A Selectable Biomarker in Hair Follicle Cycles - Cathepsins: A Preliminary Study in Murine.

BACKGROUND/OBJECTIVE: Hair cycle is regulated by many biological factors. Cathepsins are involved in various physiological processes in human skin. Here, we investigated the cathepsin expression and distribution changes in follicular growth cycles for better understanding the hair cycles and to explore new intervention measures. METHODS: The 24 mice (C57BL/6, female, 7-week old) were selected and removed the back hair via rosin/paraffin method. At Day 8, Day 20, and Day 25, biopsy on post-plucking area was done. Immunohistochemical staining, Western blot, and Q-PCR were used to test the cathepsin B/D/L/E. RESULTS: In anagen, cathepsins (B, D, L, and E) were distributed in the hair follicle matrix, inner hair root sheath, and hair. In catagen, cathepsins were mainly observed in un-apoptosis inner root sheath and outer root sheath. Expression of cathepsins B-mRNA and L-mRNA was decreased from anagen and catagen to telogen. Cathepsin D-mRNA was increased in catagen and then decreased in telogen. Cathepsin E-mRNA was decreased in catagen and slightly increased in telogen. CONCLUSIONS: The distribution and expression of cathepsins B, D, L, and E in hair follicle changed with hair growth process which indicated that cathepsins might act as selectable biomarkers of hair cycle in different stages.

Differential gene expression in HaCaT cells may account for the various clinical presentation caused by anthropophilic and geophilic dermatophytes infections.

BACKGROUND: Despite the worldwide prevalence of dermatophyte infections, only a few genes are reported to be related to dermatophyte infections. In addition, the mechanism by which different ecological dermatophytes infection leads to varying intensity of inflammation remains unclear. OBJECTIVES: To investigate the mechanism of varying intensity of skin inflammation caused by different ecological dermatophytes infection. METHODS: We infected HaCaT cells with anthropophilic and geophilic dermatophytes to mimic various ecological dermatophyte infections. RNA-sequencing (RNA-seq) was employed to identify the change in the gene expression of HaCaT cells. To verify the expression of differentially expressed genes (DEGs), we selected 18 HaCaT cells genes to conduct qPCR experiments. In addition, immunoblotting was conducted to validate key genes from the MAPK signalling pathway. RESULTS: After HaCaT cells were infected with the anthropophilic Trichophyton rubrum (T rubrum) and the geophilic Microsporum gypseum (M gypseum), 118 and 619 differentially expressed genes were identified in HaCaT cells, respectively. These genes may provide a clue as to how keratinocytes respond to anthropophilic and geophilic dermatophytes. We also found that JUN may play a critical role in keratinocytes infected with M gypseum. CONCLUSIONS: Differential gene expression in HaCaT cells may account for the various clinical presentation caused by anthropophilic and geophilic dermatophytes infections. In addition, the intense inflammatory reaction of M gypseum infection may be triggered by activating the JNK-JUN signalling pathway.

Expression Profiles of Long Noncoding RNA in UVA-Induced Human Skin Fibroblasts.

BACKGROUND: Long noncoding RNA (lncRNA) are differentially expressed across stages of differentiation and development, but the role of lncRNA in human skin photoaging mechanisms remains poorly understood. OBJECTIVE: This study aimed to determine lncRNA expression changes in human dermal fibroblasts (HDF) induced by repeated UVA irradiation and to explore correlations between lncRNA and skin photoaging prognosis. METHODS: In the UVA-HDF group, HDF were subjected to repeated UVA irradiation (10 J/cm2 UVA twice daily for 7 days); in the control group, HDF received no irradiation. High-throughput sequencing was used to detect lncRNA expression profiles. Functional annotation analysis and pathway enrichment were preformed via Gene Ontology and KEGG. Predicted lncRNA target genes were identified by bioinformatic analysis. RESULTS: In the UVA-HDF group, 1,730 lncRNA exhibited over 2-fold expression changes compared with the control group: 1,494 were upregulated, and 236 downregulated. Predicted lncRNA targets were associated with matrix metalloproteinases, cathepsin D, mitogen-activated protein kinase and TGF-ß signaling pathways, and collagen fiber metabolism following repeated UVA damaging mechanisms. CONCLUSIONS: lncRNA profiles were aberrantly expressed in UVA-HDF and might play a key role in skin photoaging. This study provides novel insights into the repeated UVA-damaging pathology and potential targets for treatment of human skin photoaging.

Novel Genes Related to Ceftriaxone Resistance Found among Ceftriaxone-Resistant Neisseria gonorrhoeae Strains Selected In Vitro.

The emergence of ceftriaxone-resistantNeisseria gonorrhoeaeis currently a global public health concern. However, the mechanism of ceftriaxone resistance is not yet fully understood. To investigate the potential genes related to ceftriaxone resistance inNeisseria gonorrhoeae, we subcultured six gonococcal strains with increasing concentrations of ceftriaxone and isolated the strains that became resistant. After analyzing several frequently reported genes involved in ceftriaxone resistance, we found only a single mutation inpenA(A501V). However, differential analysis of the genomes and transcriptomes between pre- and postselection strains revealed many other mutated genes as well as up- and downregulated genes. Transformation of the mutatedpenAgene into nonresistant strains increased the MIC between 2.0- and 5.3-fold, and transformation of mutatedftsXincreased the MIC between 3.3- and 13.3-fold. Genes encoding the ABC transporters FarB, Tfq, Hfq, and ExbB were overexpressed, whilepilM,pilN, andpilQwere downregulated. Furthermore, the resistant strain developed cross-resistance to penicillin and cefuroxime, had an increased biochemical metabolic rate, and presented fitness defects such as prolonged growth time and downregulated PilMNQ. In conclusion, antimicrobial pressure could result in the emergence of ceftriaxone resistance, and the evolution of resistance ofNeisseria gonorrhoeaeto ceftriaxone is a complicated process at both the pretranscriptional and posttranscriptional levels, involving several resistance mechanisms of increased efflux and decreased entry.

"Abraxane-Like" Radiosensitizer for In Situ Oral Cancer Therapy.

Radiotherapy plays a vital role in cancer therapy. However, the hypoxic microenvironment of tumors greatly limits the effectiveness, thus it is crucial to develop a simple, efficient, and safe radiosensitizer to reverse hypoxia and ameliorate the efficacy of radiotherapy. Inspired by the structure of canonical nanodrug Abraxane, herein, a native HSA-modified CaO2 nanoparticle system (CaO2-HSA) prepared by biomineralization-induced self-assembly is developed. CaO2-HSA will accumulate in tumor tissue and decompose to produce oxygen, altering the hypoxic condition inside the tumor. Simultaneously, ROS and calcium ions will lead to calcium overload and further trigger immunogenic cell death. Notably, its sensitizing enhancement ratio (SER = 3.47) is much higher than that of sodium glycididazole used in the clinic. Furthermore, in animal models of in situ oral cancer, CaO2-HSA can effectively inhibit tumor growth. With its high efficacy, facile preparation, and heavy-metal free biosafety, the CaO2-HSA-based radiosensitizer holds enormous potential for oral cancer therapy.

Combined mutations of the penA with ftsX genes contribute to ceftriaxone resistance in Neisseria gonorrhoeae and peptide nucleic acids targeting these genes reverse ceftriaxone resistance.

OBJECTIVES: To investigate the gene mutations associated with ceftriaxone (CRO) resistance among gonococcal isolates, and to determine the effects of the mutated genes on CRO minimum inhibitory concentrations (MICs) with transformation assays and antisense peptide nucleic acids (asPNAs). METHODS: Ceftriaxone-resistant (CROR) and ceftriaxone-susceptible (CROS) isolates were identified using EUCAST and paired according to similarity in their MICs to other antimicrobials. The two groups of gonococci were sequenced and analysed. Mutated genes that showed a statistical difference between the two groups were transformed into gonococcal reference strains to determine their functions. AsPNAs were designed and transformed into the former transformant to further confirm the effects of the mutated genes. RESULTS: Twenty-two paired CROR and CROS isolates were obtained. The incidence of the penA-A501T and penA-G542S mutations individually, as well as combined mutations (penA-A501T and ftsX-R251H, penA-G542S and ftsX R251H), was statistically different between the two groups. The MIC of ATCC43069 (A43) increased 2 times following transformation with penA-A501T, and the MICs of A43 and ATCC49226 (A49) increased 32 times and 2 times following transformation with penA-A501T and ftsX-R251H, respectively. Antisense PNA-P3 reduced the MIC of the A43 transformant most significantly when transformed individually. PNA-P3 and PNA-F1 (asPNAs of the penA and ftsX) restored CRO susceptibility. CONCLUSIONS: PenA-A501T and penA-G542S mutations are important in CRO resistance among gonococci isolates. The ftsX-R251H mutation is also related to CRO resistance, and combined mutations of ftsX-R251H and penA-A501T comediate a significant reduction in CRO susceptibility. The combined application of PNA-P3 and PNA-F1 could effectively reverse the resistance to CRO in N. gonorrhoeae.

A Zinc- and Calcium-Rich Lysosomal Nanoreactor Rescues Monocyte/Macrophage Dysfunction under Sepsis.

Sepsis is a dysregulation of the immune response to pathogens and has high morbidity and mortality worldwide. However, the unclear mapping and course of dysregulated immune cells currently hinders the development of advanced therapeutic strategies to treat sepsis. Here, evidence is provided using single-cell RNA sequencing from peripheral blood mononuclear cells in sepsis that pathogens attacking monocytes/macrophages disrupt their immune function. The results reveal an enormous decline in monocytes/macrophages in sepsis and chart the evolution of their impaired phagocytosis (Pha) capabilities. Inspired by these findings, nanoparticles, named "Alpha-MOFs," are developed that target dysfunctional monocytes/macrophages to actively (A) lift (L) Pha by the release of lysosome-sensitive ions from a mineralized metal-organic framework (MOF). Alpha-MOFs have good stability and biosafety in peripheral blood and efficiently targeted monocytes/macrophages. They also release calcium and zinc ions into monocyte/macrophage lysosomes to promote the Pha and degradation of bacteria. Taken together, these results suggest that Alpha-MOFs rescue monocytes/macrophages dysfunction and effectively improve their survival rate during sepsis.

Neuro-Inspired Biomimetic Microreactor for Sensory Recovery and Hair Follicle Neogenesis under Skin Burns.

Deep burns are one of the most severe skin wounds, with typical symptoms being a contradiction between initial severe pain and a subsequent loss of sensation. Although it has long been known that sensory nerves promote skin regeneration and modulate skin function, no proven burn management strategies target sensory nerves. Here, a neuro-inspired biomimetic microreactor is designed based on the immune escape outer membrane of neuroblastoma cells and neural-associated intracellular proteins. The microreactor is constructed on a metal-organic framework (MOF) with a neuroblastoma membrane coating the surface and intracellular proteins loaded inside, called Neuro-MOF. It is loaded into a therapeutic hydrogel and triggers the release of its content proteins upon excitation by near-infrared light. The proteins compensate the skin microenvironment for permanent neurological damage after burns to initiate peripheral nerve regeneration and hair follicle niche formation. In addition, the neuroblastoma cell membrane is displayed on the surface of the Neuro-MOF microreactor, decreasing its immunogenicity and suppressing local inflammation. In a mouse model of deep skin burns, the Neuro-MOF microreactor exhibited significant functional skin regeneration effects, particularly sensory recovery and hair follicle neogenesis.

Ectopic Expression of MADS-Box Transcription Factor VvAGL12 from Grape Promotes Early Flowering, Plant Growth, and Production by Regulating Cell-Wall Architecture in Arabidopsis.

The MADS-box family, a substantial group of plant transcription factors, crucially regulates plant growth and development. Although the functions of AGL12-like subgroups have been elucidated in Arabidopsis, rice, and walnut, their roles in grapes remain unexplored. In this study, we isolated VvAGL12, a member of the grape MADS-box group, and investigated its impact on plant growth and biomass production. VvAGL12 was found to localize in the nucleus and exhibit expression in both vegetative and reproductive organs. We introduced VvAGL12 into Arabidopsis thaliana ecotype Columbia-0 and an agl12 mutant. The resulting phenotypes in the agl12 mutant, complementary line, and overexpressed line underscored VvAGL12's ability to promote early flowering, augment plant growth, and enhance production. This was evident from the improved fresh weight, root length, plant height, and seed production, as well as the reduced flowering time. Subsequent transcriptome analysis revealed significant alterations in the expression of genes associated with cell-wall modification and flowering in the transgenic plants. In summary, the findings highlight VvAGL12's pivotal role in the regulation of flowering timing, overall plant growth, and development. This study offers valuable insights, serving as a reference for understanding the influence of the VvAGL12 gene in other plant species and addressing yield-related challenges.

CD301b+ Macrophages as Potential Target to Improve Orthodontic Treatment under Mild Inflammation.

Due to improvements of quality of life and the demand for aesthetics, more and more people are choosing orthodontic treatments, resulting in a surge in adult orthodontic patients in recent years. However, a large amount of clinical evidence shows that many orthodontic patients have mild periodontitis in the periodontal tissues, which affects the efficacy of the orthodontic treatment or aggravates the periodontal condition. Therefore, it is important to identify the key factors that affect orthodontic treatments in this inflammatory environment. The aim of this study was to investigate the role of macrophages in orthodontic treatments under inflammatory environments. By analyzing the functional groups of macrophages in the orthodontic rat model of periodontitis, we found that macrophages with high expression levels of CD301b could improve the periodontal microenvironment and improve the efficiency of the orthodontic tooth movement. CD301b+ macrophages transplanted into the model can promote osteogenesis around orthodontic moving teeth, improve bone remodeling during orthodontic treatment, and accelerate orthodontic tooth movement. Considered together, these results suggest that CD301b+ macrophages may play an active role in orthodontic treatments in inflammatory environments and may serve as potential regulatory targets.

CD301b+ macrophages mediate angiogenesis of calcium phosphate bioceramics by CaN/NFATc1/VEGF axis.

Calcium phosphate (CaP) bioceramics are important for tissue regeneration and immune response, yet how CaP bioceramics influence these biological processes remains unclear. Recently, the role of immune cells in biomaterial-mediated regeneration, especially macrophages, has been well concerned. CD301b+ macrophages were a new subset of macrophages we have discovered, which were required for bioceramics-mediated bone regeneration. Nevertheless, the impact of CD301b+ macrophages on angiogenesis, which is a vital prerequisite to bone formation is yet indistinct. Herein, we found that CD301b+ macrophages were closely correlated to angiogenesis of CaP bioceramics. Additionally, depletion of CD301b+ macrophages led to the failure of angiogenesis. We showed that store-operated Ca2+ entry and calcineurin signals regulated the VEGF expression of CD301b+ macrophages via the NFATc1/VEGF axis. Inhibition of calcineurin effectively impaired angiogenesis via decreasing the infiltration of CD301b+ macrophages. These findings provided a potential immunomodulatory strategy to optimize the integration of angiogenesis and bone tissue engineering scaffold materials.

A KRAS-Associated Signature for Prognostic, Immune and Chemical Anti-Cancer Drug-Response Prediction in Colon Cancer.

Background: KRAS mutation, one of the most important biological processes in colorectal cancer, leads to poor prognosis in patients. Although studies on KRAS have concentrated for a long time, there are currently no ideal drugs against KRAS mutations. Methods: Different expression analysis and weighted gene coexpression network analysis was conducted to select candidate genes. Log-rank tests and Cox regression picked out the prognostic genes to build a KRAS-related gene prognostic score (KRGPS). A nomogram based on KRGPS was built to predict survival of clinical patients. Comprehensive analysis showed the prognosis, immune microenvironment and response to immune therapy and chemotherapy in KRGPS subgroups. Results: We collected a KRGPS from the set of two genes GJB6 and NTNG1, with low-KRGSP patients having better progression-free survival (PFS). Low KRGPS is correlated with high infiltration of activated NK cells, plasma cells and activated memory CD4 T cells and that these cells benefit more from immune checkpoint inhibitor therapy. However, high KRGPS is associated with high infiltration of activated mast cells, pathways of immune dysregulation and a high ratio of TP53 and KRAS mutations. KRGPS subgroups are also sensitive to chemotherapy differently. A nomogram, established based on the KRGPS and pathological stage, predict 3- and 5-years PFS well. Conclusions: The KRAS-associated score acts as a promising signature to distinguish prognosis, molecular and immune characteristics, and benefits from immune and chemical therapy. These KRAS-associated genes could be promising targets for drug design.

Preparation, characterization and biological properties of a novel bone block composed of platelet rich fibrin and a deproteinized bovine bone mineral.

Alveolar bone defects caused by tooth loss often lead to challenges in implant dentistry, with a need for development of optimal bone biomaterials to predictably rebuild these tissues. To address this problem, we fabricated a novel bone block using platelet-rich fibrin (PRF) and Deproteinized Bovine Bone Mineral (DBBM), and characterized their mechanical and biological properties. The bone block was prepared by mixing DBBM, Liquid-PRF, and Solid-PRF fragments in various combinations as follows: (1) BLOCK-1 made with Solid-PRF fragments + DBBM, (2) BLOCK-2 made with Liquid-PRF + DBBM, (3) BLOCK-3 made with Solid-PRF fragments + Liquid-PRF + DBBM. The time for solidification and the degradation properties were subsequently recorded. Scanning electron microscopy (SEM) and tensile tests were carried out to investigate the microstructure and mechanical properties of each block. The bioactivity of the three groups towards osteoblast differentiation was also evaluated by culturing cells with the conditioned medium from each of the three groups including cell proliferation assay, cell migration assay, alkaline phosphatase (ALP) staining, and alizarin red staining (ARS), as well as by real-time PCR for genes encoding runt-related transcription factor 2 (RUNX2), ALP, collagen type I alpha1(COL1A1) and osteocalcin (OCN). BLOCK-3 made with Solid-PRF fragments + Liquid-PRF + DBBM had by far the fastest solidification period (over a 10-fold increase) as well as the most resistance to degradation. SEM and tensile tests also revealed that the mechanical properties of BLOCK-3 were superior in strength when compared to all other groups and further induced the highest osteoblast migration and osteogenic differentiation confirmed by ALP, ARS and real-time PCR. PRF bone blocks made through the combination of Solid-PRF fragments + Liquid-PRF + DBBM had the greatest mechanical and biological properties when compared to either used alone. Future clinical studies are warranted to further support the clinical application of PRF bone blocks in bone regeneration procedures.

Inflammation and Vascular Injury as the Basis of COVID-19 Skin Changes: Preliminary Analysis of 23 Patients from the Literature.

BACKGROUND: COVID-19 can affect various organ systems including the skin. Cutaneous manifestations of COVID-19 in infected patients are poorly characterized. OBJECTIVE: To summarize retrospectively the skin features of COVID-19 infection and to analyze the skin rash incidence rate, clinical onset time, cutaneous manifestations, pathological characteristics and relationship with the novel coronavirus pneumonia severity. METHODS: The literature up to Sep 20, 2020, were searched and analyzed. Information on clinical features including skin manifestations, disease severity, stage and onset day, and cutaneous pathological characteristics was extracted. Data were analyzed using descriptive non-parametric statistics. For categorical data, the number and percentage of patients are presented. A Spearman correlation test was used to analyze the associations between rash type, rash onset and severity of COVID-19. All statistical analysis was performed with IBM SPSS software (version 20) using two-tailed tests. P values <0.05 were considered statistically significant. RESULTS: Twenty-three cases of COVID-19 patients with cutaneous manifestations from seven reports were collected. Inflammatory dermatosis, skin vasculitis and vascular dermatosis were the main lesion types of COVID-19 patients. Microvascular and endothelial cell injury, perivascular lymphocytic infiltrate, thrombosis, extremely dilated vessels and prominent deposits of C5b-9 were the main dermatologic pathological changes. The onset day analysis showed that out of 19 patients, 63.2% of cutaneous manifestations were within 10 days, 21.1% in 10-20 days and 15.8% were 20 days after the time the patient presented with COVID-19 main symptoms. Spearman rho analysis found no correlation between skin rash type, onset day and COVID-19 severity. CONCLUSION: COVID-19 induced skin changes are one of the manifestations of immune responses to the novel coronavirus. Clinical and pathological characteristics were identified as dermal inflammatory reactions and/or skin vascular injury. External or systematic use of anti-inflammatories, protection of blood vessels and circulation-improving medicines should be considered in the skin treatments for novel coronavirus pneumonia patients.

Characterisation of a novel peptide, Brevinin-1H, from the skin secretion of Amolops hainanensis and rational design of several analogues.

As drug-resistant bacteria have become a serious health problem and have caused thousands of deaths, finding new antibiotics has become an urgent research priority. A novel antimicrobial peptide, named Brevinin-1H, was identified in the skin secretion of Amolops hainanensis through 'shotgun' cloning. It has broad-spectrum antimicrobial activity against tested micro-organisms and has anticancer cell activity. To improve its bioactivity and decrease its cytotoxicity, two structural analogues-Brevinin-1Ha and Brevinin-1HY-were designed based on the secondary structure of the natural peptide. Brevinin-1HY, in which tyrosine substituted Pro11 , had similar activity to the natural peptide against Gram-negative bacteria and cancer cells, but showed a dramatic increase in haemolytic activity and cytotoxicity at its minimum inhibitory concentration. Brevinin-1Ha, which transferred the Rana-box from the C-terminal to a central position, had significantly decreased haemolytic activity, but also in antimicrobial and anticancer activity. The present data suggest that increasing the proportion of α-helix structure in an AMP can increase its target micro-organism bioactivity to some extent.

Target Reprogramming Lysosomes of CD8+ T Cells by a Mineralized Metal-Organic Framework for Cancer Immunotherapy.

T cell immunotherapy holds significant challenges in solid tumors, mainly due to the T cells' low activation and the decreased synthesis-release of therapeutic proteins, including perforin and granzyme B, which are present in lysosomes. In this study, a lysosome-targeting nanoparticle (LYS-NP) is developed by way of a mineralized metal-organic framework (MOF) coupled with a lysosome-targeting aptamer (CD63-aptamer) to enhance the antitumor effect of T cells. The MOF synthesized from Zn2+ and dimethylimidazole has good protein encapsulation and acid sensitivity, and is thus an ideal lysosomal delivery vector. Calcium carbonate (CaCO3 ) is used to induce MOF mineralization, improve the composite material's stability in encapsulating therapeutic protein, and provide calcium ions with synergistic effects. Before mineralization, perforin and granzyme B-T cell-needed therapeutic proteins for tumors-are preloaded with the MOF. Moreover, T cells are pretreated with processed tumor-specific antigens to activate or produce memory before reprogramming the lysosomes, facilitating the T cell receptor (TCR) for release of the therapeutic proteins. Using T cells recombined by LYS-NPs, a significant enhancement of breast cancer control is confirmed.

Crafting Mixed Sexual Advertisements for Mainstream Media: Examining the Impact of Homosexual and Heterosexual Imagery Inclusion on Advertising Effectiveness.

This research applied both qualitative and quantitative methods to measure the effectiveness of mixed sexual advertisements that explicitly feature both homosexual and heterosexual models within the same message. Drawing on theoretical framework of social identity theory, this study predict mixed sexual advertisements could create a perceptual social categorization that includes both homosexual and heterosexual identities and reduces intergroup competitions between homosexual and heterosexual viewers. Results indicate that mixed sexual advertisements elicit better ad evaluation than strictly gay-themed advertisements when evaluated by a mix of homosexual and heterosexual participants. The findings suggest mixed sexual advertisements could balance between homosexual-themed advertising and gay window advertising by addressing homosexual audiences without alienating heterosexual viewers.

Identification of Transcription Factor/Gene Axis in Colon Cancer Using a Methylome Approach.

Colon cancer is one of the most commonly diagnosed cancers worldwide. Both environmental and molecular characters can influence its development. DNA methylation has been heralded as a promising marker for use in cancer prevention, diagnosis, and treatment. It has been shown to facilitate cancer progression through multiple mechanisms. Changes in DNA methylation can inhibit or promote the binding of transcription factors (TFs) and further disturb gene regulation. Detection of DNA methylation-mediated regulatory events in colon cancer are critical for mining novel biomarkers. Here, we explore the influence of CpG sites located at promoter regions of differentially expressed genes and identify methylation-gene relationships using expression-methylation quantitative trait loci. We find that promoter methylation sites mainly negatively regulate the corresponding genes. We also identify candidate TFs that can bind to these sites in a sequence-dependent manner. By integrating transcriptome and methylome profiles, we construct a TF-CpG-gene regulatory network for colon cancer, which is used to determine the roles of TFs and methylation in the transcription process. Finally, based on TF-CpG-gene relationships, we design a framework to evaluate patient prognosis, which shows that one TF-CpG-gene triplet is significantly associated with patient survival rate and represents a potential novel biomarker for use in colon cancer prognosis and treatment.

Identification and Rational Design of a Novel Antibacterial Peptide Dermaseptin-AC from the Skin Secretion of the Red-Eyed Tree Frog Agalychnis callidryas.

Antibiotic resistance represents a tremendous contemporary clinical challenge. Given this challenge, antimicrobial peptides (AMPs) are regarded as one of the most promising new options for next-generation lead antibiotics. Here, we describe the antibacterial activities of a cationic peptide named DRP-AC4, obtained from frog skin secretion using shotgun cloning. Two modified peptides were derived by substituting the sequence of amino acids to complete the hydrophobic face (DRP-AC4b) and increase net charge (DRP-AC4a), respectively. The activity and cytotoxicity of these two peptides were compared. DRP-AC4a displayed significantly increased potency against bacteria compared to the natural peptide. It should be noted, however, that both analogue peptides demonstrated higher lytic ability than the natural peptide against the membranes of mammalian erythrocytes. At the same time, all three peptides displayed lower hemolytic activity compared to their antibacterial activity. Here, we demonstrate that AMPs have more complex activity mechanisms and faster bactericidal rates than traditional antibiotics, which may be one of the reasons why bacteria do not develop resistance to them. These discoveries provide interesting insights into the discovery and development of novel drugs from natural sources.