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Fetissov SO, Hallman J, Oreland L, Af Klinteberg B, Grenbäck E, Hulting AL, Hökfelt T. Autoantibodies against alpha -MSH, ACTH, and LHRH in anorexia and bulimia nervosa patients. Proc Natl Acad Sci U S A 2002; 99:17155-60. [PMID: 12486250 PMCID: PMC139285 DOI: 10.1073/pnas.222658699] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2002] [Indexed: 11/18/2022] Open
Abstract
The hypothalamic arcuate nucleus is involved in the control of energy intake and expenditure and may participate in the pathogenesis of eating disorders such as anorexia nervosa (AN) and bulimia nervosa (BN). Two systems are of particular interest in this respect, synthesizing alpha-melanocyte-stimulating hormone (alpha-MSH) and synthesizing neuropeptide Y, respectively. We report here that 42 of 57 (74%) AN andor BN patients studied had in their plasma Abs that bind to melanotropes andor corticotropes in the rat pituitary. Among these sera, 8 were found to bind selectively to alpha-MSH-positive neurons and their hypothalamic and extrahypothalamic projections as revealed with immunostaining on rat brain sections. Adsorption of these sera with alpha-MSH peptide abolished this immunostaining. In the pituitary, the immunostaining was blocked by adsorption with alpha-MSH or adrenocorticotropic hormone. Additionally, 3 ANBN sera bound to luteinizing hormone-releasing hormone (LHRH)-positive terminals in the rat median eminence, but only 2 of them were adsorbed with LHRH. In the control subjects, 2 of 13 sera (16%) displayed similar to ANBN staining. These data provide evidence that a significant subpopulation of ANBN patients have autoantibodies that bind to alpha-MSH or adrenocorticotropic hormone, a finding pointing also to involvement of the stress axis. It remains to be established whether these Abs interfere with normal signal transduction in the brain melanocortin circuitryLHRH system andor in other central and peripheral sites relevant to food intake regulation, to what extent such effects are related to andor could be involved in the pathophysiology or clinical presentation of ANBN, and to what extent increased stress is an important factor for production of these autoantibodies.
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Affiliation(s)
- Sergueï O Fetissov
- Departments of Neuroscience and Endocrinology, Karolinska Institute, SE-171 77 Stockholm, Sweden.
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Schiöth HB, Tesfaye A, Mutulis F, Rudzish R, Mutule I, Muceniece R, Watanobe H, Wikberg JES. Subtype selective binding properties of substituted linear melanocyte stimulating hormone analogues. Neuropeptides 2002; 36:427-34. [PMID: 12507437 DOI: 10.1016/s0143-4179(02)00133-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The melanocortin receptors are peptide binding G-protein coupled receptors that play a role in important physiological functions such as energy balance, inflammatory processes and several aspects of reproduction. In this study, we synthesised 11 new linear MSH analogues and tested their binding to the human MC receptors (MC1, MC3, MC4 and MC5) expressed in COS cells. Our results show that introduction of Asp in position 4 similarly affects the binding to the MC1, MC4 and MC5 receptors, but drastically lowers the binding to the MC3 receptor. Arg(5) substitution shows relatively high affinity for the MC4 receptor, while the results also give further support for specific importance of His(6) for the MC1 receptor. Introduction of Asp in position 10, mimicking gamma-MSH, decreased the affinity for the MC3 receptor in similar manner as for the MC4 receptor, suggesting that there are important differences in the binding conformation of gamma-MSH and NPD-MSH. Our results provide further information about the ligand binding requirements for each of the MC receptor subtypes, and highlights differential influence of the core residues in the MSH peptides. The data set also provides useful information for further calculations and modeling of MC receptor binders.
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Affiliation(s)
- Helgi B Schiöth
- Department of Neuroscience, Biomedical Center, Uppsala University, Box 593, Uppsala 751 24, Sweden.
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Abstract
Energy homeostasis is controlled by a complex neuroendocrine system consisting of peripheral signals like leptin and central signals, in particular, neuropeptides. Several neuropeptides with anorexigenic (POMC, CART, and CRH) as well as orexigenic (NPY, AgRP, and MCH) actions are involved in this complex (partly redundant) controlling system. Starvation as well as overfeeding lead to changes in expression levels of these neuropeptides, which act downstream of leptin, resulting in a physiological response. In this review the role of several anorexigenic and orexigenic (hypothalamic) neuropeptides on food intake and body weight regulation is summarized.
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Affiliation(s)
- J J G Hillebrand
- Department of Medical Pharmacology, Rudolf Magnus Institute for Neurosciences, Utrecht University, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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Martin WJ, McGowan E, Cashen DE, Gantert LT, Drisko JE, Hom GJ, Nargund R, Sebhat I, Howard AD, Van der Ploeg LHT, MacIntyre DE. Activation of melanocortin MC(4) receptors increases erectile activity in rats ex copula. Eur J Pharmacol 2002; 454:71-9. [PMID: 12409007 DOI: 10.1016/s0014-2999(02)02479-2] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Melanocortin peptide agonists, alpha-melanocyte stimulating hormone (alpha-MSH) and melanotan-II, stimulate erectile activity in a variety of species, including man. Since neither peptide discriminates amongst melanocortin receptors, it is not clear which subtype mediates these pro-erectile effects. Here, we present data that melanocortin-induced erectogenesis is mediated by melanocortin MC(4) receptors. Systemic administration of a melanocortin MC(4) receptor agonist (N-[(3R)-1,2,3,4-tetrahydroisoquinolinium-3-ylcarbonyl]-(1R)-1-(4-chlorobenzyl)-2-[4-cyclohexyl-4-(1H-1,2,4-triazol-1ylmethyl)piperidin-1-yl]-2-oxoethylamine; THIQ) with high selectivity over other melanocortin receptors enhanced intracavernosal pressure and stimulated erectile activity in rats ex copula. THIQ dose-dependently (1-5 mg/kg, i.v.) increased the total number of erections, to an extent comparable or greater than that produced by apomorphine (0.025 mg/kg, s.c.). Central administration of THIQ (20 microg, intracerebroventricular (i.c.v.)) increased the number of reflexive penile erections; whereas administration of both a nonselective endogenous melanocortin MC(4) receptor antagonist (agouti-related protein (AgRP), 5.5. microg, i.c.v.) and a melanocortin MC(4) receptor preferring antagonist (MPB10, 1 mg/kg, i.v.) blocked THIQ-induced erectogenesis. These pro-erectile effects were also attenuated by systemic or central administration of an oxytocin antagonist (L-368899, 1 mg/kg, i.v.). Thus, melanocortin MC(4) receptor activation is sufficient for erectogenesis and these effects may involve oxytocinergic pathways.
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Affiliation(s)
- William J Martin
- Department of Pharmacology, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA.
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Kim CS, Lee SH, Kim RY, Kim BJ, Li SZ, Lee IH, Lee EJ, Lim SK, Bae YS, Lee W, Baik JH. Identification of domains directing specificity of coupling to G-proteins for the melanocortin MC3 and MC4 receptors. J Biol Chem 2002; 277:31310-7. [PMID: 12045190 DOI: 10.1074/jbc.m112085200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The melanocortin receptors, MC3R and MC4R, are G protein-coupled receptors that are involved in regulating energy homeostasis. Using a luciferase reporter gene under the transcriptional control of a cAMP- responsive element (CRE), the coupling efficiency of the MC4R and MC3R to G-proteins was previously shown to be different. MC4R exhibited only 30-50% of the maximum activity induced by MC3R. To assess the role of the different MC3R and MC4R domains in G-protein coupling, several chimeric MC3R/MC4R receptors were constructed. The relative luciferase activities, which were assessed after transfecting the chimeric receptors into HEK 293T cells, showed that the i3 (3rd intracellular) loop domain has an essential role in the differential signaling of MC3R and MC4R. To reveal which amino acid residue was involved in the MC4R-specific signaling in the i3 loop, a series of mutant MC4Rs was constructed. Reporter gene analysis showed that single mutations of Arg(220) to Ala and Thr(232) to either Val or Ala increased the relative luciferase activities, which suggests that these specific amino acids, Arg(220) and Thr(232), in the i3 loop of MC4R play crucial roles in G-protein coupling and the subtype-specific signaling pathways. An examination of the inositol phosphate (IP) levels in the cells transfected with either MC3R or MC4R after being exposed to the melanocortin peptides revealed significant stimulation of IP production by MC3R but no detectable increase in IP production was observed by MC4R. Furthermore, none of the MC4R mutants displayed melanocortin peptide-stimulated IP production. Overall, this study demonstrated that MC3R and MC4R have distinct signaling in either the cAMP- or the inositol phospholipid-mediated pathway with different conformational requirements.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Binding Sites
- DNA Primers
- GTP-Binding Proteins/metabolism
- Genes, Reporter
- Humans
- Kinetics
- Luciferases/genetics
- Melanocyte-Stimulating Hormones/metabolism
- Models, Molecular
- Molecular Sequence Data
- Protein Conformation
- Rats
- Receptor, Melanocortin, Type 3
- Receptor, Melanocortin, Type 4
- Receptors, Corticotropin/chemistry
- Receptors, Corticotropin/genetics
- Receptors, Corticotropin/metabolism
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/metabolism
- Sequence Alignment
- Sequence Homology, Amino Acid
- Substrate Specificity
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Affiliation(s)
- Chung Sub Kim
- Laboratory of Molecular Biology, Medical Research Center, Department of Pharmacology, College of Medicine, Brain Korea 21 Project for Medical Sciences, Yonsei University, Seoul 120-752, South Korea
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56
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MacNeil DJ, Howard AD, Guan X, Fong TM, Nargund RP, Bednarek MA, Goulet MT, Weinberg DH, Strack AM, Marsh DJ, Chen HY, Shen CP, Chen AS, Rosenblum CI, MacNeil T, Tota M, MacIntyre ED, Van der Ploeg LHT. The role of melanocortins in body weight regulation: opportunities for the treatment of obesity. Eur J Pharmacol 2002; 450:93-109. [PMID: 12176114 DOI: 10.1016/s0014-2999(02)01989-1] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Five G-protein-coupled melanocortin receptors (MC(1)-MC(5)) are expressed in mammalian tissues. The melanocortin receptors support diverse physiological functions, including the regulation of hair color, adrenal function, energy homeostasis, feed efficiency, sebaceous gland lipid production and immune and sexual function. The melanocortins (adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), beta-MSH and gamma-MSH) are agonist peptide ligands for the melanocortin receptors and these peptides are processed from the pre-prohormone proopiomelanocortin (POMC). Peptide antagonists for the melanocortin MC(1), MC(3) and MC(4) receptors include agouti-related protein (AgRP) and agouti. Diverse lines of evidence, including genetic and pharmacological data obtained in rodents and humans, support a role for the melanocortin MC(3) and MC(4) receptors in the regulation of energy homeostasis. Recent advances in the development of potent and selective peptide and non-peptide melanocortin receptor ligands are anticipated to help unravel the roles for the melanocortin receptors in humans and to accelerate the clinical use of small molecule melanocortin mimetics.
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Lotti T, Bianchi B, Ghersetich I, Brazzini B, Hercogova J. Can the brain inhibit inflammation generated in the skin? The lesson of alpha-melanocyte-stimulating hormone. Int J Dermatol 2002. [DOI: 10.1111/j.1365-4632.2002.01408.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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MacNeil DJ, Howard AD, Guan X, Fong TM, Nargund RP, Bednarek MA, Goulet MT, Weinberg DH, Strack AM, Marsh DJ, Chen HY, Shen CP, Chen AS, Rosenblum CI, MacNeil T, Tota M, MacIntyre ED, Van der Ploeg LHT. The role of melanocortins in body weight regulation: opportunities for the treatment of obesity. Eur J Pharmacol 2002; 440:141-57. [PMID: 12007532 DOI: 10.1016/s0014-2999(02)01425-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Five G-protein-coupled melanocortin receptors (MC(1)-MC(5)) are expressed in mammalian tissues. The melanocortin receptors support diverse physiological functions, including the regulation of hair color, adrenal function, energy homeostasis, feed efficiency, sebaceous gland lipid production and immune and sexual function. The melanocortins (adrenocorticotropic hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), beta-MSH and gamma-MSH) are agonist peptide ligands for the melanocortin receptors and these peptides are processed from the pre-prohormone proopiomelanocortin (POMC). Peptide antagonists for the melanocortin MC(1), MC(3) and MC(4) receptors include agouti-related protein (AgRP) and agouti. Diverse lines of evidence, including genetic and pharmacological data obtained in rodents and humans, support a role for the melanocortin MC(3) and MC(4) receptors in the regulation of energy homeostasis. Recent advances in the development of potent and selective peptide and non-peptide melanocortin receptor ligands are anticipated to help unravel the roles for the melanocortin receptors in humans and to accelerate the clinical use of small molecule melanocortin mimetics.
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Abstract
Upon receipt in the dorsal horn (DH) of the spinal cord, nociceptive (pain-signalling) information from the viscera, skin and other organs is subject to extensive processing by a diversity of mechanisms, certain of which enhance, and certain of which inhibit, its transfer to higher centres. In this regard, a network of descending pathways projecting from cerebral structures to the DH plays a complex and crucial role. Specific centrifugal pathways either suppress (descending inhibition) or potentiate (descending facilitation) passage of nociceptive messages to the brain. Engagement of descending inhibition by the opioid analgesic, morphine, fulfils an important role in its pain-relieving properties, while induction of analgesia by the adrenergic agonist, clonidine, reflects actions at alpha(2)-adrenoceptors (alpha(2)-ARs) in the DH normally recruited by descending pathways. However, opioids and adrenergic agents exploit but a tiny fraction of the vast panoply of mechanisms now known to be involved in the induction and/or expression of descending controls. For example, no drug interfering with descending facilitation is currently available for clinical use. The present review focuses on: (1) the organisation of descending pathways and their pathophysiological significance; (2) the role of individual transmitters and specific receptor types in the modulation and expression of mechanisms of descending inhibition and facilitation and (3) the advantages and limitations of established and innovative analgesic strategies which act by manipulation of descending controls. Knowledge of descending pathways has increased exponentially in recent years, so this is an opportune moment to survey their operation and therapeutic relevance to the improved management of pain.
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Affiliation(s)
- Mark J Millan
- Department of Psychopharmacology, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy/Seine, Paris, France.
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60
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Vrinten DH, Kalkman CJ, Adan RA, Gispen WH. Neuropathic pain: a possible role for the melanocortin system? Eur J Pharmacol 2001; 429:61-9. [PMID: 11698027 DOI: 10.1016/s0014-2999(01)01306-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In humans, damage to the nervous system can lead to a pain state referred to as neuropathic pain. Here, we give a short overview of the clinical picture and classification of neuropathic pain and highlight some of the currently known pathophysiological mechanisms involved, with special emphasis on neuropeptide plasticity. In this context, we discuss a specific group of neuropeptides, the melanocortins. These peptides have been demonstrated to play a role in nociception and to functionally interact with the opiate system. Recently, we demonstrated that spinal melanocortin receptors are upregulated in a rat model of neuropathic pain and that blockade of the melanocortin MC(4) receptor has anti-allodynic effects in this condition, suggesting that the melanocortin system plays a role in neuropathic pain. A natural agonist of melanocortin receptors is alpha-melanocyte-stimulating hormone (alpha-MSH), derived from the precursor molecule pro-opiomelanocortin (POMC). Cleavage of this precursor also yields beta-endorphin, which is co-released with alpha-MSH in nociception-associated areas of the spinal cord. We hypothesise that melanocortin receptor blockade attenuates a tonic influence of alpha-MSH on nociception, thus allowing the analgesic effects of beta-endorphin to develop, resulting in the alleviation of allodynia. In this way, treatment with melanocortin receptor antagonists might enhance opioid efficacy in neuropathic pain, which would be of great benefit in clinical practice.
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Affiliation(s)
- D H Vrinten
- Department of Medical Pharmacology, Rudolf Magnus Institute for Neurosciences, University Medical Centre Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands
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61
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Abstract
Since its discovery, leptin (a 167-amino acid product of the OB gene) has quickly moved to the forefront as an important hormone for regulation of energy balance. It closes a feedback loop from adipose tissue to hypothalamic neuropeptide-containing neural circuitry involved in regulation of food intake and neuroendocrine/autonomic outflow. While increased central leptin signalling reduces adiposity via a reduction in food intake, it also has remarkable metabolic effects that promote leanness, independent of food intake. These include: (i) increased energy expenditure, (ii) in-place degradation of fat, and (iii) increased thermogenesis. Hypothalamic neurones that synthesize corticotropin releasing hormone and melanocortins (i.e. alpha-melanocyte-stimulating hormone and agouti-related protein) are likely effector pathways that mediate the anorexigenic and metabolic effects of leptin. Activation of sympathetic outflow (via neuropeptidergic effector pathways of central leptin) to a number of tissues that store fat might be an important mechanism through which these peripheral metabolic effects are elicited. It is proposed that these peripheral metabolic effects contribute to the satiating properties of leptin.
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Affiliation(s)
- G van Dijk
- Department of Animal Physiology, Division Neuroendocrinology, School of Behavioural and Cognitive Neurosciences, University of Groningen, Haren, The Netherlands.
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