The Neuropeptide Alpha-Melanocyte-Stimulating Hormone Is Critical for Corneal Endothelial Cell Protection and Graft Survival after Transplantation.

Corneal transplantation is the most common form of tissue transplantation. The success of corneal transplantation mainly relies on the integrity of corneal endothelial cells (CEnCs), which maintain tissue transparency by pumping out excess water from the cornea. After transplantation, the rate of CEnC loss far exceeds that seen with normal aging, which can threaten sight. The underlying mechanisms are poorly understood. Alpha-melanocyte-stimulating hormone (α-MSH) is a neuropeptide that is constitutively found in the aqueous humor with both cytoprotective and immunomodulatory effects. The curent study found high expression of melanocortin 1 receptor (MC1R), the receptor for α-MSH, on CEnCs. The effect of α-MSH/MC1R signaling on endothelial function and allograft survival in vitro and in vivo was investigated using MC1R signaling-deficient mice (Mc1re/e mice with a nonfunctional MC1R). Herein, the results indicate that in addition to its well-known immunomodulatory effect, α-MSH has cytoprotective effects on CEnCs after corneal transplantation, and the loss of MC1R signaling significantly decreases long-term graft survival in vivo. In conclusion, α-MSH/MC1R signaling is critical for CEnC function and graft survival after corneal transplantation.

The alpha-melanocyte-stimulating hormone acts as a local immune homeostasis factor in experimental allergic asthma.

BACKGROUND: Originally, the neuropeptide α-melanocyte-stimulating hormone (α-MSH) has been described as a mediator of skin pigmentation. However, recent studies have shown that α-MSH is able to modulate inflammation in various tissues including the lung. So far, it is still not clear whether α-MSH also plays a role in allergic bronchial asthma. OBJECTIVE: This study aimed at investigating the role and regulatory mechanisms of α-MSH in asthma pathogenesis. METHODS: α-MSH levels were measured in bronchoalveolar lavage (BAL) fluid of asthmatic and non-asthmatic individuals as well as of healthy mice and mice with experimental asthma. Wild-type mice were sensitized to ovalbumin (OVA) and exposed to an OVA aerosol in order to induce experimental allergic asthma. α-MSH was administrated intratracheally, the α-MSH antibody intraperitoneally prior each OVA challenge. Airway inflammation, cytokine production, mucus production, airway hyperresponsiveness and receptor expression were assessed. RESULTS: α-MSH levels in BAL of asthmatic individuals and mice were significantly higher compared to healthy controls. In a mouse model of experimental asthma, α-MSH neutralization increased airway inflammation and mucus production, whereas local administration of α-MSH significantly reduced inflammation of the airways. The beneficial effects were further associated with decreased levels of eosinophilic chemoattractant factors that are released by MC5R-positive T helper 2 and airway epithelial cells. CONCLUSION AND CLINICAL RELEVANCE: α-MSH acts as a regulatory factor to maintain local immune homeostasis in allergic bronchial asthma.

Evaluation of the immunogenicity of the synthetic α-melanocyte-stimulating hormone (α-MSH) analogue afamelanotide ([Nle4-D-Phe7]-α-MSH, Scenesse®) in erythropoietic protoporphyria patients by ELISA detecting both anti-afamelanotide and anti-α-MSH antibodies.

UNLABELLED: Afamelanotide is an α-melanocyte-stimulating hormone (α-MSH) agonist with proven efficacy in photodermatoses such as erythropoietic protoporphyria (EPP). This peptide drug, repeatedly administered over prolonged time, may induce anti-drug antibodies (ADA). Here, we describe a new ELISA method developed to monitor the occurrence of ADA against afamelanotide as well as against α-MSH. Covalent binding instead of absorption of antigen onto the microtitre wells prevented antigen leakage and enabled extensive washings followed by lower background. The cut-off between antibody-negative and -positive sera was determined. Inhibition of the antigen-antibody reaction by excess soluble antigen tested for specificity. The sensitivity of the ELISA was 608 and 1,390 ng/ml of specific ADA against afamelanotide and α-MSH, respectively. This ELISA method enabled us to investigate the occurrence of ADA during long-term administration of afamelanotide. No immunoreactivity was found in 23 of the 26 EPP patients exposed to the drug for up to 6 years. Pre-existing immunoreactivity against afamelanotide as well as α-MSH was found in 3 patients, whose titres did not change during afamelanotide administration. CONCLUSION: The new ELISA is suitable to determine ADA against afamelanotide and α-MSH. Afamelanotide did not elicit ADA during long-term administration in patients with EPP.

Prevalence of autoantibodies against some selected growth and appetite-regulating neuropeptides in serum of short children exposed to Candida albicans colonization and/or Helicobacter pylori infection: the molecular mimicry phenomenon.

OBJECTIVES: Many of peptides synthesized in gastrointestinal tract (GI) and adipose tissues, regulate growth and food intake. The GI microflora is an antigenic source. Based on the molecular mimicry hypothesis, intestinal microbe-derived antigens may trigger the production of autoantibodies cross-reacting with some neuropeptides. DESIGN: The aim of the study was to assess whether in idiopathic short stature (ISS) children with Candida albicans (C.albicans) colonisation and/or Helicobacter pylori (H.pylori) infection the autoantibodies (in positive levels) against selected neuropeptides [anti-NP Abs(+)]: ghrelin, leptin, orexin A, αMSH are more prevalent than in Controls. SETTING: The study group comprised 64 children with ISS and 36 children with normal height (Controls). In each child, IgG antibodies against H.pylori, ghrelin, leptin, orexin A and αMSH were assessed in serum, while presence of C.albicans - in stool samples. RESULTS: The higher prevalence of anti-NP Abs(+) in ISS children with C.albicans and/or H.pylori than in normal height children with the colonization in question (34.4% vs 21.1%, p<0.01) was found. The prevalence of anti-NP Abs(+) in groups of children without C.albicans and H.pylori were low, anti-NP Abs(+) were detected in 9.4% of ISS children only, while in Controls they were not found. CONCLUSIONS: In short children with C.albicans and/or H.pylori the incidence of autoantibodies against selected neuropeptides is high. It probably is connected with molecular mimicry between antigens of these microbiota and the mentioned peptides. It is tempting to speculate that presence of cross-reacting autoantibodies against regulatory neuropeptides may results in worse growth velocity. However, further studies are necessary to elucidate this issue.

Psychopathological and personality features in primary Sjogren's syndrome--associations with autoantibodies to neuropeptides.

OBJECTIVES: To determine the spectrum of personality and psychopathology features of patients with primary SS (pSS) and explore whether they are linked to disease characteristics as well as the presence of autoantibodies (autoAbs) against neuropeptides. METHODS: Personality and psychopathological variables were determined in 103 pSS patients and 110 healthy controls (HCs). AutoAbs against hypothalamic and pituitary neuropeptides were measured by ELISA in 25 pSS patients and 25 HCs. Data analysis was performed by univariate and multivariate logistic regression models and by comparison with regression models. RESULTS: A higher number of pSS patients reported distinct personality traits (neuroticism, psychoticism and obsessiveness) and psychological distress compared with HCs. After adjustment for personality characteristics and demographics, only hypochondriasis was the main psychopathology feature associated with pSS, suggesting that psychopathological manifestations in the setting of pSS are primarily dependent on premorbid personality characteristics. Although no differences were detected between serum levels of neuropeptide autoAbs in pSS cases and controls, levels of autoAbs against alpha-melanocyte-stimulating hormone (alpha-MSH) correlated with anxiety scores in both groups examined but with higher intercept in pSS subjects. Significant correlations between anxiety score and autoAbs directed against oxytocin and vasopressin were also detected in the pSS patients. CONCLUSIONS: pSS patients exhibit a distinct pattern of personality traits and high levels of psychological distress compared with HCs, which seems to be determined by premorbid personality characteristics. Correlations between anxiety and alpha-MSH autoAbs suggest their potential involvement in anxiety development in both pSS and HCs.

Ethanol-induced increase of agouti-related protein (AgRP) immunoreactivity in the arcuate nucleus of the hypothalamus of C57BL/6J, but not 129/SvJ, inbred mice.

BACKGROUND: The melanocortin (MC) system is composed of peptides that are cleaved from the polypeptide precursor, pro-opiomelanocortin (POMC). Previous research has shown that MC receptor (MCR) agonists reduce, and MCR antagonists increase, ethanol consumption in rats and mice. Consistently, genetic deletion of the endogenous MCR antagonist, agouti-related protein (AgRP), causes reductions of ethanol-reinforced lever pressing and binge-like ethanol drinking in C57BL/6J mice. Ethanol also has direct effects on the central MC system, as chronic exposure to an ethanol-containing diet causes significant reductions of alpha-melanocyte stimulating hormone (alpha-MSH) immunoreactivity in specific brain regions of Sprague-Dawley rats. Together, these observations suggest that the central MC system modulates neurobiological responses to ethanol. To further characterize the role of the MC system in responses to ethanol, here we compared AgRP and alpha-MSH immunoreactivity in response to an acute injection of saline or ethanol between high ethanol drinking C57BL/6J mice and moderate ethanol drinking 129/SvJ mice. METHODS: Mice received an intraperitoneal (i.p.) injection of ethanol (1.5 g/kg or 3.5 g/kg; mixed in 0.9% saline) or an equivolume of 0.9% saline. Two hours after injection, animals were sacrificed and their brains were processed for AgRP and alpha-MSH immunoreactivity. RESULTS: Results indicated that acute ethanol administration triggered a dose-dependent increase in AgRP immunoreactivity in the arcuate (ARC) of C57BL/6J mice, an effect that was not evident in the 129/SvJ strain. Although acute administration of ethanol did not influence alpha-MSH immunoreactivity, C57BL/6J mice had significantly greater overall alpha-MSH immunoreactivity in the ARC, dorsomedial, and lateral regions of the hypothalamus relative to the 129/SvJ strain. In contrast, C57BL/6J mice displayed significantly lower alpha-MSH immunoreactivity in the medial amygdala. CONCLUSIONS: The results show that acute ethanol exposure has direct effects on endogenous AgRP activity in ethanol preferring C57BL/6J mice. It is suggested that ethanol-induced increases in AgRP may be part of a positive feedback system that stimulates excessive binge-like ethanol drinking in C57BL/6J mice. Inherent differences in alpha-MSH immunoreactivity may contribute to differences in neurobiological responses to ethanol that are characteristically observed between the C57BL/6J and 129/SvJ inbred strains of mice.

Regulation of feeding and anxiety by alpha-MSH reactive autoantibodies.

alpha-Melanocyte-stimulating hormone (alpha-MSH) is a stress-related neuropeptide involved in the regulation of motivated behavior, appetite and emotion including stimulation of satiety and anxiety. Although autoantibodies (autoAbs) reactive with alpha-MSH have been identified in human subjects and in rats, it remained unknown if these autoAbs are involved in the regulation of feeding and anxiety and if their production is related to stress. Here we show that repeated exposure of rats to anxiolytic mild stress by handling increases the levels and affinity of alpha-MSH reactive IgG autoAbs and that these changes are associated with adaptive feeding and anxiety responses during exposure of rats to a strong stress by food restriction. Importantly, an increase in affinity of alpha-MSH reactive autoAbs was associated with changes of their functional roles from stimulation to inhibition of alpha-MSH-mediated behavioural responses, suggesting that these autoAbs can be a carrier or a neutralizing molecule of alpha-MSH peptide, respectively. Using a model of passive transfer into the brain, we show that alpha-MSH autoAbs affinity purified from blood of rats exposed to repeated mild stress, but not from control rats, are able to increase acutely food intake, suppress anxiety and modify gene expression of hypothalamic neuropeptides in naïve rats. These data provide the first evidence that autoAbs reactive with alpha-MSH are involved in the physiological regulation of feeding and mood, supporting a further role of the immune system in the control of motivated behavior and adaptation to stress.

Dermal microdialysis of inflammatory markers induced by aliphatic hydrocarbons in rats.

In the present study we made an attempt to understand the skin irritation cascade of selected aliphatic hydrocarbons using microdialysis technique. Microdialysis probes were inserted into dermis in the dorsal skin of hairless rats. After 2h of probes insertion, occlusive dermal exposure (2h) was carried out with 230 microl of nonane, dodecane and tetradecane, using Hill top chambers((R)). Inflammatory biomarkers such as substance P (SP), alpha-melanocyte stimulating hormone (alpha-MSH) Interleukin 6 (IL-6) and prostaglandin E2 (PGE(2)) were analyzed in the dialysis samples by enzyme immunoassay (EIA). SP, alpha-MSH and IL6 were released in significant amounts following the dermal exposure of nonane and dodecane, whereas tetradecane did not induce any of these markers in significant amounts compared to control. Nonane increased the PGE(2) levels in significant amounts within 2h of chemical exposure compared to dodecane and tetradecane. IL-6 response was found to be slow and 2-3-fold increase in IL-6 levels was observed after 5h following nonane and dodecane application. The magnitude of skin irritation exerted by all three chemicals was in the order of nonane>or=dodecane>or=tetradecane. The results demonstrate that microdialysis can be used to measure the inflammatory biomarkers in the skin irritation studies and irritation response of chemicals was quantifiable by this method. In conclusion, microdialysis was found to be an excellent tool to measure several inflammatory biomarkers as a function of time after dermal exposures with irritant chemicals.

Immunoglobulin G modulation of the melanocortin 4 receptor signaling in obesity and eating disorders.

Melanocortin 4 receptor (MC4R) plays a key role in regulation of appetite activated by its main ligand α-melanocyte-stimulating hormone (α-MSH) in both central and peripheral targets. α-MSH also binds to circulating immunoglobulins (Igs) but the functional significance of such immune complexes (ICs) in MC4R signaling in normal and pathological conditions of altered appetite has remained unknown. To address this question, we analyzed plasma levels, affinity kinetics, and binding epitopes of α-MSH-reactive IgG extracted from plasma samples of female patients with hyperphagic obesity, anorexia nervosa, bulimia nervosa, binge-eating disorder, and healthy controls. Ability of α-MSH/IgG IC to bind and activate human MC4R were studied in vitro and to influence feeding behavior in vivo in rodents. We found that α-MSH-reactive IgG were low in obese but increased in anorectic and bulimic patients and displayed different epitope and kinetics of IC formation. Importantly, while α-MSH/IgG IC from all subjects were binding and activating MC4R, the receptor binding affinity was decreased in obesity. Additionally, α-MSH/IgG IC had lower MC4R-mediated cAMP activation threshold as compared with α-MSH alone in all but not obese subjects. Furthermore, the cellular internalization rate of α-MSH/IgG IC by MC4R-expressing cells was decreased in obese but increased in patients with anorexia nervosa. Moreover, IgG from obese patients prevented central anorexigenic effect of α-MSH. These findings reveal that MC4R is physiologically activated by IC formed by α-MSH/IgG and that different levels and molecular properties of α-MSH-reactive IgG underlie biological activity of such IC relevant to altered appetite in obesity and eating disorders.

Emerging role of autoantibodies against appetite-regulating neuropeptides in eating disorders.

OBJECTIVE: Recent findings of autoantibodies directed against melanocortin peptides suggest that these autoantibodies may represent a source of variability in peptidergic signaling that can be responsible for altered appetite and emotion in eating disorders. However, it is still unknown if autoantibodies directed against some other appetite-regulating neuropeptides and peptide hormones exist in healthy human subjects and if these autoantibodies can regulate appetite and emotion. METHODS: We determined the presence of autoantibodies against some key appetite-regulating neuropeptides and peptide hormones in sera of human subjects and in rats, and used animal models to study the role of alpha-melanocyte-stimulating hormone autoantibodies in food intake and anxiety. RESULTS: Immunoglobulin G and A autoantibodies against alpha-melanocyte-stimulating hormone, neuropeptide Y, agouti-related protein, ghrelin, leptin, and some other neuropeptides or peptide hormones involved in appetite control were present in healthy humans and rats. Animal models including active and passive transfer showed that alpha-melanocyte-stimulating hormone autoantibodies are involved in the regulation of feeding and anxiety. Sequence homology was found between neuropeptides and proteins from some members of intestinal microflora, whereas germ-free rats showed altered levels of autoantibodies directed against several neuropeptides. CONCLUSION: Autoantibodies directed against appetite-regulating neuropeptides and peptide hormones are emerging as important participants in the peptidergic mechanisms controlling motivated behavior. Furthermore, these autoantibodies could provide a link in the gut-brain axis and may represent new biological targets for the diagnosis and treatment of eating disorders.

Proopiomelanocortin-derived peptides are synthesized and released by human keratinocytes.

Proopiomelanocortin (POMC), the precursor for melanotropic, corticotropic, and opioid peptides such as alpha-melanocyte-stimulating hormone (alpha MSH), ACTH, and other related peptides, was originally identified as a product of the pituitary gland. However, recent evidence shows that POMC products can also be produced by nonpituitary tissues. Because keratinocytes, the major constituent of the epidermis exhibit the capacity to release a variety of proinflammatory and immunomodulatory mediators, the present study was performed to investigate whether human keratinocytes are able to produce POMC-derived peptides. Supernatants of human normal keratinocytes and an epidermal carcinoma cell line (A431) contained significant levels of immunoreactive alpha MSH and ACTH. Upon immuneprecipitation and size-exclusion chromatography, keratinocyte-derived alpha MSH exhibited a molecular mass of approximately 1 kD and was biologically active as demonstrated in a tyrosinase bioassay. Northern blot analysis revealed the expression of POMC-specific transcripts (1.3 kb) in both normal keratinocytes and A431 cells. The production of alpha MSH and ACTH could be significantly upregulated both at the protein and mRNA level upon treatment with phorbol myristate acetate, ultraviolet light, or interleukin 1. These data provide first evidence that human keratinocytes produce POMC-derived peptides such as alpha MSH and ACTH. Because POMC-derived peptides recently have been recognized as potent immunomodulatory mediators, their presence in the epidermis may have a major impact on the skin immune system.

In vitro generated autoimmune regulatory T cells enhance intravitreous allogeneic retinal graft survival.

PURPOSE: The authors demonstrated that in vitro-generated alpha-melanocyte stimulated hormone (MSH)-induced Treg cells specific to ocular autoantigen suppress ocular autoimmune disease in vivo when adoptively transferred. They examined the possibility of using these ocular autoantigen-specific Treg cells to promote the survival of a retinal allograft placed in the mouse vitreous. METHODS: Enhanced green fluorescent protein (eGFP)-C57BL/6 neonatal retinal microaggregates were injected into the vitreous of B10-RIII mice before the adoptive transfer of interphotoreceptor retinoid-binding protein (IRBP; an ocular antigen) or ovalbumin (OVA)-specific alpha-MSH-induced Treg cells. GFP transplants were imaged in vivo on days 7 and 12. In addition, on day 12, the eyes were cryosectioned and immunostained with a panel of neuronal and immune cell markers. RESULTS: GFP allografts underwent no detectable changes in size on days 7 and 12 in the B10-RIII mice injected with IRBP-specific Treg cells; however, mice that received OVA-specific Treg cells or no Treg cells experienced remarkable reductions in graft size on day 12. Only one quarter of the original size was seen. Using neuronal-specific markers, immunohistochemistry showed that the architecture of the retinal allografts in the IRBP Treg cell-injected group had intact rosettes and neuronal cells on the outermost layer, whereas the allografts in the OVA Treg cell-injected mice were disorganized. Immune cell-specific markers demonstrated that Treg cells and activated microglial cells were found in the retinal allografts of the mice injected with IRBP Treg cells, but not in the retinal allografts of the OVA Treg-injected mice. CONCLUSIONS: These results demonstrate that adoptive transfer of alpha-MSH-generated IRBP-specific Treg cells promotes retinal allograft survival and development.

Evidence for hypothalamic dysregulation in mouse models of anorexia as well as in humans.

Eating disorders constitute major medical health problems in the western world. Even though little is known about the molecular mechanisms behind abnormal eating behavior, it has become clear that the central nervous system (CNS), particularly the hypothalamus, plays a significant role. The anorexic anx/anx mouse is a unique model for studying food intake and energy expenditure. The anx mutation is linked to marked alterations in hypothalamic distributions of signal substances known to have potent regulatory roles in the control of food intake. Another mouse model that displays an anorectic phenotype similar to the anx/anx mouse is the Contactin KO mouse. This model displays very similar hypothalamic alterations as seen in the anx/anx mouse, arguing for a role of these specific hypothalamic changes in an anorectic phenotype. In human eating disorders, hypothalamic systems corresponding to those defective in mouse models could be compromised since autoantibodies against melanocortin peptides have been detected in anorectic and bulimic patients. These findings represent research avenues that may lead to a better understanding of eating disorders and development of targeted therapeutic approaches.

Aggressive behavior linked to corticotropin-reactive autoantibodies.

BACKGROUND: Altered stress response is characteristic for subjects with abnormal aggressive and antisocial behavior, but the underlying biological mechanisms are unclear. We hypothesized that autoantibodies (autoAbs) directed against several stress-related neurohormones may exist in aggressive subjects. METHODS: Using enzyme-linked immunosorbent assay, we studied whether autoAbs directed against corticotropin (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), oxytocin, and vasopressin are present in serum of male subjects with conduct disorder and prisoners with history of violence. Healthy blood donors served as control subjects. RESULTS: Both conduct disorder and prisoners groups displayed strongly increased levels of ACTH-reactive immunoglobulin G (IgG) and immunoglobulin M (IgM) autoAbs compared with control subjects. Levels of oxytocin-reactive IgM autoAbs were slightly increased in both groups of aggressive subjects, whereas levels of vasopressin-reactive IgG and IgM autoAbs were lower only in conduct disorder. No differences in the levels of alpha-MSH-reactive autoAbs were found between aggressive and control subjects. CONCLUSIONS: High levels of ACTH-reactive autoAbs as well as altered levels of oxytocin- and vasopressin-reactive autoAbs found in aggressive subjects may interfere with the neuroendocrine mechanisms of stress and motivated behavior. Our data suggest a new biological mechanism of human aggressive behavior that involves autoAbs directed against several stress-related neurohormones.

Participation of alpha-melanocyte stimulating hormone in ethanol-induced anxiolysis and withdrawal anxiety in rats.

Although recent reports underscore a close association between the ethanol consumption and the central melanocortin (MC) system in rats, neurobehavioral component of this association has not been explored. In this study, we investigated the role of alpha-melanocyte stimulating hormone (alpha-MSH) in ethanol (1.5-2 g/kg, i.p.) induced anxiolysis and anxiety-like behavior following withdrawal from prolonged ethanol (9% v/v ethanol, 15 days) consumption, using elevated plus maze (EPM) test in rats. While alpha-MSH (1-5 microg/rat, i.c.v.) showed dose-dependent anxiogenic-like effect, the MC4 receptor antagonist HS014 (1-10 nM/rat, i.c.v.) or antiserum against alpha-MSH (1:500-1:50 dilution, 5 microl/rat, i.c.v.) failed to produce any effect in the EPM test. The anxiolytic-like effect of ethanol was suppressed by central administration of alpha-MSH (0.5 microg/rat, i.c.v.). On the other hand, pretreatment with either HS014 (5 nM/rat, i.c.v.) or antiserum against alpha-MSH (1:100 dilution, 5 microl/rat, i.c.v.) enhanced anxiolytic action of ethanol. Moreover, ethanol withdrawal anxiety was markedly blocked by HS014 (1-10 nM/rat, i.c.v.). These results suggest that alpha-MSH may be implicated in ethanol-induced anxiolysis and withdrawal anxiety. These findings also suggest MC4 receptors as possible therapeutic target for development of drugs to address the ethanol withdrawal-related conditions.

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.

Non-pigmentary actions of alpha-melanocyte-stimulating hormone--lessons from the cutaneous melanocortin system.

In the last years the neuropeptide a-melanocyte-stimulating hormone has emerged as a regulator of various biological processes far beyond the initially described pigment-inducing action. Expression of melanocortin-receptors (MC-Rs), mainly MC-1R, has been identified in several non-pigmentary human skin cell types. Moreover, expression of MC-5R has been detected in sebocytes and skin mast cells while MC-4R has been reported in dermal papilla cells, a specialized myofibroblast cell type regulating hair follicle activity. In accordance with early observations in the rat preputial gland alpha-melanocyte-stimulating and related peptides have lipogenic activity in the human system. The immunomodulatory actions of alpha-melanocyte-stimulating include regulation of expression and secretion of chemokines, downregulation of proinflammatory signal-induced NF-kappaB activation and adhesion molecule expression, prostaglandin E2 synthesis, as well as induction of interleukin-10. Depending on the cell type studied and the experimental conditions alpha-melanocyte-stimulating however may also have weak proinflammatory actions. In dermal fibroblasts alpha-melanocyte-stimulating was further reported to modulate collagen metabolism via upregulating interstitial collagenase as well as by attenuating the inductive effect of transforming growth factor B on 1 collagen synthesis and fibrosis, the latter pointing towards a potential role of a-melanocyte-stimulating during chronic inflammatory skin responses. The immunomudulatory effects, the established melanotropic action and the recently identified cytoprotective activity of a-melanocyte-stimulating on UVB-induced apoptosis and DNA damage may be part of the body's host defence in which this neuropeptide--typically induced by proinflammatory signals--maintains tissue homeostasis and prevents genotoxicity during inflammatory responses.

Oral delivery of Bifidobacterium longum expressing α-melanocyte-stimulating hormone to combat ulcerative colitis.

α-Melanocyte-stimulating hormone (α-MSH) is a tridecapeptide derived from pro-opiomelanocortin that exhibits potent anti-inflammatory properties by regulating the production of inflammatory mediators. This peptide has been well established in several inflammatory models, including inflammatory bowel disease (IBD). However, its extremely short duration in vivo limits its clinical application. To address this limitation, Bifidobacterium was used here as a carrier to deliver α-MSH. We utilized α-MSH-engineered Bifidobacterium against IBD, which is closely linked to immune and intestinal microbiota dysfunction. First, we constructed a Bifidobacterium longum secreting α-MSH (B. longum-α-MSH). We then tested the recombinant α-MSH expression and determined its bioactivity in HT-29 cells. To assess its effectiveness, B. longum-α-MSH was used against an ulcerative colitis (UC) model in rats induced by dextran sulfate sodium. The data showed that α-MSH expression in B. longum-α-MSH was effective, and its biological activity was similar to the synthesized one. This UC model experiment indicated that B. longum-α-MSH successfully colonized the intestinal gut, expressed bioactive α-MSH and had a significant anti-inflammatory effect. The results demonstrate the feasibility of preventing IBD by using B. longum-α-MSH.

Sex-related effects of nutritional supplementation of Escherichia coli: relevance to eating disorders.

OBJECTIVES: The biological background of sex-related differences in the development of eating disorders (EDs) is unknown. Recent data showed that gut bacteria Escherichia coli induce autoantibodies against anorexigenic α-melanocyte-stimulating hormone (α-MSH) associated with psychopathology in ED. The aim of this study was to compare the effects of E. coli on feeding and autoantibodies against α-MSH and adrenocorticotropic hormone (ACTH), between female and male rats. METHODS: Commensal E. coli K12 were given in a culture medium daily to adult Wistar rats by intragastric gavage over a 3-wk period; control rats received culture medium only. RESULTS: Before gavage, E. coli K12 DNA was detected in feces of female but not male rats. E. coli provision was accompanied by an increase in body weight gain in females, but a decrease in body weight gain and food intake in males. Independent of E. coli treatment, plasma levels of anti-α-MSH and ACTH immunoglobulin (Ig)G were higher in female than male rats. Females responded to E. coli by increasing α-MSH IgG levels and affinity, but males by increasing α-MSH IgM levels. Affinity of IgG for ACTH was increased in both E. coli-treated females and males, although with different kinetics. IgG from females stimulated more efficiently α-MSH-induced cyclic adenosine monophosphate production by melanocortin 4 receptor-expressing cells compared with IgG from males. DISCUSSION: Sex-related response to how E. coli affects feeding and anti-melanocortin hormone antibody production may depend on the presence of these bacteria in the gut before E. coli supplementation. These data suggest that sex-related presence of certain gut bacteria may represent a risk factor for ED development.

Melanin production through novel processing of proopiomelanocortin in the extracellular compartment of the auricular skin of C57BL/6 mice after UV-irradiation.

The production of melanin is regulated by α-melanocyte-stimulating hormone (α-MSH), which is produced from proopiomelanocortin (POMC). Keratinocytes release POMC along with lower levels of α-MSH and ACTH. To clarify the mechanism of melanogenesis after ultraviolet (UV)-irradiation, this study focused on the expression of POMC and POMC-derived peptides after UV-irradiation. Western blot analysis and immunoassays indicated that both POMC and α-MSH-like immunoreactivity (α-MSH-LI) increased after UV-irradiation. However, other POMC-derived products were very low. In hypophysectomized mice, α-MSH-LI increased to the same level as in control mice after UV-irradiation. Structural analysis revealed that the major α-MSH-LI product was ACTH(1-8). Furthermore, ACTH(1-8) competed with [(125)I]-α-MSH for receptor binding and increased melanin production via a melanocortin-1 receptor. These results suggested that melanin was produced through ACTH(1-8) after UV-irradiation. Trypsin-like enzymatic activity, which is responsible for POMC activation, increased after UV-irradiation and was identified as tryptase. In mast cell-deficient mice, which do not produce tryptase, α-MSH-LI levels were unchanged after UV-irradiation. The present study demonstrates the production of ACTH(1-8) from POMC by tryptase, which is a novel peptide-processing mechanism in the extracellular compartment of the skin.