Stimulation of hyaluronan synthesis by tumor necrosis factor-alpha is mediated by the p50/p65 NF-kappa B complex in MRC-5 myofibroblasts

The lesions of fibrocontractive diseases result from an excessive myofibrop roliferative response to numerous forms of inflammatory stimuli, which elic it the net deposition of extracellular matrix (ECM) in the interstitium of the affected tissue. Hyaluronan (HA), reported to be a key player supportin g cellular migration and adherence,is a major component of ECM that undergo es dynamic regulation during inflammation. The molecular regulation of HA b iosynthesis by inflammatory cytokines on myofibroblasts is not yet complete ly understood. Here we report the biochemical characteristics of the lung m yofibroblast cell line MRC-5, and we demonstrate that the production of HA by this cell line is inducible by the proinflammatory cytokine, tumor necro sis factor-alpha (TNF-alpha), at the message level of HA synthase (HAS). In TNF-alpha-stimulated MRC-5 cells, DNA-binding and competition experiments indicated that the predominant NF-kappa B binding activity detected with nu clear extract-stimulated cells is mediated by the p50/p65 complex. Using an tisense oligonucleotides, we confirmed that the TNF-alpha-stimulation of HA synthesis by MRC-5 cells is dependent on the activation of the p50/p65 NF- kappa B complex. These findings indicate that TNF-alpha production within i nflamed tissues may enhance the HA synthesis via the transcriptional induct ion of HAS on myofibroblasts, thereby providing a provisional matrix for su pporting cellular migration and adhesion, and that the p50/p65 NF-kappa B c omplex that plays an important role in the regulation of HA. production by TNF-alpha might be an appropriate target for therapeutic compounds to treat tissue fibrosis accompanied by inflammation. (C) 1999 Elsevier Science B.V . All rights reserved.