Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Western societies roughly 50% of all cases of liver cirrhosis are related to alcohol abuse. The oxidative metabolite of ethanol, acetaldehyde, often in conjunction with viral or metabolic liver disease, is implicated as the major cause for liver fibrogenesis. Acetaldehyde damages cell membranes, initiates lipid peroxidation and forms noxious protein adducts, resulting in the activation of Kupffer cells and perisinusoidal lipocytes/portal fibroblasts. The activation of lipocytes and fibroblasts to a proliferative and collagen-producing myofibroblast-like phenotype is triggered by the release of fibrogenic factors such as platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) from the activated Kupffer cells. Due to the socioeconomic burden inflicted by cirrhosis, antifibrotic treatment is urgently needed. Strategies to prevent or reverse cirrhosis must interrupt the continuous process of pathological wound healing in the liver. An antifibrotic effect has been demonstrated for the interferons, prostaglandins E and relaxin. Polyunsaturated lecithin, silymarin and ursodeoxycholic acid, agents with a high hepatotropism and a good safety-profile, appear to have antifibrotic properties. Targeted approaches include the specific removal of matrix-bound fibrogenic growth factors and the induction of stress-relaxation of the activated mesenchymal cells by biologically active matrix-peptides and their stable analogues. Since serum tests for the non-invasive assessment of collagen synthesis and degradation in the liver are now available, rapid progress in the development and clinical application of antifibrotic drugs can be anticipated.
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PMID:Alcohol and liver fibrosis--pathobiochemistry and treatment. 852 60

Apolipoprotein A-I (Apo A-I), a protein produced mainly by hepatocytes, is decreased in the sera of alcoholic patients with liver fibrosis and cirrhosis. To explain this decrease, we investigated possible interactions between liver extracellular matrix (ECM) and Apo A-I. Using a solid-phase binding assay, we evaluated the binding of Apo A-I to the different liver matrix components. Apo A-I bound significantly to fibronectin (FN) (optical density [OD] = 1.11 +/- .26, P = .01) and collagen (C) I (OD = 0.91 +/- 0.22, P = .02) in comparison with bovine serum albumin (BSA) (OD = 0.26 +/- 0.16). Binding of Apo A-I to fibronectin was concentration dependent and saturable. Apo A-I bound also to ECM in vivo because Apo A-I was detected by immunofluorescence on fibrous septa in liver biopsy specimens of alcoholic patients. Because a negative correlation between Apo A-I and liver fibrosis is amplified in alcoholic patients, we investigated whether the in vitro formation of Apo A-I/acetaldehyde complex (adducts) increased the binding of Apo A-I to the ECM. We showed that the amount of Apo A-I that bound to FN was significantly higher with acetaldehyde-modified Apo A-I (OD = 2.18 +/- 0.19, P = .01) than with native Apo A-I. This increase was probably related to the formation and binding of Apo A-I dimers, because immunoblot of in vitro acetaldehyde-modified Apo A-I showed the formation of dimeric Apo A-I. In conclusion, FN binds both native and acetaldehyde-modified Apo A-I. Because FN is deposited early and in excess during liver fibrosis, a storage mechanism of Apo A-I on newly deposited fibronectin would explain, in part, the decrease observed in alcoholic patients with liver fibrosis.
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PMID:Binding of apolipoprotein A-I and acetaldehyde-modified apolipoprotein A-I to liver extracellular matrix. 862 Nov 58

Genetic factors may play a role in the development of alcoholic liver disease (ALD). Cytochrome P4502E1 (CYP2E1) catalyzes the oxidation of ethanol, producing acetaldehyde and free radicals capable of reacting with and peroxidizing cell membranes. Polymorphisms have been identified in the 5-flanking region of the CYP2E1 gene that may alter the transcriptional activity. In our laboratory, no difference in c1 and c2 allele frequencies was observed between alcoholic patients with or without liver disease in Caucasian men, but there is reported data to the contrary for other populations. To determine if there is a differential susceptibility to ALD between ethnic groups that differ in the frequency of the c2 allele, we studied 30 Han Chinese with severe alcoholic liver disease. Allele frequencies of alcoholics with cirrhosis were compared with 46 alcoholic and 100 nonalcoholic Han individuals without liver disease. To identify the type A (homozygous for c1), type B (heterozygous for c1 and c2) and type C (homozygous for c2) genotypes, DNA encompassing the polymorphisms was amplified by polymerase chain reaction, slot-blotted, and probed with allele-specific oligonucleotides, No significant differences in c2 allele frequencies were found: 0.23 for alcoholics with severe liver disease, 0.20 for alcoholics without liver disease, and 0.26 for the normal population. There also was no difference in c2 allele frequencies between alcoholic and nonalcoholic Atayal natives from Taiwan. Therefore, our results suggest that the allelic variations at the CYP2E1 gene locus also do not significantly affect the development of alcoholism or ALD in Han Chinese and Atayal natives of Taiwan.
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PMID:Cytochrome P4502E1 genotypes, alcoholism, and alcoholic cirrhosis in Han Chinese and Atayal Natives of Taiwan. 865 60

Acetaldehyde, the first product of ethanol in hepatocytes, can react with protein to form acetaldehyde-protein adducts (APAs). Because it has been suggested that these adducts could be involved in the pathogenesis of ethanol-induced hepatic lesions and in fibrogenesis, we performed an ultrastructural immunohistochemical study to precisely define the cellular and subcellular localization of APAs. A preembedding technique of indirect immunoperoxidase was performed in liver biopsy specimens from eight patients with alcoholic liver disease, using a specific antiserum against APAs. In all specimens, APAs were detected in the rough endoplasmic reticulum, in some peroxisomes, and in the cytosol of hepatocytes. In four patients with steatofibrosis or cirrhosis, labeling of Ito cells was also observed. In these cases, the same staining pattern was observed in the cytoplasmic processes of myofibroblasts in areas of fibrogenesis. When isolated rat Ito cells were incubated in the presence of acetaldehyde, APAs were also detected in the cytoplasm. These results show that APA formation occurs in hepatocytes at the sites of acetaldehyde production. Detection of APAs in human and rat Ito cells strongly suggests that acetaldehyde can diffuse into Ito cells and bind to cytoplasmic proteins to form local APAs. Because Ito cells are the main effector cells of liver fibrosis, detection of APAs in these cells points to their possible involvement in liver fibrogenesis.
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PMID:Cellular and subcellular localization of acetaldehyde-protein adducts in liver biopsies from alcoholic patients. 877 71

Excessive ethanol consumption has been related with the development of liver cirrhosis, as well as with rapid intestinal transit time and diarrhea. Moreover, heavy drinking is associated with an increased incidence of cancer of the oropharynx, larynx, esophagus, and colorectum. Acetaldehyde of microbial origin has recently been suggested as a possible pathogenic factor behind this alcohol-associated gastrointestinal morbidity. The present in vitro study was aimed to investigate alcohol dehydrogenase activity and acetaldehyde formation capacity of some major aerobic bacteria representing the normal colonic flora in man. Cytosolic alcohol dehydrogenase activity and cytosolic protein concentration were determined spectrophotometrically. Alcohol dehydrogenase activity was then calculated as nmoles of reduced substrate produced by milligrams of protein per minute. The ability of different bacteria to produce acetaldehyde was determined by incubating the intact bacterial suspension in closed vials containing ethanol (final concentration 22 mM) for 1 hr at 37 degrees C. The acetaldehyde formed during the incubation was analyzed by headspace gas chromatography. Marked differences in the alcohol dehydrogenase activity and acetaldehyde forming capacity were found among the strains tested. The alcohol dehydrogenase activity varied from 606 +/- 91 nmol/min/mg protein (Escherichia coli IH 50546) to 1 +/- 0.2 nmol/min/mg protein (E. coli IH 50817), and acetaldehyde formation varied from 1,717 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Klebsiella oxytoca IH 35403) to 5 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Pseudomonas aeruginosa ATCC 27853). There was a statistically significant correlation (r = 0.77; p < 0.001) between alcohol dehydrogenase activity and acetaldehyde production from ethanol, strongly suggesting the catalytic role of bacterial alcohol dehydrogenase in this reaction.
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PMID:In vitro alcohol dehydrogenase-mediated acetaldehyde production by aerobic bacteria representing the normal colonic flora in man. 889 13

The main pathway for the hepatic oxidation of ethanol to acetaldehyde proceeds via ADH and is associated with the reduction of NAD to NADH; the latter produces a striking redox change with various associated metabolic disorders. NADH also inhibits xanthine dehydrogenase activity, resulting in a shift of purine oxidation to xanthine oxidase, thereby promoting the generation of oxygen-free radical species. NADH also supports microsomal oxidations, including that of ethanol, in part via transhydrogenation to NADPH. In addition to the classic alcohol dehydrogenase pathway, ethanol can also be reduced by an accessory but inducible microsomal ethanoloxidizing system. This induction is associated with proliferation of the endoplasmic reticulum, both in experimental animals and in humans, and is accompanied by increased oxidation of NADPH with resulting H2O2 generation. There is also a concomitant 4- to 10-fold induction of cytochrome P4502E1 (2E1) both in rats and in humans, with hepatic perivenular preponderance. This 2E1 induction contributes to the well-known lipid peroxidation associated with alcoholic liver injury, as demonstrated by increased rates of superoxide radical production and lipid peroxidation correlating with the amount of 2E1 in liver microsomal preparations and the inhibition of lipid peroxidation in liver microsomes by antibodies against 2E1 in control and ethanol-fed rats. Indeed, 2E1 is rather "leaky" and its operation results in a significant release of free radicals. In addition, induction of this microsomal system results in enhanced acetaldehyde production, which in turn impairs defense systems against oxidative stress. For instance, it decreases GSH by various mechanisms, including binding to cysteine or by provoking its leakage out of the mitochondria and of the cell. Hepatic GSH depletion after chronic alcohol consumption was shown both in experimental animals and in humans. Alcohol-induced increased GSH turnover was demonstrated indirectly by a rise in alpha-amino-n-butyric acid in rats and baboons and in volunteers given alcohol. The ultimate precursor of cysteine (one of the three amino acids of GSH) is methionine. Methionine, however, must be first activated to S-adenosylmethionine by an enzyme which is depressed by alcoholic liver disease. This block can be bypassed by SAMe administration which restores hepatic SAMe levels and attenuates parameters of ethanol-induced liver injury significantly such as the increase in circulating transaminases, mitochondrial lesions, and leakage of mitochondrial enzymes (e.g., glutamic dehydrogenase) into the bloodstream. SAMe also contributes to the methylation of phosphatidylethanolamine to phosphatidylcholine. The methyltransferase involved is strikingly depressed by alcohol consumption, but this can be corrected, and hepatic phosphatidylcholine levels restored, by the administration of a mixture of polyunsaturated phospholipids (polyenylphosphatidylcholine). In addition, PPC provided total protection against alcohol-induced septal fibrosis and cirrhosis in the baboon and it abolished an associated twofold rise in hepatic F2-isoprostanes, a product of lipid peroxidation. A similar effect was observed in rats given CCl4. Thus, PPC prevented CCl4- and alcohol-induced lipid peroxidation in rats and baboons, respectively, while it attenuated the associated liver injury. Similar studies are ongoing in humans.
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PMID:Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases. 889 26

Alcohol affects the liver through metabolic disturbances associated with its oxidation. Redox changes produced by the hepatic alcohol dehydrogenase pathway affect lipid, carbohydrate and protein metabolism. Ethanol is also oxidized in liver microsomes by the ethanol-inducible cytochrome P4502E1, resulting in ethanol tolerance and selective hepatic perivenular damage. Furthermore, P4502E1 activates various xenobiotics, explaining the increased susceptibility of the heavy drinker to the toxicity of anesthetics, commonly used medications (i.e. isoniazid), analgesics (i.e. acetaminophen), and chemical carcinogens. Induction of microsomal enzymes also contributes to vitamin A depletion, enhances its hepatotoxicity and results in increased acetaldehyde generation from ethanol, with formation of protein adducts, glutathione depletion, free-radical-mediated toxicity, and lipid peroxidation. Chronic ethanol consumption strikingly enhances the number of hepatic collagen-producing activated lipocytes. Both in vivo (in our baboon model of alcoholic cirrhosis) and in vitro (in cultured myofibroblasts and activated lipocytes) ethanol and/or its metabolite acetaldehyde increase collagen accumulation and mRNA for collagen. Gender differences are related, in part, to lower gastric ADH activity (with consequent reduction of first pass ethanol metabolism) in young women, decreased hepatic fatty acid binding protein and increased free-fatty acid levels as well as lesser omega-hydroxylation, all of which result in increased vulnerability to ethanol. Elucidation of the biochemical effects of ethanol are now resulting in improved therapy: in baboons, S-adenosyl-L-methionine attenuates the ethanol-induced glutathione depletion and associated mitochondrial lesions, and polyenylphosphatidylcholine opposes the ethanol-induced hepatic phospholipid depletion, the decrease in phosphatidylethanolamine methyltransferase activity and the activation of hepatic lipocytes, with full prevention of ethanol-induced septal fibrosis and cirrhosis; its dilinoleoyl species also increases collagenase activity in lipocytes. The efficacy of this compound in man is now being studied in randomized multicenter clinical trials.
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PMID:Susceptibility to alcohol-related liver injury. 897 51

Ethanol-inducible cytochrome P4502E1 is the main pathway in the non-alcohol dehydrogenase oxidation of ethanol. Its coding gene, CYP2E1, is polymorphic at the Rsa I restriction site in the 5'-flanking region. The mutant genotype c2c2 has a higher transcriptional activity than the genotype c1c1 or c1c2. Heavy drinkers carrying the c2 allele might be at a higher risk of alcoholic cirrhosis since they might synthesize greater amounts of acetaldehyde, the compound believed responsible for hepatotoxicity of ethanol. With the aim of establishing if the c2 allele increases the risk of cirrhosis in heavy drinkers, we studied 58 (6 female) chronic heavy drinkers with liver cirrhosis and 137 healthy normal controls of the same ethnic (white Spaniards) origin. After extraction of DNA from white blood cells, alleles c1 and c2 of CYP2E1 were identified by restriction fragment length polymorphism (RFLP) with endonuclease Rsa I. Fifty-six patients and 130 controls were classified as homozygous c1c1 and two and seven, respectively, as heterozygous c1c2. No homozygous c2c2 were detected. The c2 allele frequencies were 0.017 in patients and 0.026 in controls (non-significant differences). We conclude that the Rsa I RFLP polymorphism is probably not related to the risk of cirrhosis in Spanish heavy drinkers.
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PMID:Rsa I polymorphism at the cytochrome P4502E1 locus is not related to the risk of alcohol-related severe liver disease. 902 17

Alcohol-induced tissue damage results from associated nutritional deficiencies as well as some direct toxic effects, which have now been linked to the metabolism of ethanol. The main pathway involves liver alcohol dehydrogenase which catalyzes the oxidation of ethanol to acetaldehyde, with a shift to a more reduced state, and results in metabolic disturbances, such as hyperlactacidemia, acidosis, hyperglycemia, hyperuricemia and fatty liver. More severe toxic manifestations are produced by an accessory pathway, the microsomal ethanol oxidizing system involving an ethanol-inducible cytochrome P450 (2E1). After chronic ethanol consumption, there is a 4- to 10-fold induction of 2E1, associated not only with increased acetaldehyde generation but also with production of oxygen radicals that promote lipid peroxidation. Most importantly, 2E1 activates many xenobiotics to toxic metabolites. These include solvents commonly used in industry, anaesthetic agents, medications such as isoniazid, over the counter analgesics (acetaminophen), illicit drugs (cocaine), chemical carcinogens, and even vitamin A and its precursor beta-carotene. Furthermore, enhanced microsomal degradation of retinoids (together with increased hepatic mobilization) promotes their depletion and associated pathology. Induction of 2E1 also yields increased acetaldehyde generation, with formation of protein adducts, resulting in antibody production, enzyme inactivation, decreased DNA repair, impaired utilization of oxygen, glutathione depletion, free radical-mediated toxicity, lipid peroxidation, and increased collagen synthesis. New therapies include adenosyl-L-methionine which, in baboons, replenishes glutathione, and attenuates mitochondrial lesions. In addition, polyenylphosphatidylcholine (PPC) fully prevents ethanol-induced septal fibrosis and cirrhosis, opposes ethanol-induced hepatic phospholipid depletion, decreased phosphatidylethanolamine methyltransferase activity and activation of hepatic lipocytes, whereas its dilinoleoyl species increases collagenase activity. Current clinical trials with PPC are targeted on susceptible populations, namely heavy drinkers at precirrhotic stages.
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PMID:Ethanol metabolism, cirrhosis and alcoholism. 902 26

Thus far, a large number of hypothesis have been proposed to explain how ethanol causes liver diseases including fatty liver, hepatitis, hepatic fibrosis, cirrhosis, as well as hepatocellular carcinoma. Although it still remains obscure, recent progress of science enables us to understand the mechanisms more deeply. We reviewed the latest aspects of mechanisms of alcoholic liver diseases, including alteration of redox state, effects of acetaldehyde and acetate, changes of metabolisms of lipid and protein, production of free radicals, alteration of hepatic micro circulation, change of hepatic membrane composition followed by changes of intracellular signal transduction, and effects of endotoxin. Moreover, we discussed the recent progress of studies on enzyme systems which participate in ethanol metabolism.
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PMID:[Recent progression in research on alcoholic liver disease]. 904 44


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