[The effect of Cathepsin S in primary biliary cholangitis]

Objective: To explore the effect of cathepsin (Cat) S in primary biliary cholangitis (PBC). Methods: The serum of PBC patients and Hepatitis B virus (HBV) patients were collected in Peking Union Medical College Hospital from August 2016 to July 2017 and the liver tissue of PBC were collected from March 2010 to July 2013. Indirect enzyme-linked immunosorbent assay (ELISA) was used to detect the serum concentrations of total-and pro-Cat S respectively in 24 PBC patients, 24 Hepatitis B patients and 24 healthy controls. The relation between the serum levels of Cat S and cholestasis biochemical indexes and the serum levels of immunoglobulin (Ig) M, G were analyzed. Immunofluorescence analysis of liver tissue was performed to detect macrophage infiltration and Cat S expression. The data was analyzed by student's t-test, spearman correlation analysis, and receiver operating characteristic (ROC) curve was used to obtain an optimal cutoff value. Results: The serum levels of total-Cat S, pro-Cat S and active-Cat S in PBC group were significantly higher than those in healthy controls and HBV controls (P<0.05). There was a correlation between serum total-Cat S and ALP and GGT in patients with PBC (P<0.05). There was a moderate correlation between pro-Cat S and ALP and GGT (P<0.05) and total Cat S was associated with IgG (P<0.05). The area under ROC curve (AUC) of total-Cat S, pro-Cat S and active-Cat S was 0.85(P<0.01), 0.65(P<0.05) and 0.77(P<0.01), respectively. The optimal cut-off value was 11.30、7.81 and 5.93 pg/L, respectively, with the sensitivity of 0.81, 0.53 and 0.53 and specificity of 0.82, 0.81 and 0.96. Liver tissue immunofluorescence revealed macrophage infiltration in the liver of PBC patients. The average percentage of macrophages and Cat S co-expressed cells in mononuclear cells was 23.77%. Conclusion: The expression of Cat S in serum of patients with PBC is significantly higher than that of healthy controls and HBV patients, and is related to IgG and serum ALP, r-GT levels. Liver tissue macrophages were co-expressed with Cat S. Cat S may participate in the process of antigen presentation in the pathogenesis of PBC.