Mechanism of the 24-hour rhythm of tumor necrosis factor-alpha formed by onset of rheumatoid arthritis.

OBJECTIVE: Morning stiffness and plasma cytokine levels in rheumatoid arthritis (RA) patients exhibit 24-hour variations. Tumor necrosis factor-α (TNF-α) plays a central role in RA clinical conditions, including the invasion of inflammatory cells, destruction of cartilage, systemic inflammatory response and its levels show a 24-hour rhythm after the onset of RA. In this study, we investigated what cytokines and/or transcriptional factors are involved in the formation of 24-hour variations in TNF-α levels after the onset of RA using MRL/Mpj-Tnfrsf6(lpr) (MRL/lpr) mice. METHOD: Blood was drawn at six different times from MRL/lpr mice to measure cytokines, serum amyloid A (SAA), IgG rheumatoid factor (IgG-RF) and corticosterone levels. Cytokine and transcriptional factor levels at the different times were measured in 10- and/or 15-week-old MRL/lpr mice. The promoter activity of TNF-α by lymphotoxins (LTs) was investigated using a dual-luciferase assay. RESULTS: SAA and TNF-α concentrations clearly exhibited 24-hour rhythms with higher levels at the light phase and lower levels at the dark phase after RA crisis. The expression of LT-α and LT-ß showed significant 24-hour rhythms in 15-week-old MRL/lpr mice and the phases of LT-α and LT-ß levels were antiphase compared with that of TNF-α. AP-1 binding sites were found in LT-α and LT-ß promoter regions, and jun mRNA expression corresponded to LT-α and LT-ß levels. TNF-α promoter activity was decreased due to the co-transfection of LT-α and LT-ß. CONCLUSION: LT-α and LT-ß controls the 24-hour rhythm in TNF-α levels after the onset of RA in order to suppress TNF-α promoter activity.

High levels of Lymphotoxin-Beta (LT-Beta) gene expression in rheumatoid arthritis synovium: clinical and cytokine correlations.

Lymphotoxin-Beta (LT-Beta) is implicated in lymphoid follicle development, production of pro-inflammatory cytokines, and can enhance the proliferation of fibroblasts and synoviocytes. The objective of this study was to investigate LT-Beta and LT-BetaReceptor (LT-BetaR) gene expression in RA patient synovium and blood samples compared with control individuals, and correlate with LT-Alpha and TNF-Alpha gene expression and disease parameters. RT-PCR was used to investigate the gene expression of LT-Beta, LT-BetaR, TNF-Alpha and LT-Alpha in the blood and synovium of RA patients and a control group of individuals. LT-Beta gene expression was significantly higher in RA patient synovium compared to control synovium (P = 0.005). There was a significant positive correlation between LT-Beta and LT-Alpha gene expression in both the synovium (P = 0.001) and blood (P = 0.002) of RA patients. LT-Beta gene expression was significantly higher in RA patient synovial samples that were inflamed to a moderately severe degree compared to those inflamed to a minimal degree (P = 0.02). Analysis of clinical variables revealed a significant positive correlation between LT-BetaR gene expression in RA patient synovium and Pain VAS Score (P = 0.01) and also HAQ Score (P = 0.01). Increased LT-Beta gene expression occurs in RA synovium and correlates with the degree of inflammation. LT-Beta may play a role in RA disease pathogenesis by contributing to a more intense inflammatory reaction in the synovium.