Immunopathogenesis of cholestatic autoimmune liver diseases

Making Sense of Autoantibodies in Cholestatic Liver Diseases

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are the most common chronic cholestatic liver diseases (CLD) in adults and are associated with immune mechanisms. PBC is considered a model autoimmune disease, and more than 90% of patients present very specific autoantibodies against mitochondrial antigens. Whether PSC should be considered an autoimmune or merely immune-mediated disease is still under debate. This review addresses the clinical relevance of autoantibodies in CLD and their pathogenic mechanisms and illustrates the technology available for appropriate autoantibody detection.

Transient elastography to assess hepatic fibrosis in primary biliary cirrhosis

BACKGROUND

Liver stiffness measurements may have potential for detecting and monitoring hepatic fibrosis in chronic liver disease.

AIM

To study the detection, quantification and progression of hepatic fibrosis in primary biliary cirrhosis by liver stiffness measurements.

METHODS

Liver stiffness measurements were generated in 80 patients with primary biliary cirrhosis by applying transient elastography; however, as there were 55 with liver biopsy, histological stage (METAVIR) and liver stiffness measurements were compared only in these 55 patients. The efficiency of liver stiffness measurements in predicting stage of fibrosis was determined from the area under receiver operating characteristics curve analysis.

RESULTS

Of the 80 patients included, 91, 4% were women and their mean age was 56 +/- 12 (s.d.) years. A significant correlation was found (P < 0.05) between histological fibrosis stage (METAVIR) and liver stiffness measurements. The values obtained from area under receiver operating characteristic curve analysis of liver stiffness measurement data were 0.89 for F > 2 and 0.96 for F = 4. Liver stiffness measurements were 9.0 +/- 5.3 and 7.9 +/- 6.0 kPa for patients followed up more than 5 years and less than 5 years, respectively (P > 0.05).

CONCLUSIONS

In patients with primary biliary cirrhosis, median values of liver stiffness measurements correlated with histological severity of hepatic fibrosis. Liver stiffness measurements appear to be promising for liver fibrosis detection and quantification, as well as monitoring its progression, in patients with primary biliary cirrhosis. The progression rate of hepatic fibrosis in our primary biliary cirrhosis patients appears to be slow.

Pathophysiological basis for antioxidant therapy in chronic liver disease

Oxidative stress is a common pathogenetic mechanism contributing to initiation and progression of hepatic damage in a variety of liver disorders. Cell damage occurs when there is an excess of reactive species derived from oxygen and nitrogen, or a defect of antioxidant molecules. Experimental research on the delicately regulated molecular strategies whereby cells control the balance between oxidant and antioxidant molecules has progressed in recent years. On the basis of this evidence, antioxidants represent a logical therapeutic strategy for the treatment of chronic liver disease. Clinical studies with large numbers of patients have not yet been performed. However, results from several pilot trials support this concept and indicate that it may be worth performing multicentre studies, particularly combining antioxidants with anti-inflammatory and/or antiviral therapy. Oxidative stress plays a pathogenetic role in liver diseases such as alcoholic liver disease, chronic viral hepatitis, autoimmune liver diseases and non-alcoholic steatohepatitis. The use of antioxidants (e.g. S-adenosylmethionine [SAMe; ademetionine], tocopherol [vitamin E], polyenylphosphatidylcholine or silymarin) has already shown promising results in some of these pathologies.

The role of Helicobacter spp. in the pathogenesis of primary biliary cirrhosis and primary sclerosing cholangitis

Helicobacter species DNA has been detected in liver tissue of patients affected by primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). To investigate a potential causative relation between Helicobacter species and PBC/PSC, we compared the presence of Helicobacter species-specific DNA in liver tissue of patients with PBC/PSC (n=18/n=13) with those of a control group of patients with various liver diseases with known cause (n=29). A PCR with Helicobacter genus-specific 16S rRNA primers was performed on DNA isolated from paraffin embedded liver tissue. Control patients had hepatitis-B (n=9), alcoholic cirrhosis (n=14), or non-cirrhotic metabolic liver disease (n=6). There was no significant difference between the incidence of Helicobacter spp.-specific DNA in PBC/PSC (9/31; 29%) and the control group (10/29; 34%). Sequence analysis confirmed Helicobacter spp. DNA. Because Helicobacter spp. DNA can be found in approximately one-third of all samples tested, it is unlikely that PSC and PBC are caused by Helicobacter infection.

Immune-mediated liver injury: prognostic value of CD4+, CD8+, and CD68+ in infants with extrahepatic biliary atresia

BACKGROUND

Hepatic fibrosis and cirrhosis develop progressively in extrahepatic biliary atresia (EHBA) despite timely surgical intervention.

PURPOSE

The aim of the study was to define CD4+ helper T lymphocytes, cytotoxic CD8+ T lymphocytes, and CD68+ (macrophages) infiltration of portal tracts and lobules and hepatic fibrosis as possible predictive measures of outcome of infants having EHBA.

METHODS

The outcome of 32 infants with EHBA was correlated to their percutaneous biopsy and postportoenterostomy core liver tissue infiltration by CD4+, CD68+, and CD8+ cells and to the degree of detected fibrosis.

RESULTS

Portoenterostomy cores were heavily infiltrated by CD4+, CD8+, and CD68+, compared with the preoperative liver biopsy (P = .008, .004, and .017, respectively). Infants having favorable outcome had more macrophage infiltration in portoenterostomy core compared with those having an unfavorable outcome (25.66 +/- 29.77 per HPF compared with 11.62 +/- 4.58, P = .000). Mean CD4+/CD8+ ratio was 1.54 +/- 1.37 in those who died within 18 months postoperatively and 0.733 +/- 0.48 in others (P = .021).

CONCLUSION

Immune-mediated destruction of portal tracts is an integral part of pathogenesis of EHBA.

Evidence of angiogenesis in primary biliary cirrhosis: an immunohistochemical descriptive study

BACKGROUND/AIMS

The intrahepatic inflammatory process occurring during primary biliary cirrhosis contributes to bile duct destruction, but the cellular and molecular pathways involved are largely unknown. Furthermore, additional pathogenetic mechanisms may exist. We aimed at evaluating the cellular infiltrate phenotype; the expression of lymphocyte activation, antigen recognition and cell-adhesion molecules; the occurrence of hepatic angiogenesis and the molecules involved.

METHODS

Immunohistochemical investigations were performed in frozen liver biopsy sections from primary biliary cirrhosis patients.

RESULTS

CD8+ and CD69+ T cells were predominant in inflammatory infiltrates around damaged cholangiocytes; beta2-microglobulin conformational epitope and intercellular adhesion molecule-1 expression were enhanced in bile ducts and hepatocytes. Inflamed portal areas showed vascular cell adhesion molecule-1 up-regulation; formation of tubule-like structures (neovessels) by endothelial cells expressing vascular endothelial-cadherin and CD-31; vascular endothelial growth factor expression in surrounding sinusoidal endothelial cells; and enhanced expression of angiopoietins 1 and 2, their receptor Tie-2 and endoglin, suggesting their involvement in new vascular structure formation.

CONCLUSIONS

The inflammatory infiltrate in primary biliary cirrhosis shows an increased reactivity for lymphocyte activation, antigen recognition and cell- and vascular-adhesion molecules. Additionally, intrahepatic angiogenesis occurs, involving vascular endothelial growth factor, angiopoietins 1 and 2, Tie-2 and endoglin in neovessel formation.

Angiogenesis in chronic inflammatory liver disease

Intrahepatic hypoxia may occur during the inflammatory and fibrotic processes that characterize several chronic liver diseases of viral and autoimmune origin. As a consequence, new vascular structures are formed to provide oxygen and nutrients. Angiogenesis involves a tightly regulated network of cellular and molecular mechanisms that result in the formation of functional vessels. Of particular importance are growth factors, molecules involved in matrix remodeling and cell migration, and vessel maturation-related factors. In recent years, a number of studies have examined the expression and function of many pro- and antiangiogenic molecules in the setting of nontumoral chronic liver diseases and liver regeneration. This review examines the potential pathogenetic role of angiogenesis in the context of viral hepatitis, cirrhosis, autoimmune hepatitis, primary biliary cirrhosis, and alcoholic liver disease. The future perspectives for research in this field are outlined.

Characterization of M2 antibodies in asymptomatic Chinese population

AIM: To investigate the presence of M2 antibodies specific for primary biliary cirrhosis (PBC) in asymptomatic Chinese and identify patients with early PBC.

METHODS: Enzyme-linked immunosorbent assay (ELISA) tests for M2 antibodies to recombinant protein were performed in 5011 subjects (age range, 26-85 years; mean age: 45.81 ± 15.02 years) who took an annual physical examination. M2-positive subjects were further analyzed for immunoglobulin (Ig) classes and subclasses of M2 antibodies. Clinical, biochemical and immunological data were obtained for M2-positive subjects. In addition, ultrasonography (US) or endoscopic retrograde cholangio-pancreatography (ERCP) was performed to exclude any disorders other than PBC.

RESULTS: M2 antibodies were detected in 8 (0.16%) of the 5011 subjects studied. Of the 8 subjects, 7 were female and 1 was male (age range: 40-74 years). An unexplained increase of serum alkaline phosphatase (ALP) and gamma glutamyl transpeptidase (γ-GT) values, often to striking levels, was detected in 4 M2-positive subjects, 3 of them accorded with the diagnostic criteria recommended by the American Association for the Study of Liver Diseases, even though they had no symptoms of PBC (such as fatigue, pruritus or jaundice). Liver biopsy was performed in two M2-positive subjects and the histology was compatible with PBC in both cases.

CONCLUSION: Our data, while not assessing the true prevalence of asymptomatic PBC in the general population, suggest that asymptomatic PBC is much more common in China than has been supposed.

Construction and expression of a humanized M2 autoantigen trimer and its application in the diagnosis of primary biliary cirrhosis

AIM: To construct and express a humanized M₂ autoantigen trimer designated as BPO and to apply it in the diagnosis of primary biliary cirrhosis (PBC).

METHODS: cDNA fragments encoding M₂-reactive epitopes of pyruvate dehydrogenase complex E₂ (PDC-E₂), branched chain 2-oxo-acid dehydrogenase complex E₂ (BCOADC-E₂) and 2-oxo-glutarate dehydrogenase complex E₂ (OGDC-E₂) were amplified with PCR using total RNA extracted from human peripheral mononuclear blood cells. The fragments were cloned into the plasmid vector pQE-30 and then transferred into E. coli M15 (pREP4) for expression, which was induced by isopropylthio-β-D-galactoside. The expressed recombinant BPO protein was demonstrated by SDS-PAGE, Western-blotting and Immunoabsorption test, its antigenic reactivity and specificity were identified with seven M_---positive sera confirmed at Euroimmun Research Center (Germany). Using the purified BPO, M2 antibodies in sera from patients with PBC and other liver related diseases were detected with ELISA.

RESULTS: The expressed BPO was observed with both antigenic reactivity and specificity of M₂ autoantigens. The determination of M₂ antibodies by BPO with ELISA was more sensitive than using the Euroimmun's kit with the coefficients of variation less than 10% in both interassay and intraassay. With the newly established method, M2 antibodies were found in 100% (20/20) of patients with PBC. Six cases of liver disease with unknown etiology and 1 patient with drug induced liver injury had detectable levels of serum M₂ antibodies. There were also 2 patients with autoimmune cholangitis and 1 with autoimmune hepatitis showing M₂-antibody positive.

CONCLUSION: Compared with the routine immunofluorescence assay and commercially available assay kit using porcine heart mitochondrial protein as the antigen, the detection system established in the present study shows higher sensitivity and specificity and may be used as a powerful tool for the diagnosis of PBC.

Review article: is there an optimal therapeutic regimen for antimitochondrial antibody-negative primary biliary cirrhosis (autoimmune cholangitis)?

Testing for antimitochondrial antibodies is the most useful laboratory procedure in the diagnosis of primary biliary cirrhosis; nevertheless, 5-10% of patients with typical features of primary biliary cirrhosis do not have detectable antimitochondrial antibodies, their condition being referred to as antimitochondrial antibody-negative primary biliary cirrhosis or "autoimmune cholangitis". Uncertainty exists whether antimitochondrial antibody-positive and -negative primary biliary cirrhosis represent distinct entities. We reviewed studies that compared: (i) the clinical, laboratory and histological characteristics of antimitochondrial antibody-positive and -negative primary biliary cirrhosis; (ii) the response to treatment of both conditions; and (iii) the response of autoimmune cholangitis to ursodeoxycholic acid and immunosuppressive therapy. Antimitochondrial antibody-positive and -negative primary biliary cirrhosis were characterized by similar clinical, laboratory and histological abnormalities, clinical course and survival. Antimitochondrial antibody status did not seem to affect the response to ursodeoxycholic acid. At present, the efficacy of therapies for autoimmune cholangitis has not been established in controlled trials. Of 52 patients with autoimmune cholangitis treated with ursodeoxycholic acid in 13 uncontrolled studies, 83% had serum biochemical improvement. Also, a favourable effect of immunosuppressive drugs occurred in 57% of 54 patients with autoimmune cholangitis in 17 uncontrolled studies. Each of these trials included very few patients and most evaluated the effects of treatment on surrogate markers of disease only. No marker that consistently distinguished patients who would respond favourably to ursodeoxycholic acid or immunosuppression was apparent. Consequently, treatment is, at present, empirical. However, ursodeoxycholic acid may be given when histology reveals bile duct lesions, whereas immunosuppressive therapy should probably be reserved for patients exhibiting interface hepatitis.

Enhanced intrahepatic inducible nitric oxide synthase expression and nitrotyrosine accumulation in primary biliary cirrhosis and autoimmune hepatitis

BACKGROUND/AIMS

Nitrosative stress resulting from increased nitric oxide (NO) synthesis contributes to the pathogenesis of chronic inflammatory diseases, including chronic viral hepatitis. Our goal was to assess the expression of inducible nitric oxide synthase (iNOS) and the formation of nitrotyrosine (NTY), as a marker of nitrosative stress, in liver biopsies from primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH) patients.

METHODS

Intrahepatic expression of iNOS and NTY was measured immunohistochemically and compared to histological scores of the severity of liver disease.

RESULTS

Hepatocellular iNOS expression was observed in liver sections from PBC patients (with a diffuse lobular distribution) and from AIH patients (marked staining in areas of pronounced inflammation and necrosis), but not in control liver sections, including non-autoimmune cholestatic liver disease. Liver samples from PBC and AIH patients, but not from controls, showed NTY accumulation in clusters of hepatocytes and Kupffer cells. Increased iNOS expression and NTY accumulation correlated with the histological severity of PBC or AIH, especially with the degree of inflammation.

CONCLUSIONS

Patients with PBC and AIH showed an enhanced intrahepatic iNOS expression and NTY accumulation, related to the histological severity of liver disease, consistent with NO-mediated nitration of hepatocellular proteins contributing to liver damage in both diseases.