Expression of Rasd1 in mouse endocrine pituitary cells and its response to dexamethasone
Stress (Amsterdam, Netherlands)
Foradori, CD;Mackay, L;Huang, CJ;Kemppainen, RJ;
PMID: 33840368 | DOI: 10.1080/10253890.2021.1907340
Dexamethasone-induced Ras-related protein 1 (Rasd1) is a member of the Ras superfamily of monomeric G proteins that have a regulatory function in signal transduction. Rasd1, also known as Dexras1 or AGS1, is rapidly induced by dexamethasone (Dex). While prior data indicates that Rasd1 is highly expressed in the pituitary and that the gene may function in regulation of corticotroph activity, its exact cellular localization in this tissue has not been delineated. Nor has it been determined which endocrine pituitary cell type(s) are responsive to Dex-induced expression of Rasd1. We hypothesized that Rasd1 is primarily localized in corticotrophs and furthermore, that its expression in these cells would be upregulated in response to exogenous Dex administration. Rasd1 expression in each pituitary cell type both under basal conditions and 1-hour post Dex treatment were examined in adult male mice. While a proportion of all endocrine pituitary cell types expressed Rasd1, a majority of corticotrophs and thyrotrophs expressed Rasd1 under basal condition. In vehicle treated animals, approximately 50-60% of corticotrophs and thyrotrophs cells expressed Rasd1 while the gene was detected in only 15-30% of lactotrophs, somatotrophs, and gonadotrophs. In Dex treated animals, Rasd1 expression was significantly increased in corticotrophs, somatotrophs, lactotrophs, and gonadotrophs but not thyrotrophs. In Dex treated animals, Rasd1 was detected in 80-95% of gonadotrophs and corticotrophs. In contrast, Dex treatment increased Rasd1 expression to a lesser extent (55-60%) in somatotrophs and lactotrophs. Corticotrophs of the pars intermedia, which lack glucocorticoid receptors, failed to display increased Rasd1 expression in Dex treated animals. Rasd1 is highly expressed in corticotrophs under basal conditions and is further increased after Dex treatment, further supporting its role in glucocorticoid negative feedback. In addition, the presence and Dex-induced expression of Rasd1 in endocrine pituitary cell types, other than corticotrophs, may implicate Rasd1 in novel pituitary functions.
Journal of Neuroendocrinology
He, J;Yan, J;Zha, X;Ding, X;Zhang, Y;Lu, Z;Xu, X;
| DOI: 10.1111/jne.13195
Sex differences in emotional behaviors and affective disorders have been widely noted, of which sexually dimorphic secretion of gonadal steroid hormones such as estrogen is suspected to play a role. However, the underlying neural mechanisms remain poorly understood. We noted that the expression of estrogen receptor 2 (Esr2, or ERβ), a key mediator of estrogen signaling in the brain, was enriched in the dorsal raphe nucleus (DRN), a region involved in emotion regulation. To test whether DRN Esr2 expression confers sex-specific susceptibility or vulnerability in emotional behaviors, we generated a conditional allele of Esr2 that allowed for site-specific deletion of Esr2 in DRN via local injection of Cre-expressing viruses. DRN-specific Esr2 deletion mildly increased anxiety behaviors in females, as shown by decreased time spent in the center zone of an open field in knockout females. By contrast, DRN Esr2 deletion had no effects on anxiety levels in males, as demonstrated by knockout males spending comparable time in the center zone of an open field and open arms of an elevated-plus maze. Furthermore, in the tail suspension test, DRN Esr2 deletion reduced immobility, a depression-like behavior, in a male-biased manner. Together these results reveal sex-specific functions of DRN Esr2 in regulating emotional behaviors and suggest targeted manipulation of DRN Esr2 signaling as a potential therapeutic strategy to treat sex-biased affective disorders.
Tooke BP, Yu H, Adams JM, Jones GL, Sutton-Kennedy T, Mundada L, Qi NR, Low MJ, Chhabra KH.
PMID: - | DOI: 10.1016/j.molmet.2018.11.004
Abstract
Objective
Life-threatening hypoglycemia is a major limiting factor in the management of diabetes. While it is known that counterregulatory responses to hypoglycemia are impaired in diabetes, molecular mechanisms underlying the reduced responses remain unclear. Given the established roles of the hypothalamic proopiomelanocortin (POMC)/melanocortin 4 receptor (MC4R) circuit in regulating sympathetic nervous system (SNS) activity and the SNS in stimulating counterregulatory responses to hypoglycemia, we hypothesized that hypothalamic POMC as well as MC4R, a receptor for POMC derived melanocyte stimulating hormones, is required for normal hypoglycemia counterregulation.
Methods
To test the hypothesis, we induced hypoglycemia or glucopenia in separate cohorts of mice deficient in either POMC or MC4R in the arcuate nucleus (ARC) or the paraventricular nucleus of the hypothalamus (PVH), respectively, and measured their circulating counterregulatory hormones. In addition, we performed a hyperinsulinemic-hypoglycemic clamp study to further validate the function of MC4R in hypoglycemia counterregulation. We also measured Pomc and Mc4r mRNA levels in the ARC and PVH, respectively, in the streptozotocin-induced type 1 diabetes mouse model and non-obese diabetic (NOD) mice to delineate molecular mechanisms by which diabetes deteriorates the defense systems against hypoglycemia. Finally, we treated diabetic mice with the MC4R agonist MTII, administered stereotaxically into the PVH, to determine its potential for restoring the counterregulatory response to hypoglycemia in diabetes.
Results
Stimulation of epinephrine and glucagon release in response to hypoglycemia or glucopenia was diminished in both POMC- and MC4R-deficient mice, relative to their littermate controls. Similarly, the counterregulatory response was impaired in association with decreased hypothalamic Pomc and Mc4r expression in the diabetic mice, a phenotype that was not reversed by insulin treatment which normalized glycemia. In contrast, infusion of an MC4R agonist in the PVH restored the counterregulatory response in diabetic mice.
Conclusion
In conclusion, hypothalamic Pomc as well as Mc4r, both of which are reduced in type 1 diabetic mice, are required for normal counterregulatory responses to hypoglycemia. Therefore, enhancing MC4R function may improve hypoglycemia counterregulation in diabetes.
Journal of Neuroendocrinology
Cara, A;Henson, E;Beekly, B;Elias, C;
| DOI: 10.1111/jne.13063
Androgens are steroid hormones that play a critical role in brain development and sexual maturation by acting upon both androgen receptors (AR), and estrogen receptors (ERα/β) after aromatization. The contribution of estrogens from aromatized androgens in brain development and the central regulation of metabolism, reproduction, and behavior is well defined, but the role of androgens acting on AR has been unappreciated. Here we map the sex specific expression of _Ar_ in the adult and developing mouse brain. Postnatal days (PND) 12 and 21 were used to target a critical window of prepubertal development. Consistent with previous literature in adults, sex-specific differences in _Ar_ expression were most profound in the bed nucleus of the stria terminalis (BST), medial amygdala (MEA), and medial preoptic area (MPO). _Ar_ expression was also high in these areas in PND 12 and 21 of both sexes. In addition, we describe extra-hypothalamic and extra-limbic areas which show moderate, consistent, and similar _Ar_ expression in both sexes at both prepubertal time points. Briefly, _Ar_ expression was observed in olfactory areas of the cerebral cortex, in the hippocampus, several thalamic nuclei, and cranial nerve nuclei involved in autonomic sensory and motor function. To further characterize forebrain populations of _Ar_ expressing neurons and determine whether they also coexpress estrogen receptors, we examined expression of _Ar_, _Esr1_, and _Esr2_ in prepubertal mice in selected nuclei. We found populations of neurons in the BST, MEA, and MPO that coexpress _Ar_, but not _Esr1_ or _Esr2_, while others express a combination of the three receptors. Our findings indicate that various brain areas express _Ar_ during prepubertal development and may play an important role in female neuronal development and physiology.
Kanaya M, Higo S, Ozawa H
PMID: 31877966 | DOI: 10.3390/ijms21010115
Estrogens play an essential role in multiple physiological functions in the brain, including reproductive neuroendocrine, learning and memory, and anxiety-related behaviors. To determine these estrogen functions, many studies have tried to characterize neurons expressing estrogen receptors known as ER? and ER?. However, the characteristics of ER?-expressing neurons in the rat brain still remain poorly understood compared to that of ER?-expressing neurons. The main aim of this study is to determine the neurochemical characteristics of ER?-expressing neurons in the rat hypothalamus using RNAscope in situ hybridization (ISH) combined with immunofluorescence. Strong Esr2 signals were observed especially in the anteroventral periventricular nucleus (AVPV), bed nucleus of stria terminalis, hypothalamic paraventricular nucleus (PVN), supraoptic nucleus, and medial amygdala, as previously reported. RNAscope ISH with immunofluorescence revealed that more than half of kisspeptin neurons in female AVPV expressed Esr2, whereas few kisspeptin neurons were found to co-express Esr2 in the arcuate nucleus. In the PVN, we observed a high ratio of Esr2 co-expression in arginine-vasopressin neurons and a low ratio in oxytocin and corticotropin-releasing factor neurons. The detailed neurochemical characteristics of ER?-expressing neurons identified in the current study can be very essential to understand the estrogen signaling via ER?.
Mitochondrial cristae-remodeling protein OPA1 in POMC neurons couples Ca2+ homeostasis with adipose tissue lipolysis
Gómez-Valadés, AG;Pozo, M;Varela, L;Boudjadja, MB;Ramírez, S;Chivite, I;Eyre, E;Haddad-Tóvolli, R;Obri, A;Milà-Guasch, M;Altirriba, J;Schneeberger, M;Imbernón, M;Garcia-Rendueles, AR;Gama-Perez, P;Rojo-Ruiz, J;Rácz, B;Alonso, MT;Gomis, R;Zorzano, A;D'Agostino, G;Alvarez, CV;Nogueiras, R;Garcia-Roves, PM;Horvath, TL;Claret, M;
PMID: 34343501 | DOI: 10.1016/j.cmet.2021.07.008
Appropriate cristae remodeling is a determinant of mitochondrial function and bioenergetics and thus represents a crucial process for cellular metabolic adaptations. Here, we show that mitochondrial cristae architecture and expression of the master cristae-remodeling protein OPA1 in proopiomelanocortin (POMC) neurons, which are key metabolic sensors implicated in energy balance control, is affected by fluctuations in nutrient availability. Genetic inactivation of OPA1 in POMC neurons causes dramatic alterations in cristae topology, mitochondrial Ca2+ handling, reduction in alpha-melanocyte stimulating hormone (α-MSH) in target areas, hyperphagia, and attenuated white adipose tissue (WAT) lipolysis resulting in obesity. Pharmacological blockade of mitochondrial Ca2+ influx restores α-MSH and the lipolytic program, while improving the metabolic defects of mutant mice. Chemogenetic manipulation of POMC neurons confirms a role in lipolysis control. Our results unveil a novel axis that connects OPA1 in POMC neurons with mitochondrial cristae, Ca2+ homeostasis, and WAT lipolysis in the regulation of energy balance.
Journal of Neuroendocrinology
Watanabe, Y;Fisher, L;Campbell, R;Jasoni, C;
| DOI: 10.1111/jne.13302
Polycystic ovary syndrome (PCOS) is a female endocrine disorder that is associated with prenatal exposure to excess androgens. In prenatally androgenized (PNA) mice that model PCOS, GABAergic neural transmission to and innervation of GnRH neurons is increased. Evidence suggests that elevated GABAergic innervation originates in the arcuate nucleus (ARC). We hypothesised that GABA-GnRH circuit abnormalities are a direct consequence of PNA, resulting from DHT binding to androgen receptor (AR) in the prenatal brain. However, whether prenatal ARC neurons express AR at the time of PNA treatment is presently unknown. We used RNAScope _in situ_ hybridization to localize AR mRNA (_Ar_)-expressing cells in healthy gestational day (GD) 17.5 female mouse brains and to assess co-expression levels in specific neuronal phenotypes. Our study revealed that less than 10% of ARC GABA cells expressed _Ar_. In contrast, we found that ARC kisspeptin neurons, critical regulators of GnRH neurons, were highly co-localised with _Ar_. Approximately 75% of ARC _Kiss1_-expressing cells also expressed _Ar_ at GD17.5, suggesting that ARC kisspeptin neurons are potential targets of PNA. Investigating other neuronal populations in the ARC we found that approximately 50% of pro-opiomelanocortin (_Pomc_) cells, 22% of tyrosine hydroxylase (_Th_) cells, 8% of agouti-related protein (_Agrp_) cells and 8% of somatostatin (_Sst_) cells express _Ar_. Lastly, RNAscope in coronal sections showed _Ar_ expression in the medial preoptic area (mPOA), and the ventral part of the lateral septum (vLS). These _Ar_-expressing regions were highly GABAergic, and 22% of GABA cells in the mPOA and 25% of GABA cells in the vLS also expressed _Ar_. Our findings identify specific neuronal phenotypes in the ARC, mPOA and vLS that are androgen sensitive in late gestation. PNA-induced functional changes in these neurons may be related to the development of impaired central mechanisms associated with PCOS-like features.
Liu Y, Huang Y, Liu T, Wu H, Cui H, Gautron L.
PMID: 27111742 | DOI: -
While Agouti-related peptide (AgRP) neurons play a key role in the regulation of food intake, their contribution to the anorexia caused by pro-inflammatory insults has yet to be identified. Using a combination of neuroanatomical and pharmacogenetics experiments, this study sought to investigate the importance of AgRP neurons and downstream targets in the anorexia caused by the peripheral administration of a moderate dose of lipopolysaccharide (LPS; 100 μ g/kg, ip). First, in the C57/Bl6 mouse, we demonstrated that LPS induced c-fos in select AgRP-innervated brain sites involved in feeding, but not in any arcuate proopiomelanocortin neurons. Double immunohistochemistry further showed that LPS selectively induced c-Fos in a large subset of melanocortin 4 receptor-expressing neurons in the lateral parabrachial nucleus. Secondly, we used pharmacogenetics to stimulate the activity of AgRP neurons during the course of LPS-induced anorexia. In AgRP-Cre mice expressing the designer receptor hM3Dq-Gq only in AgRP neurons, the administration of the designer drug clozapine-N-oxide (CNO) induced robust food intake. Strikingly, CNO-mediated food intake was rapidly and completely blunted by the coadministration of LPS. Neuroanatomical experiments further indicated that LPS did not interfere with the ability of CNO to stimulate c-Fos in AgRP neurons. In summary, our findings combined together support the view that the stimulation of select AgRP-innervated brain sites and target neurons, rather than the inhibition of AgRP neurons themselves, is likely to contribute to the rapid suppression of food intake observed during acute bacterial endotoxemia.
Zahaf, A;Kassoussi, A;Hutteau-Hamel, T;Mellouk, A;Marie, C;Zoupi, L;Tsouki, F;Mattern, C;Bobé, P;Schumacher, M;Williams, A;Parras, C;Traiffort, E;
PMID: 36949062 | DOI: 10.1038/s41467-023-36846-w
Neuroprotective, anti-inflammatory, and remyelinating properties of androgens are well-characterized in demyelinated male mice and men suffering from multiple sclerosis. However, androgen effects mediated by the androgen receptor (AR), have been only poorly studied in females who make low androgen levels. Here, we show a predominant microglial AR expression in demyelinated lesions from female mice and women with multiple sclerosis, but virtually undetectable AR expression in lesions from male animals and men with multiple sclerosis. In female mice, androgens and estrogens act in a synergistic way while androgens drive microglia response towards regeneration. Transcriptomic comparisons of demyelinated mouse spinal cords indicate that, regardless of the sex, androgens up-regulate genes related to neuronal function integrity and myelin production. Depending on the sex, androgens down-regulate genes related to the immune system in females and lipid catabolism in males. Thus, androgens are required for proper myelin regeneration in females and therapeutic approaches of demyelinating diseases need to consider male-female differences.
Porniece Kumar, M;Cremer, AL;Klemm, P;Steuernagel, L;Sundaram, S;Jais, A;Hausen, AC;Tao, J;Secher, A;Pedersen, TÅ;Schwaninger, M;Wunderlich, FT;Lowell, BB;Backes, H;Brüning, JC;
PMID: 34931084 | DOI: 10.1038/s42255-021-00499-0
Insulin acts on neurons and glial cells to regulate systemic glucose metabolism and feeding. However, the mechanisms of insulin access in discrete brain regions are incompletely defined. Here we show that insulin receptors in tanycytes, but not in brain endothelial cells, are required to regulate insulin access to the hypothalamic arcuate nucleus. Mice lacking insulin receptors in tanycytes (IR∆Tan mice) exhibit systemic insulin resistance, while displaying normal food intake and energy expenditure. Tanycytic insulin receptors are also necessary for the orexigenic effects of ghrelin, but not for the anorexic effects of leptin. IR∆Tan mice exhibit increased agouti-related peptide (AgRP) neuronal activity, while displaying blunted AgRP neuronal adaptations to feeding-related stimuli. Lastly, a highly palatable food decreases tanycytic and arcuate nucleus insulin signalling to levels comparable to those seen in IR∆Tan mice. These changes are rooted in modifications of cellular stress responses and of mitochondrial protein quality control in tanycytes. Conclusively, we reveal a critical role of tanycyte insulin receptors in gating feeding-state-dependent regulation of AgRP neurons and systemic insulin sensitivity, and show that insulin resistance in tanycytes contributes to the pleiotropic manifestations of obesity-associated insulin resistance.
Claflin KE, Sandgren JA, Lambertz AM, Weidemann BJ, Littlejohn NK, Burnett CM, Pearson NA, Morgan DA, Gibson-Corley KN, Rahmouni K, Grobe JL.
PMID: 28263184 | DOI: 10.1172/JCI88641
Leptin contributes to the control of resting metabolic rate (RMR) and blood pressure (BP) through its actions in the arcuate nucleus (ARC). The renin-angiotensin system (RAS) and angiotensin AT1 receptors within the brain are also involved in the control of RMR and BP, but whether this regulation overlaps with leptin's actions is unclear. Here, we have demonstrated the selective requirement of the AT1A receptor in leptin-mediated control of RMR. We observed that AT1A receptors colocalized with leptin receptors (LEPRs) in the ARC. Cellular coexpression of AT1A and LEPR was almost exclusive to the ARC and occurred primarily within neurons expressing agouti-related peptide (AgRP). Mice lacking the AT1A receptor specifically in LEPR-expressing cells failed to show an increase in RMR in response to a high-fat diet and deoxycorticosterone acetate-salt (DOCA-salt) treatments, but BP control remained intact. Accordingly, loss of RMR control was recapitulated in mice lacking AT1A in AgRP-expressing cells. We conclude that angiotensin activates divergent mechanisms to control BP and RMR and that the brain RAS functions as a major integrator for RMR control through its actions at leptin-sensitive AgRP cells of the ARC.
Shi, Z;Stornetta, DS;Stornetta, RL;Brooks, VL;
PMID: 34937769 | DOI: 10.1523/ENEURO.0404-21.2021
The arcuate nucleus (ArcN) is an integrative hub for the regulation of energy balance, reproduction, and arterial pressure (AP), all of which are influenced by Angiotensin II (AngII); however, the cellular mechanisms and downstream neurocircuitry are unclear. Here we show that ArcN AngII increases AP in female rats via two phases, both of which are mediated via activation of AngII type 1 receptors (AT1aR): initial vasopressin-induced vasoconstriction, followed by slowly developing increases in sympathetic nerve activity (SNA) and heart rate (HR). In male rats, ArcN AngII evoked a similarly slow increase in SNA, but the initial pressor response was variable. In females, the effects of ArcN AngII varied during the estrus cycle, with significant increases in SNA, HR, and AP occurring during diestrus and estrus, but only increased AP during proestrus. Pregnancy markedly increased the expression of AT1aR in the ArcN with parallel substantial AngII-induced increases in SNA and MAP. In both sexes, the sympathoexcitation relied on suppression of tonic ArcN sympathoinhibitory Neuropeptide Y inputs, and activation of pro-opiomelanocortin (POMC) projections, to the paraventricular nucleus (PVN). Few or no NPY or POMC neurons expressed the AT1aR, suggesting that AngII increases AP and SNA at least in part indirectly via local interneurons, which express tyrosine hydroxylase (TH) and VGat (i.e. GABAergic). ArcN TH neurons release GABA locally, and central AT1aR and TH neurons mediate stress responses; therefore, we propose that TH AT1aR neurons are well situated to locally coordinate the regulation of multiple modalities within the ArcN in response to stress.SIGNIFICANCEThe arcuate nucleus (ArcN) is an integrative hub for the regulation of energy balance, reproduction, and arterial pressure (AP), all of which are influenced by Angiotensin II (AngII). Here we show that ArcN AngII activates AT1aR to increase AP in male and female rats by slowly increasing sympathetic nerve activity. In females, ArcN AngII also evoked an initial pressor response mediated by vasopressin-induced vasoconstriction. Pregnant and estrus females responded more than males, in association with higher ArcN AT1aR expression. AT1aR were identified in ArcN interneurons that express tyrosine hydroxylase (TH) and GABA. Since brain AT1aR and TH mediate stress responses, ArcN AT1aR TH neurons are well situated to locally coordinate autonomic, hormonal, and behavioral responses to stress.