Mechanisms of antiinflammatory action of the neuroimmunomodulatory peptide alpha-MSH

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.

Applications of Melanin and Melanin-Like Nanoparticles in Cancer Therapy: A Review of Recent Advances

Thanks to the growing knowledge about cancers and their interactions with the immune system, a huge number of therapeutic cancer vaccines have been developed in the past two decades. Despite encouraging results in pre-clinical models, cancer vaccines have not yet achieved significant clinical efficacy. Several factors may contribute to such poor results, including the difficulty of triggering a strong immune response and the immunosuppressive tumor microenvironment. Many strategies are currently being explored. Different types of adjuvants have been incorporated into vaccine formulations to improve their efficacy, as cancer antigens are usually poorly immunogenic. Nanoparticle systems are promising tools as they act as carriers for antigens and can be surface-modified so that they specifically target antigen-presenting cells in lymph nodes. Bioinspired nanomaterials are ideal candidates thanks to their biocompatibility. Recently, melanin-based nanoparticles were reported to efficiently localize into draining lymphoid tissues and trigger immune responses against loaded antigens. In addition, by virtue of their photochemical properties, melanin-based nanoparticles can also play an immunomodulatory role to promote anti-cancer responses in the context of photothermal therapy. In this review, we discuss the above-mentioned properties of melanin, and summarize the promising results of the melanin-based cancer vaccines recently reported in preclinical models.

Melanocortins, Melanocortin Receptors and Multiple Sclerosis

The melanocortins and their receptors have been extensively investigated for their roles in the hypothalamo-pituitary-adrenal axis, but to a lesser extent in immune cells and in the nervous system outside the hypothalamic axis. This review discusses corticosteroid dependent and independent effects of melanocortins on the peripheral immune system, central nervous system (CNS) effects mediated through neuronal regulation of immune system function, and direct effects on endogenous cells in the CNS. We have focused on the expression and function of melanocortin receptors in oligodendroglia (OL), the myelin producing cells of the CNS, with the goal of identifying new therapeutic approaches to decrease CNS damage in multiple sclerosis as well as to promote repair. It is clear that melanocortin signaling through their receptors in the CNS has potential for neuroprotection and repair in diseases like MS. Effects of melanocortins on the immune system by direct effects on the circulating cells (lymphocytes and monocytes) and by signaling through CNS cells in regions lacking a mature blood brain barrier are clear. However, additional studies are needed to develop highly effective MCR targeted therapies that directly affect endogenous cells of the CNS, particularly OL, their progenitors and neurons.

Nerve-derived transmitters including peptides influence cutaneous immunology

Clinical observations suggest that the nervous and immune systems are closely related. For example, inflammatory skin disorders; such as psoriasis, atopic dermatitis, rosacea and acne; are widely believed to be exacerbated by stress. A growing body of research now suggests that neuropeptides and neurotransmitters serve as a link between these two systems. Neuropeptides and neurotransmitters are released by nerves innervating the skin to influence important actors of the immune system, such as Langerhans cells and mast cells, which are located within close anatomic proximity. Catecholamines and other sympathetic transmitters that are released in response to activation of the sympathetic nervous system are also able to reach the skin and affect immune cells. Neuropeptides appear to direct the outcome of Langerhans cell antigen presentation with regard to the subtypes of Th cells generated and neuropeptides induce the degranulation of mast cells, among other effects. Additionally, endothelial cells, which release many inflammatory mediators and express cell surface molecules that allow leukocytes to exit the bloodstream, appear to be regulated by certain neuropeptides and transmitters. This review focuses on the evidence that products of nerves have important regulatory activities on antigen presentation, mast cell function and endothelial cell biology. These activities are highly likely to have clinical and therapeutic relevance.

Identification of a physiological role for leptin in the regulation of ambulatory activity and wheel running in mice

Mechanisms regulating spontaneous physical activity remain poorly characterized despite evidence of influential genetic and acquired factors. We evaluated ambulatory activity and wheel running in leptin-deficient ob/ob mice and in wild-type mice rendered hypoleptinemic by fasting in both the presence and absence of subcutaneous leptin administration. In ob/ob mice, leptin treatment to plasma levels characteristic of wild-type mice acutely increased both ambulatory activity (by 4,000 ± 200 beam breaks/dark cycle, P < 0.05) and total energy expenditure (TEE; by 0.11 ± 0.01 kcal/h during the dark cycle, P < 0.05) in a dose-dependent manner and acutely increased wheel running (+350%, P < 0.05). Fasting potently increased ambulatory activity and wheel running in wild-type mice (AA: +25%, P < 0.05; wheel running: +80%, P < 0.05), and the effect of fasting was more pronounced in ob/ob mice (AA: +400%, P < 0.05; wheel running: +1,600%, P < 0.05). However, unlike what occurred in ad libitum-fed ob/ob mice, physiological leptin replacement attenuated or prevented fasting-induced increases of ambulatory activity and wheel running in both wild-type and ob/ob mice. Thus, plasma leptin is a physiological regulator of spontaneous physical activity, but the nature of leptin's effect on activity is dependent on food availability.

Textures in magnetic resonance images of the ischemic rat brain treated with an anti-inflammatory agent

Computer-based analysis of textures in magnetic resonance images provides a higher sensitivity to textural changes that cannot be recognized by the naked human eye. Thus, there is a better potential for identifying pathophysiological processes at an earlier stage or of a different character than even a trained radiologist can find. In the present study, the potential of texture analysis for in vivo identification of the administering effect of an anti-inflammatory drug in cerebral stroke in rats was evaluated. Twenty-seven Wistar rats underwent middle cerebral artery occlusion resulting in local ischemic brain infarct. One group of rats received alpha-melanocyte stimulating hormone (alpha-MSH) and a control group received saline only. T2-weighted images, apparent diffusion maps, and T2 maps were recorded by MR. Texture features were calculated in the T2-weighted images and correlated to the apparent diffusion coefficient (ADC) and the T2 values. From an array of tested texture features three independent features were tested further. Two of which were found to provide a significant discriminative classification between the control and the alpha-MSH groups. Furthermore, the same two texture features were significantly correlated to the ADCs. Thus, quantification of texture features can be helpful in detecting the effects of stroke therapy.

A distinct pattern of intracellular glucocorticoid-related responses is associated with extreme behavioral response to stress in an animal model of post-traumatic stress disorder

BACKGROUND

Activation of glucocorticoid receptors (GR) increases expression of the mitogen-activated protein kinase (MAPK) pathway leading to increased expression of Zif/268, an effector immediate early gene involved in cellular growth, intracellular signaling, and synaptic modification. Glucocorticoids induce expression of Zif/268 through two distinct mechanisms: a rapid-onset, MAPK-independent pathway and a slower-onset, MAPK-dependent mechanism.

METHOD

This study investigated both rapid and long-term expression of GR protein in the cytosolic extract, its translocation to the nucleus, and expression of mRNA for the Zif/268 gene in selected brain areas, associated with circulating levels of corticosterone, in an animal model of PTSD. Trauma cue-triggered Zif/268 expression was assessed eight days after stress exposure.

RESULTS

The results demonstrated a pattern of response that was common to all exposed individuals at 30 min after exposure, characterized by a significant elevation in GR translocation to the nucleus and elevated levels of Zif/268 mRNA in the hippocampus. A distinct pattern associated with extreme behavioral response (EBR) was revealed upon further bioassay of behavioral response groups, classified according to their individual patterns of behavioral response at seven days. These EBR individuals displayed significantly higher circulating corticosterone and nuclear GR levels, compared to minimal behavioral responders and controls. No difference in Zif/268 mRNA levels was observed between the exposed and naïve animals.

CONCLUSION

Following the uniform acute response, the patterns of GR protein levels and Zif/268 mRNA levels are associated with degree of behavioral disruption. Since the slower-onset mechanism for glucocorticoid-induced Zif/268 expression depends on activation of the MAPK pathway, the pattern observed only in EBR rats may be related to disruptions of this pathway.

Reduction of ischemic stroke in rat brain by alpha melanocyte stimulating hormone

Anti-inflammatory therapy has provided hope for a new effective treatment of brain ischemic stroke. In this study, adult male Wistar rats subjected to right middle cerebral artery occlusion (MCAO) for 60 min were allocated to treatment of the anti-inflammatory compound alpha melanocyte stimulating hormone (alpha-MSH) or saline. Magnetic resonance imaging (MRI) and histology were used to evaluate the effects of alpha-MSH. MRI volumetry was performed to measure infarct size, and MRI measurements of the apparent diffusion coefficient (ADC) were performed to evaluate changes in the extra/intracellular volume ratio. Triphenyltetrazolium chloride (TTC) staining was used as a reference method to measure infarct sizes. The ADC value of the infarct area decreased significantly two days after MCAO in both groups. Simultaneously the infarct volume determined from the ADC map decreased in the alpha-MSH treated group compared to the control group. Five days after MCAO, ADC returned to baseline levels in both groups. The infarct volume in the alpha-MSH group was smaller compared to the saline treated group as demonstrated both by MRI and TTC staining. This study showed that the extra/intracellular ratio (reflected by ADC) following focal brain ischemic stroke could be affected by alpha-MSH. Secondly, we showed that the infarct volume was reduced by alpha-MSH. The volumetric dimensions of the infarct areas measured by MRI were comparable to those measured by histology.

Design and microwave-assisted synthesis of novel macrocyclic peptides active at melanocortin receptors: discovery of potent and selective hMC5R receptor antagonists

Differentiation of the physiological role of the melanocortin receptor 5 MC5R from that of other melanocortin receptors will require development of high affinity and selective antagonists. To date, a few synthetic antagonist ligands active at hMC5 receptor are available, but most do not have appreciable selectivity. With the aim to gain more potent and selective antagonists for the MC5R ligands, we have designed, synthesized, and pharmacologically characterized a series of alkylthioaryl-bridged macrocyclic peptide analogues derived from MT-II and SHU9119. These 20-membered macrocycles were synthesized by a tandem combination using solid phase peptide synthesis and microwave-assisted reactions. Biological assays for binding affinities and adenylate cyclase activities for the hMC1R, hMC3R, hMC4R, and hMC5R showed that three analogues, compounds, 9, 4, and 7, are selective antagonists at the hMC5 receptor. In particular, compound 9(PG-20N) is a selective and competitive hMC5R antagonist, with IC 50 of 130 +/- 11 nM, and a pA 2 value of 8.3, and represents an important tool for further biological investigations of the hMC5R. Compounds 4 and 7 (PG14N, PG17N) show potent and selective allosteric inhibition at hMC5R with IC 50 values of 38 +/- 3 nM and 58 +/- 6 nM, respectively. Compound 9 will be used to further investigate and more clearly understand the physiological roles played by the MC5 receptor in humans and other animals.

Melanocortin-derived tripeptide KPV has anti-inflammatory potential in murine models of inflammatory bowel disease

BACKGROUND

Despite some progress in recent years, the options for treating inflammatory bowel disease (IBD) are still dissatisfying, and surgery rates are still high. The anti-inflammatory effects of melanocortin peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) have been described recently in, for example, dextran sodium sulfate (DSS) colitis in mice. The aim of this study was to investigate the therapeutic potential of the melanocortin-derived tripeptide alpha-MSH(11-13) (KPV) and its mode of action in 2 models of intestinal inflammation.

METHODS

The anti-inflammatory activity of KPV was analyzed in 2 well-described models of IBD: DSS colitis, and CD45RB(hi) transfer colitis. Furthermore, animals expressing a nonfunctional melanocortin-1 receptor (MC1Re/e) received DSS for induction of colitis and were treated with KPV. The course of inflammation was monitored by weight loss and histological changes in the colon as well as by myeloperoxidase (MPO) activity.

RESULTS

In the DSS-colitis model, treatment with KPV led to earlier recovery and significantly stronger regain of body weight. Histologically, inflammatory infiltrates were significantly reduced in KPV-treated mice, which was confirmed by the significant reduction of MPO activity in colonic tissue after KPV treatment. Supporting these findings, KPV treatment of transfer colitis led to recovery, regain of body weight, and reduced inflammatory changes histologically. In MC1Re/e mice, KPV treatment rescued all animals in the treatment group from death during DSS colitis.

CONCLUSIONS

The melanocortin-derived tripeptide KPV showed significant anti-inflammatory effects in 2 murine models of colitis. These effects seem to be at least partially independent of MC1R signaling. In conclusion, our data suggest KPV as an interesting therapeutic option for the treatment of IBD.

Signals generating anorexia during acute illness

Anorexia is part of the body's acute-phase response to illness. Microbial products such as lipopolysaccharides (LPS), which are also commonly used to model acute illness, trigger the acute-phase response and cause anorexia mainly through pro-inflammatory cytokines. LPS stimulate cytokine production through the cell-surface structural molecule CD14 and toll-like receptor-4. Cytokines ultimately change neural activity in brain areas controlling food intake and energy balance. The blood-brain barrier endothelial cells (BBB EC) are an important site of cytokine action in this context. BBB EC and perivascular cells (microglia and macrophages) form a complex regulatory interface that modulates neuronal activity by the release of messengers (e.g. PG, NO) in response to peripheral challenges. Serotonergic neurons originating in the raphe nuclei and glucagon-like peptide-1-expressing neurons in the hindbrain may be among the targets of these messengers, because serotonin (5-HT), acting through the 5-HT2C receptor, and glucagon-like peptide-1 have recently emerged as neurochemical mediators of LPS anorexia. The central melanocortin system, which is a downstream target of serotonergic neurons, also appears to be involved in mediation of LPS anorexia. Interestingly, LPS also reduce orexin expression and the activity of orexin neurons in the lateral hypothalamic area of fasted mice. As the eating-stimulatory properties of orexin are apparently related to arousal, the inhibitory effect of LPS on orexin neurons might be involved in LPS-induced inactivity and anorexia. In summary, the immune signalling pathways of LPS-induced, and presumably acute illness-induced, anorexia converge on central neural signalling systems that control food intake and energy balance in healthy individuals.

Induction of interleukin-1beta by interleukin-4 in lipopolysaccharide-treated mixed glial cultures: microglial-dependent effects

Glial-secreted proinflammatory mediators are dynamically involved in central nervous system responses to exogenous stimuli such as infection, neurotoxins, and nerve injury. The therapeutic use of anti-inflammatory agents may reduce certain central nervous system pathology induced by inflammatory responses. We investigated the role of interleukin (IL)-4 in modulating the production of proinflammatory mediators from lipopolysaccharide-stimulated mixed glia in vitro. Interestingly, IL-4 significantly enhanced IL-1beta secretion and did not affect monocyte chemoattractant protein-1 release, even though IL-4 considerably inhibited IL-6, tumor necrosis factor alpha, and nitric oxide production from rat neonatal mixed glia. Further, IL-4 exhibited inhibitory effects on IL-1beta production in microglial-enriched cultures, while significantly increasing IL-1beta production in microglial-depleted glia. The enhancing effect of IL-4 on IL-1beta production was found to be inversely correlated with the percentage of microglia present in the mixed glial population. In summary, IL-4 did not act as a global anti-inflammatory cytokine and in fact, under certain situations enhanced IL-1beta secretion. We conclude that IL-4 exerts its anti-inflammatory effects in a limited and target-specific manner, which is delicately regulated by the cellular microenvironment. Therefore, precaution should be taken when clinically using IL-4 to treat diseases manifested by overt inflammatory responses.

Hypothalamic proopiomelanocortin (POMC) neurons have a cholinergic phenotype

Neuronal networks originating in the hypothalamic arcuate nucleus play fundamental roles in the control of energy balance. Neuropeptide Y (NPY)-producing neurons in the arcuate nucleus stimulate food intake, whereas arcuate nucleus neurons that release the proopiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone (alpha-MSH) potently reduce food intake. Relatively little attention has been focused on classical neurotransmitters in regulation of food intake. Here, we have investigated the potential presence of acetylcholine (ACh) in NPY- and POMC-containing neuronal populations of the arcuate nucleus. Antisera to proteins required for cholinergic neurotransmission, including choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (VAChT), were employed in double-labeling immunohistochemical experiments. In colchicine-treated rats, ChAT- and VAChT-immunopositive cell bodies were located in the ventral aspect of the arcuate nucleus. ChAT and VAChT immunoreactivities were demonstrated in alpha-MSH- and cocaine- and amphetamine-regulated transcript (CART)-containing cell bodies of the arcuate nucleus, whereas cell bodies containing NPY or agouti-related peptide (AGRP) were distinct from VAChT-immunoreactive neuronal perikarya. VAChT immunoreactivity was also present in a large number of alpha-MSH-containing nerve fiber varicosities throughout the central nervous system. In the commissural part of the nucleus tractus solitarius, no alpha-MSH-containing cell bodies were found to have ChAT or VAChT immunoreactivity. The presence of markers for cholinergic neurotransmission in a subpopulation of hypothalamic POMC/CART neurons suggests co-release of ACh with peptides derived from the POMC precursor and CART. The results indicate a role for ACh in control of energy balance, mediating the effects of peripheral hormones such as leptin and insulin.

Characterization of Mahogunin Ring Finger-1 expression in mice

Mutations in mouse Mahogunin Ring Finger-1 (Mgrn1) were first recognized for their effect on agouti-mediated pigment-type switching. Mgrn1 null mutants are completely black and develop spongiform degeneration of the brain. Mgrn1 hypomorphs have dark fur but do not develop neurodegeneration. We characterized a new Mgrn1 hypomorphic allele caused by a gene-trap insertion. Mice homozygous for this mutation are slightly darker than non-mutant animals. They show reduced overall expression of Mgrn1 and two of the four normal Mgrn1 isoforms are replaced by beta-GEO fusion proteins that differ from the normal proteins at their carboxy termini. To investigate the role of different Mgrn1 isoforms in pigment-type switching, we used quantitative relative reverse transcriptase polymerase chain reaction to examine their expression in the skin of Mgrn1 mutant and control mice. Most Mgrn1 mutants produce little or no normal Mgrn1 in the skin. Mgrn1 null mutant mice overexpressing isoform I or III, which are normally absent or weakly expressed in adult skin, had normal agouti-banded hairs. Our results indicate that reduced levels of MGRN1 cause the pigmentation phenotypes of Mgrn1 mutant mice and that there are no significant differences in the function of the four MGRN1 isoforms in pigment-type switching.

The MC4 receptor and control of appetite

Mutations in the human melanocortin (MC)4 receptor have been associated with obesity, which underscores the relevance of this receptor as a drug target to treat obesity. Infusion of MC4R agonists decreases food intake, whereas inhibition of MC receptor activity by infusion of an MC receptor antagonist or with the inverse agonist AgRP results in increased food intake. This review addresses the role of the MC system in different aspects of feeding behaviour. MC4R activity affects meal size and meal choice, but not meal frequency, and the type of diet affects the efficacy of MC4R agonists to reduce food intake. The central sites involved in the different aspects of feeding behaviour that are affected by MC4R signalling are being unravelled. The paraventricular nucleus plays an important role in food intake per se, whereas MC signalling in the lateral hypothalamus is associated with the response to a high fat diet. MC4R signalling in the brainstem has been shown to affect meal size. Further genetic, behavioural and brain-region specific studies need to clarify how the MC4R agonists affect feeding behaviour in order to determine which obese individuals would benefit most from treatment with these drugs. Application of MCR agonists in humans has already revealed side effects, such as penile erections, which may complicate introduction of these drugs in the treatment of obesity.

Effects of the COOH-terminal tripeptide alpha-MSH(11-13) on corneal epithelial wound healing: role of nitric oxide

It is known that alpha-melanocyte stimulating hormone (alpha-MSH) may exert anti-inflammatory effects and facilitate reparative processes in different tissues. The effective message sequence of alpha-MSH resides in the COOH-terminal tripeptide alpha-MSH(11-13). This study was undertaken to investigate the effects of topical administration of the COOH-terminal tripeptide sequence of alpha-MSH (alpha-MSH(11-13), KPV) on corneal epithelial wound healing in rabbits and the possible role of nitric oxide (NO) in these effects. The whole corneal epithelium was denuded in both eyes by mechanical abrasion. The area of the corneal epithelial defect was stained with fluorescein, photographed, and then measured before the treatment and every 12 h by a computerized software. The mean epithelial wound area and the mean percent of epithelial defect remaining at each follow-up control were compared between experimental groups. Rabbits were topically treated with KPV 1, 5 or 10 mg/ml (30 microl), two drops four times in a day, for 4 days, starting immediately after corneal abrasion, while control animals received topical phosphate-buffered saline as vehicle. In order to study the role of NO in corneal repair processes, the NO donor, sodium nitroprusside (SP, 10 mg/ml, 30 microl) was administered in both eyes, two drops four times in a day, for 4 days. The effects of KPV or SP were challenged by pre-treatment with the nitric oxide synthase inhibitor, N omega-nitro-L-arginine methyl ester (L-NAME, 10 mg/ml, 30 microl) 30 min prior to KPV or SP instillation. The mean percent epithelial defect remaining each time was significantly smaller in animals treated with KPV or SP in comparison to controls. Sixty hours later, eight out of eight (100%) corneas treated with KPV or SP were completely re-epithelized (P<0.05) while none of the corneas treated with placebo were re-epithelized. Pre-treatment with L-NAME inhibited the facilitating effect of KPV on corneal epithelial wound healing process and totally prevented the effect of SP. Rabbit corneal epithelial cells (RCE) in culture were exposed for 1, 6 and 24 h to different KPV concentrations (0.1, 1 and 10 microM) in medium containing 15% foetal bovine serum (FBS). Cell viability was stimulated by 1 and 10 microM concentrations of the substance. Thus, KPV may facilitate corneal epithelial wound healing in rabbits with a mechanism that may involve NO disposition in corneal tissue. However, it is not known whether this mechanism is likely to depend on a direct stimulating repairing activity shared by the entire molecule of alpha-MSH.

Sick building syndrome (SBS) and exposure to water-damaged buildings: time series study, clinical trial and mechanisms

Occupants of water-damaged buildings (WDBs) with evidence of microbial amplification often describe a syndrome involving multiple organ systems, commonly referred to as "sick building syndrome" (SBS), following chronic exposure to the indoor air. Studies have demonstrated that the indoor air of WDBs often contains a complex mixture of fungi, mycotoxins, bacteria, endotoxins, antigens, lipopolysaccharides, and biologically produced volatile compounds. A case-series study with medical assessments at five time points was conducted to characterize the syndrome after a double-blinded, placebo-controlled clinical trial conducted among a group of study participants investigated the efficacy of cholestyramine (CSM) therapy. The general hypothesis of the time series study was that chronic exposure to the indoor air of WDBs is associated with SBS. Consecutive clinical patients were screened for diagnosis of SBS using criteria of exposure potential, symptoms involving at least five organ systems, and the absence of confounding factors. Twenty-eight cases signed voluntary consent forms for participation in the time-series study and provided samples of microbial contaminants from water-damaged areas in the buildings they occupied. Twenty-six participants with a group-mean duration of illness of 11 months completed examinations at all five study time points. Thirteen of those participants also agreed to complete a double-blinded, placebo-controlled clinical trial. Data from Time Point 1 indicated a group-mean of 23 out of 37 symptoms evaluated; and visual contrast sensitivity (VCS), an indicator of neurological function, was abnormally low in all participants. Measurements of matrix metalloproteinase 9 (MMP9), leptin, alpha melanocyte stimulating hormone (MSH), vascular endothelial growth factor (VEGF), immunoglobulin E (IgE), and pulmonary function were abnormal in 22, 13, 25, 14, 1, and 7 participants, respectively. Following 2 weeks of CSM therapy to enhance toxin elimination rates, measurements at Time Point 2 indicated group-means of 4 symptoms with 65% improvement in VCS at mid-spatial frequency-both statistically significant improvements relative to Time Point 1. Moderate improvements were seen in MMP9, leptin, and VEGF serum levels. The improvements in health status were maintained at Time Point 3 following a 2-week period during which CSM therapy was suspended and the participants avoid re-exposure to the WDBs. Participants reoccupied the respective WDBs for 3 days without CSM therapy, and all participants reported relapse at Time Point 4. The group-mean number of symptoms increased from 4 at Time Point 2 to 15 and VCS at mid-spatial frequency declined by 42%, both statistically significant differences relative to Time Point 2. Statistically significant differences in the group-mean levels of MMP9 and leptin relative to Time Point 2 were also observed. CSM therapy was reinstated for 2 weeks prior to assessments at Time Point 5. Measurements at Time Point 5 indicated group-means of 3 symptoms and a 69% increase in VCS, both results statistically different from those at Time Points 1 and 4. Optically corrected Snellen Distance Equivalent visual acuity scores did not vary significantly over the course of the study. Group-mean levels of MMP9 and leptin showed statistically significant improvement at Time Point 5 relative to Time Points 1 and 4, and the proportion of participants with abnormal VEGF levels was significantly lower at Time Point 5 than at Time Point 1. The number of participants at Time Point 5 with abnormal levels of MMP9, leptin, VEGF, and pulmonary function were 10, 10, 9, and 7, respectively. The level of IgE was not re-measured because of the low incidence of abnormality at Time Point 1, and MSH was not re-measured because previously published data indicated a long time course for MSH improvement. The results from the time series study supported the general study hypothesis that exposure to the indoor air of WDBs is associated with SBS. High levels of MMP9 indicated that exposure to the complex mixture of substances in the indoor air of the WDBs triggered a pro-inflammatory cytokine response. A model describing modes of action along a pathway leading to biotoxin-associated illness is presented to organize current knowledge into testable hypotheses. The model links an inflammatory response with tissue hypoxia, as indicated by abnormal levels of VEGF, and disruption of the proopiomelanocortin pathway in the hypothalamus, as evidenced by abnormalities in leptin and MSH levels. Results from the clinical trial on CSM efficacy indicated highly significant improvement in group-mean number of symptoms and VCS scores relative to baseline in the 7 participants randomly assigned to receive 2 weeks of CSM therapy, but no improvement in the 6 participants assigned placebo therapy during that time interval. However, those 6 participants also showed a highly significant improvement in group-mean number of symptoms and VCS scores relative to baseline following a subsequent 2-week period of CSM therapy. Because the only known benefit of CSM therapy is to enhance the elimination rates of substances that accumulate in bile by preventing re-absorption during enterohepatic re-circulation, results from the clinical trial also supported the general study hypothesis that SBS is associated with exposure to WDBs because the only relevant function of CSM is to bind and remove toxigenic compounds. Only research that focuses on the signs, symptoms, and biochemical markers of patients with persistent illness following acute and/or chronic exposure to WDBs can further the development of the model describing modes of action in the biotoxin-associated pathway and guide the development of innovative and efficacious therapeutic interventions.

Blunted HPA axis response to stress influences susceptibility to posttraumatic stress response in rats

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with low levels of circulating cortisol, and recent studies suggest that cortisol administration may reduce PTSD symptoms. This study investigated the role of cortisol in the manifestation of anxiety- and fear-like symptoms in an animal model of PTSD.

METHOD

Magnitude of changes in prevalence of anxiety-like behaviors on the elevated plus-maze and nonhabituated exaggerated startle reaction were compared in three strains of rats exposed to predator stress, with and without prior corticosterone treatment. Extreme behavioral changes in both paradigms implied an extreme behavioral response (EBR), representing PTSD-like symptoms.

RESULTS

Lewis rats exhibited greater baseline anxiety-like behaviors and greater stress-induced increases in anxiety-like behaviors than Fischer F344 or Sprague-Dawley rats, with only minor corticosterone increases following stress. Prevalence of EBR was 50% among Lewis rats compared with 10% of Fischer F344 and 25% of Sprague-Dawley rats. Administering corticosterone 1 hour before stress exposure reduced the prevalence of EBR from 50% to 8% in the Lewis rats.

CONCLUSIONS

These results suggest that a blunted HPA response to stress may play a causal role in this model of PTSD and that this susceptibility may be prevented by administration of cortisol before stress exposure.

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.

Breaking or making immunological privilege in the central nervous system: the regulation of immunity by neuropeptides

Immune privilege in the central nervous system (CNS) is not maintained by immune ignorance of the CNS, but by CNS control over inflammatory processes. In this review we examine the role neuropeptides play in maintenance of immune privilege in the CNS. Vasoactive intestinal peptide, alpha-melanocyte-stimulating-hormone, neuropeptide Y, and somatostatin are members of an anti-inflammatory repertoire of immune modulators, while substance P acts to break immune privilege and promote inflammation in the CNS. Here we focus both on cellular responses to these neuropeptides and the role these peptides play in immune privilege as it relates to CNS autoimmunity.

alpha-MSH prevents impairment in renal function and dysregulation of AQPs and Na-K-ATPase in rats with bilateral ureteral obstruction

The purpose of this study was to evaluate the effects of the anti-inflammatory hormone alpha-melanocyte-stimulating hormone (alpha-MSH) treatment on renal function and expression of aquaporins (AQPs) and Na-K-ATPase in the kidney in response to 24 h of bilateral ureteral obstruction (BUO) or release of BUO (BUO-R). In rats with 24-h BUO, immunoblotting revealed that downregulation of AQP2 and AQP3 was attenuated (AQP2: 38 +/- 5 vs. 13 +/- 4%; AQP3: 44 +/- 3 vs. 19 +/- 4% of sham levels; P < 0.05), whereas downregulation of Na-K-ATPase was prevented by alpha-MSH treatment (Na-K-ATPase: 94 +/- 7 vs. 35 +/- 5% of sham levels; P < 0.05). Immunocytochemistry confirmed the changes in AQP1 and Na-K-ATPase expression. Renal tubular cell apoptosis was confirmed in BUO kidneys, and alpha-MSH treatment virtually completely abolished apoptosis. Furthermore, we measured glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), respectively. Forty-eight hours after BUO-R demonstrated that alpha-MSH treatment almost completely prevented the decrease in GFR (nontreated: 271 +/- 50; alpha-MSH: 706 +/- 85; sham: 841 +/- 105 microl x min(-1).100 g body wt(-1), P < 0.05) and ERPF (nontreated: 1,139 +/- 217; alpha-MSH: 2,598 +/- 129; sham: 2,633 +/- 457 microl x min(-1).100 g body wt(-1), P < 0.05). alpha-MSH treatment also partly prevented the downregulation of AQP1 and Na-K-ATPase expression in rats after BUO-R for 48 h. In conclusion, alpha-MSH treatment significantly prevents impairment in renal function and also prevents downregulation of AQP2, AQP3, and Na-K-ATPase during BUO or AQP1 and Na-K-ATPase after BUO-R, demonstrating a marked renoprotective effect of alpha-MSH treatment in conditions with urinary tract obstruction.

Accelerating sensory recovery after sciatic nerve crush: non-selective versus melanocortin MC4 receptor-selective peptides

Melanocortin receptor ligands accelerate functional recovery after peripheral nerve crush. It is not known which mechanism is involved or via which melanocortin receptor this effect occurs, albeit indirect evidence favours the melanocortin MC4 receptor. To test whether the melanocortin MC4 receptor is involved in the effects of melanocortins on functional recovery, we used melanocortin compounds that distinguish the melanocortin MC4 receptor from the melanocortin MC1, MC3 and MC5 receptors on basis of selectivity and agonist/antagonist profile. Activation and binding studies indicated that the previously described peptides JK1 (Ac-Nle-Gly-Lys-D-Phe-Arg-Trp-Gly-NH2) and [D-Tyr4]melanotan-II ([D-Tyr4]MTII. Ac-Nle-c[Asp-His-D-Tyr-Arg-Trp-Lys]NH2) are selective for the rat melanocortin MC4 receptor as compared to the rat melanocortin MC3 and MC5 receptors, but are also potent on the melanocortin MC1 receptor. Both peptides did not accelerate sensory recovery in rats with a sciatic nerve crush, whereas the non-selective melanocortin agonist melanotan-II (MTII, Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]NH2) was effective. The melanocortin MC3/MC4 receptor antagonist SHU9119 (Ac-Nle-c[Asp-His-D-Nal(2)-Arg-Trp-Lys]NH2) also enhanced sensory recovery. This effect was probably not due to interaction with the melanocortin MC4 receptor, since JK46 (Ac-Gly-Lys-His-D-Nal(2)-Arg-Trp-Gly-NH2), a selective melanocortin MC4 receptor antagonist, was ineffective. Taken together, these data suggest that melanocortins do not accelerate sensory recovery via interaction with the melanocortin MC4 receptor. From the known melanocortin receptors, only the involvement of the melanocortin MC5 receptor in acceleration of recovery could not be excluded.

What price support? Ventricular assist device induced systemic response

Use of ventricular support systems has been associated with myriad systemic complications. Engendered by the blood-biomaterial interface of a unique host/device relationship, these complications include diverse humoral dyscrasias that frequently culminate in episodes of bleeding, hemolysis and thrombogenicity, heightened susceptibility to inflammation and infection, and transient immunal compromise. Recent endeavor in biocompatibility research has served to illustrate the critical role played by cellular, humoral, and neurohormonal components in regulating cytokine expression and has provided insight into the complexities involved in such biomechanical juxtapositions. The following is intended as a review of current literature attempting to address the many aspects of this host/device interaction and their consequences for the supported patient.

Intrauterine infection/inflammation during pregnancy and offspring brain damages: possible mechanisms involved

Intrauterine infection is considered as one of the major maternal insults during pregnancy. Intrauterine infection during pregnancy could lead to brain damage of the developmental fetus and offspring. Effects on the fetal, newborn, and adult central nervous system (CNS) may include signs of neurological problems, developmental abnormalities and delays, and intellectual deficits. However, the mechanisms or pathophysiology that leads to permanent brain damage during development are complex and not fully understood. This damage may affect morphogenic and behavioral phenotypes of the developed offspring, and that mice brain damage could be mediated through a final common pathway, which includes over-stimulation of excitatory amino acid receptor, over-production of vascularization/angiogenesis, pro-inflammatory cytokines, neurotrophic factors and apoptotic-inducing factors.

Delayed Administration of ??-Melanocyte-Stimulating Hormone or Combined Therapy with Bay 11-7085 Protects Against Gut Ischemia???Reperfusion Injury

Gut ischemia-reperfusion (I/R) injury is a serious complication of shock. Previously we demonstrated that the administration of alpha-melanocyte-stimulating hormone (MSH) immediately before mesenteric I/R protected against postischemic gut injury. In this report, we tested the therapeutic efficacy of alpha-MSH on gut I/R (60 min ischemia, 6 h reperfusion) injury when given at different time points of reperfusion. Rats underwent sham surgery or were treated with saline or with alpha-MSH that was given 1, 2, or 4 h after superior mesenteric artery clamping. Vehicle-treated I/R rats exhibited severe mucosal injury and increased NF-kappaB DNA binding activity, myeloperoxidase (MPO) activity, and interleukin-6 and heme oxygenase-1 (HO-1) expression. In contrast, rats given alpha-MSH at 1 h of reperfusion, but not 2 h or 4 h, exhibited much less mucosal injury. Rats given alpha-MSH at 1 h or 2 h of reperfusion, but not 4 h, exhibited less MPO activity, NF-kappaB DNA binding activity, and interleukin-6 protein and even higher levels of heme oxygenase-1 than vehicle-treated rats. In addition, we found that combined use of alpha-MSH, a known inhibitor of IkappaBalpha tyrosine phosphorylation, with BAY 11-7085, an inhibitor of IkappaBalpha Ser 32,36 phosphorylation, abrogates gut MPO induction and tissue injury at early and late time points of reperfusion. Thus, alpha-MSH, an endogenous peptide with a favorable side-effect profile, is effective in treating experimental gut I/R injury when given early after the initial ischemia and may represent a candidate therapy for gut I/R in humans in whom recognition and treatment are often delayed.

Tumor necrosis factor alpha increases and alpha-melanocyte-stimulating hormone reduces uveal melanoma invasion through fibronectin

Iris melanomas are less likely to metastasize than posterior compartment melanomas. The anterior chamber of the eye is an immunosuppressed microenvironment where a wide range of immunosuppressive factors in aqueous humor contribute to the immune privilege. One such factor is alpha-melanocyte-stimulating hormone, a potent anti-inflammatory neuropeptide that exhibits efficacy in many studies of acute and chronic inflammation. The aim of this study was to investigate whether the different metastatic behavior of iris melanomas versus posterior compartment melanomas might be explained by the differing immunosuppressive/anti-inflammatory environments of these tumors in vivo. To investigate this hypothesis, we studied the effect of human aqueous and vitreous fluids, of the proinflammatory cytokine tumor necrosis factor alpha, and of the anti-inflammatory peptides alpha-melanocyte-stimulating hormone and melanocyte-stimulating hormone 11-13 (KP-D-V) on the invasion of three human uveal melanoma cell lines through human fibronectin. Fresh aqueous humor samples significantly decreased the invasion in two out of three uveal melanoma cell lines. In contrast, vitreous humor did not reduce invasion. Tumor necrosis factor alpha significantly increased the invasiveness of uveal melanoma cell lines by approximately 50%-80% over 20 h. Full-length alpha-melanocyte-stimulating hormone, at concentrations present in the aqueous humor (10-9 M), as well as melanocyte-stimulating hormone 11-13 (KP-D-V) reduced the invasion of cells through human fibronectin by 45%-50% and also protected uveal melanoma cells from the pro-invasive actions of tumor necrosis factor alpha. These data are consistent with inflammation playing a major role in affecting the metastatic ability of uveal melanomas. Thus, ocular microenvironments that differ in their immunosuppressive/anti-inflammatory properties may influence the invasiveness of developing tumors.

alpha-Melanocyte-stimulating hormone inhibits lipopolysaccharide-induced tumor necrosis factor-alpha production in leukocytes by modulating protein kinase A, p38 kinase, and nuclear factor kappa B signaling pathways

The neuropeptide alpha-melanocyte-stimulating hormone (alpha-MSH) inhibits inflammation by down-regulating the expression of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) in leukocytes via stimulation of alpha-MSH cell surface receptors. However, the signaling mechanism of alpha-MSH action has not yet been clearly elucidated. Here, we have investigated signaling pathways by which alpha-MSH inhibits lipopolysaccharide (LPS)-induced TNF-alpha production in leukocytes such as THP-1 cells. We focused on the possible roles of protein kinase A (PKA), p38 kinase, and nuclear factor kappa B (NF kappa B) signaling. In THP-1 cells, LPS is known to activate p38 kinase, which in turn activates NF kappa B to induce TNF-alpha production. We found that pretreatment of cells with alpha-MSH blocked LPS-induced p38 kinase and NF kappa B activation as well as TNF-alpha production. This response was proportional to alpha-MSH receptor expression levels, and addition of an alpha-MSH receptor antagonist abolished the inhibitory effects. In addition, alpha-MSH treatment activated PKA, and PKA inhibition abrogated the inhibitory effects of alpha-MSH on p38 kinase activation, NF kappa B activation, and TNF-alpha production. Taken together, our results indicate that stimulation of PKA by alpha-MSH causes inhibition of LPS-induced activation of p38 kinase and NF kappa B to block TNF-alpha production.

Dissection of the anti-inflammatory effect of the core and C-terminal (KPV) alpha-melanocyte-stimulating hormone peptides

In this study, we analyzed the anti-inflammatory effects of alpha-melanocyte stimulating hormone (MSH)11-13 (KPV) in comparison with other MSH peptides in a model of crystal-induced peritonitis. Systemic treatment of mice with KPV, alpha-MSH, the core melanocortin peptide His-Phe-Arg-Trp, and the melanocontin receptor 3/4 agonist Ac-Nle4-c[Asp5,d-Phe7,Lys10]NH2 ACTH4-10 (MTII) but not the selective MC1-R agonist H-Ser-Ser-Ile-Ile-Ser-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2 (MS05) resulted in a significant reduction in accumulation of polymorphonuclear leukocyte in the peritoneal cavity. The antimigratory effect of KPV was not blocked by the MC3/4-R antagonist Ac-Nle4-c[Asp5,d-2Nal7,Lys10]NH2 ACTH4-10 (SHU9119). In vitro, macrophage activation, determined as release of KC and interleukin (IL)-1beta was inhibited by alpha-MSH and MTII but not by KPV. Furthermore, macrophage activation by MTII led to an increase in cAMP accumulation, which was attenuated by SHU9119, whereas KPV failed to increase cAMP. The anti-inflammatory properties of KPV were also evident in IL-1beta-induced peritonitis inflammation and in mice with a nonfunctional MC1-R (recessive yellow e/e mice). In conclusion, these data highlight that the C-terminal MSH peptide KPV exhibits an anti-inflammatory effect that is clearly different from that of the core MSH peptides. KPV is unlikely to mediate its effects through melanocortin receptors but is more likely to act through inhibition of IL-1beta functions.

Effects of alpha-melanotropin C-terminal tripeptide analogues on macrophage NO production

The C-terminal tripeptide of melanocyte-stimulating hormone, MSH (11-13) (Lys-Pro-Val), possesses strong anti-inflammatory actions, which are mediated via mechanisms that are not fully understood. To shed more light into these mechanisms we have here synthesised and evaluated the activities of L- and D-Val substituted cyclic modifications of MSH (11-13) on nitric oxide (NO) in macrophage RAW 264.7 cells, as well as on binding to melanocortin receptors (MCRs) in B16-F1 and MCR expressing insect cells, and for effects on cAMP. MSH (11-13) and its analogues did neither bind to MCRs nor stimulate cAMP in RAW 264.7 and B16-F1 cells, except H-, which showed a tendency to increase cAMP at high (10-100 microM) concentrations. However, all investigated peptides dose dependently inhibited NO in LPS/IFN-gamma-stimulated RAW 264.7, cells with a structure activity relationship suggesting the existence of a distinct receptive site. This site appears to be distinct from the MCRs and not linked with cAMP.

Redundancy of a functional melanocortin 1 receptor in the anti-inflammatory actions of melanocortin peptides: studies in the recessive yellow (e/e) mouse suggest an important role for melanocortin 3 receptor

The issue of which melanocortin receptor (MC-R) is responsible for the anti-inflammatory effects of melanocortin peptides is still a matter of debate. Here we have addressed this aspect using a dual pharmacological and genetic approach, taking advantage of the recent characterization of more selective agonists/antagonists at MC1 and MC3-R as well as of the existence of a naturally defective MC1-R mouse strain, the recessive yellow (e/e) mouse. RT-PCR and ultrastructural analyses showed the presence of MC3-R mRNA and protein in peritoneal macrophages (M phi) collected from recessive yellow (e/e) mice and wild-type mice. This receptor was functional as Mphi incubation (30 min) with melanocortin peptides led to accumulation of cAMP, an effect abrogated by the MC3/4-R antagonist SHU9119, but not by the selective MC4-R antagonist HS024. In vitro M phi activation, determined as release of the CXC chemokine KC and IL-1 beta, was inhibited by the more selective MC3-R agonist gamma(2)-melanocyte stimulating hormone but not by the selective MC1-R agonist MS05. Systemic treatment of mice with a panel of melanocortin peptides inhibited IL-1 beta release and PMN accumulation elicited by urate crystals in the murine peritoneal cavity. MS05 failed to inhibit any of the inflammatory parameters either in wild-type or recessive yellow (e/e) mice. SHU9119 prevented the inhibitory actions of gamma(2)-melanocyte stimulating hormone both in vitro and in vivo while HS024 was inactive in vivo. In conclusion, agonism at MC3-R expressed on peritoneal M phi leads to inhibition of experimental nonimmune peritonitis in both wild-type and recessive yellow (e/e) mice.

Alpha-melanocyte stimulating hormone prevents lipopolysaccharide-induced vasculitis by down-regulating endothelial cell adhesion molecule expression

The neuroendocrine hormone alpha-melanocyte stimulating hormone (MSH) has profound antiinflammatory and immunomodulating properties. Here we have examined the possibility that alpha-MSH may interfere with the expression and function of cell adhesion molecules (CAMs) expressed by human dermal microvascular endothelial cells (HDMECs) in response to lipopolysaccharide (LPS) or TNFalpha in vitro and in vivo. In HDMEC, alpha-MSH (10(-8)/10(-12) M) profoundly reduced the mRNA and protein expression of E-selectin, vascular CAM (VCAM)-1, and intercellular CAM (ICAM)-1 induced by LPS or TNFalpha as determined by semiquantitative RT-PCR, ELISA, and fluorescence-activated cell sorter analysis. In addition, alpha-MSH significantly impaired the LPS-induced ICAM-1 and VCAM-1-mediated adhesion of lymphocytes to HDMEC monolayer in a functional adhesion assay. Likewise, alpha-MSH effectively inhibited the transcription factor nuclear factor-kappaB activation in HDMEC, which is required for CAM gene expression. Importantly in vivo, in murine LPS-induced cutaneous vasculitis (local Shwartzman reaction), a single ip injection of alpha-MSH significantly suppressed the deleterious vascular damage and hemorrhage by inhibiting the sustained expression of vascular E-selectin and VCAM-1. This persistent expression has been implicated in the dysregulation of diapedesis and activation of leukocytes, which subsequently leads to hemorrhagic vascular damage. Our findings indicate that alpha-MSH may have an important therapeutical potential for the treatment of vasculitis, sepsis, and inflammatory diseases.

Stress and the inflammatory response: a review of neurogenic inflammation

The subject of neuroinflammation is reviewed. In response to psychological stress or certain physical stressors, an inflammatory process may occur by release of neuropeptides, especially Substance P (SP), or other inflammatory mediators, from sensory nerves and the activation of mast cells or other inflammatory cells. Central neuropeptides, particularly corticosteroid releasing factor (CRF), and perhaps SP as well, initiate a systemic stress response by activation of neuroendocrinological pathways such as the sympathetic nervous system, hypothalamic pituitary axis, and the renin angiotensin system, with the release of the stress hormones (i.e., catecholamines, corticosteroids, growth hormone, glucagons, and renin). These, together with cytokines induced by stress, initiate the acute phase response (APR) and the induction of acute phase proteins, essential mediators of inflammation. Central nervous system norepinephrine may also induce the APR perhaps by macrophage activation and cytokine release. The increase in lipids with stress may also be a factor in macrophage activation, as may lipopolysaccharide which, I postulate, induces cytokines from hepatic Kupffer cells, subsequent to an enhanced absorption from the gastrointestinal tract during psychologic stress. The brain may initiate or inhibit the inflammatory process. The inflammatory response is contained within the psychological stress response which evolved later. Moreover, the same neuropeptides (i.e., CRF and possibly SP as well) mediate both stress and inflammation. Cytokines evoked by either a stress or inflammatory response may utilize similar somatosensory pathways to signal the brain. Other instances whereby stress may induce inflammatory changes are reviewed. I postulate that repeated episodes of acute or chronic psychogenic stress may produce chronic inflammatory changes which may result in atherosclerosis in the arteries or chronic inflammatory changes in other organs as well.

Structure-activity relationship and signal transduction of gamma-MSH peptides in GH3 cells: further evidence for a new melanocortin receptor

The structure-activity relationship and signal transduction properties of the pro-opiomelanocortin (POMC)-derived gamma-MSH peptides in the GH3 cell line was compared with that described for the known melanocortin receptors (MCRs). Single alanine replacements showed that, unlike the classical MCRs, the His(5)-Phe(6)-Arg(7)-Trp(8) sequence in gamma2-MSH is not a core sequence for activating the gamma-MSH receptor in GH3 cells, whereas Met(3) is essential. gamma2-MSH increased binding of [35S]GTPgammaS to membrane preparations of GH3 cells. Blockade of protein kinase A abolished the [Ca(2+)](i) responses to gamma3-MSH, and low nanomolar doses of gamma3-MSH increased intracellular cAMP levels, which could be blocked by pertussis toxin (PTX). We conclude that the putative novel gamma-MSH receptor in GH3 cells is a GPCR, but with structure-activity and signal transduction features different from those of the classical MCRs.

Alpha-melanocyte-stimulating hormone protects against mesenteric ischemia-reperfusion injury

Mesenteric ischemia-reperfusion (I/R) injury to the intestine is a common and often devastating clinical occurrence for which there are few therapeutic options. alpha-Melanocyte-stimulating hormone (alpha-MSH) is a tridecapeptide released by the pituitary gland and immunocompetent cells that exerts anti-inflammatory actions and abrogates postischemic injury to the kidneys and brainstem of rodents. To test the hypothesis that alpha-MSH would afford similar protection in the postischemic small intestine, we analyzed the effects of this peptide on intestinal transit, histology, myeloperoxidase activity, and nuclear factor-kappaB (NF-kappaB) activation after 45 min of superior mesenteric artery occlusion and <or=6 h of reperfusion. Rats subjected to I/R exhibited markedly depressed intestinal transit, histological evidence of severe injury to the ileum, increased myeloperoxidase activity in ileal cytoplasmic extracts, and biphasic activation of NF-kappaB in ileal nuclear extracts. In contrast, rats treated with alpha-MSH before I/R exhibited intestinal transit and histological injury scores comparable to those of sham-operated controls. In addition, the alpha-MSH-treated rats demonstrated less I/R-induced activation of intestinal NF-kappaB and myeloperoxidase activity after prolonged (6 h) reperfusion. We conclude that alpha-MSH significantly limits postischemic injury to the rat small intestine.

Long-term alterations in body weight do not affect the expression of melanocortin receptor-3 and -4 mRNA in the ovine hypothalamus

The pro-opiomelanocortin-derived peptides and the melanocortin receptors are implicated in various functions within the CNS including the regulation of food intake. In the present study, we used in situ hybridization, with specific 35S-labelled ovine riboprobes to map the expression of melanocortin receptor-3 (MC3-R) and -4 (MC4-R) mRNA in the diencephalon and brainstem of normal female sheep. Furthermore, we examined the effect of long-term alterations in energy balance on the distribution and expression of MC3-R and MC4-R mRNA in food-restricted and ad libitum-fed ovariectomized female sheep. The distribution of melanocortin receptors generally resembled that of the rat. A high number of MC3-R-labelled cells were seen in the ventral division of the lateral septum and the medial preoptic area. In the hypothalamus, a moderate number of MC3-R-labelled cells was observed in the lateral hypothalamic area while other nuclear groups had low to intermediate numbers of MC3-R-labelled cells. The distribution of MC4-R mRNA was generally similar to that of MC3-R mRNA in the septal/preoptic and hypothalamic regions, with a high number of labelled cells present in the intermediate division of the lateral septum. Within the hypothalamus, no MC4-R mRNA expression was observed in the arcuate nucleus. There was more widespread distribution of moderate to low numbers of MC4-R mRNA-expressing cells in the brainstem compared to that of MC3-R mRNA. Unlike findings in the rat, only a low number of cells expressed melanocortin receptor mRNA in the ovine hypothalamic nuclei associated with feeding behavior. The number of melanocortin receptor-labelled cells and the level of expression (silver grains/cell) in the hypothalamic feeding centers was similar in food-restricted and ad libitum-fed animals. These findings suggest that long-term alterations in metabolic status do not change the melanocortin receptor mRNA distribution and/or expression in the sheep hypothalamus.

Stress, inflammation and cardiovascular disease

Various psychosocial factors have been implicated in the etiology and pathogenesis of certain cardiovascular diseases such as atherosclerosis, now considered to be the result of a chronic inflammatory process. In this article, we review the evidence that repeated episodes of acute psychological stress, or chronic psychologic stress, may induce a chronic inflammatory process culminating in atherosclerosis. These inflammatory events, caused by stress, may account for the approximately 40% of atherosclerotic patients with no other known risk factors. Stress, by activating the sympathetic nervous system, the hypothalamic-pituitary axis, and the renin-angiotensin system, causes the release of various stress hormones such as catecholamines, corticosteroids, glucagon, growth hormone, and renin, and elevated levels of homocysteine, which induce a heightened state of cardiovascular activity, injured endothelium, and induction of adhesion molecules on endothelial cells to which recruited inflammatory cells adhere and translocate to the arterial wall. An acute phase response (APR), similar to that associated with inflammation, is also engendered, which is characterized by macrophage activation, the production of cytokines, other inflammatory mediators, acute phase proteins (APPs), and mast cell activation, all of which promote the inflammatory process. Stress also induces an atherosclerotic lipid profile with oxidation of lipids and, if chronic, a hypercoagulable state that may result in arterial thromboses. Shedding of adhesion molecules and the appearance of cytokines, and APPs in the blood are early indicators of a stress-induced APR, may appear in the blood of asymptomatic people, and be predictors of future cardiovascular disease. The inflammatory response is contained within the stress response, which evolved later and is adaptive in that an animal may be better able to react to an organism introduced during combat. The argument is made that humans reacting to stressors, which are not life-threatening but are "perceived" as such, mount similar stress/inflammatory responses in the arteries, and which, if repetitive or chronic, may culminate in atherosclerosis.

Calcitonin induces IL-6 production via both PKA and PKC pathways in the pituitary folliculo-stellate cell line

It has been demonstrated that calcitonin-binding sites are present in a variety of tissue types, including in the pituitary gland. Interleukin-6 (IL-6) is also produced in the pituitary and it regulates the secretion of various hormones. In this study, we examined the expression of the calcitonin receptor and the mechanism of IL-6 production induced by calcitonin in the pituitary folliculo-stellate cell line (TtT/GF). The mRNA of calcitonin receptor subtype C1a, but not that of C1b, was detected by RT-PCR in TtT/GF cells and in the normal mouse pituitary. Calcitonin increased cAMP accumulation and IL-6 production in a concentration-dependent manner in TtT/GF cells. As calcitonin activates the PKA and PKC pathways, we investigated the contributions of PKA and PKC to IL-6 production. IL-6 production was only slightly increased by either 8-bromo-cAMP (1 mM) or phorbol 12-myristate 13-acetate (100 nM) alone. However, IL-6 was synergistically induced in the presence of both 8-bromo-cAMP (1 mM) and phorbol 12myristate 13-acetate (100 nM). Furthermore, calcitonin-induced IL-6 production was completely suppressed by H-89 (PKA inhibitor) or GF109203X (PKC inhibitor), indicating that the activation of both PKA and PKC is necessary for calcitonin-induced IL-6 production. On the other hand, pertussis toxin (G(i)/G(o) signaling inhibitor) treatment achieved an approximately 9-fold increase in calcitonin-induced IL-6 production. These results show that calcitonin-stimulated IL-6 production is mediated via both PKA- and PKC-signaling pathways, whereas calcitonin also suppresses IL-6 production by activating G(i)/G(o) proteins in folliculo-stellate cells.

Anorexic but not pyrogenic actions of interleukin-1 are modulated by central melanocortin-3/4 receptors in the rat

The cytokine interleukin-1 (IL-1), which mediates many responses to infection and injury, induces anorexia and fever through direct actions in the central nervous system. The melanocortin neuropeptides, such as alpha melanocyte-stimulating hormone (alpha-MSH), reportedly antagonize many actions of IL-1, including fever and anorexia. However, it is unknown whether endogenous melanocortins modulate anorexia induced by IL-1. The objective of the present study was to establish the effect of endogenous melanocortins on IL-1-induced anorexia and fever in the rat. Intracerebroventricular (i.c.v.) injection of IL-1beta caused a significant reduction in food intake and body weight gain, and a rise in core body temperature in conscious rats. Coadministration of the melanocortin-3/4 receptor (MC3/4-R) antagonist, SHU9119, reversed IL-1beta-induced reductions in food intake and body weight, but did not affect the febrile response to IL-1beta. These data suggest IL-1beta may elicit its effects on food intake through the melanocortin system, predominantly via the MC3-R or MC4-R. In contrast, IL-1beta-induced fever does not appear to be mediated or modulated by MC3-R or MC4-R activity.

The role of alpha-MSH as a modulator of cutaneous inflammation

Among various neuropeptides such as substance P, calcitonin gene-related peptide and others, alpha-melanocyte-stimulating hormone (alpha-MSH) was found to be produced in the skin. Moreover, melanocortin receptor 1 (MC-1R), which is specific for alpha-MSH and ACTH, is expressed in the skin on keratinocytes, dendritic cells, macrophages and endothelial cells. In monocytes, macrophages and dendritic cells alpha-MSH inhibits the production and activity of immunoregulatory and proinflammatory cytokines such as IL-2, IFN-gamma, TNF-alpha and IL-1. It downregulates the expression of costimulatory molecules such as CD86 and CD40 and induces the production of suppressor factors such as the cytokine synthesis inhibitory factor IL-10. On endothelial cells alpha-MSH is capable of downregulating the LPS-induced expression of adhesion molecules such as vascular cell adhesion molecule (VCAM) and E-selectin. Moreover, the LPS-induced activation of transcription factors such as NF kappa B is downregulated by alpha-MSH. In a mouse model i.v. or topical application of alpha-MSH was found to inhibit the induction phase as well as the effector phase of contact hypersensitivity (CHS) reactions and to induce hapten-specific tolerance. These findings indicate that the production of immunosuppressing neuropeptides such as alpha-MSH by epidermal cells may play an essential role during the pathogenesis of immune and inflammatory reactions in the skin.

Effects of melanocortin peptides on lipopolysaccharide/interferon-gamma-induced NF-kappaB DNA binding and nitric oxide production in macrophage-like RAW 264.7 cells: evidence for dual mechanisms of action

The pro-opiomelanocortin-derived peptide alpha-melanocyte-stimulating hormone (alpha-MSH) mediates broad anti-inflammatory and immunomodulatory effects, which include inhibition of the production and release of proinflammatory cytokines and nitric oxide (NO) from macrophages. We investigated the effects of alpha-MSH, alpha-MSH(1-10), and alpha-MSH(11-13) on NO production and nuclear factor-kappaB (NF-kappaB) translocation in RAW 264.7 macrophages. After stimulation of the cells with bacterial lipopolysaccharide/interferon-gamma (LPS/IFN-gamma), all three peptides inhibited NO production with an order of potency alpha-MSH > or = alpha-MSH(11-13) > alpha-MSH(1-10). All three MSH peptides inhibited NF-kappaB nuclear translocation with the maximal effect of alpha-MSH and alpha-MSH(11-13) being seen in the range 1 nM-1 microM, and that of alpha-MSH(1-10) at 1 microM. By use of (125)I-(Nle(4),D-Phe(7))alpha-MSH(NDP-MSH) radioligand binding, MC(1) receptor-binding sites were demonstrated on RAW 264.7 cells. alpha-MSH and alpha-MSH(1-10) competed with the (125)I-NDP-MSH binding at these MC(1) receptor-binding sites, but alpha-MSH(11-13) even in concentrations up to 1 mM did not. Moreover, alpha-MSH and alpha-MSH(1-10) caused powerful stimulation of cyclic 3',5'-adenosine monophosphate (cAMP) in the RAW 264.7 cell, whereas alpha-MSH(11-13) was ineffective. Forskolin stimulated cAMP and inhibited NO production to the same extent as alpha-MSH and alpha-MSH(1-10), but did not modify the translocation of NF-kappaB. Whereas the protein kinase A inhibitor H89 did not modify the effect of alpha-MSH on NF-kappaB translocation, H89 caused a partial inhibition of the inhibitory effect of alpha-MSH, alpha-MSH(1-10), alpha-MSH(11-13), and forskolin on NO production. In addition alpha-MSH, alpha-MSH(1-10), alpha-MSH(11-13), and forskolin also inhibited the activity of an NF-kappaB-dependent luciferase reporter and these effects were partially counteracted by H89. We suggest that melanocortin peptides act via dual mechanisms of action: one cAMP-independent and causing inhibition of NF-kappaB translocation and the other dependent on MC(1) receptor/cAMP activation.

Stimulation of intracellular free calcium in GH3 cells by gamma3-melanocyte-stimulating hormone. Involvement of a novel melanocortin receptor?

The melanocortin (MC) gamma3MSH is a peptide that can be generated from the N-terminal domain of POMC and is believed to signal through the MC3 receptor. We recently showed that it induces a sustained rise in intracellular free calcium levels ([Ca(2+)](i)) in a subpopulation of pituitary cells, particularly in the lactosomatotroph lineage. In the present study we report that gamma3MSH and some analogs increase [Ca(2+)](i) in the GH- and PRL-secreting GH3 cell line and evaluate on the basis of pharmacological experiments and gene expression studies which MC receptor may be involved. A dose as low as 1 pM gamma3MSH induced an oscillating [Ca(2+)](i) increase in a significant percentage of GH3 cells. Increasing the dose recruited an increasing number of responding cells; a maximum was reached at 0.1 nM. gamma2MSH, alphaMSH, and NDP-alphaMSH displayed a similar effect. SHU9119, an MC3 and MC4 receptor antagonist, and an MC5 receptor agonist, did not affect the number of cells showing a [Ca(2+)](i) rise in response to gamma3MSH. SHU9119 had also no effect when added alone. MTII, a potent synthetic agonist of the MC3, MC4, and MC5 receptor as well as an N-terminally extended recombinant analog of gamma3MSH showed low potency in increasing [Ca(2+)](i) in GH3 cells, but high potency in stimulating cAMP accumulation in HEK 293 cells stably transfected with the MC3 receptor. In contrast, a peptide corresponding to the gamma2MSH sequence of POMC-A of Acipenser transmontanus increased [Ca(2+)](i) in GH3 cells, but was about 50 times less potent than gamma2- or gamma3MSH in stimulating cAMP accumulation in the MC3 receptor expressing HEK 293 cells. By means of RT-PCR performed on a RNA extract from GH3 cells, the messenger RNA of the MC2, MC3, and MC4 receptor was undetectable, but messenger RNA of the MC5 receptor was clearly present. These data suggest that the GH3 cell line does not mediate the effect of gamma3MSH through the MC3 receptor. The involvement of the MC5 receptor is unlikely, but cannot definitely be excluded. The findings animate the hypothesis that there exists a second, hitherto unidentified, MC receptor that displays high affinity for gamma3MSH.

NF-kappaB activation is inhibited in human pulmonary epithelial cells transfected with alpha-melanocyte-stimulating hormone vector

alpha-Melanocyte-stimulating hormone (alpha-MSH) modulates inflammation. We investigated the influence of alpha-MSH on NF-kappaB activation in human pulmonary epithelial cells (A549) using a plasmid vector encoding alpha-MSH (pCMV-ssMSH). Electrophoretic mobility shift assays demonstrated that NF-kappaB activation induced by lipopolysaccharide was inhibited in A549 cells transfected with pCMV-ssMSH. Western blot analysis revealed that this inhibition was linked to preservation of expression of IkappaBalpha protein. Chloramphenicol acetyltransferase assay indicated that NF-kappaB-dependent reporter gene expression was suppressed in A549 cells transfected with pCMV-ssMSH. The findings indicate that anti-inflammatory actions are exerted via modulation of NF-kappaB activation by preservation of IkappaBalpha protein in human pulmonary epithelial cells transfected with alpha-MSH vector. We showed a possibility of gene therapy for chronic inflammatory lung diseases.

Anorexia of infection: current prospects

The anorexia of infection is part of the host's acute phase response (APR). Despite being beneficial in the beginning, long lasting anorexia delays recovery and is ultimately deleterious. Microbial products such as bacterial cell wall compounds (e.g., lipopolysaccharides and peptidoglycans), microbial nucleic acids (e. g., bacterial DNA and viral double-stranded RNA), and viral glycoproteins trigger the APR and presumably also the anorexia during infections. Microbial products stimulate the production of proinflammatory cytokines (e.g., interleukins [ILs], tumor necrosis factor-alpha, interferons), which serve as endogenous mediators. Several microbial products and cytokines reduce food intake after parenteral administration, suggesting a role of these substances in the anorexia during infection. Microbial products are mainly released and cytokines are produced in the periphery during most infections; they might inhibit feeding through neural and humoral pathways activated by their peripheral actions. Activation of peripheral afferents by locally produced cytokines is involved in several cytokine effects, but is not crucial for the anorectic effect of microbial products and IL-1beta. Cytokines increase leptin expression in the adipose tissue, and leptin may contribute to, but is also not essential for, the anorectic effects of microbial products and cytokines. In addition, a direct action of cytokines and microbial products on the central nervous system (CNS) is presumably involved in the anorexia during infection. Cytokines can reach CNS receptors through circumventricular organs and through active or passive transport mechanisms or they can act through receptors on endothelial cells of the brain vasculature and stimulate the release of subsequent mediators such as eicosanoids. De novo CNS cytokine synthesis occurs in response to peripheral infections, but its role in the accompanying anorexia is still open to discussion. Central mediators of the anorexia during infection appear to be neurochemicals involved in the normal control of feeding, such as serotonin, dopamine, histamine, corticotropin releasing factor, neuropeptide Y, and alpha-melanocyte-stimulating hormone. Reciprocal, synergistic, and antagonistic interactions between various pleiotropic cytokines, and between cytokines and neurochemicals, form a complex network that mediates the anorexia during infection. Current knowledge on the mechanisms involved suggests some therapeutic options for treatment. Substances that block common key steps in cytokine synthesis or cytokine action, or inhibitors of eicosanoid synthesis, may hold more promise than attempts to antagonize specific cytokines. To target the neurochemical mediation of the anorexia during infection may be even more efficient. Future research should address these neurochemical mechanisms and the cytokine actions at the blood-brain barrier. Further unanswered questions concern the modulation of the anorexia during infection by gender and nutritional state.

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.

Corticotropin releasing hormone and proopiomelanocortin involvement in the cutaneous response to stress

The skin is a known target organ for the proopiomelanocortin (POMC)-derived neuropeptides alpha-melanocyte stimulating hormone (alpha-MSH), beta-endorphin, and ACTH and also a source of these peptides. Skin expression levels of the POMC gene and POMC/corticotropin releasing hormone (CRH) peptides are not static but are determined by such factors as the physiological changes associated with hair cycle (highest in anagen phase), ultraviolet radiation (UVR) exposure, immune cytokine release, or the presence of cutaneous pathology. Among the cytokines, the proinflammatory interleukin-1 produces important upregulation of cutaneous levels of POMC mRNA, POMC peptides, and MSH receptors; UVR also stimulates expression of all the components of the CRH/POMC system including expression of the corresponding receptors. Molecular characterization of the cutaneous POMC gene shows mRNA forms similar to those found in the pituitary, which are expressed together with shorter variants. The receptors for POMC peptides expressed in the skin are functional and include MC1, MC5 and mu-opiate, although most predominant are those of the MC1 class recognizing MSH and ACTH. Receptors for CRH are also present in the skin. Because expression of, for example, the MC1 receptor is stimulated in a similar dose-dependent manner by UVR, cytokines, MSH peptides or melanin precursors, actions of the ligand peptides represent a stochastic (predictable) nonspecific response to environmental/endogenous stresses. The powerful effects of POMC peptides and probably CRH on the skin pigmentary, immune, and adnexal systems are consistent with stress-neutralizing activity addressed at maintaining skin integrity to restrict disruptions of internal homeostasis. Hence, cutaneous expression of the CRH/POMC system is highly organized, encoding mediators and receptors similar to the hypothalamic-pituitary-adrenal (HPA) axis. This CRH/POMC skin system appears to generate a function analogous to the HPA axis, that in the skin is expressed as a highly localized response which neutralizes noxious stimuli and attendant immune reactions.

alpha-MSH inhibits induction of C/EBPbeta-DNA binding activity and NOS2 gene transcription in macrophages

BACKGROUND

alpha-Melanocyte-stimulating hormone (alpha-MSH) is an endogenous tridecapeptide that exerts anti-inflammatory actions and abrogates postischemic renal injury in rodents. alpha-MSH inhibits lipopolysaccharide (LPS)-induced gene expression of several cytokines, chemokines, and nitric oxide synthase-2 (NOS2), but the molecular mechanisms underlying these effects have not been clearly defined. To test the hypothesis that alpha-MSH inhibits the expression of inducible trans-activating factors involved in NOS2 regulation, we used RAW 264.7 macrophage cells to examine the effects of alpha-MSH on the activation of nuclear factor-kappaB (NF-kappaB) and CCAAT/enhancer binding protein-beta (C/EBPbeta), trans-acting factors known to be involved in LPS + interferon (IFN)-gamma induction of the NOS2 gene.

METHODS

Gel shift assays were performed to identify NF-kappaB and C/EBP DNA binding activities in LPS + IFN-gamma-treated RAW 264.7 cells in the presence and absence of alpha-MSH. NOS2 promoter assays were conducted to identify the effects of alpha-MSH on LPS + IFN-gamma-mediated induction of NOS2 transcription.

RESULTS

Gel shift assays demonstrated LPS + IFN-gamma induction of NF-kappaB and C/EBP family protein-DNA complexes in nuclei harvested from the cells. Supershift assays revealed that the C/EBP complexes were comprised of C/EBPbeta, but not C/EBPalpha, C/EBPdelta, or C/EBPepsilon. alpha-MSH (100 nmol/L) inhibited the LPS + IFN-gamma-mediated induction of nuclear DNA binding activity of C/EBPbeta, but not that of NF-kappaB (in contrast to reports in other cell types), as well as the activity of a murine NOS2 promoter-luciferase construct. In contrast, alpha-MSH (100 nmol/L) had no effect on the induction of NOS2 promoter-luciferase genes harboring deletion or mutation of the C/EBP box.

CONCLUSIONS

These data indicate that alpha-MSH inhibits the induction of C/EBPbeta DNA binding activity and that this effect is a major mechanism by which alpha-MSH inhibits the transcription of the NOS2 gene. The inability of alpha-MSH to inhibit LPS + IFN-gamma induction of NF-kappaB in murine macrophage cells, which contrasts with inhibitory effects of the neuropeptide in other cell types, suggests that cell-type-specific mechanisms are involved.