Short-term hyperthermia prevents activation of proinflammatory genes in fibroblast-like synoviocytes by blocking the activation of the transcription factor NF-kappaB.

Fibroblast-like synoviocytes (FLS) play a key role in the genesis of rheumatoid arthritis (RA). FLS are among the most versatile cells with the potential to activate an array of genes that are able to initiate and propagate inflammation in RA-affected joints. Controlling activation of FLS might hold the key to restraining inflammation in RA-affected joints. In this study, we investigate the effect and mechanisms of short-term hyperthermia on a series of proinflammatory genes in FLS. In vitro experiments demonstrate that exposure of FLS to elevated temperatures for the duration of 30 min prevents activation of a series of genes with proinflammatory properties. Exposure to hyperthermia reduces IL-1beta-induced prostaglandin E2 release, suppresses activation of the adhesion molecules VCAM-1, ICAM-1, the cytokines TNFalpha, IL-1alpha, IL-1beta, IL-8 as well as COX-2 protein synthesis. Real time reverse transcriptase-polymerase chain reaction showed that hyperthermia altered gene expression at the transcriptional level. The amount and the duration of inhibition is gene-specific and lasts for up to 25 h. As to the mechanism of inhibition, electrophoretic mobility shift assay experiments demonstrated that exposure of FLS to hyperthermia prevents IL-1beta-induced NF-kappaB translocation and subsequent DNA binding. Many mechanisms have been shown to be involved in hyperthermia-mediated effects on NF-kappaB-DNA interactions. We demonstrate by Western blot experiments that in FLS, hyperthermia prevents the phosphorylation and subsequent degradation of IkappaBalpha, therefore retaining the NF-kappaB complex in the cytoplasm. Carefully controlled in vivo tests are certainly needed before one can take full advantage of those phenomena; however, the ease by which the temperature in joints can be modulated might offer an opportunity for manipulating inflammatory processes in joints by simple balneological means.