PLCL1 regulates fibroblast-like synoviocytes inflammation via NLRP3 inflammasomes in rheumatoid arthritis.

Phospholipase C-like 1 (PLCL1), a protein that lacks catalytic activity, has similar structures to the PLC family. The aim of this research was to find the function and underlying mechanisms of PLCL1 in fibroblast-like synoviocyte (FLS) of rheumatoid arthritis (RA). In this study, we first analyzed the expression of PLCL1 in the synovial tissue of RA patients and K/BxN mice by immunohistochemical staining. Then silencing or overexpressing PLCL1 in FLS before stimulating by TNF-α. The levels of IL-6, IL-1β and CXCL8 in FLS and supernatants were detected by Western Blot (WB), Real-Time Quantitative PCR and Enzyme Linked Immunosorbent Assay. We used INF39 to specifically inhibit the activation of NLRP3 inflammasomes, and detected the expression of NLRP3, Cleaved Caspase-1, IL-6 and IL-1β in FLS by WB. When PLCL1 was silenced, the level of IL-6, IL-1β and CXCL8 were down-regulated. When PLCL1 was overexpressed, the level of IL-6, IL-1β and CXCL8 were unregulated. The previous results demonstrated that the mechanism of PLCL1 regulating inflammation in FLS was related to NLRP3 inflammasomes. INF39 could counteract the release of inflammatory cytokines caused by overexpression of PLCL1. Result showed that the function of PLCL1 in RA FLS might be related to the NLRP3 inflammasomes. We finally confirmed our hypothesis with the NLRP3 inhibitor INF39. Our results suggested that PLCL1 might promote the inflammatory response of RA FLS by regulating the NLRP3 inflammasomes.

Luo S ，Li XF ，Yang YL ，Song B ，Wu S ，Niu XN ，Wu YY ，Shi W ，Huang C ，Li J ... -  《Advances in Rheumatology》

TNF-α/calreticulin dual signaling induced NLRP3 inflammasome activation associated with HuR nucleocytoplasmic shuttling in rheumatoid arthritis.

Liu Y ，Wei W ，Wang Y ，Wan C ，Bai Y ，Sun X ，Ma J ，Zheng F ... -  《-》

SMAD2 inhibits pyroptosis of fibroblast-like synoviocytes and secretion of inflammatory factors via the TGF-β pathway in rheumatoid arthritis.

Mao X ，Wu W ，Nan Y ，Sun W ，Wang Y ... -  《-》

Estradiol inhibits NLRP3 inflammasome in fibroblast-like synoviocytes activated by lipopolysaccharide and adenosine triphosphate.

Nucleotide binding domain and leucine-rich repeat pyrin 3 domain (NLRP3) inflammasome is known for activating pro-inflammatory cytokines in knee osteoarthritis (OA). This study was performed to identify whether NLRP3 inflammasome can be triggered by lipopolysaccharides (LPS) and adenosine triphos adenine (ATP), which are positively related with knee OA severity in joint-spaces, in human fibroblast-like synoviocytes (FLS), and to identify whether estrogen would inhibit the activation of NLRP3 inflammasome. In the present study, human FLS were isolated from the knee OA in patients during arthroplasty, and were treated with LPS and ATP in the presence or absence of estradiol (E2). The messenger RNA (mRNA) and protein levels of NLRP3 components were analyzed by real-time polymerase chain reaction and western blotting, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to examine interleukin (IL)-1β and IL-18 content in the supernatant. Estrogen receptor α inhibitor MPP and β inhibitor PHTPP were used to explore how E2 works. Our results demonstrated that treatment with LPS and ATP increased significantly both in mRNA and protein levels of all the NLRP3 inflammasome components, and triggered the NLRP3 inflammasome, followed by upregulated IL-1β and IL-18 in the cell supernatant. E2 appeared to inhibit the activation of NLRP3 inflammasome by diminishing mRNA and protein levels of NLRP3 through estrogen receptor β, and decreased the expression of IL-1β and IL-18 as well. These results suggested the increased LPS and ATP in joint-space may promote knee OA by NLRP3 inflammasome and E2 may exert a protective effect by inhibiting the activation of NLRP3 inflammasome in FLS.

Shi J ，Zhao W ，Ying H ，Zhang Y ，Du J ，Chen S ，Li J ，Shen B ... -  《-》

Taraxasterol suppresses inflammation in IL-1β-induced rheumatoid arthritis fibroblast-like synoviocytes and rheumatoid arthritis progression in mice.

Previous study has indicated that taraxasterol (TAR), one of bioactive pentacyclic triterpenes mainly isolated from Chinese medicine herb Taraxacum officinale, displays considerable anti-inflammatory effects in various kinds of models. However, its effects on rheumatoid arthritis (RA) have still not been elucidated. In this study, we aim to investigate its anti-inflammatory effects and underlying mechanisms of TAR against RA using both interleukin (IL)-1β-stimulated human fibroblast-like synoviocytes rheumatoid arthritis (HFLS-RA) in vitro and collagen-induced arthritis (CIA) mice in vivo. Firstly, our results demonstrated that TRA significantly suppressed the IL-1β-induced expressions of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), IL-6, and IL-8 and productions of matrix metalloproteinases (MMPs), like MMP-1 and MMP-3 in HFLS-RA in vitro. Moreover, TRA alleviated arthritis progressions and prevented inflammatory processes in the joint tissues of CIA mice in vivo. Further mechanism studies indicated that TRA blocked nuclear factor kappa B (NF-κB) activation via modulating inhibitor of kappa B (IκB), IκB kinase (IKK) and transforming growth factor-β-activated kinase 1 (TAK1). Results also demonstrated that TRA suppressed the NOD-like receptor protein 3 (NLRP3) inflammasomes through blocking expressions of NLRP3, apoptosis-associated speck-like protein containing (ASC), and caspase-1 in both IL-1β-induced HFLS-RA and CIA mice. In conclusions, current findings suggested that TRA might one of considerable therapeutic compounds for relieving rheumatoid arthritis progress via suppressing inflammations through modulating NF-κB and NLRP3 inflammasomes pathways.

Chen J ，Wu W ，Zhang M ，Chen C ... -  《-》