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A7.8 DNA Demethylation in Salivary Gland Epithelial Cells from Patients with Primary Sjögren’s Syndrome may be Ascribed to Infiltrating B Cells
  1. Yves Renaudineau1,2,
  2. Yosra Thabet1,3,
  3. Christelle Le Dantec1,
  4. Ibtissem Ghedira3,
  5. Valérie Devauchelle1,4,
  6. Divi Cornec1,4,
  7. Jacques-Olivier Pers1
  1. 1Research Unit EA2216 “Immunology, Pathology and Immunotherapy”, European University of Brittany, Brest University Medical School Hospital, Brest, France
  2. 2Laboratory of Immunology and Immunotherapy, CHRU Morvan, Brest, France
  3. 3Research Unit 03UR/07-02 “Autoimmunity and Allergy”, Faculty of Pharmacy, Monastir, Tunisia
  4. 4Unit of Rheumatology, CHRU Cavale Blanche, Brest, France

Abstract

Background and Objectives Sjögren’s syndrome (SS) is an autoimmune exocrinopathy characterised by an epithelium injury surrounded by 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. Accordingly, we decided to further characterise DNA methylation in SS.

Materials and Methods We tested, using a 5 methyl cytosine (5MeCyt) ELISA, global DNA methylation in long-term cultured salivary gland epithelial cells (SGEC), peripheral T cells and B cells from eight SS patients. DNA methylation/demethylation partners were assessed by real time quantitative PCR (DNA methyl transferase (DNMT)1, DNMT3a/b, PCNA, UHRF1, MBD2, MBD4, and Gadd45-alpha). Immunofluorescence was conducted on labial salivary gland biopsy. Co-culture experiments were performed associating 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 difference was observed in T and B cells. SGEC demethylation in SS patients was associated with a 7-fold decrease of DNMT1 and a 1.8-fold increase of Gadd45-alpha expression. The other DNA methylation/demethylation partners tested were not differently expressed when compared to controls. Interestingly, SGEC demethylation may be attributed to the B cell infiltrate as DNA methylation increased in salivary gland biopsy after rituximab (anti-CD20 antibody) treatment. Such hypothesis was confirmed using co-culture experiments (HSG cells and B cells) revealing an alteration of the PKC-delta/ERK/DNMT1 pathway. Finally, DNA methylation was associated with the overexpression of several SGEC genes such as ICAM-1 and human endogenous retrovirus (HERV).

Conclusions SGEC dysfunction in SS may be linked to epigenetic modifications and this tissue specific defect may be ascribed in part to infiltrating B cells. This observation opens new therapeutic perspectives in SS.

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