The highest-elevation frog provides insights into mechanisms and evolution of defenses against high UV radiation.

Defense against ultraviolet (UV) radiation exposure is essential for survival, especially in high-elevation species. Although some specific genes involved in UV response have been reported, the full view of UV defense mechanisms remains largely unexplored. Herein, we used integrated approaches to analyze UV responses in the highest-elevation frog, Nanorana parkeri. We show less damage and more efficient antioxidant activity in skin of this frog than those of its lower-elevation relatives after UV exposure. We also reveal genes related to UV defense and a corresponding temporal expression pattern in N. parkeri. Genomic and metabolomic analysis along with large-scale transcriptomic profiling revealed a time-dependent coordinated defense mechanism in N. parkeri. We also identified several microRNAs that play important regulatory roles, especially in decreasing the expression levels of cell cycle genes. Moreover, multiple defense genes (i.e., TYR for melanogenesis) exhibit positive selection with function-enhancing substitutions. Thus, both expression shifts and gene mutations contribute to UV adaptation in N. parkeri. Our work demonstrates a genetic framework for evolution of UV defense in a natural environment.

Peptide RL-QN15 promotes regeneration of epidermal nerve fibers and recovery of sensory function in diabetic skin wounds.

Epidermal nerve fiber regeneration and sensory function are severely impaired in skin wounds of diabetic patients. To date, however, research on post-traumatic nerve regeneration and sensory reconstruction remains scarce, and effective clinical therapeutics are lacking. In the current study, localized treatment with RL-QN15, considered as a drug candidate for intervention in skin wounds in our previous research, accelerated the healing of full-thickness dorsal skin wounds in diabetic mice and footpad skin wounds in diabetic rats. Interestingly, nerve density and axonal plasticity in the skin wounds of diabetic rats and mice, as well as plantar sensitivity in diabetic rats, were markedly enhanced by RL-QN15 treatment. Furthermore, RL-QN15 promoted the proliferation, migration, and axonal length of neuron-like PC12 cells, which was likely associated with activation of the phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt) signaling pathway. The therapeutic effects of RL-QN15 were partially reduced by blocking the PI3K/Akt signaling pathway with the inhibitor LY294002. Thus, RL-QN15 showed positive therapeutic effects on the distribution of epidermal nerve fibers and stimulated the recovery of sensory function after cutaneous injury. This study lays a solid foundation for the development of RL-QN15 peptide-based therapeutics against diabetic skin wounds.

The direct binding of bioactive peptide Andersonin-W1 to TLR4 expedites the healing of diabetic skin wounds.

BACKGROUND: Chronic nonhealing wounds remain a considerable challenge in clinical treatment due to excessive inflammation and impeded reepithelialization and angiogenesis. Therefore, the discovery of novel prohealing agents for chronic skin wounds are urgent and important. Amphibian-derived prohealing peptides, especially immunomodulatory peptides, provide a promising strategy for the treatment of chronic skin trauma. However, the mechanism of immunomodulatory peptides accelerating the skin wound healing remains poorly understood. METHODS: The prohealing ability of peptide Andersonin-W1 (AW1) was assessed by cell scratch, cell proliferation, transwell, and tube formation. Next, full-thickness, deep second-degree burns and diabetic full-thickness skin wounds in mice were performed to detect the therapeutic effects of AW1. Moreover, the tissue regeneration and expression of inflammatory cytokines were evaluated by hematoxylin and eosin (H&E), enzyme-linked immunosorbent assay (ELISA), and immunohistochemistry staining. Molecular docking, colocalization, and western blotting were used to explore the mechanism of AW1 in promoting wound healing. RESULTS: We provide solid evidence to display excellent prohealing effects of AW1, identified as a short antimicrobial peptide in our previous report. At relative low concentration of nM, AW1 promoted the proliferation, migration, and scratch repair of keratinocyte, macrophage proliferation, and tube formation of HUVEC. AW1 also facilitated reepithelialization, granulation regeneration, and angiogenesis, thus significantly boosting the healing of full-thickness, deep second-degree burns and diabetic skin wounds in mice. Mechanistically, in macrophages, AW1 directly bound to Toll-like receptor 4 (TLR4) in the extracellular region and regulated the downstream nuclear factor-κB (NF-κB) signaling pathway to facilitate the inflammatory factor secretion and suppress excessive inflammation induced by lipopolysaccharide (LPS). Moreover, AW1 regulated macrophage polarization to promote the transition from the inflammatory to the proliferative phase and then facilitated reepithelialization, granulation regeneration, and angiogenesis, thus exhibiting excellent therapeutic effects on diabetic skin wounds. CONCLUSIONS: AW1 modulates inflammation and the wound healing process by the TLR4/NF-κB molecular axis, thus facilitating reepithelialization, granulation regeneration, and angiogenesis. These findings not only provided a promising multifunctional prohealing drug candidate for chronic nonhealing skin wounds but also highlighted the unique roles of "small" peptides in the elucidation of "big" human disease mechanisms.

Peptide OM-LV20 protects astrocytes against oxidative stress via the 'PAC1R/JNK/TPH1' axis.

Stroke can lead to severe nerve injury and debilitation, resulting in considerable social and economic burdens. Due to the high complexity of post-injury repair mechanisms, drugs approved for use in stroke are extremely scarce, and thus, the discovery of new antistroke drugs and targets is critical. Tryptophan hydroxylase 1 (TPH1) is involved in a variety of mental and neurobehavioral processes, but its effects on stroke have not yet been reported. Here, we used primary astrocyte culture, quantitative real-time PCR, double immunofluorescence assay, lentiviral infection, cell viability analysis, Western blotting, and other biochemical experiments to explore the protective mechanism of peptide OM-LV20, which previously exhibited neuroprotective effects in rats after ischemic stroke via a mechanism that may involve TPH1. First, we showed that TPH1 was expressed in rat astrocytes. Next, we determined that OM-LV20 impacted expression changes of TPH1 in CTX-TNA2 cells and exhibited a protective effect on the decrease in cell viability and catalase (CAT) levels induced by hydrogen peroxide. Importantly, we also found that TPH1 expression induced by OM-LV20 may be related to the level of change in the pituitary adenylate cyclase-activating peptide type 1 receptor (PAC1R) and to the JNK signaling pathways, thereby exerting a protective effect on astrocytes against oxidative stress. The protective effects of OM-LV20 likely occur via the 'PAC1R/JNK/TPH1' axis, thus highlighting TPH1 as a novel antistroke drug target.

Peptide NCTX15 derived from spider toxin gland effectively relieves hyperuricemia in mice.

Hyperuricemia is a clinical disease characterized by a continuous increase in uric acid (UA) due to purine metabolism disorder. As current drug treatments are limited, it is imperative to explore new drugs that offer better safety and efficacy. In this study, Nephila clavata toxin gland homogenates were isolated and purified by exclusion chromatography and high-performance liquid chromatography, resulting in the identification and isolation of a short peptide (NCTX15) with the sequence 'QSGHTFK'. Analysis showed that NCTX15 exhibited no cytotoxicity in mouse macrophages or toxic and hemolytic activity in mice. Notably, NCTX15 inhibited UA production by down-regulating urate transporter 1 and glucose transporter 9 and up-regulating organic anion transporter 1, thus promoting UA excretion. In addition, NCTX15 alleviated the inflammatory response and renal injury by inhibiting the expression of inflammatory factors interleukin-6, interleukin-1ß, tumor necrosis factor alpha, NLR family, pyrin domain-containing 3, and pyroptosis-related factor gasdermin D. These results indicate that NCTX15 displayed urate-lowering, anti-inflammatory, and analgesic effects. As the first urate-reducing short peptide isolated from a spider toxin gland homogenate, NCTX15 exhibits considerable potential as a novel drug molecule for anti-gout and hyperuricemia treatment.

A short peptide exerts neuroprotective effects on cerebral ischemia-reperfusion injury by reducing inflammation via the miR-6328/IKKß/NF-κB axis.

BACKGROUND: Despite considerable efforts, ischemic stroke (IS) remains a challenging clinical problem. Therefore, the discovery of effective therapeutic and targeted drugs based on the underlying molecular mechanism is crucial for effective IS treatment. METHODS: A cDNA-encoding peptide was cloned from RNA extracted from Rana limnocharis skin, and the mature amino acid sequence was predicted and synthesized. Hemolysis and acute toxicity of the peptide were tested. Furthermore, its neuroprotective properties were evaluated using a middle cerebral artery occlusion/reperfusion (MCAO/R) model in rats and an oxygen-glucose deprivation/reperfusion (OGD/R) model in neuron-like PC12 cells. The underlying molecular mechanisms were explored using microRNA (miRNA) sequencing, quantitative real-time polymerase chain reaction, dual-luciferase reporter gene assay, and western blotting. RESULTS: A new peptide (NP1) with an amino acid sequence of 'FLPAAICLVIKTC' was identified. NP1 showed no obvious toxicities in vivo and in vitro and was able to cross the blood-brain barrier. Intraperitoneal administration of NP1 (10 nmol/kg) effectively reduced the volume of cerebral infarction and relieved neurological dysfunction in MCAO/R model rats. Moreover, NP1 significantly alleviated the decrease in viability and increase in apoptosis of neuron-like PC12 cells induced by OGD/R. NP1 effectively suppressed inflammation by reducing interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) levels in vitro and in vivo. Furthermore, NP1 up-regulated the expression of miR-6328, which, in turn, down-regulated kappa B kinase ß (IKKß). IKKß reduced the phosphorylation of nuclear factor-kappa B p65 (NF-κB p65) and inhibitor of NF-κB (I-κB), thereby inhibiting activation of the NF-κB pathway. CONCLUSIONS: The newly discovered non-toxic peptide NP1 ('FLPAAICLVIKTC') exerted neuroprotective effects on cerebral ischemia-reperfusion injury by reducing inflammation via the miR-6328/IKKß/NF-κB axis. Our findings not only provide an exogenous peptide drug candidate and endogenous small nucleic acid drug candidate but also a new drug target for the treatment of IS. This study highlights the importance of peptides in the development of new drugs, elucidation of pathological mechanisms, and discovery of new drug targets.

Peptide OA-VI12 restrains melanogenesis in B16 cells and C57B/6 mouse ear skin via the miR-122-5p/Mitf/Tyr axis.

Excessive melanogenesis leads to hyperpigmentation, which is one of the common skin conditions in humans. Existing whitening cosmetics cannot meet market needs due to their inherent limitations. Thus, the development of novel skin-whitening agents continues to be a challenge. The peptide OA-VI12 from the skin of amphibians at high altitude has attracted attention due to its remarkable anti light damage activity. However, whether OA-VI12 has the skin-whitening effect of inhibiting melanogenesis is still. Mouse melanoma cells (B16) were used to study the effect of OA-VI12 on cell viability and melanin content. The pigmentation model of C57B/6 mouse ear skin was induced by UVB and treated with OA-VI12. Melanin staining was used to observe the degree of pigmentation. MicroRNA sequencing, quantitative real-time PCR (qRT-PCR), immunofluorescence analysis and Western blot were used to detect the change of factor expression. Double luciferase gene report experiment was used to prove the regulatory relationship between miRNA and target genes. OA-VI12 has no effect on the viability of B16 cells in the concentration range of 1-100 µM and significantly inhibits the melanin content of B16 cells. Topical application of OA-VI12, which exerted transdermal potency, prevented UVB-induced pigmentation of ear skin. MicroRNA sequencing and double luciferase reporter analysis results showed that miR-122-5p, which directly regulated microphthalmia-associated transcription factor (Mitf), had significantly different expression before and after treatment with OA-VI12. Mitf is a simple helix loop and leucine zipper transcription factor that regulates tyrosinase (Tyr) expression by binding to the M-box promoter element of Tyr. qRT-PCR, immunofluorescence analysis and Western blot showed that OA-VI12 up-regulated the expression of miR-122-5p and inhibited the expression of Mitf and Tyr. The effects of OA-VI12 on melanogenesis inhibition in vitro and in vivo may involve the miR-122-5p/Mitf/tyr axis. OA-VI12 represents the first report on a natural amphibian-derived peptide with skin-whitening capacity and the first report of miR-122-5p as a target for regulating melanogenesis, thereby demonstrating its potential as a novel skin-whitening agent and highlighting amphibian-derived peptides as an underdeveloped resource.

A frog peptide provides new strategies for the intervention against skin wound healing.

BACKGROUND: Amphibian derived pro-healing peptides as molecular probes might provide a promising strategy for development of drug candidates and elucidation of cellular and molecular mechanisms of skin wound healing. A novel skin amphibian peptide, OA-RD17, was tested for modulation of cellular and molecular mechanisms associated with skin wound healing. METHODS: Cell scratch, cell proliferation, trans-well, and colony formation assays were used to explore the pro-healing ability of peptide OA-RD17 and microRNA-632 (miR-632). Then, the therapeutic effects of OA-RD17 and miR-632 were assessed in mice, diabetic patient ex vivo skin wounds and SD rats. Moreover, hematoxylin and eosin (H&E), enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, and immunofluorescence staining were performed to detect skin wound tissue regeneration, inflammatory factors expression, and macrophage polarization. Finally, RNA sequencing, molecular docking, co-localization, dual luciferase reporter, real-time quantitative reverse transcription PCR (RT-qPCR), and Western blotting were used to explore the mechanism of OA-RD17 and miR-632 on facilitating skin wound healing. RESULTS: The non-toxic peptide (OA-RD17) promoted macrophage proliferation and migration by activating MAPK and suppressed inflammation by inhibiting NF-κB. In keratinocytes, OA-RD17 inhibited excessive inflammation, and activated MAPK via the Toll-like receptor 4 (TLR4) to promote proliferation and migration, as well as up-regulate the expression of miR-632, which targeted GSK3ß to activate Wnt/ß-catenin to boost proliferation and migration in a positive feedback manner. Notably, OA-RD17 promoted transition from the inflammatory to proliferative stage, accelerated epidermal and granulation regeneration, and exhibited therapeutic effects on mouse and diabetic patient ex vivo skin wounds. MiR-632 activated Wnt/ß-catenin to promote full-thickness skin wound healing in rats. CONCLUSIONS: OA-RD17 exhibited promising therapeutic effects on mice (full-thickness, deep second-degree burns), and ex vivo skin wounds in diabetic patients by regulating macrophages proliferation, migration, and polarization (MAPK, NF-κB), and keratinocytes proliferation and migration (TLR4/MAPK/miR-632/Wnt/ß-catenin molecular axis). Moreover, miR-632 also activated Wnt/ß-catenin to promote full-thickness skin wound healing in rats. Notably, our results indicate that OA-RD17 and miR-632 are promising pro-healing drug candidates.

Role of interleukin-36γ induced by ultraviolet radiation in chronic actinic dermatitis.

BACKGROUND: Chronic actinic dermatitis (CAD) is an immune-mediated photodermatosis characterized by a high eosinophil count and total immunoglobulin E (IgE) in the peripheral blood of patients. At present, however, the reasons for their elevation remain unclear. OBJECTIVE: The current study aimed to detect changes in inflammatory cytokines in CAD and explore their role in this disease. METHODS: Enzyme-linked immunosorbent assay and Luminex assay were conducted to measure inflammatory factor levels. Immunohistochemical analysis and quantitative real-time polymerase chain reaction were performed to evaluate the expression levels of interleukin-36γ (IL-36γ), IL-8, chemokine (C-C motif) ligand 17 (CCL17), and CCL18. CCK8 kits were used to assess cell proliferation. Immunofluorescence was used to detect nuclear factor κB (NF-κB) p65 nuclear translocation. Western blot analysis was performed to detect the protein expression level of phosphorylated NF-κB (p-NF-κB) p65. Hematoxylin and eosin and Masson trichrome staining were applied to observe histological changes in a chronic photo-damaged mouse model. RESULTS: Eosinophils, total IgE, IL-36γ, IL-8, tumor necrosis factor α, CCL17, and CCL18 were elevated in CAD. Of note, IL-36γ promoted the proliferation of eosinophilic cells (EOL-1) and the production of IgE in peripheral blood mononuclear cells. IL-36γ also promoted the production of IL-8 and CCL18 in immortalized human keratinocytes (HaCaT cells), while ultraviolet radiation (UVR)-induced IL-36γ via activation of the NF-κB signaling pathway. CONCLUSIONS: IL-36γ was involved in the pathogenesis of CAD and UVR contributed to the production of IL-36γ, which may provide a novel therapeutic target for CAD.

miR-186-5p targets TGFßR2 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-ß type II receptor (TGFßR2) 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 TGFßR2/Smad2/p38 molecular axes, thus providing a promising new pro-repair drug target.

Peptide OM-LV20 promotes structural and functional recovery of spinal cord injury in rats.

At present, there are no satisfactory therapeutic drugs for the functional recovery of spinal cord injury (SCI). We previously identified a novel peptide (OM-LV20) that accelerated the regeneration of injured skin tissues of mice and exerts neuroprotective effects against cerebral ischemia/reperfusion injury in rats. Here, the intraperitoneal injection of OM-LV20 (1 µg/kg) markedly improved motor function recovery in the hind limbs of rats with traumatic SCI, and further enhanced spinal cord repair. Administration of OM-LV20 increased the number of surviving neuron bodies, as well as the expression levels of brain-derived neurotrophic factor (BDNF) and its receptor tyrosine receptor kinase B (TrkB). In the acute stage of SCI, OM-LV20 treatment also increased superoxide dismutase and glutathione content but decreased the levels of malonaldehyde and nitric oxide. Thus, OM-LV20 significantly promoted structural and functional recovery of SCI in adult rats by increasing neuronal survival and BDNF and TrkB expression, and thereby regulating the balance of oxidative stress. Based on our knowledge, this research is the first report on the effects of amphibian-derived peptide on the recovery of SCI and our results highlight the potential of peptide OM-LV20 administration in the acceleration of the recovery of SCI.

Scorpion venom peptide HsTx2 suppressed PTZ-induced seizures in mice via the circ_0001293/miR-8114/TGF-ß2 axis.

BACKGROUND: Due to the complexity of the mechanisms involved in epileptogenesis, the available antiseizure drugs (ASDs) do not meet clinical needs; hence, both the discovery of new ASDs and the elucidation of novel molecular mechanisms are very important. METHODS: BALB/c mice were utilized to establish an epilepsy model induced by pentylenetetrazol (PTZ) administration. The peptide HsTx2 was administered for treatment. Primary astrocyte culture, immunofluorescence staining, RNA sequencing, identification and quantification of mouse circRNAs, cell transfection, bioinformatics and luciferase reporter analyses, enzyme-linked immunosorbent assay, RNA extraction and reverse transcription-quantitative PCR, Western blot and cell viability assays were used to explore the potential mechanism of HsTx2 via the circ_0001293/miR-8114/TGF-ß2 axis. RESULTS: The scorpion venom peptide HsTx2 showed an anti-epilepsy effect, reduced the inflammatory response, and improved the circular RNA circ_0001293 expression decrease caused by PTZ in the mouse brain. Mechanistically, in astrocytes, circ_0001293 acted as a sponge of endogenous microRNA-8114 (miR-8114), which targets transforming growth factor-beta 2 (TGF-ß2). The knockdown of circ_0001293, overexpression of miR-8114, and downregulation of TGF-ß2 all reversed the anti-inflammatory effects and the influence of HsTx2 on the MAPK and NF-κB signaling pathways in astrocytes. Moreover, both circ_0001293 knockdown and miR-8114 overexpression reversed the beneficial effects of HsTx2 on inflammation, epilepsy progression, and the MAPK and NF-κB signaling pathways in vivo. CONCLUSIONS: HsTx2 suppressed PTZ-induced epilepsy by ameliorating inflammation in astrocytes via the circ_0001293/miR-8114/TGF-ß2 axis. Our results emphasized that the use of exogenous peptide molecular probes as a novel type of ASD, as well as to explore the novel endogenous noncoding RNA-mediated mechanisms of epilepsy, might be a promising research area.

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.

Novel scorpion venom peptide HsTx2 ameliorates cerebral ischemic brain injury in rats via the MAPK signaling pathway.

Ischemic stroke is a severe threat to human health due to its high recurrence, mortality, and disability rates. As such, how to prevent and treat ischemic stroke effectively has become a research hotspot in recent years. Here, we identified a novel peptide, named HsTx2 (AGKKERAGSRRTKIVMLKCIREHGH, 2 861.855 Da), derived from the scorpion Heterometrus spinifer, which showed obvious anti-apoplectic effects in rats with ischemic stroke. Results further demonstrated that HsTx2 significantly reduced formation of infarct area and improved behavioral abnormalities in ischemic stroke rats. These protective effects were likely exerted via activation of the mitogen-activated protein kinase (MAPK) signaling pathway, i.e., up-regulation of phosphorylated ERK1/2 in both rat cerebral cortex and activated microglia (AM); up-regulation of phosphorylated p38 (p-p38) in the cerebral cortex; and inhibition of phosphorylated JNK and p-p38 levels in the AM. In conclusion, this study highlights HsTx2 as a potential neuroprotective agent for stroke.

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-ß1 and TGF-ß3 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.

The beneficial roles of poisonous skin secretions in survival strategies of the odorous frog Odorrana andersonii.

The evolution of predatory, anti-predatory, and defensive strategies regarding environmental adaptation in animals is of significant research interest. In particular, amphibians, who represent a transition between aquatic and terrestrial vertebrates, play an important role in animal evolution. The bioactive skin secretions of amphibians are of specific interest due to their involvement in the crucial physiological functions of amphibian skin. We previously isolated and identified several bioactive peptides, including those showing antioxidant, antimicrobial, and wound-healing properties, from the skin secretions of the odorous frog species Odorrana andersonii. Currently, however, the biological significance of skin secretions in O. andersonii survival remains unclear. Here, we studied the biological significance of skin glands and secretions in regard to environmental adaptations of O. andersonii. Our research found that O. andersonii may secrete and excrete bioactive secretions through many glands (peptides and proteins as the main components in glands) distributed in the skin. The skin secretions not only displayed toxicity but also showed antioxidant, antibacterial, and repair promoting activities, suggesting that they play a protective role in O. andersonii when facing environmental threats. These bioactive skin secretions appear to act as a chemical survival strategy in O. andersonii, allowing the species to gain advantages in survival behavior.

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.

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.

Centipede venom peptide SsmTX-I with two intramolecular disulfide bonds shows analgesic activities in animal models.

Pain is a major symptom of many diseases and results in enormous pressures on human body or society. Currently, clinically used analgesic drugs, including opioids and nonsteroidal anti-inflammatory drugs, have adverse reactions, and thus, the development of new types of analgesic drug candidates is urgently needed. Animal venom peptides have proven to have potential as new types of analgesic medicine. In this research, we describe the isolation and characterization of an analgesic peptide from the crude venom of centipede, Scolopendra subspinipes mutilans. The amino acid sequence of this peptide was identical with SsmTX-I that was previously reported as a specific Kv2.1 ion channel blocker. Our results revealed that SsmTX-I was produced by posttranslational processing of a 73-residue prepropeptide. The intramolecular disulfide bridge motifs of SsmTX-I was Cys1-Cys3 and Cys2-Cys4. Functional assay revealed that SsmTX-I showed potential analgesic activities in formalin-induced paw licking, thermal pain, and acetic acid-induced abdominal writhing mice models. Our research provides the first report of cDNA sequences, disulfide motif, successful synthesis, and analgesic potential of SsmTX-I for the development of pain-killing drugs. It indicates that centipede peptide toxins could be a treasure trove for the search of novel analgesic drug candidates. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Characterization of an insulinotropic peptide from skin secretions of Odorrana andersonii.

Insulinotropic peptide agents are regarded as potential candidates for anti-diabetic treatment. In the present study, a novel insulinotropic peptide, termed OA-A1, was purified from frog skin secretions of Odorrana andersonii. Mature OA-A1 was determined to be a 1965.049 Da peptide with an amino acid sequence of LVGKLLKGAVGDVCGLLPIC, in which an intramolecular disulfide bridge was formed by two cysteine residues. At the cellular level, OA-A1 exhibited potent proliferation promoting effects on mouse-derived pancreatic ß-TC-6 cells and significantly stimulated insulin release in ß-TC-6 cells at a minimum concentration of 1 nM. In the animal model, OA-A1 also showed a dose-dependent insulin-releasing role in mice. At concentrations ranging from 1 nmol/kg to 1 µmol/kg, OA-A1 had a significant acute hypoglycemic effect on streptozotocin (STZ)-induced diabetic mice. The pancreatic islet areas of diabetic mice increased dose-dependently after 21 days of OA-A1 treatment (1-100 nmol/kg) compared with those of the saline control group. Moreover, OA-A1 significantly improved the oral glucose tolerance of STZ-induced diabetic mice. Taken together, these results suggest that OA-A1 provides an excellent template for the development of novel anti-diabetic therapeutic agents. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.