AB0102 SPECIALIZED PRO-RESOLVING MEDIATOR RECEPTORS AS INFLAMMATORY RESOLUTION BIOMARKERS IN RHEUMATOID ARTHRITIS

Abstract

Background:The regulation of inflammation is a dynamic process involving several molecules as lipid mediators. The Specialized Pro-resolving Mediators (SPMs), such as Resolvin (RvD and RvE), Protectins, Maresins and Lipoxin A4 (LXA4), are bioactive metabolites of omega-3 and omega-6 fatty acids which drive inflammatory resolution phase and promote tissue repair. ERV, ALX/FPR2 and BLT1 are SPM receptors. Although in Rheumatoid Arthritis (RA) lipid mediators role within pathophysiology is under definition, studies on SPMs receptors role are still lacking in this disease.Objectives:Purpose of this study is to define ERV, ALX/FPR2 and BLT1 expression in blood derived leukocytes and synovial cells and to correlate it to disease activity to define SPM receptors ad inflammatory resolution biomarkers in RA patients.Methods:A cohort of 52 RA patients was enrolled in the study of which 40 with active disease (DAS28= 5,35 (5,18-6,40)) and 12 in sustained remission status (DAS28= 2,1 (1,83-2,42)). Each enrolled patient underwent peripheral blood (PB) drawing and 46 of them underwent US-guided synovial tissue (ST) biopsy. FACS gating strategy was used for PB and ST processing to evaluate percentage of positive cells and the mean fluorescence intensity (MFI) of ERV+, ALX/FPR2+and BLT1+in CD45+CD3+, CD45+CD19+for PB and ST, CD45+CD14+and neutrophils for PB only and CD45-CD90+, CD45+CD64+CD11b+macrophages (distinct in CD206+and CD206-subpopulations) for ST only. Each included ST was stained with haematoxylin/eosin and categorized by a pathologist, blinded to clinical characteristics, using the Krenn Score (KS) to assess ST inflammation degree. As control group, 11 undifferentiated peripheral inflammatory arthritis (UPIA) patients were enrolled in the study.Results:Considering the whole RA cohort, DAS28 inversely correlated with BLT1+positive cells on ST-derived CD45+(r= -0.48; p= 0.048), CD3+(r= -0.56; p= 0.019) and CD19+(r= -0.49; p= 0.042) cells, in contrast with CD90+(r= 0.50; p= 0.041) cells. Similarly, both DAS28 and KS inversely correlated with ALX/FPR2+positive cells in ST-derived CD45+(r= -0.42, p= 0.050 and r= -0,41, p= 0,046 respectively) cells. Evaluating the MFI levels of the SPM receptors along all RA stages (naïve-to-treatment, resistant-to-treatment, sustained remission) compared with UPIA control group, interestingly ST-derived CD45+cells of remission RA were depleted of ERV1 compared to naïve-to-treatment RA (p=0.04), despite comparable ST inflammation. Furthermore, highest ERV1 expression was found in ST-derived CD45+CD3+and CD45+CD19+cells in naïve-to-treatment RA compared with UPIA patients (p= 0,045 and p= 0,012 respectively). Moreover, the lowest BLT1 level was found in remission RA CD3+cells compared with UPIA and naïve-to-treatment RA patients (p= 0,008 and p= 0,023 respectively).Conclusion:SPM receptors expression seem to be tightly related to disease activity in the synovial tissue, suggesting an important involvement in the inflammatory process in RA patient.