OM-LV20, a novel peptide from odorous frog skin, accelerates wound healing in vitro and in vivo

Peptide OM-LV20 promotes arteriogenesis induced by femoral artery ligature via the miR-29b-3p/VEGFA axis

BACKGROUND AND AIMS

Therapeutic arteriogenesis is a promising direction for the treatment of ischemic disease caused by atherosclerosis. However, pharmacological or biological approaches to stimulate functional collateral vessels are not yet available. Identifying new drug targets to promote and explore the underlying mechanisms for therapeutic arteriogenesis is necessary.

METHODS

Peptide OM-LV20 (20 ng/kg) was administered for 7 consecutive days on rat hindlimb ischemia model, collateral vessel growth was assessed by H&E staining, liquid latex perfusion, and specific immunofluorescence. In vitro, we detected the effect of OM-LV20 on human umbilical vein endothelial cells (HUVEC) proliferation and migration. After transfection, we performed quantitative real-time polymerase chain reaction, in situ-hybridization and dual luciferase reporters to assessed effective miRNAs and target genes. The proteins related to downstream signaling pathways were detected by Western blot.

RESULTS

OM-LV20 significantly increased visible collateral vessels and endothelial nitric oxide synthase (eNOS), together with enhanced inflammation cytokine and monocytes/macrophage infiltration in collateral vessels. In vitro, we defined a novel microRNA (miR-29b-3p), and its inhibition enhanced proliferation and migration of HUVEC, as well as the expression of vascular endothelial growth factor A (VEGFA). OM-LV20 also promoted migration and proliferation of HUVEC, and VEGFA expression was mediated via inhibition of miR-29b-3p. Furthermore, OM-LV20 influenced the protein levels of VEGFR2 and phosphatidylinositol3-kinase (PI3K)/AKT and eNOS in vitro and invivo.

CONCLUSIONS

Our data indicated that OM-LV20 enhanced arteriogenesis via the miR-29b-3p/VEGFA/VEGFR2-PI3K/AKT/eNOS axis, and highlighte the application potential of exogenous peptide molecular probes through miRNA, which could promote effective therapeutic arteriogenesis in ischemic conditions.

A Horn Peptide-Thermoresponsive Hydrogel for Angiogenesis and Bone Regeneration

The management of critical-sized bone defects presents a formidable clinical challenge, especially given the increasing incidence of bone diseases in the aging population. Consequently, there is an increased demand for minimally invasive bone repair materials that can effectively address this challenge, particularly in outpatient settings. In this study, the goal is to develop an injectable and biodegradable biomaterial that adheres to and fills bone-defect sites to support bone regeneration. The osteogenic and angiogenic activities of animal horn peptides are investigated by incorporating them into biologically active moieties, in combination with a novel thermosensitive hydrogel. The resulting thermosensitive hydrogel exhibited essential biological functionalities, allowing precise modulation of its physical and chemical properties. Notably, the hydrogel incorporating the horn peptide rapidly filled the bone defect site, promoting both angiogenesis and bone induction. Consequently, this approach significantly accelerates new bone regeneration. In summary, the findings of this study present a promising, minimally invasive solution for addressing critical-sized bone defects.

Antioxidant peptides, the guardian of life from oxidative stress

Reactive oxygen species (ROS) are produced during oxidative metabolism in aerobic organisms. Under normal conditions, ROS production and elimination are in a relatively balanced state. However, under internal or external environmental stress, such as high glucose levels or UV radiation, ROS production can increase significantly, leading to oxidative stress. Excess ROS production not only damages biomolecules but is also closely associated with the pathogenesis of many diseases, such as skin photoaging, diabetes, and cancer. Antioxidant peptides (AOPs) are naturally occurring or artificially designed peptides that can reduce the levels of ROS and other pro-oxidants, thus showing great potential in the treatment of oxidative stress-related diseases. In this review, we discussed ROS production and its role in inducing oxidative stress-related diseases in humans. Additionally, we discussed the sources, mechanism of action, and evaluation methods of AOPs and provided directions for future studies on AOPs.

miR-186-5p targets TGFβR2 to inhibit RAW264.7 cell migration and proliferation during mouse skin wound healing

BACKGROUND

Active peptides play a vital role in the development of new drugs and the identification and discovery of drug targets. As the first reported native peptide homodimer with pro-regenerative potency, OA-GP11d could potentially be used as a novel molecular probe to help elucidate the molecular mechanism of skin wound repair and provide new drug targets.

METHODS

Bioinformatics analysis and luciferase assay were adopted to determine microRNAs (miRNAs) and its target. The prohealing potency of the miRNA was determined by MTS and a Transwell experiment against mouse macrophages. Enzyme-linked immunosorbent assay, realtime polymerase chain reaction, and western blotting were performed to explore the molecular mechanisms.

RESULTS

In this study, OA-GP11d was shown to induce Mus musculus microRNA-186-5p (mmu-miR-186-5p) down-regulation. Results showed that miR-186-5p had a negative effect on macrophage migration and proliferation as well as a targeted and negative effect on TGF-β type II receptor (TGFβR2) expression and an inhibitory effect on activation of the downstream SMAD family member 2 (Smad2) and protein-p38 kinase signaling pathways. Importantly, delivery of a miR-186-5p mimic delayed skin wound healing in mice.

CONCLUSION

miR-186-5p regulated macrophage migration and proliferation to delay wound healing through the TGFβR2/Smad2/p38 molecular axes, thus providing a promising new pro-repair drug target.

Characterization and mechanism of action of amphibian-derived wound-healing-promoting peptides

Wound-healing-promoting peptides are excellent candidates for developing wound-healing agents due to their small size and low production cost. Amphibians are one of the major sources of bioactive peptides, including wound-healing-promoting peptides. So far, a series of wound-healing-promoting peptides have been characterized from amphibians. We hereby summarized the amphibian-derived wound-healing-promoting peptides and their mechanism of action. Among these peptides, two peptides (tylotoin and TK-CATH) were characterized from salamanders, and twenty five peptides were characterized from frogs. These peptides generally have small sizes with 5-80 amino acid residues, nine peptides (tiger17, cathelicidin-NV, cathelicidin-DM, OM-LV20, brevinin-2Ta, brevinin-2PN, tylotoin, Bv8-AJ, and RL-QN15) have intramolecular disulfide bonds, seven peptides (temporin A, temporin B, esculentin-1a, tiger17, Pse-T2, DMS-PS2, FW-1, and FW-2) are amidated at the C-terminus, and the others are linear peptides without modifications. They all efficiently accelerated the healing of skin wounds or photodamage in mice or rats. They selectively promoted the proliferation and migration of keratinocytes and fibroblasts, recruited neutrophils and macrophages to wounds, and regulated the immune response of neutrophils and macrophages in wounds, which were essential for wound healing. Interestingly, MSI-1, Pse-T2, cathelicidin-DM, brevinin-2Ta, brevinin-2PN, and DMS-PS2 were just antimicrobial peptides, but they also significantly promoted the healing of infected wounds by clearing off bacteria. Considering the small size, high efficiency, and definite mechanism, amphibian-derived wound-healing-promoting peptides might be excellent candidates for developing novel wound-healing-promoting agents in future.

Amphibian-derived wound healing peptides: chemical molecular treasure trove for skin wound treatment

Amphibian-derived wound healing peptides thus offer new intervention measures and strategies for skin wound tissue regeneration. As novel drug lead molecules, wound healing peptides can help analyze new mechanisms and discover new drug targets. Previous studies have identified various novel wound healing peptides and analyzed novel mechanisms in wound healing, especially competing endogenous RNAs (ceRNAs) (e.g., inhibition of miR-663a promotes skin repair). In this paper, we review amphibian-derived wound healing peptides, including the acquisition, identification, and activity of peptides, a combination of peptides with other materials, and the analysis of underlying mechanisms, to better understand the characteristics of wound healing peptides and to provide a molecular template for the development of new wound repair drugs.

Microbial Natural Products with Wound-Healing Properties

Wound healing continues to pose a challenge in clinical settings. Moreover, wound management must be performed properly and efficiently. Acute wound healing involves multiple cell divisions, a new extracellular matrix, and the process of formation, such as growth factors and cytokines, which are released at the site of the wound to regulate the process. Any changes that disrupt the healing process could cause tissue damage and prolong the healing process. Various factors, such as microbial infection, oxidation, and inflammation, can delay wound healing. In order to counter these problems, utilizing natural products with wound-healing effects has been reported to promote this process. Several natural products have been associated with wound healing, most of which are from medicinal plants. However, secondary microbial metabolites have not been extensively studied for their wound-healing properties. Further, investigations on the wound-healing control of natural microbial products are required due to a lack of studies. This review discussed the in vivo and in vitro research on the wound healing activities of natural microbial products, which may assist in the development of better wound treatments in the future.

A Novel Peptide from Polypedates megacephalus Promotes Wound Healing in Mice

Amphibian skin contains wound-healing peptides, antimicrobial peptides, and insulin-releasing peptides, which give their skin a strong regeneration ability to adapt to a complex and harsh living environment. In the current research, a novel wound-healing promoting peptide, PM-7, was identified from the skin secretions of Polypedates megacephalus, which has an amino acid sequence of FLNWRRILFLKVVR and shares no structural similarity with any peptides described before. It displays the activity of promoting wound healing in mice. Moreover, PM-7 exhibits the function of enhancing proliferation and migration in HUVEC and HSF cells by affecting the MAPK signaling pathway. Considering its favorable traits as a novel peptide that significantly promotes wound healing, PM-7 can be a potential candidate in the development of novel wound-repairing drugs.

Peptides Isolated from Amphibian Skin Secretions with Emphasis on Antimicrobial Peptides

The skin of amphibians is a tissue with biological functions, such as defense, respiration, and excretion. In recent years, researchers have discovered a large number of peptides in the skin secretions of amphibians, including antimicrobial peptides, antioxidant peptides, bradykinins, insulin-releasing peptides, and other peptides. This review focuses on the origin, primary structure, secondary structure, length, and functions of peptides secreted from amphibians' skin. We hope that this review will provide further information and promote the further study of amphibian skin secretions, in order to provide reference for expanding the research and application of amphibian bioactive peptides.

Zn2+ Cross-Linked Alginate Carrying Hollow Silica Nanoparticles Loaded with RL-QN15 Peptides Provides Promising Treatment for Chronic Skin Wounds

Chronic and non-healing wounds pose a great challenge to clinical management and patients. Many studies have explored novel interventions against skin wounds, with bioactive peptides, nanoparticles, and hydrogels arousing considerable attention regarding their therapeutic potential. In this study, the prohealing peptide RL-QN15 was loaded into hollow silica nanoparticles (HSNs), with these HSN@RL-QN15 nanocomposites then combined with zinc alginate (ZA) gels to obtain HSN@RL-QN15/ZA hydrogel. The characteristics, biological properties, and safety profiles of the hydrogel composites were then evaluated. Results showed that the hydrogel had good porosity, hemocompatibility, biocompatibility, and broad-spectrum antimicrobial activity, with the slow release of loaded RL-QN15. Further analysis indicated that the hydrogel promoted skin cell proliferation and keratinocyte scratch repair, regulated angiogenesis, reduced inflammation, and accelerated re-epithelialization and granulation tissue formation, resulting in the rapid healing of both full-thickness skin wounds and methicillin-resistant Staphylococcus aureus biofilm-infected chronic wounds in mice. This peptide-based hydrogel provides a novel intervention for the treatment of chronic skin wounds and shows promise as a wound dressing in the field of tissue regeneration.

Antimicrobial-wound healing peptides: Dual-function molecules for the treatment of skin injuries

Chronic non-healing wounds caused by microbial infections extend the necessity for hospital care and constitute a public health problem and a great financial burden. Classic therapies include a wide range of approaches, from wound debridement to vascular surgery. Antimicrobial peptides (AMPs) are a preserved trait of the innate immune response among different animal species, with known effects on the immune system and microorganisms. Thus, AMPs may represent promising candidates for the treatment of chronic wounds with dual functionality in two of the main agents that lead to this condition, proliferation of microorganisms and uncontrolled inflammation. Here, our goal is to critically review AMPs with wound healing properties. We strongly believe that these dual-function peptides alone, or in combination with other wound healing strategies, constitute an underexplored field that researchers can take advantage of.

Bioactivities, Applications, Safety, and Health Benefits of Bioactive Peptides From Food and By-Products: A Review

Bioactive peptides generated from food proteins have great potential as functional foods and nutraceuticals. Bioactive peptides possess several significant functions, such as antioxidative, anti-inflammatory, anticancer, antimicrobial, immunomodulatory, and antihypertensive effects in the living body. In recent years, numerous reports have been published describing bioactive peptides/hydrolysates produced from various food sources. Herein, we reviewed the bioactive peptides or protein hydrolysates found in the plant, animal, marine, and dairy products, as well as their by-products. This review also emphasizes the health benefits, bioactivities, and utilization of active peptides obtained from the mentioned sources. Their possible application in functional product development, feed, wound healing, pharmaceutical and cosmetic industries, and their use as food additives have all been investigated alongside considerations on their safety.

Amphibian-derived peptide homodimer OA-GL17d promotes skin wound regeneration through the miR-663a/TGF-β1/Smad axis

Background

Amphibian-derived peptides exhibit considerable potential in the discovery and development of new therapeutic interventions for clinically challenging chronic skin wounds. MicroRNAs (miRNAs) are also considered promising targets for the development of effective therapies against skin wounds. However, further research in this field is anticipated. This study aims to identify and provide a new peptide drug candidate, as well as to explore the underlying miRNA mechanisms and possible miRNA drug target for skin wound healing.

Methods

A combination of Edman degradation, mass spectrometry and cDNA cloning were adopted to determine the amino acid sequence of a peptide that was fractionated from the secretion of Odorrana andersonii frog skin using gel-filtration and reversed-phase high-performance liquid chromatography. The toxicity of the peptide was evaluated by Calcein-AM/propidium iodide (PI) double staining against human keratinocytes (HaCaT cells), hemolytic activity against mice blood cells and acute toxicity against mice. The stability of the peptide in plasma was also evaluated. The prohealing potency of the peptide was determined by MTS, scratch healing and a Transwell experiment against HaCaT cells, full-thickness injury wounds and scald wounds in the dorsal skin of mice. miRNA transcriptome sequencing analysis, enzyme-linked immunosorbent assay, real-time polymerase chain reaction and western blotting were performed to explore the molecular mechanisms.

Results

A novel peptide homodimer (named OA-GL17d) that contains a disulfide bond between the 16th cysteine residue of the peptide monomer and the sequence ‘GLFKWHPRCGEEQSMWT’ was identified. Analysis showed that OA-GL17d exhibited no hemolytic activity or acute toxicity, but effectively promoted keratinocyte proliferation and migration and strongly stimulated the repair of full-thickness injury wounds and scald wounds in the dorsal skin of mice. Mechanistically, OA-GL17d decreased the level of miR-663a to increase the level of transforming growth factor-β1 (TGF-β1) and activate the subsequent TGF-β1/Smad signaling pathway, thereby resulting in accelerated skin wound re-epithelialization and granular tissue formation.

Conclusions

Our results suggest that OA-GL17d is a new peptide drug candidate for skin wound repair. This study emphasizes the importance of exogenous peptides as molecular probes for exploring competing endogenous RNA mechanisms and indicates that miR-663a may be an effective target for promoting skin repair.

Amphibian-derived peptide homodimer promotes regeneration of skin wounds

Despite the increasing treatments in skin wound repair, existing therapeutic drugs cannot meet current needs. As such, skin wound repair remains a considerable clinical challenge, and thus the discovery of new pro-healing agents is crucial. Here, we identified the first naturally occurring peptide homodimer named as OA-GP11 dimer (OA-GP11d) from Odorrana andersonii (odorous frog) through the combinational methods of peptidomics and genomics. OA-GP11d was linked by the intramolecular disulfide formed by the 10^th cysteine residues from the monomer of peptide with sequence of GPLSGINAECM, which effectively promoted the repair of full-thickness and burn wounds in mice. The underlying molecular mechanisms revealed that OA-GP11d not only accelerated the migration and cell-scratch healing of mouse keratinocytes, but also activated the mitogen-activated protein kinases (MAPKs) signaling pathway (phosphorylation of p38 and ERK subgroups) in immortalized human keratinocytes (HaCaT). Besides, OA-GP11d reduced the phosphorylation of nuclear factor-κB (NF-κB) and inhibitor of NF-κB (I-κB) induced by lipopolysaccharide stimulation in mouse macrophages, and inhibited the release of associated inflammatory factors tumor necrosis factor (TNF)-α and interleukin (IL)-6. OA-GP11d is the first identified naturally occurring peptide dimer with significant pro-healing potency. Our results highlight the importance of amphibians as a source of novel pro-healing agents and suggest OA-GP11d as a potential new pro-regenerative drug candidate.

Novel amphibian-derived antioxidant peptide protects skin against ultraviolet irradiation damage

Given the adverse impact of ultraviolet irradiation on human skin, as well as currently limited interventions, the discovery of new molecules with anti-photodamage potency remains critical. In this research, we obtained a new bioactive peptide (named OS-LL11, amino acid sequence 'LLPPWLCPRNK') from Odorrana schmackeri. Results showed that OS-LL11 could directly scavenge free radicals and sustain the viability of mouse keratinocytes challenged by ultraviolet B (UVB) irradiation or hydrogen peroxide (H₂O₂) by decreasing the levels of lipid peroxidation, malondialdehyde, and reactive oxygen species while increasing the level of catalase, Keap-1, HO-1, GCLM, and NQO1. Interestingly, topical application of OS-LL11 protected mouse skin against UVB irradiation damage by up-regulating the levels of superoxide dismutase, glutathione, and nitric oxide, but down-regulating the levels of H₂O₂, IL-1α, IL-1β, IL-6, TNF-α, 8-OHdG, Bcl-2, and Bax, as well as the number of apoptotic bodies. Our research demonstrated the anti-photodamage activity of a novel amphibian-derived peptide and the potential underlying mechanisms related to its free radical scavenging ability and antioxidant, anti-inflammatory, and anti-apoptotic activities. This study provides a new molecule for the development of anti-skin photodamage drugs or cosmetics and highlights the prospects of amphibian-derived peptides in photodamaged skin intervention.

Mesoporous polydopamine nanoparticles carrying peptide RL-QN15 show potential for skin wound therapy

BACKGROUND

Skin wound healing remains a considerable clinical challenge, thus stressing the urgent need for the development of new interventions to promote repair. Recent researches indicate that both peptides and nanoparticles may be potential therapies for the treatment of skin wounds.

METHODS

In the current study, the mesoporous polydopamine (MPDA) nanoparticles were prepared and the peptide RL-QN15 that was previously identified from amphibian skin secretions and exhibited significant potential as a novel prohealing agent was successfully loaded onto the MPDA nanoparticles, which was confirmed by results of analysis of scanning electron microscopy and fourier transform infrared spectroscopy. The encapsulation efficiency and sustained release rate of RL-QN15 from the nanocomposites were determined. The prohealing potency of nanocomposites were evaluated by full-thickness injured wounds in both mice and swine and burn wounds in mice.

RESULTS

Our results indicated that, compared with RL-QN15 alone, the prohealing potency of nanocomposites of MPDA and RL-QN15 in the full-thickness injured wounds and burn wounds in mice was increased by up to 50 times through the slow release of RL-QN15. Moreover, the load on the MPDA obviously increased the prohealing activities of RL-QN15 in full-thickness injured wounds in swine. In addition, the obvious increase in the prohealing potency of nanocomposites of MPDA and RL-QN15 was also proved by the results from histological analysis.

CONCLUSIONS

Based on our knowledge, this is the first research to report that the load of MPDA nanoparticles could significantly increase the prohealing potency of peptide and hence highlighted the promising potential of MPDA nanoparticles-carrying peptide RL-QN15 for skin wound therapy.

Hollow polydopamine nanoparticles loading with peptide RL-QN15: a new pro-regenerative therapeutic agent for skin wounds

BACKGROUND

Although the treatments of skin wounds have greatly improved with the increase in therapeutic methods and agents, available interventions still cannot meet the current clinical needs. Therefore, the development of new pro-regenerative therapies remains urgent. Owing to their unique characteristics, both nanomaterials and peptides have provided novel clues for the development of pro-regenerative agents, however, more efforts were still be awaited and anticipated.

RESULTS

In the current research, Hollow polydopamine (HPDA) nanoparticles were synthesized and HPDA nanoparticles loading with RL-QN15 (HPDAlR) that was an amphibian-derived peptide with obvious prohealing activities were prepared successfully. The characterization, biodistribution and clearance of both HPDA nanoparticles and HPDAlR were evaluated, the loading efficiency of HPDA against RL-QN15 and the slow-releasing rate of RL-QN15 from HPDAlR were also determined. Our results showed that both HPDA nanoparticles and HPDAlR exerted no obvious toxicity against keratinocyte, macrophage and mice, and HPDA nanoparticles showed no prohealing potency in vivo and in vitro. Interestingly, HPDAlR significantly enhanced the ability of RL-QN15 to accelerate the healing of scratch of keratinocytes and selectively modulate the release of healing-involved cytokines from macrophages. More importantly, in comparison with RL-QN15, by evaluating on animal models of full-thickness injured skin wounds in mice and oral ulcers in rats, HPDAlR showed significant increasing in the pro-regenerative potency of 50 and 10 times, respectively. Moreover, HPDAlR also enhanced the prohealing efficiency of peptide RL-QN15 against skin scald in mice and full-thickness injured wounds in swine.

CONCLUSIONS

HPDA obviously enhanced the pro-regenerative potency of RL-QN15 in vitro and in vivo, hence HPDAlR exhibited great potential in the development of therapeutics for skin wound healing.

Antimicrobial peptides: mechanism of action, activity and clinical potential

The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria. As an excellent candidate to overcome antibiotic resistance, antimicrobial peptides (AMPs) that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity. These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action. This comprehensive review provides a broad overview of AMPs from the origin, structural characteristics, mechanisms of action, biological activities to clinical applications. We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.

Synthesis of Novel Spiro-Tetrahydroquinoline Derivatives and Evaluation of Their Pharmacological Effects on Wound Healing

A highly diastereoselective method for the synthesis of novel spiro-tetrahydroquinoline derivatives is reported here, using a one-pot reaction method. All compounds were characterized by ¹H-nuclear magnetic resonance (NMR) and mass spectroscopy, and their stereo configurations were confirmed by X-ray analysis. These activities of these derivatives were then tested in human keratocyte cells. The responses of cells to treatment with selected compounds were studied using scratch analysis, and the compounds were tested in a mouse excision wound model. Three of the derivatives demonstrated significant wound-healing activities.

Insights into Peptide Mediated Antibiofilm Treatment in Chronic Wound: A Bench to Bedside Approach

Chronic wound biofilm infections are a threat to the population with respect to morbidity and mortality. The presence of multidrug-resistant bacterial pathogens in chronic wound renders the action of antibiotics and antibiofilm agents difficult. Therefore an alternative therapy is essential for reducing bacterial biofilm burden. In this scenario, the peptide-based antibiofilm therapy for chronic wound biofilm management seeks more attention. A synthetic peptide with a broad range of antibiofilm activity against preformed and established biofilms, having the ability to kill multispecies bacteria within biofilms and possessing combinatorial activity with other antimicrobial agents, provides significant insights. In this review, we portray the possibilities and difficulties of peptide-mediated treatment in chronic wounds biofilm management and how it can be clinically translated into a product.

Enzyme-Digested Peptides Derived from Lates calcarifer Enhance Wound Healing after Surgical Incision in a Murine Model

Surgical wounds are common injuries of skin and tissues and usually become a clinical problem. Until now, various synthetic and natural peptides have been widely explored as potential drug candidates for wound healing. Inhibition of the TNF-α signaling pathway and promotion of angiogenesis are suggested to be involved in their effects. Angiogenesis at the wound site is one of the essential requisites for rapid healing. In the present study, a novel peptide extract derived from the natural source Lates calcarifer, commonly known as sea bass or barramundi, was evaluated for its wound healing property. The specific acidic and enzymatic approaches were employed for producing sea bass extract containing small size peptides (molecular weight ranging from 1 kD to 5 kD). The cytotoxicity of the extract was examined in HaCaT and NIH3T3. After this, the effects of enzyme digested peptide extracts of sea bass on wound healing in mice were investigated. The peptide extracts (660 and 1320 mg/kg/day) and control protein (1320 mg/kg/day) was orally given to the wounded mice, respectively, for 12 days. The surgical method was improved by implanting a silicone ring at the wound site. The ring avoided the contracting effect in murine wounds, making it more closely related to a clinical condition. The results showed promising improvement at the wound site in mice. Sea bass peptide extracts accelerated the wound healing process and enhanced the microvessel formation at the wound site. The remarkable effects of this novel sea bass peptide extract in healing traumatic injuries revealed a new option for developing wound management.

Peptide OM-LV20 exerts neuroprotective effects against cerebral ischemia/reperfusion injury in rats

Ischemia/reperfusion (I/R) is a common injury leading to ischemic stroke. At present, I/R treatment remains limited, highlighting the urgent need for the discovery and development of new protective drugs for brain injury. Here, we investigated the neuroprotective effects of short peptide OM-LV20 previously identified from amphibian against I/R rats. Results showed that intraperitoneal administration of OM-LV20 (20 ng/kg) significantly reduced infarct area formation, improved behavioral abnormalities, and protected cortical and hippocampal neurons against death caused by I/R. Moreover, the underlying molecular mechanism was involved with the regulation of the MAPK and BDNF/AKT signaling pathways, as well as the levels of cyclic adenosine monophosphate, pituitary adenylate cyclase-activating polypeptide receptor, and tryptophan hydroxylase 1. To the best of our knowledge, this research was the first report to describe the neuroprotective effects of an amphibian skin secretion-derived peptide in I/R rats and highlighted OM-LV20 as a promising drug candidate for the development of novel anti-stroke therapies.

Discovery of a novel short peptide with efficacy in accelerating the healing of skin wounds

Despite extensive efforts to develop efficacious therapeutic approaches, the treatment of skin wounds remains a considerable clinical challenge. Existing remedies cannot sufficiently meet current needs, so the discovery of novel pro-healing agents is of growing importance. In the current research, we identified a novel short peptide (named RL-QN15, primary sequence 'QNSYADLWCQFHYMC') from Rana limnocharis skin secretions, which accelerated wound healing in mice. Exploration of the underlying mechanisms showed that RL-QN15 activated the MAPK and Smad signaling pathways, and selectively modulated the secretion of cytokines from macrophages. This resulted in the proliferation and migration of skin cells and dynamic regulation of TGF-β1 and TGF-β3 in wounds, which accelerated re-epithelialization and granulation tissue formation and thus skin regeneration. Moreover, RL-QN15 showed significant therapeutic potency against chronic wounds, skin fibrosis, and oral ulcers. Our results highlight frog skin secretions as a potential treasure trove of bioactive peptides with healing activity. The novel peptide (RL-QN15) identified in this research shows considerable capacity as a candidate for the development of novel pro-healing agents.

Peptides from Animal Origin: A Systematic Review on Biological Sources and Effects on Skin Wounds

Background

Skin wounds are closely correlated with opportunistic infections and sepsis risk. Due to the need of more efficient healing drugs, animal peptides are emerging as new molecular platforms to accelerate skin wound closure and to prevent and control bacterial infection.

Aim

The aim of this study was to evaluate the preclinical evidence on the impact of animal peptides on skin wound healing. In addition, we carried out a critical analysis of the studies' methodological quality. Main Methods. This systematic review was performed according to the PRISMA guidelines, using a structured search on the PubMed-Medline, Scopus, and Web of Science platforms to retrieve studies published until August 25, 2020 at 3 : 00 pm. The studies included were limited to those that used animal models, investigated the effect of animal peptides with no association with other compounds on wound healing, and that were published in English. Bias analysis and methodological quality assessments were examined through the SYRCLE's RoB tool.

Results

Thirty studies were identified using the PRISMA workflow. In general, animal peptides were effective in accelerating skin wound healing, especially by increasing cellular proliferation, neoangiogenesis, colagenogenesis, and reepithelialization. Considering standardized methodological quality indicators, we identified a marked heterogeneity in research protocols and a high risk of bias associated with limited characterization of the experimental designs.

Conclusion

Animal peptides show a remarkable healing potential with biotechnological relevance for regenerative medicine. However, rigorous experimental approaches are still required to clearly delimit the mechanisms underlying the healing effects and the risk-benefit ratio attributed to peptide-based treatments.

A New Family of Diverse Skin Peptides from the Microhylid Frog Genus Phrynomantis

A wide range of frogs produce skin poisons composed of bioactive peptides for defence against pathogens, parasites and predators. While several frog families have been thoroughly screened for skin-secreted peptides, others, like the Microhylidae, have remained mostly unexplored. Previous studies of microhylids found no evidence of peptide secretion, suggesting that this defence adaptation was evolutionarily lost. We conducted transcriptome analyses of the skins of Phrynomantis bifasciatus and Phrynomantis microps, two African microhylid species long suspected to be poisonous. Our analyses reveal 17 evolutionary related transcripts that diversified from to those of cytolytic peptides found in other frog families. The 19 peptides predicted to be processed from these transcripts, named phrynomantins, show a striking structural diversity that is distinct from any previously identified frog skin peptide. Functional analyses of five phrynomantins confirm the loss of a cytolytic function and the absence of insecticidal or proinflammatory activity, suggesting that they represent an evolutionary transition to a new, yet unknown function. Our study shows that peptides have been retained in the defence poison of at least one microhylid lineage and encourages research on similarly understudied taxa to further elucidate the diversity and evolution of skin defence molecules.

Accelerated Wound Healing Induced by a Novel Amphibian Peptide (OA-FF10)

BACKGROUND

Despite the continued development of modern medicine, chronic wounds are still a critical issue in clinical treatment, placing a great physiological, psychological, and financial burden on patients. Researchers have investigated many methods to solve this problem, with bioactive peptides gaining increasing attention due to their considerable advantages and diverse functions, as well as low cost, simple storage, and easy transportation.

METHODS

In this research, a novel peptide (named OA-FF10) was identified from the skin secretions of the odorous frog species Odorrana andersonii. The sequence of mature OA-FF10 was "FFTTSCRSGC", which was produced by the post-translational processing of a 61-residue prepropeptide.

RESULTS

Similar to most frog peptides, OA-FF10 showed an intramolecular disulfide bridge at the C-terminus. OA-FF10 demonstrated no antibacterial, antioxidant, hemolytic, or acute toxic activity, but promoted wound healing and proliferation of human keratinocytes (HaCaT) both time- and dose-dependently. Furthermore, while OA-FF10 had no effect on wound healing of Human Skin Fibroblasts (HSF), it did accelerate healing in a full-thickness skin-wound mouse model.

CONCLUSION

Our research revealed the strong wound-healing activity of OA-FF10 in vivo and in vitro, thus providing a new candidate for the development of novel wound-healing drugs.

Effect of Oral Administration of Active Peptides of Pinctada Martensii on the Repair of Skin Wounds

Skin wound healing, especially chronic wound healing, is a common challenging clinical problem. It is urgent to broaden the sources of bioactive substances that can safely and efficiently promote skin wound healing. This study aimed to observe the effects of active peptides (APs) of the mantle of Pinctada martensii on wound healing. After physicochemical analysis of amino acids and mass spectrometry of APs, the effect of APs on promoting healing was studied through a whole cortex wound model on the back of mice for 18 consecutive days. The results showed that APs consisted of polypeptides with molecular weights in the range 302.17–2936.43 Da. The content of polypeptides containing 2–15 amino acids accounted for 73.87%, and the hydrophobic amino acids accounted for 56.51%. Results of in vitro experimentation showed that mice in APs-L group which were fed a low dose of APs (0.5 g/kg bw) had a shortened epithelialization time due to a shortening inflammatory period (p < 0.05). Mechanistically, this relied on its specific ability to promote the proliferation of CD31, FGF and EGF which accelerated the percentage of wound closure. Moreover, the APs-L group mice had enhanced collagen synthesis and increased type III collagen content in their wounds through a TGF-β/Smad signaling pathway (p > 0.05). Consequently, scar formation was inhibited and wound healing efficiency was significantly improved. These results show that the APs of Pinctada martensii promote dermal wound healing in mice and have tremendous potential for development and utilization in skin wound healing.

A Frog-Derived Immunomodulatory Peptide Promotes Cutaneous Wound Healing by Regulating Cellular Response

Wound healing-promoting peptides exhibit excellent therapeutic potential in regenerative medicine. However, amphibian-derived wound healing-promoting peptides and their mechanism of action remain to be further elucidated. We hereby characterized a wound healing-promoting peptide, Ot-WHP, derived from Chinese concave-eared frog Odorrana tormota. It efficiently promoted wound healing in a mouse model of full-thickness wounds. Ot-WHP significantly increased the number of neutrophils in wounds, and modestly promoted neutrophil phagocytosis and phorbol myristate acetate (PMA)-induced neutrophil extracellular trap formation. Ot-WHP also significantly increased the number of macrophages in wound sites, and directly induced chemokine, cytokine and growth factor production in macrophages by activating mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) signaling pathways. Of note, Ot-WHP did not act as a chemoattractant for neutrophils and macrophages, suggesting its chemotactic activity depends on inducing chemoattractant production in macrophages. Besides, Ot-WHP directly promoted keratinocyte migration by enhancing integrin expression and cell adhesion. In addition, Ot-WHP significantly enhanced the cross-talk between macrophages and keratinocytes/fibroblasts by promoting keratinocyte/fibroblast proliferation, and fibroblast-to-myofibroblast transition despite having no direct effects on keratinocyte/fibroblast proliferation, and fibroblast differentiation. Collectively, Ot-WHP directly elicited the production of regulatory factors in macrophages, consequently initiated and accelerated the inflammatory phase by recruiting neutrophils and macrophages to wounds, and in turn enhanced the cross-talk between macrophages and keratinocytes/fibroblasts, additionally promoted keratinocyte migration, and finally promoted cutaneous wound healing. Our findings provide a promising immunomodulator for acute wound management and new clues for understanding the mechanism of action of amphibian-derived wound healing-promoting peptides.

Cloning, Expression and Effects of P. americana Thymosin on Wound Healing

The American cockroach (Periplaneta americana) is a medicinal insect. Its extract is used clinically to promote wound healing and tissue regeneration, but the effective medicinal components and mechanisms are not yet clear. It has been reported that human thymosin beta 4 (Tβ4) may accelerate skin wound healing, however, the role of P. americana thymosin (Pa-THYs) is still poorly understood. In the present study, we identify and analyze the DNA sequences of Pa-THYs by bioinformatics analysis. Then we clone, express, and purify the Pa-THYs proteins and evaluate the activity of recombinant Pa-THYs proteins by cell migration and proliferation assays in NIH/3T3 cells. To elucidate the role of Pa-THYs in wound healing, a mouse model is established, and we evaluate wound contraction, histopathological parameters, and the expressions of several key growth factors after Pa-THYs treatment. Our results showed that three THY variants were formed by skipping splicing of exons. Pa-THYs could promote fibroblast migration, but have no effect on fibroblast proliferation. In wound repair, Pa-THYs proteins could effectively promote wound healing through stimulating dermal tissue regeneration, angiogenesis, and collagen deposition. On the molecular mechanism, Pa-THYs also stimulated the expression of several key growth factors to promote wound healing. The data suggest that Pa-THYs could be a potential drug for promoting wound repair.

A short peptide potentially promotes the healing of skin wound

Skin wound, a common form of skin damage in daily life, remains a serious challenge in clinical treatment. Bioactive peptides with high efficiency have been considered as potential therapeutic candidates for wound healing. In this report, a novel short linear peptide, with mature peptide sequence of 'GLLSGINAEWPC' and no obvious similarity with other known bioactive peptides, was identified by genomic method from the skin of odorous frog, Odorrana andersonii Our results suggested that OA-GL12 (OA: abbreviation of species (O. andersonii), GL: two initial amino acids, 12: peptide length) obviously accelerated the scratch-healing of keratinocytes and human fibroblasts in a time- and concentration-dependent manner. Meanwhile, OA-GL12 showed significant effect in promoting the wound healing on the full-thickness skin wound model. Inflammatory assay results demonstrated that OA-GL12 induced the secretion of tumor necrosis factor (TNF) and transforming growth factor β1 (TGF-β1) on murine macrophage cell line (RAW264.7), which might explain the powerful accelerating capacity of wound healing. Moreover, results also indicated that epidermal growth factor receptor (EGFR) was involved in the mechanisms underlying the scratch-healing promoting activity of OA-GL12. In addition, OA-GL12 showed obvious free radical scavenging activity. Results supported that OA-GL12 did not exert risk in acute toxicity, hemolytic activity, and direct antibacterial activity. The remarkable effect of OA-GL12 on promoting wound healing verified in this research made it potential to be a novel template for the development of wound healing-promoting agents.

Peptides for Skin Protection and Healing in Amphibians

Amphibian skin is not to be considered a mere tegument; it has a multitude of functions related to respiration, osmoregulation, and thermoregulation, thus allowing the individuals to survive and thrive in the terrestrial environment. Moreover, amphibian skin secretions are enriched with several peptides, which defend the skin from environmental and pathogenic insults and exert many other biological effects. In this work, the beneficial effects of amphibian skin peptides are reviewed, in particular their role in speeding up wound healing and in protection from oxidative stress and UV irradiation. A better understanding of why some species seem to resist several environmental insults can help to limit the ongoing amphibian decline through the development of appropriate strategies, particularly against pathologies such as viral and fungal infections.

New Rice-Derived Short Peptide Potently Alleviated Hyperuricemia Induced by Potassium Oxonate in Rats

Gout that caused by hyperuricemia affects human health seriously and more efficient drugs are urgently required clinically. In this study, a novel peptide named RDP1 (AAAAGAKAR, 785.91 Da) was identified from the extract of shelled fruits of Oryza sativa. Our results demonstrated that RDP1 (the minimum effective concentration is 10 μg/kg) could significantly reduce the serum uric acid and creatinine and alleviate hyperuricemic nephropathy in rats by intragastric administration. RDP1 inhibited xanthine oxidase, which also was verified at the animal level. Results from molecular docking indicated that RDP1 can inhibit uric acid formation by occupying the binding site of xanthine oxidase to xanthine. Besides, RDP1 showed no toxicity on rats and was stable in several temperatures, demonstrating its advantages for transportation. This research was the first discovery of antihyperuricemic peptide from the shelled fruits of O. Sativa and provided a new candidate for the development of hypouricemic drugs.

Identification and characterization of a novel gene-encoded antioxidant peptide obtained from amphibian skin secretions

Amphibian skin is known to secrete gene-encoded antioxidant peptides of small molecular weight, which play important roles in host defense. However, recognition of such peptides is still in its infancy. Here, we discovered a novel gene-encoded antioxidant peptide (named OM-GF17) from skin secretions of amphibian species, Odorrana margaretae. Produced by the post-translational processing of a 61-residue prepropeptide, the amino acid sequence of OM-GF17 was 'GFFKWHPRCGEEHSMWT', with a molecular mass of 2135.7 Da. Functional analysis revealed that OM-GF17 scavenged ABTS⁺, DPPH, NO and decreased iron oxidation. Our results also implied that five amino acid residues, including Cys, Pro, Met, Trp, and Phe, be related to the antioxidant activity of OM-GF17. Furthermore, OM-GF17 did not exhibit direct microbe-killing activity. This novel gene-encoded antioxidant peptide could help in the development of new antioxidant agents and increase our understanding of the biological functions of amphibian skin. [Formula: see text].

Identification of β-Sitosterol as in Vitro Anti-Inflammatory Constituent in Moringa oleifera

β-Sitosterol is a well known phytosterol in plants, but owing to its poor solubility in typical media, determining its cellular mechanisms has been proven to be difficult. In this study, we investigated the anti-inflammatory activity of β-sitosterol (BSS) isolated from Moringa oleifera in two cell lines. Over a dose range of 7.5 to 30 μM, BSS dispersed well in the medium as nanoparticles with diameters of 50 ± 5 nm and suppressed the secretion of inflammatory factors from keratinocytes and macrophages induced by PGN, TNF-α, or LPS, such as TNF-α, IL-1β, IL-6, IL-8, and ROS, separately. In addition, BSS significantly reduced the expression of NLRP3, a key component of NLRP3 inflammasomes, and inhibited the activation of caspase-1. There was partial inhibition of NF-κB in macrophages. This is the first study to report an increase in the solubility of nearly water-insoluble phytosterols via the formation of nanoparticles and to delineate the formulation's capacity to inhibit the signal transduction pathways of inflammation in macrophages.

OA-GL21, a novel bioactive peptide from Odorrana andersonii, accelerated the healing of skin wounds

Nowadays, the number of chronic trauma cases caused by a variety of factors such as the world's population-ageing and chronic diseases is increasing steadily, and thus effective treatment for chronic wounds has become a severe clinical challenge, which also burdens the patient both physically and financially. Therefore, it is urgent to develop new drugs to accelerate the healing of wounds. Bioactive peptides, which are relatively low cost, easy to produce, store and transport, have become an excellent choice. In this research, we identified a novel peptide OA-GL21, with an amino acid sequence of 'GLLSGHYGRVVSTQSGHYGRG', from the skin secretions of Odorrana andersonii Our results showed that OA-GL21 exerted the ability to promote wound healing of human keratinocytes (HaCaT) and human fibroblasts in a dose- and time-denpendent manner. However, OA-GL21 had no significant effect on the proliferation of these two cells. Significantly, OA-GL21 showed obvious ability to promote wound healing in the full-thickness skin wound model in dose- and scar-free manners. Further studies showed that OA-GL21 had no direct antibacterial, hemolytic, and acute toxic activity; it had weak antioxidant activities but high stability. In conclusion, this research proved the promoting effects of OA-GL21 on cellular and animal wounds, and thus provided a new peptide template for the development of wound-repairing drugs.

Cathelicidin-OA1, a novel antioxidant peptide identified from an amphibian, accelerates skin wound healing

Cathelicidins play pivotal roles in host defense. The discovery of novel cathelicidins is important research; however, despite the identification of many cathelicidins in vertebrates, few have been reported in amphibians. Here we identified a novel cathelicidin (named cathelicidin-OA1) from the skin of an amphibian species, Odorrana andersonii. Produced by posttranslational processing of a 198-residue prepropeptide, cathelicidin-OA1 presented an amino acid sequence of 'IGRDPTWSHLAASCLKCIFDDLPKTHN' and a molecular mass of 3038.5 Da. Functional analysis showed that, unlike other cathelicidins, cathelicidin-OA1 demonstrated no direct microbe-killing, acute toxicity and hemolytic activity, but did exhibit antioxidant activity. Importantly, cathelicidin-OA1 accelerated wound healing against human keratinocytes (HaCaT) and skin fibroblasts (HSF) in both time- and dose-dependent manners. Notably, cathelicidin-OA1 also showed wound-healing promotion in a mouse model with full-thickness skin wounds, accelerating re-epithelialization and granulation tissue formation by enhancing the recruitment of macrophages to the wound site, inducing HaCaT cell proliferation and HSF cell migration. This is the first cathelicidin identified from an amphibian that shows potent wound-healing activity. These results will help in the development of new types of wound-healing agents and in our understanding of the biological functions of cathelicidins.

Novel SA@Ca2+/RCSPs core–shell structure nanofibers by electrospinning for wound dressings

Therapeutic drugs remain of great significance for the absorption of wound blood, the closure of wounds and rapid wound healing. Hence, we propose a novel composite nanofiber membrane with the above characteristics as a wound healing material. We utilize the reaction of calcium ion and alginate gel, sodium alginate (SA) and Rana chensinensis skin peptides (RCSPs) extracted from discarded Rana chensinensis skin; these two natural substances were successfully used to prepare composite nanofibers by coaxial electrospinning. The composite nanofibers are named SA@Ca²⁺/RCSPs nanofibers. SA@Ca²⁺/RCSPs nanofibers exhibited that the nanofibers contact with the liquid is unmelted, instead become gel, when compared to nanofibers of does not contain calcium ions, and the absorption rate reached 179.87%. SA@Ca²⁺/RCSPs nanofibers conform to the quasi-first-order dynamics model and the Ritger–Peppas release model. In vivo wound healing experiments showed that the wound-healing rate of SA@Ca²⁺/RCSPs nanofiber-treated wounds was 46.65% and 97.46% on days 5 and 15, respectively. In addition, SA@Ca²⁺/RCSPs nanofibers promoted collagen deposition and enhanced epidermal regeneration. The present study showed that composite nanofibers could quickly undergo hemostasis and effectively promote wound healing.

Core–shell nanofiber membranes by coaxial electrospinning process that became gel after absorbing blood were used for wound repair.

The Potential of Frog Skin-Derived Peptides for Development into Therapeutically-Valuable Immunomodulatory Agents

The aim of this article is to review the immunoregulatory actions of frog skin-derived peptides in order to assess their potential as candidates for immunomodulatory or anti-inflammatory therapy. Frog skin peptides with demonstrable immunomodulatory properties have been isolated from skin secretions of a range of species belonging to the families Alytidae, Ascaphidae, Discoglossidae, Leptodactylidae, Pipidae and Ranidae. Their effects upon production of inflammatory and immunoregulatory cytokines by target cells have been evaluated ex vivo and effects upon cytokine expression and immune cell activity have been studied in vivo by flow cytometry after injection into mice. The naturally-occurring peptides and/or their synthetic analogues show complex and variable actions on the production of proinflammatory (TNF-α, IL-1β, IL-12, IL-23, IL-8, IFN-γ and IL-17), pleiotropic (IL-4 and IL-6) and immunosuppressive (IL-10 and TGF-β) cytokines by peripheral and spleen cells, peritoneal cells and/or isolated macrophages. The effects of frenatin 2.1S include enhancement of the activation state and homing capacity of Th1-type lymphocytes and NK cells in the mouse peritoneal cavity, as well as the promotion of their tumoricidal capacities. Overall, the diverse effects of frog skin-derived peptides on the immune system indicate their potential for development into therapeutic agents.