All posts in Raw-Peptide Journal (Elsevier)

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): J. Michael Conlon , Milena Mechkarska , Gordana Radosavljevic , Samir Attoub , Jay D. King , Miodrag L. Lukic , Stephen McClean

Peptidomic analysis of norepinephrine-stimulated skin secretions of the Orinoco lime tree frog Sphaenorhynchus lacteus (Hylidae, Hylinae) revealed the presence of three structurally related host-defense peptides with limited sequence similarity to frenatin 2 from Litoria infrafrenata (Hylidae, Pelodryadinae) and frenatin 2D from Discoglossus sardus (Alytidae). Frenatin 2.1S (GLVGTLLGHIGKAILG.NH2) and frenatin 2.2S (GLVGTLLGHIGKAILS.NH2) are C-terminally α-amidated but frenatin 2.3S (GLVGTLLGHIGKAILG) is not. Frenatin 2.1S and 2.2S show potent bactericidal activity against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MIC ≤16μM) but are less active against a range of Gram-negative bacteria. Frenatin 2.1S (LC50 =80±6μM) and 2.2S (LC50 =75±5μM) are cytotoxic against non-small cell lung adenocarcinoma A549 cells but are less hemolytic against human erythrocytes (LC50 =167±8μM for frenatin 2.1S and 169±7μM for 2.2S). Weak antimicrobial and cytotoxic potencies of frenatin 2.3S demonstrate the importance of C-terminal α-amidation for activity. Frenatin 2.1S and 2.2S significantly (P <0.05) increased production of proinflammatory cytokines IL-1β and IL-23 by lipopolysaccharide (LPS)-stimulated mouse peritoneal macrophages and frenatin 2.1S also enhanced production of TNF-α. Effects on IL-6 production were not significant. Frenatin 2.2S significantly downregulated production of the anti-inflammatory cytokine IL-10 by LPS-stimulated cells. The data support speculation that frenatins act on skin macrophages to produce a cytokine-mediated stimulation of the adaptive immune system in response to invasion by microorganisms. They may represent a template for the design of peptides with therapeutic applications as immunostimulatory agents.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Tie-Jiang Chen , Qing-Yang Fu , Wu-Quan Wu

High plasma levels of adrenomedullin have been associated with stroke severity and clinical outcomes. This study aimed to analyze plasma levels of adrenomedullin in traumatic brain injury and their association with prognosis. One hundred and forty-eight acute severe traumatic brain injury and 148 sex- and age-matched healthy controls were recruited in this study. Plasma adrenomedullin concentration was measured by enzyme-linked immunosorbent assay. Unfavorable outcome was defined as Glasgow Outcome Scale score of 1–3. Compared to controls, the patients had significantly higher plasma concentrations of adrenomedullin, which were also highly associated negatively with Glasgow Coma Scale score. Plasma adrenomedullin level was proved to be an independent predictor for 6-month mortality and unfavorable outcome of patients in a multivariate analysis. A receiver operating characteristic curve was configured to show that a baseline plasma adrenomedullin level predicted 6-month mortality and unfavorable outcome of patients with high area under curve. The predictive performance of the plasma adrenomedullin concentration was also similar to that of Glasgow Coma Scale score for the prediction of 6-month mortality and unfavorable outcome of patients. In a combined logistic-regression model, adrenomedullin improved the area under curve of Glasgow Coma Scale score for the prediction of 6-month mortality and unfavorable outcome of patients, but the differences did not appear to be statistically significant. Thus, high plasma levels of adrenomedullin are associated with head trauma severity, and may independently predict long-term clinical outcomes of traumatic brain injury.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Suleyman Aydin

Homeostasis of energy is regulated by genetic factors, food intake, and energy expenditure. When energy input is greater than expenditure, the balance is positive, which can lead to weight gain and obesity. When the balance is negative, weight is lost. Regulation of this homeostasis is multi-factorial, involving many orexigenic (appetite-stimulating) and anorexigenic (appetite-suppressing) peptide hormones. Peripheral tissues are now known to be involved in weight regulation and research on its endocrine characteristics proceeds apace. Preptin with 34 amino acids (MW 3948Da), adropin with 43 amino acids and a molecular weight of (4999Da), and irisin with 112 amino acids (12587Da), are three newly discovered peptides critical for regulating energy metabolism. Preptin is synthesized primarily in pancreatic beta cells, and adropin mainly in the liver and brain, and many peripheral tissues. Irisin, however, is synthesized principally in the heart muscle, along with peripheral tissues, including salivary glands, kidney and liver. The prime functions of preptin and adropin include regulating carbohydrate, lipid and protein metabolisms by moderating glucose-mediated insulin release. Irisin is an anti-obesitic and anti-diabetic hormone regulating adipose tissue metabolism and glucose homeostasis by converting white to brown adipose tissue. This review offers a historical account of these discovery and function of these peptides, including their structure, and physiological and biochemical properties. Their roles in energy regulation will be discussed. Their measurement in biological fluids will be considered, which will lead to further discussion of their possible clinical value.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Yun Wu , Lei Wang , Maojun Zhou , Xiuhua Jiang , Xiaoyan Zhu , Yu Chen , Shaonan Luo , Yuwen You , Zhenghua Ren , Anlong Xu

The conotoxin cysteine framework XV (-C-C-CC-C-C-C-C-), which was named Lt15a, was firstly identified from the cDNA library of Conus litteratus. After that, 18 new framework XV conotoxin sequences were cloned from nine Conus species. Like other conopeptides, the XV-conotoxins have the conserved signal peptide and propeptide, and there are also some conserved residues in their mature peptide. All the framework XV conotoxins were apparently converged into two branches, because of the indel and point mutations occurred in their mature peptides. By fused with thioredoxin and 6×His tag, six XV-conotoxins were successfully expressed in Escherichia coli and purified. Different framework XV conotoxins have distinct biological activities on mice and frogs, and that may be related to the diversity of the toxin sequences. All the six XV-conotoxins had no obvious effects on the sodium currents of DRG neuron cells of Sprague–Dawley (SD) rats. The identification of this framework of conotoxins enriches our understanding of the structural and functional diversity of conotoxin.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Xiang-Lin Chen , Bing-Jian Yu , Mao-Hua Chen

High plasma proenkephalin A level has been associated with ischemic stroke severity and clinical outcomes. This study aimed to assess the relationship between proenkephalin A and disease severity as well as to investigate its ability to predict long-term clinical outcome in patients with aneurysmal subarachnoid hemorrhage. Plasma proenkephalin A concentrations of one hundred and eighty patients and 180 sex- and age-matched healthy controls were measured by chemoluminescence sandwich immunoassay. Plasma proenkephalin A level was substantially higher in patients than in healthy controls (205.5±41.6pmol/L vs. 90.8±21.1pmol/L, P <0.001), was highly associated with World Federation of Neurological Surgeons (WFNS) score (r =0.470, P <0.001) and Fisher score (r =0.488, P <0.001), was an independent predictor for 6-month mortality [odds ratio (OR), 1.183; 95% confidence interval (CI), 1.067–1.339; P =0.004] and unfavorable outcome (Glasgow Outcome Scale score of 1–3) (OR, 1.119; 95% CI, 1.046–1.332; P =0.005) using multivariate analysis, and had high area under receiver operating characteristic curve (AUC) for prediction of 6-month mortality (AUC, 0.831; 95% CI, 0.768–0.883) and unfavorable outcome (AUC, 0.821; 95% CI, 0.757–0.874). The predictive value of the plasma proenkephalin A concentration was also similar to those of WFNS score and Fisher score (both P >0.05). In a combined logistic-regression model, proenkephalin A improved the AUCs of WFNS score and Fisher score, but the differences were not significant (both P >0.05). Thus, proenkephalin A level may be a useful, complementary tool to predict mortality and functional outcome at 6 months after aneurysmal subarachnoid hemorrhage.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Hélène Volkoff

cDNAs encoding the appetite regulating peptides apelin, cocaine and amphetamine regulated transcript (CART), cholecystokinin (CCK), peptide YY (PYY) and orexin were isolated in red-bellied piranha and their mRNA tissue and brain distributions examined. When compared to other fish, the sequences obtained for all peptides were most similar to that of other Characiforme fish, as well as to Cypriniformes. All peptides were widely expressed within the brain and in several peripheral tissues, including gastrointestinal tract. In order to assess the role of these peptides in the regulation of feeding of red-bellied piranha, we compared the brain mRNA expression levels of these peptides, as well as the gut mRNA expression of CCK and PYY, between fed and 7-day fasted fish. Within the brain, fasting induced a significant increase in both apelin and orexin mRNA expressions and a decrease in CART mRNA expression, but there where were no significant differences for either PYY or CCK brain mRNA expressions between fed and fasted fish. Within the intestine, PYY mRNA expression was lower in fasted fish compared to fed fish but there was no significant difference for CCK intestine mRNA expression between fed and fasted fish. Our results suggest that these peptides, perhaps with the exception of CCK, play a major role in the regulation of feeding of red-bellied piranha.

Publication date: June 2014 Source:Peptides, Volume 56

Author(s): Elaine F. Toniolo , Estêfani T. Maique , Wilson A. Ferreira Jr. , Andrea S. Heimann , Emer S. Ferro , Dinah L. Ramos-Ortolaza , Lydia Miller , Lakshmi A. Devi , Camila S. Dale

Direct-acting cannabinoid receptor ligands are well known to reduce hyperalgesic responses after nerve injury, although their psychoactive side effects have damped enthusiasm for their therapeutic development. Hemopressin (Hp) is a nonapeptide that selectively binds CB1 cannabinoid receptors (CB1 receptors) and exerts antinociceptive action in inflammatory pain models. We investigated the effect of Hp on neuropathic pain in rats subjected to chronic constriction injury (CCI) of the sciatic nerve, and explored the mechanisms involved. Oral administration of Hp inhibits mechanical hyperalgesia of CCI-rats up to 6h. Hp treatment also decreases Egr-1 immunoreactivity (Egr-1Ir) in the superficial layer of the dorsal horn of the spinal cord of CCI rats. The antinociceptive effect of Hp seems to be independent of inhibitory descending pain pathway since methysergide (5HT1A receptor antagonist) and yohimbine (α-2 adrenergic receptor antagonist) were unable to prevent Hp antinociceptive effect. Hp decreased calcium flux on DRG neurons from CCI rats, similarly to that observed for AM251, a CB1 receptor antagonist. We also investigated the effect of Hp on potassium channels of CCI rats using UCL 1684 (a blocker of Ca²⁺-activated K⁺ channels) which reversed Hp-induced antinociception. Furthermore, concomitant administration of URB-584 (FAAH inhibitor) but not JZL-184 (MAGL inhibitor) potentiates antinociceptive effect of Hp in CCI rats indicating an involvement of anadamide on HP-induced antinociception. Together, these data demonstrate that Hp displays antinociception in pain from neuropathic etiology through local effects. The release of anandamide and the opening of peripheral K⁺ channels are involved in the antinociceptive effect.

Publication date: Available online 18 May 2014 Source:Peptides

Author(s): Cabiati Manuela , Sabatino Laura , Svezia Benedetta , Caruso Raffaele , Verde Alessandro , Caselli Chiara , Prescimone Tommaso , Giannessi Daniela , D.R. Silvia

Publication date: May 2014 Source:Peptides, Volume 55

Author(s): William F. Porto , Diego O. Nolasco , Octavio L. Franco

Glycine-rich proteins (GRPs) derived from plants compose a family of proteins and peptides that share a glycine repeat domain and they can perform diverse functions. Two structural conformations have been proposed for GRPs: glycine loops arranged as a Velcro and an anti-parallel β-sheet with several β-strands. The antimicrobial peptide Pg-AMP1 is the only plant GRP with antibacterial activity reported so far and its structure remains unclear. Recently, its recombinant expression was reported, where the recombinant peptide had an additional methionine residue at the N-terminal and a histidine tag at the C-terminal (His6-tag). These changes seem to change the peptide's activity, generating a broader spectrum of antibacterial activity. In this report, through ab initio molecular modelling and molecular dynamics, it was observed that both native and recombinant peptide structures were composed of an N-terminal α-helix and a dynamic loop that represents two-thirds of the protein. In contrast to previous reports, it was observed that there is a tendency to adopt a globular fold instead of an extended one, which could be in both, glycine loops or anti-parallel β-sheet conformation. The recombinant peptide showed a slightly higher solvated potential energy compared to the native form, which could be related to the His6-tag exposition. In fact, the His6-tag could be mainly responsible for the broader spectrum of activity, but it does not seem to cause great structural changes. However, novel studies are needed for a better characterization of its pharmacological properties so that in the future novel drugs may be produced based on this peptide.

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Publication date: Available online 30 April 2014 Source:Peptides

Author(s): Samad Mussa Farkhani , Alireza Valizadeh , Hadi Karami , Samane Mohammadi , Nasrin Sohrabi , Fariba Badrzadeh

Efficient delivery of therapeutic and diagnostic molecules to the cells and tissues is a difficult challenge. The cellular membrane is very effective in its role as a selectively permeable barrier. While it is essential for cell survival and function, also presents a major barrier for intracellular delivery of cargo such as therapeutic and diagnostic agents. In recent years, cell-penetrating peptides (CPPs), that are relatively short cationic and/or amphipathic peptides, received great attention as efficient cellular delivery vectors due to their intrinsic ability to enter cells and mediate uptake of a wide range of macromolecular cargo such as plasmid DNA (pDNA), small interfering RNA (siRNAs), drugs, and nanoparticulate pharmaceutical carriers. This review discusses the various uptake mechanisms of these peptides. Furthermore, we discuss recent advances in the use of CPP for the efficient delivery of nanoparticles, nanocarriers, DNA, siRNA, and anticancer drugs to the cells. In addition, we have been highlighting new results for improving endosomal escape of CPP-cargo molecules. Finally, pH-responsive and activable CPPs for tumor-targeting therapy have been described.

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