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

TNFα-induced adipose-related protein is a six-transmembrane protein expressed on macrophages, neutrophils and synoviocytes. We reported recently that mice deficient in spontaneously develop arthritis and are highly susceptible to collagen-induced arthritis (CIA) with enhanced interleukin (IL)-6 production. However, the effects of TIduanyu37 on neutrophils and fibroblast-like synoviocytes (FLS) have not been elucidated. We analyzed the roles of TIduanyu37 in K/BxN serum transfer model using mice. Arthritis in TIduanyu37^-/- mice transferred with K/BxN serum was significantly exacerbated compared with WT mice. We characterized the differences in neutrophils between wild-type (WT) and TIduanyu37^-/- mice by DNA microarray. Overexpression of CXCR1 and CXCR2 was noted in TIduanyu37^-/- neutrophils. Neutrophils of TIduanyu37^-/- 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 TIduanyu37^-/- TNFα-stimulated FLS. Blockade of IL-6R significantly attenuated serum-transferred TIduanyu37^-/- arthritis with diminished neutrophil recruitment in joints. Our findings suggested that TIduanyu37 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.

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