ABSTRACT
Objective To investigate the pathogenesis of the production of anti-neutrophil cytoplasmic antibodies (ANCA) in the rat models of chronic bronchitis (CB) with recurrent infections. Methods The CB models were made by double element of smoking and lipopolysaccharide (LPS) stimulation. The rats were divided into four groups, including normal control group (n=5), phorbol-12-myristate-13-acetate (PMA)-treated healthy rats control group (n=5), CB rats group (n=5) and PMA-treated CB rats group (n=6). Renal function of rats was detected. The histopathological lung and kidney tissues were observed by HE staining of paraffin section. Immunological markers, including myeloperoxidase anti-neutrophil cytoplasmic antibodies (MPO-ANCA), proteinase 3 anti-neutrophil cytoplasmic antibodies (PR3-ANCA) and citrullinated histone H3 (CitH3), were measured by enzyme-linked immune-sorbent assay (ELISA) at different time points. Correlation between CitH3 and MPO-ANCA was analyzed by the Spearman rank correlation. NETs components were further detected in lung and kidney tissue by confocal immunofluorescence and colocalization analysis. Results (1) The serum levels of CitH3 and MPO-ANCA in CB+PMA group showed an increased trend. Compared with those in the normal control group and CB rats group, the serum levels of CitH3 and MPO-ANCA in CB+PMA group increased significantly at the sixth week (both P＜0.05). Serum CitH3 levels in rats were positively correlated with serum MPO-ANCA levels (rs=0.490,P=0.024). (2) There were pathological manifestations of CB in the lung tissues of rats in CB group and CB+PMA group, and no obvious abnormalities in the lung tissues of rats in the normal control group and control group. In the rat kidney tissue of CB+PMA group, there were inflammatory cells infiltrated in the glomerular and around the renal tubules, but glomerular necrosis was not found. No obvious abnormalities were observed in the kidney tissues of rats in the normal control group, PMA-treated healthy rats control group and CB group. (3) In the lung and kidney tissues of CB+PMA group NETs could be detected by confocal immunofluorescence analysis. Conclusion CB rats with the recurrent infections can release large amounts of NETs, in which the exposure of MPO antigen will break the immune tolerance and result in the production of MPO-ANCA.