Tryptophan 2,3-dioxygenase 2 plays a key role in regulating the activation of fibroblast-like synoviocytes in autoimmune arthritis.

Abnormal kynurenine (Kyn) metabolism has been closely linked to the pathogenesis of rheumatoid arthritis (RA). The aims of this study were to investigate the role of tryptophan 2,3-dioxygenase 2 (TDO2), a rate-limiting enzyme that converts tryptophan (Trp) to Kyn, in regulating fibroblast-like synoviocyte (FLS)-mediated synovial inflammation in autoimmune arthritis. The expression of TDO2 was determined by immunohistochemistry, confocal laser scanning fluorescence microscopy, imaging flow cytometry and Western blot. TDO2 activity was tested by HPLC and colorimetric assay. TDO2 siRNA and TDO2 inhibitor 680C91 were used to inhibit TDO2 in AA-FLS function in vitro. A rat model of adjuvant-induced arthritis (AA) was used to evaluate the in vivo effect of allopurinol (Allo), a TDO2 inhibitor. TDO2 expression was strongly increased in synovial tissue and FLS of RA and AA. Immune cells were found to express high amount of TDO2 proteins at the peak stage of AA. Pharmacological inhibition or knockdown of TDO2 in AA-FLS resulted in a reduced proliferation, secretion, migration and invasion. Kyn restored the inhibitory effect of TDO2 inhibition on activation of AA-FLS. Allo treatment ameliorated the arthritis severity and decreased the activity of TDO2. Our results suggest that elevated TDO2 expression may contribute to synovial inflammation and joint destruction during arthritis. Therefore, targeting TDO2 activity and the Kyn pathway of Trp degradation may represent a potential therapeutic strategy in RA.

Chang Y ，Han P ，Wang Y ，Jia C ，Zhang B ，Zhao Y ，Li S ，Li S ，Wang X ，Yang X ，Wei W ... -  《-》

Inhibition of 6-phosphofructo-2-kinase suppresses fibroblast-like synoviocytes-mediated synovial inflammation and joint destruction in rheumatoid arthritis.

Abnormal glycolytic metabolism contributes to joint inflammation in rheumatoid arthritis (RA). The aims of this study were to investigate the role of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a bifunctional enzyme that controls the glycolytic rate, in regulating fibroblast-like synoviocyte (FLS)-mediated synovial inflammation and invasiveness in RA. A specific inhibitor of PFKFB3, PFK15, and siRNA were used to evaluate the role of PFKFB3. Protein expression was measured by Western blotting or immunofluorescence staining. The expression of cytokines was determined by quantitative real-time PCR. Migration and invasion were measured using a Boyden chamber assay. A mouse model of collagen-induced arthritis (CIA) was used to evaluate the in vivo effect of PFK15. PFKFB3 expression was increased in the synovial tissue and FLSs from RA patients compared with osteoarthritis patients. PFKFB3 inhibition decreased the expression of IL-8, IL-6, CCL-2 and CXCL-10 and the proliferation, migration and invasion of RA FLSs. PFK15 suppressed TNF-α-induced activation of NF-κB and p38, JNK and ERK MAPK signals in RA FLSs. PFK15 treatment also suppressed glucose uptake and lactate secretion. Lactate reversed the inhibitory effect of PFK15 or PFKFB3 siRNA on cytokine expression and migration of RA FLSs. Lactate was also involved in PFKFB3-mediated activation of NF-κB and MAPKs. Intraperitoneal injection of PFK15 in mice with CIA attenuated joint inflammation. Elevated PFKFB3 expression might contribute to synovial inflammation and aggressive behaviours of RA FLSs, suggesting a novel strategy of targeting PFKFB3 to prevent synovial inflammation and joint destruction in RA.

Zou Y ，Zeng S ，Huang M ，Qiu Q ，Xiao Y ，Shi M ，Zhan Z ，Liang L ，Yang X ，Xu H ... -  《-》

Paeoniflorin-6'-o-benzene sulfonate ameliorates the progression of adjuvant-induced arthritis by inhibiting the interaction between Ahr and GRK2 of fibroblast-like synoviocytes.

Aryl hydrocarbon receptor (Ahr) is thought to be a crucial factor that regulates immune responses, which may be involved in the pathogenesis of autoimmune inflammation including rheumatoid arthritis (RA). The results of our group in recent years have shown that Paeoniflorin-6'-O-benzene sulfonate (code: CP-25), a novel ester derivative of paeoniflorin, has a good effect on improving RA animal models. However, whether the anti-arthritis effect of CP-25 is related to Ahr remains unclear. Here, we showed that CP-25 treatment ameliorated adjuvant-induced arthritis (AA), a rat model of RA, by inhibiting Ahr-related activities in fibroblasts like synoviocytes (FLS). AA rats were treated with CP-25 or paroxetine from days 17 to 33 after immunization. We showed that CP-25 alleviated arthritis symptoms and the pathological changes. Treatment with CP-25 decreased the expression of Ahr in the synovium of AA rats. CP-25 inhibited the expression of Ahr and the G protein-coupled receptor kinase 2 (GRK2) as well as the co-expression of GRK2 with Ahr in FLS of AA rats. Furthermore, CP-25 down-regulated the production of Kyn in FLS of AA rats. These results suggested that CP-25 may inhibit the expression and activation of Ahr. Besides, treatment with CP-25 reduced the proliferation and migration of MH7A caused by Ahr activation. In addition, we also demonstrated that CP-25 down-regulated the total and nuclear expression of Ahr and the expression of GRK2 in Kyn-treated MH7A. Moreover, the co-expression and co-localization of Ahr and GRK2in Kyn-treated MH7A were also repressed by CP-25. The data presented here demonstrated that CP-25 suppressed FLS dysfunction in rats with AA, which were associated with reduced Ahr activation and the interaction between Ahr and GRK2.

Zhang BJ ，Wang YY ，Jia CY ，Li SS ，Wang XW ，Xu Y ，Chen AY ，Xu HP ，Wang C ，Yang ZY ，Wei W ，Chang Y ... -  《-》

Glycogen Metabolism and Rheumatoid Arthritis: The Role of Glycogen Synthase 1 in Regulation of Synovial Inflammation via Blocking AMP-Activated Protein Kinase Activation.

Shi M ，Wang J ，Xiao Y ，Wang C ，Qiu Q ，Lao M ，Yu Y ，Li Z ，Zhang H ，Ye Y ，Liang L ，Yang X ，Chen G ，Xu H ... -  《Frontiers in Immunology》

A novel function of artesunate on inhibiting migration and invasion of fibroblast-like synoviocytes from rheumatoid arthritis patients.

Ma JD ，Jing J ，Wang JW ，Yan T ，Li QH ，Mo YQ ，Zheng DH ，Gao JL ，Nguyen KA ，Dai L ... -  《-》