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Department of Biomedical Sciences

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https://hdl.handle.net/10217/100360
These digital collections include theses, dissertations, faculty publications, departmental publications, and datasets from the Department of Biomedical Sciences. Due to departmental name changes, materials from the following historical department are also included here: Physiology.

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Browsing Department of Biomedical Sciences by Subject "androgen"

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    Androgen signaling in the placenta
    (Colorado State University. Libraries, 2014) Cleys, Ellane Rachael, author; Bouma, Gerrit, advisor; Clay, Colin, advisor; Tobet, Stuart, committee member; Di Pietro, Santiago, committee member
    Placental estrogen signaling is known to regulate placental trophoblast function and differentiation. However, the role of placental androgen signaling has never been investigated, despite the rise of maternal serum androgens throughout gestation. Recent findings have shown increased maternal serum androgen in patients with the placental induced disorder preeclampsia. Preeclampsia, a maternal hypertension and proteinuria condition instigated by insufficient trophoblast differentiation and invasion into maternal spiral arteries, is also associated with increased placental expression of androgen receptor and an increased risk of incidence in patients with polymorphisms in androgen receptor that decrease androgen signaling. These findings suggest a crucial role for placental androgen signaling. Moreover, research investigating androgen's role in cancer progression has shown that many androgen responsive genes regulate cell proliferation, differentiation to invasive phenotypes, and tissue vascularization, all processes necessary for normal placental development. Androgen signaling in tumor tissues is further regulated by androgen receptor complexes with histone lysine demethylases. These complexes are recruited to androgen response elements in DNA and dynamically regulate histone tail modifications for transcription initiation. This led us to the overall hypothesis that (1) androgen signaling in trophoblast cells is important for placental development, and (2) androgen receptor complexes with histone lysine demethylases in the placenta to regulate vascularization, growth and invasion factors in trophoblast cells. To test this hypothesis, we utilized a prenatal androgenization ewe model as well as human first trimester placental samples and immortalized human trophoblast cell lines. Using the prenatal androgenized ewe model, we report for the first time expression of histone lysine demethylases in the placenta. Furthermore, we showed androgen receptor complexes with histone lysine demethylases and is recruited to an androgen response elements in the 5'untranslated flanking sequence of vascular endothelial growth factor in the sheep placenta. We also report that histone lysine demethylase are present in human first trimester syncytiotrophoblast and complex with androgen receptor in immortalized trophoblasts. Additionally, we demonstrated that androgen receptor complexes with histone lysine demethylases are also present in choriocarcinoma ACH-3P and BeWo cells. Dihydrotestosterone treatment in these cells led to down-regulation of androgen responsive genes, specifically KDM3A and MMP2. Inhibition of androgen receptor through flutamide treatment altered mRNA levels for genes regulating vascularization, including HIF1α, PPARα, and PPARy. Hypoxia also decreased CYP19 levels, however, further investigation is needed to confirm dihydrotestosterone and flutamide effect on protein expression in trophoblast cells. These data suggest that histone lysine demethylases complex with androgen receptor to regulate androgen responsive genes, including those directing placental vascularization and development. However, further experiments are needed to confirm the necessity of histone lysine demethylases for targeted androgen signaling in trophoblast cells and to determine if androgen directly regulates trophoblast differentiation and invasion. These findings suggest androgen signaling may play a critical role in placental development.
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    Dihydrotestosterone attenuates endotoxin, cytokine, and hypoxia-induced vascular inflammation
    (Colorado State University. Libraries, 2011) Osterlund, Kristen Leanne, author; Handa, Robert, advisor; Gonzales, Rayna, committee member; Amberg, Gregory, committee member; Garrity, Deborah, committee member; Tobet, Stuart, committee member
    Vascular inflammation plays a key role in the etiology of cardiovascular disease, particularly stoke. Vascular inflammation is under the control of several transcription factors, including nuclear factor kappa B and hypoxia inducible factor-1 alpha (HIF-1α). Activation of these transcription factors can lead to the production of inflammatory mediators such as cyclooxygenase-2 (COX-2). COX-2 plays a role in vascular inflammation, cerebral ischemia-induced injury, and has been implicated as a source of reactive oxygen species (ROS). Inflammatory mediators, such as endotoxin or cellular breakdown products released following injury, are known to signal through the Toll-like receptor 4 (TLR4). TLR4 activation leads to NFκB activation and subsequent production of COX-2. Like COX-2, TLR4 has also been implicated in injury-induced oxidative stress and cerebral ischemia damage. Previous studies have demonstrated that gonadal steroid hormones can also modulate vascular inflammation. Both protective and detrimental effects of androgens on the cardiovascular system have been reported. Since the potent androgen receptor (AR) agonist dihydrotestosterone (DHT) can be converted to 3β-diol, an estrogen receptor (ER) β-selective agonist, I hypothesized that ERβ may mediate some of the protective effects of androgens, while the AR may mediate some of the detrimental effects. The overall goal of this dissertation was to determine the mechanisms by which androgens can influence the vascular inflammatory response under both physiological and pathophysiological conditions. The hypothesis to be tested was that DHT influences vascular inflammation under both physiological and pathophysiological conditions. In my first set of experiments, using Western blot, I found that DHT increases expression of the vascular inflammatory mediator COX-2 under physiological conditions in human coronary artery vascular smooth muscle (VSM) cells and human brain VSM cells. This effect of DHT was attenuated in the presence of the AR antagonist bicalutamide. This data indicates that the pro-inflammatory effect of DHT under normal physiological conditions is AR mediated. In my second set of experiments, I examined the effects of DHT on vascular inflammation under a variety of pathophysiological conditions. Surprisingly, I found that DHT decreased cytokine-induced COX-2 expression and oxidative stress, endotoxin-induced COX-2 and TLR4 expression in human VSM cells. Furthermore, DHT also decreased hypoxia induced HIF-1α and COX-2 expression in human brain VSM cells and rat pial arteries. Finally, I found that DHT decreased hypoxia with glucose deprivation (HGD)-induced HIF-1α, COX-2 and TLR4 expression in human brain VSM cells. DHT`s anti-inflammatory effects during cytokine or HGD-induced inflammation in human brain VSM cells were not blocked by the AR antagonist bicalutamide, indicating that they were not AR mediated. These results led me to my second hypothesis, that DHT's anti-inflammatory effects are ERβ-mediated. In my third set of experiments, I found that the DHT metabolite/ERβ selective agonist 3β-diol also decreased cytokine-induced COX-2 expression in human brain VSM cells. Furthermore, DHT's ability to reduce cytokine-induced COX-2 expression in human brain VSM cells was inhibited by the non-selective estrogen receptor antagonist ICI 182,780 and the selective ERβ antagonist PHTPP. The mRNAs for steroid metabolizing enzymes in the pathway necessary to convert DHT to 3β-diol were detected in human brain VSM cells, as were AR and ERβ mRNAs. Therefore, DHT appears to be protective against cerebrovascular inflammation via conversion to 3β-diol and subsequent activation of ERβ in human brain VSM cells. The results of these studies indicate that: 1) DHT increases COX-2 expression under unstimulated/physiological conditions via an AR-dependent mechanism. 2) DHT decreases cytokine-, endotoxin,-hypoxia, and HGD-induced COX-2 expression via an AR-independent mechanism. 3) DHT decreases cytokine-induced reactive oxygen species. 4) DHT decreases hypoxia-induced HIF-1α expression. 5) DHT decreases HIF-1α and TLR4 expression during HGD via an AR-independent mechanism. 6) DHT's effect to attenuate cytokine-induced COX-2 expression is ERβ-mediated.