Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0239946 (liver fibrosis)
 8,268 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Livers from aryl hydrocarbon receptor-null mice showed a 3-fold increase in retinoids and a 65% decrease in retinoic acid metabolism. Levels of expression of the retinoic acid 4-hydroxylase, P450RAI, did not change, whereas cytochrome P4501A2 levels were lower in the null mouse, as shown earlier; however, this enzyme was found not to be active toward retinoic acid. These data suggest that aryl hydrocarbon receptor controls retinoic acid catabolism, through modulation of an unidentified target gene. Aldehyde dehydrogenases 1 and 2 were down-regulated markedly in the aryl hydrocarbon receptor-deficient mouse liver. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induced cytochrome P4501A2 but not the aldehyde dehydrogenases in wild-type mice, suggesting that aryl hydrocarbon receptor is not involved directly in the down-regulation of this gene. Transglutaminase II, a retinoic acid-responsive gene product, was increased 2-fold, consistent with the liver fibrosis phenotype observed in the null mice. These findings suggest a molecular connection between xenobiotic-activated receptor signaling and retinoid homeostasis.
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PMID:Aryl hydrocarbon receptor knockout mice (AHR-/-) exhibit liver retinoid accumulation and reduced retinoic acid metabolism. 923 Jan 84

Liver fibrosis and its end-stage disease cirrhosis are a main cause of mortality and morbidity worldwide. Thus far, there is no efficient pharmaceutical intervention for the treatment of liver fibrosis. Liver fibrosis is characterized by excessive accumulation of the extracellular matrix (ECM) proteins. Transglutaminase (TG)-mediated covalent cross-linking has been implicated in the stabilization and accumulation of ECM in a number of fibrotic diseases. Thus, the use of tissue TG2 inhibitors has potential in the treatment of liver fibrosis. Recently, we introduced a novel group of site-directed irreversible specific inhibitors of TGs. Here, we describe the development of a liposome-based drug-delivery system for the site-specific delivery of these TG inhibitors into the liver. By using anionic or neutral-based DSPC liposomes, the TG inhibitor can be successfully incorporated into these liposomes and delivered specifically to the liver. Liposomes can therefore be used as a potential carrier system for site-specific delivery of the TG2 inhibitors into the liver, opening up a potential new avenue for the treatment of liver fibrosis and its end-stage disease cirrhosis.
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PMID:Targeted delivery of a novel group of site-directed transglutaminase inhibitors to the liver using liposomes: a new approach for the potential treatment of liver fibrosis. 2106 61

Transglutaminase 2 (TG2) is primarily known as the most ubiquitously expressed member of the transglutaminase family with Ca(2+)-dependent protein crosslinking activity; however, this enzyme exhibits multiple additional functions through GTPase, cell adhesion, protein disulfide isomerase, kinase, and scaffold activities and is associated with cell growth, differentiation, and apoptosis. TG2 is found in the extracellular matrix, plasma membrane, cytosol, mitochondria, recycling endosomes, and nucleus, and its subcellular localization is an important determinant of its function. Depending upon the cell type and stimuli, TG2 changes its subcellular localization and biological activities, playing both anti- and pro-apoptotic roles. Increasing evidence indicates that the GTP-bound form of the enzyme (in its closed form) protects cells from apoptosis but that the transamidation activity of TG2 (in its open form) participates in both facilitating and inhibiting apoptosis. A difficulty in the study and understanding of this enigmatic protein is that opposing effects have been reported regarding its roles in the same physiological and/or pathological systems. These include neuroprotective or neurodegenerative effects, hepatic cell growth-promoting or hepatic cell death-inducing effects, exacerbating or having no effect on liver fibrosis, and anti- and pro-apoptotic effects on cancer cells. The reasons for these discrepancies have been ascribed to TG2's multifunctional activities, genetic variants, conformational changes induced by the immediate environment, and differences in the genetic background of the mice used in each of the experiments. In this article, we first report that TG2 has opposing roles like the protagonist in the novel Dr. Jekyll and Mr. Hyde, followed by a summary of the controversies reported, and finally discuss the possible reasons for these discrepancies.
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PMID:Transglutaminase 2 has opposing roles in the regulation of cellular functions as well as cell growth and death. 2725 8