Browsing by Subject "estrogen"
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Item 17 Beta-Estradiol, Integrins, and Synaptic Proteins(2009-05-01) Chandra, Manjari; Simpkins, James W.Item Connexin 43 Contributes to Estrogen Protection against Oxidative Stress in Cortical Astrocytes(2019-05) Kubelka, Nicholas K.; Singh, Meharvan; Uht, Rosalie M.; Schreihofer, Derek A.; Yang, Shaohua; Planz, John V.Age-related brain disorders are associated with the decline in the ability of brain cells to cope with homeostatic challenge. Although all major brain cell types have the capacity to respond to homeostatic challenges, astrocytes are particularly well-equipped to counteract these challenges. Here, we focused on Connexin 43 (Cx43) as a protein that is not only highly expressed in astrocytes, but whose expression is critical to inter-cellular communication that in turn, can influence cell viability. Most studies to date have focused on the expression (i.e., abundance) of Cx43. However, a critical limitation of these studies is that they did not thoroughly examine functionality of the Cx43 channels. In particular, there is a paucity of data describing the differential contributions of Cx43-containing hemichannels versus Cx43-containing gap junctions to cellular functions. We hypothesized the astrocyte Cx43 hemichannel as a yet unreported target of androgens and estrogens based on three notions. First, our laboratory has determined that astrocytes are a relevant and important target of such gonadal steroid hormones as estrogens (e.g., 17[beta]-estradiol (abbreviated herein as estradiol or E2)) and androgens (such as DHT), through which these hormones promote healthy brain cell function. Second, oxidative stress is associated with an increase in Cx43 opening. Finally, the Cx43 gene promoter contains functional estrogen response element (ERE) half sites, and estradiol, as well as other estrogenic compounds, decrease Cx43 channel opening in peripheral (non-CNS) tissue. Based on these notions, we hypothesized that gonadal androgens and estrogens will inhibit Cx43 hemichannel opening in cortical astrocytes as well. My data revealed that while E2, dihydrotestosterone (DHT), and the estrogenic metabolite of DHT (3[beta]diol) all protect primary cortical astrocytes from the mixed metabolic/oxidative insult, iodoacetic acid (IAA), only DHT decreased astrocyte Cx43 mRNA expression. Consistent with their cytoprotective effects, however, all three steroids decrease astrocyte Cx43 hemichannel opening, and antagonized the increased opening of Cx43 hemichannels induced by IAA. In an effort to pursue the mechanism by which these steroids reduced Cx43 hemichannel opening, we evaluated the phosphorylation of Cx43 at two key residues, Ser 368 and Tyr 265. Phosphorylation at these residues is associated with channel closing, and as such, we predicted that the three hormones would increase the phosphorylation of Cx43 at one or both of these residues. Whereas Tyr265 phosphorylation was unaffected any of the three hormones, DHT significantly reduced the phosphorylation of Cx43 at Ser368. These observations may indicate that while all three steroids contribute to astrocyte protection through a mechanism that involves blocking astrocyte Cx43 hemichannel opening, DHT may induce molecular changes in the astrocytes that are distinct from those induced by estradiol or 3[beta]diol. The knowledge gained through the experiments conducted not only enhance our understanding of how Cx43 hemichannels and Cx43 gap junctions influence astrocyte function and viability but also define Cx43 hemichannels as relevant targets of gonadal steroid hormone induced regulation of cell viability. Such knowledge may facilitate the development of more precise therapeutics (i.e., selectively targeting Cx43 hemichannels without activity at Cx43 gap junctions in the same cells or tissue), the benefit of which would be to better treat age-associated neurodegenerative disorders as well as disorders of peripheral tissueItem Estrogen administration attenuates post-stroke depression by enhancing CREB/BDNF/TrkB signaling in the rat hippocampus(Spandidos Publications, 2021-02-26) Jiang, Huigang; Xiao, Li; Jin, Kunlin; Shao, BeiA previous study demonstrated that 17beta-estradiol (E2), which is an antidepressant, can ameliorate post-stroke depression (PSD); however, the underlying mechanisms governing this remain largely unknown. Therefore, the present study developed a PSD model in rats, which was induced by left middle cerebral artery occlusion followed by exposure to chronic mild stress for 2 weeks. The results revealed that the activity of the cAMP response element-binding protein (CREB), a cellular transcription factor, and the associated brain-derived neurotrophic factor (BDNF)/tyrosine kinase B (TrkB) signaling were all attenuated in the hippocampus in PSD rats. The depression-like behaviors were significantly improved after treatment with E2, along with increased CREB and the BDNF/TrkB signaling activity. These results provide novel insight into the molecular basis of PSD, and suggest the potential involvement of CREB/BDNF/TrkB signaling in E2-mediated improvement of PSD in rats.Item Prospective Observational Study Evaluating Systemic Hormones and Corneal Crosslinking Effects in Keratoconus(Elsevier B.V., 2023-10-23) Van, Lyly; Bennett, Sashia; Nicholas, Sarah E.; Hjortdal, Jesper; McKay, Tina B.; Karamichos, DimitriosPURPOSE: To evaluate associations between hormone levels and corneal parameters in patients with keratoconus (KC), before and after photooxidative corneal collagen crosslinking (CXL). DESIGN: Prospective, observational cohort study. PARTICIPANTS: Twenty-eight patients with KC who were scheduled for CXL at Aarhus University Hospital in Denmark. METHODS: Androgen (dehydroepiandrosterone sulfate [DHEA-S]) and estrogen (estrone and estriol) plasma levels were measured and clinical assessments were performed before CXL and 2 to 3 months post-CXL, comparing the CXL eye with the control eye from the same participant. MAIN OUTCOME MEASURES: Associations between hormone levels and maximum corneal curvature (K(max)) and minimum central corneal thickness (CCt(min)) before and after CXL. RESULTS: Corneal collagen crosslinking was associated with a 2% reduction in K(max) values in the CXL eye, post-CXL, from baseline (median, 56.8 diopters [D]; 95% confidence interval [CI], 50.4-60.3) to the second visit (55.7 D; 95% CI, 50.4-58.8; P < 0.001). Systemic DHEA-S levels were 5 to 6 orders of magnitude higher than estriol or estrone concentrations in plasma. Importantly, estriol levels, rather than DHEA-S or estrone levels, were more closely correlated with K(max) before CXL (Spearman's r = 0.55, P = 0.01). Post-CXL K(max) and CCt(min) were not associated with DHEA-S, estrone, or estriol plasma levels at the same timepoint. CONCLUSIONS: This study provides supporting evidence based on a KC clinical population that systemic estrogen levels may influence corneal parameters (curvature and thickness) pre-CXL. Further studies evaluating the interplay between the therapeutic benefits of CXL and systemic hormone distributions are needed to determine if perturbation of the local corneal microenvironment influences endocrine function. FINANCIAL DISCLOSURES: The authors have no proprietary or commercial interest in any materials discussed in this article.Item Protein Biomakers of Estrogenic Impact on Mouse and Rat Uterus(2021-05) Thai, Stephen Duy-An; Prokai, Laszlo; Prokai-Tatrai, Katalin; Lacko, Andras G.Understanding the structural and morphological impact that occur in the uterus upon exposure to estrogens can reveal how these hormones elicit changes in the organ. This study seeks to revalidate the data obtained in studies of ovariectomized mice and rats treated with 17β-estradiol, followed by comparative analysis of the protein expression between the two animal models (the mice model studied by Prokai et al. [1] and the rat model presented in a dissertation by Rahlouni [2]). During these studies, female Swiss-Webster mice and Sprague-Dawley rats were ovariectomized (OVX) and divided respectively into two groups: 1) The control was treated with a corn oil vehicle while 2) The treatment group received 17β-estradiol injection for 5 days. Raw data gathered from the earlier proteomics studies were reanalyzed using Maxquant version 1.6.17, which utilized extracted ion chromatography technique (XIC). LFQ analyst and Ingenuity Pathway Analysis (IPA) version 5.0 were used to identify proteins that were differentially regulated by 17β-estradiol and perform comparative analyses of the protein expression between OVX mice and rats. Reanalysis of OVX mice identified 59 proteins of interest at 95% confidence with 29 upregulated and 30 downregulated significantly. Reanalysis of the OVX rats identified 126 differentially expressed proteins at 95% confidence with 98 upregulated and 27 downregulated significantly. Comparative analysis using IPA® found 27 proteins unique to mice and 85 proteins unique to rats. Conversely, the OVX mice and rats shared 19 proteins regulated by 17β-estradiol in the uterus. Ingenuity Pathway Analysis® also created networks in OVX mouse and rat models showing a relationship with estrogen receptors in the nucleus, which can bind 17β-estradiol and then initiate gene transcription. Although there is overlap between OVX mice and rat protein expression, the proteins that were found to be unique to each animal demonstrate that a complementary model using both animals provides a much broader view of uterine protein expression in OVX animals treated with 17?-estradiol. Additionally, this study illustrates the merit of reanalyzing older data with improved computational and bioinformatic tools to pinpoint proteins of interest for future analysis as potential markers of estrogenic effects in the uterus.Item Quantitative Proteomic Investigation of Estrogenic Endocrine-Disrupting Effects in the Rat Uterus(2016-05-01) Rahlouni, Fatima R.; Prokai, Laszlo; Lacko, Andras G.; Borejdo, JulianThe mammalian uterus is one of the most sensitive organs for estrogenicity. However, the widely used rat uterotrophic assay to assess known and potential estrogenic compounds only considers the uterine wet weight gain as an endpoint measurement. To complement this method with an advanced technology that reveals molecular targets, we analyzed changes in protein expression using label-free quantitative proteomic analysis by liquid chromatography–mass spectrometry from uterine protein extracts of ovariectomized rats after daily 17β-estradiol exposure for five days. We performed shotgun proteomic analysis of the uterus to identify candidate proteins for use as markers of estrogenicity. In addition, we mapped the differentially expressed proteins from untargeted analysis to signaling networks and biological processes through Ingenuity Pathway Analysis. We selected twelve of the top up- and down-regulated proteins for further evaluation by selected reaction monitoring-based targeted quantitation. Of the final six candidate markers, we verified all six as markers of estrogenicity by the application of the panel to testing rats exposed to a low and high dose of the known estrogenic compound bisphenol A. Altogether, the results of this study demonstrate the power of combining untargeted and targeted quantitative proteomic methods for a comprehensive analysis in rat uterus to evaluate changes in protein expression levels due to estrogen exposure, and to uncover candidate markers of estrogenicity in the development of a targeted proteomics panel.Item RETINA-TARGETED ESTROGEN PRODRUG: A NEW CONCEPT FOR RETINAL PROTECTION(2022-05) Lal, Kevin; Wu, Hongli; Prokai-Tatrai, Katalin; Liu, YangRetinal injury due to excessive light exposure during military duties often results in serious vision damage to soldiers including irreversible loss of visual function. However, therapeutic interventions that can promote retinal protection or reverse retinal damage are very limited. This unmet clinical need also persists in the public when strong lasers, light, or fire cause trauma in ocular tissues. It is well known that estrogen has been shown to exhibit various beneficial actions in the central nervous system, including positively affecting mood and protecting the neuronal cells against neurodegenerative diseases. Despite estrogen's potential, its detrimental side effects prevent its clinical uses for neurotherapy. To overcome this challenge, a bioprecursor prodrug was developed, called 10β,17β-dihydroxyestra-1,4-dien-3-one (DHED), that is selectively converted to E2 only in the neuronal cells, including retinal cells. To determine if treatment with DHED can sufficiently protect the photoreceptor cells from light-induced damage, male C57BL/6J mice were injected with or without 100 μg/kg DHED (n=15), 200 μg/kg DHED (n=15), 400 μg/kg DHED (n=15) and 200 μg/kg E2 (n=15) for 10 days before the light injury. Seven days after the light exposure, the visual function and retinal structure were examined by the spectral-domain optical coherence tomography (SD-OCT) and electroretinogram (ERG). After light exposure, we found massive photoreceptor loss as indicated by thinning of the outer nuclear layer (ONL) in groups that received no treatment. However, DHED treatment significantly prevented light-induced retinal structural changes and light-induced a- and b-wave reduction. Additionally, photoreceptor loss was decreased as indicated by increased outer nucellar layer thickness and SD-OCT data. The photoreceptor protective effects upon DHED-derived E2 treatment are stronger than that of the direct E2 treatment, consistent with our earlier observation that targeted E2 delivery via DHED prodrug produces more robust neuroprotection than direct administration of E2. In conclusion, our study supported our hypothesis that DHED is an efficacious and safe site-specific delivery agent to produce robust estrogen-mediated retinal neuroprotection.Item Sex Hormones, Growth Hormone, and the Cornea(MDPI, 2022-01-11) McKay, Tina B.; Priyadarsini, Shrestha; Karamichos, DimitriosThe growth and maintenance of nearly every tissue in the body is influenced by systemic hormones during embryonic development through puberty and into adulthood. Of the ~130 different hormones expressed in the human body, steroid hormones and peptide hormones are highly abundant in circulation and are known to regulate anabolic processes and wound healing in a tissue-dependent manner. Of interest, differential levels of sex hormones have been associated with ocular pathologies, including dry eye disease and keratoconus. In this review, we discuss key studies that have revealed a role for androgens and estrogens in the cornea with focus on ocular surface homeostasis, wound healing, and stromal thickness. We also review studies of human growth hormone and insulin growth factor-1 in influencing ocular growth and epithelial regeneration. While it is unclear if endogenous hormones contribute to differential corneal wound healing in common animal models, the abundance of evidence suggests that systemic hormone levels, as a function of age, should be considered as an experimental variable in studies of corneal health and disease.Item The role of aging and length of hypogonadism on the neuroprotective effects of dietary genistein following focal cerebral ischemia(2021-05) Oppong-Gyebi, Anthony; Schreihofer, Derek A.; Singh, Meharvan; Sumien, Nathalie; Yang, Shaohua; Shi, XiangrongThe risk of ischemic stroke increases with increasing age. Women beyond menopause have an exponential increase in stroke risk with worse post-stroke prognosis and mortalities compared to men of similar ages. One of the key reasons for this discrepancy is the sudden and drastic drop in the levels of the circulating principal female sex hormones estrogen and progesterone after menopause. Both sex hormones have been shown in several studies to provide neuroprotection against ischemic insults in stroke models and other disease models including Alzheimer's Disease and Parkinson's Disease. However, from clinical studies, neither estrogen nor progesterone alone or in combination has met clinical needs for the prevention of chronic cardiovascular diseases. These clinical failures were mainly evidenced by the absence of benefits in the human population or an increased predisposition to adverse side effects. Reports from studies including the Women's Health Initiative and Nurse's Health Study showed that the timing of initiation and age of recipients significantly influence the outcome of estrogen therapy. In this dissertation project, we investigated the plant-based estrogenic compound genistein as a possible alternative to estrogen therapy. It was hypothesized that the neuroprotective benefits of genistein will be less sensitive to the length of hypogonadism and age under experimental ischemic conditions. We used a rodent model of transient middle cerebral artery occlusion under varied lengths of estrogen deprivation and age to test the neuroprotection of dietary genistein. Findings from this dissertation show that early initiation of dietary genistein after hypogonadism improves aspects of cognition, an effect that is diminished following the long absence of circulating estrogen. Furthermore, pre-treatment with dietary genistein improves age-associated locomotor deficits after long-term hypogonadism after stroke. This dissertation, therefore, provides new considerations on the time-dependent sensitivity of the brain to genistein's effect as a potential therapeutic option to improve aspects of cognition and reduce the severity of stroke in the target population with low circulating estrogens.