Increased serum aminotransferases associated with anti-mitochondrial antibodies in systemic lupus erythematosus patients with autoimmune liver disease

Antimitochondrial Antibodies: from Bench to Bedside

Anti-mitochondrial antibodies (AMA) are directed against the E2 subunits of the 2-oxo acid dehydrogenase complexes (PDC-E2) and are the typical biomarkers of primary biliary cholangitis (PBC), being present in 90-95% of patients, with increasing sensitivity at increasing titers. Albeit being highly specific for PBC diagnosis, AMA can be detected in less than 1% of healthy subjects, and thus the management subjects with no sign or symptom of liver disease is still a challenge and data concerning clinical risk of developing PBC in this subgroup of patients are controversial. Moreover, AMA can also be detected in patients affected by overlap syndrome, as well as hepatic diseases (i.e., NASH and viral hepatitis), while the association with autoimmune diseases, in particular Sjögren's syndrome, systemic sclerosis, and systemic lupus erythematosus, is well established. Furthermore, new associations are being identified with inflammatory myositis and heart disease. AMA are directed towards the pyruvate dehydrogenase multi enzyme complex (PDC-E2) subunit, which represents an epithelial specific autoantigen for PBC. This review focuses on the main characteristics of AMA, their association with autoimmune diseases and liver diseases.

Prevalence of antimitochondrial antibodies in subacute cutaneous lupus erythematosus

BACKGROUND

In approximately 13% of systemic lupus erythematosus (SLE) patients, a hallmark of primary biliary cirrhosis (PBC) can be detected: antimitochondrial M2 antibodies (AMA-M2). It has not been determined if the presence of AMA-M2 in SLE patients results in a higher risk of PBC in comparison to those with AMA but no SLE. Until now, there have been no such analyses among individuals with subacute cutaneous lupus erythematosus (SCLE).

METHODS

To assess the seropositivity rates for AMA-M2 and autoantibodies associated with autoimmune hepatitis in patients with newly diagnosed SCLE and to determine the coexistence and risk of development of autoimmune liver disease in these patients within 1 year of follow-up, data from 33 patients with newly diagnosed SCLE were analyzed.

RESULTS

AMA-M2 was found in 20% of SCLE patients. Patients from the AMA-M2-positive group were characterized by significantly higher levels of cholestatic liver enzymes when compared to those without AMA-M2 (P < 0.05). After introducing therapy with hydroxychloroquine and prednisone, the levels of hepatocellular enzymes increased significantly only in AMA-M2 positive patients (P < 0.05).

CONCLUSIONS

A high prevalence of AMA-M2 was found in patients with SCLE. Patients with SCLE and AMA-M2 had significantly higher values of cholestatic enzymes than patients without AMA. Newly diagnosed patients with SCLE should be screened for the presence of AMA and should be clinically followed up. Avoiding drugs with potential liver toxicity should be recommended in patients with SCLE and AMA.

The binding of SLE autoantibodies to mitochondria

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by immune complexes. Because these complexes contain mitochondrial components, we assessed the presence of antibodies to whole mitochondria (wMITO) using an ELISA in which mitochondria from mouse liver are bound to microtiter plates pre-coated with poly-l-lysine. Studies with this ELISA demonstrated that SLE plasmas contain abundant anti-wMITO activity. While digestion with DNase 1 did not affect anti-wMITO activity, adsorption of plasma on DNA affinity columns could reduce binding activity. Assay for anti-mitochondrial antibodies (AMA) by immunofluorescence and an ELISA with the M2 antigen (2-oxo-acid dehydrogenase protein complex) showed a low frequency of positivity, indicating that AMA and anti-wMITO are distinct specificities. In the study of 204 patients with SLE, the levels of anti-wMITO were higher in active SLE and correlated with levels of anti-DNA. These findings suggest that anti-wMITO can form immune complexes with mitochondria which may drive pathogenesis.

Spectrum of autoantibodies for gastrointestinal autoimmune diseases in systemic lupus erythematosus patients

Background

Organ-specific autoimmune diseases may appear in patients with systemic lupus erythematosus (SLE). Gastrointestinal symptoms are well documented in SLE and may be similar to those related to autoimmune gastrointestinal diseases.

Objective

Our aim was to search for gastrointestinal organ-specific autoantibodies in 194 patients with systemic lupus and 103 healthy controls from Southern Brazil.

Methods

Anti-endomysium antibodies (IgA-EmA), anti-gastric parietal cells (GPC) antibodies, anti-smooth muscle antibodies (ASMA), anti-mitochondrial antibodies (AMA) and anti-LKM-1 (liver-kidney microsomal) were searched for using indirect immunofluorescence in the sera of patients and controls.

Results

The total positivity of antibodies in SLE patients was 14.4% (28/194) and differed significantly from healthy individuals (0.97%; p < 0.001). IgA-EmA was more common in lupus patients than in controls (11/194; p = 0.009), and one of these patients had dermatitis herpetiformis. Clinical association revealed that IgA-EmA was more common in SLE patients with discoid lesions. The frequency of anti-GPC ( p = 0.10), ASMA ( p = 0.16) and AMA ( p = 0.55) did not differ significantly between groups. No patient presented LKM-1 autoantibodies. One patient presenting anti-GPC was diagnosed with atrophic gastritis and pernicious anemia.

Conclusion

Only IgA-EmA was significantly associated with lupus and with the presence of discoid lesions. Until now, no obvious association with celiac disease has been found.

Autoantibodies to asialoglycoprotein receptor (ASGPR) measured by a novel ELISA--revival of a disease-activity marker in autoimmune hepatitis

BACKGROUND

The liver-specific ASGPR is an autoantigen in autoimmune hepatitis (AIH) patients. Anti-ASGPR antibody correlates with disease activity, however, only in-house assays have been reported so far.

METHODS

Rabbit ASGPR was purified by affinity chromatography on galactose-Sepharose and used for standardised detection of anti-ASGPR by ELISA. Anti-ASGPR IgG was measured in sera from 45 patients with AIH, PBC (n=43), alcoholic liver disease (n=13), HBV infection (n=35), HCV infection (n=53), and 118 blood donors. Anti-ASGPR was correlated with biochemical parameters of disease activity in 22 AIH patients with consecutive samples.

RESULTS

Twenty-one of 30 untreated (70%) and five of 15 treated AIH patients (30%) showed elevated anti-ASGPR at first presentation. Only one blood donor demonstrated anti-ASGPR. ALD and PBC patients were all negative. ROC curve analysis of AIH and disease-control patients revealed a sensitivity of 77.8% and a specificity of 99.4%. Three (8.6%) of 35 HBV and 7 (13.2%) of 53 HCV patients demonstrated elevated anti-ASGPR. In AIH patients, anti-ASPGR correlated with liver-transaminases levels. In 22 follow-up patients, elevation of anti-ASPGR preceded liver-transaminases increase.

CONCLUSIONS

The novel anti-ASGPR ELISA is a readily available and specific diagnostic tool for anti-ASGPR detection in AIH. Quantification of anti-ASGPR is helpful in monitoring disease activity.