Browsing by Author "Phillips, Rebecca A."

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    Estrogen up-regulates inducible nitric oxide synthase, nitric oxide, and cyclooxygenase-2 in splenocytes activated with T cell stimulants: Role of interferon-gamma
    Karpuzoglu, Ebru; Fenaux, Jillian B.; Phillips, Rebecca A.; Lengi, Andrea J.; Elvinger, Francois; Ahmed, Sattar Ansar (Endocrine Society, 2006-02)
    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 IFN gamma. First, blocking costimulatory signals mediated through interactions of CD28 and B7 molecules by CTLA-4Ig markedly decreased not only IFN gamma but also nitric oxide. Second, estrogen treatment of IFN gamma-knockout (IFN gamma(-)/(-)) mice did not induce iNOS protein or nitric oxide. Finally, in vitro addition of recombinant IFN gamma to Con-A-activated splenocytes from IFN gamma((-)/(-)) mice induced iNOS protein primarily in estrogen-treated mice. Overall, this is the first report to show that estrogen treatment up-regulates IFN gamma-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.
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    Signal Transducer and Activation of Transcription (STAT) 4 beta, a Shorter Isoform of Interleukin-12-Induced STAT4, Is Preferentially Activated by Estrogen
    Karpuzoglu, Ebru; Phillips, Rebecca A.; Dai, Rujuan; Graniello, Carmine; Gogal, Robert M.; Ahmed, Sattar Ansar (Endocrine Society, 2009-03)
    Estrogen, a natural immunomodulatory compound, has been shown to promote the induction of a prototype T helper 1 cytokine, interferon (IFN)-gamma, as well as to up-regulate IFN gamma-mediated pro-inflammatory molecules (nitric oxide, cyclooxygenase 2, monocyte chemoattractant protein 1). Because IL-12 is a major IFN gamma-inducing cytokine, in this study we investigated whether estrogen treatment of wild-type C57BL/6 mice alters IL-12-mediated signaling pathways. A recent study has shown that IL-12 activates two isoforms of signal transducer and activation of transcription (STAT) 4, a normal-sized (full-length STAT4 alpha) and a truncated form (STAT4 beta). Interestingly, we found that estrogen treatment preferentially up-regulates the phosphorylation of STAT4 beta in splenic lymphoid cells. Time kinetic data showed the differential activation of STAT4 beta in splenic lymphoid cells from estrogen-treated mice, but not in cells from placebo controls. The activation of STAT4 beta was mediated by IL-12 and not IFN gamma because deliberate addition or neutralization of IL-12, but not IFN gamma, affected the activation of STAT4 beta. In contrast to IL-12-induced activation of STAT4 beta in cells from estrogen-treated mice, STAT4 beta was not increased, rather it tended to be decreased. In this context, STAT4 alpha-induced p27(kip1) protein was decreased in concanavalin A + IL-12-activated lymphocytes from estrogen-treated mice only. By using the in vitro DNA binding assay, we confirmed the ability of pSTAT4 beta to bind to the IFN gamma-activated sites (IFN gamma activation sequences)/STAT4-binding sites in estrogen-treated mice. Our data are the first to show that estrogen apparently has selective effects on IL-12-mediated signaling by preferentially activating STAT4 beta. These novel findings are likely to provide new knowledge with regard to estrogen regulation of inflammation. (Endocrinology 150: 1310-1320, 2009)