POS0180 TYPE I INTERFERON DEPENDENT HSA-MIR-145-5P DOWNREGULATION MODULATES MUC1 AND TLR4 OVEREXPRESSION IN SALIVARY GLANDS FROM PRIMARY SJÖGREN’S SYNDROME PATIENTS

Background: Primary Sjogren’s syndrome (pSS) is an autoimmune and inflammatory disease that mainly affects the salivary glands (SG) and is characterized by an overactivation of the type I interferon pathway (IFNs I). IFNs I are known to regulate the levels of microRNAs (miRNAs), non-coding RNAs whose levels are altered in pSS. IFNs I can decrease the levels of miR-145-5p, a miRNA with anti-inflammatory roles that has been reported downregulated in SG of from pSS patients [1]. This miRNA has TLR4 and MUC1 transcripts as predicted targets. MUC1 and TLR4 are two proteins overexpressed in SG of pSS patients that contribute, through various mechanisms, to the inflammatory state and glandular dysfunction [2-3]. Thus, we propose that IFNs I may contribute to a self-perpetuating inflammation loop through a hsa-miR-145-5p dependent MUC1 and TLR4 overexpression in the SG of pSS patients. Objectives: to evaluate whether mRNA levels of MUC1 and TLR4 are modulated by hsa-miR-145-5p in a IFNs I dependent manner. Methods: 13 pSS patients and 9 controls SG biopsies were analyzed. hsa-miR-145-5p levels were determined by TaqMan assays and MUC1, TLR4, IFN-α and IFN-β mRNA levels by RT-qPCR. Additionally, in vitro assays using type I IFNs and chemically synthesized hsa-miR-145-5p mimics and inhibitors were performed to study its effect on MUC1 and TLR4 expression. JAK1 and STAT1 mRNA levels were also measured. Results: By Taqman assays we validated the decreased hsa-miR-145-5p levels (p=0.0001) in SG of pSS patients compared to controls. The decreased hsa-miR-145-5p levels correlated inversely with the increased mRNA levels of IFN-β (p=0.0192) in SG of pSS-patients. The hsa-miR-145-5p downregulation also correlated inversely with the overexpression of its predicted targets MUC1 (p=0.010) and TLR4 (p=0.0004). In vitro assays showed that IFN-β induces the overexpression of JAK1 ( Conclusion: Our findings suggest that IFNs I could induce the downregulation of hsa-miR-145-5p leading to the overexpression of MUC1 and TLR4 in SG from pSS patients. TLR4 is activated by ectopic mucins in the SG extracellular matrix from pSS patients which induces pro-inflammatory cytokines secretion [3]. Furthermore, the high levels of the MUC1-SEC and MUC1-Y isoforms observed in SG from pSS patients may favor cytokine synthesis through the immuno-enhancing peptide of MUC1-SEC or through the formation of a MUC1-SEC/MUC1-Y complex [4]. Therefore, IFNs I may contribute to the development of SS through amplification and perpetuation of inflammation due to a hsa-miR-145-5p dependent MUC1 and TLR4 overexpression. References: [1]I. Alevizos, et al,. Arthritis Rheum, 2011;63:535-44. [2]HH. Sung, et al,. Oral Dis. 2015;21(6):730-8. [3]MJ. Barrera, et al,. Rheumatology (Oxford). 2015;54(8):1518-27 [4]LM. Herbert, et al,. Cancer Res. 2004;64(21):8077-84. Acknowledgements: Fondecyt 1210055, Fondecyt 1160015, Fondecyt Iniciacion 11170049, Fondecyt Iniciacion 11201058, CONICYT fellowship (DJ, PC) Disclosure of Interests: None declared