Background Leukocyte immunoglobulin-like receptor A3 (LILRA3) is a putatively secreted protein belongs to the leukocyte immunoglobulin-like receptor (LILR) family. Our previous study provided the first evidence that the functional LILRA3 was a novel genetic risk for rheumatoid arthritis (RA) in Chinese Han population.
Objectives we undertake this study to investigate the role of LILRA3 on bone destruction in RA patients.
Methods i) The expression of LILRA3 in serum and synovial fluid from patients with RA, OA, and health controls were measured by using ELISA. Bone destruction was scored using modified Sharp-vander Heijde score (SHS) on hands. ii) RAW264.7 cells and peripheral blood mononuclear cells (PBMCs) from RA,OA patients and health controls were cultured in the medium containing different concentration of recombinant LILRA3 protein in the presence or absence of Receptor Activator for Nuclear Factor-κ B Ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Osteoclasts were identified by tartrate-resistant acid phosphatase (TRAP) staining. Bone resorption activity of osteoclasts was determined by bone slices stained with toluidine blue, iii) PBMCs from patients with RA, OA and health controls were transfected with LILRA3 plasmid or control vector. The expression of osteoclasts related genes, including TRAP, CTSK, MMP-9 was measured by q-PCR array and Western Blotting method. MAPK and NF–κB signaling pathway activation levels were detected by Western Blotting method. One-way analysis of variance was used to detect the differences between the group means.
Results Compared with health controls, the expression of LILRA3 in RA and OA serum was high and LILRA3 was specifically express in synovial fluid with RA patients. The serum level of LILRA3 in RA patients was positively correlated with bone damage. We demonstrated that LILRA3 can promote bone damage independently or synergy with RANKL in RAW264.7 cells through MAPK and NF–κB signaling pathway. Furthermore, we proved that LILRA3 can induce the differentiation of osteoclasts in the presence of RANKL and M-CSF both in vitro and in a transfect system in PBMCs with RA,OA patients and health controls.
Conclusions Our data indicate that LILRA3 can promote done destruction through MAPK and NF–κB signaling pathway. These findings may give us some clues for the study on the pathogenesis of RA.
Disclosure of Interest None declared