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.

Baseline anti-citrullinated peptide antibody (ACPA) titers and serum interleukin-6 (IL-6) levels possibly predict progression of bone destruction in early stages of rheumatoid arthritis (ERA).

A prospective study was made to seek for a convenient biomarker to predict progression of bone destruction (PBD) in early stages of rheumatoid arthritis (ERA). All participated patients had definite RA and their radiographic stages were mild less than stage II of the Steinbrocker classification, naïve for treatment of any DMARDs or corticosteroids. After the entry, they were treated according to the 2002 ACR management guideline for RA. The candidate biomarkers (RF-IgM, RF-IgG, CARF, ACPA, CRP, ESR, NTx, MMP-3, IL-6 and osteopontin) were measured at the entry. PBD was assessed radiographically by interval changes in the modified Sharp scores (ΔSHS) for 24 months. The associations between ΔSHS and baseline biomarkers were assessed statistically by multivariate regression analyses. Both the baseline ACPA and IL-6 levels correlated with PBD, suggesting that they could predict PBD in ERA.