Simvastatin inhibits IFN-gamma-induced CD40 gene expression by suppressing STAT-1alpha.
CD40, a member of the TNF receptor superfamily, is critical for productive immune responses. Macrophages constitutively express CD40 at low levels, which are enhanced by IFN-gamma. IFN-gamma-induced CD40 expression involves activation of STAT-1alpha as well as NF-kappaB activation through an autocrine response to IFN-gamma-induced TNF-alpha production. Statins are 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors, which exert anti-inflammatory effects independent of their cholesterol-lowering actions. Herein, we describe that simvastatin (SS) inhibits IFN-gamma-induced CD40 expression via the suppression of STAT-1alpha expression. This results in diminished STAT-1alpha recruitment to the CD40 promoter upon IFN-gamma treatment, in addition to reduced RNA Polymerase II recruitment and diminished levels of H3 and H4 histone acetylation. SS-mediated inhibition of STAT-1alpha occurs through suppression of constitutive STAT-1alpha mRNA and protein expression. The inhibitory effect of SS on CD40 and STAT-1alpha is dependent on HMG-CoA reductase activity, as the addition of mevalonate reverses the inhibitory effect. In addition, CD40 and/or STAT-1alpha expression is inhibited by GGTI-298 or Clostridium difficile Toxin A, a specific inhibitor of Rho family protein prenylation, indicating the involvement of small GTP-binding proteins in this process. Collectively, these data indicate that SS inhibits IFN-gamma-induced CD40 expression by suppression of STAT-1alpha, and altering transcriptional events at the CD40 promoter.
Lee
Sun Jung
SJ
Department of Cell Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294-0005, USA.
Qin
Hongwei
H
Benveniste
Etty N
EN
D000818:Animals; D019013:CD40 Antigens / Q000037:antagonists & inhibitors* / Q000235:genetics*; D002460:Cell Line; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D051379:Mice; D050794:STAT1 Transcription Factor / Q000037:antagonists & inhibitors*; D019821:Simvastatin / Q000494:pharmacology*
D019013:CD40 Antigens; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D007371:Interferon-gamma; D019821:Simvastatin