Inhibition of major histocompatibility complex class II gene transcription by nitric oxide and antioxidants.
Interferon (IFN)-gamma facilitates cellular immune response, in part, by inducing the expression of major histocompatibility complex class II (MHC-II) molecules. We demonstrate that IFN-gamma induces the expression of HLA-DRA in vascular endothelial cells via mechanisms involving reactive oxygen species. IFN-gamma-induced HLA-DRA expression was inhibited by nitric oxide (NO) and antioxidants such as superoxide dismutase, catalase, pyrrolidine dithiocarbamate, and N-acetylcysteine. Nuclear run-on assays demonstrated that NO and antioxidants inhibited IFN-gamma-induced HLA-DRA gene transcription. Transient transfection studies using a fully functional HLA-DRA promoter construct ([-300]DR alpha.CAT) showed that inhibition of endogenous NO synthase activity by N(omega)-monomethyl-l-arginine or addition of exogenous hydrogen peroxide (H(2)O(2)) augmented basal and IFN-gamma-stimulated [-300]DR alpha.CAT activity. However, H(2)O(2) and N(omega)-monomethyl-l-arginine could induce HLA-DRA expression suggesting that H(2)O(2) is a necessary but not a sufficient mediator of IFN-gamma-induced HLA-DRA expression. Electrophoretic mobility shift assay and Western blotting demonstrated that NO and antioxidants had little or no effect on IFN-gamma-induced IRF-1 activation or MHC-II transactivator (CIITA) expression but did inhibit IFN-gamma-induced activation of STAT1 alpha (p91) and Y box transcription factors, NF-Y(A) and NF-Y(B). These results indicate that NO and antioxidants may attenuate vascular inflammation by antagonizing the effects of intracellular reactive oxygen species generation by IFN-gamma, which is necessary for MHC-II gene transcription.
Grimm
Michael
M
Vascular Medicine Unit, Brigham & Women's Hospital and Harvard Medical School, Boston, Masachusetts 02115, USA.
Spiecker
Martin
M
De Caterina
Raffaele
R
Shin
Wee Soo
WS
Liao
James K
JK
D000975:Antioxidants / Q000494:pharmacology*; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D005802:Genes, MHC Class II / Q000187:drug effects*; D006684:HLA-DR Antigens / Q000235:genetics; D059805:HLA-DR alpha-Chains; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection; D019323:omega-N-Methylarginine / Q000494:pharmacology
D000975:Antioxidants; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D006861:Hydrogen Peroxide