Elevated concentrations of plasma alpha-melanocyte stimulating hormone are associated with reduced disease progression in HIV-infected patients

Resolution pharmacology and the treatment of infectious diseases

Inflammation is elicited by the host in response to microbes, and is believed to be essential for protection against infection. However, we have previously hypothesized that excessive or misplaced inflammation may be a major contributor to tissue dysfunction and death associated with viral and bacterial infections. The resolutive phase of inflammation is a necessary condition to achieve homeostasis after acute inflammation. It is possible that targeting inflammation resolution may be beneficial for the host during infection. In this review, we summarize the evidence demonstrating the expression, roles and effects of the best described pro-resolving molecules in the context of bacterial and viral infections. Pro-resolving molecules play a pivotal role in modulating a spectrum of pathways associated with tissue inflammation and damage during both viral and bacterial infections. These molecules offer a blend of anti-inflammatory, pro-resolving and sometimes anti-infective benefits, all the while circumventing the undesired and immune-suppressive unwanted effects associated with glucocorticoids. Whether these beneficial effects will translate into benefits to patients clearly deserve further investigation.

The increase of alpha-melanocyte-stimulating hormone in the plasma of chronic fatigue syndrome patients

Background

Despite extensive research, no reliable biological marker for chronic fatigue syndrome (CFS) has yet been identified. However, hyperactivation of melanotrophs in the pituitary gland and increased levels of plasma alpha-melanocyte-stimulating hormone (α-MSH) have recently been detected in an animal model of chronic stress. Because CFS is considered to be caused partly by chronic stress events, increased α-MSH plasma levels may also occur in CFS patients. We therefore examined α-MSH levels in CFS patients.

Methods

Fifty-five CFS patients, who were previously diagnosed within 10 years of with the disease, were enrolled in this study. Thirty healthy volunteers were studied as controls. Fasting bloods samples were collected in the morning and evaluated for their plasma levels of α-MSH, adrenocorticotropic hormone (ACTH), serum cortisol and dehydroepiandrosterone sulfate (DHEA-S). Mean levels of α-MSH were compared between the CFS and control groups using Welch's t test.

Results

The mean plasma α-MSH concentration in the CFS group (17.9 ± 1.0 pg/mL) was significantly higher than that in healthy controls (14.5 ± 1.0 pg/mL, p = 0.02). However, there was a wide range of values in the CFS group. The factors correlated with the plasma α-MSH values were analyzed using Spearman's rank correlation. A negative correlation was found between the duration of the CFS and the plasma α-MSH values (p = 0.04, r_s = -0.28), but no correlations with ACTH, cortisol or DHEA-S levels were identified (p = 0.55, 0.26, 0.33, respectively). The CFS patients were divided into two groups: patients diagnosed for ≤ 5 years' duration, and those diagnosed for 5-10 years' duration. They were compared with the healthy controls using one-way ANOVA and Tukey-Kramer multiple comparison tests. The mean α-MSH concentration in the ≤ 5 years group was 20.8 ± 1.2 pg/mL, which was significantly higher than that in the healthy controls (p < 0.01). There was no significant difference between the 5-10 year group (15.6 ± 1.4 pg/mL) and the healthy controls.

Conclusions

CFS patients with a disease duration of ≤ 5 years had significantly higher levels of α-MSH in their peripheral blood. α-MSH could be a potent biological marker for the diagnosis of CFS, at least during the first 5 years after onset of the disease.

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.

Central neurotranspeptide, alpha-melanocyte-stimulating hormone (alpha-MSH) is upregulated in patients with congestive heart failure

BACKGROUND

Alpha-melanocyte-stimulating hormone (alpha-MSH), a pro-opiomelanocortin (POMC) derivative, is a neuropeptide with potent anti-inflammatory properties that inhibits tissue injury in a wide array of inflammation models.

OBJECTIVE

To determine if alpha-MSH is involved in the development of congestive heart failure (CHF) with the specific aim of examining its peripheral source and one of the mechanisms.

METHODS

The circulating levels of alpha-MSH were measured in 115 patients with CHF using a double-antibody radioimmunoassay. To determine one of the sources of circulating alpha-MSH, human peripheral blood mononuclear cells (PBMC) were stimulated with lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-alpha. Furthermore, to clarify one of the functions of alpha-MSH, PBMC were cultured in the presence or absence of alpha-MSH.

RESULTS

Plasma levels of alpha-MSH were significantly higher in NYHA class II patients with CHF than in control subjects (p<0.0001). A significant correlation was found between the levels of alpha-MSH and high-sensitive testing for C-reactive protein in patients with CHF (r=0.41, p<0.0005). PBMC stimulated with LPS or TNF-alpha released alpha-MSH in a concentration-dependent manner. alpha-MSH inhibited LPS-induced TNF-alpha production, and alpha-MSH simultaneously augmented production of interleukin (IL)-10 by PBMC.

CONCLUSIONS

Circulating alpha-MSH was increased in patients with CHF. Inflammatory response induced alpha-MSH production in cultured human PBMC. Treatment of alpha-MSH could modify the immunobalance between inflammatory and anti-inflammatory responses in cultured PBMC. These findings suggest that alpha-MSH may play an important role in the pathophysiology of CHF.

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.

New aspects on the melanocortins and their receptors

Knowledge of melanocortins and their receptors has increased tremendously over the last few years. The cloning of five melanocortin receptors, and the discovery of two endogenous antagonists for these receptors, agouti and agouti-related peptide, have sparked intense interest in the field. Here we give a comprehensive review of the pharmacology, physiology and molecular biology of the melanocortins and their receptors. In particular, we review the roles of the melanocortins in the immune system, behaviour, feeding, the cardiovascular system and melanoma. Moreover, evidence is discussed suggesting that while many of the actions of the melanocortins are mediated via melanocortin receptors, some appear to be mediated via mechanisms distinct from melanocortin receptors.

Elevated plasma levels of alpha-melanocyte stimulating hormone (alpha-MSH) are correlated with insulin resistance in obese men

OBJECTIVE

The role of alpha-melanocyte stimulating hormone (MSH) in obesity has been well-documented. However, circulating alpha-MSH concentrations in obese men and their relationship with clinical indicators of obesity and glucose metabolism have not as yet been evaluated.

METHODS

We measured the plasma concentrations of alpha-MSH in 15 obese and 15 non-obese male subjects. The relationship of the plasma concentrations of alpha-MSH with body mass index (BMI), body fat mass (measured by bioelectric impedance), body fat distribution (measured by computed tomography), insulin levels, insulin resistance (assessed by the glucose infusion rate (GIR) during an euglycemic hyperinsulinemic clamp study) and with the serum concentrations of leptin and TNF-alpha were also evaluated.

RESULTS

In obese men, the plasma alpha-MSH concentrations were significantly increased compared with those in non-obese men (P< 0.02). The plasma levels of alpha-MSH were positively correlated with BMI (r= 0.560, P< 0.05), fasting insulin levels (r=0.528, P< 0.05) and with visceral fat area (r=0.716, P<0.01), but negatively correlated with GIR (r= -0.625, P< 0.02) in obese male subjects. There were significant correlations between plasma concentrations of alpha-MSH and visceral fat area (r=0.631, P< 0.02), and GIR (r = -0.549, P< 0.05) in non-obese male subjects. Circulating concentrations of alpha-MSH were not significantly correlated with the serum concentrations of leptin and TNF-alpha in both obese and non-obese men.

CONCLUSION

Circulating concentrations of alpha-MSH are significantly increased and correlated with insulin resistance in obese men.

Alpha-melanocyte-stimulating hormone in normal human physiology and disease states

Over the past two decades, research in animal models has indicated that alpha-melanocyte-stimulating hormone (alpha-MSH) has potent anti-inflammatory properties. Furthermore, recent data show that the peptide has antimicrobial effects and probably contributes to innate immunity. alpha-MSH, which is produced by many extrapituitary human cells, should no longer be considered solely a pituitary hormone; rather, it should be viewed as a ubiquitous modulatory peptide.