Opioid peptides derived from hemoglobin: hemorphins

Bioactivities generated from meat proteins by enzymatic hydrolysis and the Maillard reaction

Bioactive peptides are released from meat proteins by enzymatic hydrolysis (i.e., gastrointestinal digestion, aging/storage, fermentation, and protease treatment). Such peptides attribute physiological functions to meat and meat products and are promising food ingredients for developing functional foods. Meat by-products (e.g., blood and collagen) are also good sources for generating bioactive peptides, since they are produced in large quantities and are rich in proteins. Although protein-derived bioactive peptides are attractive ingredients, their changes by the Maillard reaction during processing, cooking, and storage should be investigated. This article briefly reviews the production of bioactive peptides from meat and meat by-products. Such diverse peptides affects circulatory, nervous, alimentary, and immune systems. Then, the bioactivities of Maillard reaction products (MRPs) generated from protein hydrolysates are discussed. Special attention is paid to bioactivities of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) inhalation. As such activities, we have evaluated the impact of DMHF on blood pressure, moods, brainwaves, and dietary intake. Our efforts for understanding various aspects and implication of peptides and MRPs from meat proteins would open new avenues in the meat and food industry.

Hemorphins Targeting G Protein-Coupled Receptors

Hemorphins are short peptides produced by the proteolysis of the beta subunit of hemoglobin. These peptides have diverse physiological effects especially in the nervous and the renin-angiotensin systems. Such effects occur through the modulation of a diverse range of proteins including enzymes and receptors. In this review, we focus on pharmacological and functional targeting of G protein-coupled receptors (GPCRs) by hemorphins and their implication in physiology and pathophysiology. Among GPCRs, the opioid receptors constitute the first set of targets of hemorphins with implication in analgesia. Subsequently, several other GPCRs have been reported to be directly or indirectly involved in hemorphins’ action. This includes the receptors for angiotensin II, oxytocin, bombesin, and bradykinin, as well as the human MAS-related G protein-coupled receptor X1. Interestingly, both orthosteric activation and allosteric modulation of GPCRs by hemorphins have been reported. This review links hemorphins with GPCR pharmacology and signaling, supporting the implication of GPCRs in hemorphins’ effects. Thus, this aids a better understanding of the molecular basis of the action of hemorphins and further demonstrates that hemorphin-GPCR axis constitutes a valid target for therapeutic intervention in different systems.

Hemoglobin-derived peptides and mood regulation

Evidence accumulated over the past decades has revealed that red blood cells and hemoglobin (Hb) in the blood play important roles in modulating moods and emotions. The number of red blood cells affects the mood. Hb is the principal content in the red blood cells besides water. Denatured Hb is hydrolyzed to produce bioactive peptides. RVD-hemopressin α (RVD-Hpα), which is a fragment of α-chain (95-103) in Hb, functions as a negative allosteric modulator of cannabinoid receptor 1 and a positive allosteric modulator of cannabinoid receptor 2. Hemorphins, which are fragments of β-chain in Hb, exert their effects on opioid receptors. Two hemorphins, namely, LVV-hemorphin-6 and LVV-hemorphin-7, could induce anxiolytic-like effects. The use of Hb-derived bioactive peptides for the treatment of mood disorders is desirable due to cannabinoid-opioid cross modulation and the critical roles of the two systems in physiological processes, such as memory, mood and emotion.

Effect of Preparation Method on the Protein Profile of Equine Amnion Dressings

The protein content of amnion is thought to be the primary contributor to its efficacy as a biological dressing for wounds. Protein elution into antibiotic processing media has been reported, but the effect of antiseptic-based processing methods is unknown. Amniotic membranes were collected from eight healthy mares. Samples were collected after removal of gross debris. Tissues were subsequently divided and processed with either 0.05% chlorhexidine or 2% iodine/0.25% acetic acid. After protein extraction and trypsin digestion, the proteins were labeled with 8-plex iTRAQ tags, combined, and analyzed by high-resolution liquid chromatography-mass spectrometry. The MaxQuant-Perseus software suite was used to identify and quantify sample proteins, with functional annotation performed in PANTHER. There were 220 unique proteins identified, of which 144 were found in all individuals and across all conditions, several with a known role in wound healing. Contrary to expectations, processing did not significantly alter the protein content of the amnion tissue. Limitations include the small sample size and single time point. These results suggest that either processing method is acceptable for use in the preparation of equine amnion dressings. The role of expressed proteins in the biological activity of amnion dressings remains to be elucidated.

A putative antimicrobial peptide from Hymenoptera in the megaplasmid pSCL4 of Streptomyces clavuligerus ATCC 27064 reveals a singular case of horizontal gene transfer with potential applications

Streptomyces clavuligerus is a Gram-positive bacterium that is a high producer of secondary metabolites with industrial applications. The production of antibiotics such as clavulanic acid or cephamycin has been extensively studied in this species; nevertheless, other aspects, such as evolution or ecology, have received less attention. Furthermore, genes that arise from ancient events of lateral transfer have been demonstrated to be implicated in important functions of host species. This approximation discovered relevant genes that genomic analyses overlooked. Thus, we studied the impact of horizontal gene transfer in the S. clavuligerus genome. To perform this task, we applied whole-genome analysis to identify a laterally transferred sequence from different domains. The most relevant result was a putative antimicrobial peptide (AMP) with a clear origin in the Hymenoptera order of insects. Next, we determined that two copies of these genes were present in the megaplasmid pSCL4 but absent in the S. clavuligerus ATCC 27064 chromosome. Additionally, we found that these sequences were exclusive to the ATCC 27064 strain (and so were not present in any other bacteria) and we also verified the expression of the genes using RNAseq data. Next, we used several AMP predictors to validate the original annotation extracted from Hymenoptera sequences and explored the possibility that these proteins had post-translational modifications using peptidase cleavage prediction. We suggest that Hymenoptera AMP-like proteins of S. clavuligerus ATCC 27064 may be useful for both species adaptation and as an antimicrobial molecule with industrial applications.

Cryptides: latent peptides everywhere

Proteomic surveys with top-down platforms are today revealing thousands of naturally occurring fragments of bigger proteins. Some of them have not functional meaning because they derive from pathways responsible for protein degradation, but many have specific functions, often completely different from that one of the parent proteins. These peptides encrypted in the protein sequence are nowadays called cryptides. They are frequent in the animal and plant kingdoms and represent a new interesting -omic field of investigation. To point out how much widespread is their presence, we describe here the most studied cryptides from very common sources such as serum albumin, immunoglobulins, hemoglobin, and from saliva and milk proteins. Given its vastness, it is unfeasible to cover the topic exhaustively, therefore only several selected examples of cryptides from other sources are thereafter reported. Demanding is the development of new -omic platforms for the functional screening of new cryptides, which could provide suggestion for peptides and peptido-mimetics with variegate fields of application.

Food-Derived Hemorphins Cross Intestinal and Blood-Brain Barriers In Vitro

A qualitative study is presented, where the main question was whether food-derived hemorphins, i.e., originating from digested alimentary hemoglobin, could pass the intestinal barrier and/or the blood-brain barrier (BBB). Once absorbed, hemorphins are opioid receptor (OR) ligands that may interact with peripheral and central OR and have effects on food intake and energy balance regulation. LLVV-YPWT (LLVV-H4), LVV-H4, VV-H4, VV-YPWTQRF (VV-H7), and VV-H7 hemorphins that were previously identified in the 120 min digest resulting from the simulated gastrointestinal digestion of hemoglobin have been synthesized to be tested in in vitro models of passage of IB and BBB. LC-MS/MS analyses yielded that all hemorphins, except the LLVV-H4 sequence, were able to cross intact the human intestinal epithelium model with Caco-2 cells within 5-60 min when applied at 5 mM. Moreover, all hemorphins crossed intact the human BBB model with brain-like endothelial cells (BLEC) within 30 min when applied at 100 µM. Fragments of these hemorphins were also detected, especially the YPWT common tetrapeptide that retains OR-binding capacity. A cAMP assay performed in Caco-2 cells indicates that tested hemorphins behave as OR agonists in these cells by reducing cAMP production. We further provide preliminary results regarding the effects of hemorphins on tight junction proteins, specifically here the claudin-4 that is involved in paracellular permeability. All hemorphins at 100 µM, except the LLVV-H4 peptide, significantly decreased claudin-4 mRNA levels in the Caco-2 intestinal model. This in vitro study is a first step toward demonstrating food-derived hemorphins bioavailability which is in line with the growing body of evidence supporting physiological functions for food-derived peptides.

Utilization of blood by-products: An in silico and experimental combined study for BSA usage

In order to exploit industrial discards, protein enzymatic hydrolysis is a currently popular methodology for obtaining bioactive peptides. However, once released, most promising peptides have to be selected from the mixture. In this work, the suitability of pepsin (EC 3.4.23.1) to hydrolyse serum albumin in order to obtain bioactive peptides was assessed. Then, a suitable process to obtain best separation of bioactive peptides was evaluated, using polyethersulfone membranes at different pH values. Serum albumin was easily hydrolysed by pepsin, reaching a DH value of the 65.64 ± 1.57% of the maximum possible. A 23.25% of the identified peptides possessed high bioactivity scores (greater than 0.5), and one of them had reported bioactivity (LLL). Charge mechanisms always predominated over the sieve effect, and best transmission was accomplished at pH values close to the peptides isoelectric points. Basic and neutral peptides with the highest scores were always the most transmitted. Membrane material had greater influence than NMWCO in determining peptide transmission. In order to obtain purified fractions rich in peptides with high bioactivity scores from serum albumin, polyethersulfone membranes (applicable to industrial scale) of 5 kDa MWCO should be used at basic pH values after pepsin digestion.

Unsupervised Network Analysis of the Plastic Supraoptic Nucleus Transcriptome Predicts Caprin2 Regulatory Interactions

The supraoptic nucleus (SON) is a group of neurons in the hypothalamus responsible for the synthesis and secretion of the peptide hormones vasopressin and oxytocin. Following physiological cues, such as dehydration, salt-loading and lactation, the SON undergoes a function related plasticity that we have previously described in the rat at the transcriptome level. Using the unsupervised graphical lasso (Glasso) algorithm, we reconstructed a putative network from 500 plastic SON genes in which genes are the nodes and the edges are the inferred interactions. The most active nodal gene identified within the network was Caprin2. Caprin2 encodes an RNA-binding protein that we have previously shown to be vital for the functioning of osmoregulatory neuroendocrine neurons in the SON of the rat hypothalamus. To test the validity of the Glasso network, we either overexpressed or knocked down Caprin2 transcripts in differentiated rat pheochromocytoma PC12 cells and showed that these manipulations had significant opposite effects on the levels of putative target mRNAs. These studies suggest that the predicative power of the Glasso algorithm within an in vivo system is accurate, and identifies biological targets that may be important to the functional plasticity of the SON.

Chronic administration of nandrolone increases susceptibility to morphine dependence without correlation with LVV-hemorphin 7 in rats

LVV-hemorphin 7 (LVVYPWTQRF; LVV-H7), an N-terminal fragment of the β-chain of hemoglobin cleaved by cathepsin D/pepsin, is an atypical endogenous opioid peptide that is found in high concentration in blood. LVV-H7 acts as a μ-opioid agonist and an inhibitor of insulin-regulated aminopeptidase. Subchronic administration of anabolic androgenic steroids (AAS) has been clinically proven to induce the synthesis of erythrocytes and increase hemoglobin concentrations. Patients with a history of AAS abuse are more susceptible to opioid abuse. We hypothesized that this association could be at least partially attributed to the sensitization of the mesocorticolimbic dopaminergic pathway by LVV-H7. Using the conditioned place preference test and neurochemical analysis, we investigated the possible mechanism underlying the effect of chronic nandrolone administration on morphine-induced reward and its correlation with LVV-H7 in rats. Either LVV-H7 may not sensitize the rewarding neural circuits or its inhibition on locomotor activity could mask reward-related behaviors. Chronic nandrolone pretreatment indeed caused a significant reward by low dose morphine, which did not cause any reward in control rats. However, coadministration of anti-LVV-H7 antiserum with nandrolone did not block this effect. This may rule out the possibility of the involvement of LVV-H7 in the action of nandrolone to intensify morphine-induced reward. Moreover, the serum level of LVV-H7 was mildly increased in response to chronic nandrolone administration in our animal model. According to the current clinical observations, we may conclude that the chronic administration of nandrolone can increase susceptibility to morphine dependence, but that this effect is not related to elevated LVV-H7.

New insights into meat by-product utilization

Meat industry generates large volumes of by-products like blood, bones, meat trimmings, skin, fatty tissues, horns, hoofs, feet, skull and viscera among others that are costly to be treated and disposed ecologically. These costs can be balanced through innovation to generate added value products that increase its profitability. Rendering results in feed ingredients for livestock, poultry and aquaculture as well as for pet foods. Energy valorization can be obtained through the thermochemical processing of meat and bone meal or the use of waste animal fats for the production of biodiesel. More recently, new applications have been reported like the production of polyhydroxyalkanoates as alternative to plastics produced from petroleum. Other interesting valorization strategies are based on the hydrolysis of by-products to obtain added value products like bioactive peptides with relevant physiological effects as antihypertensive, antioxidant, antidiabetic, antimicrobial, etc. with promising applications in the food, pharmaceutical and cosmetics industry. This paper reports and discusses the latest developments and trends in the use and valorisation of meat industry by-products.

Production of bioactive peptide hydrolysates from deer, sheep, pig and cattle red blood cell fractions using plant and fungal protease preparations

Protease preparations from plant (papain and bromelain) and fungal (FP400 and FPII) sources were used to hydrolyze the red blood cell fractions (RBCFs) separated from deer, sheep, pig, and cattle abattoir-sourced blood. After 1, 2, 4 and 24h of hydrolysis, the antioxidant and antibacterial activities of the peptide hydrolysates obtained were investigated. The increase in trichloroacetic acid-soluble peptides over the hydrolysis period was examined using the o-phthaldialdehyde (OPA) assay and the hydrolysis profiles were illustrated using SDS-PAGE. Papain generated RBCF hydrolysates exhibited higher ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) compared to those generated with bromelain, FP400 and FPII. At certain concentrations, 24h hydrolysates of RBCF using FP400 and FPII were able to inhibit the growth of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The results indicated that the use of proteases from plant or fungal sources can produce animal blood hydrolysates with antioxidant and antimicrobial activities.

Trans-Modulation of the Somatostatin Type 2A Receptor Trafficking by Insulin-Regulated Aminopeptidase Decreases Limbic Seizures

Within the hippocampus, the major somatostatin (SRIF) receptor subtype, the sst2A receptor, is localized at postsynaptic sites of the principal neurons where it modulates neuronal activity. Following agonist exposure, this receptor rapidly internalizes and recycles slowly through the trans-Golgi network. In epilepsy, a high and chronic release of somatostatin occurs, which provokes, in both rat and human tissue, a decrease in the density of this inhibitory receptor at the cell surface. The insulin-regulated aminopeptidase (IRAP) is involved in vesicular trafficking and shares common regional distribution with the sst2A receptor. In addition, IRAP ligands display anticonvulsive properties. We therefore sought to assess by in vitro and in vivo experiments in hippocampal rat tissue whether IRAP ligands could regulate the trafficking of the sst2A receptor and, consequently, modulate limbic seizures. Using pharmacological and cell biological approaches, we demonstrate that IRAP ligands accelerate the recycling of the sst2A receptor that has internalized in neurons in vitro or in vivo. Most importantly, because IRAP ligands increase the density of this inhibitory receptor at the plasma membrane, they also potentiate the neuropeptide SRIF inhibitory effects on seizure activity. Our results further demonstrate that IRAP is a therapeutic target for the treatment of limbic seizures and possibly for other neurological conditions in which downregulation of G-protein-coupled receptors occurs.

SIGNIFICANCE STATEMENT

The somatostatin type 2A receptor (sst2A) is localized on principal hippocampal neurons and displays anticonvulsant properties. Following agonist exposure, however, this receptor rapidly internalizes and recycles slowly. The insulin-regulated aminopeptidase (IRAP) is involved in vesicular trafficking and shares common regional distribution with the sst2A receptor. We therefore assessed by in vitro and in vivo experiments whether IRAP could regulate the trafficking of this receptor. We demonstrate that IRAP ligands accelerate sst2A recycling in hippocampal neurons. Because IRAP ligands increase the density of sst2A receptors at the plasma membrane, they also potentiate the effects of this inhibitory receptor on seizure activity. Our results further demonstrate that IRAP is a therapeutic target for the treatment of limbic seizures.

Are intact peptides absorbed from the healthy gut in the adult human?

For over 100 years it was believed that dietary protein must be completely hydrolysed before its constituent amino acids could be absorbed via specific amino acid transport systems. It is now known that the uptake of di- and tripeptides into the enterocyte is considerable, being transported across the intestinal endothelium by the PepT1 H+/peptide co-transporter. There is also evidence that some di- and tripeptides may survive cytosolic hydrolysis and be transported intact across the basolateral membrane. However, other than antigen sampling, the transport of larger intact macromolecules across the intestinal endothelium of the healthy adult human remains a controversial issue as there is little unequivocal in vivo evidence to support this postulation. The aim of the present review was to critically evaluate the scientific evidence that peptides/proteins are absorbed by healthy intestinal epithelia and pass intact into the hepatic portal system. The question of the absorption of oliogopeptides is paramount to the emerging science of food-derived bioactive peptides, their mode of action and physiological effects. Overall, we conclude that there is little unequivocal evidence that dietary bioactive peptides, other than di- and tripeptides, can cross the gut wall intact and enter the hepatic portal system in physiologically relevant concentrations.

Bioactive peptides of animal origin: a review

Bioactive peptides are specific protein fragments which, above and beyond their nutritional capabilities, have a positive impact on the body's function or condition which may ultimately influence health. Although, inactive within the sequence of the parent proteins, these peptides can be released during proteolysis or fermentation and play an important role in human health by affecting the digestive, endocrine, cardiovascular, immune and nervous systems. Several peptides that are released in vitro or in vivo from animal proteins have been attributed to different health effects, including antimicrobial properties, blood pressure-lowering (ACE inhibitory) effects, cholesterol-lowering ability, antithrombotic and antioxidant activities, opioid activities, enhancement of mineral absorption and/or bioavailability, cytomodulatory and immunomodulatory effects, antiobesity, and anti-genotoxic activity. Several functional foods based on the bioactivities of these peptides with scientifically evidenced health claims are already on the market or under development by food companies. Consumer's increasing interest in these products has given an impetus to the food industry and scientific sector who are continuously exploring the possibilities for the development of new functional products based on these peptides. In this review, we describe above stated properties of bioactive peptides of animal origin.

Effects of porcine hemoglobin on serum lipid content and fecal lipid excretion in rats

The purpose of this study was to elucidate the effects of dietary hemoglobin on serum and liver lipid contents in rats, and the ability of hemoglobin hydrolysates to disrupt lipid absorption. After rats had been fed on casein- or porcine hemoglobin-containing diets for 4 weeks, their serum and liver lipid contents and fecal cholesterol, bile acid, and nitrogen excretion were measured. To elucidate the mechanism of lipid absorption by dietary hemoglobin, we also examined lipase activity, micellar solubility of cholesterol, and bile acid binding activity in the presence of hemoglobin hydrolysates. Dietary hemoglobin decreased serum and liver triglyceride and cholesterol contents and increased fecal fatty acid, cholesterol, and bile acid excretion. In addition, hemoglobin hydrolysates inhibited lipase activity compared with casein hydrolysates in an in vitro study. These results suggested that the hypolipidemic effect of hemoglobin is mediated by increased fecal lipid excretion, and that decreased lipase activity by hemoglobin is at least partially responsible for this result. The observed effects were documented with an 8 g/kg hemoglobin diet, which is lower than in other studies; therefore. hemoglobin may be useful in the prevention of lifestyle-related diseases.

Probing protein sequences as sources for encrypted antimicrobial peptides

Starting from the premise that a wealth of potentially biologically active peptides may lurk within proteins, we describe here a methodology to identify putative antimicrobial peptides encrypted in protein sequences. Candidate peptides were identified using a new screening procedure based on physicochemical criteria to reveal matching peptides within protein databases. Fifteen such peptides, along with a range of natural antimicrobial peptides, were examined using DSC and CD to characterize their interaction with phospholipid membranes. Principal component analysis of DSC data shows that the investigated peptides group according to their effects on the main phase transition of phospholipid vesicles, and that these effects correlate both to antimicrobial activity and to the changes in peptide secondary structure. Consequently, we have been able to identify novel antimicrobial peptides from larger proteins not hitherto associated with such activity, mimicking endogenous and/or exogenous microorganism enzymatic processing of parent proteins to smaller bioactive molecules. A biotechnological application for this methodology is explored. Soybean (Glycine max) plants, transformed to include a putative antimicrobial protein fragment encoded in its own genome were tested for tolerance against Phakopsora pachyrhizi, the causative agent of the Asian soybean rust. This procedure may represent an inventive alternative to the transgenic technology, since the genetic material to be used belongs to the host organism and not to exogenous sources.

Development and validation of a capillary electrophoresis tandem mass spectrometry analytical method for the determination of Leu-Val-Val- and Val-Val-hemorphin-7 peptides in cerebrospinal fluid

A CE-tandem MS method was optimised and validated for selective and specific determination of LVV- and VV-hemorphin-7 peptides in cerebrospinal fluid. These two small peptides originate from haemoglobin beta chains. They possess relevant biological activity and recently a potential biomarker role in posterior cranial fossa paediatric brain tumour disease was evidenced. The separation was optimised using formic acid as background electrolyte and a water/methanol mixture, containing 0.1% (v/v) formic acid, as sheath liquid. The two peptides, differing in only one amino acid of the sequence at the N-terminal side were baseline separated in less than 15 min. The method allowed a very reduced and rapid sample pretreatment and was successfully applied to hemorphins determination in patient samples without matrix interferences. The method successfully passed bioanalytical validation showing linearity, accuracy and precision data on cerebrospinal fluid matrix within the acceptable values. The analysis of cerebrospinal fluid of patients affected by different posterior cranial fossa tumour forms confirmed our previous findings showing the absence of hemorphins in the pre-surgical cerebrospinal fluid and their presence in the post-ones and controls. The present method saves costs and time due to capillary electrophoresis miniaturisation and to the absence of chromatographic column and gradient elution and allows numerous injections per sample starting from few microlitres of cerebrospinal fluid.

Hemopressin and other bioactive peptides from cytosolic proteins: are these non-classical neuropeptides?

Peptides perform many roles in cell-cell signaling; examples include neuropeptides, hormones, and growth factors. Although the vast majority of known neuropeptides are produced in the secretory pathway, a number of bioactive peptides are derived from cytosolic proteins. For example, the hemopressins are a family of peptides derived from alpha and beta hemoglobin which bind to the CB1 cannabinoid receptor, functioning as agonists or antagonists/inverse agonists depending on the size of the peptide. However, the finding that peptides derived from cytosolic proteins can affect receptors does not prove that these peptides are true endogenous signaling molecules. In order for the hemopressins and other peptides derived from cytosolic proteins to be considered neuropeptide-like signaling molecules, they must be synthesized in brain, they must be secreted in levels sufficient to produce effects, and either their synthesis or secretion should be regulated. If these criteria are met, we propose the name "non-classical neuropeptide" for this category of cytosolic bioactive peptide. This would be analogous to the non-classical neurotransmitters, such as nitric oxide and anandamide, which are not stored in secretory vesicles and released upon stimulation but are synthesized upon stimulation and constitutively released. We review some examples of cytosolic peptides from various protein precursors, describe potential mechanisms of their biosynthesis and secretion, and discuss the possibility that these peptides are signaling molecules in the brain, focusing on the criteria that these peptides would have to fill in order to be considered non-classical neuropeptides.

Hemopressins and other hemoglobin-derived peptides in mouse brain: comparison between brain, blood, and heart peptidome and regulation in Cpefat/fat mice

Many hemoglobin-derived peptides are present in mouse brain, and several of these have bioactive properties including the hemopressins, a related series of peptides that bind to cannabinoid CB1 receptors. Although hemoglobin is a major component of red blood cells, it is also present in neurons and glia. To examine whether the hemoglobin-derived peptides in brain are similar to those present in blood and heart, we used a peptidomics approach involving mass spectrometry. Many hemoglobin-derived peptides are found only in brain and not in blood, whereas all hemoglobin-derived peptides found in heart were also seen in blood. Thus, it is likely that the majority of the hemoglobin-derived peptides detected in brain are produced from brain hemoglobin and not erythrocytes. We also examined if the hemopressins and other major hemoglobin-derived peptides were regulated in the Cpe(fat/fat) mouse; previously these mice were reported to have elevated levels of several hemoglobin-derived peptides. Many, but not all of the hemoglobin-derived peptides were elevated in several brain regions of the Cpe(fat/fat) mouse. Taken together, these findings suggest that the post-translational processing of alpha and beta hemoglobin into the hemopressins, as well as other peptides, is up-regulated in some but not all Cpe(fat/fat) mouse brain regions.

Hemorphins act as homeostatic agents in response to endotoxin-induced stress

The effect of synthetic LVV-hemorphin-7 and hemorphin-7 on hypothalamo-pituitary-adrenocortical axis activity in response to endotoxin-induced stress was studied. The intraperitoneal (ip) endotoxin (lipopolysaccaride, LPS) (0.5 mg/kg) administration in combination with hemorphin (1 mg/kg) induce significant decrease in plasma corticosterone and modest decrease in plasma levels of tumor necrosis factor-alpha (TNFalpha) in compare with elevated levels of both corticosterone and TNFalpha in plasma of rats received LPS administration alone. Increased activity of calcineurin in both plasma and brain of rats received ip administration of LPS, was recovered under LPS + hemorphin treatment. In two independent proteome analysis, using 2-dimensional fluorescence difference gel electrophoresis and the isotope coded protein label technology, peptidyl-prolyl cis-trans-isomerase A (cyclophilin A) was identified as regulated by hemorphins protein in mouse brain. A therapeutic potential of hemorphins and mechanisms of their homeostatic action in response to endotoxin-induced stress are discussed.

Significant lower VVH7-like immunoreactivity serum level in diabetic patients: evidence for independence from metabolic control and three key enzymes in hemorphin metabolism, cathepsin D, ACE and DPP-IV

Low circulating VVH7-like immunoreactivity (VVH7 i.r) level was amazingly observed in human diabetic sera. Here, we examined the impact of diabetes type, clinico-biological features and metabolic control on circulating VVH7 i.r level in this disease. ELISA test was used to measure VVH7 i.r in sera of 120 diabetic patients (type 1 diabetes in 64, type 2 diabetes in 56). Three enzymatic tests were also applied to determine serum cathepsin D (CD), dipeptidyl peptidase IV (DPP-IV) and angiotensin-converting enzyme (ACE) activities. A subgroup of 24 type 1 diabetic patients negative for microalbuminuria and hypertension were submitted to an ambulatory blood pressure monitoring to evaluate the relationship between VVH7 i.r level and blood pressure parameters. The mean serum concentration of VVH7 i.r was drastically reduced in diabetic patients (0.91+/-0.93 micromol/l versus 5.63+/-1.11 micromol/l in controls) (p<0.001). A negative correlation between VVH7 i.r level and daytime diastolic blood pressure existed in type 1 diabetic patients. There was no association of low VVH7 i.r with either type of diabetes or HbA1c level. An increase of cathepsin D activity was found in serum of diabetic patients compared to controls (0.47 U/ml versus 0.15 U/ml, respectively) whereas DPPIV activity was significantly decreased in diabetic sera (50.81 U/ml versus 282.10 U/l respectively). Diminution of VVH7 i.r in sera of diabetic patients was confirmed but still remained unexplained. Relationships between higher systolic blood pressure and decrease of VVH7 i.r reinforce the need to investigate this pathway in this disease to elucidate its role in macro- and micro-angiopathy.

A novel bradykinin potentiating peptide isolated from Bothrops jararacussu venom using catallytically inactive oligopeptidase EP24.15

Characterization of the peptide content of venoms has a number of potential benefits for basic research, clinical diagnosis, development of new therapeutic agents, and production of antiserum. Here, we use a substrate-capture assay that employs a catalytically inactive mutant of thimet oligopeptidase (EC 3.4.24.15; EP24.15) to identify novel bioactive peptides in Bothrops jararacussu venom. Of the peptides captured with inactive EP24.15 and identified by mass spectrometry, three were previously identified bradykinin-potentiating peptides (BPP), <ENWPHPQIPP (Xc), <EGGWPRPGPEIPP (XIIIa) and <EARPPHPPIPP (XIe) (where <E is a pyroglutamyl residue). In addition, we identified a novel BPP peptide containing additional AP amino acids in the C-terminus (<EARPPHPPIPPAP); this novel peptide was named BPP-AP. Next, dermal and muscle microcirculations were visualized using intravital microscopy to establish the roles of peptides BPP-XIe and BPP-AP in this process. After local administration of peptide BPP-XIe (0.5 microg.microL(-1)), leukocyte rolling flux and adhesion were increased by fivefold in post-capillary venules, without any increments in vasodilatation of arterioles compared to control experiments. In contrast, local administration of BPP-AP (0.5 microg.microL(-1)) potently induced vasodilatation of arterioles (nearly 100% increase compared with the vehicle saline control), with only a small increase in leukocyte rolling flux. Therefore, the novel BPP-AP described herein has pharmacological advantages compared to the BPP-XIe. The present study further suggests that inactive oligopeptidase EP24.15 is a useful tool for the isolation of bioactive peptides from crude biological samples.

Attenuated effects of peptides derived from porcine plasma albumin on in vitro lipid peroxidation in the liver homogenate of mice

Porcine plasma albumin was hydrolyzed with alcalase available for industrial application, and attenuated effects of peptides were evaluated using 4-Nitroquiunoline 1-oxide (4-NQO) as an inducing reagent. 4-NQO is a potent oral carcinogen, which has been found to induce lipid peroxidation in vivo and in vitro. Our results indicated that addition of 4-NQO resulted in increase of hydroxyl and superoxide radicals, glutathione peroxidase (GPx) activity and levels of malondialdehyde (MDA), and decrease in activities of superoxide dismutase (SOD) and catalase (CAT) and levels of glutathione (GSH). Simultaneous addition of peptides significantly attenuated lipid peroxidation. The lowermost molecular weight (MW) peptide fractions (<3kDa) had the highest activity. This study also demonstrated that the attenuated effects of peptides might be due to the protective interactions between cells and peptides rather than the direct inhibition of 4-NQO by peptides. The results of this study showed the potential of utilizing porcine plasma albumin as a source of functional peptides.

The endomorphin system and its evolving neurophysiological role

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2) are two endogenous opioid peptides with high affinity and remarkable selectivity for the mu-opioid receptor. The neuroanatomical distribution of endomorphins reflects their potential endogenous role in many major physiological processes, which include perception of pain, responses related to stress, and complex functions such as reward, arousal, and vigilance, as well as autonomic, cognitive, neuroendocrine, and limbic homeostasis. In this review we discuss the biological effects of endomorphin-1 and endomorphin-2 in relation to their distribution in the central and peripheral nervous systems. We describe the relationship between these two mu-opioid receptor-selective peptides and endogenous neurohormones and neurotransmitters. We also evaluate the role of endomorphins from the physiological point of view and report selectively on the most important findings in their pharmacology.

Structure−Activity Relationships of αS1-Casomorphin Using AM1 Calculations and Molecular Dynamics Simulations

This paper investigates the structure-activity relationships of alphaS1-casomorphin (alphaS1-CM) using AM1 calculations and molecular dynamics (MD) simulations. Previous studies have shown that this peptide has remarkable opioid actions, and not only has a high affinity toward all three subtypes (kappa1-kappa3) of the kappa-opioid sites, but also inhibits the proliferation of the T47D human breast cancer cell line. The systematic conformer search performed by the AM1 calculations is based on the torsional angles of the Val2-Pro3 (omega2) and Phe4-Pro5 (omega4) amide bonds. The AM1 results reveal that the alphaS1-CM conformers strongly favor the cis/cis pair of the omega2/omega4 amide bonds in the minimized energy state. Furthermore, the picture of these stable conformers is found to be a strong interaction of the coulomb's force between two terminuses. MD simulations are performed to investigate the features of both the structural stability and pharmacological activity of alphaS1-CM in aqueous solution. The simulation results reveal that the omega2/omega4 amide bonds favor the cis/cis status in the stable state. Furthermore, the pharmacophoric distance between two aromatic rings is found to be 5.0 approximately 5.4A. The chi1 rotamers of the Tyr and Phe residues show a preference for gauche (-) and trans, respectively. The side chain rotamers of alphaS1-CM are competed to those of other opioid ligands with a known potency and selectivity for delta- and mu-opioid receptors. Finally, we address a likely kappa pharmacophore model compared to the delta pharmacophore model.

Isolation and characterization of a novel bradykinin potentiating peptide (BPP) from the skin secretion of Phyllomedusa hypochondrialis

Bradykinin potentiating peptides (BPPs) from Bothrops jararaca venom were first described in the middle of 1960s and were the first natural inhibitors of the angiotensin-converting enzyme (ACE). BPPs present a classical motif and can be recognized by their typical pyroglutamyl (Pyr)/proline rich sequences presenting, invariably, a proline residue at the C-terminus. In the present study, we describe the isolation and biological characterization of a novel BPP isolated from the skin secretion of the Brazilian tree-frog Phyllomedusa hypochondrialis. This new BPP, named Phypo Xa presents the sequence Pyr-Phe-Arg-Pro-Ser-Tyr-Gln-Ile-Pro-Pro and is able to potentiate bradykinin activities in vivo and in vitro, as well as efficiently and competitively inhibit ACE. This is the first canonical BPP (i.e. Pyr-Aaa(n)-Gln-Ile-Pro-Pro) to be found not only in the frog skin but also in any other natural source other than the snake venoms.

Peptidomics: a logical sequel to proteomics

Rapid progress of separation techniques as well as methods of structural analysis provided conditions in the past decade for total screening of complex biologic mixtures for any given class of biomolecules. The present review updates the reader with the modern state of peptidomics, a chapter of chemical biology that deals with structure and biologic properties of sets of peptides present in biologic tissues, cells or fluids. Scope and limitations of currently employed experimental techniques are considered and the main results are outlined. Considerable attention will be afforded to the biologic role of peptides formed in vivo by proteolysis of nonspecialized precursor proteins with other well-defined functions. In conclusion, the connection is discussed between peptidomics and the much more mature and still closely related field of proteomics.

Proenkephalin peptide F immunoreactivity in different circulatory biocompartments after exercise

This study was the first study to examine the three circulatory biocompartments (plasma, white blood cell layer (WBC) and red blood cell layer (RBC)) and determine PF concentrations before and after exercise. Proenkephalin peptide F (PF) is an enkephalin-containing peptide found predominantly within the adrenal medulla. PF is co-packaged with epinephrine, and both can be co-secreted in response to similar stimuli. PF and epinephrine have shown immunomodulating properties. Ten healthy resistance trained men performed six sets of 10 RM squats with 2 min rest periods between sets and 10 healthy active men were matched and served as resting controls. Blood samples were obtained pre-exercise, immediately post-exercise and 15 min post-exercise and were analyzed for lactate, cortisol, epinephrine and biocompartmentalized PF. There was no change in resting control values measured across time within respective PF biocompartments and endocrine profile, indicating stability and technique validity of peptide F across the time period measured. As expected, the acute resistance exercise protocol caused an increase in lactate at 15 min post-exercise. Circulating epinephrine increased immediately post-exercise and returned to baseline during 15 min into recovery. Plasma PF increased immediate post-exercise and 15 min post-exercise, while WBC-PF and RBC-PF only increased at 15 min into recovery. For all time points tested, resting and exercise WBC-PF and RBC-PF concentrations were lower than plasma PF thus indicating a concentration difference across the three different biocompartments within the same blood sample. The presence of PF within all three biocompartments of whole blood may indicate the potential for biological transport and interactions with other cells in other biocompartments of the blood.

Strategies for designing novel functional meat products

In recent years, much attention has been paid to physiological functions of foods due to increasing concerns for health. Although there has been limited information of physiological functions of meat until recently, several attractive meat-based bioactive compounds, such as carnosine, anserine, l-carnitine, conjugated linoleic acid, have been studied. Emphasizing these activities is one possible approach for improving the health image of meat and developing functional meat products. This article provides potential benefits of representative meat-based bioactive compounds on human health and an overview of meat-based functional products. Strategies for designing novel functional meat products utilizing bioactive peptides and/or probiotic bacteria, is also discussed. This article focuses particularly on the possibility of meat protein-derived bioactive peptides, such as antihypertensive peptides. There are still some hurdles in developing and marketing novel functional meat products since such products are unconventional and consumers in many countries recognize meat and meat products to be bad for health. Along with accumulation of scientific data, there is an urgent need to inform consumers of the exact functional value of meat and meat products including novel functional foods.

Hypothesized and found mechanisms for potentiation of bradykinin actions

Potentiation of hormone actions can occur by different mechanisms, including inhibition of degrading enzymes, interaction with the hormone receptor leading to stabilization of bioactive conformation or leading to receptor homo- and hetero-oligomerization, receptor phosphorylation and dephosphorylation or can occur by directly influencing the signal transduction and ion channels. In this review the potentiation of bradykinin actions in different systems by certain compounds will be reviewed. Despite many long years of experimental research and investigation the mechanisms of potentiating action remain not fully understood. One of the most contradictory findings are the distinct differences between the inhibition of the angiotensin I-converting enzyme and the potentiation of the bradykinin induced smooth muscle reaction. Contradictory findings and hypothesized mechanisms in the literature are discussed in this review and in some cases compared to own results. Investigation of potentiating actions was extended from hypotension, smooth muscle reaction and cellular actions to activation of immunocompetent cells. In our opinion the potentiation of bradykinin action can occur by different mechanisms, depending on the system and the applied potentiating factor used.

Potentiation of bradykinin actions by analogues of the bradykinin potentiating nonapeptide BPP9alpha

Synthetic analogues of the bradykinin potentiating nonapeptide BPP9alpha indicate significantly different structural requirements for potentiation of the bradykinin (BK)-induced smooth muscle contraction (GPI) and the inhibition of isolated somatic angiotensin I-converting enzyme (ACE). The results disprove the ACE inhibition as the only single mechanism and also the direct interaction of potentiating peptides with the bradykinin receptors in transfected COS-7 cells as molecular mechanism of potentiation. Our results indicate a stimulation of inositol phosphates (IPn) formation independently from the B2 receptor. Furthermore, the results with La3+ support the role of extracellular Ca2+ and its influx through corresponding channels. The missing effect of calyculin on the GPI disproves the role of phosphatases in the potentiating action. These experimental studies should not only contribute to a better understanding of the potentiating mechanisms but also incorporate a shift in the research towards the immune system, in particular towards the immunocompetent polymorphonuclear leukocytes. The chemotaxis of these cells can be potentiated most likely by exclusive inhibition of the enzymatic degradation of bradykinin. Thus the obtained results give evidence that the potentiation of the bradykinin action can occur by different mechanisms, depending on the system and on the applied potentiating factor.

The Opioid Haemorphin-7 in Horses During Low-speed and High-speed Treadmill Exercise to Fatigue

The opioid neuropeptide haemorphin-7 was measured, by immunoreactivity, in Standardbred horses during low-speed (7 m/s) and high-speed (10 m/s) endurance exercises, lasting 49-58 and 12-16 min respectively. In parallel, heart rate, muscle temperature and plasma lactate concentrations were measured. The profile of the low-speed exercise showed significantly increased heart rate after 10 min [154 beats per minute (bpm)]. After the exercise, muscle temperature (42.1 degrees C) and plasma lactate (4.8 mmol/l) were significantly increased. The profile of the high-speed exercise was comparatively characterized by a higher increase of heart rate after 5 min (194 bpm) and higher increases of muscle temperature (43.2 degrees C) and lactate levels (15.8 mmol/l) after the exercise. The horses were probably exhausted by glycogen depletion in the low-speed exercise and by muscle pH decrease in the high-speed exercise. Haemorphin-7 increased significantly during the high-speed exercise (274.8 fmol/ml) but not during low speed (108.3 fmol/ml), coincident with the results of lactate. These results suggest that plasma haemorphin-7 is measurable in the horse by immunoreactivity, and that intense exercise stimulates release of this opioid. Such endogenous opioids are most likely involved in regulatory functions associated with pain, physical effort, inflammation, and blood pressure variation in horses, as have been established in other species.