Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019158 (hepatitis)
 30,205 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytochrome P450 IID6 is an autoantigen recognized by the sera of children affected with a subtype of autoimmune hepatitis. It was hypothesized that a mutation in the CYP2D6 gene could explain the autoimmune response in these patients. To examine this question, genomic DNA from peripheral lymphocytes (n = 9) and liver (n = 1) of 10 patients with anti-LKM-1 antibody was analysed by Southern blot for genetic association studies between a particular CYP2D6 haplotype and autoimmune hepatitis. In addition, a region of CYP2D6, from the same genomic DNA, was amplified by polymerase chain reaction (PCR) and digested by BstNI, in a search for the most prevalent 29B mutation, described in subjects who do not express the P450 IID6. Total RNA and proteins, prepared from the liver of an anti-LKM-1+ patient, were analysed by Northern and Western (immunoblot) blots respectively. Our results do not reveal any major structural change in the DNA of this patient at the CYP2D6 locus that could explain their autoimmune response. Corroborating this observation, no changes were noted either in P450 IID6 mRNA size or in the corresponding protein. However, these data do not exclude the possibility of subtle changes in the protein due to point mutations in critical regions that might trigger an autoimmune response.
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PMID:Study of CYP2D6 gene in children with autoimmune hepatitis and P450 IID6 autoantibodies. 134 12

Liver/kidney microsomal antibody type 1 (LKM-1), the serological marker of a subset of autoimmune hepatitis, is also present in a proportion of patients with hepatitis C virus (HCV) related chronic liver disease. To characterise further this autoreactivity and to evaluate whether an autoantibody giving an identical immunofluorescence staining, and detected in two different clinical conditions, involves the same antigenic target(s), sera from autoimmune and HCV infected patients were tested with native, recombinant, and synthetic antigens. Sixty five sera were selected on the basis of the typical immunofluorescence pattern: 50 patients had serological markers of HCV infection, the remaining 15 suffered from autoimmune hepatitis. The reactivity of each serum with rat and human microsomal fractions, full length human recombinant CYP2D6, and two synthetic peptides spanning the amino acid regions 257-269 and 373-398 of CYP2D6 was systematically investigated by immunoblotting. Fourteen (93%) sera from autoimmune hepatitis patients and 39 (78%) from HCV infected patients reacted with rat and/or human microsomal polypeptides of 39 kD, 50 kD, 58 kD, and 66 kD in different associations, the 50 kD band being the most frequently observed. Reactivity to CYP2D6 and its amino acid sequence 257-269 was significantly more common in autoimmune hepatitis than in HCV infected patients (p < 0.001 and p < 0.0003, respectively). LKM-1 reactivity is directed against heterogeneous and not entirely defined autoantigens. The main target in autoimmune sera is CYP2D6 and its 257-269 amino acid region, while sera from patients with HCV infection are more likely to recognise other microsomal targets, the molecular identity of which is currently unknown.
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PMID:Heterogeneity of liver/kidney microsomal antibody type 1 in autoimmune hepatitis and hepatitis C virus related liver disease. 759 Apr 39

LKM1 autoantibody, directed against P450IID6, is accepted as a marker of a particular type of autoimmune hepatitis, but its role in the pathogenesis of the disease is controversial. Localization of P450IID6 on the cell surface of rat hepatocytes was previously reported, suggesting that membrane-bound P450IID6 could be the target of LKM1 antibodies, thus allowing immune lysis of hepatocytes. The objective of the present study was to determine, using various methods, the cell localization of P450IID6 in human and rat hepatocytes. Incubation of rat and human hepatocytes with LKM1-positive serum showed slight, if any, cell membrane staining using immunofluorescence, immunoperoxidase and immunoelectron microscopic studies. No staining of the plasma membrane of human hepatocytes was observed when incubations were carried out with immunoaffinity-purified antibody directed against peptide 254-271, the main epitope of P450IID6 recognized by all LKM1 sera tested. Chinese hamster ovary cells, transfected with the complete P450IID6 cDNA and incubated with the supernatant from a B cell lymphoblastoid cell line prepared with the lymphocytes of a LKM1-positive patient, did not show any staining of the cell surface by immunofluorescence. Incubation of rat microsomal fraction vesicles with LKM1-positive serum, followed by protein A-gold immunoelectron microscopy, displayed a staining of almost all vesicles, confirming that P450IID6 is present on the cytoplasmic side of the microsomal membrane, which makes it unable to be expressed on the cell surface even if it were transported from the endoplasmic reticulum (ER). Sulpho NHS Biotin labelling of rat hepatocyte cell membranes did not show the presence of a 50-kD molecule that could have reacted with LKM1 antibody. DNA sequencing of exon 1 of the CYP2D6 gene of a patient positive for LKM1 antibody did not show any difference from that of the normal published sequence of the gene. This does not favour an alteration of the NH2 terminal sequence of the P450IID6 molecule that could explain a translocation of the molecule to the luminal side of the ER, allowing its expression on the cell surface. These results indicate that, in all likelihood, P450IID6 molecule is not present on the cell surface of normal rat and human hepatocytes. Other mechanisms than antibody-mediated cell lysis directed against membrane P450IID6 antigenic determinants must be found to account for the destruction of hepatocytes observed in this disease.
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PMID:Cytochrome P450IID6 recognized by LKM1 antibody is not exposed on the surface of hepatocytes. 839 Mar 32

Tienilic acid-induced hepatitis is characterized by the presence of anti-liver and -kidney microsomal (anti-LKM2) autoantibodies in patient sera. Cytochrome P4502C9(CYP2C9), involved in the metabolism of tienilic acid, was shown to be a target for tienilic acid-reactive metabolites and for autoantibodies. To further investigate the relationship between drug metabolism and the pathogenesis of this drug-induced autoimmune disease, the specificity of anti-LKM2 autoantibodies toward CYP2C9 was first determined, and the antigenic sites on CYP2C9 were localized. By constructing several deletion mutants derived from CYP2C9 cDNA and by probing the corresponding proteins with different anti-LKM2 sera, we defined three regions (amino acids 314-322, 345-356, and 439-455); they interacted to form a major conformational autoantibody binding site. This binding site was immunoreactive with 100% of sera and allowed removal of the entire reactivity of the sera tested by immunoblotting. Epitope mapping studies have been performed for CYP2D6, CYP17, CYP21A2, and, recently, CYP3A. Those data were compared with the results obtained in the current study with CYP2C9 in an attempt to elucidate one of the mechanisms by which CYP becomes immunogenic.
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PMID:Tienilic acid-induced autoimmune hepatitis: anti-liver and-kidney microsomal type 2 autoantibodies recognize a three-site conformational epitope on cytochrome P4502C9. 870 Jan 40

Antibodies specific for cytochrome CYP2D6, formally known as liver-kidney-microsome type-1 antibodies (LKM-1), are characteristically found in a subgroup of patients presenting autoimmune hepatitis. They are also found in some patients with chronic HCV infection. These autoantibodies are usually detected by indirect immunofluorescence, immunoblotting and ELISA tests. In an attempt to set up a more sensitive detection assay we developed a quantitative immunoprecipitation radioligand assay using a 35S-methionine-labelled CYP2D6 antigen obtained by in vitro transcription and translation synthesis. All 16 sera from AIH-2 patients strongly bound to this CYP2D6 antigen. Two of the nine sera (22%) from AIH-2 patients that presented only liver cytosol-1 antibodies also bound to CYP2D6. All 24 sera from HCV patients that were positive for LKM-1 antibodies by indirect immunofluorescence were also positive using this CYP2D6 radioligand assay. Lastly, all 15 sera from HCV patients negative for LKM-1 antibodies were negative by this test. The present results support the view that this quantitative radioligand assay is more sensitive than immunoblotting and ELISA CYP2D6 assays, and that it could be used in combination with indirect immunofluorescence assay.
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PMID:A new approach to cytochrome CYP2D6 antibody detection in autoimmune hepatitis type-2 (AIH-2) and chronic hepatitis C virus (HCV) infection: a sensitive and quantitative radioligand assay. 918 82

Dihydralazine-induced hepatitis is characterized by the presence of anti-liver microsomal (anti-LM) autoantibodies in the sera of patients. Cytochrome P450 1A2 (CYP1A2), involved in the metabolism of dihydralazine, was shown to be a target for autoantibodies. In order to investigate further the relationship between drug metabolism and the pathogenesis of this drug-induced autoimmune disease, and since the specificity of anti-LM autoantibodies towards CYP1A2 has been determined, the antigenic site was further localized. By constructing fragments derived from CYP1A2 cDNA and probing the corresponding proteins with several anti-LM sera, we were able to define a region (amino acid 335-471) which was immunoreactive with 100% of sera. An internal deletion in this region led to the loss of recognition by anti-LM autoantibodies, confirming that the epitope was conformational. Epitope mapping studies had previously been performed for CYP2D6, CYP17, CYP21A2, and recently for CYP3A1 and CYP2C9. Those data were compared with results obtained in the present study for CYP1A2.
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PMID:Epitope mapping of human CYP1A2 in dihydralazine-induced autoimmune hepatitis. 924 57

Anti-liver-kidney microsome-1 (LKM-1), which reacts with cytochrome P450 IID6 (CYP2D6), is an autoantibody present in autoimmune hepatitis type II, which affects primarily young patients. Recently, it has been shown some adult patients with chronic hepatitis C are also positive for anti-LKM-1. Thus, anti-LKM-1-positive patients can be classified into two subgroups: (1) those with autoimmune hepatitis type II and (2) those with chronic hepatitis C. We investigated the antigenic epitopes of CYP2D6 with which each of these two anti-LKM-1-positive subgroups reacted. Multiple deletion mutants of CYP2D6 were constructed from a human liver cDNA library and five recombinant fusion proteins expressed. Antigenic epitopes were determined by immunoblot analysis using these proteins. Anti-LKM-1 present in HCV-negative sera recognized at least two peptide regions of aa213-280 and aa341-477 of human CYP2D6. In contrast, anti-LKM-1 present in HCV-positive sera recognized only a single region of aa341-477. Thus, the sera of patients with autoimmune hepatitis type II and patients with chronic hepatitis C recognize different antigenic epitopes of the CYP2D6 molecule. To our knowledge, this is the first time LKM-1 autoantigens have been analyzed at the molecular level in Japanese patients.
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PMID:Differences in antigenic sites, recognized by anti-liver-kidney microsome-1 (LKM-1) autoantibody, between HCV-positive and HCV-negative sera in Japanese patients. 971 54

Halothane, an effective and usually safe anaesthetic agent, is rarely associated with the development of fulminant hepatic failure. Guidelines have been developed to reduce the probability of a patient developing halothane hepatitis. However, cases continue to occur and, in some cases, the guidelines have been ignored. Stricter adherence to the guidelines will reduce, but not totally prevent, further cases from occurring. Once halothane hepatitis has developed, there are no specific treatments and liver replacement may be required. Halothane hepatitis is a paradigm for immune mediated adverse drug reactions. The mechanism appears to be related to development of sensitization to both autoantigens (including CYP2D6) and halothane-altered liver cell determinants.
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PMID:Halothane hepatitis. 974 90

Anti-liver kidney microsome-1 (LKM-1) autoantibody, which is a serological marker for autoimmune hepatitis type II, recognizes Cytochrome P450 IID6 (CYP2D6). This autoantibody is also detected in a portion of patients with chronic hepatitis C. Anti-LKM-1 has been measured by indirect immunofluorescence (IF) using rat liver and kidney sections. However, this method has some problems in specificity and is so laborious to handle with many samples. In this study, in order to determine anti-LKM-1, we established an enzyme-linked immunosorbent assay (ELISA) for anti-CYP2D6 using a recombinant CYP2D6 fusion protein. We studied sera from 29 patients positive for anti-LKM-1 by the new ELISA. We further studied sera from a total of 301 patients with various liver diseases and 100 sera from normal controls negative for anti-LKM-1 by the new ELISA. The specificity of the ELISA was ascertained by absorption tests using sera positive for anti-LKM-1. In 29 sera from patients positive for anti-LKM-1 by IF, we found a good correlation between the logarithms of the antibody titers determined by IF and ELISA indexes obtained by our new method. Anti-CYP2D6 was positive in 12 of 12 (100%) patient with autoimmune hepatitis type II and 16 of 17(94.1%) with chronic hepatitis C positive for anti-LKM-1 by IF. In other 401 sera negative for anti-LKM-1 by IF, anti-CYP2D6 was all negative except a few sera. We established a new ELISA for anti-LKM-1 (anti-CYP2D6). This ELISA system is sensitive, antigen-specific and easy to be done. Therefore, this assay allows a routine test of many serum samples, especially for diagnosing autoimmune hepatitis type II.
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PMID:Detection of anti-LKM-1(anti-CYP2D6) by an enzyme-linked immunosorbent assay in adult patients with chronic liver diseases. 1043 24

Cytochromes P450 (CYPs) and UDP-glucuronosyltransferases (UGTs) are targets of autoantibodies in several hepatic and extrahepatic autoimmune diseases. Autoantibodies directed against hepatic CYPs and UGTs were first detected by indirect immunofluorescence as antiliver and/or kidney microsomal antibodies. In autoimmune hepatitis (AIH) type 2, liver and/or kidney microsomal (LKM) type 1 autoantibodies are detected and are directed against CYP2D6. About 10% of AIH-2 sera further contain LKM-3 autoantibodies directed against family 1 UGTs. Chronic infections by hepatitis C virus and hepatitis delta virus may induce several autoimmune phenomena, and multiple autoantibodies are detected. Anti-CYP2D6 autoantibodies are detected in up to 4% of patients with chronic hepatitis C, and anti-CYP2A6 autoantibodies are detected in about 2% of these patients. In contrast, 14% of patients with chronic hepatitis delta virus infections generate anti-UGT autoantibodies. In a small minority of patients, certain drugs are known to induce immune-mediated, idiosyncratic drug reactions, also known as 'druginduced hepatitis'. Drug-induced hepatitis is often associated with autoantibodies directed against hepatic CYPs or other hepatic proteins. Typical examples are tienilic acid-induced hepatitis with anti-CYP2C9, dihydralazine hepatitis with anti-CYP1A2, halothane hepatitis with anti-CYP2E1 and anticonvulsant hepatitis with anti-CYP3A. Recent data suggest that alcoholic liver disease may be induced by mechanisms similar to those that are active in drug-induced hepatitis. Autoantibodies directed against several CYPs are further detected in sera from patients with the autoimmune polyglandular syndrome type 1. Patients with autoimmune polyglandular syndrome type 1 with hepatitis often develop anti-CYP1A2; patients with adrenal failure develop anti-CYP21, anti- CYP11A1 or CYP17; and patients with gonadal failure develop anti-CYP11A1 or CYP17. In idiopathic Addison disease, CYP21 is the major autoantigen.
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PMID:Target proteins in human autoimmunity: cytochromes P450 and UDP- glucuronosyltransferases. 1085 Dec 84


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