ALKBH5-Mediated RNA m(6) A Methylation Regulates the Migration, Invasion, and Proliferation of Rheumatoid Fibroblast-Like Synoviocytes.

Fibroblast-like synoviocytes (FLSs) are critical for promoting joint damage in rheumatoid arthritis (RA). N6 -methyladenosine (m6 A) modification plays key roles in various diseases, but its role in the pathogenesis of RA is largely unknown. Here, we investigate increased demethylase ALKBH5 promotion of proliferation, migration, and invasion of RA FLSs via regulating JARID2 expression. ALKBH5 expression in FLSs was evaluated using real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot. 5-ethynyl-2'-deoxyuridine, scratch wound healing, and transwell assays were implemented to determine the role of ALKBH5 on RA FLS proliferation, mobility, and migration. Then, m6 A sequencing combined with RNA sequencing was performed to identify the potential targets of ALKBH5. RNA immunoprecipitation and RNA pulldown were then used to validate the interaction between the protein and messenger RNA (mRNA). Collagen-induced arthritis (CIA) and delayed-type hypersensitivity arthritis (DTHA) models were further established to assess the therapeutic potency of ALKBH5 in vivo. We demonstrated that ALKBH5 expression was increased in FLSs and synovium from RA. Functionally, ALKBH5 knockdown inhibited the proliferation, migration, and invasion of RA FLSs, whereas overexpression of ALKBH5 displayed the opposite effect. Mechanistically, ALKBH5 mediated m6 A modification in the JARID2 mRNA and enhanced its mRNA stability in cooperation with IGF2BP3. Intriguingly, the severity of arthritis was attenuated in mice with DTHA and ALKBH5 knockout or rats with CIA and intra-articular injection of ALKBH5 short hairpin RNA. Our findings suggest that ALKBH5-mediated m6 A modification is crucial for synovial hyperplasia and invasion in RA. ALKBH5 might be a potential therapeutic target for RA and even for dysregulated fibroblasts in a wide range of diseases.

Kuang Y ，Li R ，Wang J ，Xu S ，Qiu Q ，Lin S ，Liu D ，Shen C ，Liu Y ，Xu M ，Lin W ，Zhang S ，Liang L ，Xu H ，Xiao Y ... -  《-》

NAT10 promotes synovial aggression by increasing the stability and translation of N4-acetylated PTX3 mRNA in rheumatoid arthritis.

Recent studies indicate that N-acetyltransferase 10 (NAT10)-mediated ac4C modification plays unique roles in tumour metastasis and immune infiltration. This study aimed to uncover the role of NAT10-mediated ac4C in fibroblast-like synoviocytes (FLSs) functions and synovial immune cell infiltration in rheumatoid arthritis (RA). FLSs were obtained from active established patients with RA. Protein expression was determined by western blotting or immunohistochemistry or multiplexed immunohistochemistry. Cell migration was measured using a Boyden chamber. ac4C-RIP-seq combined with RNA-seq was performed to identify potential targets of NAT10. RNA immunoprecipitation was used to validate the interaction between protein and mRNA. NAT10 haploinsufficiency, inhibitor remodelin or intra-articular Adv-NAT10 was used to suppress arthritis in mice with delayed-type hypersensitivity arthritis (DYHA) and collagen II-induced arthritis (CIA) and rats with CIA. We found elevated levels of NAT10 and ac4C in FLSs and synovium from patients with RA. NAT10 knockdown or specific inhibitor treatment reduced the migration and invasion of RA FLSs. Increased NAT10 level in the synovium was positively correlated with synovial infiltration of multiple types of immune cells. NAT10 inhibition in vivo attenuated the severity of arthritis in mice with CIA and DTHA, and rats with CIA. Mechanistically, we explored that NAT10 regulated RA FLS functions by promoting stability and translation efficiency of N4-acetylated PTX3 mRNA. PTX3 also regulated RA FLS aggression and is associated with synovial immune cell infiltration. Our findings uncover the important roles of NAT10-mediated ac4C modification in promoting rheumatoid synovial aggression and inflammation, indicating that NAT10 may be a potential target for the treatment of RA, even other dysregulated FLSs-associated disorders.

Liu D ，Kuang Y ，Chen S ，Li R ，Su F ，Zhang S ，Qiu Q ，Lin S ，Shen C ，Liu Y ，Liang L ，Wang J ，Xu H ，Xiao Y ... -  《-》

Ferroportin inhibits the proliferation and migration of fibroblast-like synoviocytes in rheumatoid arthritis via regulating ROS/PI3K/AKT signaling pathway.

The aberrant proliferation of fibroblast-like synoviocytes (FLS) significantly contributes to excessive synovial hyperplasia and joint deformity in rheumatoid arthritis (RA). It has been observed that the membrane iron transporter protein, ferroportin (FPN), is commonly downregulated in tumor cells, while its overexpression can inhibit tumor cell proliferation. However, limited studies have investigated the role of iron in the pathogenesis of RA. In this study, we examined the functional relevance of FPN in RA. The expression of FPN in RA tissue specimens and primary cells was assessed using western blotting and RT-PCR. An adjuvant-induced arthritis (AIA) rat model was established to further validate the expression level of FPN. Phenotypic analysis of FLS cell proliferation was performed via CCK-8, clonogenic formation, and cell scratch assays. The involvement of membrane iron transporter proteins was analyzed through RNAseq and reactive oxygen species (ROS) detection. The results demonstrated decreased expression of FPN in the synovial tissue of RA patients compared to the normal group. Overexpression of FPN can inhibit RA-FLS proliferation and migration by suppressing the PI3K/AKT pathway, and this effect is associated with the elevation of ROS levels. Our findings suggest that the downregulation of FPN may contribute to the pathogenesis of RA, indicating a potential role of iron dysregulation in this disease, and FPN regulates the proliferation and migration of FLS by promoting the levels of ROS in FLS as well as suppressing the PI3K/AKT signaling pathway. These results suggest that FPN could be a potential target for alleviating joint damage in RA.

Shao W ，Liu F ，Zhu L ，Qian W ，Meng Q ，Zhang A ，Jin S ，Lu J ，Yan SG ... -  《-》

Syringin inhibits the crosstalk between macrophages and fibroblast-like synoviocytes to treat rheumatoid arthritis via PDE4.

Syringin (SRG) is well-known for its anti-inflammatory effects. However, its pharmacological mechanisms against rheumatoid arthritis (RA) are not fully understood. We assessed the anti-RA effects of SRG using a collagen-induced arthritis (CIA) rat model. And, we employed single-cell RNA sequencing (scRNA-seq) to analyze the changes in cell types and gene expression in the synovial tissues. Building on these observations, we investigated the effects of SRG on M1 macrophage polarization and RA-fibroblast-like synoviocytes (FLS) proliferation. Our findings highlighted the anti-RA effects of SRG on CIA rat. scRNA-seq of rat synovial tissues revealed significant changes in M1 and RA-FLS. Specifically, SRG decreased the levels of inflammatory factors in the supernatants of LPS and IFN-γ induced THP-1 cells and downregulated M1-polarized markers in these cells. Further analysis indicated that SRG's regulation of phosphodiesterase 4 (PDE4) and its associated factors was crucial for its anti-M1 polarization effects. Besides, we found that SRG inhibited the activation of FLS in vivo but showed no direct effects on RA-FLS in vitro. However, in RA-FLS, co-cultured with supernatant from SRG-treated M1-polarized THP-1 cells exhibited lower ability of cell proliferation and activation as compared to co-cultured with supernatant from M1-polarized THP-1 cells. By integrating scRNA-seq analysis with in vivo and in vitro validations, our study revealed that SRG achieved its anti-RA effects by blocking the interaction between macrophages and RA-FLS, with PDE4 playing a central role. This study may provide a novel research paradigm in studying the multi-cell regulatory mechanisms of natural compounds.

Cong S ，Wang N ，Pei H ，Li Z ，Meng Y ，Maimaitituersun S ，Zhao X ，Wan R ，Wan Q ，Luo L ，Bian Y ，Wen W ，Cui H ... -  《-》

m(6)A-mediated lncRNA MAPKAPK5-AS1 induces apoptosis and suppresses inflammation via regulating miR-146a-3p/SIRT1/NF-κB axis in rheumatoid arthritis.

Wen J ，Liu J ，Wan L ，Jiang H ，Xin L ，Sun Y ，Fang Y ，Wang X ，Wang J ... -  《-》