Effects of the central melanocortin system on feed intake, metabolic hormones and insulin action in the sheep.

Voluntary feed intake is insufficient to meet the nutrient demands associated with late pregnancy in prolific ewes and early lactation in high-yielding dairy cows. Under these conditions, peripheral signals such as growth hormone and ceramides trigger adaptations aimed at preserving metabolic well-being. Recent work in rodents has shown that the central nervous system-melanocortin (CNS-MC) system, consisting of alpha-melanocyte-stimulating hormone (α-MSH) and agouti-related peptide (AGRP) acting respectively as agonist and antagonist on central MC receptors, contributes to the regulation of some of the same adaptations. To assess the effects of the CNC-MC on peripheral adaptations in ruminants, ewes were implanted with an intracerebroventricular cannula in the third ventricle and infused over days with artificial cerebrospinal fluid (aCSF), the α-MSH analog melanotan-I (MTI), or AGRP. Infusion of MTI at 0.03 nmol/h reduced intake, expressed as a fold of maintenance energy requirement (M), from 1.8 to 1.1 M (P < 0.0001), whereas AGRP at 0.3 nmol/h increased intake from 1.8 to 2.0 M (P < 0.01); these doses were used in all subsequent experiments. To assess the effect of MTI on plasma variables, sheep were fed ad libitum and infused with aCSF or MTI or pair-fed to MTI-treated sheep and infused with aCSF (aCSFPF). Feed intake of the MTI and aCSFPF groups was 40% lower than the aCSF group (P < 0.0001). MTI increased plasma triiodothyronine and thyroxine in an intake-independent manner (P < 0.05 or less) but was devoid of effects on plasma glucose, insulin, and cortisol. None of these variables were altered by AGRP infusion in sheep fed at a fixed intake of 1.6 M. To assess the effect of CNS-MC activation on insulin action, ewes were infused with aCSF or MTI over the last 3 d of a 14-d period when energy intake was limited to 0.3 M and studied under basal conditions and during hyperinsulinemic-euglycemic clamps. MTI had no effect on plasma glucose, plasma insulin, or glucose entry rate under basal conditions but blunted the ability of insulin to inhibit endogenous glucose production during hyperinsulinemic-euglycemic clamps (P < 0.0001). Finally, MTI tended to reduce plasma leptin in sheep fed at 0.3 M (P < 0.08), and this effect became significant at 0.6 M (P < 0.05); MTI had no effect on plasma adiponectin irrespective of feeding level. These data suggest a role for the CNC-MC in regulating metabolic efficiency and peripheral insulin action.

Highly productive ruminants face short-term nutritional deficits during demanding phases of their life cycle. They remain productive and healthy during these periods through a series of metabolic adaptations. Current models in ruminant biology attribute the coordination of these adaptations to circulating hormones and bioactive metabolites but have not considered the possibility that the central nervous system (CNS) is also involved. The latter appears likely given recent work in rodents implicating the CNS-melanocortin system in the regulation of some of these adaptations. To test this possibility, mature ewes were surgically implanted with a cannula accessing the brain allowing chronic infusion of melanocortins, and used in experiments assessing peripheral effects. These experiments showed that the CNS-melanocortin system regulates the circulating concentrations of some metabolic hormones as well as the ability of insulin to regulate glucose production. Overall, these studies suggest a role for the CNS-melanocortin system in regulating metabolic adaptations in ruminants.

Evidence for a feeding related association between melanocortin in the NTS and Neuropeptide-Y in the PVN.

Melanocortin and neuropeptide-Y (NPY) are both involved in feeding and energy regulation, and they have opposite effects in the paraventricular nucleus of the hypothalamus (PVN). The present study examined an interaction between melanocortin in the nucleus of the solitary tract (NTS) and NPY in the PVN. Male Sprague-Dawley rats were implanted with cannulae in the injection sites of interest. In Experiment 1, subjects received either the melanocortin 3/4-receptor (MC3/4) antagonist SHU9119 (0, 10, 50 and 100 pmol/0.5 µl) or the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS. Food intake was measured at 1, 2, 4, 6 and 24-h post-injection. Administration of SHU9119 into the NTS significantly and dose-dependently increased food intake at 1, 2, 4, 6 and 6-24-h, and administration of MTII into the NTS significantly and dose-dependently decreased 24-h free feeding. In Experiment 2, subjects received the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS just prior to NPY (0 and 1µg/0.5 µl) in the PVN. PVN injection of NPY stimulated feeding, and administration of MTII (50, 100 and 200 pmol) into the NTS significantly and dose-dependently decreased NPY-induced feeding at 2, 4, 6 and 6-24-h. These data suggest that there could be a neuronal association between melanocortin in the NTS and NPY in the PVN, and that the melanocortin system in the NTS has an antagonistic effect on NPY-induced feeding in the PVN.

The Melanocortin System: A Promising Target for the Development of New Antidepressant Drugs.

Major depression is one of the most prevalent mental disorders, causing significant human suffering and socioeconomic loss. Since conventional antidepressants are not sufficiently effective, there is an urgent need to develop new antidepressant medications. Despite marked advances in the neurobiology of depression, the etiology and pathophysiology of this disease remain poorly understood. Classical and newer hypotheses of depression suggest that an imbalance of brain monoamines, dysregulation of the hypothalamic-pituitary-adrenal axis (HPAA) and immune system, or impaired hippocampal neurogenesis and neurotrophic factors pathways are cause of depression. It is assumed that conventional antidepressants improve these closely related disturbances. The purpose of this review was to discuss the possibility of affecting these disturbances by targeting the melanocortin system, which includes adrenocorticotropic hormone-activated receptors and their peptide ligands (melanocortins). The melanocortin system is involved in the regulation of various processes in the brain and periphery. Melanocortins, including peripherally administered non-corticotropic agonists, regulate HPAA activity, exhibit anti-inflammatory effects, stimulate the levels of neurotrophic factors, and enhance hippocampal neurogenesis and neurotransmission. Therefore, endogenous melanocortins and their analogs are able to complexly affect the functioning of those body's systems that are closely related to depression and the effects of antidepressants, thereby demonstrating a promising antidepressant potential.

Melanocortin MC4R receptor is required for energy expenditure but not blood pressure effects of angiotensin II within the mouse brain.

The brain renin-angiotensin system (RAS) is implicated in control of blood pressure (BP), fluid intake, and energy expenditure (EE). Angiotensin II (ANG II) within the arcuate nucleus of the hypothalamus contributes to control of resting metabolic rate (RMR) and thereby EE through its actions on Agouti-related peptide (AgRP) neurons, which also contribute to EE control by leptin. First, we determined that although leptin stimulates EE in control littermates, mice with transgenic activation of the brain RAS (sRA) exhibit increased EE and leptin has no additive effect to exaggerate EE in these mice. These findings led us to hypothesize that leptin and ANG II in the brain stimulate EE through a shared mechanism. Because AgRP signaling to the melanocortin MC4R receptor contributes to the metabolic effects of leptin, we performed a series of studies examining RMR, fluid intake, and BP responses to ANG II in mice rendered deficient for expression of MC4R via a transcriptional block (Mc4r-TB). These mice were resistant to stimulation of RMR in response to activation of the endogenous brain RAS via chronic deoxycorticosterone acetate (DOCA)-salt treatment, whereas fluid and electrolyte effects remained intact. These mice were also resistant to stimulation of RMR via acute intracerebroventricular (ICV) injection of ANG II, whereas BP responses to ICV ANG II remained intact. Collectively, these data demonstrate that the effects of ANG II within the brain to control RMR and EE are dependent on MC4R signaling, whereas fluid homeostasis and BP responses are independent of MC4R signaling.

Antistress Action of Melanocortin Derivatives Associated with Correction of Gene Expression Patterns in the Hippocampus of Male Rats Following Acute Stress.

Natural melanocortins (MCs) have been used in the successful development of drugs with neuroprotective properties. Here, we studied the behavioral effects and molecular genetic mechanisms of two synthetic MC derivatives-ACTH(4-7)PGP (Semax) and ACTH(6-9)PGP under normal and acute restraint stress (ARS) conditions. Administration of Semax or ACTH(6-9)PGP (100 µg/kg) to rats 30 min before ARS attenuated ARS-induced behavioral alterations. Using high-throughput RNA sequencing (RNA-Seq), we identified 1359 differentially expressed genes (DEGs) in the hippocampus of vehicle-treated rats subjected to ARS, using a cutoff of >1.5 fold change and adjusted p-value (Padj) < 0.05, in samples collected 4.5 h after the ARS. Semax administration produced > 1500 DEGs, whereas ACTH(6-9)PGP administration led to <400 DEGs at 4.5 h after ARS. Nevertheless, ~250 overlapping DEGs were identified, and expression of these DEGs was changed unidirectionally by both peptides under ARS conditions. Modulation of the expression of genes associated with biogenesis, translation of RNA, DNA replication, and immune and nervous system function was produced by both peptides. Furthermore, both peptides upregulated the expression levels of many genes that displayed decreased expression after ARS, and vice versa, the MC peptides downregulated the expression levels of genes that were upregulated by ARS. Consequently, the antistress action of MC peptides may be associated with a correction of gene expression patterns that are disrupted during ARS.

Impact of the Central Histaminergic and Melanocortin Systems on Leptin-Induced Hypophagia in Neonatal Layer Chicken.

The present study aimed to assess the probable impact of the central histaminergic and melanocortin systems on leptin-induced hypophagia in neonatal layer chickens. In experiment 1, the chickens received intracerebroventricular (ICV) injections of the control solution, 250 nmol of α-FMH, 10 µg of leptin, and α-FMH+leptin. Experimental groups 2-8 were injected the same as experiment 1. Nonetheless, the chickens in experiments 2-8 received ICV injections of 300 nmol of chlorpheniramine (H1 receptor antagonist), 82 nmol of famotidine (H2 receptor antagonist), 300 nmol of thioperamide (H3 receptor antagonist), 0.5 nmol of SHU9119 (M3/M4 receptors antagonist), 0.5 nmol of MCL0020 (M4 receptor antagonist), 30 µg of astressin-B (CRF1/ CRF2 receptors antagonist), and 30 µg of astressin2-B (CRF2 receptor antagonist), instead of α-FMH, respectively. Food was provided for the birds immediately following the injection, and 30, 60, and 120 min after the injection, cumulative food intake (g) was measured. The findings pointed out that the ICV injection of leptin diminished food intake in neonatal chickens (P<0.05). The co-administration of M3/M4 receptor antagonist+leptin significantly decreased the hypophagic effect of leptin (P<0.05). A significant decrease was also detected in the hypophagic effect of leptin following the co-administration of the M4 receptor antagonist and leptin (P<0.05). Moreover, the co-injection of the antagonists of CRF1/CRF2 receptors and leptin significantly mitigated the hypophagic effect of leptin (P<0.05). The co-injection of CRF2 receptor antagonist and leptin led to a decrease in the hypophagic effect of leptin. As evidenced by the results of the current study the hypophagic effect of leptin is mediated by the receptors of H1, H3, M3/M4, and CRF1/CRF2 in neonatal layer chicken.

[Melanocortin peptides : Fundamentals, translational research, clinical dermatology, and future perspectives]. / Melanokortinpeptide : Grundlagen, translationale Forschung, klinische Dermatologie und Zukunftsperspektiven.

Melanocortins are peptides that share a common central pharmacophor. Melanin pigmentation of interfollicular epidermis and hair via MC1R remains the key physiologic function of the naturally occurring melanocortin peptides in skin. Moreover, the melanocortins are crucially involved in the ultraviolet light-induced tanning response. Under pathophysiologic conditions, melanocortin peptides induce cutaneous hyperpigmentation, likewise via the MC1R axis, e.g. in patients with Addison's disease, ectopic precursor pro-opiomelanocortin (POMC) syndrome and in those with abnormally elevated melanocortin blood levels. Translational research on α­MSH (melanocyte-stimulating hormones) and their antagonists has further revealed a variety of other biological activities beyond pigmentation. They include cytoprotection, antioxidative effects, regulation of collagen metabolism and fibrosis, sebum production, and cutaneous wound healing. These findings have also promoted the development of novel therapies in clinical dermatology including the exploitation of afamelanotide. In 2015, this agent became the first in-class synthetic α­MSH analogue to be approved in dermatology for the treatment of erythropoetic protoporphyria. In addition to afamelanotide, setmelanotide has recently emerged as a highly selective MC4R agonist useful for the treatment of distinct forms of genetically determined obesity, e.g., POMC deficiency. Future perspectives in dermatology reside in treatment of other difficult-to-treat skin diseases with α­MSH analogues, either with topical or systemic formulations. Moreover, synthetic melanocortin peptide derivatives lacking the central pharmacophor but with maintained anti-inflammatory effects could become a promising strategy for the design of new therapies in dermatology.

The Use of Human Induced Pluripotent Stem Cells for Testing Neuroprotective Activity of Pharmacological Compounds.

Development of therapeutic preparations involves several steps, starting with the synthesis of chemical compounds and testing them in different models for selecting the most effective and safest ones to clinical trials and introduction into medical practice. Cultured animal cells (both primary and transformed) are commonly used as models for compound screening. However, cell models display a number of disadvantages, including insufficient standardization (primary cells) and disruption of cell genotypes (transformed cells). Generation of human induced pluripotent stem cells (IPSCs) offers new possibilities for the development of high-throughput test systems for screening potential therapeutic preparations with different activity spectra. Due to the capacity to differentiate into all cell types of an adult organism, IPSCs are a unique model that allows examining the activity and potential toxicity of tested compounds during the entire differentiation process in vitro. In this work, we demonstrated the efficiency of IPSCs and their neuronal derivatives for selecting substances with the neuroprotective activity using two classes of compounds - melanocortin family peptides and endocannabinoids. None of the tested compounds displayed cyto- or embryotoxicity. Both melanocortin peptides and endocannabinoids exerted neuroprotective effect in the neuronal precursors and IPSC-derived neurons subjected to hydrogen peroxide. The endocannabinoid N-docosahexaenoyl dopamine exhibited the highest neuroprotective effect (~70%) in the differentiated cultures enriched with dopaminergic neurons; the effect of melanocortin Semax was ~40%. The possibility of using other IPSC derivatives for selecting compounds with the neuroprotective activity is discussed.

Melanotan-induced priapism: a hard-earned tan.

Melanocortin analogues, such as melanotan, are illegally used for artificial tanning. They have also been suggested as possible therapeutic agents in the treatment of erectile dysfunction. This case study presents a patient attending the accident and emergency department, in a tertiary urology centre, with acute priapism after abdominal subcutaneous injection of melanotan. The priapism was diagnosed as 'low-flow' and managed with cavernosal aspiration, irrigation and subsequent intracavernosal injection of phenylephrine. The patient avoided requiring surgical shunting but had not yet recovered erectile function at 4-week follow-up. Acute priapism is an unreported side effect of melanocortin analogue use and this case report presents a patient managed without surgical intervention. Future therapeutic application of these agents will need to take this potential life altering complication into consideration.

Are melanocortin peptides future therapeutics for cutaneous wound healing?

Cutaneous wound healing is a complex process divided into different phases, that is an inflammatory, proliferative and remodelling phase. During these phases, a variety of resident skin cell types but also cells of the immune system orchestrate the healing process. In the last year, it has been shown that the majority of cutaneous cell types express the melanocortin 1 receptor (MC1R) that binds α-melanocyte-stimulating hormone (α-MSH) with high affinity and elicits pleiotropic biological effects, for example modulation of inflammation and immune responses, cytoprotection, antioxidative defense and collagen turnover. Truncated α-MSH peptides such as Lys-Pro-Val (KPV) as well as derivatives like Lys-d-Pro-Thr (KdPT), the latter containing the amino acid sequence 193-195 of interleukin-1ß, have been found to possess anti-inflammatory effects but to lack the pigment-inducing activity of α-MSH. We propose here that such peptides are promising future candidates for the treatment of cutaneous wounds and skin ulcers. Experimental approaches in silico, in vitro, ex vivo and in animal models are outlined. This is followed by an unbiased discussion of the pro and contra arguments of such peptides as future candidates for the therapeutic management of cutaneous wounds and a review of the so-far available data on melanocortin peptides and derivatives in wound healing.

Peripherally administered melanocortins induce mice fat browning and prevent obesity.

BACKGROUND/OBJECTIVES: The browning of white adipose tissue (WAT) has been in the spotlight during the last years, becoming an attractive approach to combat obesity. Melanocortin neuropeptides, such as α-melanocyte-stimulating hormone (α-MSH), are well-known regulators of appetite at the central nervous system, but its role in adipocyte metabolism is poorly elucidated. This study sought to verify if α-MSH can induce transdifferentiation of white to brown/beige adipocytes and to determine whether it can ameliorate the obesity phenotype. METHODS: The browning effect of α-MSH was determined in isolated adipocytes using the 3T3-L1 cell line and in inguinal subcutaneous adipose tissue (ingWAT) of diet-induced obese (DIO) mice by quantifying the expression of browning hallmark genes, oxygen consumption, and mitochondrial biogenesis. α-MSH protection from diet-induced obesity was evaluated by analyzing mice body weight, fat mass, and lipid and glucose serum profiles. RESULTS: Here, we report that α-MSH activates a thermogenic gene program and increases the mitochondrial respiratory rate in 3T3-L1 adipocytes and ingWAT of DIO mice. Without affecting food intake, peripheral administration of α-MSH decreases body weight and ingWAT mass, promoting a significant rise in the number of smaller adipocytes, whereas it lowered the larger ones. Additionally, there was an increase in the mass of brown adipose tissue. Browning activation occurs concomitantly with improvement on serum lipid profile, insulin resistance, and glucose homeostasis. CONCLUSIONS: This study highlights the anti-obesity properties of melanocortins by promoting ingWAT browning and provides new perspectives for future designing of more effective therapeutic strategies.

Food Perception Primes Hepatic ER Homeostasis via Melanocortin-Dependent Control of mTOR Activation.

Adaptation of liver to the postprandial state requires coordinated regulation of protein synthesis and folding aligned with changes in lipid metabolism. Here we demonstrate that sensory food perception is sufficient to elicit early activation of hepatic mTOR signaling, Xbp1 splicing, increased expression of ER-stress genes, and phosphatidylcholine synthesis, which translate into a rapid morphological ER remodeling. These responses overlap with those activated during refeeding, where they are maintained and constantly increased upon nutrient supply. Sensory food perception activates POMC neurons in the hypothalamus, optogenetic activation of POMC neurons activates hepatic mTOR signaling and Xbp1 splicing, whereas lack of MC4R expression attenuates these responses to sensory food perception. Chemogenetic POMC-neuron activation promotes sympathetic nerve activity (SNA) subserving the liver, and norepinephrine evokes the same responses in hepatocytes in vitro and in liver in vivo as observed upon sensory food perception. Collectively, our experiments unravel that sensory food perception coordinately primes postprandial liver ER adaption through a melanocortin-SNA-mTOR-Xbp1s axis. VIDEO ABSTRACT.

Lorcaserin improves glycemic control via a melanocortin neurocircuit.

OBJECTIVE: The increasing prevalence of type 2 diabetes (T2D) and associated morbidity and mortality emphasizes the need for a more complete understanding of the mechanisms mediating glucose homeostasis to accelerate the identification of new medications. Recent reports indicate that the obesity medication lorcaserin, a 5-hydroxytryptamine (5-HT, serotonin) 2C receptor (5-HT2CR) agonist, improves glycemic control in association with weight loss in obese patients with T2D. Here we evaluate whether lorcaserin has an effect on glycemia without body weight loss and how this effect is achieved. METHODS: Murine models of common and genetic T2D were utilized to probe the direct effect of lorcaserin on glycemic control. RESULTS: Lorcaserin dose-dependently improves glycemic control in mouse models of T2D in the absence of reductions in food intake or body weight. Examining the mechanism of this effect, we reveal a necessary and sufficient neurochemical mediator of lorcaserin's glucoregulatory effects, brain pro-opiomelanocortin (POMC) peptides. To clarify further lorcaserin's therapeutic brain circuit, we examined the receptor target of POMC peptides. We demonstrate that lorcaserin requires functional melanocortin4 receptors on cholinergic preganglionic neurons (MC4RChAT) to exert its effects on glucose homeostasis. In contrast, MC4RChAT signaling did not impact lorcaserin's effects on feeding, indicating a divergence in the neurocircuitry underpinning lorcaserin's therapeutic glycemic and anorectic effects. Hyperinsulinemic-euglycemic clamp studies reveal that lorcaserin reduces hepatic glucose production, increases glucose disposal and improves insulin sensitivity. CONCLUSIONS: These data suggest that lorcaserin's action within the brain represents a mechanistically novel treatment for T2D: findings of significance to a prevalent global disease.

Bench-top to clinical therapies: A review of melanocortin ligands from 1954 to 2016.

The discovery of the endogenous melanocortin agonists in the 1950s have resulted in sixty years of melanocortin ligand research. Early efforts involved truncations or select modifications of the naturally occurring agonists leading to the development of many potent and selective ligands. With the identification and cloning of the five known melanocortin receptors, many ligands were improved upon through bench-top in vitro assays. Optimization of select properties resulted in ligands adopted as clinical candidates. A summary of every melanocortin ligand is outside the scope of this review. Instead, this review will focus on the following topics: classic melanocortin ligands, selective ligands, small molecule (non-peptide) ligands, ligands with sex-specific effects, bivalent and multivalent ligands, and ligands advanced to clinical trials. Each topic area will be summarized with current references to update the melanocortin field on recent progress. This article is part of a Special Issue entitled: Melanocortin Receptors - edited by Ya-Xiong Tao.

Neural Programmatic Role of Leptin, TNFα, Melanocortin, and Glutamate in Blood Pressure Regulation vs Obesity-Related Hypertension in Male C57BL/6 Mice.

Continuous nutritional surplus sets the stage for hypertension development. Whereas moderate dietary obesity in mice is normotensive, the homeostatic balance is disrupted concurrent with an increased risk of hypertension. However, it remains unclear how the obesity-associated prehypertensive state is converted into overt hypertension. Here, using mice with high-fat-diet (HFD)-induced moderate obesity vs control diet (CD)-fed lean mice, we comparatively studied the effects of central leptin and tumor necrosis factor-α (TNFα) as well as the involvement of the neuropeptide melanocortin pathway vs the neurotransmitter glutamate pathway. Compared with CD-fed lean mice, the pressor effect of central excess leptin and TNFα, but not melanocortin, was sensitized in HFD-fed mice. The pressor effect of central leptin in HFD-fed mice was strongly suppressed by glutamatergic inhibition but not by melanocortinergic inhibition. The pressor effect of central TNFα was substantially reversed by melanocortinergic inhibition in HFD-fed mice but barely in CD-fed mice. Regardless of diet, the hypertensive effects of central TNFα and melanocortin were both partially reversed by glutamatergic suppression. Hence, neural control of blood pressure is mediated by a signaling network between leptin, TNFα, melanocortin, and glutamate and changes in dynamics due to central excess leptin and TNFα mediate the switch from normal physiology to obesity-related hypertension.

G(q/11)α and G(s)α mediate distinct physiological responses to central melanocortins.

Activation of brain melanocortin 4 receptors (MC4Rs) leads to reduced food intake, increased energy expenditure, increased insulin sensitivity, and reduced linear growth. MC4R effects on energy expenditure and glucose metabolism are primarily mediated by the G protein G(s)α in brain regions outside of the paraventricular nucleus of the hypothalamus (PVN). However, the G protein(s) that is involved in MC4R-mediated suppression of food intake and linear growth, which are believed to be regulated primarily though action in the PVN, is unknown. Here, we show that PVN-specific loss of G(q)α and G11α, which stimulate PLC, leads to severe hyperphagic obesity, increased linear growth, and inactivation of the hypothalamic-pituitary-adrenal axis, without affecting energy expenditure or glucose metabolism. Moreover, we demonstrate that the ability of an MC4R agonist delivered to PVN to inhibit food intake is lost in mice lacking G(q/11)α in the PVN but not in animals deficient for G(s)α. The blood pressure response to the same MC4R agonist was only lost in animals lacking G(s)α specifically in the PVN. Together, our results exemplify how different physiological effects of GPCRs may be mediated by different G proteins and identify a pathway for appetite regulation that could be selectively targeted by G(q/11)α-biased MC4R agonists as a potential treatment for obesity.

Protective effects of the melanocortin analog NDP-α-MSH in rats undergoing cardiac arrest.

We previously reported that melanocortins afford cardioprotection in conditions of experimental myocardial ischemia/reperfusion, with involvement of the janus kinases (JAK), extracellular signal-regulated kinases (ERK) and signal transducers and activators of transcription (STAT) signalings. We investigated the influence of the melanocortin analog [Nle(4), D-Phe(7)]α-melanocyte-stimulating hormone (NDP-α-MSH) on short-term detrimental responses to cardiac arrest (CA) induced in rats by intravenous (i.v.) administration of potassium chloride, followed by cardiopulmonary resuscitation (CPR) plus epinephrine treatment. In CA/CPR rats i.v. treated with epinephrine (0.1 mg/kg) and returned to spontaneous circulation (48%) we recorded low values of mean arterial pressure (MAP) and heart rate (HR), alteration of hemogasanalysis parameters, left ventricle low expression of the cardioprotective transcription factors pJAK2 and pTyr-STAT3 (JAK-dependent), increased oxidative stress, up-regulation of the inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and down-regulation of the anti-inflammatory cytokine IL-10, as assessed at 1h and 3h after CPR. On the other hand, i.v. treatment during CPR with epinephrine plus NDP-α-MSH (340 µg/kg) almost completely restored the basal conditions of MAP and HR, reversed metabolic acidosis, induced left ventricle up-regulation of pJAK2, pTyr-STAT3 and IL-10, attenuated oxidative stress, down-regulated TNF-α and IL-6 levels, and improved survival rate by 81%. CA/CPR plus epinephrine alone or in combination with NDP-α-MSH did not affect left ventricle pSer-STAT3 (ERK1/2-dependent) and pERK1/2 levels. These results indicate that melanocortins improve return to spontaneous circulation, reverse metabolic acidosis, and inhibit heart oxidative stress and inflammatory cascade triggered by CA/CPR, likely via activation of the JAK/STAT signaling pathway.

Melanocortin peptides protect chondrocytes from mechanically induced cartilage injury.

INTRODUCTION: Mechanical injury can greatly influence articular cartilage, propagating inflammation, cell injury and death - risk factors for the development of osteoarthritis. Melanocortin peptides and their receptors mediate anti-inflammatory and pro-resolving mechanisms in chondrocytes. This study aimed to investigate the potential chondroprotective properties of α-MSH and [DTRP(8)]-γ-MSH in mechanically injured cartilage explants, their ability to inhibit pro-inflammatory and stimulate anti-inflammatory cytokines in in situ and in freshly isolated articular chondrocytes. METHODS: The effect of melanocortins on in situ chondrocyte viability was investigated using confocal laser scanning microscopy of bovine articular cartilage explants, subjected to a single blunt impact (1.14N, 6.47 kPa) delivered by a drop tower. Chondroprotective effects of α-MSH, [DTRP(8)]-γ-MSH and dexamethasone on cytokine release by TNF-α-activated freshly isolated articular chondrocytes/mechanically injured cartilage explants were investigated by ELISA. RESULTS: A single impact to cartilage caused discreet areas of chondrocyte death, accompanied by pro-inflammatory cytokine release; both parameters were modulated by α-MSH, [DTRP(8)]-γ-MSH and dexamethasone. Melanocortin pre-treatment of TNF-α-stimulated freshly isolated chondrocytes resulted in a bell-shaped inhibition in IL-1ß, IL-6 and IL-8, and elevation of IL-10 production. The MC3/4 antagonist, SHU9119, abrogated the effect of [DTRP(8)]-γ-MSH but not α-MSH on cytokine release. CONCLUSION: Melanocortin peptide pre-treatment prevented chondrocyte death following mechanical impact to cartilage and led to a marked reduction of pro-inflammatory cytokines, whilst prompting the production of anti-inflammatory/pro-resolving cytokine IL-10. Development of small molecule agonists towards melanocortin receptors could thus be a viable approach for preventing chondrocyte inflammation and death within cartilage and represent an alternative approach for the treatment of osteoarthritis.

Melanocortins protect against progression of Alzheimer's disease in triple-transgenic mice by targeting multiple pathophysiological pathways.

Besides specific triggering causes, Alzheimer's disease (AD) involves pathophysiological pathways that are common to acute and chronic neurodegenerative disorders. Melanocortins induce neuroprotection in experimental acute neurodegenerative conditions, and low melanocortin levels have been found in occasional studies performed in AD-type dementia patients. Here we investigated the possible neuroprotective role of melanocortins in a chronic neurodegenerative disorder, AD, by using 12-week-old (at the start of the study) triple-transgenic (3xTg-AD) mice harboring human transgenes APPSwe, PS1M146V, and tauP301L. Treatment of 3xTg-AD mice, once daily until the end of the study (30 weeks of age), with the melanocortin analog [Nle(4),D-Phe(7)]-α-melanocyte-stimulating hormone (NDP-α-MSH) reduced cerebral cortex/hippocampus phosphorylation/level of all AD-related biomarkers investigated (mediators of amyloid/tau cascade, oxidative/nitrosative stress, inflammation, apoptosis), decreased neuronal loss, induced over-expression of the synaptic activity-dependent gene Zif268, and improved cognitive functions, relative to saline-treated 3xTg-AD mice. Pharmacological blockade of melanocortin MC4 receptors prevented all neuroprotective effects of NDP-α-MSH. Our study identifies, for the first time, a class of drugs, MC4 receptor-stimulating melanocortins, that are able to counteract the progression of experimental AD by targeting pathophysiological mechanisms up- and down-stream of ß-amyloid and tau. These data could have important clinical implications.