BackgroundRheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs) actively drive joint inflammation and degradation by producing inflammatory cytokines and matrix-degrading molecules, making them key factors in the pathogenesis of RA. Cylindromatosis (CYLD) is a tumor suppressor that downregulates nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation by deubiquitinating NF-κB essential modulator and tumor necrosis factor receptor-associated factors 2 and 6. In this study, we aimed to determine CYLD expression in the synovium of patients with RA, analyze its correlation with NF-κB activation and clinical disease activity, further investigate CYLD expression in RA-FLSs, and explore CYLD’s roles and mechanisms in the pro-inflammatory effects, proliferation, apoptosis, and cell cycles of RA-FLSs.MethodsWe obtained synovia from 50 patients with active RA and 20 with osteoarthritis (OA) and then cultured FLSs from the samples. We determined CYLD expression in the synovia of RA patients and in FLSs via reverse transcription polymerase chain reaction (RT-PCR). CYLD was depleted by lentiviral CYLD short hairpin ribonucleic acid. We used RT-PCR and enzyme-linked immunosorbent assay to analyze the expression of pro-inflammatory cytokines, matrix metalloproteinases (MMPs), and receptor activator of nuclear factor kappa-B ligand (RANKL). We detected cell proliferation using Cell Counting Kit-8 and examined cell apoptosis and cell cycle using flow cytometry.ResultsWe obtained the following results:In synovia from patients with RA, CYLD expression was significantly downregulated while NF-κB expression was distinctly upregulated, compared with synovia from patients with OA. Thus, there is a significant inverse correlation between CYLD and NF-κB in synovia affected by RA.CYLD expression significantly decreased in RA-FLSs compared with OA-FLSs.CYLD suppression enhanced the production of pro-inflammatory cytokines, MMPs, and RANKL by activating NF-κB in RA-FLSs.CYLD suppression enhanced proliferation, reduced apoptosis, and increased cell division of RA-FLSs and aggravated the activity of NF-κB in RA-FLSs.ConclusionsVia its regulation of NF-κB activation, CYLD may be involved in the pathogenesis of synovial inflammation in RA as well as in the pro-inflammatory effects and hyperproliferation of RA-FLSs. CYLD may therefore provide a potential target for the treatment of RA.

Rheumatoid arthritis (RA) is characterized by chronic inflammatory synovitis resulting in progressive joint destruction. Persistent synovial inflammation is induced by activation of various inflammatory cells. G-protein-coupled bile acid receptor 1 (TGR5) is a G-protein-coupled receptor activated by various bile acids, which has been reported to act as a key adaptor in regulating various signaling pathways involved in inflammatory responses and a diverse array of physiological processes, including bile acid synthesis, lipid and carbohydrate metabolism, carcinogenesis, immunity and inflammation. In the present study, TGR5 expression was detected in RA peripheral blood mononuclear cells (PBMCs), and its association with clinical disease activity, histological synovitis severity and radiological joint destruction was analyzed. Subsequently, the role and potential underlying mechanisms of TGR5 in the PBMCs of patients with RA and mice with collagen II-induced arthritis (CIA) were investigated. PBMCs were obtained from 50 patients with RA and 40 healthy controls (HCs). The mRNA and protein expression levels of TGR5 were detected in PBMCs via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence staining, respectively. Additionally, the levels of proinflammatory cytokines were analyzed by RT-qPCR and enzyme-linked immunosorbent assay (ELISA). The activation of nuclear factor-κB (NF-κB) and IκB kinase a was determined via western blot analysis. The anti-arthritic and anti-inflammatory effects of LCA on mice with CIA were then investigated. The arthritis score was assessed, and the protein levels of proinflammatory cytokines in the plasma of mice were detected via ELISA. TGR5 mRNA expression was significantly downregulated in the PBMCs of patients with RA compared with in those of the HCs (0.53±0.58 for patients vs. 1.49±0.83 for HCs; P<0.001); similar findings were observed at the protein level. The mRNA expression levels of TGR5 in the PBMCs of patients with RA with a high 28-Joint Disease Activity Score (DAS28) were significantly decreased compared with in patients with a low DAS28 (0.81±0.65 for low score vs. 0.35±0.46 for high score; P=0.002). Furthermore, TGR5 expression was significantly correlated with the levels of C-reactive protein (r=−0.429; P=0.002) and the DAS28 (r=−0.383; P=0.006). RT-qPCR and ELISA analyses indicated that lithocholic acid (LCA, 10 mg/kg/day) attenuated lipopolysaccharide-induced proinflammatory cytokine production via inhibition of NF-κB activity in the PBMCs of patients with RA. In addition, the arthritis score was significantly decreased in LCA-treated CIA mice compared with in non-treated CIA mice. The increased production of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-8 was significantly reduced in the plasma of LCA-treated CIA mice compared with the control. In conclusion, TGR5 may contribute to the inflammation of PBMCs in patients with RA and mice with CIA.

Background: Current studies have limited data on long-term treatment safety and medication compliance of roxadustat for renal anemia in peritoneal dialysis (PD) patients. We aimed to analyze the long-term efficacy, safety, and medication compliance of roxadustat in the treatment of renal anemia in patients with PD who discontinued recombinant human erythropoietin (rhEPO) treatment due to the corona virus disease 2019 (COVID-19) outbreak.Methods: We retrospectively collected patients who were switched from rhEPO to roxadustat in our hospital due to the pandemic. The criteria for subject inclusion: aged >18 years with a dialysis vintage >3 months, without malignant tumor, no severe cardiovascular and cerebrovascular diseases, and not combined hemodialysis. Patients were followed up until the end of December 2021. Hemoglobin (Hb), red blood cell (RBC) and hematocrit (Hct) were recorded at baseline, month 1-12 and month 20, and iron parameters at baseline, 3, 6, 9, 12, and 20 months were collected. The Morisky Medication Adherence Scale-8 (MMAS-8) was used to score medication compliance during rhEPO treatment and roxadustat treatment, and adverse reactions occurred during treatment were collected. The efficacy and medication compliance of roxadustat were analyzed using Wilcoxon rank sum test or t-test.Results: The median follow-up time was 21.1 (20.6, 21.7) months. After 1 month of treatment, the Hb level was significantly increased by 9.4 g/L (95% CI: 6.0-12.8 g/L) compared with the baseline, follow up at 20 months showed the Hb level had remained stable, increased by 20.7 g/L (95% CI: 15.9-25.4 g/L) compared with before treatment. At the beginning of treatment, total iron binding capacity increased, transferrin saturation and serum ferritin decreased, serum iron remained stable during treatment. During roxadustat treatment, no patient discontinued treatment due to the pandemic, and the Morisky score was improved compared with that during rhEPO treatment [5.75 (4.25, 6.00) vs. 6.75 (5.75, 7.00), P=0.000].There were no serious adverse events associated with roxadustat were observed.Conclusions: Roxadustat can effectively improve anemia and had good tolerance in patients undergoing PD who have difficult using rhEPO, and the medication compliance was better than rhEPO during the COVID-19.