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Department of Biomedical Sciences and Pathology, Virginia-Maryland Regional College of Veterinary Medicine, Center for Molecular Medicine and Infectious Diseases, Virginia Polytechnic Institute and State University, 1410 Prices Fork Road, Blacksburg, Virginia 24061-0342, USA

(Requests for offprints should be addressed to S A Ahmed; Email: ansrahmd{at}vt.edu)

Interferon regulatory factor-1 (IRF-1) is an important transcription factor that mediates interferon- (IFN-)-induced cell-signaling events. In this study, we examined whether 17ß-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- 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- is a potent inducer of IRF-1, direct addition of recombinant IFN- to splenocytes from either wild-type or IFN--knockout mice, or the addition of recombinant IFN- 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- 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--inducible IRF-1 in lymphoid cells, a finding that may have implications to IFN--regulated immune and vascular diseases.

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				M. M. Joyce, R. C. Burghardt, R. D. Geisert, J. R. Burghardt, R. N. Hooper, J. W. Ross, M. D. Ashworth, and G. A. Johnson Pig Conceptuses Secrete Estrogen and Interferons to Differentially Regulate Uterine STAT1 in a Temporal and Cell Type-Specific Manner Endocrinology, September 1, 2007; 148(9): 4420 - 4431. [Abstract] [Full Text] [PDF]

				A. J. Lengi, R. A. Phillips, E. Karpuzoglu, and S. A. Ahmed Estrogen selectively regulates chemokines in murine splenocytes J. Leukoc. Biol., April 1, 2007; 81(4): 1065 - 1074. [Abstract] [Full Text] [PDF]