The effect of alpha-melanocyte stimulating hormone on endotoxin-induced intestinal injury

The Melanocortin System in Inflammatory Bowel Diseases: Insights into Its Mechanisms and Therapeutic Potentials

The melanocortin system is a complex set of molecular mediators and receptors involved in many physiological and homeostatic processes. These include the regulation of melanogenesis, steroidogenesis, neuromodulation and the modulation of inflammatory processes. In the latter context, the system has assumed importance in conditions of chronic digestive inflammation, such as inflammatory bowel diseases (IBD), in which numerous experiences have been accumulated in mouse models of colitis. Indeed, information on how such a system can counteract colitis inflammation and intervene in the complex cytokine imbalance in the intestinal microenvironment affected by chronic inflammatory damage has emerged. This review summarises the evidence acquired so far and highlights that molecules interfering with the melanocortin system could represent new drugs for treating IBD.

Nitric oxide donors in sepsis: a systematic review of clinical and in vivo preclinical data

An abundant literature in the field of sepsis focuses on the role of NO. Inhibiting NO synthesis corrects certain hemodynamic parameters of septic shock but failed to improve outcome in patients. Conversely, administration of NO donors lowers blood pressure but restores microcirculatory flow in patients with sepsis. We undertook a systematic review of the literature to comprehensively summarize the results of studies exploring the effects of systemic NO donors in sepsis. We included both clinical and preclinical data. We described the details surrounding NO donor administration, and the results obtained in each study were regrouped in broad categories. In the case of animal research, we limited our data collection to in vivo protocols and described the sepsis model. Finally, we critically appraised all the studies included in the review. Overall, the reviewed publications aimed for physiopathological description rather than clinical relevance and did not meet the required criteria for extrapolation to clinical practice. With this reserve, NO donors usually improved the outcomes measured (e.g., mortality, pulmonary hypertension, tissue/organ perfusion, etc.) but also lowered blood pressure. We conclude that our findings warrant further animal experimentation designed to maximize clinical relevance.

The effect of alpha-melanocyte stimulating hormone on gentamicin-induced acute nephrotoxicity in rats

The effect of alpha-melanocyte stimulating hormone (alpha-MSH) was investigated on gentamicin-induced acute renal injury in rats. Sprague-Dawley rats (200-250 g; n = 8-10) were treated with gentamicin sulphate (GEN; 80 mg kg(-1)) or saline intraperitoneally for 7 consecutive days. alpha-MSH was administered at a dose of 25 microg rat(-1) day(-1) following GEN or saline injections. On day 8, all animals were decapitated. Trunk blood and 24 h urine were collected to measure the serum creatinine levels, blood urea nitrogen (BUN) levels and to calculate the creatinine clearance values. The kidneys were excised for histological evaluation and for the measurement of malondialdehyde (MDA) levels, glutathione (GSH) contents and myeloperoxidase (MPO) activity. Treatment with alpha-MSH reduced the severity of the renal lesions microscopically, decreased MDA content and MPO activity and restored GSH in kidney samples. However, it did not restore the impaired renal function tests due to GEN challenge. In conclusion, alpha-MSH treatment has a beneficial effect on GEN-induced acute nephrotoxicity, as confirmed by histological evaluation and biochemical assays; but it does not improve GEN-induced renal dysfunction. The mechanism of the protective effect could be attributed, at least in part, to decreased tissue leukocyte infiltration and thus, to decreased oxygen-derived reactive metabolite production.

Gastric protection by α-melanocyte-stimulating hormone against ethanol in rats: Involvement of somatostatin

The proopiomelanocortin-derived tridecapeptide alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide that exerts broad anti-inflammatory actions in mammals. This study aimed to investigate the effect of alpha-MSH on ethanol-induced gastric ulcer in rats and to evaluate the involvement of endogenous somatostatin in the actions of the peptide. The rats received 1 mL 75% ethanol or saline orally. alpha-MSH was given (25 micro g/rat; i.p.) alone or following the somatostatin antagonist cyclo-(7-aminoheptanoyl-PH-E-d-Trp-Lys-THR) (10 microM/kg; i.p.) administration. Gastric lesions were scored macroscopically and microscopically following decapitation at 30 min after ethanol challenge. Gastric malondialdehyde (MDA) level, myeloperoxidase (MPO) activity and mast cell counts were assessed. Ethanol-induced gastric hemorrhagic lesions were characterized by increased gastric MDA level, MPO activity and mast cell counts. alpha-MSH treatment decreased the extent of tissue injury and reversed tissue MDA level, MPO activity and mast cell counts. The effect of the peptide on the severity of gastric lesions, MDA level and MPO activity was reversed by the somatostatin antagonist. In conclusion, alpha-MSH is beneficial in a rat model of gastric ulcer via mechanisms which partly involve the endogenous somatostatin.

Role of the melanocortin system in inflammation

In recent years, scientific interest in melanocortins (MC) has progressively increased due to their wide range of effects and expression on various tissues. Primarily discovered as mediators of skin pigmentation, recent research has shown their important roles in various body functions, such as energy homeostasis, sexual function, and inflammation. The anti-inflammatory and immunomodulatory properties discovered so far have led to the hypothesis that alpha-melanocyte-stimulating hormone (MSH) and its cognate receptors might present potential anti-inflammatory treatment options.

The melanocortin system in leukocyte biology

The melanocortin system is composed of the melanocortin peptides, adrenocorticotropic hormone and alpha-, beta-, and gamma-melanocyte-stimulating hormone, the melanocortin receptors (MCRs), and the endogenous antagonists agouti- and agouti-related protein. Melanocortin peptides exert multiple effects upon the host, including anti-inflammatory and immunomodulatory effects. Leukocytes are a source of melanocortins and a major target for these peptides. Because of reduced translocation of the nuclear factor NF-kappaB to the nucleus, MCR activation by their ligands causes a collective reduction of the most important molecules involved in the inflammatory process. This review examines how melanocortin peptides and their receptors participate in leukocyte biology.

Targeting melanocortin receptors as potential novel therapeutics

Adrenocorticotrophic hormone (ACTH(1-39)) and the melanocortins (alpha, beta and gamma-melanocyte-stimulating hormone [MSH]) are derived from a larger precursor molecule known as the pro-opiomelanocortin (POMC) protein. They exert their numerous biological effects by activating 7 transmembrane G-protein coupled receptors (GPCR), leading to adenylyl cyclase activation and subsequent cAMP accumulation within the target cell. To date, 5 melanocortin receptors (MCR) have been identified and termed MC1R to MC5R, they have been shown to have a wide and varied distribution throughout the body, being found in the central nervous system (CNS), periphery and immune cells. Melanocortins have a multitude of actions including: (i) modulating disease pathologies including arthritis, asthma, obesity; (ii) affecting functions, for example erectile dysfunction, skin tanning; and (iii) organ systems, for example cardiovascular system. Recently a mechanistic approach has been identified with alpha-MSH preventing NF-kappaB activation via the preservation and expression of IkappaBalphaprotein. This leads to a reduction of pro-inflammatory mediators including cytokines and inhibition of adhesion molecule expression, with subsequent reduction in leukocyte emigration. Development of selective ligands with an appropriate pharmacokinetic profile will enable a pharmacological evaluation of the potential beneficial effects of the melanocortins. In this review I have discussed the potential mechanistic action for the melanocortins and some of the disease pathologies shown to be modulated. This review proposes targeting the MCR with the ultimate aim of controlling many of the diseases that we face today.

Comparative analysis of the neuronal activation and cardiovascular effects of nitroglycerin, sodium nitroprusside and l-arginine

In this study, we compare the biological effects, Fos expression and cardiovascular responses induced in the rat, of different nitric oxide modulators (nitroglycerin, sodium nitroprusside and L-arginine). Nitroglycerin and sodium nitroprusside induced a similar pattern of neuronal activation in several areas, which include the paraventricular and supraoptic nuclei of the hypothalamus, central nucleus of the amygdala, parabrachial nucleus, locus coeruleus, ventrolateral medulla and nucleus tractus solitarius. However, only nitroglycerin activated the periaqueductal grey and nucleus trigeminalis caudalis. L-arginine-induced neuronal activation was restricted to the paraventricular and supraoptic nuclei of the hypothalamus. As regards cardiovascular effect, both nitroglycerin and sodium nitroprusside induced moderate hypotension (nitroglycerin: -23.3%, sodium nitroprusside: -24.3%) that lasted 40 min in the case of sodium nitroprusside and 80 min in the case of nitroglycerin. L-arginine did not significantly influence blood pressure. These data suggest that nitroglycerin, sodium nitroprusside and L-arginine are associated with different biological effects on both the central nervous system and the cardiovascular system. Of the NO-related drugs tested in this study, only nitroglycerin confirmed its ability to activate brainstem areas implicated in nociception.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.

Single injection of naked plasmid encoding alpha-melanocyte-stimulating hormone protects against thioacetamide-induced acute liver failure in mice

Oxidative stress has been implicated in the propagation of acute liver injury. The aim of our study was to investigate whether gene transfer of alpha-melanocyte-stimulating hormone (alpha-MSH), a potent anti-inflammatory peptide, could prevent fulminant hepatic failure in mice. Acute liver damage was induced by intraperitoneal administration of thioacetamide. Hydrodynamics-based gene transfection with alpha-MSH expression plasmid via rapid tail vein injection was initiated 1 day prior to intoxication. The mortality in the alpha-MSH-treated mice was significantly lower compared to the vehicle group 3 days after injury. Liver histology significantly improved and TUNEL-positive hepatocytes decreased in the treated mice. The degradation of IkappaBalpha, endogenous inhibitor of nuclear factor kappaB, and upregulation of inducible nitric oxide synthase and tumor necrosis factor-alpha mRNA levels were prevented in the alpha-MSH-treated group, indicating decreased oxidative stress and inflammation. These results suggest alpha-MSH gene therapy might protect against acute hepatic necroinflammatory damage with further potential applications.

Targeting Melanocortin Receptors as a Novel Strategy to Control Inflammation

Adrenocorticotropic hormone and alpha-, beta-, and gamma-melanocyte-stimulating hormones, collectively called melanocortin peptides, exert multiple effects upon the host. These effects range from modulation of fever and inflammation to control of food intake, autonomic functions, and exocrine secretions. Recognition and cloning of five melanocortin receptors (MCRs) has greatly improved understanding of peptide-target cell interactions. Preclinical investigations indicate that activation of certain MCR subtypes, primarily MC1R and MC3R, could be a novel strategy to control inflammatory disorders. As a consequence of reduced translocation of the nuclear factor kappaB to the nucleus, MCR activation causes a collective reduction of the major molecules involved in the inflammatory process. Therefore, anti-inflammatory influences are broad and are not restricted to a specific mediator. Short half-life and lack of selectivity could be an obstacle to the use of the natural melanocortins. However, design and synthesis of new MCR ligands with selective chemical properties are already in progress. This review examines how marshaling MCR could control inflammation.

Alpha-melanocyte stimulating hormone has beneficial effects on cerulein-induced acute pancreatitis

We investigated the effect of alpha-melanocyte stimulating hormone (alpha-MSH) on cerulein induced acute pancreatitis in rats. alpha-MSH treatment (50 microg per rat, intraperitoneally) prior to cerulein reduced the plasma amylase level, pancreatic weight, pancreatic myeloperoxidase activity and the severity of the lesions microscopically. These data suggest that alpha-MSH has a protective effect on cerulein-induced acute pancreatitis and this effect could be attributed, at least in part, to decreased tissue leukocyte infiltration and thus, to decreased pro-inflammatory cytokine production and/or oxygen- and nitrogen-derived reactive metabolite release.

Melanocortin peptides and their receptors: new targets for anti-inflammatory therapy

alpha-Melanocyte stimulating hormone (alpha-MSH) and other melanocortin peptides are potent anti-inflammatory agents that exhibit efficacy in many animal models of acute and chronic inflammation. These peptides are produced both centrally and peripherally, and exert their biological actions via activation of membrane-bound receptors. To exploit the therapeutic potential of such anti-inflammatory peptides, it is essential that the receptor subtype mediating these effects is identified with certainty.