Serum amyloid A expression in liver promotes synovial macrophage activation and chronic arthritis via NFAT5
Meiling Li, … , Donghyun Kim, Wan-Uk Kim
Meiling Li, … , Donghyun Kim, Wan-Uk Kim
Published March 1, 2024
Citation Information: J Clin Invest. 2024;134(5):e167835. https://doi.org/10.1172/JCI167835.
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Research Article Autoimmunity Inflammation

Serum amyloid A expression in liver promotes synovial macrophage activation and chronic arthritis via NFAT5

Abstract

Nuclear factor of activated T-cells 5 (NFAT5), an osmo-sensitive transcription factor, can be activated by isotonic stimuli, such as infection. It remains unclear, however, whether NFAT5 is required for damage-associated molecular pattern–triggered (DAMP-triggered) inflammation and immunity. Here, we found that several DAMPs increased NFAT5 expression in macrophages. In particular, serum amyloid A (SAA), primarily generated by the liver, substantially upregulated NFAT5 expression and activity through TLR2/4-JNK signalling pathway. Moreover, the SAA-TLR2/4-NFAT5 axis promoted migration and chemotaxis of macrophages in an IL-6– and chemokine ligand 2–dependent (CCL2-dependent) manner in vitro. Intraarticular injection of SAA markedly accelerated macrophage infiltration and arthritis progression in mice. By contrast, genetic ablation of NFAT5 or TLR2/4 rescued the pathology induced by SAA, confirming the SAA-TLR2/4-NFAT5 axis in vivo. Myeloid-specific depletion of NFAT5 also attenuated SAA-accelerated arthritis. Of note, inflammatory arthritis in mice strikingly induced SAA overexpression in the liver. Conversely, forced overexpression of the SAA gene in the liver accelerated joint damage, indicating that the liver contributes to bolstering chronic inflammation at remote sites by secreting SAA. Collectively, this study underscores the importance of the SAA-TLR2/4-NFAT5 axis in innate immunity, suggesting that acute phase reactant SAA mediates mutual interactions between liver and joints and ultimately aggravates chronic arthritis by enhancing macrophage activation.

Authors

Meiling Li, Yu-Mi Kim, Jung Hee Koh, Jihyun Park, H. Moo Kwon, Jong-Hwan Park, Jingchun Jin, Youngjae Park, Donghyun Kim, Wan-Uk Kim

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Figure 2

SAA upregulation of NFAT5 expression via TLR2/4-JNK pathway in macrophages.

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SAA upregulation of NFAT5 expression via TLR2/4-JNK pathway in macrophag...
(A and B) Western blot analysis for NFAT5 expression in RAW 264.7 macrophages treated with TAK-242 (TAK) or oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) in the presence of SAA. (C) NFAT5 expression in SAA-treated BMDMs of WT, TLR4 KO (Tlr4–/–) and TLR2/4 double KO (Tlr2/4–/–) mice. (D and E) Increase in phospho-p38 (p-p38), phospho-ERK (p-ERK1/2), phospho-JNK1/2 (p-JNK1/2), and phospho-AKT (p-AKT) levels by SAA (5 μg/mL) in RAW 264.7 macrophages (D) and mouse BMDMs (E), as determined by Western blot. (F) NFAT5 expression in RAW 264.7 macrophages pretreated with SB203580 (SB, 15 [SB15] and 30 μM [SB30]), PD98059 (PD, 30 μM), SP600125 (SP, 10 μM), LY294002 (LY, 10 μM), Wortmannin (Wort, 10 μM), and allopurinol (Allo, 1 mM) for 1 hour. (G and H) SP600125 inhibition of NFAT5 expression in RAW 264.7 macrophages (G) and mouse BMDMs (H) stimulated with SAA. (I) Reduction of NFAT5 expression in RAW 264.7 macrophages by Jnk1/2 siRNA. Cells were transfected with control or Jnk1/2 siRNA for 24 hours and then treated with SAA (5 μg/mL) for 8 hours. Expression of NFAT5 and total JNK1/2 was measured by Western blot analysis. (J) Decrease in p-JNK1/2 expression by Tlr2/4 deficiency. BMDMs of WT, Tlr2–/–, Tlr4–/–, Tlr2/4–/– mice were activated with SAA for the indicated times. Total JNK1/2 and p-JNK1/2 expressions were determined by Western blotting. Data are representative of more than 3 independent experiments with similar results. In experiments for A, B, C, F, G, and H, the cells were stimulated with 5 μg/mL of SAA for 24 hours.