Peptides (v.48, #C)

Many data suggest the deep involvement of the substance P (SP)/neurokinin (NK)-1 receptor system in cancer: (1) Tumor cells express SP, NK-1 receptors and mRNA for the tachykinin NK-1 receptor; (2) Several isoforms of the NK-1 receptor are expressed in tumor cells; (3) the NK-1 receptor is involved in the viability of tumor cells; (4) NK-1 receptors are overexpressed in tumor cells in comparison with normal ones and malignant tissues express more NK-1 receptors than benign tissues; (5) Tumor cells expressing the most malignant phenotypes show an increased percentage of NK-1 receptor expression; (6) The expression of preprotachykinin A is increased in tumor cells in comparison with the levels found in normal cells; (7) SP induces the proliferation and migration of tumor cells and stimulates angiogenesis by increasing the proliferation of endothelial cells; (8) NK-1 receptor antagonists elicit the inhibition of tumor cell growth; (9) The specific antitumor action of NK-1 receptor antagonists on tumor cells occurs through the NK-1 receptor; (10) Tumor cell death is due to apoptosis; (11) NK-1 receptor antagonists inhibit the migration of tumor cells and neoangiogenesis. The NK-1 receptor is a therapeutic target in cancer and NK-1 receptor antagonists could be considered as broad-spectrum antitumor drugs for the treatment of cancer. It seems that a common mechanism for cancer cell proliferation mediated by SP and the NK-1 receptor is triggered, as well as a common mechanism exerted by NK-1 receptor antagonists on tumor cells, i.e. apoptosis.
Keywords: Angiogenesis; Cancer; Metastasis; NK-1 receptor; NK-1 receptor antagonists; Substance P;

AGH is a new hemoglobin alpha-chain fragment with antinociceptive activity by Natalia M. Ribeiro; Elaine F. Toniolo; Leandro M. Castro; Lilian C. Russo; Vanessa Rioli; Emer S. Ferro; Camila S. Dale (10-20).
Limited proteolysis of certain proteins leads to the release of endogenous bioactive peptides. Hemoglobin-derived peptides such as hemorphins and hemopressins are examples of intracellular protein-derived peptides that have antinociceptive effects by modulating G-protein coupled receptors activities. In the present study, a previously characterized substrate capture assay that uses a catalytically inactive form of the thimet oligopeptidase was combined with isotopic labeling and mass spectrometry in order to identify new bioactive peptides. Indeed, we have identified the peptide AGHLDDLPGALSAL (AGH), a fragment of the hemoglobin alpha-chain, which specifically bind to the inactive thimet oligopeptidase in the substrate capture assay. Previous peptidomics studies have identified the AGH as well as many other natural peptides derived from hemoglobin alpha-chain containing this sequence, further suggesting that AGH is a natural endogenous peptide. Pharmacological assays suggest that AGH inhibits peripheral inflammatory hyperalgesic responses through indirect activation of mu opioid receptors, without having a central nervous system activity. Therefore, we have successfully used the substrate capture assay to identify a new endogenous bioactive peptide derived from hemoglobin alpha-chain.
Keywords: Hemoglobin-derived peptides; Hemopressin; Opioid; Inflammation; Hyperalgesia;

Endothelial permeability in vitro and in vivo: Protective actions of ANP and omapatrilat in experimental atherosclerosis by Tomoko Ichiki; Ririko Izumi; Alessandro Cataliotti; Amy M. Larsen; Sharon M. Sandberg; John C. Burnett (21-26).
Increased arterial endothelial cell permeability (ECP) is considered an initial step in atherosclerosis. Atrial natriuretic peptide (ANP) which is rapidly degraded by neprilysin (NEP) may reduce injury-induced endothelial cell leakiness. Omapatrilat represents a first in class of pharmacological agents which inhibits both NEP and angiotensin converting enzyme (ACE). We hypothesized that ANP prevents thrombin-induced increases of ECP in human aortic ECs (HAECs) and that omapatrilat would reduce aortic leakiness and atherogenesis and enhance ANP mediated vasorelaxation of isolated aortas. Thrombin induced ECP determined by I125 albumin flux was assessed in HAECs with and without ANP pretreatment. Next we examined the effects of chronic oral administration of omapatrilat (12 mg/kg/day, n  = 13) or placebo (n  = 13) for 8 weeks on aortic leakiness, atherogenesis and ANP-mediated vasorelaxation in isolated aortas in a rabbit model of atherosclerosis produced by high cholesterol diet. In HAECs, thrombin-induced increases in ECP were prevented by ANP. Omapatrilat reduced the area of increased aortic leakiness determined by Evans-blue dye and area of atheroma formation assessed by Oil-Red staining compared to placebo. In isolated arterial rings, omapatrilat enhanced vasorelaxation to ANP compared to placebo with and without the endothelium. ANP prevents thrombin-induced increases in ECP in HAECs. Chronic oral administration of omapatrilat reduces aortic leakiness and atheroma formation with enhanced endothelial independent vasorelaxation to ANP. These studies support the therapeutic potential of dual inhibition of NEP and ACE in the prevention of increased arterial ECP and atherogenesis which may be linked to the ANP/cGMP system.
Keywords: Atrial natriuretic peptides; Neprilysin inhibitor; Angiotensin converting enzyme inhibitor; Atherosclerosis; Endothelium;

In vitro and in vivo pharmacological characterization of the novel neuropeptide S receptor ligands QA1 and PI1 by V. Camarda; C. Ruzza; A. Rizzi; C. Trapella; R. Guerrini; R.K. Reinscheid; G. Calo (27-35).
The pharmacological activity of the novel neuropeptide S (NPS) receptor (NPSR) ligands QA1 and PI1 was investigated. In vitro QA1 and PI1 were tested in calcium mobilization studies performed in HEK293 cells expressing the recombinant mouse (HEK293mNPSR) and human (HEK293hNPSRIle107 and HEK293hNPSRAsn107) NPSR receptors. In vivo the compounds were studied in mouse righting reflex (RR) and locomotor activity (LA) tests. NPS caused a concentration dependent mobilization of intracellular calcium in the three cell lines with high potency (pEC50 8.73–9.14). In inhibition response curve and Schild protocol experiments the effects of NPS were antagonized by QA1 and PI1. QA1 displayed high potency (pK B 9.60–9.82) behaving as a insurmountable antagonist. However in coinjection experiments QA1 produced a rightward swift of the concentration response curve to NPS without modifying its maximal effects; this suggests that QA1 is actually a slow dissociating competitive antagonist. PI1 displayed a competitive type of antagonism and lower values of potencies (pA 2 7.74–8.45). In vivo in mice NPS (0.1 nmol, i.c.v.) elicited arousal promoting action in the RR assay and stimulant effects in the LA test. QA1 (30 mg kg−1) was able to partially counteract the arousal promoting NPS effects, while PI1 was inactive in the RR test. In the LA test QA1 and PI1 only poorly blocked the NPS stimulant action. The present data demonstrated that QA1 and PI1 act as potent NPSR antagonists in vitro, however their usefulness for in vivo investigations in mice seems limited probably by pharmacokinetic reasons.
Keywords: Neuropeptide S; NPS receptor; NPSR antagonists; QA1; PI1; Calcium mobilization; Mouse; Locomotor activity; Righting reflex test;

Functional activity of murine intestinal mucosal cells is regulated by the glucagon-like peptide-1 receptor by Mamdouh H. Kedees; Yelena Guz; Marine Grigoryan; Gladys Teitelman (36-44).
To determine whether the glucagon-like peptide-1 receptor (GLP-1r) plays a role in the regulation of intestinal functional activity, we analyzed the distribution of the GLP-1r in mouse tissues and tested if tissues expressing the receptor respond to exendin-4 and exendin (9–39) amide, a GLP-1r agonist and antagonist respectively. In ileum, Glp1r mRNA level was two fold higher in extracts from epithelial cells than non-epithelial tissues. By immunohistochemistry, the receptor was localized to the mucosal cell layer of villi of ileum and colon, to the myenteric and submucosal plexus and to Paneth cells. Intravenous administration of exendin-4 to CD-1 mice induced expression of the immediate early gene c-fos in mucosal cells but not in cells of the enteric plexuses or in L cells of ileum. The induction of c-fos was inhibited by the voltage-gated sodium channel blocker tetrodotoxin. Exendin-4 also increased c-fos expression in ileal segments in vitro, suggesting that this action of the analog was independent of an extrinsic input. The induction of c-fos expression by exendin-4 was inhibited by exendin (9–39) amide, indicating that the action of exendin-4 was mediated by activation of the receptor. Our findings indicate that the GLP-1r is involved in ileal enterocyte and Paneth cell function, that the GLP-1 analog activates c-fos expression in the absence of an extrinsic input and that some of the actions of the receptor is/are mediated by voltage-gated Na channels.
Keywords: Glucagon like peptide-1 receptor; Enterocytes; Paneth cells; Enteric neurons;

Relationship between plasma mid-regional pro-adrenomedullin level and resistance to antihypertensive therapy in stable kidney transplant recipients by Yosuke Suzuki; Hiroki Itoh; Fumihiko Katagiri; Fuminori Sato; Kanako Kawasaki; Yukie Sato; Yuhki Sato; Hiromitsu Mimata; Masaharu Takeyama (45-48).
We investigated the relationship between plasma mid-regional pro-adrenomedullin (MR-proADM)-like immunoreactive substance (IS) level and clinical characteristics associated with renal failure or resistance to antihypertensive therapy in stable kidney transplant recipients. Forty-six Japanese kidney transplant recipients who underwent transplantation more than 90 days prior to the study were included. To evaluate resistance to antihypertensive therapy, we calculated the treatment intensity score of the antihypertensive drugs in each recipient. Morning blood samples were collected and plasma MR-proADM-IS levels were measured using an enzyme immunoassay. A significant correlation was observed between plasma MR-proADM-IS level with creatinine clearance or treatment intensity score. Multiple regression analysis identified plasma MR-proADM level and body mass index as significant independent factors associated with treatment intensity score. Plasma MR-proADM level may be a useful biomarker indicating the degree of resistance to antihypertensive therapy.

Secreted aspartic peptidases of Candida albicans liberate bactericidal hemocidins from human hemoglobin by Oliwia Bocheńska; Maria Rąpała-Kozik; Natalia Wolak; Grażyna Braś; Andrzej Kozik; Adam Dubin; Wataru Aoki; Mitsuyoshi Ueda; Paweł Mak (49-58).
Secreted aspartic peptidases (Saps) are a group of ten acidic hydrolases considered as key virulence factors of Candida albicans. These enzymes supply the fungus with nutrient amino acids as well as are able to degrade the selected host's proteins involved in the immune defense. Our previous studies showed that the human menstrual discharge is exceptionally rich in bactericidal hemoglobin (Hb) fragments – hemocidins. However, to date, the genesis of such peptides is unclear. The presented study demonstrates that the action of C. albicans isozymes Sap1–Sap6, Sap8 and Sap9, but not Sap7 and Sap10, toward human hemoglobin leads to limited proteolysis of this protein and generates a variety of antimicrobial hemocidins. We have identified these peptides and checked their activity against selected microorganisms representative for human vagina. We have also demonstrated that the process of Hb hydrolysis is most effective at pH 4.0, characteristic for vagina, and the liberated peptides showed pronounced killing activity toward Lactobacillus acidophilus, and to a lower degree, Escherichia coli. However, only a very weak activity toward Staphylococcus aureus and C. albicans was noticed. These findings provide interesting new insights into pathophysiology of human vaginal candidiasis and suggest that C. albicans may be able to compete with the other microorganisms of the same physiological niche using the microbicidal peptides generated from the host protein.
Keywords: Antibacterial; Bactericidal; Hemocidins; Hemoglobin; Menstruation; Microbicidal; Peptidases; Peptides; Sap; Secreted aspartic peptidases; Vagina;

Effects of recombinant trout leptin in superoxide production and NF-κB/MAPK phosphorylation in blood leukocytes by Giovanna Mariano; Romania Stilo; Giuseppe Terrazzano; Elena Coccia; Pasquale Vito; Ettore Varricchio; Marina Paolucci (59-69).
Studies in mammals indicate that leptin is a multifunctional cytokine involved in regulation of energy metabolism and the modulation of the immune function. However, evidence for an immunomodulatory effect of leptin in fish is still missing. At least in part, this lack of knowledge is due to the absence of materials and models. In this study, we produced trout recombinant leptin (rt-lep) and tested its capacity to trigger cellular pathways, usually active in mammal immune system cells. STAT3, NF-κB, and the three major MAPK cascades (JNK, p38 and ERK), were activated by rt-lep in in vitro incubations with blood leucocytes of the rainbow trout Oncorhynchus mykiss. We also showed that rt-lep causes a decrease in superoxide anion production in trout blood leucocytes. Thus our data indicate that as in mammals also in teleosts leptin plays pleiotropic activities. Importantly, its actions in fishes do not always conform to the picture emerging for mammals.
Keywords: Leptin; Rainbow trout leucocytes; Signaling; Superoxide anion;

Leptin as a marker for severity and prognosis of aneurysmal subarachnoid hemorrhage by Xiao-Feng Fan; Zhen-Hong Chen; Qiang Huang; Wei-Min Dai; Yuan-Qing Jie; Guo-Feng Yu; An Wu; Xin-Jiang Yan; Yun-Ping Li (70-74).
Leptin has been identified as a plasma marker for outcomes in traumatic brain injury and intracerebral hemorrhage. We further investigated whether leptin might serve as a marker for severity and prognosis in aneurysmal subarachnoid hemorrhage. One hundred and eight consecutive patients and 108 sex and age – matched healthy subjects were recruited. Plasma leptin levels were measured by enzyme-linked immunosorbent assay. Clinical severity was assessed using World Federation of Neurological Surgeons score and Fisher score. Mortality and poor long-term outcome (Glasgow outcome scale scores of 1–3) at 6 months were recorded. Plasma leptin levels on admission were substantially higher in patients than in healthy controls, and were significantly associated with the clinical severity. There was also a significant association between leptin levels and clinical outcomes at 6 months in multivariate logistic regression analysis. Using receiver operating characteristic curves, we calculated areas under the curve for clinical outcomes at 6 months. The predictive performance of leptin was similar to, but did not obviously improve those of World Federation of Neurological Surgeons score and Fisher score. Thus, leptin may indicate clinical severity of the initial bleeding and also have prognostic value for clinical outcomes in aneurysmal subarachnoid hemorrhage and may therefore help in guiding treatment decisions in the setting of aneurysmal subarachnoid hemorrhage.
Keywords: Leptin; Aneurysmal subarachnoid hemorrhage; Functional outcome; Mortality;

Differential mode of antimicrobial actions of arginine-rich and lysine-rich histones against Gram-positive Staphylococcus aureus by Shuu Morita; Chihiro Tagai; Takayuki Shiraishi; Kazuyuki Miyaji; Shawichi Iwamuro (75-82).
We previously reported the activities and modes of action of arginine (Arg)-rich histones H3 and H4 against Gram-negative bacteria. In the present study, we investigated the properties of the Arg-rich histones against Gram-positive bacteria in comparison with those of lysine (Lys)-rich histone H2B. In a standard microdilution assay, calf thymus histones H2B, H3, and H4 showed growth inhibitory activity against Staphylococcus aureus with minimum effective concentration values of 4.0, 4.0, and 5.6 μM, respectively. Laser confocal microscopic analyses revealed that both the Arg-rich and Lys-rich histones associated with the surface of S. aureus. However, while the morphology of S. aureus treated with histone H2B appeared intact, those treated with the histones H3 and H4 closely resembled each other, and the cells were blurred. Electrophoretic mobility shift assay results revealed these histones have binding affinity to lipoteichoic acid (LTA), one of major cell surface components of Gram-positive bacteria. Scanning electron microscopic analyses demonstrated that while histone H2B elicited no obvious changes in cell morphology, histones H3 and H4 disrupted the cell membrane structure with bleb formation in a manner similar to general antimicrobial peptides. Consequently, our results suggest that bacterial cell surface LTA initially attracts both the Arg- and Lys-rich histones, but the modes of antimicrobial action of these histones are different; the former involves cell membrane disruption and the latter involves the cell integrity disruption.
Keywords: Antimicrobial peptides; Histone H2B; Histone H3; Histone H4; Gram-positive bacteria; Lipoteichoic acid;

Orexigenic effects of endomorphin-2 (EM-2) related to decreased CRH gene expression and increased dopamine and norepinephrine activity in the hypothalamus by Luigi Brunetti; Claudio Ferrante; Giustino Orlando; Lucia Recinella; Sheila Leone; Annalisa Chiavaroli; Chiara Di Nisio; Rugia Shohreh; Fabio Manippa; Adriana Ricciuti; Adriano Mollica; Michele Vacca (83-88).
Endomorphin-1 (EM-1) and endomorphin-2 (EM-2) are opioid peptides which are selective partial agonists of μ-opioid receptor. We studied the effects of EM-2 injected into the arcuate nucleus (ARC) of the hypothalamus on feeding behavior and gene expression of orexigenic [agouti-related peptide (AgRP), neuropeptide Y (NPY) and orexin-A] and anorexigenic [cocaine and amphetamine-regulated transcript (CART), corticotrophin releasing hormone (CRH) and proopiomelanocortin (POMC)] peptides in male Wistar rats fed a standard laboratory diet. Furthermore, we evaluated the effects of EM-2 on dopamine (DA), norepinephrine (NE) and serotonin (5-hydroxytryptamine, 5-HT) steady state concentrations, in the hypothalamus. 64 rats (16 for each group of treatment) were injected into the ARC, at 9.00 am, with either vehicle or EM-2 (0.50–0.75 μmol/kg) or EM-2 (0.50 μmol/kg) plus β-funaltrexamine (0.20 μmol/kg). Food intake was recorded through 24 h following injection, and hypothalamic DA, NE, 5-HT levels and neuropeptide gene expression were evaluated 24 h after EM-2 administration. Compared to vehicle, EM-2 significantly increased food intake, throughout 24 h post-injection. Furthermore, EM-2 treatment led to a significant increase of DA and NE concentrations and a decrease of CRH mRNA levels. On the other hand, β-funaltrexamine administration reverted both feeding stimulatory and neuromodulatory effects induced by EM-2. We can conclude that the orexigenic effect of μ-opioid receptor activation by EM-2 could be related to both inhibition of CRH and stimulation of dopamine and norepinephrine levels, in the hypothalamus.
Keywords: Endomorphin-2; Feeding; Hypothalamus; Corticotrophin-releasing hormone; Dopamine; Norepinephrine;

Involvement of delta and mu opioid receptors in the acute and sensitized locomotor action of cocaine in mice by J.H. Kotlinska; E. Gibula-Bruzda; E. Witkowska; J. Izdebski (89-95).
Analogs of deltorphins, such as cyclo(Nδ, Nδ-carbonyl-d-Orn2, Orn4)deltorphin (DEL-6) and deltorphin II N-(ureidoethyl)amide (DK-4) are functional agonists predominantly for the delta opioid receptors (DOR) in the guinea-pig ileum and mouse vas deferens bioassays. The purpose of this study was to examine an influence of these peptides (5, 10 or 20 nmol, i.c.v.) on the acute cocaine-induced (10 mg/kg, i.p.) locomotor activity and the expression of sensitization to cocaine locomotor effect. Sensitization to locomotor effect of cocaine was developed by five injections of cocaine at the dose of 10 mg/kg, i.p. every 3 days. Our results indicated that DK-4 and DEL-6 differently affected the acute and sensitized cocaine locomotion. Co-administration of DEL-6 with cocaine enhanced acute cocaine locomotion only at the dose of 10 nmol, with minimal effects at the doses 5 and 20 nmol, whereas co-administration of DK-4 with cocaine enhanced acute cocaine-induced locomotion in a dose-dependent manner. Similarly to the acute effects, DEL-6 only at the dose of 10 nmol but DK-4 dose-dependently enhanced the expression of cocaine sensitization. Pre-treatment with DOR antagonist – naltrindole (5 nmol, i.c.v.) and mu opioid receptor (MOR) antagonist, β-funaltrexamine abolished the ability of both peptides to potentiate the effects of cocaine. Our study suggests that MOR and DOR are involved in the interactions between cocaine and both deltorphins analogs. A distinct dose–response effects of these peptides on cocaine locomotion probably arise from differential functional activation (targeting) of the DOR and MOR by both deltorphins analogs.
Keywords: Deltorphins analogs; Cocaine; Locomotor activity; Sensitization; Mice;

A mastoparan-derived peptide has broad-spectrum antiviral activity against enveloped viruses by Christopher J. Sample; Kathryn E. Hudak; Brice E. Barefoot; Matthew D. Koci; Moses S. Wanyonyi; Soman Abraham; Herman F. Staats; Elizabeth A. Ramsburg (96-105).
Broad-spectrum antiviral drugs are urgently needed to treat individuals infected with new and re-emerging viruses, or with viruses that have developed resistance to antiviral therapies. Mammalian natural host defense peptides (mNHP) are short, usually cationic, peptides that have direct antimicrobial activity, and which in some instances activate cell-mediated antiviral immune responses. Although mNHP have potent activity in vitro, efficacy trials in vivo of exogenously provided mNHP have been largely disappointing, and no mNHP are currently licensed for human use. Mastoparan is an invertebrate host defense peptide that penetrates lipid bilayers, and we reasoned that a mastoparan analog might interact with the lipid component of virus membranes and thereby reduce infectivity of enveloped viruses. Our objective was to determine whether mastoparan-derived peptide MP7-NH2 could inactivate viruses of multiple types, and whether it could stimulate cell-mediated antiviral activity. We found that MP7-NH2 potently inactivated a range of enveloped viruses. Consistent with our proposed mechanism of action, MP7-NH2 was not efficacious against a non-enveloped virus. Pre-treatment of cells with MP7-NH2 did not reduce the amount of virus recovered after infection, which suggested that the primary mechanism of action in vitro was direct inactivation of virus by MP7-NH2. These results demonstrate for the first time that a mastoparan derivative has broad-spectrum antiviral activity in vitro and suggest that further investigation of the antiviral properties of mastoparan peptides in vivo is warranted.
Keywords: Mastoparan; Antiviral; Host defense peptide;

Accumulating data implicate a pathological role for sympathetic neurotransmitters like neuropeptide Y (NPY) in breast cancer progression. Our group and others reported that NPY promotes proliferation and migration in breast cancer cells, however the angiogenic potential of NPY in breast cancer is unknown. Herein we sought to determine if NPY promotes angiogenesis in vitro by increasing vascular endothelial growth factor (VEGF) expression and release from 4T1 breast cancer cells. Western blot analysis revealed that NPY treatment caused a 52 ± 14% increase in VEGF expression in the 4T1 cells compared to non-treated controls. Using selective NPY Y-receptor agonists (Y1R, Y2R and Y5R) we observed an increase in VEGF expression only when cells were treated with Y5R agonist. Congruently, using selective Y1R, Y2R, or Y5R antagonists, NPY-induced increases in VEGF expression in 4T1 cells were attenuated only under Y5R antagonism. Endothelial tube formation assays were conducted using conditioned media (CM) from NPY treated 4T1 cells. Concentration-dependent increases in number of branch points and complete endothelial networks were observed in HUVEC exposed to NPY CM. CM from Y5R agonist treated 4T1 cells caused similar increases in number of branch points and complete endothelial networks. VEGF concentration was quantified in CM (ELISA) from agonist experiments; we observed a 2-fold and 2.5-fold increase in VEGF release from NPY and Y5R agonist treated 4T1 cells respectively. Overall these data highlight a novel mechanism by which NPY may promote breast cancer progression, and further implicate a pathological role of the NPY Y5R.
Keywords: NPY; Neuropeptide Y; 4T1, Mammary carcinoma; Breast cancer; Y1R; Y2R; Y5R; VEGF; Vascularization;

Release of biologically active kinin peptides, Met-Lys-bradykinin and Leu-Met-Lys-bradykinin from human kininogens by two major secreted aspartic proteases of Candida parapsilosis by Grazyna Bras; Oliwia Bochenska; Maria Rapala-Kozik; Ibeth Guevara-Lora; Alexander Faussner; Wojciech Kamysz; Andrzej Kozik (114-123).
In terms of infection incidence, the yeast Candida parapsilosis is the second after Candida albicans as causative agent of candidiases in humans. The major virulence factors of C. parapsilosis are secreted aspartic proteases (SAPPs) which help the pathogen to disseminate, acquire nutrients and dysregulate the mechanisms of innate immunity of the host. In the current work we characterized the action of two major extracellular proteases of C. parapsilosis, SAPP1 and SAPP2, on human kininogens, proteinaceous precursors of vasoactive and proinflammatory bradykinin-related peptides, collectively called the kinins. The kininogens, preferably the form with lower molecular mass, were effectively cleaved by SAPPs, with the release of two uncommon kinins, Met-Lys-bradykinin and Leu-Met-Lys-bradykinin. While optimal at acidic pH (4–5), the kinin release yield was only 2–3-fold lower at neutral pH. These peptides were able to interact with cellular kinin receptors of B2 subtype and to stimulate the human endothelial cells HMEC-1 to increased secretion of proinflammatory interleukins (ILs), IL-1β and IL-6. The analysis of the stability of SAPP-generated kinins in plasma suggested that they are biologically equivalent to bradykinin, the best agonist of B2 receptor subtype and can be quickly converted to des-Arg9-bradykinin, the agonist of inflammation-inducible B1 receptors.
Keywords: Candida parapsilosis; Candidiasis; Kallikrein–kinin system; Bradykinin receptors; Interleukins; Secreted aspartic proteases;

Proline rich-oligopeptides: Diverse mechanisms for antihypertensive action by Katia L.P. Morais; Danielle Ianzer; José Rodolfo R. Miranda; Robson L. Melo; Juliano R. Guerreiro; Robson A.S. Santos; Henning Ulrich; Claudiana Lameu (124-133).
Bradykinin-potentiating peptides from Bothrops jararaca (Bj) discovered in the early 1960s, were the first natural inhibitors of the angiotensin-converting enzyme (ACE). These peptides belong to a large family of snake venom proline-rich oligopeptides (PROs). One of these peptides, Bj-PRO-9a, was essential for defining ACE as effective drug target and development of captopril, an active site-directed inhibitor of ACE used worldwide for the treatment of human arterial hypertension. Recent experimental evidences demonstrated that cardiovascular effects exerted by different Bj-PROs are due to distinct mechanisms besides of ACE inhibition. In the present work, we have investigated the cardiovascular actions of four Bj-PROs, namely Bj-PRO-9a, -11e, -12b and -13a. Bj-PRO-9a acts upon ACE and BK activities to promote blood pressure reduction. Although the others Bj-PROs are also able to inhibit the ACE activity and to potentiate the BK effects, our results indicate that antihypertensive effect evoked by them involve new mechanisms. Bj-PRO-11e and Bj-PRO-12b involves induction of [Ca2+] i transients by so far unknown receptor proteins. Moreover, we have suggested argininosuccinate synthetase and M3 muscarinic receptor as targets for cardiovascular effects elicited by Bj-PRO-13a. In summary, the herein reported results provide evidence that Bj-PRO-mediated effects are not restricted to ACE inhibition or potentiation of BK-induced effects and suggest different actions for each peptide for promoting arterial pressure reduction. The present study reveals the complexity of the effects exerted by Bj-PROs for cardiovascular control, opening avenues for the better understanding of blood pressure regulation and for the development of novel therapeutic approaches.
Keywords: Proline-rich oligopeptides; Argininosuccinate synthetase; Muscarinic acetylcholine receptor; Nitric oxide; Mean arterial pressure; Heart rate;

Apelin stimulates both cholecystokinin and glucagon-like peptide 1 secretions in vitro and in vivo in rodents by Jean-Sébastien Wattez; Rozenn Ravallec; Benoit Cudennec; Claude Knauf; Pascal Dhulster; Philippe Valet; Christophe Breton; Didier Vieau; Jean Lesage (134-136).
Apelin is an enteric peptide that exerts several digestive functions such as stimulation of cell proliferation and cholecystokinin (CCK) secretion. We investigated using murine enteroendocrine cell line (STC-1) and rats if apelin-13 stimulates both CCK and glucagon-like peptide 1 (GLP-1) secretions. We demonstrated that, in vitro and in vivo, apelin-13 increases the release of these two hormones in a dose-dependent manner. Present data suggest that apelin may modulate digestive functions, food intake behavior and glucose homoeostasis via apelin-induced release of enteric CCK but also through a new incretin-releasing activity on enteric GLP-1.
Keywords: Apelin; Cholecystokinin; Glucagon-like peptide 1; STC-1 cells; Rat;

Effects of ghrelin on gastric distention sensitive neurons in the arcuate nucleus of hypothalamus and gastric motility in diabetic rats by Luo Xu; Zhuling Qu; Feifei Guo; Mingjie Pang; Shengli Gao; Hai Zhu; Fang Gu; Xiangrong Sun (137-146).
This study was performed to observe the effects of ghrelin on the activity of gastric distention (GD) sensitive neurons in the arcuate nucleus of hypothalamus (Arc) and on gastric motility in vivo in streptozocin (STZ) induced diabetes mellitus (DM) rats. Electrophysiological results showed that ghrelin could excite GD-excitatory (GD-E) neurons and inhibit GD-inhibitory (GD-I) neurons in the Arc. However, fewer GD-E neurons were excited by ghrelin and the excitatory effect of ghrelin on GD-E neurons was much weaker in DM rats. Gastric motility research in vivo showed that microinjection of ghrelin into the Arc could significantly promote gastric motility and it showed a dose-dependent manner. The effect of ghrelin promoting gastric motility in DM rats was weaker than that in normal rats. The effects induced by ghrelin could be blocked by growth hormone secretagogue receptor (GHSR) antagonist [d-Lys-3]-GHRP-6 or BIM28163. RIA and real-time PCR data showed that the levels of ghrelin in the plasma, stomach and ghrelin mRNA in the Arc increased at first but decreased later and the expression of GHSR-1a mRNA in the Arc maintained a low level in DM rats. The present findings indicate that ghrelin could regulate the activity of GD sensitive neurons and gastric motility via ghrelin receptors in the Arc. The reduced effects of promoting gastric motility induced by ghrelin could be connected with the decreased expression of ghrelin receptors in the Arc in diabetes. Our data provide new experimental evidence for the role of ghrelin in gastric motility disorder in diabetes.
Keywords: Arcuate nucleus of hypothalamus; Diabetes mellitus; Ghrelin; Gastric distention sensitive neurons; Gastric motility; Rats;

Antimicrobial activity and mechanism of action of a novel cationic α-helical octadecapeptide derived from heat shock protein 70 of rice by Masayuki Taniguchi; Atsuo Ikeda; Shun-ichi Nakamichi; Yohei Ishiyama; Eiichi Saitoh; Tetsuo Kato; Akihito Ochiai; Takaaki Tanaka (147-155).
Hsp70(241–258), an octadecapeptide derived from the heat shock protein 70 (Hsp70) of rice (Oryza sativa L. japonica), is a novel cationic α-helical antimicrobial peptide (AMP) that contains four lysine, two arginine, and two histidine residues. The antimicrobial activity of Hsp70(241–258) against Porphyromonas gingivalis, a periodontal pathogen, and Candida albicans, an opportunistic fungal pathogen, was quantitatively evaluated using a chemiluminescence method that measures ATP derived from viable cells. The 50% growth-inhibitory concentrations of Hsp70(241–258) against P. gingivalis and C. albicans cells were 63 μM and 70 μM, respectively. Hsp70(241–258) had little or no hemolytic activity even at 1 mM, and showed negligible cytotoxicity up to 300 μM. The degrees of calcein leakage from large unilamellar vesicles, which mimic the membranes of Gram-negative bacteria, and 3,3′-dipropylthiadicarbocyanine iodide release from P. gingivalis cells induced by the addition of Hsp70(241–258) increased in a concentration-dependent manner. When Hsp70(241–258) was added to calcein-acetoxymethyl ester-loaded C. albicans cells, calcein release from the cells increased in a concentration-dependent manner. Flow cytometric analysis also showed that the percentages of C. albicans cells stained with propidium iodide, a DNA-intercalating dye, increased as the concentration of Hsp70(241–258) added was increased. Therefore, Hsp70(241–258) appears to exhibit antimicrobial activity against P. gingivalis and C. albicans through membrane disruption. These results suggest that Hsp70(241–258) could be useful as a safe and potent AMP against P. gingivalis and C. albicans in many fields of health care, especially in the control of oral infections.
Keywords: Antimicrobial peptide; Cationic α-helical peptide; Porphyromonas gingivalis; Candida albicans; Membrane-active peptide;

Ghrelin protects heart against ERS-induced injury and apoptosis by activating AMP-activated protein kinase by Gai-Gai Zhang; Huai-Qiu Cai; Yan-Hui Li; Yu-Bin Sui; Jin-Sheng Zhang; Jin-Rui Chang; Ming Ning; Yang Wu; Chao-Shu Tang; Yong-Fen Qi; Xin-Hua Yin (156-165).
Ghrelin, the endogenous ligand of growth hormone secretagogue receptor (GHS-R), is a cardioprotective peptide. In our previous work, we have revealed that ghrelin could protect heart against ischemia/reperfusion (I/R) injury by inhibiting endoplasmic reticulum stress (ERS), which contributes to many heart diseases. In current study, using both in vivo and in vitro models, we investigated how ghrelin inhibits myocardial ERS. In the in vivo rat heart injury model induced by isoproterenol (ISO), we found that exogenous ghrelin could alleviate heart dysfunction, reduce myocardial injury and apoptosis and inhibit the excessive myocardial ERS induced by ISO. More importantly, the activation of AMP-activated protein kinase (AMPK) was observed. To explore the role of AMPK activation in ERS inhibition by ghrelin, we set up two in vitro ERS models by exposing cultured rat cardiomyocytes to tunicamycin(Tm) or dithiothreitol (DTT). In both models, compared with Tm or DTT treatment alone, pre-incubation cardiomyocytes with ghrelin significantly activated AMPK, reversed the upregulation of the ERS markers, C/EBP-homologous protein (CHOP) and cleaved caspase-12, and reduced apoptosis of cardiomyocytes. Further, we found that the ERS inhibitory and anti-apoptotic actions induced by ghrelin were blocked by an AMPK inhibitor. To investigate how ghrelin activates AMPK, selective antagonist of GHS-R1a and inhibitor of Ca2+/Calmodulin-dependent protein kinase kinase (CaMKK) were added, respectively, before ghrelin pre-incubation, and we found that AMPK activation was prevented and the ERS inhibitory and anti-apoptotic actions of ghrelin were blocked. In conclusion, ghrelin could protect heart against ERS-induced injury and apoptosis, at least partially through a GHS-R1a/CaMKK/AMPK pathway.
Keywords: Ghrelin; Heart; Endoplasmic reticulum stress; Apoptosis; AMP-activated protein kinase;