Gene expression profile of TIARP-deficient macrophages or neutrophils, compared with WT macrophages or neutrophils

[Background] TNFa-induced adipose-related protein (TIARP) is a six-transmembrane protein that is expressed on macrophages, neutrophils and synoviocytes. We have recently reported that TIARP deficient mice (TIARP-/-) spontaneously developed arthritis, and had the high susceptibility to collagen-induced arthritis (CIA) with enhanced interleukin (IL)-6 production. However, the effect of TIARP to neutrophils and fibroblast-like syonoviocytes (FLS) has not been clearly elucidated. [Methods] We analyzed the roles of TIARP in K/BxN serum transfer model using TIARP-/- mice. We characterized the differences of neutrophils between WT and TIARP-/- mice by DNA microarray. Transmigration assays of TIARP-/- neutrophils were performed in vitro and in vivo. FLS were cultured with TNFα and the production of CXCL2 (a specific ligand of CXCR1 and CXCR2) and IL-6 were measured by ELISA. Moreover, TIARP-/- mice transferred with K/BxN serum were treated with anti-IL-6R antibodies. [Results] Arthritis in TIARP-/- mice transferred with K/BxN serum was significantly exacerbated. We identified overexpression of CXCR1 and CXCR2 in TIARP-/- neutrophils by DNA microarray. Neutrophils from TIARP-/- mice showed strong migration activity. The enhancement of chomotactic activity of TIARP-/- neutrophil was greatly facilitated by CXCL2 in vitro and in vivo. In addition, TIARP-/-FLS has enhanced the production of CXCL2 and IL-6 and the cell proliferation in the presence of TNFa, and the blockade of IL-6R significantly attenuated arthritis in vivo. [Conclusion] Our findings indicate that TIARP might down-regulate the production of CXCL2 and IL-6 in FLS, and the expression of chemokine receptors (CXCR1 and CXCR2) in neutrophils, resulting in the protective ability of neutrophils migration into arthritic joints. Mice were treated with thiogycollate medium intraperitoneally. After 3 days, peritoneal macrophages were isolated from three WT or TIARP-deficient mice, and these cells were stimulated by TNFα for 24 hours. Ly6G+ Neutrophils were isolated from splenocytes by MACS.