Session Title: Rheumatoid Arthritis: Animal Models
Session Type: Abstract Submissions (ACR)
Background/Purpose: TNFα-induced adipose-related protein (TIARP) is a six-transmembrane protein induced by TNFα and IL-6 in adipose tissue. Recently, we found that TIARP is dominantly expressed in splenic macrophages and joints of two arthritic mouse models (collagen induced arthritis; CIA and glucose-6-phosphate isomerase (GPI) induced arthritis). In human, TIARP is also observed in human joints from patients with rheumatoid arthritis and clearly upregulated by TNFα stimulation, although the pathogenic mechanisms of arthritis remain unclear. In this study, to elucidate the role of TIARP in the development of arthritis, we have generated TIARP-deficient (TIARP-/-) mice.
(1) We generated TIARP-/- mice in C57BL/6 (B6) background, and investigated several organs in aged (12-month-old) TIARP-/- mice. The level of cytokines in the serum was measured by ELISA. (2) Peritoneal macrophages (PEM) were isolated and cultured with LPS or TNFα. Then, the production of IL-6 in culture supernatant was measured by ELISA. (3) We examined the role of TIARP in NF-κB pathway and apoptosis. PEM were cultured with TNFα, then fluctuation of NF-κB inhibitory molecule IκBα expression was detected by Western blotting. Apoptotic cells were detected by flowcytometry using anti-Annexin V antibodies. (4) We also examined the susceptibility of young (8-12-week-old) TIARP-/- mice to CIA. CIA was induced by immunization with 200μg of chicken type II collagen (CII) emulsified in CFA to B6 mice, followed by boost immunization on day21. The severity of arthritis was monitored by clinical score. (5) The level of anti-CII antibodies in the serum on day30 and 60 were measured by ELISA. (6) The level of IL-6 and TNFα in the serum on day 60 after CII immunization was measured. (7) We examined the effects of anti-IL-6 receptor mAb (MR16-1) on the development of arthritis in TIARP-/- -CIA mice. We injected 2mg of MR16-1 intraperitoneally on day 21 after CII immunization. (8) PEM were cultured with IL-6 for 1 h. The expression of STAT3, phosphorylated-STAT3 (p-STAT3) and SOCS3 were detected by Western blotting.
(1) 80% of aged TIARP-/- mice spontaneously developed arthritis. The levels of IL-6 in the serum from TIARP-/- mice were significantly higher than WT mice. (2) PEM from TIARP-/- produced high amount of IL-6 with LPS or TNFα stimulation. (3) PEM from TIARP-/- mice showed sustained degradation of IkBα compared with WT by TNFα stimulation. TNFa-induced apoptotic cells were increased in WT but unchanged in TIARP-/-. (4) The severity of arthritis in TIARP-/- was higher than that in WT. (5) The level of anti-CII antibodies was comparable between WT and TIARP-/-. (6) The serum IL-6 was significantly increased in TIARP-/- mice, whereas serum TNFα was not detected. (7) Administration of MR16-1 on day 21 significantly suppressed the progression of arthritis in TIARP-/- CIA mice. (8) P-STAT3 expression was enhanced in TIARP-/- compared with WT, whereas SOCS3 expression was comparable between WT and TIARP-/-.
These findings suggest that TIARP is a negative regulator in autoimmune arthritis through the suppression of IL-6 production, NF-κB, STAT3 signaling, and the induction of apoptosis.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/polyarthritis-caused-by-tiarp-tnfaip9-deficiency-critically-dependent-on-dysregulated-stat3-nf-%ce%bab-signaling-and-cell-death-in-macrophage/