title: 17beta-estradiol downregulates interferon regulatory factor-1 in murine splenocytes.
abstract: Interferon regulatory factor-1 (IRF-1) is an important transcription factor that mediates interferon-gamma (IFN-gamma)-induced cell-signaling events. In this study, we examined whether 17beta-estradiol alters IRF-1 in splenic lymphocytes, in view of the immunomodulatory effects of this natural female sex hormone including its ability to alter IFN-gamma levels. We find that IRF-1 expression is markedly downregulated in splenocytes or purified T-cells from estrogen-treated mice at all time points studied when compared with their placebo counterparts. This decrease in IRF-1 in splenocytes from estrogen-treated mice is neither due to upregulation of IRF-1-interfering proteins (nucleophosmin or signal transducer and activator of transcription (STAT)-5) nor due to alternatively spliced IRF-1 mRNA. Given that IFN-gamma is a potent inducer of IRF-1, direct addition of recombinant IFN-gamma to splenocytes from either wild-type or IFN-gamma-knockout mice, or the addition of recombinant IFN-gamma to purified T-cells, was expected to stimulate IRF-1 expression. However, robust expression of IRF-1 in cells from estrogen-treated mice was not seen, unlike what was observed in cells from placebo-treated mice. Diminished IFN-gamma induction of IRF-1 in cells from estrogen-treated mice was noticed despite comparable phosphorylated STAT-1 activation. These studies are the first to show that estrogen regulates IFN-gamma-inducible IRF-1 in lymphoid cells, a finding that may have implications to IFN-gamma-regulated immune and vascular diseases.
authors.affiliation: Department of Biomedical Sciences and Pathology, Virginia-Maryland Regional College of Veterinary Medicine, 1410 Prices Fork Road, Blacksburg, VA 24061-0342, USA.
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Lengi
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Phillips
authors.forename: Ebru
authors.initials: E
authors.lastname: Karpuzoglu
authors.forename: Sattar Ansar
authors.initials: SA
authors.lastname: Ahmed
mesh_terms: D000818:Animals; D015536:Down-Regulation / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D005091:Exons / Q000235:genetics; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000378:metabolism*; D007371:Interferon-gamma / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D050794:STAT1 Transcription Factor / Q000378:metabolism; D013154:Spleen / Q000187:drug effects* / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D015854:Up-Regulation
chemical_list: D050856:Interferon Regulatory Factor-1; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D004958:Estradiol; D007371:Interferon-gamma