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. Graphical

Individuals with diabetes frequently face serious challenges, including delayed wound healing and increased risk of infection. Notably, the regeneration of hair follicles plays a crucial role in accelerating diabetic skin damage repair, reducing the risk of infection, and enhancing overall skin health. Research has predominantly emphasized the re-epithelialization of diabetic wounds, with a paucity of in-depth studies on hair follicle regeneration. In the current study, we explored the effects of a bioactive amphibian-derived peptide, Cy _RL-QN15, on promoting hair regeneration in a diabetic skin model. In vivo experiments demonstrated that local treatment with Cy _RL-QN15 not only accelerated wound healing of scalded skin on the backs of diabetic Kunming (KM) mice but also improved growth of damaged hair follicles. Additionally, back-shaved diabetic C57BL/6 mice showed a significant increase in the growth of newly formed hair after 28 days of continuous Cy _RL-QN15 treatment. Further analysis indicated that the hair-regenerating effects of Cy _RL-QN15 were closely associated with the proliferation and migration of hair follicle stem cells (HFSCs). Cy _RL-QN15 enhanced intracellular β-catenin expression by binding to the Frizzled-7 receptor on the surface of HFSCs. The up-regulation in β-catenin modulated the levels of downstream proteins, such as c-MYC, Cyclin D1, and Lef1, ultimately inducing hair regeneration. This study not only reveals the robust effects of the bioactive peptide Cy _RL-QN15 in hair follicle regeneration but also provides novel avenues for the development of more targeted and effective therapeutics for diabetic wound healing in the future.

The combined use of peptides, nanomaterials, and hydrogels is a promising strategy for chronic skin wound healing, which remains a huge clinical challenge. Here, we optimized the RL-QN15 peptide, which was shown to be a pro-healing drug candidate in our previous research, to obtain the cyclic heptapeptide (Cy _RL-QN15 ) with considerable therapeutic potency against skin wounds. Furthermore, a Zn ²⁺ -crosslinked sodium alginate (ZA) hydrogel containing hollow polydopamine (HPDA) nanoparticles loaded with Cy _RL-QN15 (HPDAlCy _RL-QN15 /ZA hydrogel) was prepared and characterized, which significantly enhanced the pro-healing potency of Cy _RL-QN15 . At the cellular level, this nontoxic hydrogel accelerated the proliferation, migration, tube formation, and scratch healing of skin cells, regulated the secretion of cytokines from macrophages, directly scavenged free radicals, and decreased reactive oxygen species. Moreover, the HPDAlCy _RL-QN15 /ZA hydrogel significantly accelerated the healing of full-thickness skin wounds in type 2 diabetic mice by promoting the transition of macrophages to the M2 phenotype to reduce inflammation and cause re-epithelialization, formation of granulation tissue, deposition of collagen, and angiogenesis. Of note, the hydrogel also facilitated wound healing of diabetic patient skin cultured ex vivo. Overall, the HPDAlCy _RL-QN15 /ZA hydrogel presents a novel therapeutic strategy for clinical chronic skin wound (diabetic ulcer) healing.

The pursuit of developing groundbreaking pro‐regenerative therapies to expedite skin wound healing persists as a formidable challenge. Peptide RL‐QN15, emerges as a highly promising candidate for the first pro‐regenerative drug derived from amphibian skin, offering a glimmer of hope for innovative healing treatments. Yet, there is an urgent need for intensified research efforts to propel RL‐QN15 from a molecular entity to a viable drug candidate, particularly in unraveling the mechanisms underlying its exceptional pro‐healing efficacy. In the current research, our results revealed that RL‐QN15 significantly enhanced the proliferation, migration, stemness, and epithelial‐to‐mesenchymal transition of human epidermal stem cells (hESCs) through direct binding to the membrane frizzled 8 (FZD8) receptor. This interaction triggers the downstream Wnt/β‐catenin signaling pathway, leading to the up‐regulation of target genes MYC and CCND1. Furthermore, RL‐QN15 augmented the expression and secretion of matrix metalloproteinase‐3, which degrades E‐cadherin and activates the Wnt/β‐catenin pathway, thereby amplifying RL‐QN15's regulatory effects on hESCs. In summary, our findings have demonstrated that RL‐QN15 modulated the functions of ESCs to accelerate skin wound regeneration via the FZD8/β‐catenin axis. This research not only advances peptide RL‐QN15 from a molecular entity to a drug candidate by shedding light on the mechanisms involved with regulation of ESCs functions, but also presents compelling evidence implicating FZD8 as a novel therapeutic target for skin wound regeneration.

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. Graphic

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-1β (IL-1β) 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 β (IKKβ). IKKβ 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/IKKβ/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.