Peptide fraction from sturgeon muscle by pepsin hydrolysis exerts anti-inflammatory effects in LPS-stimulated RAW264.7 macrophages via MAPK and NF-κB pathways

Enzyme-free method for preparation of sturgeon extracts with antioxidant, hepatoprotective and immune-enhancing functions

Sturgeon has a long lifespan and slow evolutionary rate due to their powerful endogenous antioxidant system. This work aimed to assess the in vitro and in vivo antioxidant activity of sturgeon extracts from both muscle and roe. The extraction process without enzyme hydrolysis is not only simple, but also can produce extracts with better free radicals scavenging abilities than enzymatic hydrolysates in both cellular and in vivo experiments. Moreover, in mouse models with liver injury and immunosuppression treatment, the sturgeon extracts demonstrated strong hepatoprotective and immune-enhancing functions, comparable to vitamin C and ginseng extract supplements, which were attributed to abundant antioxidant peptides of the extracts. The 15 isolated peptides exhibited diverse free radical scavenging ability. Therefore, the sturgeon extracts showed high potential to be applied in food and biomedical industries.

Novel Peptides from Sturgeon Ovarian Protein Hydrolysates Prevent Oxidative Stress-Induced Dysfunction in Osteoblast Cells: Purification, Identification, and Characterization

This study aimed to explore antioxidant peptides derived from sturgeon (Acipenser schrenckii) ovaries that exhibit antiosteoporotic effects in oxidative-induced MC3T3-E1 cells. The F3-15 component obtained from sturgeon ovarian protein hydrolysates (SOPHs) via gel filtration and RP-HPLC significantly increased the cell survival rate (from 49.38 ± 2.88 to 76.26 ± 2.09%). Two putative antioxidant-acting peptides, FDWDRL (FL6) and FEGPPFKF (FF8), were screened from the F3-15 faction via liquid chromatography-tandem mass spectrometry (LC-MS/MS) and through prediction by computer simulations. Molecular docking results indicated that the possible antioxidant mechanisms of FL6 and FF8 involved blocking the active site of human myeloperoxidase (hMPO). The in vitro tests showed that FL6 and FF8 were equally adept at reducing intracellular ROS levels, increasing the activity of antioxidant enzymes, and protecting cells from oxidative injuries by inhibiting the mitogen-activated protein kinase (MAPK) pathway and activating the phosphoinositide-3 kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase-3β (GSK-3β) signaling pathway. Moreover, both peptides could increase differentiation and mineralization abilities in oxidatively damaged MC3T3-E1 cells. Furthermore, FF8 exhibited high resistance to pepsin and trypsin, showcasing potential for practical applications.

Advances in Research on the Activity Evaluation, Mechanism and Structure-Activity Relationships of Natural Antioxidant Peptides

Antioxidant peptides are a class of biologically active peptides with low molecular weights and stable antioxidant properties that are isolated from proteins. In this review, the progress in research on the activity evaluation, action mechanism, and structure-activity relationships of natural antioxidant peptides are summarized. The methods used to evaluate antioxidant activity are mainly classified into three categories: in vitro chemical, in vitro cellular, and in vivo animal methods. Also, the biological effects produced by these three methods are listed: the scavenging of free radicals, chelation of metal ions, inhibition of lipid peroxidation, inhibition of oxidative enzyme activities, and activation of antioxidant enzymes and non-enzymatic systems. The antioxidant effects of natural peptides primarily consist of the regulation of redox signaling pathways, which includes activation of the Nrf2 pathway and the inhibition of the NF-κB pathway. The structure-activity relationships of the antioxidant peptides are investigated, including the effects of peptide molecular weight, amino acid composition and sequence, and secondary structure on antioxidant activity. In addition, four computer-assisted methods (molecular docking, molecular dynamics simulation, quantum chemical calculations, and the determination of quantitative structure-activity relationships) for analyzing the structure-activity effects of natural peptides are summarized. Thus, this review lays a theoretical foundation for the development of new antioxidants, nutraceuticals, and cosmetics.

Preparation of polysaccharide-based nanoparticles by chitosan and flaxseed gum polyelectrolyte complexation as carriers for bighead carp (Aristichthys nobilis) peptide delivery

Polysaccharide-based nanoparticles formed by the polyelectrolyte complexation between chitosan (CS) and flaxseed gum (FG) was developed in this work, and it was further used as a carrier for bighead carp peptide (BCP) delivery. The CS molecular weight (MW) of 50 kDa and CS/FG mass ratio of 1:2 at pH 3.5 were optimal conditions for the NP preparation, with the minimum particle size (∼155.1 nm) and the maximum BCP encapsulation efficiency (60.3 %). The BCP-loaded CS/FG NPs exhibited the smallest particle size (175.8 nm). Both CS/FG NPs and CS/FG-BCP NPs exhibited roughly uniform spherical shape. FT-IR spectra confirmed the existence of hydrogen bonds and electrostatic interactions in the nanoparticles. The BCP-loaded NPs displayed a higher thermal stability than BCP. Moreover, the release of BCP was controllable and dose-dependent, following a first-order kinetics model. These findings suggested that our CS/FG NPs are a promising carrier for bioactive peptide delivery.

Patrinoside and Patrinoside A from Patrinia scabiosaefolia Improve Insulin Resistance by Inhibiting NF-κB, MAPK Pathways and Oxidative Stress in RAW264.7 and 3 T3-L1 Cells

Patrinia scabiosaefolia, as traditional food and medicine plant, was used to treat appendicitis, enteritis, and hepatitis for thousand years in China. Patrinoside and patrinoside A isolated from P. scabiosaefolia could significantly improve insulin resistance (IR) by activating PI-3 K/AKT signaling pathway in our previous study. Since IR is closely related to inflammation, their anti-inflammatory activities in RAW264.7 inflammatory model induced by LPS and in 3 T3-L1 IR inflammatory model induced by TNF-α were evaluated to identify whether the effects on improving IR related to anti-inflammatory activity. In RAW264.7 cells, patrinoside and patrinoside A significantly inhibited the transcription and secretion of inflammatory mediators NO, TNF-α, and IL-6. Western blot analysis showed that the significant inhibition of phosphorylation of IκB and P65 and P38, ERK and JNK suggested that the effects were exerted through NF-κB pathway and MAPK pathway. In 3 T3-L1 cells, patrinoside and patrinoside A also inhibited the activation of NF-κB and MAPK pathways through inhibiting the transcriptions of inflammatory cytokines IL-6 and chemokines MCP-1 and MIP-1α. These events resulted in the inhibition of macrophages migration to adipocytes. In addition, patrinoside and patrinoside A ameliorated oxidative stress by inhibiting ROS release in LPS-stimulated RAW264.7 cells. In conclusion, patrinoside and patrinoside A could active PI-3 K/AKT pathway, inhibit NF-κB pathway, MAPK pathway, and improve oxidative stress, which showed multipathways on improving IR. These results provided the scientific basis for material basis and mechanism on improving IR of P. scabiosaefolia.

Peptides and protein hydrolysates exhibiting anti-inflammatory activity: sources, structural features and modulation mechanisms

Inflammation is the response of the immune system to harmful stimuli such as tissue injury, infection or toxic chemicals, which has the aim of eliminating irritants or pathogenic microorganisms and enhancing tissue repair. Uncontrolled long-lasting acute inflammation can gradually progress to chronic, causing a variety of chronic inflammatory diseases that are usually treated with anti-inflammatory drugs, but most of them are inadequate to control chronic responses and are also associated with adverse side effects. Thus, many efforts are being directed to develop alternative and more selective anti-inflammatory therapies from natural products. One main field of interest is the obtaining of bioactive peptides exhibiting anti-inflammatory activity from sustainable protein sources like edible insects or agroindustry and fishing by-products. This work highlighted the structure-activity relationship of anti-inflammatory peptides. Small peptides with molecular weight under 1 kDa and amino acid chain length between 2 to 20 residues are generally the most active because of the higher probability to be absorbed in the intestine and penetrate into cells when compared with the larger size peptides. The presence of hydrophobic (Val, Ile, Pro) and positively charged (His, Arg, Lys) amino acids is another common occurrence for anti-inflammatory peptides. Interestingly, a high percentage (77%) of these bioactive peptides can be found in alternative sustainable protein sources such as Tenebrio molitor or sunflower, apart from its original protein source. However, not all of these peptides with anti-inflammatory potential in vitro achieve good scores by the in silico bioactivity predictors studied. Therefore, it is essential to implement current bioinformatics tools, in order to complement in vitro experiments with prior prediction of potential bioactive peptides.

Anti-inflammatory action of ark shell (Scapharca subcrenata) protein hydrolysate in LPS-stimulated RAW264.7 murine macrophages

Potential anti-inflammatory effects of ark shell (Scapharca subcrenata) protein hydrolysates were investigated. Ark shell protein hydrolysates were prepared using Alcalase® and pepsin and were designated ASAH and ASPH, respectively. The nitric oxide (NO) inhibitory activity of ASAH and ASPH was determined in lipopolysaccharides (LPS)-stimulated RAW264.7 murine macrophages, and the results showed that ASAH inhibited better NO inhibitory activity than ASPH. ASAH suppressed inflammatory mediator, a prostaglandin E2, secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), and production of reactive oxygen species (ROS) dose dependently. It inhibited the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and simulated heme oxygenase-1 (HO-1) protein expression. However, the pharmacological approach revealed that pretreatment with zinc protoporphyrin ІX (ZnPP), an inhibitor of HO-1, reversed the anti-inflammatory effect of ASAH. Moreover, ASAH upregulated phosphorylation of mitogen-activated protein kinases (MAPKs) including ERK1/2, JNK1/2, and p38 MAPK. To find out the role of MAPKs phosphorylation, MAPKs inhibitors were used, and the results showed that ASAH-mediated HO-1 protein expression and Nrf2 nuclear translocation were abolished. Taken all together, this study revealed that ASAH has a potential anti-inflammatory activity through regulation of the MAPK-dependent HO-1/Nrf2 pathway. PRACTICAL APPLICATIONS: Food-derived marine bioactive peptides, due to their pivotal role in biological activities, are gaining much attention recently. However, the anti-inflammatory activities of ark shell protein hydrolysates still remain to be investigated. This study investigated that ASAH shows potential anti-inflammatory activities through regulation of the MAPK-dependent HO-1/Nrf2 pathway in RAW264.7 murine macrophages. These findings indicated that ASAH may be used as a dietary supplement, functional food, and medicinal drug for the management of inflammation and inflammation-associated diseases.

Proteomics Characterization of Food-Derived Bioactive Peptides with Anti-Allergic and Anti-Inflammatory Properties

Bioactive peptides are found in foods and dietary supplements and are responsible for health benefits with applications in human and animal medicine. The health benefits include antihypertensive, antimicrobial, antithrombotic, immunomodulatory, opioid, antioxidant, anti-allergic and anti-inflammatory functions. Bioactive peptides can be obtained by microbial action, mainly by the gastrointestinal microbiota from proteins present in food, originating from either vegetable or animal matter or by the action of different gastrointestinal proteases. Proteomics can play an important role in the identification of bioactive peptides. High-resolution mass spectrometry is the principal technique used to detect and identify different types of analytes present in complex mixtures, even when available at low concentrations. Moreover, proteomics may provide the characterization of epitopes to develop new food allergy vaccines and the use of immunomodulating peptides to induce oral tolerance toward offending food allergens or even to prevent allergic sensitization. In addition, food-derived bioactive peptides have been investigated for their anti-inflammatory properties to provide safer alternatives to nonsteroidal anti-inflammatory drugs (NSAIDs). All these bioactive peptides can be a potential source of novel drugs and ingredients in food and pharmaceuticals. The following review is focused on food-derived bioactive peptides with antiallergic and anti-inflammatory properties and summarizes the new insights into the use of proteomics for their identification and quantification.

Piperine Derived from Piper nigrum L. Inhibits LPS-Induced Inflammatory through the MAPK and NF-κB Signalling Pathways in RAW264.7 Cells

Piperine, an important natural product, has a good anti-inflammatory effect. However, few researchers have studied its mechanism in these pathways. The objective of this research was to evaluate the molecular mechanism underlying the anti-inflammatory responses of piperine in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The purification and characterization of piperine from Piper nigrum L. were determined by HPLC, UPLC-Q-TOF-MS and ¹H NMR. Then, the anti-inflammatory activity was evaluated by a reagent test kit, ELISA kits, RT-PCR and Western blot experiments. The results suggested that piperine (90.65 ± 0.46% purity) at a concentration of 10–20 mg/L attenuated the production of NO and ROS, downregulated the protein and mRNA expression levels of TNF-α, IL-1β and IL-6, and upregulated the protein and mRNA transcription levels of IL-10. Meanwhile, the Western blot results indicated that piperine could inhibit the phosphorylation levels of the ERK, JNK, p38 and p65 proteins. Our findings suggest that piperine is a potential anti-inflammatory substance, whose molecular mechanism may be to regulate the key factors of the NF-κB and MAPK signalling pathways.

Diversified Polyketides With Anti-inflammatory Activities From Mangrove Endophytic Fungus Daldinia eschscholtzii KBJYZ-1

In total, five new polyketide derivatives: eschscholin B (2), dalditone A and B (3 and 4), (1R, 4R)-5-methoxy-1,2,3,4-tetrahydronaphthalene-1,4-dio (5), and daldilene A (6), together with 10 known as analogs (1, 7-15) were isolated from the mangrove endophytic fungus Daldinia eschscholtzii KBJYZ-1. Their structures and absolute configurations were established by extensive analysis of NMR and HRESIMS spectra data combined with ECD calculations and the reported literature. Compounds 2 and 6 showed significant cell-based anti-inflammatory activities with IC₅₀ values of 19.3 and 12.9 μM, respectively. In addition, western blot results suggested that compound 2 effectively inhibits the expression of iNOS and COX-2 in LPS-induced RAW264.7 cells. Further molecular biology work revealed the potential mechanism of 2 exerts anti-inflammatory function by inactivating the MAPK and NF-κB signaling pathways.

Anti-Inflammatory Phytoconstituents of Origanum Majorana

Origanum majorana belongs to the Lamiaceae family as a famous spice plant in Egypt, which is used to treat arthritis, allergies, fever, flu, hypertension, respiratory infections, migraine, and asthma. In our studies, it was found that the ethanol extract of O. marjoram could significantly reduce NO release at 200 ( $P<0.001$ ), 100 ( $P<0.001$ ) and 50 ( $P<0.01$ ) μg/mL compared with the model group. Therefore, the chemical constituents were further studied to obtain the bioactive compounds. As a result, ten compounds were isolated and identified from the 70% ethanol extract of O. marjoram, including six flavonoids (3–8), two terpene derivatives (9-10), one lignan (2), and one phenolic glycoside (1). Among them, compounds 1–3, 5, and 9-10 were isolated from this genus for the first time. Compounds 1, 9, and 10 could significantly decrease the content of NO at the concentration of 100 μm ( $P<0.001$ ) in RAW264.7 cells induced by LPS. Furthermore, compounds 9 and 10 were more effective than compound 1 to lower the content at 50 μm ( $P<0.001$ ).

The Anti-Inflammatory Effect of Bovine Bone-Gelatin-Derived Peptides in LPS-Induced RAW264.7 Macrophages Cells and Dextran Sulfate Sodium-Induced C57BL/6 Mice

The bioactive peptides hydrolyzed from bone collagen have been found to possess health-promoting effects by regulating chronic diseases such as arthritis and hypertension. In the current study, the anti-inflammatory effect of bovine bone gelatin peptides (GP) was evaluated in 264.7 macrophages cells and followed by animal trials to investigate their interference on inflammatory cytokines and gut microbiota compositions in dextran sodium sulfate (DSS)-induced C57BL/6 mice. The GP was demonstrated to alleviate the extra secretion of interleukin-6 (IL-6), nitric oxide (NO) and tumor necrosis factor-α(TNF-α) in lipopolysaccharide (LPS)-induced RAW264.7 cells. In DSS-induced colitis mice, the gavage of GP was demonstrated to ameliorate the IBD symptoms of weight loss, hematochezia and inflammatory infiltration in intestinal tissues. In serum, the proinflammatory cytokines (TNF-α,IL-6, MCP-1, IL-1β) were suppressed along with the decreasing effect on toll-like receptor 4 and cyclooxygenase-2 by GP treatment. In the analysis of gut microbiota, the GP was checked to modulate the abundance of Akkermansia, Parasutterella, Peptococcus, Bifidobacterium and Saccharibacteria. The above results imply that GP could attenuate DSS-induced colitis by suppressing the inflammatory cytokines and regulating the gut microbiota.

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.

An updated review on food-derived bioactive peptides: Focus on the regulatory requirements, safety, and bioavailability

Food-derived bioactive peptides (BAPs) are recently utilized as functional food raw materials owing to their potential health benefits. Although there is a huge amount of scientific research about BAPs' identification, purification, characterization, and physiological functions, and subsequently, many BAPs have been marketed, there is a paucity of review on the regulatory requirements, bioavailability, and safety of BAPs. Thus, this review focuses on the toxic peptides that could arise from their primary proteins throughout protein extraction, protein pretreatment, and BAPs' formulation. Also, the influences of BAPs' length and administration dosage on safety are summarized. Lastly, the challenges and possibilities in BAPs' bioavailability and regulatory requirements in different countries were also presented. Results revealed that the human studies of BAPs are essential for approvals as healthy food and to prevent the consumers from misinformation and false promises. The BAPs that escape the gastrointestinal tract epithelium and move to the stomach are considered good peptides and get circulated into the blood using different pathways. In addition, the hydrophobicity, net charge, molecular size, length, amino acids composition/sequences, and structural characteristics of BAPs are critical for bioavailability, and appropriate food-grade carriers can enhance it. The abovementioned features are also vital to optimize the solubility, water holding capacity, emulsifying ability, and foaming property of BAPs in food products. In the case of safety, the possible allergenic and toxic peptides often exhibit physiological functions and could be produced during the hydrolysis of food proteins. It was also noted that the production of iso-peptides bonds and undesirable Maillard reaction might occur during protein extraction, sample pretreatments, and peptide synthesis.

Anti-inflammatory and Antioxidant Activity of Peptides From Ethanol-Soluble Hydrolysates of Sturgeon (Acipenser schrenckii) Cartilage

Research has shown that cartilage containing chondroitin sulfate and protein presents versatile bioactivities. Chondroitin sulfate in cartilage is beneficial to activate the immune system while the protein/peptide has not been fully understood. The current study investigated the antioxidant and anti-inflammatory properties of ethanol-soluble hydrolysates of sturgeon cartilage (ESCH) prepared through hot-pressure, enzymatic hydrolysis and ethanol extraction. UV spectrum, IR and agarose gel electrophoresis results suggested the successful exclusion of chondroitin sulfate from peptides. Nitric oxide (NO) floods in cells activated by inflammation. It was inhibited when administrated with ESCH. To further explain the observed anti-inflammatory activity, ESCH was separated with Sephadex G-15 into 3 components, among which F3 showed a higher NO inhibition rate and significantly reduced the production of the proinflammatory cytokine IL-6. In addition, the yield of IL-10 increased. Western blotting suggested that F3 downregulated the NO content and IL-6 level by suppressing Mitogen-activated protein kinases (MAPK) channels. Moreover, both ESCH and F3 showed DPPH and ABTS free radical scavenging abilities which was possibly related to the anti-inflammatory property. These results indicated that ESCH behaved anti-inflammatory and antioxidant activities. Cartilage may be a good source to produce anti-inflammatory peptides.

Fish and Shellfish-Derived Anti-Inflammatory Protein Products: Properties and Mechanisms

The interest in utilizing food-derived compounds therapeutically has been rising. With the growing prevalence of systematic chronic inflammation (SCI), efforts to find treatments that do not result in the side effects of current anti-inflammatory drugs are underway. Bioactive peptides (BAPs) are a particularly promising class of compounds for the treatment of SCI, and the abundance of high-quality seafood processing byproducts (SPB) makes it a favorable material to derive anti-inflammatory BAPs. Recent research into the structural properties of anti-inflammatory BAPs has found a few key tendencies including they tend to be short and of low molecular weight (LMW), have an overall positive charge, contain hydrophobic amino acids (AAs), and be rich in radical scavenging AAs. SPB-derived anti-inflammatory BAPs have been observed to work via inhibition of the NF-κB and MAPK pathways by disrupting the phosphorylation of IκBα and one or more kinases (ERK, JNK, and p38), respectively. Radical scavenging capacity has also been shown to play a significant role in the efficacy of SPB-derived anti-inflammatory BAPs. To determine if SPB-derived BAPs can serve as an effective treatment for SCI it will be important to understand their properties and mechanisms of action, and this review highlights such findings in recent research.