title: Estrogen up-regulates inducible nitric oxide synthase, nitric oxide, and cyclooxygenase-2 in splenocytes activated with T cell stimulants: role of interferon-gamma.
abstract: Estrogen is implicated in many autoimmune diseases and is a robust immunomodulator. For example, it regulates interferon (IFN)-gamma, a cytokine believed to up-regulate inducible nitric oxide synthase (iNOS). A notable gap in the literature is a lack of information on the regulation of nitric oxide in immune tissues by estrogen. We now show that activation of splenocytes with T cell stimulants [concanavalin-A (Con-A) or anti-CD3 antibodies] results in copious release of nitric oxide in splenocyte cultures from estrogen-treated but not placebo-treated mice. Moreover, even a low dose of T cell stimulants induced nitric oxide in splenocytes from estrogen-treated, but not placebo-treated, mice. Con-A-activated splenocytes from estrogen-treated mice also have up-regulated iNOS mRNA, iNOS protein, and cyclooxygenase-2 (a nitric oxide-regulated downstream proinflammatory protein) when compared with controls. Our studies suggest that the induction of nitric oxide by activated splenocytes from estrogen-treated mice is mediated in part by IFNgamma. First, blocking costimulatory signals mediated through interactions of CD28 and B7 molecules by CTLA-4Ig markedly decreased not only IFNgamma but also nitric oxide. Second, estrogen treatment of IFNgamma-knockout (IFNgamma(-)/(-)) mice did not induce iNOS protein or nitric oxide. Finally, in vitro addition of recombinant IFNgamma to Con-A-activated splenocytes from IFNgamma((-)/(-)) mice induced iNOS protein primarily in estrogen-treated mice. Overall, this is the first report to show that estrogen treatment up-regulates IFNgamma-inducible-iNOS gene expression, iNOS protein, nitric oxide, and cyclooxygenase-2 as an indirect consequence of activation of T cells. These findings may have wide implications to immunity and inflammatory disorders including female-predominant autoimmune diseases.
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, 24061, USA.
authors.forename: Ebru
authors.initials: E
authors.lastname: Karpuzoglu
authors.forename: Jillian B
authors.initials: JB
authors.lastname: Fenaux
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Phillips
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Lengi
authors.forename: François
authors.initials: F
authors.lastname: Elvinger
authors.forename: S
authors.initials: S
authors.lastname: Ansar Ahmed
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000502:physiology; D018106:CD28 Antigens / Q000502:physiology; D051546:Cyclooxygenase 2 / Q000096:biosynthesis / Q000378:metabolism*; D004790:Enzyme Induction; D004958:Estradiol / Q000502:physiology*; D004967:Estrogens / Q000494:pharmacology; D007371:Interferon-gamma / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D013154:Spleen / Q000166:cytology / Q000201:enzymology*; D013601:T-Lymphocytes / Q000276:immunology*; D015854:Up-Regulation
chemical_list: D018122:B7-1 Antigen; D018106:CD28 Antigens; D004967:Estrogens; D012333:RNA, Messenger; D009569:Nitric Oxide; D004958:Estradiol; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2