Alteration of the cellular response to interleukin-1 beta by SV40 large T antigen in rheumatoid synovial fibroblasts

The large T antigen of SV40 (LT) has been widely used to immortalize primar y cells for various studies. In this study, synovial fibroblasts of a patie nt from rheumatoid arthritis (RA) were transformed with LT gene to analyze the effect of SV40-mediated transformation on the production of cytokines, such as IL-6, IL-8, and GM-CSF, that are under the control of interleukin-1 beta (IL-1 beta), a physiological inducer of nuclear factor kappa B (NF-ka ppa B). It was noted that the basal levels of GM-CSF and IL-8 were upregula ted, whereas that of IL-6 was downregulated. Moreover, the extents of induc tion of these cytokines in response to IL-1 beta were markedly downregulate d in synovial fibroblasts transformed by LT as compared from parental cells . Although IL-1 beta could translocate NF-kappa B to the nucleus in all cel ls, some of the transformed cells exhibited nuclear translocation of NF-kap pa B even before the stimulation with IL-1 beta, suggesting that transforma tion of LT resulted in the constitutive activation of NF-kappa B, either di rectly or indirectly. In order to examine whether LT downregulate the kappa B-dependent gene expression, we performed the transient luciferase gene ex pression assay. We found that cotransfection of LT did not downregulate the kappa B-dependent gene expression that was stimulated with L-1 beta. These observations suggest that the apparent inhibitory effect of LT on the IL-1 -induced expression of cytokines may not be through its direct action on th e NF-kappa B transactivation.