TIARP attenuates autoantibody-mediated arthritis via the suppression of neutrophil migration by reducing CXCL2/CXCR2 and IL-6 expression.

TNFα-induced adipose-related protein (TIARP) is a six-transmembrane protein expressed on macrophages, neutrophils and synoviocytes. We reported recently that mice deficient in TIARP (TIARP) spontaneously develop arthritis and are highly susceptible to collagen-induced arthritis (CIA) with enhanced interleukin (IL)-6 production. However, the effects of TIARP on neutrophils and fibroblast-like synoviocytes (FLS) have not been elucidated. We analyzed the roles of TIARP in K/BxN serum transfer model using TIARP mice. Arthritis in TIARP mice transferred with K/BxN serum was significantly exacerbated compared with WT mice. We characterized the differences in neutrophils between wild-type (WT) and TIARP mice by DNA microarray. Overexpression of CXCR1 and CXCR2 was noted in TIARP neutrophils. Neutrophils of TIARP mice showed strong migration activity, which was markedly facilitated by CXCL2 in vitro and in vivo. Moreover, enhanced production of CXCL2 and IL-6 and cell proliferation was noted in TIARP TNFα-stimulated FLS. Blockade of IL-6R significantly attenuated serum-transferred TIARP arthritis with diminished neutrophil recruitment in joints. Our findings suggested that TIARP independently down-regulated CXCL2 and IL-6 production by FLS, and the expression of chemokine receptors (CXCR1 and CXCR2) in neutrophils, with resultant reduction of neutrophil migration into arthritic joints.