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

The activity of procollagen prolyl hydroxylase was measured in fibrotic liver obtained from mice with hepatosplenic schistosomiasis, an animal model of the most prevalent form of human liver fibrosis. Measurable activity of prolyl hydroxylase in fibrotic liver supernatants was 47-fold higher than that of normal liver. The effect of prolyl hydroxylase inhibition on collagen synthesis in fibrotic liver slices was studied, using 8,9-dihydroxy-7-methyl benzo[b]quinolizinium bromide (GPA 1734). This compound was shown in other systems to inhibit prolyl and lysyl hydroxylations by iron chelation at concentrations which did not affect total protein synthesis. The formation of nondialyzable labelled hydroxyproline was inhibited by GPA 1734, 40, 70 and 95% at 30, 50 and 100 micrometer, respectively. Incorporation of proline into total liver protein was unaffected at 30 and 50 micrometer, but was inhibited 20% at 100 micrometer GPA 1734. Underhydroxylated collagen synthesized by liver slices with GPA 1734 was extracted with neutral salt solution and was subsequently hydroxylated with partially-purified prolyl hydroxylase to the same extent as control material synthesized in the absence of GPA 1734.
 ...
PMID:Liver collagen hydroxylation in murine schistosomiasis. 20 35

Hepatic fibrosis may result from collapse after hepatocellular necrosis or from new formation of connective tissue. Fibroplasia, particularly within the lobular parenchyma, is a dynamic process. Newer cellular and biochemical investigations clarified its various steps. The process begins with stimulation of cells to connective tissue formation and can be divided into (1) intracellular synthesis, (2) extracellular maturation, and (3) collagen breakdown. The turnover of the connective tissue in the liver is conspicuously increased in chronic hepatitis of any type, as indicated by an elevation of several cellular and metabolic parameters. They are particularly raised in chronic hepatitis and in alcoholic liver injury. Further development of these parameters in the future should facilitate the analysis of the dynamics of fibroplasia. The strongest stimuli for hepatic fibroplasia are hepatocellular necrosis and inflammation, but ethyl alcohol and steatosis are also stimulating, though to a lesser degree. This explains the particular elevation of the fibroplastic parameters in alcoholic hepatitis. It points, however, also to the possibility that cirrhosis might develop without significant hepatocellular necrosis and inflammation. Perihepatocellular, periductular, and septal fibrosis are the functionally most important localizations leading to additional hepatic injury. The initiation of these types of fibrosis by liver injury points to a vicious circle. Specific anti-fibroplastic therapy is still in infancy.
 ...
PMID:[Hepatic fibrosis--mechanism, dynamics and clinical consequences (author's transl)]. 20 39

Many chronic inflammations of various origin are characterized by an elevated metabolic activity of connective tissue, causing an increased tissue proliferation. The authors first review the more recent methods of analyzing the connective tissue metabolism. Details of changes of this metabolism are described with reference to liver fibrosis and rheumatoid arthritis. First steps of a pathobiochemical diagnosis of activity in organ fibroses are discussed. It seems possible to judge the activity of liver fibrosis by estimating the serum activity of lysosomal glycosidases and serum levels of terminal collagen peptides. Elevated antiprotease serum levels in rheumatoid patients may indicate an inflammatory activity.
 ...
PMID:[Pathobiochemistry of organ fibroses. Changes in the connective tissue metabolism in liver fibrosis and in chronic polyarthritis]. 22 18

A significant increase in the activity of prolyl hydroxylase, in the relative collagen synthesis and in the hydroxyproline content was observed in the liver of rats treated for five weeks with CCl4 when compared to control liver. Five weeks after the suspension of the treatment, the activity of prolyl hydroxylase and the relative collagen synthesis returned to normal, but the hydroxyproline content of the liver of the CCl4-treated animals remained significantly higher than that of the controls. These findings suggest that an impairment in the mechanisms responsible for the resorption of the scar tissue could account for the accumulation of collagen within the parenchyma in liver fibrosis.
 ...
PMID:Collagen metabolism in the liver of normal and carbon tetrachloride treated rats. 23 Aug 65

Proline analogs are readily incorporated into collagen and noncollagen proteins. Since the imino acid content of collagen is greater than other proteins, it is suggested that the incorporation of a proline analog into cellular protein would have a maximal effect on collagen metabolism. Using a partially purified amino acyl tRNA synthetase preparation, various proline analogs were tested for their ability to inhibit Pro-tRNA synthesis. Amongst those tested, dehydroproline was the preferred inhibitor. Dehydroproline was also a substrate for amino acyl tRNA synthetase. When dehydroproline was added in vitro to membrane bound polysomes, the synthesis of collagenous proteins was preferentially inhibited. The addition of dehydroproline to mammalian cell cultures caused a marked reduction in prolyl hydroxylase activity. Under these conditions growth of cells, activities of lysyl; hydroxylase or lactic dehydrogenase were not affected. Reduction of prolyl hydroxylase activity by dehydroproline required protein synthesis. Removal of dehydroproline from the growth medium resulted in an increase in prolylhydroxylase activity. Hepatic fibrosis can be induced in rats by chronic administration of carbon tetrachloride. Under these conditions, the collagen content and prolyl hydroxylase activity of the liver is enhanced. Treatment of these fibrotic animals with dehydroproline results in a reduction of prolyl hydroxylase activity of the liver. A mechanism by which dehydroproline reduces prolyl hydroxylase activity will be discussed. Since prolyl hydroxylase plays a key role in the maturation and deposition of collagen, specific inhibitors of this enzyme are potentially useful in controlling collagen deposition in various pathological conditions.
 ...
PMID:Regulation of collagen synthesis and maturation by 3,4-dehydroproline. 23 92

Collagen synthesis was measured in liver slices obtained from mice with hepatosplenic schistosomiasis. Enlarged fibrotic livers from these mice contained 20 times more collagen than normal. This model of hepatic fibrosis results from an inflammatory granulomatous host response to Schistosoma mansoni ova in portal tracts, rather than from direct lover cell injury as with carbon tetrachloride-induced liver fibrosis. Collagen synthesis, as measured by the formation of labeled protein-bound hydroxyproline, occurred in granulomas isolated from fibrotic livers. Labeled collagen that cochromatographed with type I collagen was extracted with neutral salt solution from liver slices incubated with labeled proline. The free proline pool of the liver was doubled in infected mice; coordinately, liver slices from these animals showed maximal collagen production when the concentration of free proline in the medium was raised to 0.4 mM, the same level measured in the fibrotic livers. Under such conditions, collagen synthesis was at a rate equivalent to the formation of 5.4 nmol of protein-bound hydroxyproline per g liver in 6 h. In comparative incubations in medium containing 0.2 mM proline, fibrotic liver slices produced 16-fold more collagen than normal slices. The proline analogue, L-azetidine 2-carboxylic acid, effectively inhibited synthesis of labeled collagen by fibrotic liver slices. These studies show the synthesis of collagen in a reproducible animal model of the most prevalent form of human liver fibrosis. Difinitition of the controlling factors in this system is of interest for the general problem of fibrosis produced by immunological responses.
 ...
PMID:Liver collagen synthesis in murine schistosomiasis. 84 55

In the previous experiments, it was demonstrated that high purity elastase extracted from porcine pancreas remarkably inhibits liver fibrosis of rats having chronic liver injury caused by carbon tetrachloride. This time, with the purpose to clarify the mechanism of inhibition of liver fibrosis by elastase, comparative study was made on the activity of lysosomal enzymes by measuring beta-glucuronidase, cathepsin and collagenolytic activity, with the rats administered with elastase and with those untreated, during the period of development of liver fibrosis and the recovery from it. In addition to it, in vitro experiments were made by having elastase act on the substrate comprising mixed collagen of acid soluble and neutral soluble collagens extracted from the skin of guinea pigs and by observing collagen components by disc electrophoresis. With any lysosomal enzymes, no marked difference was noticed between elastase group and non-administered group and thus the possibility of inhibition of liver fibrosis through activation of lysosomal enzyme by elastase was denied. The results of disc electrophoretic observation of the performance of elastase on collagen revealed that beta-component of collagen is disappeared but alpha-component remained. From the above, inhibition of liver fibrosis by elastase may be due to direct affection of elastase to telopeptide portion of collagen.
 ...
PMID:Studies on the inhibition of experimental liver fibrosis. 2. The mechanism of the inhibition of liver fibrosis of rats due to carbon tetrachloride by elastase. 123 99

Many tests for hepatitis C virus (HCV) infection have been developed and have proved useful for prevention of post-blood transfusion hepatitis C. However, there are at least 4 genotypes of HCV and the predominant type is different among countries. None of the tests using antigens from one genotype are sensitive in detecting the antibodies against another genotype. More sensitive tests using a more stable part of the HCV RNA sequences such as 5'-noncoding region must be developed for clinical use. Automated PCR methods and DNA sandwich hybridization methods using branched DNA amplification multimers may be candidates. Recently a hepatocyte growth factor test has been developed in Japan. Multicenter trials of this test reveal that it is useful for assessment of acute severe hepatitis. Tests for collagen type IV, fibronectin receptor, and prolyl hydroxylase have been reported useful for assessment of liver fibrosis. However, serum prolyl hydroxylase is prone to increase in response to hepatocellular damage as well as fibrotic processes. Enzymatic methods for determination of branched amino acids and tyrosine have been developed. The molar ratio of branched amino acids to tyrosine seems to have same pathophysiological meaning as the ratio of branched amino acids to aromatic amino acids (Fischer ratio) in assessment of liver cirrhosis. Lidocaine test is reported to be useful for predicting survival of transplanted liver and also assessing the function of the cirrhotic liver. Profiles of alpha-fetoprotein subfractions based on lectin-reactivity and galactosyl transferase II isoenzyme have been reported to be useful for detecting hepatocellular carcinoma but this remains to be proved.
 ...
PMID:[Recent advances in laboratory tests for liver diseases]. 130 30

Liver samples from patients with three different types of liver diseases, alveolar echinococcosis (a dense and irreversible fibrosis), hepatocellular carcinoma and alcoholic cirrhosis, were analyzed for their content in hydroxypyridinium cross-links found in mature collagen. We demonstrated the presence of small amounts of pyridinoline in control livers (0.27 +/- 0.06 pmol/pmol of collagen). Pyridinoline content was increased in fibrotic livers, with the highest values found in patients with alveolar echinococcosis (up to 1.33 pmol/pmol of collagen). The deoxy analogue of pyridinoline was not detected in either normal or fibrotic livers. Pyridinoline levels, expressed as picomoles per picomole of collagen, were similar in all patients with carcinoma (0.7 +/- 0.05 pmol/pmol of collagen). They were heterogeneous in patients with alveolar echinococcosis and were particularly high in patients with alcoholic cirrhosis (1.04 +/- 0.11 pmol/pmol of collagen). These results demonstrate for the first time the presence of an hydroxypyridinium cross-link in liver fibrosis and suggest that pyridinoline measurement might be an important criterion in assessing the irreversibility of human liver fibrosis.
 ...
PMID:Hydroxypyridinium collagen cross-links in human liver fibrosis: study of alveolar echinococcosis. 131 84

Therapy of chronic active liver diseases associated with fibrotic transformation is usually restricted to unspecific antiinflammatory and immunosuppressive agents. However, recent advances in the biochemistry of collagen have allowed to define specific levels of collagen metabolism at which pharmacologic intervention can lead to reduced collagen deposition. The mode of action of some substances which interfere with collagen biosynthesis and degradation is described. However, the efficacy of these agents was tested in vitro exclusively or in animal experiments. Only few agents like colchicine were also studied in clinical trials. Reliable, safe, and specific antifibrotic agents for the clinical management of liver fibrosis do not exist up to now. Advances can be expected, however, from the development of novel inhibitors of prolyl-4-hydroxylase.
 ...
PMID:[What is reliable in therapy of liver fibrosis?]. 132 34


1 2 3 4 5 6 7 8 9 10 Next >>