Pathogenesis of primary biliary cirrhosis

Autoimmune hepatitis type 2 associated with an unexpected and transient presence of primary biliary cirrhosis-specific antimitochondrial antibodies: a case study and review of the literature

Background

Unlike other autoimmune liver diseases, primary biliary cirrhosis (PBC) has never been reported in early childhood, while type 2 autoimmune hepatitis (AIH) is eminently a paediatric disease.

Case presentation

We describe a case of type 2 AIH with serological positivity for PBC-specific anti-mitochondrial antibodies (AMA) in a 3-year old girl. We found this observation intriguing as AMA and indeed an overlap with PBC are virtually absent in Type 2 AIH, a pediatric form of AIH which is distinct precisely because it is characterized by pathognomonic anti-liver kidney microsomal type 1 (LKM-1) showing a remarkable antigen-specificity directed against cytochrome P4502D6. We also review the literature in relation to AMA positivity in paediatric age and adolescence. In our case, the presence of AIH-2-specific anti-LKM-1 and PBC-specific AMA was confirmed by indirect immunofluorescence (IIF), and immunoblotting and ELISA based on recombinant mitochondrial antigens. The clinical, laboratory and histological features of the child are given in detail. Interestingly the mother was AMA positive without other features of PBC. The child was successfully treated with immunosuppression and five years after the original diagnosis is on a low dose of prednisolone and azathioprine, with no signs of relapse. Anti-LKM-1 antibodies are still present in low titres. AMA were detectable for the first 4 years after the diagnosis and disappeared later.

Conclusion

This is the first case report in the literature of AIH type 2 with an unexpected PBC-specific AMA positivity in a young child. Response to immunosuppressive treatment was satisfactory and similar to that described in AIH. A review of published reports on AMA positivity in paediatric age shows that the antibody may arise in the context of immunodeficiency and is variably associated with liver damage.

Value of autoantibody analysis in the differential diagnosis of chronic cholestatic liver disease

BACKGROUND & AIMS

It is challenging to diagnose patients with chronic cholestatic liver diseases when all the classic criteria are not fulfilled. We evaluated the performance of the recently developed MIT3-based enzyme-linked immunosorbent assay (ELISA), which detects antimitochondrial autoantibodies (AMAs), together with ELISAs for other autoimmune liver disease-related antibodies in patients with chronic cholestatic liver disease.

METHODS

Sera from 281 patients with chronic cholestatic conditions, including primary biliary cirrhosis (PBC), primary sclerosing cholangitis, AMA-positive autoimmune hepatitis, and "undetermined cholangiopathy" were tested for the following PBC-associated autoantibodies: anti-gp210, anti-sp100, conventional anti-M2, anti-M2 (MIT3) IgG, anti-M2 (MIT3) IgA, as well as anti-centromere, anti-soluble liver antigen, and anti-chromatin.

RESULTS

Of 57 patients with PBC who were AMA-negative by conventional M2 ELISA, 14 were found to be AMA-positive by the MIT3-IgG assay. Furthermore, on the basis of the data from 3 tests (MIT3-IgG, gp210, and sp100), PBC was confirmed in 20 of 57 (35%) patients diagnosed with AMA-negative PBC. We confirmed that sp100 and gp210 antibodies were detected only in patients with PBC and AMA-positive autoimmune hepatitis, whereas gp210 was detected more frequently in patients known to have had a poor outcome. Of the 11 patients with an undetermined cholangiopathy, 3 (27%) tested positive for PBC with the MIT3-IgG assay. In contrast to previous findings, anti-centromere antibodies were not found to be associated with poor outcome in PBC.

CONCLUSIONS

ELISAs for AMAs and antinuclear antibodies are useful in diagnosis and prognosis of patients with features of PBC who lack conventional AMA and in patients with a cholangiopathy of undetermined etiology.

Serum BAFF and APRIL levels in patients with PBC

B-cell-activating factor belonging to the TNF family (BAFF) and a proliferation-inducing ligand (APRIL) are known to be involved in the occurrence of autoimmune diseases. We assessed serum levels of these cytokines in PBC patients. Serum BAFF levels were significantly higher in PBC patients than in healthy controls (1253.9+/-741.4 vs. 722.8+/-199.2 pg/ml; p<0.0001) and HCV-infected patients (1253.9+/-741.4 vs. 871.0+/-251.1 pg/ml; p=0.015). Whereas changes in serum APRIL levels were not significant among these groups, there was a significant correlation between BAFF and AST (R=0.278, p=0.003) or total bilirubin (R=0.363, p=0.0006) in PBC patients. Furthermore, serum BAFF levels were elevated in PBC patients with advanced interface hepatitis. Our data indicate that serum levels of BAFF and APRIL are differentially regulated and serum BAFF levels are significantly elevated in PBC patients. These findings suggest that BAFF may serve as a modulator of the clinical and/or serological manifestation in PBC patients.

Gene expression profiling of early primary biliary cirrhosis: possible insights into the mechanism of action of ursodeoxycholic acid

OBJECTIVES

Primary biliary cirrhosis (PBC) is a poorly understood disease, both in terms of its pathogenesis and the mechanism of action of its most common treatment, ursodeoxycholic acid (UDCA). We used gene expression profiling to compare liver tissue from treatment-naïve and UDCA-treated patients in order to outline some of the molecular changes associated with PBC and its treatment. PATIENTS AND EXPERIMENTAL DESIGN: Liver biopsy specimens from non-cirrhotic, treatment-naïve (n=11) patients were compared with biopsies from UDCA-treated patients (n=20) and with 10 normal, healthy female controls. Gene expression was determined using a 19K cDNA microarray. In order to determine whether the observed changes in gene expression levels were specific to PBC or generic to liver damage overall, PBC samples were also compared with chronically diseased [48 hepatitis C virus (HCV), 18 hepatitis B virus (HBV)] and acutely stressed liver tissue (25 liver biopsies taken after reperfusion of liver transplant grafts).

RESULTS

We found a gene signature specific to PBC (P<or=0.012), containing biologically plausible genes (221 genes with adjusted P</=0.05). Differences in the expression of selected genes were confirmed using real-time polymerase chain reaction. When gene expression from non-cirrhotic UDCA-treated (n=20) and UDCA-naïve liver tissue was compared, we found a striking downregulation of a number of genes involved in protein biosynthetic pathways.

CONCLUSIONS

These studies highlight the genes associated with both treatment-naïve and UDCA-treated PBC, and suggest that the effects of UDCA are mediated, at least in part, via a modulation of protein biosynthesic pathways.

Concept on the pathogenesis and treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease that predominantly affects women and is characterized by chronic, progressive destruction of small intrahepatic bile ducts with portal inflammation and ultimately fibrosis, leading to liver failure in the absence of treatment. Little is known about the etiology of PBC. PBC is characterized by anti-mitochondrial antibodies and destruction of intra-hepatic bile ducts. The serologic hallmark of PBC is the presence of auto-antibodies to mitochondria, especially to the E2 component of the pyruvate dehydrogenase complex (PDC). Current theories on the pathogenesis of PBC favor the hypothesis that the disease develops as a result of an inappropriate immune response following stimulation by an environmental or infectious agent. Some reports suggest that xenobiotics and viral infections may induce PBC. The pathogenetic mechanism is believed to be caused by a defect in immunologic tolerance, resulting in the activation and expansion of self-antigen specific T and B lymphocyte clones and the production of circulating autoantibodies in addition to a myriad of cytokines and other inflammatory mediators. This leads to ductulopenia and persistent cholestasis, by developing end-stage hepatic-cell failure. In this review are given our own and literary data about mechanisms of development of intrahepatic cholestasis and possible ways of its correction.

Estrogens maintain bile duct mass and reduce apoptosis after biliodigestive anastomosis in bile duct ligated rats

BACKGROUND/AIMS

Disapperacence of bile ducts (ductopenia) represents the terminal, common stage of human cholangiopathies, and estrogens exert a major role in stimulating cholangiocyte proliferation. We thus evaluated whether estrogen administration protect from the bile duct loss induced by the biliary-digestive diversion in bile duct ligated (BDL) rats.

METHODS

After 3 weeks of BDL, rats were subjected to biliary-digestive diversion and treated with daily injections of 17beta-estradiol or a control solution.

RESULTS

Both after 7 and 14 days from the biliary-digestive diversion a marked increase of the number of apoptotic cholangiocytes was observed. In contrast, 17beta-estradiol significantly reduced cholangiocyte apoptosis. 17beta-estradiol also prevented the biliary-digestive diversion-induced loss of PCNA-positive cholangiocytes and of the bile duct mass. Biliary-digestive diversion determined a marked reduction of ERK1/2 phopsphorylation in cholangiocytes that was reversed by the administration of 17beta-estradiol.

CONCLUSIONS

This study indicates that estrogens prevent the increase of cholangiocyte apoptosis and loss of cholangiocyte proliferation induced by the biliary-digestive diversion in the BDL rat. In parallel, 17beta-estradiol also enhanced ERK1/2 phosphorylation, which is instead strongly reduced by the biliary-digestive diversion. These novel findings suggest that estrogens could prevent the evolution of cholangiopathies toward ductopenia.