction in assayable alanine aminotransferase (ALT) activity as well as cellular acidosis. The relative contribution of troglitazone-induced cellular acidosis vs. the decrease in assayable ALT activity to alanine production could be demonstrated. The PPARgamma antagonist bisphenol A diglycide ether (BADGE) reversed both the troglitazone-induced cellular acidosis and ammoniagenesis but enhanced the troglitazone reduction of assayable ALT activity; BADGE also blocked troglitazone induction of peroxisome proliferator response element-driven firefly luciferase activity. The protein kinase C (PKC) inhibitor chelerythrine mimics troglitazone effects, whereas phorbol ester reverses the effects on ammoniagenesis consistent with troglitazone negatively regulating the DAG/PKC/ERK pathway. Although functional PPARgamma signaling occurs in this cell line, the major troglitazone-induced acid-base responses appear to be mediated by pathway(s) involving PKC/ERK.
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PMID:Troglitazone acts by PPARgamma and PPARgamma-independent pathways on LLC-PK1-F+ acid-base metabolism. 1450 76

Advanced glycation endproducts (AGEs) have been postulated to play a role in the development of both nephropathy and large vessel disease in diabetes. However, it is still not clear which AGE subtypes play a pathogenetic role and which of several AGE receptors mediate AGE effects on cells. This review summarises the renoprotective effect of inhibitors of AGE formation, including aminoguanidine, and of cross-link breakers, including ALT-711, on experimental diabetic nephropathy and on mesenteric vascular hypertrophy. It also demonstrates similar effects of aminoguanidine and ramipril (an angiotensin converting enzyme inhibitor) on fluorescent and immunoassayable AGE levels, renal protein kinase C activity, nitrotyrosine expression, lysosomal function, and protein handling in experimental diabetes. These findings indicate that inhibition of the renin angiotensin system blocks both upstream and downstream pathways leading to tissue injury. We postulate that the chemical pathways leading to advanced glycation endproduct formation and the renin angiotensin systems may interact through the generation of free radicals, induced both by glucose and angiotensin II. There is also evidence to suggest that AGE-dependent pathways may play a role in the development of tubulointerstitial fibrosis in the diabetic kidney. This effect is mediated through RAGE and is TGF-beta and CTGF-dependent.
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PMID:Evolving concepts in advanced glycation, diabetic nephropathy, and diabetic vascular disease. 1456 9

Several excitatory amino acid ligands were found potently to inhibit forskolin-stimulated cAMP accumulation in rat cultured cerebellar astrocytes: L-cysteine sulfinic acid (L-CSA) = L-aspartate > L-glutamate >/= the glutamate uptake inhibitor, L-PDC. This property did not reflect activation of conventional glutamate receptors, since the selective ionotropic glutamate receptor agonists NMDA, AMPA, and kainate, as well as several mGlu receptor agonists [(1S,3R)-ACPD, (S)-DHPG, DCG-IV, L-AP4, L-quisqualate, and L-CCG-I], were without activity. In addition, the mGlu receptor antagonists, L-AP3, (S)-4CPG, Eglu, LY341495, (RS)-CPPG, and (S)-MCPG failed to reverse 30 microM glutamate-mediated inhibitory responses. L-PDC-mediated inhibition was abolished by the addition of the enzyme glutamate-pyruvate transaminase. This finding suggests that the effect of L-PDC is indirect and that it is mediated through endogenously released L-glutamate. Interestingly, L-glutamate-mediated inhibitory responses were resistant to pertussis toxin, suggesting that G(i)/G(o) type G proteins were not involved. However, inhibition of protein kinase C (PKC, either via the selective PKC inhibitor GF109203X or chronic PMA treatment) augmented glutamate-mediated inhibitory responses. Although mGlu3 receptors (which are negatively coupled to adenylyl cyclase) are expressed in astrocyte populations, in our study Western blot analysis indicated that this receptor type was not expressed in cerebellar astrocytes. We therefore suggest that cerebellar astrocytes express a novel mGlu receptor, which is negatively coupled to adenylyl cyclase, and possesses an atypical pharmacological profile.
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PMID:Novel metabotropic glutamate receptor negatively coupled to adenylyl cyclase in cultured rat cerebellar astrocytes. 1499 8

Hydrophobic bile salts induce either necrosis or apoptosis depending on the severity of the injury caused by them. Since bile salt-induced apoptosis is influenced by Ca2+- and protein kinase-signaling pathways, and both necrosis and apoptosis share common initiating mechanisms, we analyzed whether these signaling cascades also influence bile salt-induced necrosis in isolated rat hepatocytes. Taurochenodeoxycholate (TCDC, 0.25-1.50 mM, 2 h) reduced, in a dose-dependent manner, the percentage of viable hepatocytes, and increased the release of the cytosolic enzyme, lactate dehydrogenase (LDH) and alanine aminotransferase (ALAT), and that of the plasma membrane enzyme, alkaline phosphatase (AP). The PKC inhibitors, H7 (100 microM) and chelerythrine (2.5 microM), both prevented significantly TCDC-induced necrosis. On the contrary, the PKA activator, dibutyryl-cAMP, exacerbated TCDC-induced cell damage in a dose-dependent manner; this effect was more likely due to cAMP-mediated PKA activation, as the PKA inhibitor, KT5720 (1 microM), counteracted this effect. Instead, the intracellular Ca2+ chelator, BAPTA/AM (20 microM), was without effect. TCDC (1 mM) increased lipid peroxidation from 0.7 +/- 0.2 to 7.5 +/- 0.9 nmol of malondialdehyde per mg of protein, p < 0.001; the addition of the free radical scavenger, diphenyl-p-phenylendiamine, completely blocked this increase and prevented significantly TCDC-induced necrosis. PKC inhibition induced only a slight attenuation of TCDC-induced lipid peroxidation. Possible mechanisms accounting for the modulatory effect of signal transduction pathways on TCDC-induced necrosis, including signaling influence on TCDC transport events and TCDC-induced oxidative stress, are discussed.
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PMID:Signaling modulation of bile salt-induced necrosis in isolated rat hepatocytes. 1549 97


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