School of BioSciences - Research Publications
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ItemAndrogen receptor antagonism accelerates disease onset in the SOD1G93A mouse model of amyotrophic lateral sclerosis(WILEY, 2019-07)BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease typically more common in males, implicating androgens in progression of both patients and mouse models. Androgen effects are mediated by androgen receptor which is highly expressed in spinal motor neurons and skeletal muscles. To clarify the role of androgen receptors in ALS, we therefore examined the effect of androgen receptor antagonism in the SOD1G93A mouse model. EXPERIMENTAL APPROACH: The androgen receptor antagonist, flutamide, was administered to presymptomatic SOD1G93A mice as a slow-release subcutaneous implant (5 mg·day-1 ). Testosterone, flutamide, and metabolite levels were measured in blood and spinal cord tissue by LC-MS-MS. Effects on disease onset and progression were assessed using motor function tests, survival, muscle, and neuropathological analyses. KEY RESULTS: Flutamide was metabolised to 2-hydroxyflutamide achieving steady-state plasma levels across the study duration and reached the spinal cord at pharmacologically active concentrations. Flutamide treatment accelerated disease onset and locomotor dysfunction in male SOD1G93A mice, but not female mice, without affecting survival. Analysis of hindlimb muscles revealed exacerbation of myofibre atrophy in male SOD1G93A mice treated with flutamide, although motor neuron pathology was not affected. CONCLUSION AND IMPLICATIONS: The androgen receptor antagonist accelerated disease onset in male SOD1G93A mice, leading to exacerbated muscle pathology, consistent with a role of androgens in modulating disease severity, sexual dimorphism, and peripheral pathology in ALS. These results also demonstrate a key contribution of skeletal muscle pathology to disease onset, but not outcome, in this mouse model of ALS.
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ItemTestosterone-induced adult neurosphere growth is mediated by sexually-dimorphic aromatase expression.(Frontiers Media SA, 2015)We derived adult neural stem/progenitor cells (NSPCs) from the sub-ventricular zone of male and female mice to examine direct responses to principal sex hormones. In the presence of epidermal growth factor (EGF) and fibroblast growth factor-2 (FGF2) NSPCs of both sexes expressed nestin and sox2, and could be maintained as neurospheres without addition of any sex hormones. The reverse was not observed; neither testosterone (T), 17β-estradiol (E2) nor progesterone (P4) was able to support neurosphere growth in the absence of EGF and FGF2. Ten nanomolar T, E2 or P4 induced nestin(+) cell proliferation within 20 min and enhanced neurosphere growth over 7 days irrespective of sex, which was abolished by Erk inhibition with 20 μM U0126. Maintaining neurospheres with each sex hormone did not affect subsequent neuronal differentiation. However, 10 nM T, E2 or P4 added during differentiation increased βIII tubulin(+) neuron production with E2 being more potent compared to T and P4 in both sexes. Androgen receptor (AR) inhibition with 20 μM flutamide but not aromatase inhibition with 10 μM letrozole reduced basal and T-induced neurosphere growth in females, while only concurrent inhibition of AR and aromatase produced the same effect in males. This sex-specific effect was supported by higher aromatase expression in male neurospheres compared to females measured by Western blot and green fluorescent protein (GFP) reporter. Ten micromolar menadione induced oxidative stress, impaired neurosphere growth and up-regulated aromatase expression in both sexes. However, under oxidative stress letrozole significantly exacerbated impaired neurosphere growth in males only. While both E2 and T could prevent oxidative stress-induced growth reduction in both sexes, the effects of T were dependent on innate aromatase activity. We show for the first time that intrinsic androgen and estrogen signaling may impact the capacity of NSPCs to produce neural progenitors under pathological conditions of oxidative stress.
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ItemThe Aromatase Gene CYP19A1: Several Genetic and Functional Lines of Evidence Supporting a Role in Reading, Speech and Language(SPRINGER, 2012-07)Inspired by the localization, on 15q21.2 of the CYP19A1 gene in the linkage region of speech and language disorders, and a rare translocation in a dyslexic individual that was brought to our attention, we conducted a series of studies on the properties of CYP19A1 as a candidate gene for dyslexia and related conditions. The aromatase enzyme is a member of the cytochrome P450 super family, and it serves several key functions: it catalyzes the conversion of androgens into estrogens; during early mammalian development it controls the differentiation of specific brain areas (e.g. local estrogen synthesis in the hippocampus regulates synaptic plasticity and axonal growth); it is involved in sexual differentiation of the brain; and in songbirds and teleost fishes, it regulates vocalization. Our results suggest that variations in CYP19A1 are associated with dyslexia as a categorical trait and with quantitative measures of language and speech, such as reading, vocabulary, phonological processing and oral motor skills. Variations near the vicinity of its brain promoter region altered transcription factor binding, suggesting a regulatory role in CYP19A1 expression. CYP19A1 expression in human brain correlated with the expression of dyslexia susceptibility genes such as DYX1C1 and ROBO1. Aromatase-deficient mice displayed increased cortical neuronal density and occasional cortical heterotopias, also observed in Robo1-/- mice and human dyslexic brains, respectively. An aromatase inhibitor reduced dendritic growth in cultured rat neurons. From this broad set of evidence, we propose CYP19A1 as a candidate gene for human cognitive functions implicated in reading, speech and language.
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ItemHepatic Glucose Intolerance Precedes Hepatic Steatosis in the Male Aromatase Knockout (ArKO) Mouse(PUBLIC LIBRARY SCIENCE, 2014-02-10)Estrogens are known to play a role in modulating metabolic processes within the body. The Aromatase knockout (ArKO) mice have been shown to harbor factors of Metabolic syndrome with central adiposity, hyperinsulinemia and male-specific hepatic steatosis. To determine the effects of estrogen ablation and subsequent replacement in males on whole body glucose metabolism, three- and six-month-old male ArKO mice were subjected to whole body glucose, insulin and pyruvate tolerance tests and analyzed for ensuing metabolic changes in liver, adipose tissue, and skeletal muscle. Estrogen-deficient male ArKO mice showed increased gonadal adiposity which was significantly reduced upon 17β-estradiol (E2) treatment. Concurrently, elevated ArKO serum leptin levels were significantly reduced upon E2 treatment and lowered serum adiponectin levels were restored to wild type levels. Three-month-old male ArKO mice were hyperglycemic, and both glucose and pyruvate intolerant. These phenotypes continued through to 6 months of age, highlighting a loss of glycemic control. ArKO livers displayed changes in gluconeogenic enzyme expression, and in insulin signaling pathways upon E2 treatment. Liver triglycerides were increased in the ArKO males only after 6 months of age, which could be reversed by E2 treatment. No differences were observed in insulin-stimulated ex vivo muscle glucose uptake nor changes in ArKO adipose tissue and muscle insulin signaling pathways. Therefore, we conclude that male ArKO mice develop hepatic glucose intolerance by the age of 3 months which precedes the sex-specific development of hepatic steatosis. This can be reversed upon the administration of exogenous E2.
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ItemRestoration of the Dopamine Transporter through Cell Therapy Improves Dyskinesia in a Rat Model of Parkinson's Disease(PUBLIC LIBRARY SCIENCE, 2016-04-14)The dyskinesia of Parkinson's Disease is most likely due to excess levels of dopamine in the striatum. The mechanism may be due to aberrant synthesis but also, a deficiency or absence of the Dopamine Transporter. In this study we have examined the proposition that reinstating Dopamine Transporter expression in the striatum would reduce dyskinesia. We transplanted c17.2 cells that stably expressed the Dopamine Transporter into dyskinetic rats. There was a reduction in dyskinesia in rats that received grafts expressing the Dopamine Transporter. Strategies designed to increase Dopamine Transporter in the striatum may be useful in treating the dyskinesia associated with human Parkinson's Disease.
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ItemSCA-1 Labels a Subset of Estrogen-Responsive Bipotential Repopulating Cells within the CD24+ CD49fhi Mammary Stem Cell-Enriched Compartment(CELL PRESS, 2017-02-14)Estrogen stimulates breast development during puberty and mammary tumors in adulthood through estrogen receptor-α (ERα). These effects are proposed to occur via ERα+ luminal cells and not the mammary stem cells (MaSCs) that are ERαneg. Since ERα+ luminal cells express stem cell antigen-1 (SCA-1), we sought to determine if SCA-1 could define an ERα+ subset of EpCAM+/CD24+/CD49fhi MaSCs. We show that the MaSC population has a distinct SCA-1+ population that is abundant in pre-pubertal mammary glands. The SCA-1+ MaSCs have less stem cell markers and less in vivo repopulating activity than their SCA-1neg counterparts. However, they express ERα and specifically enter the cell cycle at puberty. Using estrogen-deficient aromatase knockouts (ArKO), we showed that the SCA-1+ MaSC could be directly modulated by estrogen supplementation. Thus, SCA-1 enriches for an ERα+, estrogen-sensitive subpopulation within the CD24+/CD49fhi MaSC population that may be responsible for the hormonal sensitivity of the developing mammary gland.
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ItemEffects of Estrogens on Adipokines and Glucose Homeostasis in Female Aromatase Knockout Mice(PUBLIC LIBRARY SCIENCE, 2015-08-28)The maintenance of glucose homeostasis within the body is crucial for constant and precise performance of energy balance and is sustained by a number of peripheral organs. Estrogens are known to play a role in the maintenance of glucose homeostasis. Aromatase knockout (ArKO) mice are estrogen-deficient and display symptoms of dysregulated glucose metabolism. We aim to investigate the effects of estrogen ablation and exogenous estrogen administration on glucose homeostasis regulation. Six month-old female wildtype, ArKO, and 17β-estradiol (E2) treated ArKO mice were subjected to whole body tolerance tests, serum examination of estrogen, glucose and insulin, ex-vivo muscle glucose uptake, and insulin signaling pathway analyses. Female ArKO mice display increased body weight, gonadal (omental) adiposity, hyperinsulinemia, and liver triglycerides, which were ameliorated upon estrogen treatment. Tolerance tests revealed that estrogen-deficient ArKO mice were pyruvate intolerant hence reflecting dysregulated hepatic gluconeogenesis. Analyses of skeletal muscle, liver, and adipose tissues supported a hepatic-based glucose dysregulation, with a down-regulation of Akt phosphorylation (a key insulin signaling pathway molecule) in the ArKO liver, which was improved with E2 treatment. Concurrently, estrogen treatment lowered ArKO serum leptin and adiponectin levels and increased inflammatory adipokines such as tumour necrosis factor alpha (TNFα) and interleukin 6 (IL6). Furthermore, estrogen deficiency resulted in the infiltration of CD45 macrophages into gonadal adipose tissues, which cannot be reversed by E2 treatment. This study describes the effects of estrogens on glucose homeostasis in female ArKO mice and highlights a primary phenotype of hepatic glucose dysregulation and a parallel estrogen modified adipokine profile.