We previously reported adiponectin (AD) is highly expressed in the inflamed synovial joint tissue and correlates closely with progressive bone erosion in Rheumatoid arthritis (RA) patients. Here, we investigate the role of adiponectin in regulating Th17 response and the expression of receptor activator of nuclear factor-κB ligand (RANKL) in mice with CIA mice by intraarticularly injection of adiponectin into knee joints on day 17, day 20 and day 23 post first collagen immunization. The increased adiponectin expression was found in inflamed joint tissue of collagen-induced arthritis (CIA) mice. Adiponectin injection resulted in an earlier onset of arthritis, an aggravated arthritic progression, more severe synovial hyperplasia, bone erosion and osteoporosis in CIA mice. CD4⁺IL-17⁺Th17 cells, IL-17 mRNA and RANKL mRNA expression were markedly increased in the joint tissue of adiponectin treated CIA mice. Moreover, adiponectin treatment markedly enhanced Th17 cell generation from naive CD4⁺T cellsin vitro, which accompanied by the high expression of Th17 transcription factor ROR-γt and Th17 cytokine genes included IL-22 and IL-23. This study reveals a novel effect of adiponectin in exacerbating CIA progression by enhancing Th17 cell response and RANKL expression.

T-614 (also named as iguratimod), a novel antirheumatic drug, could attenuate joint inflammation and articular damage in rheumatoid arthritis (RA) patients, providing a new therapy for RA. Here, we tested the role T-614 on the IL-6-induced receptor activator of nuclear factorκB ligand (RANKL)/osteoprotegerin (OPG), IL-17, and MMP-3 expression in synovial fibroblasts from rheumatoid arthritis (RASFs) patients. T-614 decreased RANKL expression and RANKL/OPG ratio in IL-6-induced RASFs. We confirmed this effect by a decrease of the mRNA and protein RANKL and mRNA RANKL/OPG in RASFs exposed in vitro to T-614 or MTX. Markedly decreased levels of IL-17, retinoid-related orphan receptor C (RORc), and MMP-3 mRNA expression were also observed in IL-6-induced RASFs in the presence of T-614 or MTX compared with those in its absence. Furthermore, T-614 blocked expression of p-ERK1/2 protein without affecting ERK1/2 expression, indicating that the way that T-614 regulated RANKL expression might be ERK1/2 pathway. Our results suggest that T-614 yields a strong improvement in arthritis via exact suppression of RANKL/OPG, IL-17, and MMP-3 expression in RASFs.

B1a cells play a pathogenic role in the development of autoimmune arthritis

We previously reported that adiponectin (AD) promotes naïve T cell differentiation into Th17 cells and participates in synovial inflammation and the bone erosion process in patients with rheumatoid arthritis. Here, we use mice conditionally deficient in adiponectin receptor 1 (AdipoR1) in the T cell lineage to investigate the role of AdipoR1 in Th17 pathway regulation. RNA-sequencing (RNA-seq) demonstrated that AdipoR1 knockout reduced the expression of a variety of T cell related genes, with Rorc showing the greatest level of down-regulation. AdipoR1 deficiency inhibited Th17 cell differentiation in vitro and ameliorated joint inflammation in antigen-induced arthritis mice. Moreover, AdipoR1-deficent CD4+T cells displayed reduced Hypoxia-Inducible Factor-1α expression leading to glycolysis inhibition during naïve CD4+T cell differentiation into Th17 cells. We describe a novel AdipoR1 function in regulating Th17 cell differentiation through modulating HIF-1α-dependent glycolysis.