Modulation of TNFR 1-triggered two opposing signals for inflammation and apoptosis via RIPK 1 disruption by geldanamycin in rheumatoid arthritis.

OBJECTIVES: To evaluate the ability of geldanamycin to modulate two opposing TNFα/TNFR1-triggered signals for inflammation and cell death. METHODS: The effects of geldanamycin on TNFα-induced proinflammatory cytokine production, apoptosis, NF-κB activation, caspase activation, and necroptosis in a human rheumatoid synovial cell line (MH7A) were evaluated via ELISA/qPCR, flow cytometry, dual-luciferase reporter assay, and western blotting assay, respectively. In addition, therapeutic effects on murine collagen-induced arthritis (CIA) were also evaluated. RESULTS: Geldanamycin disrupted RIPK1 in MH7A, thereby inhibiting TNFα-induced proinflammatory cytokine production and enhancing apoptosis. TNFα-induced NF-κB and MLKL activation was inhibited, whereas caspase 8 activation was enhanced. Recombinant RIPK1 restored the geldanamycin-mediated inhibition of TNFα-induced NF-κB activation. In addition, GM showed more clinical effectiveness than a conventional biologic TNF inhibitor, etanercept, in murine CIA and significantly attenuated synovial hyperplasia, a histopathological hallmark of RA. CONCLUSIONS: GM disrupts RIPK1 and selectively inhibits the TNFR1-triggered NF-κB activation signaling pathway, while enhancing the apoptosis signaling pathway upon TNFα stimulation, thereby redressing the balance between these two opposing signals in a human rheumatoid synovial cell line. Therapeutic targeting RIPK1 may be a novel concept which involves TNF inhibitor acting as a TNFR1-signal modulator and have great potential for a more fundamental, effective, and safer TNF inhibitor. Key Points • Geldanamycin (GM) disrupts RIPK1 and selectively inhibits the TNFR1-triggered NF-κB activation signaling pathway while enhancing the apoptosis signaling pathway upon TNFα stimulation, thereby redressing the balance between these two opposing signals in a human rheumatoid synovial cell line, MH7A. • GM showed more clinical effectiveness than a conventional biologic TNF-inhibitor, etanercept, in murine collagen-induced arthritis (CIA), and significantly attenuated synovial hyperplasia, a histopathological hallmark of RA. • Therapeutic targeting RIPK1 may be a novel concept which involves TNF inhibitor acting as a TNFR1-signal modulator and have great potential for a more fundamental, effective, and safer TNF-inhibitor.

Crosstalk between tumor necrosis factor-alpha signaling and aryl hydrocarbon receptor signaling in nuclear factor -kappa B activation: A possible molecular mechanism underlying the reduced efficacy of TNF-inhibitors in rheumatoid arthritis by smoking.

OBJECTIVES: To examine the influence of smoking on biologics treatment against different therapeutic targets, such as TNFα, IL-6, and T cell, in rheumatoid arthritis (RA) and elucidate the underlying molecular mechanism. METHODS: The association between drug-discontinuation due to poor therapeutic response and smoking status was analyzed individually in biologics against different therapeutic targets by a multivariable logistic regression analysis using the "NinJa" Registry, one of the largest cohorts of Japanese RA patients. In vitro enhancement of TNFα-induced NF-κB activation and subsequent proinflammatory cytokine production by cigarette chemical components was examined by RT-PCR, qPCR, ELISA, and western blotting using an immortalized rheumatoid synovial cell line, MH7A. RESULTS: The rate of drug-discontinuation due to poor therapeutic response was higher in the current smoking group than in the never- or ever-smoking groups (the odds ratio of current/never smoking: 2.189, 95%CI; 1.305-3.672,P = 0.003; current/ever: 1.580, 95%CI; 0.879-2.839,P = 0.126) in the TNF inhibitor (TNFi) treatment group. However, this tendency was not observed in either the IL-6 or T cell inhibitor treatment groups. Cigarette smoke chemical components, such as benzo[α]pyrene, known as aryl hydrocarbon receptor (AhR) ligands, themselves activated NF-κB and induced proinflammatory cytokines, IL-1ß and IL-6. Furthermore, they also significantly enhanced TNFα-induced NF-κB activation and proinflammatory cytokine production. This enhancement was dominantly inhibited by Bay 11-7082, an NF-κB inhibitor. CONCLUSIONS: These results suggest a crosstalk between TNFα signaling and AhR signaling in NF-κB activation which may constitute one of the molecular mechanisms underlying the higher incidence of drug-discontinuation in RA patients undergoing TNFi treatment with smoking habits.