Oxidants selectively reverse TGF-beta suppression of proinflammatory mediator production
Xiao, Y.Qun.; Freire-de-Lima, C.G.; Janssen, W.J.; Morimoto, K.; Lyu, D.; Bratton, D.L.; Henson, P.M.
Journal of Immunology 176(2): 1209-1217
2006
ISSN/ISBN: 0022-1767 PMID: 16394011 Document Number: 597702
Although TGF-beta inhibits the production of proinflammatory mediators in vitro and in vivo, its anti-inflammatory activities may be ineffective in early or severe acute inflammatory circumstances. In this study, we suggest a role for oxidative stress on TGF-beta signaling, leading to prevention of its normal anti-inflammatory effects but leaving its Smad-driven effects on cellular differentiation or matrix production unaffected. Stimulation of the RAW 264.7 macrophage cells, human or mouse alveolar macrophages with LPS led to NF-kappa B-driven production of proinflammatory mediators, which were inhibited by TGF-beta. This inhibition was prevented in the presence of hydrogen peroxide. We found that hydrogen peroxide acted by inducing p38 MAPK activation, which then prevented the ERK activation and MAPK phosphatase-1 up-regulation normally induced by TGF-beta. This was mediated through Src tyrosine kinases and protein phosphatase-1/2A. By contrast, hydrogen peroxide had no effects on TGF-beta-induced Smad2 phosphorylation and SBE-luc reporter gene transcription.