Diagnostic and therapeutic implications of bile duct injury in autoimmune hepatitis

Intracellular balance of oxidative stress and cytoprotective molecules in damaged interlobular bile ducts in autoimmune hepatitis and primary biliary cirrhosis: In situ detection of 8-hydroxydeoxyguanosine and glutathione-S-transferase-pi

AIM

Bile duct injury has been thought to be absent in autoimmune hepatitis (AIH), but recent studies have indicated that AIH patients do have bile duct injury. In this study, the intracellular balance of oxidative stress and cytoprotection in biliary epithelial cells was investigated to clarify the pathogenesis of bile duct injury in AIH.

METHODS

The intracellular status of oxidative DNA damage caused by oxidative stress and glutathione, an endogenous cytoprotective molecule, were examined in patients with AIH, primary biliary cirrhosis (PBC), and normal controls by immunostaining of 8-hydroxydeoxyguanosine (8-OHdG) and glutathione-S-transferase-pi.

RESULTS

Immunohistochemically, 8-OHdG expression was detected as abundantly in the damaged bile ducts of AIH patients as in PBC patients. Moreover, in AIH, 8-OHdG expression was detected in damaged bile ducts more than in undamaged bile ducts. Glutathione-S-transferase-pi expression was relatively preserved in the damaged bile ducts of AIH patients compared to PBC patients, reflecting preservation of intracellular glutathione.

CONCLUSIONS

In AIH, oxidative stress and DNA damage may be involved in the pathogenesis of bile duct injury in a manner similar to that found in PBC. However, relatively preserved intracellular glutathione may play a key role in preventing progressive bile duct loss following bile duct injury in AIH.

Gene cloning and fusion expression of human autoantigen Sp100 in yeasts

AIM: To clone and construct the plasmid cont-aining human autoantigene Sp100 gene, and then to identify the immunoreactivity of the purified recombinant protein.

METHODS: The Sp100 gene was amplified from human liver cDNA library, and then was cloned into PEGH vector to induce the Sp100 expression. The obtained products were identified and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot.

RESULTS: The sequence of Sp100 autoantigene gene was confirmed to be the same as the sequence reported in GenBank. The fusion pro-teins were found at 53-, 55-, 52-, 37-, 42-, and 47-ku strip on SDS-PAGE gel. Western blot analysis showed that the fusion protein with 55, 52, 42 and 47 ku had the same immunoreactivity as human Sp100 autoantigene.

CONCLUSION: Human plasmid containing Sp100 gene is successfully cloned and expressed in yeast Y258.

Autoimmune hepatitis, from mechanisms to therapy

In 1950, Waldenström was the first to describe a chronic form of hepatitis in young women. Subsequently, the disease was found to be associated with other autoimmune syndromes and was later termed "lupoid hepatitis" because of the presence of antinuclear antibodies. In 1965, it became designated by Mackay et al. as "autoimmune hepatitis" at an international meeting, at which the general concept of autoimmunity was endorsed by the scientific community. In the early 1960s and 1970s, the value of immunosuppressive therapy with glucocorticoids and/or azathioprine was well documented in several studies. The original association of autoimmune hepatitis (AIH) and HLA alleles, which has remarkably stood the test of time, was published in 1972. In the 1970s and 1980s, several autoantibodies were identified in patients with autoimmune hepatitis directed against proteins of the endoplasmatic reticulum expressed in liver and kidney and against soluble liver antigens. Subsequently, the molecular targets of these antibodies were identified and more precisely characterized. In the last two decades many additional pieces of the AIH puzzle have been collected leading to the identification of additional antibodies and genes associated with AIH and to the emergence of new therapeutic agents. Meanwhile, the immunoserological and genetic heterogeneity of AIH is well established and it has become obvious that clinical manifestations, disease behavior, and treatment outcome may vary by racial groups, geographical regions and genetic predisposition. Currently, the International Autoimmune hepatitis group is endorsing multi-center collaborative studies to more precisely define the features at disease presentation and to define prognostic indices and appropriate treatment algorithms. Given the importance of serological testing, the IAHG is also working on guidelines and procedures for more reliable and standardized testing of autoantibodies.

Autoantibodies in autoimmune liver disease

Autoantibodies indicate an immune reactive state, but in liver disease they lack pathogenicity and disease specificity. Antinuclear antibodies, smooth muscle antibodies, antibodies to liver/kidney microsome type 1, antimitochondrial antibodies, and perinuclear antineutrophil cytoplasmic antibodies constitute the standard serological repertoire that should be assessed in all liver diseases of undetermined cause. Antibodies to soluble liver antigen/liver pancreas, asialoglycoprotein receptor, actin, liver cytosol type 1, nuclear antigens specific to primary biliary cirrhosis, and pore complex antigens constitute an investigational repertoire that promises to have prognostic and diagnostic value. These autoantibodies may emerge as predictors of treatment response and outcome. Antibodies to histones, doubled-stranded DNA, chromatin, and lactoferrin constitute a supplemental repertoire, and they support the immune nature of the liver disease. Final diagnoses and treatment strategies do not depend solely on serological markers. Autoantibodies are floating variables, and their behavior does not correlate closely with disease activity. There are no minimum levels of significant seropositivity, especially in children. Over-interpretation is the major pitfall in the clinical application of the serological results. New autoantibodies will emerge as the search for target antigens and key pathogenic pathways continues.

Significance of bile-duct changes in schistosomiasis

Lesions involving the intra-hepatic biliary ducts in schistosomiasis have been reported in the literature, both in mice and man, but there are no data concerning their quantitative, evolutionary or post curative chemotherapeutic aspects on record. In order to obtain such data an investigation on this subject was attempted. Mice infected with 50 Schistosoma mansoni cercariae were submitted to a liver biopsy at the 9th week post-infection, and treated with 400 mg/bw praziquantel immediately afterwards. Infected and non-infected controls were submitted to the same procedures. By 19 weeks from cercarial exposure all surviving animals were sacrificed. The biliary ducts were counted on histological sections and the results were expressed as biliary ducts/portal spaces. This quantitative evaluation was compared with that from normal controls and revealed hyperplasia as the main biliary duct change (p<0.007) in schistosomiasis. Hyperplastic changes underwent only mild partial and not statistically significant regression after specific chemotherapy (p>0.05). Infected and untreated animals presented ductal changes that did not differ from those of the treated group. Measurements of serum bilirubin (total and direct), and gamma-glutamyl-transpeptidase (gamma-GT) did not reveal significant differences when animals from the several groups were compared. Thus, bile ducts exhibit a proliferative response in relation to neighboring S. mansoni injury to portal areas, but although these lesions are histopathologically impressive, they lack a functional or prognostic significance.

Autoimmune hepatitis: effect of symptoms and cirrhosis on natural history and outcome

Although the natural history of autoimmune hepatitis (AIH) has been characterized, little is known about patients who present asymptomatically. Consequently, whether they require immunosuppressive therapy with its associated complications is unclear. To compare the natural history of asymptomatic AIH with symptomatic AIH, a large cohort of patients from a single center was examined. All patients with a clinical diagnosis of AIH were reassessed using the revised criteria of the International Autoimmune Hepatitis Group. Liver histology, response to therapy, and survival were assessed. Patients asymptomatic at presentation (n = 31) had lower serum aminotransferase, bilirubin, and immunoglobulin G (IgG) values at baseline. Half of the asymptomatic patients received no therapy, and their survival was no different from that of the total cohort. Ten-year survival was 80.0% (62.5%-97.5%) in the asymptomatic group and 83.8% (75.1%-92.6%) in the symptomatic patients (P = NS). Survival to liver-related endpoints at 10 years was similar in both groups: 89.5% (75.7%-100%) asymptomatic and 83.8% (75.1%-92.6%) symptomatic patients (P = NS). Patients with cirrhosis at baseline had poorer 10-year survival (61.9% [CI 44.9%-78.9%]) than those without cirrhosis at presentation (94.0% [CI 87.4%-100%]) (P = .003) regardless of whether they presented with symptoms or whether they received immunosuppressive therapy. In conclusion, patients with AIH who are asymptomatic at presentation have a good prognosis and may not require immunosuppressive therapy. Cirrhosis on initial liver biopsy portends a poor prognosis in all patients with AIH.

Autoimmune liver disease

PURPOSE OF REVIEW

This review aims to demonstrate how recent insights into disease behavior and mechanisms and the availability of new drugs can be assimilated into evolving concepts of diagnosis and treatment.

RECENT FINDINGS

Autoimmune hepatitis has a global distribution, and its clinical manifestations are similar in different regions. Concurrent immune diseases are common, and immunoglobulin A nephropathy may explain ascites in some patients. Subclinical celiac disease can cause cryptic liver dysfunction or be associated with autoimmune hepatitis. A fulminant presentation that is associated with de novo rather than exacerbated pre-existent disease is possible, and these patients may have centrilobular zone 3 necrosis. Bile duct injury as a background histologic finding should not change the diagnosis or therapy, and the clinical significance of autoantibodies can be determined only by examination of liver biopsy tissue. Molecular mimicry may be important in breaking self-tolerance, and a murine model based on DNA immunization with self-antigens supports this hypothesis. Corticosteroid therapy reduces or prevents hepatic fibrosis, and noninvasive techniques promise to facilitate the development of treatments that enhance this effect. Mycophenolate mofetil is a possible salvage therapy that requires clinical trial, and liver transplantation has a 5-year patient survival of 78% but is frequently followed by recurrent disease and acute rejection.

SUMMARY

Autoimmune hepatitis should be considered in all patients with acute or chronic liver disease. Therapy can reduce or prevent fibrosis. The new immunosuppressive drugs should undergo clinical trial before empiric use. Animal models promise to identify key pathogenic sites that can be targeted by therapies.