Generation of expression constructs that secrete bioactive alphaMSH and their use in the treatment of experimental autoimmune encephalomyelitis

A nonbiodegradable scaffold-free cell sheet of genome-engineered mesenchymal stem cells inhibits development of acute kidney injury

Cell therapy using genome-engineered stem cells has emerged as a novel strategy for the treatment of kidney diseases. By exploiting genome editing technology, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) secreting an angiogenic factors or an anti-inflammatory factor were generated for therapeutic application in acute kidney injury. Junction polymerase chain reaction analysis verified zinc finger nucleases-assisted integration of the desired gene into the hUC-MSCs. Flow cytometry and differentiation assays indicated that genome editing did not affect the differentiation potential of these mesenchymal stem cells. Protein measurement in conditioned media with the use of ELISA and immunoblotting revealed the production and secretion of each integrated gene product. For cell therapy in the bilateral ischemia-reperfusion mouse model of acute kidney injury, our innovative scaffold-free cell sheets were established using a non-biodegradable temperature-responsive polymer. One of each type of scaffold-free cell sheets of either the angiogenic factor vascular endothelial grown factor or angiopoietin-1, or the anti-inflammatory factor erythropoietin, or α-melanocyte-stimulating hormone-secreting hUC-MSCs was applied to the decapsulated kidney surface. This resulted in significant amelioration of kidney dysfunction in the mice with acute kidney injury, effects that were superior to intravenous administration of the same genome-engineered hUC-MSCs. Thus, our scaffold-free cell sheets of genome-engineered mesenchymal stem cells provides therapeutic effects by inhibiting acute kidney injury via angiogenesis or anti-inflammation.

The COOH-Terminal Proline-Rich Region of GRP78 Is a Key Regulator of Its Cell Surface Expression and Viability of Tamoxifen-Resistant Breast Cancer Cells

Translocation of 78-kDa glucose-regulated protein (GRP78) from endoplasmic reticulum (ER) to plasma membrane represents a paradigm shift beyond its traditional function as an ER chaperone protein. Cell surface GRP78 (csGRP78) exerts novel signaling functions, and mechanisms underlying its cell surface expression are just emerging. Acquired tamoxifen resistance of breast cancer cells is accompanied with elevated level of csGRP78. Therefore, the tamoxifen-resistant MCF7 breast cancer cells (MCF7-LR) represents a clinically relevant model to study mechanisms of csGRP78 expression. We discovered that a proline-rich region (PRR) containing three consecutive prolines close to the COOH-terminus of GRP78 is important for its ability to form a complex with the partner protein, CD44v, as demonstrated by in vitro glutathione S-transferase pull-down assay. Proline to alanine mutations at the PRR compromised GRP78 expression level on the cell surface as evidenced by purification of biotinylated cell surface proteins. Reconstitution of MCF7-LR cells with the PRR mutant after knockdown of endogenous GRP78 diminished the capacity of GRP78 to stimulate STAT3 activation. The enforced expression of a short peptide bearing the PRR region of GRP78 led to reduction of CD44v and Cyclin D1 protein levels as well as cell viability, accompanied with increase in apoptotic signaling including cleaved Caspase-3 and PARP. These findings suggest that the COOH-terminal PRR of GRP78 is critical for its interaction with CD44v as well as its cell surface expression, and enforced expression of the short peptide bearing the PRR region may provide a new approach to lower the viability of tamoxifen-resistant breast cancer cells.

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.

TAT-HSA-α-MSH fusion protein with extended half-life inhibits tumor necrosis factor-α in brain inflammation of mice

Neuroinflammation constitutes a principal process involved in the progression of various central nervous system (CNS) disorders, including Parkinson's disease, Alzheimer's disease, ischemic stroke, and traumatic brain injury. The safety and efficacy of potential neuroprotective therapeutic agents is controversial and limited. Alpha-melanocyte-stimulating hormone (α-MSH) as a tridecapeptide derived from pro-opiomelanocortin displays potent anti-inflammatory and protective effects with a wide therapeutic window in brain damage. However, it is difficult to deliver effective concentrations of α-MSH into brain tissue via nondirect application. Besides, the half-life of the tridecapeptide is only a few minutes. In the present study, we generated a novel TAT-HSA-α-MSH by genetically fusing α-MSH with N-terminus 11-amino acid protein transduction domain of the human immunodeficiency virus Tat protein (TAT) and human serum albumin (HSA), which showed favorable pharmacokinetic properties and can effectively cross the blood brain barrier (BBB). The findings showed that TAT-HSA-α-MSH significantly inhibits NF-κB activation in human glioma cells A172 and tumor necrosis factor-α (TNF-α) production in experimental brain inflammation. These results indicate that TAT-HSA-α-MSH may be a potential therapeutic agent for treating neuroinflammation which plays a fundamental role in CNS disorders.

The Role of Alpha-MSH as a Modulator of Ocular Immunobiology Exemplifies Mechanistic Differences between Melanocortins and Steroids

Melanocortins are a highly conserved family of peptides and receptors that includes multiple proopiomelanocortin-derived peptides and five defined melanocortin receptors. The melanocortins have an important role in maintaining immune homeostasis and in suppressing inflammation. Within the healthy eye, the melanocortins have a central role in preventing inflammation and maintaining immune privilege. A central mediator of the anti-inflammatory activity is the non-steroidogenic melanocortin peptide alpha-melanocyte stimulating hormone. In this review we summarize the major findings of melanocortin regulation of ocular immunobiology with particular interest in the ability of melanocortin to induce immune tolerance and cytoprotection. The melanocortins have therapeutic potential because their mechanisms of action in regulating immunity are distinctly different from the actions of steroids.

SVα-MSH, a novel α-melanocyte stimulating hormone analog, ameliorates autoimmune encephalomyelitis through inhibiting autoreactive CD4(+) T cells activation

Alpha-melanocyte stimulating hormone (α-MSH) plays a crucial role in the regulation of immune and inflammatory reactions. Here we report that SVα-MSH, a novel α-MSH analog, could ameliorate the clinical severity of experimental autoimmune encephalomyelitis (EAE) in a preventive and therapeutic manner. SVα-MSH treatment induced the production of regulatory T (Treg) cells and reduced the Th17 cells in the CNS of EAE mice. SVα-MSH-treated PLP peptide 139-151-specific T cells showed a down-regulation of T cell activation markers CD69 and CD134. SVα-MSH did not induce apoptosis but blocked the G1/S phase transition, reduced the expression of cyclin E, Cdk2 and the activity of NFAT and AP-1 transcription factors. Thus, SVα-MSH acts as a novel immunotherapeutic approach in the treatment of autoimmune attack on the CNS.

Both MC5r and A2Ar are required for protective regulatory immunity in the spleen of post-experimental autoimmune uveitis in mice

The ocular microenvironment uses a poorly defined mela5 receptor (MC5r)-dependent pathway to recover immune tolerance following intraocular inflammation. This dependency is seen in experimental autoimmune uveoretinitis (EAU), a mouse model of endogenous human autoimmune uveitis, with the emergence of autoantigen-specific regulatory immunity in the spleen that protects the mice from recurrence of EAU. In this study, we found that the MC5r-dependent regulatory immunity increased CD11b(+)F4/80(+)Ly-6C(low)Ly-6G(+)CD39(+)CD73(+) APCs in the spleen of post-EAU mice. These MC5r-dependent APCs require adenosine 2A receptor expression on T cells to activate EAU-suppressing CD25(+)CD4(+)Foxp3(+) regulatory T cells. Therefore, in the recovery from autoimmune disease, the ocular microenvironment induces tolerance through a melanocortin-mediated expansion of Ly-6G(+) regulatory APCs in the spleen that use the adenosinergic pathway to promote activation of autoantigen-specific regulatory T cells.

Effect of NDP-α-MSH on PPAR-γ and -β expression and anti-inflammatory cytokine release in rat astrocytes and microglia

Brain inflammation plays a central role in numerous brain pathologies. Microglia and astrocytes are the main effector cells that become activated when an inflammatory process takes place within the central nervous system. α-melanocyte-stimulating hormone (α-MSH) is a neuropeptide with proven anti-inflammatory properties. It binds with highest affinity to the melanocortin receptor 4 (MC4R), which is present in astrocytes and upon activation triggers anti-inflammatory pathways. The aim of this research was to identify anti-inflammatory mediators that may participate in the immunomodulatory effects of melanocortins in glial cells. Since peroxisome proliferator-activated receptors (PPARs) have recently been implicated in the modulation of inflammation, we investigated the effect of an α-MSH analog, [Nle(4), D-Phe(7)]-α-MSH (NDP-α-MSH), on PPAR-β and PPAR-γ gene and protein expression in rat primary astrocytes and microglia. We initially demonstrated that rat primary microglia express MC4R and showed that treatment with NDP-α-MSH increases PPAR-γ protein levels and strongly decreases PPAR-β levels in both astrocytes and microglia. We also showed that extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated signaling is partially involved in these effects in a cell-specific fashion. Finally, we showed that NDP-α-MSH stimulates the release of the anti-inflammatory cytokines IL-10 and TGF-β from microglia and astrocytes, respectively. The presented data suggest a role for IL-10 and TGF-β in the protective action of melanocortins and a connection between MC4R pathway and that of the nuclear receptor PPAR-γ. This is the first report providing evidence that MC4R is expressed in rat primary microglia and that melanocortins modulate PPAR levels in glial cells. Our findings provide new insights into the mechanisms underlying the activation of glial MC4R and open perspectives for new therapeutic strategies for the treatment of inflammation-mediated brain diseases.

Gene transfer to chicks using lentiviral vectors administered via the embryonic chorioallantoic membrane

The lack of affordable techniques for gene transfer in birds has inhibited the advancement of molecular studies in avian species. Here we demonstrate a new approach for introducing genes into chicken somatic tissues by administration of a lentiviral vector, derived from the feline immunodeficiency virus (FIV), into the chorioallantoic membrane (CAM) of chick embryos on embryonic day 11. The FIV-derived vectors carried yellow fluorescent protein (YFP) or recombinant alpha-melanocyte-stimulating hormone (α-MSH) genes, driven by the cytomegalovirus (CMV) promoter. Transgene expression, detected in chicks 2 days after hatch by quantitative real-time PCR, was mostly observed in the liver and spleen. Lower expression levels were also detected in the brain, kidney, heart and breast muscle. Immunofluorescence and flow cytometry analyses confirmed transgene expression in chick tissues at the protein level, demonstrating a transduction efficiency of ∼0.46% of liver cells. Integration of the viral vector into the chicken genome was demonstrated using genomic repetitive (CR1)-PCR amplification. Viability and stability of the transduced cells was confirmed using terminal deoxynucleotidyl transferase (dUTP) nick end labeling (TUNEL) assay, immunostaining with anti-proliferating cell nuclear antigen (anti-PCNA), and detection of transgene expression 51 days post transduction. Our approach led to only 9% drop in hatching efficiency compared to non-injected embryos, and all of the hatched chicks expressed the transgenes. We suggest that the transduction efficiency of FIV vectors combined with the accessibility of the CAM vasculature as a delivery route comprise a new powerful and practical approach for gene delivery into somatic tissues of chickens. Most relevant is the efficient transduction of the liver, which specializes in the production and secretion of proteins, thereby providing an optimal target for prolonged study of secreted hormones and peptides.

Injection of an alpha-melanocyte stimulating hormone expression plasmid is effective in suppressing experimental autoimmune uveitis

PURPOSE

The neuropeptide, alpha-melanocyte stimulating hormone (alpha-MSH), is an endogenous antagonist of inflammation. Injections of alpha-MSH peptide into inflamed tissues have been found to be very effective in suppressing autoimmune and endotoxin mediated diseases. We evaluated the potential to suppress ocular autoimmune disease (uveitis) by augmenting the expression of alpha-MSH through subconjunctival injections of naked adrenocorticotropic hormone amino acids 1-17 (ACTH1-17) plasmid.

METHODS

We clinically scored the uveitis over time in B10.RIII, C57BL/6, and melanocortin 5 receptor knock-out (MC5r((-/-))) mice with experimental autoimmune uveitis (EAU) that were conjunctively injected with a naked DNA plasmid encoding ACTH1-17 at the time of EAU onset and three days later. The post-EAU retina histology of plasmid injected eyes was examined, and post-EAU concentrations of alpha-MSH in aqueous humor was assayed by ELISA.

RESULTS

The subconjunctival injection of ACTH1-17 plasmid augmented the concentration of alpha-MSH in the aqueous humor of all post-EAU mice. The injection of ACTH1-17 suppressed the severity of EAU in the B10.RIII and C57BL/6 mice but the MC5r((-/-)) mice. In all the models of EAU, the ACTH1-17 injection helped to preserve the structural integrity of the retina; however, post-EAU aqueous humor was not immunosuppressive.

CONCLUSIONS

The subconjunctival injection of the alpha-MSH expression vector ACTH1-17 plasmid is effective in suppressing EAU. The suppressive activity is dependent on MC5r expression, and possibly works though alpha-MSH antagonism of inflammation than on alpha-MSH directly modulating immune cells. The results suggest that an effective therapy for uveitis could include a gene therapy approach based on delivering alpha-MSH.

Role of alpha-melanocyte stimulating hormone and melanocortin 4 receptor in brain inflammation

Inflammatory processes contribute widely to the development of neurodegenerative diseases. The expression of many inflammatory mediators was found to be increased in central nervous system (CNS) disorders suggesting that these molecules are major contributors to neuronal damage. Melanocortins are neuropeptides that have been implicated in a wide range of physiological processes. The melanocortin alpha-melanocyte stimulating hormone (alpha-MSH) has pleiotropic functions and exerts potent anti-inflammatory actions by antagonizing the effects of pro-inflammatory cytokines and by decreasing important inflammatory mediators. Five subtypes of melanocortin receptors (MC1R-MC5R) have been identified. Of these, the MC4 receptor is expressed predominantly throughout the CNS. Evidence of effectiveness of selective MC4R agonists in modulating inflammatory processes and their low toxicity suggest that these molecules may be useful in the treatment of CNS disorders with an inflammatory component. This review describes the involvement of the MC4R in central anti-inflammatory effects of melanocortins and discusses the potential value of MC4R agonists for the treatment of inflammatory-related disorders.

The diminishment of experimental autoimmune encephalomyelitis (EAE) by neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) therapy

The neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) plays an important role in immune privilege by its suppression of inflammation, and its induction of regulatory T cells. This finding led us to test the possibility that we can use alpha-MSH to suppress autoimmune diseases, and promote re-establishment of immune tolerance to autoantigens. To test this possibility, SJL mice with experimental autoimmune encephalomyelitis (EAE) were injected with alpha-MSH at the first signs of paralysis. The alpha-MSH-treated mice in comparison with untreated EAE mice had a profound diminishment in the severity and tempo of EAE. The spleen cells in alpha-MSH-treated EAE produced TGF-beta in response to PLP-antigen stimulation in contrast to untreated mice spleen cells that produced IFN-gamma. When the alpha-MSH-treated EAE mice were reimmunized there was a delay of a week before the second episode of EAE. Although this delay maybe because of the induction of TGF-beta-producing spleen cells by the alpha-MSH-treatment, it was not adequate to suppress IFN-gamma-production by PLP-antigen stimulated spleen cells from untreated mice, nor able to suppress the eventual second episode of EAE. Therefore, the injection of alpha-MSH at the onset of paralysis is extremely effective in diminishing the severity and tempo of EAE, and the subsequent induction of potential PLP-specific Treg cells suggests that an alpha-MSH therapy could be attempted as part of a therapeutic regiment to impose immunoregulation and immunosuppression on an autoimmune disease of the central nervous system.

Prevention and treatment of experimental autoimmune encephalomyelitis with recombinant adeno-associated virus-mediated α-melanocyte-stimulating hormone-transduced PLP139-151-specific T cells

The aim of this study was to investigate the immunomodulatory effects and mechanism of action of alpha-melanocyte-stimulating hormone (alpha-MSH) gene modified proteolipid protein (PLP) 139-151-specific T cells (T(PLP-alpha-MSH)) in the SJL mouse model of experimental autoimmune encephalomyelitis (EAE). PLP139-151-specific T cells (T(PLP) cells) were transduced with a recombinant adeno-associated virus 2 (rAAV2) encoding alpha-MSH. After activation with PLP139-151 in vitro, T(PLP-alpha-MSH) cells secreted high levels of alpha-MSH and also demonstrated an altered Th1-like cytokine pattern as well as a high frequency of CD4(+)CD25(+)Treg cells. Transfer studies showed that T(PLP-alpha-MSH) cells could suppress the induction of adoptive transfer EAE. More importantly, our studies demonstrated that T(PLP-alpha-MSH) cells had preventive and therapeutic effect on active relapse-remitting EAE (REAE) in an antigen-inducible manner. Suppression of REAE by T(PLP-alpha-MSH) cells was associated with a general reduction of inflammatory central nervous system (CNS) infiltrates, a pronounced decrease in Th1 cytokines and chemokines expression and an increase in Th2 cytokines. These data strongly suggested that local delivery of alpha-MSH by rAAV2-mediated alpha-MSH-transduced PLP139-151-specific T cells (T(PLP-alpha-MSH)) would be a desirable new approach to the treatment of autoimmune disease in the CNS.

Alpha-melanocyte-stimulating hormone gene therapy reverses carbon tetrachloride induced liver fibrosis in mice

BACKGROUND

Hepatic fibrosis represents a process of healing and scarring in response to chronic liver injury. Effective therapies are lacking. We have previously demonstrated that alpha-melanocyte-stimulating hormone (alpha-MSH) gene therapy protects against thioacetamide-induced acute liver failure in mice. Recent reports showed that collagen metabolism is a novel target of alpha-MSH. Therefore, the aim of this study is to investigate whether alpha-MSH gene therapy possesses anti-hepatic fibrogenic effect in mice.

METHODS

Liver fibrosis was induced in mice by administering carbon tetrachloride (CCl4) continuously for 10 weeks. Alpha-MSH expression plasmid was delivered via electroporation after liver fibrosis had been established. Histopathology, reverse-transcription polymerase chain reaction (RT-PCR), immunoblotting, and gelatin zymography were used to investigate its possible mechanisms of action.

RESULTS

Alpha-MSH gene therapy reversed established liver fibrosis in CCl4-treated mice. RT-PCR revealed that alpha-MSH gene therapy attenuated the liver TGF-beta1, collagen alpha1, and cell adhesion molecule mRNA upregulation. Following gene transfer, both the activation of alpha-smooth muscle actin (alpha-SMA) and cyclooxygenase-2 (COX-2) was significantly attenuated. Further, alpha-MSH significantly increased matrix metalloproteinase (MMP) activity with tissue inhibitors of matrix metalloproteinase (TIMP) inactivation.

CONCLUSIONS

We have demonstrated that alpha-MSH gene therapy reversed established liver fibrosis in mice. It also prevented the upregulated fibrogenic and proinflammatory gene response after CCl4 administration. Its collagenolytic effect may be attributed to MMP and TIMP modulation. In summary, alpha-MSH gene therapy may be an effective therapeutic modality against liver fibrosis with potential clinical use.

Vitiligo patients present lower plasma levels of alpha-melanotropin immunoreactivities

Vitiligo is a depigmenting disorder characterized by the development of white patches with evidence in favour of an autoimmune mechanism. We investigated the role of melanotropins and the plasma levels of alpha-melanotropin and ACTH-like immunoreactivities in 40 vitiligo patients with the aim of detecting a possible influence of neuropeptide regulation of immunity. Twenty-one patients had active and 19 had stable vitiligo disease, 16 persons presented with an additional autoimmune thyroid disease. Median alpha-MSH levels in vitiligo patients were 6.4p mol/l [5.2;11.3] and significantly lower than in control persons with 11.4 pmol/l [8.6;13.4]. Median ACTH levels of the affected patient group were 17 pg/ml [10.5;28] and appeared statistically higher than 12 pg/ml [7;17] measured in the control group. Measured morning cortisol levels in both groups were not significantly different. Reduced cutaneous alpha-MSH immunoreactivities have been related to the development of autoimmune-induced depigmenting disorders. Our data present lower alpha-MSH plasma levels in vitiligo patients which may be associated with the development of vitiligo depigmentation and may indicate a condition of impaired peripheral tolerance in this autoimmune disorder.

Electroporative alpha-MSH gene transfer attenuates thioacetamide-induced murine hepatic fibrosis by MMP and TIMP modulation

Hepatic fibrosis represents a process of healing and scarring in response to chronic liver injury. alpha-Melanocyte-stimulating hormone (alpha-MSH) is a 13-amino-acid peptide with potent anti-inflammatory effects. We have previously demonstrated that alpha-MSH gene therapy protects against thioacetamide (TAA)-induced acute liver failure. Therefore, the aim of this study is to investigate whether alpha-MSH gene therapy possesses antihepatic fibrogenic effect. Liver fibrosis was induced by long-term TAA administration in mice. alpha-Melanocyte-stimulating hormone expression plasmid was delivered via electroporation after liver fibrosis was established. Our results showed that alpha-MSH gene therapy attenuated liver fibrosis in TAA-treated mice. Reverse transcription polymerase chain reaction revealed that alpha-MSH gene therapy attenuated the liver transforming growth factor-beta1, collagen alpha1 and cell adhesion molecule mRNA upregulation. Following gene transfer, the expression of alpha-smooth muscle actin and cyclooxygenase-2 were both significantly attenuated. Further, alpha-MSH significantly increased matrix metalloproteinase (MMP), while tissue inhibitors of matrix metalloproteinase (TIMPs) were inactivated. In summary, alpha-MSH gene therapy reversed established liver fibrosis in mice and prevented the upregulated fibrogenic and pro-inflammatory gene responses after TAA administration. Its collagenolytic effect might be attributed to MMP and TIMP modulation. Hence, alpha-MSH gene therapy may be an effective therapeutic modality against liver fibrosis with potential clinical use.

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.

Gene transfer of pro-opiomelanocortin prohormone suppressed the growth and metastasis of melanoma: involvement of alpha-melanocyte-stimulating hormone-mediated inhibition of the nuclear factor kappaB/cyclooxygenase-2 pathway

Pro-opiomelanocortin (POMC) is a prohormone of various neuropeptides, including corticotropin, alpha-melanocyte-stimulating hormone (alpha-MSH), and beta-endorphin (beta-EP). POMC neuropeptides are potent inflammation inhibitors and immunosuppressants and may exert opposite influences during tumorigenesis. However, the role of POMC expression in carcinogenesis remains elusive. We evaluated the antineoplastic potential of POMC gene delivery in a syngenic B16-F10 melanoma model. Adenovirus-mediated POMC gene delivery in B16-F10 cells increased the release of POMC neuropeptides in cultured media, which differentially regulated the secretion of pro- and anti-inflammatory cytokines in lymphocytes. POMC gene transfer significantly reduced the anchorage-independent growth of melanoma cells. Moreover, pre- or post-treatment with POMC gene delivery effectively retarded the melanoma growth in mice. Intravenous injection of POMC-transduced B16-F10 cells resulted in reduced foci formation in lung by 60 to 70% of control. The reduced metastasis of POMC-transduced B16-F10 cells could be attributed to their attenuated migratory and adhesive capabilities. POMC gene delivery reduced the cyclooxygenase-2 (COX-2) expression and prostaglandin (PG) E(2) synthesis in melanoma cells and tumor tissues. In addition, application of NS-398, a selective COX-2 inhibitor, mimicked the antineoplastic functions of POMC gene transfer in melanoma. The POMC-mediated COX-2 down-regulation was correlated with its inhibition of nuclear factor kappaB (NFkappaB) activities. Exogenous supply of alpha-MSH inhibited NFkappaB activities, whereas application of the alpha-MSH antagonist growth hormone-releasing peptide-6 (GHRP-6) abolished the POMC-induced inhibition of NFkappaB activities and melanoma growth in mice. In summary, POMC gene delivery suppresses melanoma via alpha-MSH-induced inhibition of NFkappaB/COX-2 pathway, thereby constituting a novel therapy for melanoma.

Gene polymorphisms and their effects in the melanocortin system

In addition to its role in human pigmentation, components of the melanocortin system regulate appetite, energy homeostasis and hormone production. Recent studies have suggested possible roles of this system in immunity, transmission of pain signals, and reproductive potential. A number of polymorphisms have been identified in genes of the melanocortin system and are associated with pigmentation in humans, as well as being causative of disorders of adrenal hormone production and obesity. This review gives an outline of these polymorphisms, their functional significance and possible application to or impact on diagnosis and pharmacotherapy based on melanocortin pathways.

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

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

Metabolic effects of transgenic melanocyte-stimulating hormone overexpression in lean and obese mice

The proopiomelanocortin-derived peptide, alpha-MSH, inhibits feeding via melanocortin receptors in the hypothalamus and genetic defects inactivating the melanocortin system have been shown to lead to obesity in experimental animals and humans. To determine whether long-term melanocortinergic activation has significant effects on body weight and composition and insulin sensitivity, transgenic mice overexpressing N-terminal proopiomelanocortin, including alpha- and gamma(3)-MSH, under the control of the cytomegalovirus-promoter were generated. The transgene was expressed in multiple tissues including the hypothalamus, in which both alpha-MSH and gamma(3)-MSH levels were increased approximately 2-fold, compared with wild-type controls. Transgene homozygous mice were also crossed with obese leptin receptor-deficient db(3J) and obese yellow A(y) mice. MSH overexpression led to uniform, dose- dependent darkening of coat color. MSH overexpression reduced weight gain and adiposity and improved glucose tolerance in lean male mice. In female transgenic mice, there was no significant effect on body weight, but there was a significant decrease in insulin levels. Obesity was attenuated in obese db(3J)/db(3J) male and female mice, but there was no improvement in glucose metabolism. In contrast, the MSH transgene improved glucose tolerance in male A(y) mice. These results support the hypothesis that long-term melanocortinergic activation could serve as a potential strategy for anti-obesity and/or antidiabetic therapy.

Do hyporesponsive genetic variants of the melanocortin 1 receptor contribute to the etiology of multiple sclerosis?

Hyporesponsive genetic variants of the melanocortin 1 receptor result in pigmentary phenotypes exhibiting light skin and light color hair, including red hair. These variants are common in populations with high rates of multiple sclerosis, while rare in populations with low rates. Alpha-melanocyte stimulating hormone, the major ligand for this receptor, is responsible for phenotype determination, but is also known for its anti-inflammatory and immune modulating effects, including inhibition of factors implicated in multiple sclerosis pathology. As the melanocortin 1 receptor is expressed on various cell types involved in immune response, it is possible that carriers of hyporesponsive variants of this receptor lack the full anti-inflammatory and immune modulating effects of alpha-melanocyte stimulating hormone. It is proposed that these variants are part of a spectrum of genes involved in the etiology of multiple sclerosis. Related aspects of multiple sclerosis epidemiology are examined.