Characterization of antiapoptotic microRNAs in primary Sjögren's syndrome

During the development of primary Sjögren's syndrome (pSS), aberrant expression of autoantigen is a hallmark event. To explore the regulation of autoantigen tripartite motif containing 21 (Ro/SSA, TRIM21), microRNA profiling was performed in our previous study. In which, two TRIM21-targeting microRNAs were identified, namely miR-1207-5p and miR-4695-3p. To further pursue their roles in the development of pSS, assays were performed with cultured human submandibular gland (HSG) cells, and salivary gland tissues. Results showed that transfection of miR-1207-5p or miR-4695-3p mimics down-regulated not only the expression of TRIM21, but also the levels of pro-apoptotic genes B cell lymphoma 2 associated X (BAX), Caspase 9 (CASP-9) and Caspase 8 (CASP-8). This finally led to antiapoptotic phenotypes in HSG cells. Consistent with the antiapoptotic activity, transfection of microRNA inhibitors up-regulated the expression of TRIM21 and led to a pro-apoptotic phenotype. These therefore propose miR-1207-5p and miR-4695-3p as two antiapoptotic microRNAs functioning through apoptosis pathway. Supporting this speculation, assays performed with salivary gland tissues revealed down-regulation of miR-1207-5p and miR-4695-3p, as well as up-regulation of TRIM21 and pro-apoptotic CASP-8 gene in pSS samples. SIGNIFICANCE OF THE STUDY: For pSS patients, apoptosis of acinar and ductal epithelial cells has been proposed to be a potential mechanism that impairs the secretion of salivary glands. In our study, two autoantigen-targeting microRNAs were characterized as antiapoptotic microRNAs functioning through apoptosis pathway, which may be potential targets for the treatment of pSS.