Purification and characterization of a nitric oxide inhibitory peptide from Ruditapes philippinarum

Gastrointestinal digestion of food proteins: Anticancer, antihypertensive, anti-obesity, and immunomodulatory mechanisms of the derived peptides

Food proteins and their peptides play a significant role in the important biological processes and physiological functions of the body. The peptides show diverse biological benefits ranging from anticancer to antihypertensive, anti-obesity, and immunomodulatory, among others. In this review, an overview of food protein digestion in the gastrointestinal tract and the mechanisms involved was presented. As some proteins remain resistant and undigested, the multifarious factors (e.g. protein type and structure, microbial composition, pH levels and redox potential, host factors, etc.) affecting their colonic fermentation, the derived peptides, and amino acids that evade intestinal digestion are thus considered. The section that follows focuses on the mechanisms of the peptides with anticancer, antihypertensive, anti-obesity, and immunomodulatory effects. As further considerations were made, it is concluded that clinical studies targeting a clear understanding of the gastrointestinal stability, bioavailability, and safety of food-based peptides are still warranted.

Isolation and characterization of plant-derived exosome-like nanoparticles from Carica papaya L. fruit and their potential as anti-inflammatory agent

Inflammation is an immune system response that identifies and eliminates foreign material. However, excessive and persistent inflammation could disrupt the healing process. Plant-derived exosome-like nanoparticles (PDENs) are a promising candidate for therapeutic application because they are safe, biodegradable and biocompatible. In this study, papaya PDENs were isolated by a PEG6000-based method and characterized by dynamic light scattering (DLS), transmission Electron Microscopy (TEM), bicinchoninic acid (BCA) assay method, GC-MS analysis, total phenolic content (TPC) analysis, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. For the in vitro test, we conducted internalization analysis, toxicity assessment, determination of nitrite concentration, and assessed the expression of inflammatory cytokine genes using qRT-PCR in RAW 264.7 cells. For the in vivo test, inflammation was induced by caudal fin amputation followed by analysis of macrophage and neutrophil migration in zebrafish (Danio rerio) larvae. The result showed that papaya PDENs can be well isolated using the optimized differential centrifugation method with the addition of 30 ppm pectolyase, 15% PEG, and 0.2 M NaCl, which exhibited cup-shaped and spherical morphological structure with an average diameter of 168.8±9.62 nm. The papaya PDENs storage is stable in aquabidest and 25 mM trehalose solution at -20˚C until the fourth week. TPC estimation of all papaya PDENs ages did not show a significant change, while the DPPH test exhibited a significant change in the second week. The major compounds contained in Papaya PDENs is 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP). Papaya PDENs can be internalized and is non-cytotoxic to RAW 264.7 cells. Moreover, LPS-induced RAW 264.7 cells treated with papaya PDENs showed a decrease in NO production and downregulation mRNA expression of pro-inflammatory cytokine genes (IL-1B and IL-6) and an upregulation in mRNA expression of anti-inflammatory cytokine gene (IL-10). In addition, in vivo tests conducted on zebrafish treated with PDENs papaya showed inhibition of macrophage and neutrophil cell migration. These findings suggest that PDENs papaya possesses anti-inflammatory properties.

Anti-inflammatory peptide therapeutics and the role of sulphur containing amino acids (cysteine and methionine) in inflammation suppression: A review

BACKGROUND

Inflammation serves as our body's immune response to combat infections, pathogens, viruses, and external stimuli. Inflammation can be classified into two types: acute inflammation and chronic inflammation. Non-steroidal anti-inflammatory medications (NSAIDs) are used to treat both acute and chronic inflammatory disorders. However, these treatments have various side effects such as reduced healing efficiency, peptic ulcers, gastrointestinal toxicities, etc. METHOD: This review assesses the potential of anti-inflammatory peptides (AIPs) derived from various natural sources, such as algae, fungi, plants, animals, and marine organisms. Focusing on peptides rich in cysteines and methionine, sulphur-containing amino acids known for their role in suppression of inflammation.

RESULT

Due to their varied biological activity, ability to penetrate cells, and low cytotoxicity, bioactive peptides have garnered interest as possible therapeutic agents. The utilisation of AIPs has shown great potential in the treatment of disorders associated with inflammation. AIPs can be obtained from diverse natural sources such as algae, fungi, plants, and animals. Cysteine and methionine are sulphur-containing amino acids that aid in the elimination of free radicals, hence assisting in the treatment of inflammatory diseases.

CONCLUSION

This review specifically examines several sources of AIPs including peptides that contain numerous cysteines and methionine. In addition, the biological characteristics of these amino acids and advancements in peptide delivery are also discussed.

Characterization and Exploration of the Neuroprotective Potential of Oat-Protein-Derived Peptides in PC12 Cells and Scopolamine-Treated Zebrafish

Neurodegenerative disorders pose a substantial risk to human health, and oxidative stress, cholinergic dysfunction, and inflammation are the major contributors. The purpose of this study was to explore the neuroprotective effects of oat protein hydrolysate (OPH) and identify peptides with neuroprotective potential. This study is the first to isolate and identify OPH peptides with neuroprotective potential, including DFVADHPFLF (DF-10), HGQNFPIL (HL-8), and RDFPITWPW (RW-9), by screening via peptidomes and molecular-docking simulations. These peptides showed positive effects on the activity of antioxidant enzymes and thus reduced oxidative stress through regulation of Nrf2-keap1/HO-1 gene expression in vitro and in vivo. The peptides also significantly ameliorated scopolamine-induced cognitive impairment in the zebrafish model. This improvement was correlated with mitigation of MDA levels, AChE activity, and levels of inflammatory cytokines in the brains of zebrafish. Furthermore, these peptides significantly upregulated the mRNA expression of Bdnf, Nrf2, and Erg1 in the brains of zebrafish with neurodegenerative disorders. Collectively, oat peptides have potential for use as active components in nutraceutical applications for the prevention of neurodegenerative diseases.

Structure characterization of soybean peptides and their protective activity against intestinal inflammation

Soybean peptides serve as functional foods with impressive health benefits. The structure characteristics of peptides are highly related to the health benefits. The structure-activity relationship and mechanism underlined are important scientific questions in this field. To answer these questions, soybean peptides were produced by combinatory enzymatic hydrolysis in this work. Fifty-two peptide sequences were identified by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The anti-inflammatory activities of these peptides were investigated by using a lipopolysaccharide (LPS)-induced inflammation cell model. Soybean peptides could significantly promote cell proliferation. Additionally, soybean peptides could alleviate LPS-induced inflammation by reducing the production and expression of nitric oxide (NO), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). Moreover, soybean peptides could promote the mRNA expression of proteins related to inflammation inhibition (IL-10) and tight junction modulation. The structure-activity relationship was addressed. The results documented the potential of soybean peptides as functional foods.

Separation and identification of collagen peptides derived from enzymatic hydrolysate of Salmo salar skin and their anti-inflammatory activity in lipopolysaccharide (LPS)-induced RAW264.7 inflammatory model

Inflammation is considered as a major risk for the pathogenesis of chronic diseases. Due to the adverse events caused by the long-term use of anti-inflammatory drugs, it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. In this study, flavourzyme hydrolysate (for 0.5 hr) presented the strongest anti-inflammatory activity, which was further separated by ultrafiltration and column chromatography, followed by LC-MS/MS identification. Peptide APD, QA, KA, and WG were identified as anti-inflammatory peptides, which significantly reduced secretion of NO, IL-6, IL-1β, and TNF-α in inflammatory macrophages. Among them, peptide QA showed the best overall anti-inflammatory effect, with the IC₅₀ value against NO production of 849.3 μM. Most of the identified anti-inflammatory peptides were stably against digestion, and they had abundant frequencies in the α (I/II) chain of Salmo salar collagen. Our findings indicated the potential of S. salar skin hydrolysates as functional food to prevent inflammation. PRACTICAL APPLICATIONS: Long-term use of anti-inflammatory drugs causes adverse events like gastrorrhagia, and it is necessary to develop alternative and safe dietary supplements from natural products against inflammation. Salmo salar skin, as a major byproduct of total fish, has not been effectively utilized during processing. In this study, novel anti-inflammatory oligopeptides with high activities were separated and identified from S. salar skin gelatin hydrolysate, which were stably against digestion, and presented a high bioavailability and abundant frequencies in collagen. Our study highlighted the added value of aquatic by-products and suggested that S. salar skin collagen hydrolysate could be used as a promising dietary supplement against inflammatory diseases.

Structural analysis and biological effects of a neutral polysaccharide from the fruits of Rosa laevigata

A neutral water-soluble polysaccharide (RLP50-2) was extracted and purified from the fruits of Rosa laevigata. The absolute molecular weight was determined as 1.26 × 10⁴ g/mol. Monosaccharide composition analysis showed that RLP50-2 mainly consisted of glucose, arabinose, and galactose. Structural analysis revealed that RLP50-2 consisted of →5)-α-L-Araf-(1→, →2,5)-α-L-Araf-(1→, →3,5)-α-L-Araf-(1→, →4)-α-D-Glcp-(1→, →6)-α-D-Glcp-(1→, →3,6)-β-D-Glcp-(1→, →4)-α-D-Galp-(1→, →6)-β-D-Galp-(1→, →2)-β-D-Xylp-(1→, terminal α-L-arabinose, and terminal β-D-mannose. Biological assays showed that RLP50-2 had immunomodulatory activities using cell and zebrafish models. Moreover, RLP50-2 showed significantly antitumor activities by inhibiting tumor cell proliferation and migration and blocking angiogenesis. These results suggested that RLP50-2 could be developed as a potential immunomodulatory agent or antitumor candidate drug in biomedicine field.

Isolation, purification and identification of immunologically active peptides from Hericium erinaceus

Biologically active peptides released by proteins are important in regulating immunity. The purpose of this study was to isolate and purify an immunologically active peptide from Hericium erinaceus (H. erinaceus) and to explore its effect on cytokine secretion and differentiation of macrophages. An active peptide with an amino acid sequence, Lys-Ser-Pro-Leu-Tyr (KSPLY) was obtained from H. erinaceus protein by ultrafiltration combined with multistage chromatography separation and identification technology. Subsequently, it was confirmed that the synthetic peptide KSPLY had a good immunomodulatory activity at a concentration of 100 μmol/L and could promote the secretion of NO, IL-1β, IL-6 and TNF-α by macrophages. The effects of KSPLY on M1 macrophages and M2 macrophages were also studied. Results showed that KSPLY inhibited the secretion of NO and IL-6 by M1 macrophages and promoted the tendency of M2 macrophages to transform to M1 macrophages. Therefore, it can be concluded that KSPLY is an effective immunomodulatory peptide that may be beneficial in cancer treatment and human health improvement.

Anti-inflammatory action of two novel peptides derived from peanut worms (Sipunculus nudus) in lipopolysaccharide-induced RAW264.7 macrophages

Peanut worm (Sipunculus nudus Linn.) protein was hydrolyzed by three proteases, and NO scavenging activity of the protein hydrolysates was evaluated. The hydrolysate obtained using Alcalase® showed the highest NO scavenging activity. This hydrolysate was fractionated using 10-, 5-, and 3 kDa molecular weight cut-off membranes, and the lowest MW fraction (<3 kDa) exhibited the highest NO scavenging activity. The <3 kDa fraction was further purified by gel filtration and high-performance liquid chromatographies. The peptides in the HPLC fraction with the strongest anti-NO activity were identified by quadrupole-time-of-flight mass spectrometry as LSPLLAAH (821.48 Da) and TVNLAYY (843.42 Da). Both peptides and the corresponding pure synthetic peptides inhibited NO production by RAW 264.7 macrophages without cytotoxicity. Quantitative real-time RT-PCR analysis showed that peptides LSPLLAAH and TVNLAYY reduced expression of proinflammatory cytokine genes iNOS, IL-6, TNF-α, and COX-2 in RAW 264.7 macrophages, suggesting that these peptides are novel anti-inflammatory candidates.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Anti-inflammatory potential of novel hexapeptide derived from Meretrix meretrix foot and its functional properties

The study aimed to identify bioactive peptide from Meretrix meretrix Linnaeus foot (MMF) and examine its potential of suppressing inflammation. In brief, the anti-inflammatory activity was identified by erythrocyte membrane protection and protein denaturation assay from MMF peptic 9th-h hydrolysate and was separated with three molecular weight cut-off units. The obtained four fractions were testified for activity and the fraction (10-3 kDa) with maximum activity was purified using gel permeation chromatography. Finally, the peptide sequence was identified as Asn-Pro-Ala-Gln-Asp-Cys (647.559 Da) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The hexapeptide was characterised for functional properties at different pH range. The non-toxic hexapeptide was able to reduce the cyclooxygenase (COX)-2 activation, pro-inflammatory cytokines and nitric oxide (NO) production significantly in RAW264.7 macrophage cells. The current results propose that the hexapeptide derived from MMF protein can act as an effective anti-inflammatory against pro-inflammatory cytokines, COX-2 and NO. Moreover, it could be used as an effective alternative source for drugs in pharma and also as an ingredient in food industries.

The Potential of Food Protein-Derived Bioactive Peptides against Chronic Intestinal Inflammation

Inflammation can cause various chronic diseases like inflammatory bowel diseases. Various food protein-derived bioactive peptides (BAPs) with anti-inflammatory activity have the potential to manage these diseases. The aim of this paper is to overview the mechanisms and the molecular targets of BAPs to exert anti-inflammatory activity. In this review, the in vitro and in vivo effects of BAPs on intestinal inflammation are highlighted. The mechanism, pathways, and future perspectives of BAPs as the potential sources of therapeutic treatments to alleviate intestinal inflammation are provided, including nuclear factor-κB, mitogen-activated protein kinase, Janus kinase-signal transducer and activator of transcription, and peptide transporter 1 (PepT1), finding that PepT1 and gut microbiota are the promising targets for BAPs to alleviate the intestinal inflammation. This review provides a comprehensive understanding of the role of dietary BAPs in attenuating inflammation and gives a novel direction in nutraceuticals for people or animals with intestinal inflammation.

Inhibitory Effects of Walnut (Juglans regia) Peptides on Neuroinflammation and Oxidative Stress in Lipopolysaccharide-Induced Cognitive Impairment Mice

Increasing level of inflammation and oxidative stress could lead to memory impairment. The purpose of this study was to determine the neuroprotective effects of walnut peptides against memory deficits induced by lipopolysaccharide (LPS) in mice and further to explore the underlying anti-inflammatory mechanisms against LPS-elicited inflammation in BV-2 cells. Results showed that walnut protein hydrolysate (WPH) and its low-molecular-weight fraction (WPHL) could ameliorate the memory deficits induced by LPS via normalizing the inflammatory response and oxidative stress in brain, especially WPHL. Furthermore, 18 peptides with anti-inflammatory activities on LPS-activated BV-2 cells were identified from WPHL and it was found that Trp, Gly, and Leu residues in peptides might contribute to the anti-inflammation. Meanwhile, the strong anti-inflammatory effects of LPF, GVYY, and APTLW might be related to their hydrophobic and aromatic amino acid residues as well. LPF, GVYY, and APTLW could reduce the content of proinflammatory mediators and cytokines by downregulating related enzyme expressions and mRNA expressions. Additionally, ROS and mitochondria homeostasis might also contribute to their anti-inflammatory effects.

Ultrasound treatment on the structure of goose liver proteins and antioxidant activities of its enzymatic hydrolysate

This study was to investigate the effects of ultrasonic treatment on the physical and chemical properties of goose liver protein (GLP) and the anti-oxidative activity of the goose liver protein hydrolysate (GLPH). By measuring the average particle size, sulfhydryl and disulfide bond, secondary structure, hydroxyl radical inhibition, 1, 1-diphenyl-2-picrylhydrazyl radical scavenging rate, and ferrous ion chelating ability, we found that 300 and 600 W ultrasonic treatment reduced the particle size of GLP from 509.7 μm to 313.7 μm and 273.1 μm, respectively, and significantly decreased the content of sulfhydryl and the structures of α-helix and β-turn (p < .05). Meanwhile, the content of disulfide bond and β-sheet structure increased significantly (p < .05); the antioxidant capacity of GLPH increased significantly (p < .05). After 300 W ultrasonic treatment, the GLP in the enzymatic hydrolysis process was more conducive to the release of antioxidant substances compared with the 600 W ultrasonic-treated GLP. PRACTICAL APPLICATIONS: The physical and chemical properties of the GLP were changed by ultrasonic treatment, which was beneficial to improve the texture quality of goose liver paste and the anti-oxidative activity of GLPH. It could enhanced the functional characteristics of goose liver paste by enzymolysis. Meanwhile, antioxidant components extracted by ultrasonic treatment from goose liver could be added to foods as an excipient to improve the antioxidant properties.

Nitric Oxide Synthesis Inhibition and Anti-Inflammatory Effect of Polypeptide Isolated from Chicken Feather Meal in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages

Nitric oxide (NO) plays a key role in the pathogenesis of inflammation and has been implicated in endotoxin-induced tissue injury. Chicken feather meal is a rich source of amino acids that may serve as a peptide hydrolysate to inhibit NO activity. Anti-inflammatory hydrolysates of chicken feather meal were prepared and fractionated into five samples based on molecular mass. The smallest fraction (<0.65 kDa) exhibited the highest NO inhibitory activity without cytotoxicity towards macrophage RAW 264.7 cells. Further subfractions were sufficient to obtain amino acid sequences by Q-TOF LC-MS/MS ESI analysis. Of these, the SNPSVAGVR (885.97 Da) peptide and its corresponding pure synthetic peptide have inhibitory activity against NO production by RAW 264.7 cells (IC₅₀=(55.2±0.2) mM) without cytotoxicity. Reverse transcriptase polymerase chain reaction (RT-PCR) and quantitative real-time RT-PCR results revealed that the peptide of the obtained fraction reduced transcript expression levels of the pro-inflammatory cytokines iNOS, TNF-α, COX-2 and IL-6 in lipopolysaccharide-stimulated RAW 264.7 cells. These results suggest that the peptides derived from the chicken feather meal protein could potentially be used as a promising ingredient in functional foods or nutraceuticals against inflammatory diseases.

Free radical scavenging and anti-inflammatory potential of a protein hydrolysate derived from salmon bones on RAW 264.7 macrophage cells

BACKGROUND

Salmon bones, a waste by-product from the salmon industry, were used as a protein hydrolysate source for the production of bioactive peptides. The aim of this work was to evaluate the potential antioxidant and anti-inflammatory properties of salmon bone protein hydrolysate (SBPH).

RESULTS

Salmon bones were hydrolyzed by separately using one of four proteases (Alcalase, Favourzyme, Neutrase and papain) at various concentrations (10, 25 and 50 mg mL^-1 ), where the SBPH derived from 10 mg mL^-1 papain hydrolysis exhibited the highest nitric oxide (NO) radical scavenging activity. After ultrafiltration, the MW < 0.65 kDa fraction showed the strongest NO inhibitory activity and was further fractionated by gel filtration chromatography (G1 and G2 fractions) and reverse-phase high-performance liquid chromatographic fractionation of the G1 fraction, from which the three main peaks (H1, H2 and H3) were found to have a marked NO-inhibitory activity and their peptide sequences were determined. Moreover, the G1 fraction was shown to inhibit both the lipopolysaccharide (LPS)-induced NO production and the LPS-induced inducible NO synthase , interleukin-6, tumor necrosis factor-α and induced NO production and the LPSCOX-2 mRNA levels in RAW 264.7 cells.

CONCLUSIONS

Salmon bones from the salmon fisheries and farming industry were utilized by enzymatic hydrolysis for the production of valuable peptides. The results of this study suggested that bioactive peptides derived from salmon bones would be alternative anti-inflammation materials in functional resources. © 2019 Society of Chemical Industry.

Antimicrobial and Immunomodulatory Properties and Applications of Marine-Derived Proteins and Peptides

Marine organisms provide an abundant source of potential medicines. Many of the marine-derived biomaterials have been shown to act as different mechanisms in immune responses, and in each case they can significantly control the immune system to produce effective reactions. Marine-derived proteins, peptides, and protein hydrolysates exhibit various physiologic functions, such as antimicrobial, anticancer, antioxidant, antihypertensive, and anti-inflammatory activities. Recently, the immunomodulatory properties of several antimicrobial peptides have been demonstrated. Some of these peptides directly kill bacteria and exhibit a variety of immunomodulatory activities that improve the host innate immune response and effectively eliminate infection. The properties of immunomodulatory proteins and peptides correlate with their amino acid composition, sequence, and length. Proteins and peptides with immunomodulatory properties have been tested in vitro and in vivo, and some of them have undergone different clinical and preclinical trials. This review provides a comprehensive overview of marine immunomodulatory proteins, peptides, and protein hydrolysates as well as their production, mechanisms of action, and applications in human therapy.

Mussel (Mytilus coruscus) Water Extract Containing Taurine Prevents LPS-Induced Inflammatory Responses in Zebrafish Model

Mussel (Mytilus coruscus) water extract had strong anti-inflammatory activities, but the effects and its mechanisms of mussel on anti-inflammatory properties in vivo remain to be determined. This study, therefore, was designed to investigate anti-inflammatory activities of mussel water extract containing a large amounts of taurine (151.96 nmol/mg) using the lipopolysaccharide (LPS)-induced inflammatory zebrafish model. In this study, mussel water extract containing taurine shows potent protective effects against the cell death stimulated by LPS exposure in zebrafish embryos. In addition, zebrafish subjected to LPS treatment exhibited significantly increased reactive oxygen species (ROS) and nitric oxide (NO) levels. However, mussel water extract markedly suppressed LPS-induced ROS and NO production. Our results indicate that mussel water extract attenuated inflammation by inhibiting the LPS-induced intracellular ROS and NO production in zebrafish embryos. These findings could demonstrate the anti-inflammatory activity of mussel water extract containing taurine, which might have a protective effects on inflammatory diseases.

Antioxidant and ACE Inhibitory Activity of Enzymatic Hydrolysates from Ruditapes philippinarum

Ruditapes philippinarum proteins were hydrolyzed by trypsin, neutrase, and pepsin. The antioxidant activities and ACE inhibitory activity of hydrolysates were analyzed and the antioxidant activities were related to their molecular weight distribution and amino acid compositions. Results indicated the hydrolysis of proteins led to an increase in small peptides and free amino acids. The antioxidant activities of Ruditapes philippinarum hydrolysates against DPPH radical scavenging, inhibition on linoleic acid peroxidation, and reducing power showed that the neutrase hydrolysate exhibited the strongest antioxidant activity. In addition, an ACE inhibition assay revealed that the pepsin hydrolysate had the highest ACE inhibitory ability. Ruditapes philippinarum protein hydrolysates could be a promising source of natural antioxidant and ACE inhibitory.

Structural-features of food-derived bioactive peptides with anti-inflammatory activity: A brief review

Chronic inflammatory conditions such as obesity, type-2 diabetes, and cardiovascular diseases are the leading causes of mortality worldwide. Hence, much research interest in bioactive peptides has been stimulated due to lack of potent pharmacological interventions. Although many such peptides have been identified from food proteins, insufficient information is available on their structure-function relationship. Presence of hydrophobic and positively charged amino acids is a common occurrence for the peptides with anti-inflammatory properties. However, inconsistent findings have also been reported. Most of the food-derived peptides exhibited their anti-inflammatory activities primarily by inhibiting signaling components of either NF-κB or MAPK pathway, which are the two major pathways involved in chronic inflammation following uncontrolled signal activation. This review highlighted the structural requirements of the peptides to exhibit anti-inflammatory activity based on the current knowledge about food-derived anti-inflammatory peptides and their underlying molecular mechanisms of action. PRACTICAL APPLICATIONS: While research in the food-derived bioactive peptide is gaining momentum, but the ability to translate these new findings into the commercial product such as nutraceuticals and functional foods, remains delayed. The most prominent reasons for this delay are the lack of detailed research on, (i) the structure-function relationship of the peptide and the underlying molecular mechanisms of these bioactive peptides, and (ii) the interaction of these peptides with different cellular elements in the disease pathophysiology. This review gives an insight into the structure-activity relationship of bioactive peptides involved in anti-inflammatory responses. The information provided here would be highly beneficial to describe the possible anti-inflammatory activity of any newly identified peptides from different food sources.

Isolation, purification and the anti-hypertensive effect of a novel angiotensin I-converting enzyme (ACE) inhibitory peptide from Ruditapes philippinarum fermented with Bacillus natto

A novel ACE inhibitory peptide (Val-Ile-Ser-Asp-Glu-Asp-Gly-Val-Thr-His) with a high anti-hypertensive effect isolated from Ruditapes philippinarum fermented with Bacillus natto.

Mass spectrometry analysis and in silico prediction of allergenicity of peptides in tryptic hydrolysates of the proteins from Ruditapes philippinarum

BACKGROUND

Ruditapes philippinarum is nutrient-rich and widely-distributed, but little attention has been paid to the identification and characterization of the bioactive peptides in the bivalve. In the present study, we evaluated the peptides of the R. philippinarum that were enzymolysised by trypsin using a combination of ultra-performance liquid chromatography separation and electrospray ionization quadrupole time-of-flight tandem mass spectrometry, followed by data processing and sequence-similarity database searching. The potential allergenicity of the peptides was assessed in silico.

RESULTS

The enzymolysis was performed under the conditions: E:S 3:100 (w/w), pH 9.0, 45 °C for 4 h. After separation and detection, the Swiss-Prot database and a Ruditapes philippinarum sequence database were used: 966 unique peptides were identified by non-error tolerant database searching; 173 peptides matching 55 precursor proteins comprised highly conserved cytoskeleton proteins. The remaining 793 peptides were identified from the R. philippinarum sequence database. The results showed that 510 peptides were labeled as allergens and 31 peptides were potential allergens; 425 peptides were predicted to be nonallergenic.

CONCLUSION

The abundant peptide information contributes to further investigations of the structure and potential function of R. philippinarum. Additional in vitro studies are required to demonstrate and ensure the correct production of the hydrolysates for use in the food industry with respect to R. philippinarum. © 2017 Society of Chemical Industry.

Immunomodulating peptides for food allergy prevention and treatment

Among the most promising strategies currently assayed against IgE-mediated allergic diseases stands the possibility of using immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. This review focuses on the beneficial effects of food derived immunomodulating peptides on food allergy, which can be directly exerted in the intestinal tract or once being absorbed through the intestinal epithelial barrier to interact with immune cells. Food peptides influence intestinal homeostasis by maintaining and reinforcing barrier function or affecting intestinal cell-signalling to nearby immune cells and mucus secretion. In addition, they can stimulate cells of the innate and adaptive immune system while supressing inflammatory responses. Peptides represent an attractive alternative to whole allergens to enhance the safety and efficacy of immunotherapy treatments. The conclusions drawn from curative and preventive experiments in murine models are promising, although there is a need for more pre-clinical studies to further explore the immunomodulating strategy and its mechanisms and for a deeper knowledge of the peptide sequence and structural requirements that determine the immunoregulatory function.

Anti-inflammatory activity of ethanolic extract from skipjack tuna (Katsuwonus pelamis) heart in LPS-induced RAW 264.7 cells and mouse ear edema model

This study investigated the anti-inflammatory activity of the ethanolic extract (THEE) obtained from the heart of skipjack tuna using lipopolysaccharide (LPS)-induced RAW 264.7 cells. THEE markedly suppressed the production of nitric oxide (NO), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and IL-1β in a dose-dependent manner. In addition, THEE decreased the expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), nuclear factor-kappa B p65 (NF-κB p65), and mitogen-activated protein kinases (MAPKs) including phosphorylated c-Jun NH₂-terminal kinase (p-JNK), phosphorylated extracellular signal-related kinase (p-ERK), and p-p38 proteins. Moreover, THEE orally treated at doses of 50, 100, and 250 mg/kg inhibited the croton oil-induced edema formation and the reduction of the epidermal/dermal thickness and the mast cell numbers was observed in histological analysis. There were no mortalities occurred in mice administered THEE at 5,000 mg/kg body weight. Taken together, these results indicate that THEE exerts the anti-inflammatory activities via inhibition of NF-κB and MAPKs activation.

Anti-inflammatory Properties of Bioactive Peptide Derived from Gastropod Influenced by Enzymatic Hydrolysis

The visceral mass of the gastropod, Harpa ventricosa was hydrolysed using trypsin, alcalase and pepsin for 12 h to produce protein hydrolysates. Subsequently, the active hydrolysate was observed in the 3rd hour of tryptic hydrolysate (29.17 ± 0.62 and 34.85 ± 0.55 %) using human red blood cell (HRBC) membrane stabilization and albumin denaturation (AD) assays. The active hydrolysate was fractionated by membrane filtration unit, where <10-kDa fraction revealed better anti-inflammatory activity with IC₅₀ value 6.27 ± 0.05 and 5.38 ± 0.02 mg/ml for HRBC and AD assays, respectively. Additionally, the active fraction contains essential and non-essential (aspartic acid, arginine, glutamic acid and leucine) amino acids and, sequentially, the active fraction was further purified using consecutive chromatography, in which fraction C-II exhibited strong anti-inflammatory activity (HRBC 56.02 ± 0.52 and AD 50.71 ± 1.10 % assays). The non-toxic, low molecular weight (690.2 Da) hexapeptide (Ala-Lys-Gly-Thr-Trp-Lys) suppressed the nitric oxide (NO) and pro-cytokine production in a dose-dependent manner on THP-1 cell lines.

Purification and identification of anti-inflammatory peptides derived from simulated gastrointestinal digests of velvet antler protein ( Cervus elaphus Linnaeus)

The objective of this study was to identify anti-inflammatory peptides from simulated gastrointestinal digest (pepsin–pancreatin hydrolysate) of velvet antler protein. The hydrolysate was purified using ultrafiltration and consecutive chromatographic methods. The anti-inflammatory activity of the purified fraction was evaluated by the inhibition of NO production in lipopolysaccharide-induced RAW 264.7 macrophages. Four anti-inflammatory peptides, VH (Val–His), LAN (Leu–Ala–Asn), AL (Ala–Leu), and IA (Ile–Ala), were identified by liquid chromatography/tandem mass spectrometry. Each of these peptides demonstrated a U-shaped dose–effect relationship. VH, LAN, AL and IA showed the strongest anti-inflammatory activities at 200 μg/mL, that is, 15.5%, 13.0%, 16.0% and 11.2% inhibition of lipopolysaccharide-induced NO production, respectively. Additionally, the enhanced NO inhibitory activity was observed for the peptides mixture, indicating the possible synergistic effects. These results suggested that the peptides derived from velvet antler protein could potentially be used as a promising ingredient in functional foods or nutraceuticals against inflammatory diseases.

Anti-inflammatory effect of enzymatic hydrolysates from Styela clava flesh tissue in lipopolysaccharide-stimulated RAW 264.7 macrophages and in vivo zebrafish model

BACKGROUND/OBJECTIVES

In this study, potential anti-inflammatory effect of enzymatic hydrolysates from Styela clava flesh tissue was assessed via nitric oxide (NO) production in lipopolysaccahride (LPS) induced RAW 264.7 macrophages and in vivo zebrafish model.

MATERIALS/METHODS

We investigated the ability of enzymatic hydrolysates from Styela clava flesh tissue to inhibit LPS-induced expression of pro-inflammatory mediators in RAW 264.7 macrophages, and the molecular mechanism through which this inhibition occurred. In addition, we evaluated anti-inflammatory effect of enzymatic hydrolysates against a LPS-exposed in in vivo zebrafish model.

RESULTS

Among the enzymatic hydrolysates, Protamex-proteolytic hydrolysate exhibited the highest NO inhibitory effect and was fractionated into three ranges of molecular weight by using ultrafiltration (UF) membranes (MWCO 5 kDa and 10 kDa). The above 10 kDa fraction down-regulated LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), thereby reducing production of NO and prostaglandin E₂ (PGE₂) in LPS-activated RAW 264.7 macrophages. The above 10 kDa fraction suppressed LPS-induced production of pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. In addition, the above 10 kDa fraction inhibited LPS-induced phosphorylation of extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinase (JNK), and p38. Furthermore, NO production in live zebrafish induced by LPS was reduced by addition of the above 10 kDa fraction from S. clava enzymatic hydrolysate.

CONCLUSION

The results of this study suggested that hydrolysates derived from S. clava flesh tissue would be new anti-inflammation materials in functional resources.

Purification of a novel nitric oxide inhibitory peptide derived from enzymatic hydrolysates of Mytilus coruscus

Shellfish contain significant levels of high quality protein and are therefore a potential source for biofunctional high-value peptides. To purify a novel anti-inflammatory peptide from Mytilus coruscus (M. coruscus), we applied enzymatic hydrolysis and tangential flow filtration (TFF) and investigated its nitric oxide inhibitory property. To prepare the peptide, eight proteases were employed for enzymatic hydrolysis. Flavouzyme hydrolysates, which showed clearly superior nitric oxide inhibitory activity on lipopolysaccharide (LPS)-stimulated RAW264.7, were further purified using a TFF system and consecutive chromatographic methods. Finally, a novel anti-inflammatory peptide composed of 10 amino acid residues was obtained, and the sequence was identified as Gly-Val-Ser-Leu-Leu-Gln-Gln-Phe-Phe-Leu at N-terminal position. The peptide from M. coruscus effectively inhibited nitric oxide production on macrophage cells. This is the first report of an anti-inflammatory peptide derived from the hydrolysates of M. coruscus.

Toxicity study of isolated polypeptide from wool hydrolysate

The cytotoxicity of wool polypeptide has been evaluated by both cell and animal models. Wool was dissolved in sodium hydroxide solution, the pH value of the solution was adjusted to 5.55 and the precipitate was harvested as wool polypeptide. The spray-dried polypeptide was collected as powders and characterized by SEM, FTIR and TG-DSC. The cell culturing results showed that wool polypeptide had no obvious negative effect on cell viability in vitro. Both acute oral toxicity and subacute 30-day oral toxicology studies showed that wool polypeptide had no influence on body weight, feed consumption, blood chemistry, and hematology at any dose levels. There were no treatment related findings on gross or detailed necroscopy, organ weights, organ/body weight ratios and histology. Our study indicated the absence of toxicity in wool polypeptide and supported its safe use as a food ingredient or drug carrier.

Purification and characterization of a novel angiotensin I-converting enzyme inhibitory peptide derived from an enzymatic hydrolysate of duck skin byproducts

An angiotensin I-converting enzyme (ACE) inhibitory peptide was isolated and identified from hydrolysates of duck skin byproducts. Duck skin byproducts were hydrolyzed using nine proteases (Alcalase, Collagenase, Flavourzyme, Neutrase, papain, pepsin, Protamex, trypsin, and α-chymotrypsin) to produce an antihypertensive peptide. Of the various hydrolysates produced, the α-chymotrypsin hydrolysate exhibited the highest ACE inhibitory activity. The hydrolysate was purified using fast protein liquid chromatography (FPLC) and high-performance liquid chromatography (HPLC). The amino acid sequence of the ACE inhibitory peptide was identified as a hexapeptide Trp-Tyr-Pro-Ala-Ala-Pro, with a molecular weight of 693.90 Da. The peptide had an IC50 value of 137 μM, and the inhibitory pattern of the purified ACE inhibitor from duck skin byproducts was determined to be competitive by Lineweaver-Burk plots. In addition, the peptide was synthesized and the ACE inhibitory activity was verified in vivo. Spontaneously hypertensive rats (SHR) exhibited significantly decreased blood pressure and heart rate after peptide injection. Taken together, the results suggest that Trp-Tyr-Pro-Ala-Ala-Pro may be useful as a new antihypertensive agent.

Purification and characterization of a novel peptide with inhibitory effects on colitis induced mice by dextran sulfate sodium from enzymatic hydrolysates of Crassostrea gigas

The anti-inflammatory activity of purified peptides from Crassostrea gigas (C. gigas) hydrolysates was studied. To prepare hydrolysates from C. gigas, we used eight different proteinases and the anti-inflammatory activities were determined using a nitric oxide (NO) assay in RAW264.7 cells. Among the hydrolysates, Protamex hydrolysates showed the highest anti-inflammatory activity. We separated and purified the total hydrolysate using an ultrafiltration membrane system and consecutive chromatographic methods. Finally, we obtained a peptide with the following sequence: Gln-Cys-Gln-Cys-Ala-Val-Glu-Gly-Gly-Leu at N-terminal position. The anti-inflammatory peptide purified from C. gigas inhibited NO production by 72.2% compared to the lipopolysaccharide (LPS) treated group. In addition, the Protamex hydrolysates from C. gigas showed decreased serum IgE levels and increased spleen CD4(+)/CD8(+) levels on dextran sulfate sodium (DSS) induced colitis in mice. These results suggest the peptide and hydrolysate from C. gigas possess potent anti-inflammatory effect.