Hypothalamic Neurons Research Articles

Male-specific vasotocin expression in the medaka tuberal hypothalamus: Androgen dependence and probable role in aggression

Terrestrial vertebrates have a population of androgen-dependent vasotocin (VT)-expressing neurons in the extended amygdala that are more abundant in males and mediate male-typical social behaviors, including aggression. Teleosts lack these neurons but instead have novel male-specific VT-expressing neurons in the tuberal hypothalamus. Here we found in medaka that vt expression in these neurons is dependent on post-pubertal gonadal androgens and that androgens can act on these neurons to directly stimulate vt transcription via the androgen receptor subtype Ara. Furthermore, administration of exogenous VT induced aggression in females and alterations in the androgen milieu led to correlated changes in the levels of tuberal hypothalamic vt expression and aggression in both sexes. However, genetic ablation of vt failed to prevent androgen-induced aggression in females. Collectively, our results demonstrate a marked androgen dependence of male-specific vt expression in the teleost tuberal hypothalamus, although its relevance to male-typical aggression needs to be further validated.

Postnatal Development and Maintenance of Functional Pituitary Gonadotrophs Is Dependent on PI4-Kinase A.

Postnatal development of functional pituitary gonadotrophs is necessary for maturation of the hypothalamic-pituitary-gonadal axis, puberty, and reproduction. Here we examined the role of PI4-kinase A, which catalyzes the biosynthesis of PI4P in mouse reproduction by knocking out this enzyme in cells expressing the gonadotropin-releasing hormone (GnRH) receptor. Knockout (KO) mice were infertile, reflecting underdeveloped gonads and reproductive tracts and lack of puberty. The number and distribution of hypothalamic GnRH neurons and Gnrh1 expression in postnatal KOs were not affected, whereas Kiss1/kisspeptin expression was increased. KO of PI4-kinase A also did not alter embryonic establishment and neonatal development and function of the gonadotroph population. However, during the postnatal period, there was a progressive loss of expression of gonadotroph-specific genes, including Fshb, Lhb, and Gnrhr, accompanied by low gonadotropin synthesis. The postnatal gonadotroph population also progressively declined, reaching approximately one-third of that observed in controls at 3 months of age. In these residual gonadotrophs, GnRH-dependent calcium signaling and calcium-dependent membrane potential changes were lost, but intracellular administration of inositol-14,5-trisphosphate rescued this signaling. These results indicate a key role for PI4-kinase A in the postnatal development and maintenance of a functional gonadotroph population.

Anti-inflammatory effects of hunger are transmitted to the periphery via projection-specific AgRP circuits

Caloric restriction has anti-inflammatory effects. However, the coordinated physiological actions that lead to reduced inflammation in a state of caloric deficit (hunger) are largely unknown. Using a mouse model of injury-induced peripheral inflammation, we find that food deprivation reduces edema, temperature, and cytokine responses that occur after injury. The magnitude of the anti-inflammatory effect that occurs during hunger is more robust than that of non-steroidal anti-inflammatory drugs. The effects of hunger are recapitulated centrally by activity in nutrient-sensing hypothalamic agouti-related protein (AgRP)-expressing neurons. We find that AgRP neurons projecting to the paraventricular nucleus of the hypothalamus rapidly and robustly reduce inflammation and mediate the majority of hunger's anti-inflammatory effects. Intact vagal efferent signaling is required for the anti-inflammatory action of hunger, revealing a brain-to-periphery pathway for this reduction in inflammation. Taken together, these data begin to unravel a potent anti-inflammatory pathway engaged by hypothalamic AgRP neurons to reduce inflammation.

Lateral hypothalamic proenkephalin neurons drive threat-induced overeating associated with a negative emotional state

Psychological stressors, like the nearby presence of a predator, can be strong enough to induce physiological/hormonal alterations, leading to appetite changes. However, little is known about how threats can alter feeding-related hypothalamic circuit functions. Here, we found that proenkephalin (Penk)-expressing lateral hypothalamic (LHPenk) neurons of mice exposed to predator scent stimulus (PSS) show sensitized responses to high-fat diet (HFD) eating, whereas silencing of the same neurons normalizes PSS-induced HFD overconsumption associated with a negative emotional state. Downregulation of endogenous enkephalin peptides in the LH is crucial for inhibiting the neuronal and behavioral changes developed after PSS exposure. Furthermore, elevated corticosterone after PSS contributes to enhance the reactivity of glucocorticoid receptor (GR)-containing LHPenk neurons to HFD, whereas pharmacological inhibition of GR in the LH suppresses PSS-induced maladaptive behavioral responses. We have thus identified the LHPenk neurons as a critical component in the threat-induced neuronal adaptation that leads to emotional overconsumption.

An Astyanax mexicanus mao knockout line uncovers the developmental roles of monoamine homeostasis in fish brain.

Monoaminergic systems are conserved in vertebrates, yet they present variations in neuroanatomy, genetic components and functions across species. MonoAmine Oxidase, or MAO, is the enzyme responsible for monoamine degradation. While mammals possess two genes, MAO-A and MAO-B, fish possess one single mao gene. To study the function of MAO and monoamine homeostasis on fish brain development and physiology, here we have generated a mao knockout line in Astyanax mexicanus (surface fish), by CRISPR/Cas9 technology. Homozygote mao knockout larvae died at 13 days post-fertilization. Through a time-course analysis, we report that hypothalamic serotonergic neurons undergo fine and dynamic regulation of serotonin level upon loss of mao function, in contrast to those in the raphe, which showed continuously increased serotonin levels - as expected. Dopaminergic neurons were not affected by mao loss-of-function. At behavioral level, knockout fry showed a transient decrease in locomotion that followed the variations in the hypothalamus serotonin neuronal levels. Finally, we discovered a drastic effect of mao knockout on brain progenitors proliferation in the telencephalon and hypothalamus, including a reduction in the number of proliferative cells and an increase of the cell cycle length. Altogether, our results show that MAO has multiple and varied effects on Astyanax mexicanus brain development. Mostly, they bring novel support to the idea that serotonergic neurons in the hypothalamus and raphe of the fish brain are different in nature and identity, and they unravel a link between monoaminergic homeostasis and brain growth.

Hypothalamic MCH Neurons: From Feeding to Cognitive Control.

Modern neuroscience is progressively elucidating that the classic view positing distinct brain regions responsible for survival, emotion, and cognitive functions is outdated. The hypothalamus demonstrates the interdependence of these roles, as it is traditionally known for fundamental survival functions like energy and electrolyte balance, but is now recognized to also play a crucial role in emotional and cognitive processes. This review focuses on lateral hypothalamic melanin-concentrating hormone (MCH) neurons, producing the neuropeptide MCH-a relatively understudied neuronal population with integrative functions related to homeostatic regulation and motivated behaviors, with widespread inputs and outputs throughout the entire central nervous system. Here, we review early findings and recent literature outlining their role in the regulation of energy balance, sleep, learning, and memory processes.

Overactivation of GnRH neurons is sufficient to trigger polycystic ovary syndrome-like traits in female mice

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder leading to anovulatory infertility. Abnormalities in the central neuroendocrine system governed by gonadotropin-releasing hormone (GnRH) neurons might be related to ovarian dysfunction in PCOS, although the link in this disordered brain-to-ovary communication remains unclear. Here, we manipulated GnRH neurons using chemogenetics in adult female mice to unveil whether chronic overaction of these neurons would trigger PCOS-like hormonal and reproductive impairments. We used adult Gnrh1cre female mice to selectively target and express the designer receptors exclusively activated by designer drugs (DREADD)-based chemogenetic tool hM3D(Gq) in hypophysiotropic GnRH neurons. Chronic chemogenetic activation protocol was carried out with clozapine N-oxide (CNO) i.p. injections every 48h over a month. We evaluated the reproductive and hormonal profile before, during, and two months after chemogenetic manipulations. We discovered that the overactivation of GnRH neurons was sufficient to disrupt reproductive cycles, promote hyperandrogenism, and induce ovarian dysfunction. These PCOS features were detected with a long-lasting neuroendocrine dysfunction through abnormally high luteinizing hormone (LH) pulse secretion. Additionally, the GnRH-R blockade prevented the establishment of long-term neuroendocrine dysfunction and androgen excess in these animals. Taken together, our results show that hyperactivity of hypothalamic GnRH neurons is a major driver of reproductive and hormonal impairments in PCOS and suggest that antagonizing the aberrant GnRH signaling could be an efficient therapeutic venue for the treatment of PCOS. European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement n◦ 725149).

Unloading-Induced Skeletal Interoception Alters Hypothalamic Signaling to Promote Bone Loss and Fat Metabolism.

Microgravity is the primary factor that affects human physiology in spaceflight, particularly bone loss and disturbances of the central nervous system. However, little is known about the cellular and molecular mechanisms of these effects. Here, it is reported that in mice hindlimb unloading stimulates expression of neuropeptide Y (NPY) and tyrosine hydroxylase (TH) in the hypothalamus, resulting in bone loss and altered fat metabolism. Enhanced expression of TH and NPY in the hypothalamus occurs downstream of a reduced prostaglandin E2 (PGE2)-mediated ascending interoceptive signaling of the skeletal interoception. Sympathetic antagonist propranolol or deletion of Adrb2 in osteocytes rescue bone loss in the unloading model. Moreover, depletion of TH+ sympathetic nerves or inhibition of norepinephrine release ameliorated bone resorption. Stereotactic inhibition of NPY expression in the hypothalamic neurons reduces the food intake with altered energy expenditure with a limited effect on bone, indicating hypothalamic neuroendocrine factor NPY in the facilitation of bone formation by sympathetic TH activity. These findings suggest that reduced PGE2-mediated interoceptive signaling in response to microgravity or unloading has impacts on the skeletal and central nervous systems that are reciprocally regulated.

Biohybrid tongue based on hypothalamic neuronal network-on-a-chip for real-time blood glucose sensing and assessment

The expression of sweet receptors in the hypothalamus has been implicated in energy homeostasis control and the pathogenesis of obesity and diabetes. However, the exact mechanism by which hypothalamic glucose-sensing neurons function remains unclear. Conventional detection methods, such as fiber photometry, optogenetics, brain-machine interfaces, patch clamp and calcium imaging, pose limitations for real-time glucose perception due to their complexity, cytotoxicity and so on. Therefore, this study proposes a biohybrid tongue based on hypothalamic neuronal network (HNN)-on-a-chip coupling with microelectrode array (MEA) for real-time glucose perception. Hypothalamic neuronal cultures were cultivated on a two-dimensional “brain-on-chip” device, enabling the formation of neuronal networks and electrophysiological signal detection. Additionally, we investigated the endogenous expression of sweet taste receptors (T1R2/T1R3) in hypothalamic neuronal cells, providing the basis for the biohybrid tongue based on HNN-on-a-chip's sweetness detection capabilities. The spike signal response to sucrose and glucose stimulation was detected, and concentration-dependent responses were explored with glucose concentrations ranging from 0.01 mM to 8 mM. MEAs allow for real-time recordings, enabling the observation of dynamic changes in neuronal responses to glucose fluctuations over time. The biohybrid tongue based on HNN-on-a-chip can measure various parameters, including spike frequency and amplitude, providing insights into neuronal firing patterns and excitability. Moreover, hypothalamic glucoregulatory neurons that sense and respond to changes in blood glucose was identified, including glucose-excited neurons (GE-Neurons) and glucose-inhibited neurons (GI-Neurons). The detection range for GE-Neurons spans from 0.4 to 6 mM, while GI-Neurons demonstrate sensitivity within the range of 1–8 mM. And the glucose detection limit was firmly established at 0.01 mM. Through non-linear regression analysis, the IC50 for GI-Neurons' spike firing was determined to be 4.18 mM. In conclusion, the biohybrid tongue based on HNN-on-a-chip offers a valuable in vitro tool for studying hypothalamic neurons, elucidating glucose sensing mechanisms, and understanding hypothalamic neuronal function.

Diffuse traumatic brain injury substantially alters plasma growth hormone in the juvenile rat.

Traumatic brain injury (TBI) can damage the hypothalamus and cause improper activation of the growth hormone (GH) axis, leading to growth hormone deficiency (GHD). GHD is one of the most prevalent endocrinopathies following TBI in adults; however, the extent to which GHD affects juveniles remains understudied. We used postnatal day 17 rats (n = 83), which model the late infantile/toddler period, and assessed body weights, GH levels, and number of hypothalamic somatostatin neurons at acute (1, 7 days post injury (DPI)) and chronic (18, 25, 43 DPI) time points. We hypothesized that diffuse TBI would alter circulating GH levels because of damage to the hypothalamus, specifically somatostatin neurons. Data were analyzed with generalized linear and mixed effects models with fixed effects interactions between the injury and time. Despite similar growth rates over time with age, TBI rats weighed less than shams at 18 DPI (postnatal day 35; P = 0.03, standardized effect size [d] = 1.24), which is around the onset of puberty. Compared to shams, GH levels were lower in the TBI group during the acute period (P = 0.196; d = 12.3) but higher in the TBI group during the chronic period (P = 0.10; d = 52.1). Although not statistically significant, TBI-induced differences in GH had large standardized effect sizes, indicating biological significance. The mean number of hypothalamic somatostatin neurons (an inhibitor of GH) positively predicted GH levels in the hypothalamus but did not predict GH levels in the somatosensory cortex. Understanding TBI-induced alterations in the GH axis may identify therapeutic targets to improve the quality of life of pediatric survivors of TBI.

Impact and Role of Hypothalamic Corticotropin Releasing Hormone Neurons in Withdrawal from Chronic Alcohol Consumption in Female and Male Mice.

Worldwide, alcohol use and abuse are a leading risk of mortality, causing 5.3% of all deaths (World Health Organization, 2022). The endocrine stress system, initiated by the peripheral release of corticotropin releasing hormone (CRH) from primarily glutamatergic neurons in the paraventricular nucleus of the hypothalamus (PVN), is profoundly linked with alcohol use, abuse, and relapse (Blaine and Sinha, 2017). These PVN CRH-releasing (PVNCRH) neurons are essential for peripheral and central stress responses (Rasiah et al., 2023), but little is known about how alcohol affects these neurons. Here, we show that two-bottle choice alcohol consumption blunts the endocrine-mediated corticosterone response to stress during acute withdrawal in female mice. Conversely, using slice electrophysiology, we demonstrate that acute withdrawal engenders a hyperexcitable phenotype of PVNCRH neurons in females that is accompanied by increased glutamatergic transmission in both male and female mice. GABAergic synaptic transmission was unaffected by alcohol history. We then tested whether chemogenetic inhibition of PVNCRH neurons would restore stress response in female mice with a history of alcohol drinking in the looming disk test, which mimics an approaching predator threat. Accordingly, inhibition of PVNCRH neurons reduced active escape in hM4Di alcohol history mice only. This study indicates that stress-responsive PVNCRH neurons in females are particularly affected by a history of alcohol consumption. Interestingly, women have indicated an increase in heavy alcohol use to cope with stress (Rodriguez et al., 2020), perhaps pointing to a potential underlying mechanism in alcohol-mediated changes to PVNCRH neurons that alter stress response.SIGNIFICANCE STATEMENT Paraventricular nucleus of the hypothalamus neurons that release corticotropin releasing hormone (PVNCRH) are vital for stress response. These neurons have been understudied in relation to alcohol and withdrawal despite profound relations between stress, alcohol use disorders (AUD), and relapse. In this study, we use a variety of techniques to show that acute withdrawal from a history of alcohol impacts peripheral stress response, PVNCRH neurons, and behavior. Specifically, PVNCRH are in a hyperactive state during withdrawal, which drives an increase in active stress coping behaviors in female mice only. Understanding how alcohol use and withdrawal affects stress responding PVNCRH neurons may contribute to finding new potential targets for the treatment of alcohol use disorder.

Induction of mitophagy via ROS-dependent pathway protects copper-induced hypothalamic nerve cell injury

Copper (Cu) is one of the essential trace elements in the body, but excessive amounts of Cu harm multiple organs and tissues such as liver, kidneys, testis, ovaries, and brain. However, the mechanism of hypothalamic neurotoxicity induced by Cu is still unknown. This study examined the relationship between reactive oxygen species (ROS) and mitophagy in mouse hypothalamus treated with high Cu. The results demonstrated that high levels of copper sulfate (CuSO4) could cause histopathological and neuronal changes in the mouse hypothalamus, produce a large amount of ROS, induce mitophagy, and lead to an imbalance of mitochondrial fusion/fission. The main manifestations are an increase in the expression levels of LC3-II/LC3-I, p62, DRP1, and FIS1, and a decrease in the expression levels of MFN1 and MFN2. Cu can induce mitophagy also was confirmed by LC3 co-localization with TOMM20 (mitochondrial marker). Next, the effect of oxidative stress on CuSO4-induced mitophagy was demonstrated. The results showed that ROS inhibitor N-acetylcysteine (NAC) diminished CuSO4-induced mitophagy and reversed the disturbance of mitochondrial dynamics. Additionally, a study was carried out to evaluate the role of mitophagy in CuSO4-induced hypothalamic injury. The inhibition of mitophagy using mitophagy inhibitor (Mdivi-1) decreased cell viability and promoted CuSO4-inhibited mitochondrial fusion. The aforementioned results suggested that CuSO4 induced mitophagy via oxidative stress in N38 cells and mouse hypothalamus, and that the activation of mitophagy might generate protective mechanisms by alleviating Cu-induced mitochondrial dynamics disorder. This study provided a novel approach and theoretical basis for studying and preventing Cu neurotoxicity.

Changes of Signaling Pathways in Hypothalamic Neurons with Aging.

The hypothalamus is an important regulator of autonomic and endocrine functions also involved in aging regulation. The aging process in the hypothalamus is accompanied by disturbed intracellular signaling including insulin/insulin-like growth factor-1 (IGF-1)/growth hormone (GH), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT)/the mammalian target of rapamycin (mTOR), mitogen activated protein kinase (MAPK), janus kinase (JAK)/signal transducer and activator of transcription (STAT), AMP-activated protein kinase (AMPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB), and nitric oxide (NO). In the current review, I have summarized the current understanding of the changes in the above-mentioned pathways in aging with a focus on hypothalamic alterations.

A clock-dependent brake for rhythmic arousal in the dorsomedial hypothalamus

Circadian clocks generate rhythms of arousal, but the underlying molecular and cellular mechanisms remain unclear. In Drosophila, the clock output molecule WIDE AWAKE (WAKE) labels rhythmic neural networks and cyclically regulates sleep and arousal. Here, we show, in a male mouse model, that mWAKE/ANKFN1 labels a subpopulation of dorsomedial hypothalamus (DMH) neurons involved in rhythmic arousal and acts in the DMH to reduce arousal at night. In vivo Ca2+ imaging reveals elevated DMHmWAKE activity during wakefulness and rapid eye movement (REM) sleep, while patch-clamp recordings show that DMHmWAKE neurons fire more frequently at night. Chemogenetic manipulations demonstrate that DMHmWAKE neurons are necessary and sufficient for arousal. Single-cell profiling coupled with optogenetic activation experiments suggest that GABAergic DMHmWAKE neurons promote arousal. Surprisingly, our data suggest that mWAKE acts as a clock-dependent brake on arousal during the night, when mice are normally active. mWAKE levels peak at night under clock control, and loss of mWAKE leads to hyperarousal and greater DMHmWAKE neuronal excitability specifically at night. These results suggest that the clock does not solely promote arousal during an animal’s active period, but instead uses opposing processes to produce appropriate levels of arousal in a time-dependent manner.

SAT047 Regulation Of The Insulin Receptor And The Insulin-like Growth Factor 1 Receptor By miR-322-5p, A miR-16 Family Member, In Hypothalamic Neuronal Models

Abstract Disclosure: W. He: None. N. Loganathan: None. K.W. Mak: None. E. McIlwraith: None. D.D. Belsham: None. Insulin signals through the insulin receptor (INSR) and the insulin-like growth factor 1 receptor (IGF1R) in hypothalamic neurons to control food intake and peripheral metabolism. A contributor to obesity, and subsequent comorbidities such type 2 diabetes and heart disease, is the development of cellular insulin resistance in hypothalamic neurons. However, the molecular changes to neuronal insulin signaling remain to be fully elucidated. MicroRNAs (miRNAs) inhibit translation of specific mRNAs; thus, this study aimed to understand the involvement of miRNAs in the regulation of insulin signaling and resistance in hypothalamic neurons. To profile miRNAs expressed in hypothalamic neurons, RNA from the whole hypothalami of 14-week-old CD1 male mice (n = 4), as well as the immortalized hypothalamic neuronal cell lines mHypoE-46 (n = 3) and mHypoA-59 (n = 3), each co-expressing neuropeptide Y (NPY) and agouti-related peptide (AgRP), were assessed using the Affymetrix GeneChip miRNA 4.0 Array. Notably, miR-16 family members, including miR-16-5p, miR-15b-5p, and miR-322-5p, were among the most highly expressed miRNAs in each case. In the mHypoA-59 neurons, overexpression of miR-322-5p for 24 hours decreased the mRNA levels of Igf1r (-26.1%; p = 0.0007; n = 4) and the protein level of INSR-beta (-31.8%; p = 0.0023). These results suggest that the miR-16 family plays an inhibitory role in insulin signaling in hypothalamic neurons. To study the involvement of miRNAs in hyperinsulinemia-induced neuronal insulin resistance, the mHypoE-46 neurons were treated with 100 nM insulin for 24 hours to induce cellular insulin resistance, as characterized by decreased INSR-beta protein (-96.3%; p < 0.0001; n = 4) and a resulting decrease in insulin-induced phosphorylation of protein kinase B (AKT) (-67.6%; p = 0.01; n = 4). GeneChip miRNA array analysis showed that insulin overexposure disrupted the expression of 48 miRNAs (p < 0.05, n = 3), including the upregulation of miR-18a-3p, mir-322, miR-494-3p, and miR-671-3p. Upon RT-qPCR validation (n = 3), we established that prolonged (24 hours), but not acute (1-6 hours), insulin exposure upregulated miR-18a-3p (+62%; p = 0.0104), miR-671-3p (+111%; p = 0.0079), and miR-1983 (+97%; p = 0.0181). miR-671-3p, miR-494-3p, and miR-18a-3p have been shown to decrease phosphatase and tensin homolog (PTEN) levels, which can promote neuronal insulin resistance based on bioinformatic analysis. Overall, these results suggest hyperinsulinemia disrupts the expression of specific miRNAs in hypothalamic neurons to promote cellular insulin resistance. Knowledge derived from these studies will provide insight into hypothalamus-derived miRNAs that could be targeted for miRNA-based diagnostics and therapeutics for early central insulin resistance in humans.(Supported by the CRC, CIHR, NSERC, EndoSoc, and BBDC) Presentation: Saturday, June 17, 2023

SAT592 Sexually Dimorphic Modulation Of Arcuate Kisspeptin Neurons Activity In Response To NPY

Abstract Disclosure: N.D. Mansano: None. R. Frazao: None. Kisspeptin neurons are part of an intricate brain circuit that receives neuronal inputs related tonutritional status from at least three neuronal populations, including NPY/AgRP and POMC neurons of the arcuate nucleus of the hypothalamus (ARH) and cells in the ventral premammillary nucleus. Its well-known action on the HPG axis, hypothalamic kisspeptin neurons also modulate the activity of specific neurons of the paraventricular and the dorsomedial nuclei of the hypothalamus, regions involved in the regulation of appetite and energy expenditure. However, it is not completely elucidated if NPY can influence the HPG axis through the modulation of kisspeptin neuron activity. To determine the NPY effect in the hypothalamic kisspeptin neurons we performed whole-cell patch-clamp recordings. The hypothalamic slices were obtained from the adult Kiss1/hrGFP female (diestrus-stage) or male mice. Kisspeptin cells located in the arcuate nucleus of the hypothalamus (ARHkisspeptin) and at the anteroventral periventricular and rostral periventricular nuclei (AVPV/PeNkisspeptin) were recorded. On female mice, ARHkisspeptin neurons exhibited a rest membrane potential (RMP) average of -52.5±2.5 mV (-40 to -62 mV) and 1.3±0.2 GΩ input resistance (IR). NPY induced the hyperpolarization of 45% of the ARHkisspeptin neurons (n= 9 of 20 cells, out of 9 mice). ARHkisspeptin neuron’s RMP hyperpolarization was followed by a significant decrease in IR and frequency of action potentials (fAPS). In the AVPV/PeNkisspeptin neurons showed RMP average of -69.6±1.9 mV (-51 to - 88 mV) and IR of 0.8±0.09 GΩ (n=18 cells out of 9 mice). No significant NPY-induced effect was noted when recordings were performed on AVPV/PeNkisspeptin cells from female mice. To elucidate if the ARHkisspeptin neuron’s hyperpolarization depends on action potentials (APs) mediated by synaptic transmission we further evaluated NPY effects in the presence of TTX and amino acid receptor antagonists (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10μM), DL-2-amino-5-phosphonopentanoic acid (AP5, 50μM), and picrotoxin (50μM). NPY induced no effect on ARHkisspeptin neuron’s RMP, and IR in the presence of TTX and amino acid receptor antagonists. Suggesting that NPY-induced hyperpolarization of ARHkisspeptin neurons is an indirect effect. To further verify whether sex must be considered as a biological variable to study the NPY effect, we recorded ARHkisspeptin cells from male mice. ARHkisspeptin neurons recorded from male mice exhibited RPM average of -55.6±1.5 (-45 to -66 mV) and IR of 1.5±0.15 GΩ (n= 13 cells out of 10 mice). Interestingly, NPY induced no effect on RMP, IR, or fAPs in male animals. In conclusion, our results suggest that NPY-induced hyperpolarization of ARHkisspeptin cells depends on AP’s mediate synaptic transmission, as a sex-specific effect. Presentation: Saturday, June 17, 2023

OR17-06 Clinical And Mechanistic Insight For The Therapeutic Potential Of Intranasal Kisspeptin Administration To Treat Reproductive Disorders In Humans

Abstract Disclosure: E.G. Mills: None. M. Swedrowska: None. V. Delli: None. K. Chachlaki: None. M. Silva: None. L. Decoster: None. G. Ternier: None. L. Thurston: None. M. Phylactou: None. B. Patel: None. L. Yang: None. S.A. Clarke: None. B. Muzi: None. E.C. Alexander: None. M. Choudhury: None. P. Bech: None. A. Abbara: None. B. Forbes: None. P. Giacobini: None. V. Prevot: None. A.N. Comninos: None. W.S. Dhillo: None. Background: Kisspeptin is a key regulator of hypothalamic GnRH neurons with emerging potential to treat reproductive, psychosexual and bone disorders. However, current therapeutic application is limited to the subcutaneous or intravenous routes, which presents significant barriers to further development. Alternative delivery routes could overcome this and capitalise on the clinical utility of kisspeptin-based therapeutics. Herein, we comprehensively examine the translational potential of intranasal kisspeptin administration for the first time using a series of human, rodent and pharmaceutical studies. Methods:Human studies: Healthy men (n=12) and a patient group of women with Hypothalamic Amenorrhoea (HA) (n=5) completed a randomised, double-blind, crossover, placebo-controlled study investigating the acute effects of intranasal kisspeptin-54 administration (doses 3.2-25.6nmol/kg [healthy men] and 12.8nmol/kg [women with HA] vs 0.9% saline placebo). Plasma kisspeptin and serum reproductive hormones were measured every 15mins for 4hrs. Thereafter, we conducted rodent studies in adult C57BL/6J male mice to elucidate the possible mechanism by which intranasal kisspeptin induces reproductive hormone release, using intranasal administration of fluorescently-tagged kisspeptin-54 and a series of c-Fos experiments. From a medicines development perspective, we undertook pharmaceutical studies to evaluate the chemical stability of kisspeptin-54 in solution for nasal delivery in real-time. Results:Human studies: in healthy men, intranasal kisspeptin dose-dependently increased plasma kisspeptin at doses 6.4-25.6nmol/kg (p<0.01 for all doses vs placebo), with the maximal rises achieved within 15-30 minutes. Correspondingly, intranasal kisspeptin acutely and potently increased serum LH at doses 6.4-25.6nmol/kg (p<0.01 all doses vs placebo) with maximal rises at 30 minutes. Likewise, in women with HA, intranasal kisspeptin acutely increased plasma kisspeptin (p=0.004 vs placebo) and serum LH (p=0.004 vs placebo). Animal studies: To provide mechanistic insight, we demonstrate in male mice that GnRH neurons located in the olfactory bulb express kisspeptin receptors and that intranasal administration of fluorescently-tagged kisspeptin-54 binds to the olfactory epithelium. Pharmaceutical studies: Kisspeptin-54 in 0.9% saline remained within pharmaceutically accepted limits for stability for up to 60 days at 4°C demonstrating realistic pharmaceutical potential. Conclusion: We identify robust clinical effects and provide mechanistic and pharmaceutical data for intranasal delivery as a novel, non-invasive, safe and effective kisspeptin administration route for the management of common reproductive disorders that would be far preferable to patients and clinicians and so transform the ongoing rapid development of kisspeptin-based therapeutics. Presentation: Saturday, June 17, 2023

FRI384 Sterilization Of Female Dogs By A Neonatal Treatment Of Estrogen-Releasing Implants

Abstract Disclosure: C. Park: None. P. Lin: None. S. Zhou: None. R.A. Hess: None. C. Ko: None. Hypothalamic Kisspeptin neurons that control the GnRH neuron activity are known to be a core regulator of the reproductive axis. Loss of the Kisspeptin-1 gene in these neurons results in infertility. Recent reports showed that inhibition of Kisspeptin neuron development by daily injection of 17β-estradiol benzoate (EB, 0.5 mg/day), a long-lasting estrogen, to neonatal female rats for 10 days causes sterility. We aim to develop a single injection solution for achieving sterilization in female dogs by targeting developing Kisspeptin neurons. In this study, we tested a working hypothesis that, in female dogs, extended exposure to EB for 2 weeks after birth by slow-releasing implants will result in sterility. This hypothesis was proposed based on our proof-of-concept study in which neonatal treatment of female rats with implants that contained 0.3 mg EB decreased the number of Kisspeptin neurons, and made them infertile permanently. To test the hypothesis in dogs, pellets that contained 0.5 mg (n=3) or 1.0 mg EB (n=2) and were designed to release EB for 2-3 weeks were subcutaneously implanted in female beagle dogs on postnatal day 6 (PND6). Intact dogs (n=4) were used as controls. The indices for female fertility (estrous cyclicity, ovulation) were assessed by daily vulva examination (swelling, discharge) and monthly measurement of serum progesterone levels. In addition, when a dog exhibited signs of estrus, the dog was bred with fertility-proven male dogs. During the 3 years of the study period, control dogs showed a minimum of 3 reproductive cycles (estrus, ovulation), and successfully produced puppies each time. Treated dogs displayed dose-dependent fertility outcomes; none of the EB 1.0 mg-treated dogs exhibited estrus nor had elevated serum progesterone levels, while two dogs out of the three EB 0.5 mg-treated dogs remained infertile. The other dog of the EB 0.5 mg group showed estrus signs during the study period and produced a litter when bred with a proven male. In the second experiment, implants that contained 0.5 mg (n=2) or 1.0 mg EB (n=3) were injected into female puppies on PND1. They are currently 1-1.2 years of age, and none have shown estrus/ovulation signs so far. Our study demonstrates that neonatal treatment of EB by slow-releasing implants sterilizes female beagle dogs. During the study period, the complete blood cell count and serum chemistry of treated dogs were within the normal range. This study shows that the non-surgical solution using EB implants is a promising approach to replace the current practice of sterilizing pets with surgical methods. Supported by NSF SBIR grant (#2052603) Presentation: Friday, June 16, 2023

SAT424 Neuroendocrine And Developmental Impacts Of Early Exposure To Estrogenic Endocrine Disruptors

Abstract Disclosure: M. Streifer: None. S. Mendez: None. R. Raval: None. L. Thompson: None. A.C. Gore: None. Polychlorinated biphenyls (PCBs) are a class of endocrine disrupting chemical (EDC), exposure to which during early development can result in a variety of neuroendocrine and reproductive abnormalities. Hypothalamic kisspeptin neurons in the anteroventral periventricular nucleus (AVPV) and KNDy (Kisspeptin-Neurokinin B-Dynorphin expressing) neurons in the arcuate nucleus (ARC) are involved in reproductive development, maturation, and success; dysfunctions in kisspeptin signaling can lead to hypogonadotropic hypogonadism and sub- or infertility. KNDy and kisspeptin neurons develop under the influence of gonadal hormones, notably estradiol, and are vulnerable to early exposure to estrogenic EDCs. In this experiment male and female rats were perinatally exposed to the weakly estrogenic PCB mixture Aroclor 1221 (A1221) to determine if and how altered kisspeptin signaling in the ARC and AVPV affects reproductive development. Using RNAscope, a novel in situ hybridization technique, we are exploring if changes in the number of KNDy and kisspeptin neurons or RNA expression of kisspeptin and regulatory peptides neurokinin B and dynorphin are potential mechanisms of the increased incidence of reproductive disorders associated with estrogenic PCB exposure. A1221 exposure did not alter the number of kisspeptin-expressing neurons in the AVPV, though quantification of RNA expression and analysis in the ARC are still ongoing. Serum LH, FSH, estradiol, and testosterone were measured as they are involved in the kisspeptin signaling pathway. In A1221 exposed females, serum LH and FSH were decreased, and estradiol was increased in early life (postnatal day 8). A1221 exposed males had decreased serum LH at a prepubertal time point (postnatal day 30), but FSH and testosterone were unaffected by treatment. Developmental markers that could be indicative of dysfunctions in kisspeptin and KNDy neuron function were monitored. A1221 exposure did not cause any obvious abnormal developmental delays in males or females. Moving forward, we plan on further exploring the effects of developmental A1221 exposure in the AVPV and ARC through gene expression profiling. Presentation: Saturday, June 17, 2023

SAT607 Targeted Modulation Of Kisspeptin Neurons Improves Hyperandrogenism And Hyperactive LH Secretion In A Pre-clinical PCOS-like Mouse Model: Implications For Novel Therapeutics In PCOS Women

Abstract Disclosure: E. Coutinho: Employee; Self; Crinetics. L.A. Esparza: None. A.S. Kauffman: Consulting Fee; Self; Crinetics. Polycystic ovary syndrome (PCOS), a common reproductive disorder in women, is characterized by hyperandrogenemia, chronic anovulation, and/or cystic ovarian follicles. Another common hallmark of PCOS is LH hyper-pulsatility, believed to be driven by hyperactive GnRH neurons, but the reason for the increased GnRH secretion still remains unclear. We previously developed a PCOS-like mouse model using chronic letrozole (LET; aromatase inhibitor) and reported that LET females demonstrated multiple PCOS-like phenotypes, including polycystic ovaries, anovulation, hyperandrogenemia, enlarged ovaries, and hyperactive LH pulse secretion. Given the proposed role of hypothalamic arcuate kisspeptin neurons as the GnRH pulse generator, we determined that LET females have markedly elevated Kiss1 and Tac2 expression and increased Kiss1 neuronal activation in the arcuate nucleus, correlating with their hyper-pulsatile LH secretion. Thus, in the LET PCOS-like condition, and perhaps in PCOS women, increased hypothalamic kisspeptin and NKB neuron activity may be fundamental contributors to the hyperactive LH secretion and downstream hyperandrogenemia. We next tested this possibility using chemogenetics in transgenic PCOS-like mice to acutely and chronically suppress kisspeptin neuron activity. Acute inhibition of kisspeptin neurons successfully lowered abnormally high, rapid in vivo LH pulse secretion in PCOS-like females. Likewise, chronic in vivo suppression of endogenous kisspeptin neuron activity for several weeks dramatically lowered both circulating LH and T levels, and reduced ovarian weights, in females previously displaying a PCOS-like phenotype, with a trend towards improvement of overweight phenotype. These data support the hypothesis that overactive kisspeptin neurons may be one possible driver of neuroendocrine PCOS-like phenotypes. Importantly, these findings suggest that modulation of kisspeptin neurons may be a viable, novel therapeutic target to treat hyperandrogenism and hyperactive LH pulsatility in PCOS women. Indeed, although identical studies have not yet been done in humans, our findings complement recent clinical investigations using NKB receptor antagonists or dynorphin analogs to lower LH pulse secretion in PCOS women and other PCOS-like animal models. Presentation: Saturday, June 17, 2023