Identification and characterization of autoantibodies against catalase and α-enolase in patients with primary sclerosing cholangitis

Abstract

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease of unknown aetiology. Recent studies have shown that genetic factors and both cellular and humoral immunological abnormalities are important in the pathogenesis of PSC. The most prominent autoantibodies in PSC are anti-neutrophil cytoplasmic antibodies (ANCA). The autoepitopes of ANCA in PSC are not well defined. The aim of this study was to identify corresponding ANCA autoantigens in patients with PSC. A biochemical approach with enrichment and partial purification of soluble neutrophil proteins, detection of autoantibodies by Western blot and partial amino acid sequencing were used. Two new autoantigen/autoantibody systems in patients with PSC were detected: catalase and alpha-enolase. The presence of catalase autoantibodies in 9/15 (60%) and alpha-enolase autoantibodies in 4/15 (27%) was confirmed by ELISA and Western blot. Furthermore, we showed immunoreactions of PSC sera with human biliary epithelial cells, showed the reduction of fluorescence in anti-catalase absorption experiments and observed partial co-localization of anti-catalase antibodies and PSC sera in double-staining experiments on biliary epithelial cells. The anti-catalase antibody-positive PSC patients had a more severe course of disease with a significantly higher alkaline phosphatase compared with the anti-catalase-negative PSC patients (P < 0.06). All ulcerative colitis control sera were anti-catalase antibody-negative. The identified antigens catalase and alpha-enolase can partly explain the ANCA fluorescence on ethanol-fixed and formaldehyde-fixed granulocytes in patients with PSC. Catalase is an important anti-oxidant enzyme and prevents cell damage from highly reactive oxygen-derived free radicals. Catalase autoantibodies might play a pathogenic role in patients with PSC. Our findings support the hypothesis that oxidative stress is one of the pathogenic mechanisms in patients with PSC.

Use of Proteomic Methods to Identify Serum Biomarkers Associated with Rat Liver Toxicity or Hypertrophy

“…For enolase (phosphopyruvate hydratase) and methionine adenosyltrans- ferase (MAT), no decreases were noted at the mid and final time points, but at the early time point, Ͼ5-fold decreases were observed. ␣-Enolase is a housekeeping glycolytic enzyme that is not specific to liver but is strongly expressed in biliary epithelial cells (12 ), and ␣-enolase autoantibodies have been found in patients with primary sclerosing cholangitis (13 ). MAT catalyzes the formation of S-adenosylmethionine, an essential metabolite that in turn regulates hepatic functions such as proliferation, differentiation, and death (14 ).…”

An integrated humoral and cellular response is elicited in pancreatic cancer by α‐enolase, a novel pancreatic ductal adenocarcinoma‐associated antigen

“…18 PDAC patients did not display signs of autoimmunity, though the presence of anti-a-enolase antibodies has been described in patients with autoimmune disorders. 23,[34][35][36][37][38][39] It is known that a-enolase expressed at cell surface acts as a plasminogen receptor. 28,40 The bound plasminogen is more efficiently activated to plasmin and thus contributes to pathological processes such as tumor cell invasion, metastases and inflammatory responses.…”

Increased levels of autoantibodies against catalase and superoxide dismutase associated with oxidative stress in patients with rheumatoid arthritis and systemic lupus erythematosus

“…These reports suggest that the autoimmune background, present in these diseases, induces autoantibodies that inhibit Cu/Zn-SOD activity and thereby contribute to the oxidative stress. Concerning CAT, very few reports describe anti-CAT antibodies in autoimmune diseases (39,40).…”