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.     

Manipulating central nervous mechanisms of food intake and body weight regulation by intranasal administration of neuropeptides in man

Maintaining a stable body weight set-point is assumed to rely on a homeostatic central nervous system (CNS) regulation of body fat with the particular involvement of hypothalamic pathways. The peripheral adiposity signals insulin and leptin convey information on the amount of energy stored as body fat to the arcuate nucleus of the hypothalamus, where anabolic/orexigenic and catabolic/anorexigenic pathways interact to regulate food intake and energy expenditure. One of the most prominent orexigenic messengers is neuropeptide Y (NPY), whereas melanocortins, including alpha-melanocyte-stimulating hormone (alpha-MSH), are essential for inducing anorexigenic effects. The melanocortin receptor 4 (MC4-R) plays the most important role in mediating catabolic effects of alpha-MSH. In this review, we present a series of own studies on NPY, insulin and MSH/ACTH4-10, an MC4-R agonist. The studies were all based on the intranasal route of administration which enables a direct access of the peptides to hypothalamic functions. NPY acutely attenuated electrocortical signs of meal-related satiety. Prolonged intranasal administration of insulin as well as of MSH induced weight loss in healthy human subjects. However, overweight subjects did not lose body fat after MSH administration. The results corroborate in humans the significance of all three messengers for the central nervous regulation of adiposity and might contribute to the future development of medical strategies against body-weight-related disorders.     

Differential effects of alpha-, beta- and gamma(2)-melanocyte-stimulating hormones on hypothalamic neuronal activation and feeding in the fasted rat.

Hypothalamic pro-opiomelanocortin neurones have an established role in the control of feeding. While pro-opiomelanocortin is the precursor for at least three melanocortin peptides, alpha-, beta- and gamma-melanocyte-stimulating hormone (MSH), it has been widely assumed that alpha-MSH is the predominant ligand involved. We compared the effects of centrally administered alpha-, beta- and gamma(2)-MSH on hypothalamic neuronal activation and on food intake in rats fasted for 48 h. Significant reductions in food intake were seen with alpha-MSH (first hour) and gamma(2)-MSH (second hour) but not with beta-MSH. The pattern of neuronal activation, assessed by the detection of early growth response factor-1 protein, showed considerable overlap; all three melanocortins activated cells in the arcuate, ventromedial, paraventricular, periventricular and supraoptic nuclei, as well as the preoptic area. alpha-MSH and beta-MSH produced activation in the dorsomedial nuclei while gamma(2)-MSH was only weakly active here. Retrograde labelling by systemic Fluorogold injection revealed that many cells activated by MSH compounds in the arcuate, paraventricular, periventricular and supraoptic nuclei (but not dorsomedial or ventromedial) project outside the blood-brain barrier and are therefore likely to include neuroendocrine cells. Desacetyl-alpha-MSH, which has previously been reported to lack effects on feeding, produced no discernible neuronal activation in the hypothalamus.Our finding that both the pattern of neuronal activation and the distribution of neuroendocrine cells activated in response to these closely related peptides show only partial overlap suggests that, in addition to common pathways, there may exist distinct hypothalamic circuits activated by different pro-opiomelanocortin products. The slower time course of gamma(2)-MSH- versus alpha-MSH-induced suppression of feeding provides further support for the notion that the biological responses to individual melanocortin peptides may involve distinct neuronal mechanisms.     

Vitiligo – The story from within: A transmission electron microscopic study before and after narrow-band ultraviolet B

Melanocyte loss is the main feature of vitiligo, but evidence refers to pathological multiplayers. Transmission electron microscopy was utilized to further explore vitiligo before and after narrow-band ultraviolet B (NB-UVB) therapy. Skin biopsies were retrieved from lesional and perilesional skin and compared to normal control skin. Sections were examined for melanocytes and keratinocytes and the number of melanosomes and thickness of basal lamina were measured. In lesional skin, keratinocytes revealed two types of degeneration with a significant increase in the mean thickness of basal lamina and decrease in the number of melanosomes. After treatment, lesional and perilesional skin showed variable ultrastructural features.     

Pituitary adenylate cyclase-activating polypeptide directly modulates the activity of proopiomelanocortin neurons in the rat arcuate nucleus

Pituitary adenylate cyclase-activating polypeptide (PACAP) and the proopiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone (alpha-MSH) both regulate multiple neuroendocrine functions and feeding behavior. Two subtypes of PACAP receptor mRNAs, pituitary adenylate cyclase-activating polypeptide-specific receptor (PAC1-R) and pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide mutual receptor (VPAC2-R), are actively expressed in the arcuate nucleus of the hypothalamus, where POMC cell bodies are located. This observation led us to investigate the possible regulatory action of PACAP on rat POMC neurons. Double-labeling in situ hybridization histochemistry revealed that approximately 50% of POMC-producing neurons express PAC1-R and/or VPAC2-R mRNAs. The proportion of POMC neurons that also contain PAC1-R mRNA was homogeneous along the rostro-caudal axis of the arcuate nucleus while POMC-positive cell bodies expressing the VPAC2-R subtype were more abundant in the rostral region. Incubation of mediobasal hypothalamic explants with PACAP (10(-7) M; 30 min) increased POMC mRNA expression, and this effect was blocked by PACAP6-38 (10(-6) M). In contrast, incubation with vasoactive intestinal polypeptide (10(-7) M) did not affect POMC mRNA level. Incubation of hypothalamic fragments with PACAP (10(-7) M) caused a significant increase in alpha-MSH content in the tissue and in the incubation medium. Altogether, the present results reveal that exogenous PACAP, acting probably through PAC1-R, regulates the activity of POMC neurons in the rat hypothalamus. These data suggest that the effects of PACAP on the gonadotropin-releasing hormone neuroendocrine axis and the regulation of feeding behavior may be mediated, at least in part, through modulation of POMC neurons.     

Role of staphylococcal superantigen in atopic dermatitis: influence on keratinocytes

Staphylococcus aureus may perform an crucial function in atopic dermatitis (AD), via the secretion of superantigens, including staphylococcal enterotoxins (SE) A or B, and toxic shock syndrome toxin-1 (TSST-1). Dysregulated cytokine production by keratinocytes (KCs) upon exposure to staphylococcal superantigens (SsAgs) may be principally involved in the pathophysiology of AD. We hypothesized that lesional KCs from AD may react differently to SsAgs compared to nonlesional skin or normal skin from nonatopics. We conducted a comparison of HLA-DR or CD1a expression in lesional skin as opposed to that in nonlesional or normal skin by immunohistochemistry (IHC). We also compared, using ELISA, the levels of IL-1alpha, IL-1beta, and TNF-alpha secreted by cultured KCs from lesional, nonlesional, and normal skin, after the addition of SEA, SEB and TSST-1. IHC revealed that both HLA-DR and CD1a expression increased significantly in the epidermis of lesional skin versus nonlesional or normal skin in quite a similar manner. IL-1alpha, IL-1beta, and TNF-alpha secretion was also significantly elevated in the cultured KCs from lesional skin after the addition of SsAgs. Our results indicated that KCs from lesional skin appear to react differently to SsAgs and increased proinflammatory cytokine production in response to SsAgs may contribute to the pathogenesis of AD.     

alpha-Melanocyte stimulating hormone: production and degradation

Proopiomelanocortin (POMC) is a polypeptide hormone precursor that is expressed in the brain and in peripheral tissues such as in the pituitary gland, immune system, and skin. In the brain, POMC is processed to form several peptides including alpha-melanocyte stimulating hormone (α-MSH). alpha-MSH is expressed in the hypothalamic arcuate nucleus and in the nucleus tractus solitarius of the brainstem where it has a crucial role in the regulation of metabolic functions. Specifically, α-MSH is an anorexigenic peptide. Its production and maturation processes have been shown to be regulated according to the metabolic condition of the organism. This review summarizes our current knowledge on α-MSH processing including its maturation and degradation processes and pharmacological aspects of its manipulation.     

Staphylococcal exfoliative toxins cleave alpha- and beta-melanocyte-stimulating hormones

The staphylococcal exfoliative toxins (ETs) A and B (ETA and ETB) are 27-kDa exotoxins produced by certain strains of Staphylococcus aureus and are the causative agents of staphylococcal scalded-skin syndrome. The crystal structures of the ETs strongly indicate that the proteins are members of the serine protease family of enzymes, although protease activity until now has not yet been conclusively demonstrated. Here, we show that the peptide beta-melanocyte-stimulating hormone (beta-MSH) is cleaved by ETA and that both ETA and ETB are capable of cleaving alpha-MSH. Both toxins exhibit cleavage at specific glutamic acid residues in MSH peptides. Moreover, biologically inactive mutants of ETA were incapable of cleaving beta-MSH.     

Perforin Expression in Plaque Psoriasis: An Immunohistochemical Study

Psoriasis (PsO) is T-cell-mediated disease resulting from aberrant activation of both innate and adaptive immunity. Perforin is a multi-domain, pore-forming protein. It is located within the cytoplasm of CD 8 cytotoxic T cells (CTLs) and natural killer cells (NK). The aim of this study was to evaluate the immunohistochemical (IHC) expression of perforin in lesional and perilesional skin of chronic plaque psoriatic patient and correlate its expression with the standard clinico-pathological variables. This prospective case–control study was conducted on 50 PsO patients and 30 age- and gender-matched healthy subjects as a control group. There were high-significant differences between lesional and perilesional skin of plaque PsO patients as regards to IHC perforin status and localization (p?p?p?=?0.02 and 0.03, respectively). Localization of IHC perforin positive lymphocytes in both epidermis and dermis was significantly associated with higher degree of acanthosis and higher degree of inflammatory infiltrates in comparison with positive cells located in dermis (p?=?0.001 for both). Perforin might have a putative signaling in early and late plaque PsO. Plaque psoriatic patients with positive perforin expression could be a candidate for a future target therapy to stop the proposed scenario and achieve a therapeutic response.     

Expression of class II HLA antigens (HLA-DR, DQW1, DQW3) in normal skin and cutaneous pathology

We report the cutaneous expression of class II HLA antigens disclosed by immunohistochemical staining of normal and lesional skin with monoclonal antibodies (MoAbs) reacting with HLA-DR, DQW1 and DQW3 antigens. Briefly, we disclosed: on normal human skin: 1) The Langerhans cells (LC) HLA-DR+, DQW1+; 2) the acrosyringium HLA-DR+, DQW1+, DQW3+; 3) the dermal vessel endothelial cells HLA-DR+. On lesional skin: 1) The LC were found HLA-DQW3+ in the lesional skin of some cutaneous diseases; this expression was never shown on LC of normal human skin; 2) the epidermal keratinocytes disclosed an uniform membrane expression of HLA-DR antigens in some cutaneous diseases; this kind of expression was not found by immunostaining with MoAbs directed against HLA-DQ antigens; 3) in psoriatic lesions some keratinocytes disclosed an heterogeneous expression of HLA-DR, DQW1 and DQW3 antigens; 4) tumoral cells from cutaneous malignant melanomas were shown to be HLA-DR+, DQW1+, DQW3+. The HLA-DQW3 expression on the LC of lesional skin is in favour with a modulation of HLA-DQW3 expression by unknown factors present in pathological skin. The HLA-DR expression on epidermal keratinocytes suggests a functional collaboration of keratinocytes with LC in the genetic restriction of cutaneous immune reactions.     

Autocrine inhibitory influences of alpha-melanocyte-stimulating hormone in malignant pleural mesothelioma

Malignant pleural mesothelioma is a highly aggressive tumor arising from the mesothelial cells that line the pleural cavities. This tumor is resistant to most conventional anticancer treatments and appears to be very sensitive to growth-promoting influences of cytokines and growth factors. Identification of natural inhibitory pathways that control growth should aid discovery of novel therapeutic approaches. We hypothesized that alpha-melanocyte-stimulating hormone (alpha-MSH), which is produced by many cell types and antagonizes cytokines and growth factors, could be an endogenous inhibitory molecule in mesothelioma. Twelve mesothelioma cell lines were established from pleural effusions of patients with malignant mesothelioma. Mesothelioma cells were found to express mRNA for proopiomelanocortin and its processing enzymes; release alpha-MSH peptide into supernatants; and express melanocortin 1 receptor (MC1R), the high-affinity receptor for alpha-MSH. Immunoneutralization of MC1R in the cell lines enhanced expression of interleukin-8 (IL-8), IL-6, and transforming growth factor-beta. These molecules promote mesothelioma proliferation and are considered therapeutic targets in this tumor. Coincubation of mesothelioma cells with synthetic alpha-MSH significantly reduced cell proliferation. The present research shows an autocrine-inhibitory circuit based on alpha-MSH and its receptor MC1R. Activation of MC1R by selective peptides or peptidomimetics might provide a novel strategy to reduce mesothelioma cell proliferation by taking advantage of this endogenous inhibitory circuit.     

Plexin-B2 in psoriasis; a clinical and immunohistochemical study

ABSTRACT

Psoriasis is an inflammatory, immune-mediated disease. Plexins are transmembrane proteins that are involved in immune system regulation and inflammation. This work aimed to investigate the immunohistochemical expression of Plexin-B2 in plaque psoriasis in both lesional and perilesional skin. This case‐control study included 30 patients with psoriasis vulgaris in comparison with 20 age- and sex‐matched apparently healthy persons. We used the Psoriasis Area and Severity Index (PASI) score to evaluate psoriasis severity. Biopsies from 30 lesional, 30 perilesional, and 20 control-skin patients were subjected to histopathological and immunohistochemical evaluations of Plexin-B2. There was significant stepwise overexpression of Plexin-B2 in proliferating keratinocytes from controls (66 ± 31.02) to perilesional (116 ± 41.95) and lesional (159.7 ± 63.05) skin (P < .001). Also, Plexin-B2 showed significant overexpression in dermal inflammatory cells of lesional psoriatic skin (153.67 ± 72.71) when compared to controls skin (25.71 ± 11.34) (P < .001). There was a significant positive correlation between Plexin-B2 expression and psoriasis severity (r = 0.557; P < .001). Plexin-B2 could promote skin inflammation, as well as keratinocyte proliferation in psoriasis vulgaris; therefore, it may be used as a targeted therapy for psoriasis treatment.     

Comano's (Trentino) thermal water interferes with tumour necrosis factor-alpha expression and interleukin-8 production and secretion by cultured human psoriatic keratinocytes: yet other mechanisms of its anti-psoriatic action

Thermal balneotherapy with Comano's spa water (CW; Trentino, Italy) is beneficial for psoriasis and other skin disorders but its operative mechanisms are largely unknown. Previously, we showed that CW interferes with the production and secretion of IL-6 and various VEGF-A isoforms and with CK-16 expression by cultured human psoriatic keratinocytes. In this study, confluent cultures of epidermal keratinocytes isolated from the lesional areas of 9 psoriatic patients were exposed for 11-13 days to DMEM, whose chemicals had been dissolved in either deionised water (DW-DMEM, controls) or CW (CW-DMEM, treated cells), in order to assess the expression and secretion of TNF-alpha and IL-8 by such cells. The results gained by means of immunocytochemistry, Western immunoblotting (WB), and ELISA assays showed that CW exposure significantly down-regulated the intracellular levels of TNF-alpha, a key inducer of IL-8, IL-6, and other chemokines. However, no assayable TNF-alpha secretion occurred in keratinocyte-conditioned DW- and CW-DMEM samples. Moreover, the intracellular levels and secretion rates of IL-8 were also markedly reduced in the protein extracts and conditioned media of CW-DMEM-incubated keratinocytes. Notably, the most effective inhibition of IL-8 secretion was elicited by a 25% CW fraction in the DMEM. Altogether, our findings indicate that by attenuating at lesional skin sites the deregulated production and secretion of a cascade of several cytokines and chemokines (e.g. TNF- alpha, IL-8, IL-6, and various VEGF-A isoforms), and by offsetting the keratinocytes' abnormal differentiation program entailing CK-16 expression, CW balneotherapy may beneficially influence the clinical manifestations of psoriasis.     

Nuclear Factor Kappa B and Cyclo-Oxygenase-2: Two Concordant Players in Psoriasis Pathogenesis

Nuclear factor kappa B (NFκB) is a key regulatory element in a variety of immune and inflammatory pathways, cellular proliferation, differentiation and apoptosis. Cyclo-oxygenase 2 (COX2) is one of the downstream targets of NFκB. The current work aimed to explore the possible role of NFκB and COX2 in psoriasis pathogenesis through their immunohistochemical (IHC) expression in skin biopsies of this disease and correlating this expression with clinico-pathological parameters of studied cases. 103 subjects were studied; including 58 cases with psoriasis vulgaris (lesional and perilesional skin) and 45 normal, age- and gender-matched subjects, as a control group. NFκB and COX2 expressions were evaluated using standard IHC techniques. NFκB and COX2 were upregulated in psoriasis lesional skin compared to perilesional (p?p?p?=?0.02 for both), severe degree of perivascular inflammatory infiltrate (p?=?0.03 and 0.002, respectively) and thin suprapapillary epidermis (p?=?0.003 and 0.006, respectively). Significant positive correlation was noted between NFκB and COX2 H scores in epidermis (r?=?0.41, p?=?0.02) and dermis (r?=?0.6, p?=?0.04) of lesional skin. Significant positive correlation between NFκB H score and PASI score (r?=?0.38, p?=?0.04) and between COX2 H score and PASI score (r?=?0.52, p?相似文献   

Projection of pro-opiomelanocortin neurons from the rat arcuate nucleus to the midbrain central gray as demonstrated by double staining with retrograde labeling and immunohistochemistry

Conjugate of horseradish peroxidase and wheat germ agglutinin (HRP-WGA conjugate) was injected into the midbrain central gray (MCG) of three adult rats. Frontal sections of the diencephalon were first treated with diaminobenzidine and hydrogen peroxide to detect the retrogradely transported conjugate. They were then stained immunohistochemically to detect pro-opiomelanocortin (POMC)-derived peptides (ACTH, beta-endorphin and alpha-MSH). The coexistence of the three POMC-derived peptides was confirmed by the immunohistochemistry of three consecutive sections stained with antiserum specific to each peptide. Some of the neuronal perikarya distributed in and around the arcuate nucleus were positive to the immunohistochemical stain for POMC-derived peptides, and, concomitantly, were labeled with HRP-WGA conjugate, which indicated that they projected to the MCG. They were mostly concentrated in the rostral three-fifths of the arcuate nucleus. The finding that some of the POMC neurons in the arcuate nucleus project to the midbrain central gray deserves interest, because the central gray is involved in analgesia induced by opioid peptides.     

Functional relationships between three novel homozygous mutations in the ACTH receptor gene and familial glucocorticoid deficiency

Familial glucocorticoid deficiency (FGD) is an autosomal recessive disorder characterized by a glucocorticoid adrenal insufficiency without mineralocorticoid deficiency. Mutations of the ACTH receptor (MC2-R) gene have been reported in some FGD cases, but only a few of them have been functionally studied. We reported clinical features and MC2-R gene analysis in three families. For each proband, an homozygous mutation was identified after amplification and sequencing of the whole intronless MC2-R gene. One mutation converted Val-142 located in the second intracellular loop to Leu. Another mutation in the sixth transmembrane domain converted Ala-233 to Pro. The last mutation converted the negatively charged Asp-103 in the first extracellular loop to an uncharged Asn. Functional studies of these mutations as well as the S120R mutation were performed after stable transfection of M3 cells and measurement of ACTH-induced cAMP production. For the S120R, V142L, and A233P mutated MC2-R, cAMP production curves were similar to that obtained with M3 parental cells, confirming that these mutations are responsible for the FGD in the affected patients. The D103N-mutated MC2-R had an impaired cAMP response to physiological doses of ACTH, but the maximal response at very high concentrations of ACTH was similar to that obtained for the wild-type MC2-R. All these results demonstrated clear relationships based on functional studies between MC2-R homozygous mutations and FGD phenotype.