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

Summary

The large T antigen of SV40 (LT) has been widely used to immortalize primary cells for various studies. In this study, synovial fibroblasts of a patient 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-1β (IL-1β), a physiological inducer of nuclear factor κB (NF-κB). It was noted that the basal levels of GM-CSF and IL-8 were upregulated, whereas that of IL-6 was downregulated. Moreover, the extents of induction of these cytokines in response to IL-1β were markedly downregulated in synovial fibroblasts transformed by LT as compared from parental cells. Although IL-1β could translocate NF-κB to the nucleus in all cells, some of the transformed cells exhibited nuclear translocation of NF-κB even before the stimulation with IL-1β, suggesting that transformation of LT resulted in the constitutive activation of NF-κB, either directly or indirectly. In order to examine whether LT downregulate the κB-dependent gene expression, we performed the transient luciferase gene expression assay. We found that co-transfection of LT did not downregulate the κB-dependent gene expression that was stimulated with L-1β. 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 the NF-κB transactivation.