Characteristics of Neurokinin-3 Receptor and Its Binding Sites by Mutational Analysis

NKB (Neurokinin B) is already known to play a crucial role in fish reproduction, but little is known about the structure and function of NKB receptors. Based on an in silico model of the tilapia NKB receptor Tachykinin 3 receptor a (tiTac3Ra) found in the current study, we determined the key residues involved in binding to tilapia NKB and its functional homologue NKF (Neurokinin F). Despite studies in humans suggesting the crucial role of F2516.44 and M2897.43 in NKB binding, no direct peptide interaction was observed in tilapia homologs. In-silico, Ala mutations on residues F2516.44 and M2897.43 did not influence binding affinity, but significantly affected the stability of tiTac3Ra. Moreover, in vitro studies indicated them to be critical to tiNKB/tiNKF-induced receptor activity. The binding of NKB antagonists to tiTac3Ra both in-vitro and in vivo inhibits FSH (follicle stimulating hormone) and LH (luteinizing hormone) release and sperm production in mature tilapia males. Non-peptide NKB antagonist SB-222200 had a strong inhibitory effect on the Tac3Ra activation. SB-222200 also decreased LH plasma levels; two hours post intraperitoneal injection, changed sperm volume and the ratios of the different stages along the spermatogenesis in tilapia testes.

Localization of kisspeptin, NKB, and NK3R in the hypothalamus of gilts treated with the progestin altrenogest

Mechanisms in the brain controlling secretion of gonadotropin hormones in pigs, particularly luteinizing hormone (LH), are poorly understood. Kisspeptin is a potent LH stimulant that is essential for fertility in many species, including pigs. Neurokinin B (NKB) acting through neurokinin 3 receptor (NK3R) is involved in kisspeptin-stimulated LH release, but organization of NKB and NK3R within the porcine hypothalamus is unknown. Hypothalamic tissue from ovariectomized (OVX) gilts was used to determine the distribution of immunoreactive kisspeptin, NKB, and NK3R cells in the arcuate nucleus (ARC). Almost all kisspeptin neurons coexpressed NKB in the porcine ARC. Immunostaining for NK3R was distributed throughout the preoptic area (POA) and in several hypothalamic areas including the periventricular and retrochiasmatic areas but was not detected within the ARC. There was no colocalization of NK3R with gonadotropin-releasing hormone (GnRH), but NK3R-positive fibers in the POA were in close apposition to GnRH neurons. Treating OVX gilts with the progestin altrenogest decreased LH pulse frequency and reduced mean circulating concentrations of LH compared with OVX control gilts (P < 0.01), but the number of kisspeptin and NKB cells in the ARC did not differ between treatments. The neuroanatomical arrangement of kisspeptin, NKB, and NK3R within the porcine hypothalamus confirm they are positioned to stimulate GnRH and LH secretion in gilts, though differences with other species exist. Altrenogest suppression of LH secretion in the OVX gilt does not appear to involve decreased peptide expression of kisspeptin or NKB.

Neurokinin 3 Receptor Effects on Cognitive Behaviour in a Rat Model of Alzheimer's Disease

Alzheimer's disease (AD) is accepted as a form of progressive and irreversible dementia. It is known that cholinergic systems are commonly affected in AD. Neurokinin 3 receptor (NK3R) is involved in learning and memory related processes. Activation of NK3R is known to facilitate the release of many neurotransmitters such as acetylcholine (Ach), dopamine (DA), noradrenaline (NA). Based on this information, hypothesis of the study that NK3R agonism can have positive effects on behavioral and learning parameters through cholinergic and catecholaminergic mechanisms. The aim of this study was to investigate the effects of NK3R agonist senktide on cognitive and neurobehavioral mechanisms in model of AD.50 adult male Wistar albino rats were obtained; Control, AD, Control+NK3R agonist, AD+NK3R agonist, AD+NK3R agonist+antagonist groups. AD model was established by administering Aβ1-42 intracerebroventricularly. Following NK3R agonist+antagonist injections, open field (OF) and Morris water maze (MWM) were applied for behavioral and learning parameters. Hippocampus and cortex tissues were extracted. Analysis of cholinergic mechanisms from these tissues were performed by ELISA method.Group-time effect was significant in OF (p<0.05). Distance moved parameter was significant between groups in MWM (p<0.05). There was a significant difference between groups in AChE and ChAT levels (p<0.05). DA concentrations of brainstem samples were significant (p<0.05). There was no significant difference in NA concentration (p>0.05). NK3R agonists were found to be effective in improving cognitive functions in rats with AD pathology. It has been observed that positive effects on learning and memory performances can be mediated by cholinergic mechanisms.

Randomized Controlled Trial of Neurokinin 3 Receptor Antagonist Fezolinetant for Treatment of Polycystic Ovary Syndrome

Context Polycystic ovary syndrome (PCOS), a highly prevalent endocrine disorder characterized by hyperandrogenism, is the leading cause of anovulatory infertility. Objective This proof-of-concept study evaluated clinical efficacy and safety of the neurokinin 3 (NK3) receptor antagonist fezolinetant in PCOS. Design This was a phase 2a, randomized, double-blind, placebo-controlled, multicenter study (EudraCT 2014-004409-34). Setting The study was conducted at 5 European clinical centers. Patients Women with PCOS participated in the study. Intervention Interventions included fezolinetant 60 or 180 mg/d or placebo for 12 weeks. Main Outcome Measure The primary efficacy endpoint was change in total testosterone. Gonadotropins, ovarian hormones, and safety/tolerability were also assessed. Results Seventy-three women were randomized, and 64 participants completed the study. Adjusted mean (SE) changes in total testosterone from baseline to week 12 for fezolinetant 180 and 60 mg/d were −0.80 (0.13) and −0.39 (0.12) nmol/L versus −0.05 (0.10) nmol/L with placebo (P&lt;0.0001 and P&lt;0.05, respectively). Adjusted mean (SE) changes from baseline in luteinizing hormone (LH) for fezolinetant 180 and 60 mg/d were −10.17 (1.28) and −8.21 (1.18) versus −3.16 (1.04) IU/L with placebo (P&lt;0.0001 and P=0.0022); corresponding changes in follicle-stimulating hormone (FSH) were −1.46 (0.32) and −0.92 (0.30) versus −0.57 (0.26) IU/L (P=0.0336 and P=0.3770), underpinning a dose-dependent decrease in the LH-to-FSH ratio versus placebo (P&lt;0.001). Circulating levels of progesterone and estradiol did not change significantly versus placebo (P&gt;0.1). Fezolinetant was well tolerated. Conclusions Fezolinetant had a sustained effect to suppress hyperandrogenism and reduce the LH-to-FSH ra

Neurokinin 3 receptor antagonism ameliorates key metabolic features in a hyperandrogenic PCOS mouse model

Polycystic ovary syndrome (PCOS) is a prevalent endocrine condition characterised by a range of endocrine, reproductive and metabolic abnormalities. At present, management of women with PCOS is suboptimal as treatment is only symptomatic. Clinical and experimental advances in our understanding of PCOS etiology support a pivotal role for androgen neuroendocrine actions in PCOS pathogenesis. Hyperandrogenism is a key PCOS trait and androgen actions play a role in regulating the kisspeptin-/neurokinin B-/dynorphin (KNDy) system. This study aimed to investigate if targeted antagonism of neurokinin B signalling through the neurokinin 3 receptor (NK3R) would reverse PCOS traits in a dihydrotestosterone (DHT)-induced mouse model of PCOS. After 3 months, DHT exposure induced key reproductive PCOS traits of cycle irregularity and ovulatory dysfunction, and PCOS-like metabolic traits including increased body weight; white and brown fat pad weights; fasting serum triglyceride and glucose levels and blood glucose iAUC. Treatment with a NK3R antagonist (MLE4901) did not impact the observed reproductive defects. In contrast, following NK3R antagonist treatment, PCOS-like females displayed decreased total body weight, adiposity and adipocyte hypertrophy, but increased respiratory exchange ratio, suggesting NK3R antagonism altered the metabolic status of the PCOS-like females. NK3R antagonism did not improve circulating serum triglyceride or fasted glucose levels. Collectively, these findings demonstrate that NK3R antagonism may be beneficial in the treatment of adverse metabolic features associated with PCOS and support neuroendocrine targeting in the development of novel therapeutic strategies for PCOS.