FRI0268 Dna demethylation characterizes salivary gland epithelial cells from patients with primary sjögren’s syndrome

Background Sjogren’s syndrome (SS) is an autoimmune exocrinopathy characterized by an epithelium injury with dense lymphocytic infiltrates composed of activated T and B cells. Present at the interface of genetic and environmental risk factors, epigenetic modifications are suspected to play a key role in SS. Objectives to characterize DNA methylation in SS. Methods 5 methyl cytosine (5MeCyt) ELISA tested global DNA methylation within long-term culture salivary gland epithelial cells (SGEC) and peripheral blood T and B cells from eight SS patients. DNA methylation/demethylation partners were tested by real time quantitative PCR (DNMT1, DNMT3a/b, PCNA, UHRF1, MBD2, MBD4, and Gadd45-alpha). Immunofluorescence was conducted on labial salivary gland biopsy. Co-culture experiments were performed using the human salivary gland cell line (HSG) and B cells. Results Global DNA methylation was reduced in SGEC from SS patients (5MeCyt: 36.3±3.2% in SS versus 43.1±3.3% in controls, P =0.01), while no differences were observed in T and B cells. SGEC demethylation in SS patients was associated with a 7-fold decrease in DNA methyl transferase (DNMT) 1 and a 1.8-fold increase in Gadd45-alpha expression. The other DNA methylation/demethylation partners tested were not different from controls. Interestingly, SGEC demethylation may be attributed in part to the infiltrating B cells as suspected from the analysis of salivary gland biopsy in SS patients treated with rituximab (anti-CD20). Such hypothesis was confirmed using co-culture experiments with HSG cells and B cells revealing an alteration of the ERK/DNMT1 pathway. Finally, several SGEC genes were overexpressed due to DNA methylation changes including ICAM-1 and human endogenous retrovirus (HERV). Conclusions As a consequence, part of the SGEC dysfunction in SS may be linked to epigenetic modifications and this tissue-specific defect may be ascribed in part to infiltrating B cells, thus opening new therapeutic perspectives in SS. Disclosure of Interest : None Declared