shu-9119 and Disease-Models--Animal

When the nerve tissue is injured, endogenous agonist of melanocortin type 4 (MC4) receptor, α-MSH, exerts tonic pronociceptive action in the central nervous system, contributing to sustaining the neuropathic pain state and counteracting the analgesic effects of exogenous opioids. With the intent of enhancing opioid analgesia in neuropathy by blocking the MC4 activation, so-called parent compounds (opioid agonist, MC4 antagonist) were joined together using various linkers to create novel bifunctional hybrid compounds. Analgesic action of four hybrids was tested after intrathecal (i.t.) administration in mouse models of acute and neuropathic pain (chronic constriction injury model, CCI). Under nerve injury conditions, one of the hybrids, UW3, induced analgesia in 1500 times lower i.t. dose than the opioid parent (ED50: 0.0002 nmol for the hybrid, 0.3 nmol for the opioid parent) and in an over 16000 times lower dose than the MC4 parent (ED50: 3.33 nmol) as measured by the von Frey test. Two selected hybrids were tested for analgesic properties in CCI mice after intravenous (i.v.) and intraperitoneal (i.p.) administration. Opioid receptor antagonists and MC4 receptor agonists diminished the analgesic action of these two hybrids studied, though the extent of this effect differed between the hybrids; this suggests that linker is of key importance here. Further results indicate a significant advantage of hybrid compounds over the physical mixture of individual pharmacophores in their analgesic effect. All this evidence justifies the idea of synthesizing a bifunctional opioid agonist-linker-MC4 antagonist compound, as such structure may bring important benefits in neuropathic pain treatment.

Topics: Analgesics, Opioid; Animals; Constriction; Disease Models, Animal; Dose-Response Relationship, Drug; Injections, Spinal; Male; Mice; Narcotic Antagonists; Neuralgia; Pain Measurement; Receptor, Melanocortin, Type 4

Growing evidence suggests that the pituitary adenylate cyclase-activating polypeptide (PACAP)/PAC1 receptor system represents one of the main regulators of the behavioral, endocrine, and autonomic responses to stress. Although induction of anorexia is a well-documented effect of PACAP, the central sites underlying this phenomenon are poorly understood. The present studies addressed this question by examining the neuroanatomical, behavioral, and pharmacological mechanisms mediating the anorexia produced by PACAP in the central nucleus of the amygdala (CeA), a limbic structure implicated in the emotional components of ingestive behavior. Male rats were microinfused with PACAP (0-1 μg per rat) into the CeA and home-cage food intake, body weight change, microstructural analysis of food intake, and locomotor activity were assessed. Intra-CeA (but not intra-basolateral amygdala) PACAP dose-dependently induced anorexia and body weight loss without affecting locomotor activity. PACAP-treated rats ate smaller meals of normal duration, revealing that PACAP slowed feeding within meals by decreasing the regularity and maintenance of feeding from pellet-to-pellet; postprandial satiety was unaffected. Intra-CeA PACAP-induced anorexia was blocked by coinfusion of either the melanocortin receptor 3/4 antagonist SHU 9119 or the tyrosine kinase B (TrKB) inhibitor k-252a, but not the CRF receptor antagonist D-Phe-CRF(12-41). These results indicate that the CeA is one of the brain areas through which the PACAP system promotes anorexia and that PACAP preferentially lessens the maintenance of feeding in rats, effects opposite to those of palatable food. We also demonstrate that PACAP in the CeA exerts its anorectic effects via local melanocortin and the TrKB systems, and independently from CRF.

Topics: Analysis of Variance; Animals; Anorexia; Body Weight; Central Amygdaloid Nucleus; Corticotropin-Releasing Hormone; Disease Models, Animal; Dose-Response Relationship, Drug; Eating; Feeding Behavior; Male; Melanocortins; Melanocyte-Stimulating Hormones; Motor Activity; Pituitary Adenylate Cyclase-Activating Polypeptide; Rats; Rats, Wistar; Receptor, trkB; Time Factors; Vasodilator Agents

Neutrophil recruitment is a key process in the pathogenesis of stroke, and may provide a valuable therapeutic target. Targeting the melanocortin (MC) receptors has previously shown to inhibit leukocyte recruitment in peripheral inflammation, however, it is not known whether treatments are effective in the unique cerebral microvascular environment. Here, we provide novel research highlighting the effects of the MC peptides on cerebral neutrophil recruitment, demonstrating important yet discrete roles for both MC1 and MC3.. Using intravital microscopy, in 2 distinct murine models of cerebral ischemia-reperfusion (I/R) injury, we have investigated MC control for neutrophil recruitment. After global I/R, pharmacological treatments suppressed pathological neutrophil recruitment. MC1 selective treatment rapidly inhibited neutrophil recruitment while a nonselective MC agonist provided protection even when coadministered with an MC3/4 antagonist, suggesting the importance of early MC1 signaling. However, by 2-hour reperfusion, MC1-mediated effects were reduced, and MC3 anti-inflammatory circuits predominated. Mice bearing a nonfunctional MC1 displayed a transient exacerbation of neutrophil recruitment after global I/R, which diminished by 2 hours. However importantly, enhanced inflammatory responses in both MC1 mutant and MC3 (-/-) mice resulted in increased infarct size and poor functional outcome after focal I/R. Furthermore, we used an in vitro model of leukocyte recruitment to demonstrate these anti-inflammatory actions are also effective in human cells.. These studies reveal for the first time MC control for neutrophil recruitment in the unique pathophysiological context of cerebral I/R, while also demonstrating the potential therapeutic value of targeting multiple MCs in developing effective therapeutics.

Topics: Animals; Brain Ischemia; Disease Models, Animal; Gene Expression Regulation; Humans; Male; Melanocyte-Stimulating Hormones; Mice; Neutrophil Infiltration; Receptor, Melanocortin, Type 1; Receptor, Melanocortin, Type 3; Reperfusion Injury; RNA, Messenger

In postmenopausal women the mechanisms responsible for hypertension have not been completely elucidated, and there are no gender-specific guidelines for women despite studies showing that blood pressure is not as well controlled to goal in women as in men. In the present study we tested the hypotheses that the sympathetic nervous system and the renal sympathetic nerves contribute to hypertension in aging female rats, that sympathetic activation may be mediated by the melanocortin 3/4 receptor (MC3/4R), and that MC3/4R activation may be due to increases in leptin. α-1, β-1,2-Adrenergic blockade reduced blood pressure in both young (3-4 mo) and old (18-19 mo) female spontaneously hypertensive rats (SHR). Renal denervation attenuated the hypertension more in old females than young females. MC3/4R antagonism with SHU-9119 given intracerebroventricularly had no effect on blood pressure in either young or old females but significantly reduced blood pressure in old males. Plasma leptin levels were similar in old male and female SHR and in old versus young females. These data suggest that the hypertension in old female SHR is in part due to activation of the sympathetic nervous system, that the renal nerves contribute to the hypertension, and that the mechanism responsible for sympathetic activation in old females is independent of the MC3/4R.

Topics: Age Factors; Animals; Blood Pressure; Denervation; Disease Models, Animal; Female; Hypertension; Kidney; Leptin; Melanocyte-Stimulating Hormones; Postmenopause; Rats; Rats, Inbred SHR; Receptor, Melanocortin, Type 2; Receptor, Melanocortin, Type 3; Sympathetic Nervous System

Nesfatin-1 is produced in the periphery and in the brain where it has been demonstrated to regulate appetite, stress hormone secretion, and cardiovascular function. The anorexigenic action of central nesfatin-1 requires recruitment of neurons producing the melanocortins and centrally projecting oxytocin (OT) and corticotropin-releasing hormone (CRH) neurons. We previously have shown that two components of this pathway, the central melanocortin and oxytocin systems, contribute to the hypertensive action of nesfatin-1 as well. We hypothesized that the cardiovascular effect of nesfatin-1 also was dependent on activation of neurons expressing CRH receptors, and that the order of activation of the melanocortin-CRH-oxytocin circuit was preserved for both the anorexigenic and hypertensive actions of the peptide. Pretreatment of male rats with the CRH-2 receptor antagonist astressin2B abrogated nesfatin-1-induced increases in mean arterial pressure (MAP). Furthermore, the hypertensive action of CRH was blocked by pretreatment with an oxytocin receptor antagonist ornithine vasotocin (OVT), indicating that the hypertensive effect of nesfatin-1 may require activation of oxytocinergic (OTergic) neurons in addition to recruitment of CRH neurons. Interestingly, we found that the hypertensive effect of α-melanocyte stimulating hormone (α-MSH) itself was not blocked by either astressin2B or OVT. These data suggest that while α-MSH-producing neurons are part of a core melanocortin-CRH-oxytocin circuit regulating food intake, and a subpopulation of melanocortin neurons activated by nesfatin-1 do mediate the hypertensive action of the peptide, α-MSH can signal independently from this circuit to increase MAP.

Topics: alpha-MSH; Animals; Blood Pressure; Calcium-Binding Proteins; Corticotropin-Releasing Hormone; Disease Models, Animal; DNA-Binding Proteins; Hormones; Hypertension; Male; Melanocortins; Melanocyte-Stimulating Hormones; Nerve Net; Nerve Tissue Proteins; Nucleobindins; Oxytocin; Peptide Fragments; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Receptors, Corticotropin-Releasing Hormone; Receptors, Oxytocin; Vasotocin

Neuronostatin, a newly identified peptide encoded by the somatostatin (SST) gene, was proved to produce significant antinociceptive effect in mouse tail immersion test. However, the effect of neuronostatin on tonic pain was still not clear. The aim of this study was to investigate the effect of neuronostatin in the formalin test and its possible mechanism. We found that intracerebroventricular (i.c.v.) administration of neuronostatin (1, 3, 6, 12nmol/mouse) increased licking in a dose-related manner during the late phase, but did not affect the early phase of formalin test in mice. In addition, the hyperalgesic effect during the late phase was completely reversed by melanocortin 3/4 receptor antagonist SHU9119 (50pmol/mouse) or opioid receptor antagonist naloxone (5nmol/mouse), but not GABAA receptor antagonist bicuculline (1086pmol/mouse). These data suggested that the hyperalgesic response induced by neuronostatin was dependent upon the central melanocortin system and endogenous opioid system. In conclusion, these results indicated that neuronostatin may be a new neuropeptide with important role in the modulation of acute and tonic pain.

Topics: Analysis of Variance; Animals; Bicuculline; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; GABA-A Receptor Antagonists; Hyperalgesia; Injections, Intraventricular; Male; Melanocyte-Stimulating Hormones; Mice; Mice, Inbred Strains; Pain Measurement; Pain Threshold; Peptide Fragments; Somatostatin; Time Factors

We have previously demonstrated that leptin-mediated activation of the central nervous system (CNS) melanocortin system reduces appetite and increases sympathetic activity and blood pressure (BP). In the present study we examined whether endogenous melanocortin system activation, independent of leptin's actions, contributes to the regulation of BP and metabolic functions in obese Zucker rats, which have mutated leptin receptors. The long-term cardiovascular and metabolic effects of central melanocortin-3/4 receptor (MC3/4R) antagonism with SHU-9119 were assessed in lean (n = 6) and obese (n = 8) Zucker rats. BP and heart rate (HR) were measured 24-h/day by telemetry and an intracerebroventricular cannula was placed in the brain lateral ventricle. After stable control measurements, SHU-9119 was infused intracerebroventricularlly (1 nmol/h) for 10 days followed by a 10-day recovery period. Chronic CNS MC3/4R antagonism significantly increased food intake and body weight in lean (20 ± 1 to 45 ± 2 g and 373 ± 11 to 432 ± 14 g) and obese (25 ± 2 to 35 ± 2 g and 547 ± 10 to 604 ± 11 g) rats. No significant changes were observed in plasma glucose levels in lean or obese rats, whereas plasma leptin and insulin levels markedly increased in lean Zucker rats during CNS MC3/4R antagonism. Chronic SHU-9119 infusion in obese Zucker rats reduced mean arterial pressure (MAP) and HR by 6 ± 1 mmHg and 24 ± 5 beats/min, whereas in lean rats SHU-9119 infusion reduced HR by 31 ± 9 beats/min while causing only a transient decrease in MAP. These results suggest that in obese Zucker rats the CNS melanocortin system contributes to elevated BP independent of leptin receptor activation.

Topics: Animals; Blood Glucose; Blood Pressure; Central Nervous System; Disease Models, Animal; Heart Rate; Hypertension; Infusions, Intraventricular; Insulin; Male; Melanocortins; Melanocyte-Stimulating Hormones; Obesity; Rats; Rats, Zucker; Receptor, Melanocortin, Type 3; Receptor, Melanocortin, Type 4; Receptors, Leptin

In response to illness, animals subvert normal homeostasis and divert their energy utilization to fight infection. An important and unexplored feature of this response is the suppression of physical activity and foraging behavior in the setting of negative energy balance. Inflammatory signaling in the hypothalamus mediates the febrile and anorectic responses to disease, but the mechanism by which locomotor activity (LMA) is suppressed has not been described. Lateral hypothalamic orexin (Ox) neurons link energy status with LMA, and deficiencies in Ox signaling lead to hypoactivity and hypophagia. In the present work, we examine the effect of endotoxin-induced inflammation on Ox neuron biology and LMA in rats. Our results demonstrate a vital role for diminished Ox signaling in mediating inflammation-induced lethargy. This work defines a specific population of inflammation-sensitive, arousal-associated Ox neurons and identifies a proximal neural target for inflammatory signaling to Ox neurons, while eliminating several others.

Topics: Analysis of Variance; Animals; Dark Adaptation; Disease Models, Animal; Drug Administration Routes; Enzyme-Linked Immunosorbent Assay; Food Deprivation; Gene Expression Regulation; Green Fluorescent Proteins; I-kappa B Proteins; Inflammation; Injections, Intraventricular; Interleukin-1beta; Interleukin-6; Intracellular Signaling Peptides and Proteins; Lateral Ventricles; Lethargy; Male; Melanocyte-Stimulating Hormones; Mice; Mice, Transgenic; Motor Activity; Neoplasm Transplantation; Neurons; Neuropeptides; Neurotensin; NF-KappaB Inhibitor alpha; Orexins; Photoperiod; Polysaccharides; Proto-Oncogene Proteins c-fos; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Receptors, Corticotropin; Receptors, Interleukin-11; Receptors, OSM-LIF; RNA, Messenger

Leptin plays a critical role in the control of energy homeostasis. The sympathetic cardiovascular actions of leptin have emerged as a potential link between obesity and hypertension. We previously demonstrated that in mice, modest obesity induced by 10 wk of a high-fat diet is associated with preservation of leptin ability to increase renal sympathetic nerve activity (SNA) despite the resistance to the metabolic effects of leptin. Here, we examined whether selective leptin resistance exists in mice with late-stage diet-induced obesity (DIO) produced by 20 wk of a high-fat diet. The decrease in food intake and body weight induced by intraperitoneal or intracerebroventricular injection of leptin was significantly attenuated in the DIO mice. Regional SNA responses to intravenous leptin were also attenuated in DIO mice. In contrast, intracerebroventricularly administered leptin caused contrasting effects on regional SNA in DIO mice. Renal SNA response to intracerebroventricular leptin was preserved, whereas lumbar and brown adipose tissue SNA responses were attenuated. Intact renal SNA response to leptin combined with the increased cerebrospinal fluid leptin levels in DIO mice represents a potential mechanism for the adverse cardiovascular consequences of obesity. Lastly, we examined the role of phosphoinositol-3 kinase (PI3K) and melanocortin receptors (MCR) in mediating the preserved renal SNA response to leptin in obesity. Presence of PI3K inhibitor (LY294002) or MC3/4R antagonist (SHU9119) significantly attenuated the renal SNA response to leptin in DIO and agouti obese mice. Our results demonstrate the importance of PI3K and melanocortin receptors in the transduction of leptin-induced renal sympathetic activation in obesity.

Topics: Adipose Tissue, Brown; Animals; Body Weight; Chromones; Dietary Fats; Disease Models, Animal; Dose-Response Relationship, Drug; Eating; Injections, Intraperitoneal; Injections, Intraventricular; Kidney; Leptin; Lumbar Vertebrae; Male; Melanocyte-Stimulating Hormones; Mice; Mice, Inbred C57BL; Mice, Obese; Morpholines; Obesity; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Receptors, Melanocortin; Signal Transduction; Sympathetic Nervous System; Time Factors