Synergistic Potential of α-Melanocyte Stimulating Hormone Based Analogues with Conventional Antibiotic against Planktonic, Biofilm-Embedded, and Systemic Infection Model of MRSA

The repotentiation of the existing antibiotics by exploiting the combinatorial potential of antimicrobial peptides (AMPs) with them is a promising approach to address the challenges of slow antibiotic development and rising antimicrobial resistance. In the current study, we explored the ability of lead second generation Ana-peptides viz. Ana-9 and Ana-10, derived from Alpha-Melanocyte Stimulating Hormone (α-MSH), to act synergistically with different classes of conventional antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). The peptides exhibited prominent synergy with β-lactam antibiotics, namely, oxacillin, ampicillin, and cephalothin, against planktonic MRSA. Furthermore, the lead combination of Ana-9/Ana-10 with oxacillin provided synergistic activity against clinical MRSA isolates. Though the treatment of MRSA is complicated by biofilms, the lead combinations successfully inhibited biofilm formation and also demonstrated biofilm disruption potential. Encouragingly, the peptides alone and in combination were able to elicit in vivo anti-MRSA activity and reduce the bacterial load in the liver and kidney of immune-compromised mice. Importantly, the presence of Ana-peptides at sub-MIC doses slowed the resistance development against oxacillin in MRSA cells. Thus, this study highlights the synergistic activity of Ana-peptides with oxacillin advocating for the potential of Ana-peptides as an alternative therapeutic and could pave the way for the reintroduction of less potent conventional antibiotics into clinical use against MRSA infections.

Evaluation of the therapeutic efficacy of 213Bi-labelled DOTA-conjugated alpha-melanocyte stimulating hormone peptide analogues in melanocortin-1 receptor positive preclinical melanoma model

Melanocortin-1 receptor (MC1-R) targeting alpha-melanocyte stimulating hormone-analogue (α-MSH) biomolecules labelled with α-emitting radiometal seem to be valuable in the targeted radionuclide therapy of MC1-R positive melanoma malignum (MM). Herein is reported the anti-tumor in vivo therapeutic evaluation of MC1-R-affine [213Bi]Bi-DOTA-NAPamide and HOLDamide treatment in MC1-R positive B16-F10 melanoma tumor-bearing C57BL/6J mice. On the 6th, 8th and 10th days post tumor cell inoculation; the treated groups of mice were intravenously injected with approximately 5 MBq of both amide derivatives. Beyond body weight and tumor volume assessment, [68Ga]Ga-DOTA-HOLDamide and NAPamide-based PET/MRI scans, and ex vivo biodistribution studies were executed 30,- and 90 min postinjection. In the PET/MRI imaging studies the B16-F10 tumors were clearly visualized with both 68Ga-labelled tracers, however, significantly lower tumor-to-muscle (T/M) ratios were observed by using [68Ga]Ga-DOTA-HOLDamide. After alpha-radiotherapy treatment the tumor size of the control group was larger relative to both treated cohorts, while the smallest tumor volumes were observed in the NAPamide-treated subclass on the 10th day. Relatively higher [213Bi]Bi-DOTA-NAPamide accumulation in the B16-F10 tumors (%ID/g: 2.71 ± 0.15) with discrete background activity led to excellent T/M ratios, particularly 90 min postinjection. Overall, the therapeutic application of receptor selective [213Bi]Bi-DOTA-NAPamide seems to be feasible in MC1-R positive MM management.

In Vivo evaluation of newly synthesized 213Bi-conjugated alpha-melanocyte stimulating hormone (α-MSH) peptide analogues in melanocortin-1 receptor (MC1-R) positive experimental melanoma model

Given the rising pervasiveness of melanocortin-1 receptor (MC1-R) positive melanoma malignum (MM) and pertinent metastases, radiolabelled receptor-affine alpha-melanocyte stimulating hormone-analogue (α-MSH analogue) imaging probes would be of crucial importance in timely tumor diagnostic assessment. Herein we aimed at investigating the biodistribution and the MM targeting potential of newly synthesized ²¹³Bi-conjugated MC1-R specific peptide-based radioligands with the establishment of MC1-R overexpressing MM preclinical model. DOTA-conjugated NAP, -HOLD, -FOLD, -and MARSamide were labelled with ²¹³Bi. Ex vivo biodistribution studies were conducted post-administration of 3.81 ± 0.32 MBq [²¹³Bi]Bi-DOTA conjugated deriva-tives into twenty B16-F10 tumor-bearing C57BL/6 J and healthy mice. Organ Level Internal Dose Assessment (OLINDA) and IDAC-Dose were used to calculate translational data-based absorbed radiation dose in human organs. Moderate or low %ID/g uptake of [²¹³Bi]Bi-DOTA conjugated NAP, -HOLD, -and MARSamide and significantly increased [²¹³Bi]Bi-DOTA-FOLDamide accumulation was observed in the thoracic and abdominal organs (p ≤ 0.01). High [²¹³Bi]Bi-DOTA-NAP (%ID/g:3.76 ± 0.96), -and FOLDamide (%ID/g:3.28 ± 0.95) tumor tracer activity confirmed their MC1-R-affinity. The bladder wall received the highest radiation absorbed dose followed by the kidneys (bladder wall: 1.95·10^-2 and 8.97·10^-2 mSv/MBq; kidneys: 7.47·10^-3 vs. 5.88·10^-2 mSv/MBq measured by IDAC and OLINDA; respectively) indicating the suitability of the NAPamide derivative for clinical use. These novel [²¹³Bi]Bi-DOTA-linked peptide probes displaying meaningful MC1-R affinity could be promising molecular probes in MM imaging.

Stimulation of melanocortin-3 receptors accelerates the satiation process and increases the α-MSH expression in high-fat diet-fed rats

The knowledge about the role of MC3 receptors (MC3r) in the regulation of feeding behavior is limited. The present study was conducted to determine whether MC3r mediates the hypophagic effects of the melanocortins under conditions of positive energy balance. Male Wistar rats were fed with a high-fat diet (HFD) for 15 days and on day 16 the animals received an intracerebroventricular injection of the following treatments: Vehicle, D-Trp8-γ-melanocyte-stimulating hormone (MSH; MC3r agonist), SHU9119 (MC3r/MC4r antagonist), or D-Trp8-γ-MSH+SHU9119. Food intake was measured and the behavioral satiety sequence (BSS) analysis was carried out during the first hour of the dark phase. The c-Fos and α-MSH immunoreactivity in the arcuate nucleus (ARC) was evaluated 60 min later the onset of food intake. The results indicated that D-Trp8-γ-MSH decreased the ingestion of the HFD and this effect is associated with the early development of the satiation process Moreover, the D-Trp8-γ-MSH increased the accumulation of the α-MSH in the ARC and the c-Fos activity in the PVN. The antagonist SHU9119 partially prevented the D-Trp8-γ-MSH-induced hypophagia. Moreover, behavioral analysis suggests that central activation of MC3r accelerated the cessation of feeding in conditions of positive energy balance; the possible role of MC4r is discussed. Present data indicate that central stimulation of MC3r prevented the overconsumption of the HFD without affecting the natural satiation process, suggesting a potential use of MC3r for the treatment of eating disorders that are stimulated by hypercaloric diets. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Evolution of proopiomelanocortin

Proopiomelanocortin (POMC) belongs to the opioid/orphanin gene family whose peptide precursors include either opioid (YGGF) or the orphanin/nociceptin core sequences (FGGF). In addition to POMC the family includes the proenkephalin (PENK), prodynorphin (PDYN), and nociceptin/proorphanin (PNOC) precursors. The opioid core sequence in POMC is incorporated by the β-endorphin that occupies the C-terminal region but this propeptide also exhibits at least two "alien" melanocortin core sequences (HFRW). An ACTH/MSH fragment merged into the opioid fragment not earlier than the two tetraploidizations of the vertebrate genome. Therefore, POMC exhibit a complex "evolutionary life" since the gene has coevolved together with two different receptor systems, i.e., opioid and melanocortin following a horse trading system. In this article, we summarize the different evolutionary hypotheses proposed for POMC evolution.

Inhibiting roles of melanin-concentrating hormone for skin pigment dispersion in barfin flounder, Verasper moseri

Barfin flounders change their surface color pattern to match their background. We have reported evidence of the association between hormones and body color changes in this fish. First, bolus intraperitoneal injection with melanin-concentrating hormone (MCH) immediately turned the skin color pale, while injection with melanocyte-stimulating hormone (MSH) did not change the skin color. Second, gene expression levels of MCH change in response to background color, while those of MSH do not. We also reported the expression of an MCH receptor gene (Mch-r2) in the skin of this fish. In this study, we aimed to further evaluate the roles of MCH in skin color change. First, long-term adaptation of adult barfin flounder to black or white background colors induced significantly different pigment migration patterns in both melanophores and xanthophores (P<0.05). However, continuous intraperitoneal injection with MCH did not influence chromatophore proliferation. Then, using in vitro experiments, we found that MCH aggregates both melanophores and xanthophores, and inhibits the pigment-dispersing activity of MSH in a similar manner. Finally, we identified transcripts of Mch-r2 in cells isolated from both melanophores and xanthophores. Taken together, the evidence suggests that MCH aggregates pigments via MCH-R2 in concert with the nervous system by overcoming the melanin-dispersing activities of MSH in barfin flounder.

Structure and chemistry of the peptide hormones of the intermediate lobe

The peptide hormones of the intermediate lobe are derived from a common precursor protein and are therefore biogenetically and structurally related. They represent a group of linear, flexible peptides which elicit a variety of physiological response. Structure-activity studies have shown that different segments of adjacent amino acid residues have a specific function (e.g. address, message, potentiation) in the interaction of each of these hormones with its receptor(s). This kind of organization of hormonal information is called sychnologic; it is the basic for the pleiotropic action of the opiomelanocortin peptides, i.e. the ability of related peptides to interact with different types of receptors in different target cells. Labelled peptide hormones with radioactive, fluorescent, or photolabile groups at defined sites are a prerequisite for studying hormone-receptor interaction. Multi-labelled derivatives of alpha-MSH are suitable for degradation and intracellular incorporation studies. Photoaffinity labelling of melanophore receptors with azidophenyl-containing analogues of alpha-MSH produces an irreversible stimulation of pigment cells. Covalent conjugates between peptide hormone receptors. These conjugates exhibit remarkable properties such as superpotency, strongly enhanced receptor affinity and prolonged action.

Increasing our understanding of pigmentary disorders

This article focuses on developments in pigmentary disorders that extend dermatologists' understanding of the field. Areas that are reviewed include the basic biochemistry, pharmacology, and physiology of the melanocortin system; melanosome development; genetic diseases associated with pigmentary disorders; pigmentary disorders secondary to systemic disease; drug-induced hyperpigmentation; environmental exposure to chemicals; and primary disorders of hyperpigmentation such as melasma and lentigines. Basic, clinical, and epidemiological research, along with a number of clinical case reports, were included in the review. This article also reports on the new health-related quality-of-life instrument (MELASQOL) that has been developed for women with melasma.

The Role of Melanocyte-Stimulating Hormone in Insulin Resistance and Type 2 Diabetes Mellitus

In humans, mice, and other mammals, the melanocortin system consists of four peptide hormones with a core amino acid sequence of histidine-phenylalanine-arginine-tryptophan and five melanocortin receptors. Both the melanocortin hormones and their receptors are produced in diverse tissues throughout the body. The ligand of primary interest for treatment of insulin resistance is alpha-melanocyte-stimulating hormone (alpha-MSH), which is derived, as are all melanocortins, from tissue-specific post-translational proteolytic processing of the pro-opiomelanocortin (POMC) precursor protein. Recent results have shown that alpha-MSH is the complement of leptin in the endocrine circuit, regulating bodyweight, food intake, and metabolic rate. alpha-MSH can decrease bodyweight, weight gain, and food intake in mice with diet-induced and genetic obesity. As obesity is a major risk factor for type 2 diabetes mellitus, it was reasonable to investigate the endocrine agents involved in obesity for their involvement in diabetes. alpha-MSH analogs have also been shown to affect blood glucose levels in some mouse models of obesity. For instance, the POMC null mouse is extremely sensitive to insulin in an insulin tolerance test, while being otherwise euglycemic. The results from rodent studies with alpha-MSH suggest reciprocal effects: alpha-MSH appears to increase sensitivity to insulin when present in the CNS, while alpha-MSH in the periphery is necessary for insulin resistance. Should these trends be validated in humans, alpha-MSH-based therapeutics specifically active in the CNS or peripheral circulation may be promising for the treatment of type 2 diabetes.

Autoantibodies against neuropeptides are associated with psychological traits in eating disorders

Previously, we identified that a majority of patients with anorexia nervosa (AN) and bulimia nervosa (BN) as well as some control subjects display autoantibodies (autoAbs) reacting with alpha-melanocyte-stimulating hormone (alpha-MSH) or adrenocorticotropic hormone, melanocortin peptides involved in appetite control and the stress response. In this work, we studied the relevance of such autoAbs to AN and BN. In addition to previously identified neuropeptide autoAbs, the current study revealed the presence of autoAbs reacting with oxytocin (OT) or vasopressin (VP) in both patients and controls. Analysis of serum levels of identified autoAbs showed an increase of IgM autoAbs against alpha-MSH, OT, and VP as well as of IgG autoAbs against VP in AN patients when compared with BN patients and controls. Further, we investigated whether levels of these autoAbs correlated with psychological traits characteristic for eating disorders. We found significantly altered correlations between alpha-MSH autoAb levels and the total Eating Disorder Inventory-2 score, as well as most of its subscale dimensions in AN and BN patients vs. controls. Remarkably, these correlations were opposite in AN vs. BN patients. In contrast, levels of autoAbs reacting with adrenocorticotropic hormone, OT, or VP had only few altered correlations with the Eating Disorder Inventory-2 subscale dimensions in AN and BN patients. Thus, our data reveal that core psychobehavioral abnormalities characteristic for eating disorders correlate with the levels of autoAbs against alpha-MSH, suggesting that AN and BN may be associated with autoAb-mediated dysfunctions of primarily the melanocortin system.

Targeted reduction of complex models with time scale hierarchy--a case study

With the increasing flow of biological data there is a growing demand for mathematical tools whereby essential aspects of complex causal dynamic models can be captured and detected by simpler mathematical models without sacrificing too much of the realism provided by the original ones. Given the presence of a time scale hierarchy, singular perturbation techniques represent an elegant method for making such minimised mathematical representations. Any reduction of a complex model by singular perturbation methods is a targeted reduction by the fact that one has to pick certain mechanisms, processes or aspects thought to be essential in a given explanatory context. Here we illustrate how such a targeted reduction of a complex model of melanogenesis in mammals recently developed by the authors provides a way to improve the understanding of how the melanogenic system may behave in a switch-like manner between production of the two major types of melanins. The reduced model is shown by numerical means to be in good quantitative agreement with the original model. Furthermore, it is shown how the reduced model discloses hidden robustness features of the full model, and how the making of a reduced model represents an efficient analytical sensitivity analysis. In addition to yielding new insights concerning the melanogenic system, the paper provides an illustration of a protocol that could be followed to make validated simplifications of complex biological models possessing time scale hierarchies.

ON THE ACTION OF COLCHICINE, THE MELANOCYTE MODEL

The effect of colchicine was studied on the rapid, reversible darkening of frog skin under the influence of melanocyte-stimulating hormone (MSH). Darkening is due to dispersion of melanin granules in melanocytes and is thought to be accompanied by a gel-to-sol cytoplasmic transformation. After subsequent washing, the skin lightens, with aggregation of melanin granules and cytoplasmic gelation. Preincubation of skin with colchicine had the following effects: 1. Darkening induced by MSH was increased in comparison to control skins, and on removal of MSH, lightening was inhibited. Inhibition was a function of both concentration (1 x 10^–5 to 9 x 10^–5M) and exposure time (2 to 30 minutes). Once established, inhibition was maintained throughout the remainder of the experiment. 2. The same effects were noted (a) when darkening was effected by agents other than MSH (ATP) 0.9 x 10^–3M; caffeine, 5.2 x 10^–3M; ethyl acetate, 0.8 x 10^–2M), and (b) when lightening was effected by addition of chemical agents (melatonin, 4.3 x 10^–10M; hydrocortisone, 1 x 10^–3M; norepinephrine, 1 x 10^–3M), instead of by washing. 3. Colchicine alone produced a gradual, irreversible, dosage-dependent darkening over several hours. This darkening was inhibited by melatonin, 4.3 x 10^–10M. The melanocyte model is used to construct a general theory of colchicine action on living cells, an action resulting in decreased protoplasmic viscosity. In this formulation colchicine lowers the potential limit of protoplasmic gelation, and does it rapidly, reversibly, in low concentration, in a dosage-dependent manner, and without killing the cell. The theory allows interpretation of "synergism" and "antagonism" to colchicine by other substances. It suggests a tentative approach to the understanding of colchicine action in acute gouty arthritis, where interference with ameboid activities of polymorphonuclear leukocytes is one possible aspect of the anti-inflammatory effect of colchicine. Finally, the colchicine-treated melanocyte is viewed as a good, live physical model that can be used to elucidate some fundamental biological properties.

Melanocortin receptors: identification and characterization by melanotropic peptide agonists and antagonists

Hormones are chemical messengers released from cells to act on and control the activity of other cells. Hormonal ligands initiate their actions by interacting with receptive substances (Langley, 1906) of the target cells. These receptors are proteins that are either integral components of the cell membrane or are localized cytoplasmically within cells. Ligand-receptor interaction results in either the stimulation or inhibition of cellular activity. Since most hormones bind rather specifically to receptors possessed by their target cells, labeling of hormonal ligands can be utilized to identify and localize cells within an animal. In this report we discuss what is presently known about melanocortin receptors (MCRs) as studied by the use of labeled melanotropic peptide ligands.

Ovarian melanotropic peptides and adaptation in two teleostean species: Sparus aurata L. and Dicentrarchus labrax L

The ovarian tissue of Dicentrarchus labrax and Sparus aurata displays two immunoreactive peaks that correspond to the elution time of human des-acetyl alpha-MSH [ACTH(1-13)-amide] and human alpha-MSH. In view of the close identity between the primary structure of fish and human alpha-MSH, these data demonstrate that two MSH-related peptides are present both in sea bream and sea bass ovary. alpha-MSH-like immunoreactivity was found within both granulosa and thecal layers of mature follicles, as well as in the cytoplasm of oogonia of sea bream and sea bass ovary. Gonadal content of ACTH(1-13)-amide and alpha-MSH display differences with regard to season, showing the highest peptide levels in reproductive animals. Moreover, the alpha-MSH content is significantly higher in the ovary of fish farm animals, whereas that of ACTH(1-13)-amide prevails in wild fish ovary.

The use of a chelating derivative of alpha melanocyte stimulating hormone for the clinical imaging of malignant melanoma

A novel chelating derivative of alpha melanocyte stimulating hormone, bis MSH-DTPA, has been used for the diagnostic targeting of malignant melanoma. 15 patients were investigated of whom nine were shown by other means to have active disease at the time of the scan. Tumours were imaged in all of these nine patients. Of a total of 46 lesions over 10 mm encountered, 41 (89%) were imaged. There were no false positives and in two cases bisMSH-DTPA was instrumental in reversing diagnoses made using ultrasound. Derivatives of melanocyte stimulating hormone may be of considerable value in targeting melanomas.

Role of the dermal tracts in the pigment pattern of the frog

The pigment pattern of the ventral skin of the frog Rana esculenta is compared in skin fragments grown for 24 hr with or without antiserum directed to fibronectin (anti-FN). Melanocyte-stimulating hormone (MSH) was added to the medium during the last hour in culture in order to enhance visibility of melanophores in the ventral region of the frog skin. Comparison of these two treatments provides information regarding the precise localization of melanophores in the dermal tracts and their involvement in the pigment pattern of the ventral frog skin. In this regard, the whitish pigment pattern of skin fragments is compared to the tiny black spots found on anti-FN treated skin fragments and the abundant blotchy spots found on skin cultured alone. The distribution of melanophores in the dermal tracts observed in vertical semithin sections is found to be related to the three different levels of the dermal tracts. This report demonstrates the importance of fibronectin as a substrate for the melanophore migration, the importance of the tract level for the melanophore localization both involved in the pigment pattern of the ventral skin.

Immunohistochemical study on the development of the adenohypophysial cells in the lizard Gallotia galloti

Immunohistochemical methods have been used to study the embryonic and postnatal development of the hormone-producing cells in the adenohypophysis of the lizard Gallotia galloti. In this species, Rathke's pouch is formed between stages 30 to 32 of the embryonic development, although the first sign of immunoreactivity to antisera against adenohypophysial hormones occurs in stage 33 in the pars distalis anlage. These cells derive from the dorsal face of Rathke's pouch and are immunoreactive to anti-ACTH serum. The cytodifferentiation of ACTH and MSH cells occurs in the pars intermedia in stage 34. The TSH cells appear at stage 35 and the gonadotrope cells at stage 37. These cells derive from both the dorsal and ventral face of the Rathke's pouch. The LTH cells are revealed at stage 39 and are only originated from the dorsal face. The STH cells, which come from the dorsal as well as ventral face, are the last secretory cells differentiated just before hatching. During postnatal development an increase and also a redistribution of the immunoreactive cells occur until acquiring the adult distribution.

[Structural organization of alpha-melanotropin molecules]

Using a semi-empirical method, and a priori conformational analysis of the tridecapeptide alpha-melanocyte-stimulating (alpha-MSH) was carried out. The spatial structure of alpha-MSH can be described by ten low-energy conformations. Calculations produced the values of all dihedral angles of the backbones and side chains of these forms as well as intra- and inter-residue interaction energies.

Microsequencing evidence for the maturation of human proopiomelanocortin into an 18 amino acid beta-melanocyte stimulating hormone [h beta MSH(5-22)] in nonpituitary tissue

Sixty pmoles of a material with molecular size, immunological, and RP-HPLC characteristics identical to that of h beta MSH(5-22) were purified from a bronchial carcinoid tumor responsible for the ectopic ACTH syndrome. The first 16 cycles of microsequencing revealed the following sequence: Asp-Glu-Gly-Pro-Tyr-Arg-Met-Glu-X-Phe-Arg-Trp-Gly-X-Pro- Pro-, identical to the first 16 amino acids of h beta MSH(5-22). Since this material was recognized by an antibody which requires the free COOH-terminal Asp22 residue, it can be assumed that it is indeed h beta MSH(5-22). We also show that neither the 5 N acetic acid nor the 1 N HCl extraction procedure artefactually generated h beta MSH-like material in normal or tumoral human pituitaries and in nonpituitary tumors. We conclude that h beta MSH(5-22) is a normal maturation product of proopiomelanocortin in the human nonpituitary tissues which express its gene, including the hypothalamus and ACTH-secreting tumors.

Theoretical conformational analysis of brain peptides. beta-Melanocyte-stimulating hormone

Using a semi-empirical method, an a priori conformational analysis of the octadecapeptide beta-melanocyte-stimulating hormone (beta-MSH) was carried out. The spatial structure of beta-MSH can be described by eight low-energy conformations, yielded by combinations of the most stable states of the respective free fragments. Calculations produced the values of all dihedral angles of the backbones and side chains of these forms as well as intra- and inter-residue interaction energies.

The application of fluorescein isothiocyanate and high-performance liquid chromatography for the microsequencing of proteins and peptides

Amino acid derivatives of fluorescein isothiocyanate have been separated by reverse-phase high-performance liquid chromatography in 45 min, using a linear gradient formed from acetone and 10 mM sodium phosphate buffer (pH 7.0) at 60 degrees C. The fluorescence of the derivatives has been used for detection giving a sensitivity of less than 0.5 pmol for a single component. Applications of this method to the sequence analyses of egg white lysozyme and salmon beta-melanotropin are also described.

Serotonin binding sites. I. Structures of sites on myelin basic protein, LHRH, MSH, ACTH, interferon, serum albumin, ovalbumin and red pigment concentrating hormone

We report the results of nuclear magnetic resonance spectroscopy studies of combinations of serotonin (5-hydroxytryptamine) with the tryptophan peptide sequence and similar peptides from myelin basic protein. The binding site appears to consist of the sequence Arg Phe Ser Trp. Similar serotonin binding sites were found to exist on LHRH (Tyr Ser Trp) and MSH-ACTH tetrapeptide (Phe Arg Trp). These binding sites are specific to serotonin as is demonstrated by lack of binding by dopamine, histamine, acetylcholine and a dozen other pharmacologically active amines and indoles. Drugs known to affect serotonin levels, e.g., fenfluramine and L-DOPA, bind weakly to these sites. Structural and functional similarities between the tryptophan peptide, LHRH, and MSH-ACTH with an ACTH-like peptide of human leukocyte interferon, with human and bovine serum albumin, hen ovalbumin, and with red pigment concentrating hormone suggest that the latter peptides may also contain similar serotonin binding sites. The elucidation of serotonin binding sites on these peptides and proteins has implications for understanding various aspects of cancer, autoimmunity, neurological disease, and peptide hormone control.

Capsaicin pretreatment prevents disruption of the blood-aqueous barrier in the rabbit eye

Capsaicin, the irritating agent of red pepper, produces ocular inflammation through a neurogenic mechanism. The present study is concerned with the long-term effects of capsaicin pretreatment on the capacity of the eye to respond to different inflammatory stimuli. Following retrobulbar injection of capsaicin to rabbits the aqueous flare response induced by subsequent infrared irradiation (IR) of the iris, subcutaneously administered alpha-melanocyte-stimulating hormone (alpha-MSH) and exogenously administered prostaglandin E2 (PGE2) was reduced greatly. In the case of IR and alpha-MSH the reduced responsiveness was manifest for several weeks after capsaicin pretreatment, involving first the capsaicin-treated eye, but later also the contralateral control eye. After 2-3 months the aqueous flare response was normal in both eyes. In the case of PGE2 the responsiveness was reduced for a shorter time; after 3 weeks the response was normal in both eyes. The results indicate that all three stimuli tested are at least partly dependent upon an intact sensory innervation to disrupt the blood-aqueous barrier, but that the mechanism of action of PGE2 is different from that of IR and alpha-MSH.

Iodination of beta-melanotropin. Time course analysis of reaction mixtures by high pressure liquid chromatography and characterization of biologically active mono- and diiodo-beta-melanotropin

The production of highly purified, chemically well defined, iodinated beta-melanotropin possessing full biological activity is described. beta-Melanotropin, purified by high pressure liquid chromatography, was iodinated using Iodogen as the oxidizing agent. Biological activity was recovered, following iodination, by incubating the iodinated peptide mixture in 0.75 M dithiothreitol at 37 degrees C for 18-24 h. The qualitative and quantitative effects of dithiothreitol and the changes that occurred in the iodination mixture with time were examined using high pressure liquid chromatography. This separation technique has proved to be a useful tool both for optimizing the iodination procedure and for the rapid, efficient purification of mono- and diiodinated beta-melanotropins. Amino acid analysis of these two peptides revealed modifications only of the one tyrosine residue (Tyr 5): the expected incorporation of iodine to form mono- or diiodo tyrosine. Monoiodo-beta-melanotropin had full biological activity, as measured by tyrosinase stimulation in Cloudman S91 melanoma cells, while diiodo-beta-melanotropin was an order of magnitude less active.

Complete sequence of the glycosylated amino terminal segment of porcine pro-opiomelanocortin

The complete sequence of an anterior pituitary glycopeptide corresponding to the first 80 amino acid residues of the amino terminal of pro-opiomelanocortin (POMC) after excision of the signal peptide is reported. This peptide isolated from pig pituitaries shows considerable sequence conservation with its predicted homologues from bovine, murine and human species.

Adrenocorticotropin-like and alpha-melanotropin-like peptides in a subpopulation of human gastrin cell granules: bioassay, immunoassay, and immunocytochemical evidence

Adrenocorticotropin (ACTH)-like and alpha-melanotropin (alpha-MSH)-like peptides have been localized to a subpopulation of cytoplasmic (secretory) granules of human antropyloric gastric cells and of fetal and neoplastic gastrin cells. These granules also store gastrin and belong to the electron-dense variety of gastrin cell granules. Gastrin cells also contain granules of low to medium electron density; these store only gastrin and do not react with ACTH or alpha-MSH antisera. The alpha-MSH immunoreactive peptide was shown also to display alpha-MSH bioactivity by a combined immunosorbent-bioassay technique. This peptide cochromatographs with synthetic alpha-MSH in several systems and is not detected in oxyntic mucosa or in gastric muscle wall. As in the pituitary intermediate lobe, the alpha-MSH-like peptide may be formed by cleavage of ACTH-like peptides also in gastrin cells. These data provide additional evidence for local formation of ACTH/alpha-MSH-related peptides in gastrin cells and suggest a heterogenous peptide make-up of endocrine cell granules.

Ordered conformation of polypeptides and proteins in acidic dodecyl sulfate solution

The conformation of some polypeptides and proteins in sodium dodecyl sulfate (NaDodSO4) solutions was studied by circular dichroism. The type and extent of induced structure depend on their helix- and beta-forming potential. Anionic side groups in segments of helix or beta form tend to destabilize the ordered structure unless they are protonated. beta-Endorphin has one Glu inside a predicted helical segment; its helicity in a NaDodSO4 solution is enhanced at pH below 4. alpha-Melanocyte-stimulating hormone having a Glu in a beta segment undergoes a pH-induced coil to beta transition in 1.25 mM NaDodSO4 (excess surfactant will disrupt the beta form). Reduced somatostatin assumes a beta form in 2 mM NaDodSO4 and a partial helix in 25 mM NaDodSO4, both of which are unchanged in acidic pH because it lacks -COOH groups. The unordered gastrin with five consecutive Glu's becomes helical in a NaDodSO4 solution at pH 4. Neurotensin with one Glu has no structure-forming potential and is unordered in both neutral and acidic NaDodSO4 solutions. This charge effect also manifests in segments of ordered structure for polypeptides and proteins such as glucagon, cytochrome c, parvalbumin, ribonuclease A, and lysozyme. The effect is especially predominant in tropomyosin that is rich in clusters of anionic side groups. Its more than 90% helicity is reduced to about one-half in a neutral NaDodSO4 solution, but most of it can be restored by lowering the pH to 2.4.

Alpha-melanocyte stimulating hormone induces gonadotropin release

The present study demonstrates that synthetic alpha-MSH given as a 2.5 mg intravenous bolus induces an unequivocal rise in LH and FSH in male subjects but not in female subjects during the low estrogen phase of the cycle.

Immunocytological detection and localization of a peptide reacting with an alpha-endorphin antiserum in the corticotropic and melanotropic cells of the trout pituitary (Salmo irideus Gibb)

In the pituitary of the trout, the corticotropic and melanotropic cells display a strong immunocytological reaction with alpha-endorphin antiserum. This reaction persists even when alpha-endorphin antisera treated with beta-1-24ACTH or alpha-MSH are used. In the absence of pharmacological tests on the endorphic potencies of the compounds involved in the immunoreaction, it is not yeat clear whether this reaction is due to the presence of an alpha-endorphin-like peptide or simply an immunologically related peptide without the properties of endorphin. However, the presence of such peptides in the fish pituitary is interesting from the comparative point of view.

Formaldehyde-ozone-induced fluorescence in pituitary ACTH cells: effect of adrenalectomy

ACTH and MSH cells of the pituitary are rich in peptides with NH2-terminaltryptophan, as revealed by fluorescence histochemistry. Adrenalectomy stimulates the ACTH cells but not the MSH cells. As a result, ACTH as well as tryptophyl-peptides disappear from the ACTH cells but not from the MSH cells. It is concluded that the tryptophyl-peptides are stored together with the respective hormone in the ACTH and MSH cells and that tryptophyl-peptides in the ACTH cells are released together with the hormone.

Melanocyte-stimulating hormone receptors on cultured guinea-pig melanocytes

Guinea-pig melanocytes in mixed epidermal cell cultures bind melanocyte-stimulating hormone in a distinct focal surface area in their perinuclear field and thus follow the same pattern previously described for Cloudman melanoma cells. The labeling index ranged from 18 to 34%. Pretreatment of cultures with trypsin leads to destruction of melanocyte-stimulating hormone receptors whereas neuraminidase has no such effect.