The Role Of Cathepsin S In The Pathogenesis Of Primary Sj(o|¨)gren’s Syndrome

ObjectiveTo explore the role of Cathepsin(Cat) S and the correlated cell subtypes in the pathogenesis of primary Sjogren’s syndrome(pSS).Methods1. Indirect enzyme-linked immunosorbent assay was used to detect the serum concentrations of total-and pro-Cat S respectively in 37 pSS patients and 33 healthy controls. The relation between the serum levels of Cat S and EULAR Sj(o|")gren’s Syndrome Disease Activity Index (ESSDAI) and the serum levels of immunoglobulin (Ig) G and rheumatoid factor were analyzed.2. Immunohistochemical analysis of labial gland tissue was performed to detect the expression of Cat S. Furthermore, The correlation between the expression of Cat S and focus scores(FS) was analyzed.3. The colocalization analysisof Cat S, CD68, CD20 and CD83 were analyzed by immunofluorescence, respectively. The percentage of total infiltrating mononuclear cells(MNCs) of each cell subtype(including CD20+B, CD3+T, CD68+macrophage, CD83+dendritic cell, and CD56+NK cell) was analyzed using the Image Pro-Plus Softwarewhich evaluated nuclei.4. The receiver operating characteristic (ROC) curve was used to obtain an optimal cut-off value. The data was analyzed by student’s t-test, Mann-Whitney test and Spearmancorrelation analysis.Results1. The serum levels of total-Cat S, pro-Cat S and active-Cat S in pSS group were significantly higher than in healthy controls (p<0.05).2. Moreover, the serum levels of total-Cat S, pro-Cat S and active-Cat S in pSS group were not correlated with the levels of IgG, RF and ESSDAI (p>0.05).3. The area under ROC curve (AUC) of total-Cat S, pro-Cat S and active-CatS was 0.811 (p<0.01),0.655 (p<0.05) and 0.701 (p<0.01), respectively. The optimal cut-off value was 15.77ng/ml,12.62ng/ml and 4.062ng/ml, respectively, with the sensitivity of 0.919,0.676 and 0.622 and specificity of 0.697,0.667 and 0.758.4. Immunohistochemical analysis of labial gland tissue of pSS patients showed positive expression of Cat S which was distributed in the infiltrated mononuclear cells, acinar cells and ductal epithelial cells while not in controls. Furthermore, the expression of Cat S was positively correlated with FS (p<0.05).5. The minor salivary glands(MSG) lymphocytic infiltrates mainly consist of CD3+T and CD20+B cells, whereas a small proportionof classicalantigen-presenting cells (macrophages and dendritic cells) were detected.6. In pSS patients with low FS, CD56+NK cells existedprimarily within these inflammatory foci. In contrast, in pSS patients with high FS,NK cells existed mostly outside of and along the edges of the inflammatory foci.Conclusions1. Not noly the levels of serum Cat S but also the expression of Cat S in MSG were higher than controls. Additionally, the expression of Cat S was colocalized with the professional antigen-presenting cells (APC, including B cells, dendritic cells and macrophages) and the non-professional APC (including acinar cells and duct epithelial cells), and was correlated with the FS, which suggests that Cat S play a critical role in the pathogenesis of pSS by promoting the self-antigen presentation process. Cat S may become a new serological marker and potential therapeutic target.2. Interestingly, the localization of CD56+NK cells in inflammatory foci varies with different FS, which indicates that NK cells might play a different role in the early and late stages ofthe disease.