Melanin-concentrating hormone neurons contribute to dysregulation of rapid eye movement sleep in narcolepsy.

The lateral hypothalamus contains neurons producing orexins that promote wakefulness and suppress REM sleep as well as neurons producing melanin-concentrating hormone (MCH) that likely promote REM sleep. Narcolepsy with cataplexy is caused by selective loss of the orexin neurons, and the MCH neurons appear unaffected. As the orexin and MCH systems exert opposing effects on REM sleep, we hypothesized that imbalance in this REM sleep-regulating system due to activity in the MCH neurons may contribute to the striking REM sleep dysfunction characteristic of narcolepsy. To test this hypothesis, we chemogenetically activated the MCH neurons and pharmacologically blocked MCH signaling in a murine model of narcolepsy and studied the effects on sleep-wake behavior and cataplexy. To chemoactivate MCH neurons, we injected an adeno-associated viral vector containing the hM3Dq stimulatory DREADD into the lateral hypothalamus of orexin null mice that also express Cre recombinase in the MCH neurons (MCH-Cre::OX-KO mice) and into control MCH-Cre mice with normal orexin expression. In both lines of mice, activation of MCH neurons by clozapine-N-oxide (CNO) increased rapid eye movement (REM) sleep without altering other states. In mice lacking orexins, activation of the MCH neurons also increased abnormal intrusions of REM sleep manifest as cataplexy and short latency transitions into REM sleep (SLREM). Conversely, a MCH receptor 1 antagonist, SNAP 94847, almost completely eliminated SLREM and cataplexy in OX-KO mice. These findings affirm that MCH neurons promote REM sleep under normal circumstances, and their activity in mice lacking orexins likely triggers abnormal intrusions of REM sleep into non-REM sleep and wake, resulting in the SLREM and cataplexy characteristic of narcolepsy.

Development of a Novel Carbon-11 Labeled PET Radioligand for Melanin- Concentrating Hormone Receptor 1.

BACKGROUND AND OBJECTIVE: Melanin-concentrating hormone (MCH) is an attractive target for antiobesity agents and many drug discovery programs have been dedicated to identify smallmolecule antagonists of melanin-concentrating hormone receptor 1 (MCHR1). The aim of this study was to develop a positron emission tomography (PET) tracer for MCHR1 for translation of preclinical pharmacology to clinic to enhance success rate of drug discovery programs. METHODS: We identified 4-(cyclopropylmethoxy)-N-[8-methyl-3-({[(1-methyl-1H-pyrrol-2-yl)methyl] amino}ethyl)quinolin-7-yl]benzamide (Compound II) from Takeda MCHR1 antagonist library by utilizing binding affinity, log D value, physicochemical parameters ideal for a central nerve system agent, and synthetic feasibility of corresponding carbon-11 labeled radioligands as selection parameters for tracer candidates. RESULTS: In the rat PET study, [11C] Compound II showed clear uptake in the caudate/putamen with the pretreatment of cyclosporine A and its uptake was higher than that in the cerebellum where expression of MCHR1 was reported to be low. CONCLUSION: In summary, [11C]Compound II is a promising lead compound for developing a suitable MCHR1 PET radioligand. [11C]Compound II, in combination with cyclosporine A, could be used as a research tool to visualize and quantify MCHR1 in rodents.

Novel Neuroprotective Effects of Melanin-Concentrating Hormone in Parkinson's Disease.

Acupuncture has shown the therapeutic effect on various neurodegenerative disorders including Parkinson's disease (PD). While investigating the neuroprotective mechanism of acupuncture, we firstly found the novel function of melanin-concentrating hormone (MCH) as a potent neuroprotective candidate. Here, we explored whether hypothalamic MCH mediates the neuroprotective action of acupuncture. In addition, we aimed at evaluating the neuroprotective effects of MCH and elucidating underlying mechanism in vitro and in vivo PD models. First, we tested whether hypothalamic MCH mediates the neuroprotective effects of acupuncture by challenging MCH-R1 antagonist (i.p.) in mice PD model. We also investigated whether MCH has a beneficial role in dopaminergic neuronal protection in vitro primary midbrain and human neuronal cultures and in vivo MPTP-induced, Pitx3-/-, and A53T mutant mice PD models. Transcriptomics followed by quantitative PCR and western blot analyses were performed to reveal the neuroprotective mechanism of MCH. We first found that hypothalamic MCH biosynthesis was directly activated by acupuncture treatment and that administration of an MCH-R1 antagonist reverses the neuroprotective effects of acupuncture. A novel finding is that MCH showed a beneficial role in dopaminergic neuron protection via downstream pathways related to neuronal survival. This is the first study to suggest the novel neuroprotective action of MCH as well as the involvement of hypothalamic MCH in the acupuncture effects in PD, which holds great promise for the application of MCH in the therapy of neurodegenerative diseases.

Effect of intrahippocampal administration of anti-melanin-concentrating hormone on spatial food-seeking behavior in rats.

Melanin-concentrating hormone (MCH) is a hypothalamic peptide that plays a critical role in the regulation of food intake and energy metabolism. In this study, we investigated the potential role of dense hippocampal MCH innervation in the spatially oriented food-seeking component of feeding behavior. Rats were trained for eight sessions to seek food buried in an arena using the working memory version of the food-seeking behavior (FSB) task. The testing day involved a bilateral anti-MCH injection into the hippocampal formation followed by two trials. The anti-MCH injection did not interfere with the performance during the first trial on the testing day, which was similar to the training trials. However, during the second testing trial, when no food was presented in the arena, the control subjects exhibited a dramatic increase in the latency to initiate digging. Treatment with an anti-MCH antibody did not interfere with either the food-seeking behavior or the spatial orientation of the subjects, but the increase in the latency to start digging observed in the control subjects was prevented. These results are discussed in terms of a potential MCH-mediated hippocampal role in the integration of the sensory information necessary for decision-making in the pre-ingestive component of feeding behavior.

Prodepressive effect induced by microinjections of MCH into the dorsal raphe: time course, dose dependence, effects on anxiety-related behaviors, and reversion by nortriptyline.

Melanin-concentrating hormone (MCH) administered within the rat dorsal raphe nucleus (DRN) has been shown to elicit prodepressive behaviors in the forced-swim test. The present study was designed to evaluate the time course (30 and 60 min) and dose dependence (25-100 ng) of this effect, and whether it would be antagonized by an intra-DRN microinjection of the MCH-1 receptor antagonist ATC0175 (ATC, 1 mmol/l) or intraperitoneal pretreatment with the noradrenergic antidepressant nortriptyline (20 mg/kg). The results showed that the behavioral effect of MCH was time and dose dependent as immobility was increased, and climbing decreased, only by the 50 ng MCH dose at T30. The effect was mediated by MCH-1 receptors as a significant blockade of this behavioral response was observed in ATC-pretreated animals. ATC did not by itself modify animal behavior. Nortriptyline also prevented the prodepressive-like effect of MCH. Concomitantly, the effect of MCH (50 ng) at T30 on anxiety-related behaviors was assessed using the elevated plus-maze. Interestingly, these behaviors were unchanged. In conclusion, MCH administration within the DRN elicits, through the MCH-1 receptor, a depression-related behavior that is not accompanied by changes in anxiety and that is prevented by a noradrenergic antidepressant.

Synthesis and structure-activity relationship of naphtho[1,2-b]furan-2-carboxamide derivatives as melanin concentrating hormone receptor 1 antagonists.

The discovery that novel naphtho[1,2-b]furan-2-carboxamides containing linked piperidinylphenylacetamide groups serve as melanin concentrating hormone receptor 1 (MCH-R1) antagonists is described. An extensive structure-activity relationship (SAR) study, probing members of this family that contain a variety of aryl and heteroaryl groups at C-5 of the naphtho[1,2-b]furan-2-carboxamide skeleton and having different chain linker lengths, led to the identification of the 5-(4-pyridinyl) substituted analog 10b as a highly potent MCH-R1 antagonist with an IC50 value of 3 nM. This substance also displays good metabolic stability and it does not significantly inhibit cytochrome P450 (CYP450) enzymes. However, 10b has unacceptable oral bioavailability.

Anti-melanin-concentrating hormone treatment attenuates chronic experimental colitis and fibrosis.

Fibrosis represents a major complication of several chronic diseases, including inflammatory bowel disease (IBD). Treatment of IBD remains a clinical challenge despite several recent therapeutic advances. Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide shown to regulate appetite and energy balance. However, accumulating evidence suggests that MCH has additional biological effects, including modulation of inflammation. In the present study, we examined the efficacy of an MCH-blocking antibody in treating established, dextran sodium sulfate-induced experimental colitis. Histological and molecular analysis of mouse tissues revealed that mice receiving anti-MCH had accelerated mucosal restitution and lower colonic expression of several proinflammatory cytokines, as well as fibrogenic genes, including COL1A1. In parallel, they spared collagen deposits seen in the untreated mice, suggesting attenuated fibrosis. These findings raised the possibility of perhaps direct effects of MCH on myofibroblasts. Indeed, in biopsies from patients with IBD, we demonstrate expression of the MCH receptor MCHR1 in α-smooth muscle actin(+) subepithelial cells. CCD-18Co cells, a primary human colonic myofibroblast cell line, were also positive for MCHR1. In these cells, MCH acted as a profibrotic modulator by potentiating the effects of IGF-1 and TGF-ß on proliferation and collagen production. Thus, by virtue of combined anti-inflammatory and anti-fibrotic effects, blocking MCH might represent a compelling approach for treating IBD.

Anti-obesity effects of the combined administration of CB1 receptor antagonist rimonabant and melanin-concentrating hormone antagonist SNAP-94847 in diet-induced obese mice.

OBJECTIVE: Current anti-obesity monotherapies have proven only marginally effective and are often accompanied by adverse side effects. The cannabinoid 1 (CB1) receptor antagonist rimonabant, while effective at producing weight loss, has been discontinued from clinical use owing to increased incidence of depression. This study investigates the interaction between the cannabinoid and melanin-concentrating hormone (MCH) systems in food intake, body weight control, and mood. DESIGN: Lean male C57BL/6 mice were injected i.p. with rimonabant (0.0, 0.03, 0.3 and 3.0 mg kg(-1)) or the MCH1-R antagonist SNAP-94847 (0.0, 1.0, 5.0 and 10.0 mg kg(-1)) to establish dose response parameters for each drug. Diet-induced obese (DIO) mice were given either vehicle, sub-threshold dose of rimonabant and SNAP-94847 alone or in combination. Impact on behavioral outcomes, food intake, body weight, plasma metabolites and expression of key metabolic proteins in the brown adipose tissue (BAT) and white adipose tissue (WAT) were measured. RESULTS: The high doses of rimonabant and SNAP-94847 produced a reduction in food intake after 2 and 24 h. Combining sub-threshold doses of rimonabant and SNAP-94847 produced a significantly greater loss of body weight in DIO mice compared with vehicle and monotherapies. In addition, combining sub effective doses of these drugs led to a shift in markers of thermogenesis in BAT and lipid metabolism in WAT consistent with increased energy expenditure and lipolysis. Furthermore, co-administration of rimonabant and SNAP-94847 produced a transient reduction in food intake, and significantly reduced fat mass and adipocyte size. Importantly, SNAP-94847 significantly attenuated the ability of rimonabant to reduced immobility time in the forced swim test. CONCLUSION: These results provide proof of principle that combination of rimonabant and a MCH1 receptor antagonist is highly effective in reducing body weight below that achieved by rimonabant and SNAP-94847 monotherapies. In addition, the combination therapy normalizes the rimonabant-induced behavioral changes seen in the forced swim test.

Differential modulation of gonadotropin responses to kisspeptin by aminoacidergic, peptidergic, and nitric oxide neurotransmission.

Kisspeptins (Kp), products of the Kiss1 gene, have emerged as essential elements in the control of GnRH neurons and gonadotropic secretion. However, despite considerable progress in the field, to date limited attention has been paid to elucidate the potential interactions of Kp with other neurotransmitters known to centrally regulate the gonadotropic axis. We characterize herein the impact of manipulations of key aminoacidergic (glutamate and GABA), peptidergic (NKB, Dyn, and MCH), and gaseous [nitric oxide (NO)] neurotransmission on gonadotropin responses to Kp-10 in male rats. Blockade of ionotropic glutamate receptors (of the NMDA and non-NMDA type) variably decreased LH responses to Kp-10, whereas activation of both ionotropic and metabotropic receptors, which enhanced LH and FSH release per se, failed to further increase gonadotropin responses to Kp-10. In fact, coactivation of metabotropic receptors attenuated LH and FSH responses to Kp-10. Selective activation of GABA(A) receptors decreased Kp-induced gonadotropin secretion, whereas their blockade elicited robust LH and FSH bursts and protracted responses to Kp-10 when combined with GABA(B) receptor inhibition. Blockade of Dyn signaling (at κ-opioid receptors) enhanced LH responses to Kp-10, whereas activation of Dyn and NKB signaling modestly reduced Kp-induced LH and FSH release. Finally, MCH decreased basal LH secretion and modestly reduced FSH responses to Kp-10, whereas LH responses to Kp-10 were protracted after inhibition of NO synthesis. In summary, we present herein evidence for the putative roles of glutamate, GABA, Dyn, NKB, MCH, and NO in modulating gonadotropic responses to Kp in male rats. Our pharmacological data will help to characterize the central interactions and putative hierarchy of key neuroendocrine pathways involved in the control of the gonadotropic axis.

Thyrotropin-releasing hormone (TRH) inhibits melanin-concentrating hormone neurons: implications for TRH-mediated anorexic and arousal actions.

Thyrotropin-releasing hormone (TRH) increases activity and decreases food intake, body weight, and sleep, in part through hypothalamic actions. The mechanism of this action is unknown. Melanin-concentrating hormone (MCH) and hypocretin/orexin neurons in the lateral hypothalamus (LH) together with neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons in the arcuate nucleus play central roles in energy homeostasis. Here, we provide electrophysiological evidence from GFP-reporter transgenic mouse brain slices that shows TRH modulates the activity of MCH neurons. Using whole-cell current-clamp recording, we unexpectedly found that TRH and its agonist, montrelin, dose-dependently inhibited MCH neurons. Consistent with previous reports, TRH excited hypocretin/orexin neurons. No effect was observed on arcuate nucleus POMC or NPY neurons. The TRH inhibition of MCH neurons was eliminated by bicuculline and tetrodotoxin, suggesting that the effect was mediated indirectly through synaptic mechanisms. TRH increased spontaneous IPSC frequency without affecting amplitude and had no effect on miniature IPSCs or EPSCs. Immunocytochemistry revealed little interaction between TRH axons and MCH neurons, but showed TRH axons terminating on or near GABA neurons. TRH inhibition of MCH neurons was attenuated by Na(+)-Ca(2+) exchanger (NCX) inhibitors, TRPC channel blockers and the phospholipase C inhibitor U-73122. TRH excited LH GABA neurons, and this was also reduced by NCX inhibitors. Finally, TRH attenuated the excitation of MCH neurons by hypocretin. Together, our data suggest that TRH inhibits MCH neurons by increasing synaptic inhibition from local GABA neurons. Inhibition of MCH neurons may contribute to the TRH-mediated reduction in food intake and sleep.

New insights into the binding mode of melanin concentrating hormone receptor-1 antagonists: homology modeling and explicit membrane molecular dynamics simulation study.

Melanin concentrating hormone (MCH) is a cyclic 19-amino-acid peptide expressed mainly in the hypothalamus. It is involved in the control of feeding behavior, energy homeostasis, and body weight. Administration of MCH-R1 antagonists has been proved to reduce food intake and cause weight loss in animal models. In the present study, a homology model of the human MCH-R1 was constructed using the crystal structure of bovine rhodopsin (PDB: 1u19) as a template. Based on the observation that MCH-R1 can bind ligands of high chemical diversity, the initial model was subjected to an extensive ligand-supported refinement using antagonists of different chemotypes. The refinement process involved stepwise energy minimizations and molecular dynamics simulations. The refined model was inserted into a pre-equilibrated DPPC/TIP3P membrane system and then simulated for 20 ns in complex with structurally diverse antagonists. This protocol was able to explain the SAR of MCH-R1 antagonists with diverse chemical structures. Moreover, it reveals new insights into the critical recognition sites within the receptor. This work represents the first detailed study of molecular dynamics of MCH-R1 inserted into a membrane-aqueous environment.

No relationship between the type of pituitary suppression for IVF and chromosomal abnormality rates of blastomeres: an observational study.

OBJECTIVE: To investigate whether the incidence of chromosomally abnormal blastomeres is related to the type of pituitary suppression used in ovarian stimulation. DESIGN: Retrospective study. SETTING: Tertiary referral center. PATIENT(S): The study involved 694 consecutive cycles; 320 belonged to agonist group and 374 to antagonist group, of patients' ≤ 37 years of age who underwent preimplantation genetic screening between October 1, 1992 until December 31, 2006. All of them (and their partners) had normal karyotyping results. Only the data of patients who had at least one embryo biopsy were analyzed. INTERVENTION(S): Preimplantation genetic screening (PGS). MAIN OUTCOME MEASURE(S): The primary outcome measure was detection of abnormal blastomeres on the total number of embryos analyzed. RESULT(S): The total abnormal ratio was statistically similar between the embryos of the two study groups (49.9 ± 28.1 vs. 50.2 ± 26.6). Likewise, a multivariate (linear regression) analysis indicated that the total abnormality ratio was not influenced by the type of stimulation when simultaneously adjusting for age, rank of trials, indication for preimplantation genetic screening, total gonadotropin amount, number of cumulus-oocyte complexes, and number of two pronuclear oocytes embryos. No difference was observed in ongoing pregnancy rates between agonists and antagonists (26.6% vs. 23.3%, respectively). CONCLUSION(S): Based on our findings there is no difference in the proportion of abnormal blastomeres either when using gonadotropin-releasing hormone (GnRH) agonist, or antagonist protocol.

The endogenous actions of hypothalamic peptides on brown adipose tissue thermogenesis in the rat.

Although the neuronal pathways within the hypothalamus critical in controlling feeding and energy expenditure and projecting to brown adipose tissue (BAT) have been identified and their peptidergic content characterized, endogenous action of such peptides in the control of BAT activity has not been elucidated. Here male Sprague Dawley rats received infusions of either melanin-concentrating hormone antagonist (SNAP-7941) (1 microg/microl x h), orexin A receptor antagonist (SB-334867-A; 1 microg/microl x h), combined SB-334867-A (1 microg/microl x h), and SNAP-7941 (1 microg/microl x h), or melanocortin-3/4 receptor antagonist (SHU9119) (1 microg/microl x h) via an indwelling cannula in the lateral ventricle attached to s.c. implanted osmotic minipump. BAT temperature, physical activity, body weight, food intake, and changes in uncoupling protein (UCP)-1 were measured. SB-334867-A and SNAP-7941 significantly increased BAT temperature and UCP1 expression and reduced food intake and body weight. Combined infusion of SB-334867-A and SNAP-7941 produced a pronounced response that was greater than the addition of the individual effects in all parameters measured. SHU9119 significantly decreased BAT temperature and UCP1 expression and increased feeding and body weight. In a second series of experiments, the effect of SB-334867-A and SNAP-7941 alone or combination on the expression of the Fos protein was determined. SB-334867-A and SNAP-7941 increased Fos expression in key hypothalamic and brainstem feeding-related regions. In combination, these antagonists produced a greater than additive elevation of Fos expression in most of the regions evaluated. These findings support a role for endogenous orexigenic and anorexigenic hypothalamic peptides acting in concert to create a thermogenic tone via BAT activity.

Quinolinate induces selective loss of melanin-concentrating hormone neurons, rather than orexin neurons, in the hypothalamus of mice and young rats.

Orexins are neuropeptides produced in the lateral hypothalamus and implicated in regulation of sleep-wake cycle. Selective loss of orexin neurons is found in the brain of patients with narcolepsy, but the mechanisms of this pathological change are unclear. A previous study showed that excessive stimulation of N-methyl-d-aspartate (NMDA) receptors by quinolinic acid (QA) caused selective loss of orexin neurons in rat hypothalamic slice culture. Here we examined QA toxicity on orexin neurons and melanin-concentrating hormone (MCH) neurons in vivo. Contrary to the expectation, injection of QA (60 and 120 nmol) into the lateral hypothalamus of male C57BL/6 mice caused selective loss of MCH neurons rather than orexin neurons, and this toxicity of QA was attenuated by MK-801, an NMDA receptor antagonist. Selective loss of MCH neurons with preserved orexin neurons was observed even when GABA(A) receptor antagonists such as bicuculline and picrotoxin were injected with QA. A significant decrease in the number of orexin neurons was induced when QA injection was performed in the dark phase of diurnal cycle, but the degree of the decrease was still lower than that in the number of MCH neurons. Finally, QA (60 nmol) induced selective loss of MCH neurons also in young rats at 3-4 weeks of age. These results do not support the hypothesis that acute excitotoxicity mediated by NMDA receptors is responsible for the pathogenesis of narcolepsy.

Randomized, comparative pilot study of pituitary suppression with depot leuprorelin versus cetrorelix acetate 3 mg in gonadotropin stimulation protocols for oocyte donors.

In a pilot study, implantation and pregnancy rates per transfer were favorable in recipients of donated eggs treated with a single dose of cetrorelix acetate 3 mg compared with recipients of donated eggs treated with the long protocol (42.3% vs. 30.5%, and 71.0% vs. 46.7%, respectively; NS). The stimulation protocol based on gonadotropins and a single dose of cetrorelix acetate 3 mg is adequate in terms of safety and comfort of donors and the likelihood of pregnancy among recipients, although these favorable results require confirmation in future studies.

Significantly superior response in the right ovary compared with the left ovary after stimulation with follicle-stimulating hormone in a pituitary down-regulation regimen.

OBJECTIVE: To compare the differences between the right and left ovarian responses in patients undergoing standard in vitro fertilization (IVF) treatment. DESIGN: Prospective, observational study. SETTING: A university hospital in Taiwan. PATIENT(S): Seven hundred eighty-nine consecutive patients undergoing IVF or intracytoplasmic sperm injection. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): The number of oocytes retrieved, fertilization rates, number of grade 1 zygotes and number of embryos produced, embryo arrest-free rate, and mean number of top-quality embryos on the day of transfer. RESULT(S): The number of follicles > or = 16 mm in diameter on day 2.5 versus 2.2 of human chorionic gonadotropin (hCG) administration, the number of follicles > or = 10 mm in diameter on hCG day 6.5 versus 6.1, the number of oocytes (3.6 vs. 3.0), the percentage fertilization (79.9 vs. 74.6%), and the mean number of mature oocytes and grade 1 zygotes (2.3 vs. 1.8 and 1.79 vs. 0.93, respectively), and the mean available number of top-quality embryos on transfer day 1.39 versus 0.73 were all statistically significantly greater in the right compared with the left ovary; however, the pregnancy and implantation rates were similar. CONCLUSION(S): There are statistically significant differences between the right and left ovarian responses in IVF patients with healthy ovaries, and the right ovarian responses are superior to the left ovarian responses.

Curcumin acts as anti-tumorigenic and hormone-suppressive agent in murine and human pituitary tumour cells in vitro and in vivo.

Curcumin (diferuloylmethane) is the active ingredient of the spice plant Curcuma longa and has been shown to act anti-tumorigenic in different types of tumours. Therefore, we have studied its effect in pituitary tumour cell lines and adenomas. Proliferation of lactosomatotroph GH3 and somatotroph MtT/S rat pituitary cells as well as of corticotroph AtT20 mouse pituitary cells was inhibited by curcumin in monolayer cell culture and in colony formation assay in soft agar. Fluorescence-activated cell sorting (FACS) analysis demonstrated curcumin-induced cell cycle arrest at G2/M. Analysis of cell cycle proteins by immunoblotting showed reduction in cyclin D(1), cyclin-dependent kinase 4 and no change in p27(kip). FACS analysis with Annexin V-FITC/7-aminoactinomycin D staining demonstrated curcumin-induced early apoptosis after 3, 6, 12 and 24 h treatment and nearly no necrosis. Induction of DNA fragmentation, reduction of Bcl-2 and enhancement of cleaved caspase-3 further confirmed induction of apoptosis by curcumin. Growth of GH3 tumours in athymic nude mice was suppressed by curcumin in vivo. In endocrine pituitary tumour cell lines, GH, ACTH and prolactin production were inhibited by curcumin. Studies in 25 human pituitary adenoma cell cultures have confirmed the anti-tumorigenic and hormone-suppressive effects of curcumin. Altogether, the results described in this report suggest this natural compound as a good candidate for therapeutic use on pituitary tumours.

Novel approach for chemotype hopping based on annotated databases of chemically feasible fragments and a prospective case study: new melanin concentrating hormone antagonists.

A novel strategy for chemotype hopping, based on annotated databases of chemically feasible fragments and their oriented functionalization, is presented. A three-dimensional (3D) similarity analysis of project-oriented functionalized scaffolds provides a prioritized proposal for synthesis with the most appropriate linkers and optimal regiochemistry on R-groups. This strategy maximizes the potential of proprietary and commercially available compounds. A retrospective and prospective case study, on melanin concentrating hormone (MCH) antagonists, showing the impact on the drug discovery process of this new strategy by maintaining primary activity and improving key ADME/Tox property while enhancing intellectual property (IP) position is demonstrated.

Lactational exposure to hexavalent chromium delays puberty by impairing ovarian development, steroidogenesis and pituitary hormone synthesis in developing Wistar rats.

Hexavalent chromium (Cr-VI) is used in a wide range of industries. Cr-VI from chromate industries and atmospheric emissions contribute to the Cr contamination in the environment. Cr is a reproductive metal toxicant that can traverse the placental barrier and cause a wide range of fetal effects including ovotoxicity. Therefore, the goal of this study was to investigate the basic mechanisms involved in Cr(VI)-induced ovotoxicity, and the protective role of vitamin C on ovarian follicular development and function in Cr(VI)-induced reproductive toxicity using both in vivo and in vitro approaches. Lactating rats received potassium dichromate (200 mg/L) with or without vitamin C (500 mg/L), through drinking water from postpartum days 1-21. During postnatal days (PND) 1-21 the pups received Cr(VI) via the mother's milk. Pups from both control and treatment groups were continued on regular diet and water from PND-21 onwards, and euthanized on PND-21, -45 and -65. Cr(VI) decreased steroidogenesis, GH and PRL, increased FSH and did not alter LH. Cr(VI) delayed puberty, decreased follicle number, and extended estrous cycle. Spontaneously immortalized rat granulosa cells were treated with 12.5 microM (IC(50)) potassium dichromate for 12 and 24 h, with or without vitamin C pre-treatment. Cr(VI) decreased the mRNA expressions of StAR, SF-1, 17beta-HSD-1, 17beta-HSD-2, FSHR, LHR, ER alpha and ER beta. Vitamin C pre-treatment protected ovary and granulosa cells from the deleterious effects of Cr(VI) toxicity, both in vivo and in vitro. Therefore, Cr(VI) toxicity could be a potential risk to the reproductive system in developing females, and vitamin C plays a protective role against Cr(VI)-induced ovotoxicity.

Microinjections of melanin concentrating hormone into the nucleus tractus solitarius of the rat elicit depressor and bradycardic responses.

The presence of melanin-concentrating hormone (MCH) containing processes, projecting from the lateral hypothalamus to the medial nucleus tractus solitarius (mNTS), has been reported in the rat. It was hypothesized that MCH acting within the mNTS may modulate the central regulation of cardiovascular function. This hypothesis was tested in urethane-anesthetized, artificially ventilated, adult male Wistar rats. Microinjections (100 nl) of MCH (0.25, 0.5, 0.75, and 1 mM) into the mNTS of anesthetized rats elicited decreases in mean arterial pressure (20.4+/-1.6, 50.7+/-3.3, 35.7+/-2.8 and 30.0+/-2.6 mm Hg, respectively). The decreases in heart rate in response to these concentrations of MCH were 40.0+/-8.7, 90.0+/-13.0, 48.0+/-7.3 and 48.0+/-8.0 beats/min, respectively. Maximum cardiovascular responses were elicited by a 0.5 mM concentration of MCH. Cardiovascular responses to MCH were similar in unanesthetized mid-collicular decerebrate rats. Control microinjections of normal saline (100 nl) did not elicit any cardiovascular response. Ipsilateral or bilateral vagotomy significantly attenuated MCH-induced bradycardia. Prior microinjections of PMC-3881-PI (2 mM; MCH-1 receptor antagonist) into the mNTS blocked the cardiovascular responses to microinjections of MCH. Microinjection of MCH (0.5 mM) into the mNTS decreased efferent greater splanchnic nerve activity. Direct application of MCH (0.5 mM; 4 nl) to barosensitive nucleus tractus solitarius (NTS) neurons increased their firing rate. These results indicate that: 1) MCH microinjections into the mNTS activate MCH-1 receptors and excite barosensitive NTS neurons, causing a decrease in efferent sympathetic activity and blood pressure, and 2) MCH-induced bradycardia is mediated via the activation of the vagus nerves.