Objective: Interferon-gamma (IFN-γ) is overexpressed in rheumatoid synovium and thought to be involved in the pathogenesis of rheumatoid arthritis (RA). In this study, we examined our hypothesis that IFN-γ activates innate immune cells and upregulates inflammatory cytokines. Peripheral blood neutrophils were stimulated with IFN-γ in the presence or absence of Janus kinase (JAK) inhibitors. Interleukin-6 (IL-6) mRNA and protein expression were analyzed using real-time polymerase chain reaction (PCR) method and enzyme-linked immunosorbent assay. Protein phosphorylation of JAKs or STAT1 was assessed by Western blot using phospho-specific antibodies. Results: IFN-γ stimulation induces IL-6 expression in protein and mRNA levels in human neutrophils. Furthermore, IFN-γ stimulation induces JAK1/JAK2 phosphorylation and downstream signal transducer and activator of transcription (STAT) 1 phosphorylation in human neutrophils. Although all JAKi, blocked IFN-γ-induced JAK1.2/STAT1 phosphorylation at higher concentrations (100 nM), baricitinib most efficiently inhibited IFN-γ-induced JAK1.2/STAT1 phosphorylation at lower concentrations (≤ 25 nM). Among these JAKi, baricitinib was the most potent regulator for IFN-γ-induced IL-6 production in human neutrophils. Our data indicate that IFN-γ upregulates IL-6 production via the JAK1/2-STAT1 pathway in human innate immune cells. Furthermore, this IFN-γ-mediated IL-6 induction via JAK/STAT was downregulated by JAKi.

Background: Anti-citrullinated peptide antibodies (ACPA) and inflammatory cytokines play important roles in the development of rheumatoid arthritis (RA). T cell immunoglobulin and mucin–domain containing–3 (TIM–3) is an immune-checkpoint molecule involved in inhibitory signaling. Galectin–9 (Gal–9) mediated ligation of TIM–3 induces the amelioration of autoimmune diseases. TIM–3 is expressed in synovial osteoclasts and involved in the rheumatoid bone destruction. The aim of this study was to investigate the relationships between inflammatory cytokines and immune–checkpoint molecules in RA patients.Methods: Serum levels of interleukin–6 (IL–6), tumor necrosis factor–α (TNF–α), soluble TIM–3 (sTIM–3) and Gal–9 were determined by ELISA. Patients were stratified into two groups based on ACPA titers: low-medium ACPA (ACPA <200 U/mL) and high ACPA (ACPA ≥200 U/mL). Serum levels of cytokines or immune-checkpoint molecules were evaluated between RA patients with low-medium ACPA titers and high ACPA titers.Results: Elevated serum levels of inflammatory cytokines were correlated with DAS28–ESR in RA patients. Although serum levels of sTIM–3 were elevated in RA patients, significant correlations between sTIM–3 and cytokines (IL–6 or TNF–α) were observed exclusively in RA patients with low-medium ACPA titers (<200 U/mL). Serum levels of IL–6 and TNF–α levels were significantly correlated with elevated Gal–9 levels regardless of ACPA status. A significant correlation between IL–6 and Gal–9 was observed in RA patients without advanced joint damage. Conversely, a significant correlation between TNF–α and Gal–9 was observed in RA patients with advanced joint damage.Conclusions: Our data indicated that there are positive correlations between circulating inflammatory cytokines and checkpoint molecules in RA patients and these interactions can be modulated by ACPA status or joint damage stage.

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by synovitis, bone and cartilage destruction, and increased fracture risk with bone loss. Although disease–modifying antirheumatic drugs have dramatically improved clinical outcomes, these therapies are not universally effective in all patients because of the heterogeneity of RA pathogenesis. Therefore, it is necessary to elucidate the molecular mechanisms underlying RA pathogenesis, including associated bone loss, in order to identify novel therapeutic targets. In this study, we found that Budding uninhibited by benzimidazoles 1 (BUB1) was highly expressed in RA patients’ synovium and murine ankle tissue with arthritis. As CD45⁺CD11b⁺ myeloid cells are a Bub1 highly expressing population among synovial cells in mice, myeloid cell–specific Bub1 conditional knockout (Bub1^ΔLysM) mice were generated. Bub1^ΔLysM mice exhibited reduced femoral bone mineral density when compared with control (Ctrl) mice under K/BxN serum–transfer arthritis, with no significant differences in joint inflammation or bone erosion based on a semi–quantitative erosion score and histological analysis. Bone histomorphometry revealed that femoral bone mass of Bub1^ΔLysM under arthritis was reduced by increased osteoclastic bone resorption. RNA-seq and subsequent Gene Set Enrichment Analysis demonstrated a significantly enriched nuclear factor-kappa B pathway among upregulated genes in receptor activator of nuclear factor kappa B ligand (RANKL)–stimulated bone marrow–derived macrophages (BMMs) obtained from Bub1^ΔLysM mice. Indeed, osteoclastogenesis using BMMs derived from Bub1^ΔLysM was enhanced by RANKL and tumor necrosis factor-α or RANKL and IL-1β treatment compared with Ctrl. Finally, osteoclastogenesis was increased by Bub1 inhibitor BAY1816032 treatment in BMMs derived from wildtype mice. These data suggest that Bub1 expressed in macrophages plays a protective role against inflammatory arthritis–associated bone loss through inhibition of inflammation–mediated osteoclastogenesis. Rheumatoid arthritis (RA) is a disease caused by an abnormal immune system, resulting in inflammation, swelling, and bone destruction in the joints, along with systemic bone loss. While new medications have dramatically improved treatment efficacy, these therapies are not universally effective for all patients. Therefore, we need to understand the regulatory mechanisms behind RA, including associated bone loss, to develop better therapies. In this study, we found that Budding uninhibited by benzimidazoles 1 (Bub1) was highly expressed in inflamed joints, especially in myeloid cells, which are a type of immune cells. To explore its role, we created myeloid cell–specific Bub1 conditional knockout (cKO) mice and induced arthritis to analyze its role during arthritis. The cKO mice exhibited lower bone mineral density when compared with control mice under inflammatory arthritis because of increased osteoclastic bone resorption, without significant differences in joint inflammation or bone erosion. Further investigation showed that Bub1 prevents excessive osteoclast differentiation induced by inflammation in bone marrow macrophages. These data suggest that Bub1 in macrophages protects against bone loss caused by inflammatory arthritis, offering potential insights for developing treatments that focus on bone health.

This study evaluated the real-world effectiveness of belimumab (BLM) in the treatment of systemic lupus erythematosus (SLE) patients with moderate to high disease activity. This retrospective cohort study enrolled 129 Japanese patients with moderate to high SLE disease activity who received BLM between January 2013 and March 2023. The clinical outcomes, including the flare-free survival, SLE Disease Activity Index 2000 (SLEDAI-2K) score, and prednisone-equivalent dose, in the BLM and mycophenolate mofetil (MMF) treatment groups were compared before and after treatment. Safety data for BLM were collected. Additionally, we compared the effectiveness of BLM and intravenous cyclophosphamide (IV-CY) treatment using the stabilized inverse probability of treatment weighting (IPTW) method based on the propensity scores. This observational study enrolled 129 patients with moderate/severe SLE: 48 patients received belimumab, 45 received IV-CY, and 36 received MMF and prednisolone for remission induction therapy. The median follow-up for the BLM group was 17.0 months. Among them, 19 received BLM plus MMF. BLM significantly reduced the mean SLEDAI-2K (from mean baseline to 52 weeks: 49.2% reduction from 12.8 to 6.5) and prednisone daily dose (from mean baseline to 52 weeks: 21.9% reduction from 12.8 to 10.0 mg/day). The flare-free survival at 52 weeks was not significantly different between the BLM and MMF groups. There was no significant difference in the flare-free survival rates or reduction rates of the SLEDAI-2K between the patients treated with BLM and those treated with BLM plus MMF. In the propensity score-matched comparative analyses, there was no significant difference in the flare-free survival rates or an estimated decline in the SLEDAI-2K scores between the patients with lupus treated with BLM and IV-CY. BLM may be a promising alternative treatment option for lupus patients with moderate or high disease activity who do not respond to conventional treatments.

In this retrospective cohort study, we compared the retention rates and effectiveness of biologic disease modifying antirheumatic drugs (bDMARDs) and targeted synthetic DMARDs (targeted disease modifying antirheumatic drug [tsDMARDs]: Janus kinase inhibitors [JAKi]) in elderly patients with RA. One hundred thirty-four elderly RA patients (≥65 years) who were initiated with bDMARDs (n = 80) or JAKi (n = 54) between 2016 and 2020 in our institute were enrolled in this analysis. Follow-up was conducted at 4-week intervals from the start of bDMARDs or JAKi. We compared the drug retention and clinical response at 24 week between elderly RA patients treated with bDMARDs and JAKi. In the demographic data, more disease duration, the proportion of previous bDMARDs use and less the proportion of glucocorticoid use in JAKi group was significantly observed compared to the bDMARDs group. Otherwise, there was no significant difference in the other variables between the bDMARDs and JAKi groups. In the JAKi group, drug retention rate was not significantly different compared to the bDMARDs group (HR: 0.723, 95% CI: 0.406–1.289, P = .266). Also, there was no significant difference in the proportion of patients achieving good or moderate European alliance of associations for rheumatology (EULAR) response at 24 week between these two groups (bDMARDs; 88.6% vs JAKi; 91.8%, P = .158). In elderly RA patients initiated with bDMARDs or JAKi, drug retention rates of these targeted therapies did not differ significantly between these two groups. These findings suggest that elderly RA patients can achieve similar clinical improvement after initiating bDMARDs or JAKi.