LL-37

Abstract

Refractory rosacea can be effectively treated with fractional microneedle radiofrequency (FMR), but its optimal parameters need confirmation.

Abstract

There is an urgent need for new antimicrobial agents to address the emerging antimicrobial resistance and the lack of novel antibiotics on the market. Antimicrobial peptides (AMPs) have gained significant interest as potential antibiotics over the past 30 years due to their broad activity against bacteria. So far, the presence, characteristics, and function of AMPs in camel immunity remain to be explored. Therefore, this study aims to identify and functionally characterize AMPs in Camelus Dromedarius using in-silico and experimental approaches. In-silico identification and prediction of cathelicidin peptides properties were conducted using Blastp, Conserved Domain, Signal P-5.0, Peptide Cutter-Expasy, and the Antimicrobial Sequence Scanning System (AMPA) database. Physicochemical and biological properties were characterized using bioinformatics analysis tools. The experimental assays of synthetic AMPs were performed using circular dichroism (CD) spectroscopy, colony-forming assay, sytox green uptake assay, transmission and scanning electron microscopy, and hemolysis assay. Three cathelicidin peptides were identified from Camelus Dromedarius which were designated as CdPMAP-23, Cdprotegrin-3 (CdPG-3), and Cdcathelin-like (CdCATH). CdPG-3 and CdCATH demonstrated significant antibacterial effects against all tested Gram-negative and Gram-positive strains, including Escherichia. coli (Multidrug resistant) and Methicillin-Resistant Staphylococcus aureus (ATCC 700699). These two peptides caused significant membrane leakage and damage to Escherichia. coli (ATCC 25922), with CdPMAP-23 showing a lesser effect. Lower concentrations of CdPMAP-23, CdPG-3 and CdCATH exhibited low to moderate lytic activity against red blood cells in humans, camels, and chickens. This study identified novel AMPs from dromedary camels with potential therapeutic value against multidrug-resistant strains. The results show that AMPs are present in dromedary camels, setting out a foundation for further studies on the unique features of their innate immune system.

Abstract

Rosacea is a chronic inflammatory cutaneous disorder predominantly affecting the centrofacial region, whose pathogenesis is complex and not yet fully understood. In this review we summarized the latest significant advances in the pathogenesis of rosacea in recent years. In genomic studies, the application of bioinformatics techniques such as whole-genome sequencing has identified novel susceptibility genes and linked multiple pathogenic mechanisms. Neurovascular dysfunction resulting from abnormal neuropeptides expression and dysregulated amino acid metabolism constitutes an important pathogenic factor in rosacea. The TLR2/LL-37/mTORC1 signaling axis, as a core regulatory pathway in innate immunity has been elucidated in detail. In addition, the dysbiosis of skin and gut microbiota, together with the impairment of skin barrier function, is also closely associated with the onset and progression of this disease. The deeper understanding of the pathogenesis of rosacea will benefit the development of new drugs and promote individualized diagnosis and treatment.

Abstract

Introduction. The increasing resistance and the pathogen's complex multi-drug resistance mechanisms made the selection of effective antimicrobial treatments more challenging for Pseudomonas aeruginosa (P. aeruginosa). The study aimed to explore the effect of Scutellaria baicalensis, Prunella vulgaris and antimicrobial peptide LL-37 on the virulence factors of P. aeruginosa.Hypothesis. Previous studies have shown that extracts from traditional Chinese medicines, Scutellaria baicalensis and Prunella vulgaris, can also enhance the effects of antibiotics and reduce antibiotic resistance in P. aeruginosa. Antimicrobial peptide LL-37 shows the potential as a new-generation candidate for treating multi-drug-resistant bacteria, which has advantages over traditional antibiotics, whilst the combination role between Scutellaria baicalensis, Prunella vulgaris and LL-37 in P. aeruginosa remains unknown.Aim. We explored whether the combined use of Scutellaria baicalensis, Prunella vulgaris and LL-37 can exert antibacterial effects through the quorum sensing (QS) system.Methodology. The minimal inhibitory concentrations of Scutellaria baicalensis, Prunella vulgaris and LL-37 were determined for PAO1 and PA-ΔlasI/rhlI using micro broth dilution. The antibacterial activity of Scutellaria baicalensis combined with LL-37 and Prunella vulgaris combined with LL-37 was also assessed. The growth abilities of PAO1 were analysed after being treated with Scutellaria baicalensis, Prunella vulgaris and LL-37, respectively. Elastase secretion was measured using Congo red-elastic proteinase assays. And the expressions of QS genes (lasI, rhlR) were analysed by real-time PCR.Results. Single or combined treatments of Scutellaria baicalensis and LL-37 and Prunella vulgaris and LL-37 would significantly reduce elastase secretion. There were no significant differences in proliferation between the groups at any timepoint. All treatments downregulated lasI and rhlR gene expressions.Conclusion. Scutellaria baicalensis, Prunella vulgaris and antimicrobial peptide LL-37 all down-regulate the QS system-related genes of P. aeruginosa, inhibiting the secretion of virulence factors and reducing bacterial toxicity.

Abstract

Cathelicidins, a diverse family of host defence peptides (HDPs) in vertebrates, are recognized for their potential in combating resistant microorganisms and their varied biological functions. While extensive studies have focused on mammalian cathelicidins, those in reptiles remain largely unexplored. In this study, we conducted a genome mining analysis that identified 287 cathelicidin genes across reptilian orders Testudines and Squamata. Of these genes, we identified 219 complete cathelicidin protein sequences and 68 cathelicidin-like gene copies that appear to be pseudogenes or gene fragments lacking intact open reading frames. We established for the first time a classification for reptile cathelicidins of the cited orders based on their sequence and structure, observing six types for Testudines and six for Squamata, suggesting a common ancestral lineage. Furthermore, we investigated the genomic arrangement of these cathelicidin genes, uncovering that they are grouped into clusters with variability in the gene number and in their organization. Cathelicidin derived mature peptides were classified into nine groups based on their sequences and physicochemical properties. This comprehensive study enhances the understanding of the cathelicidin family in reptiles, clarifying their genomic organization and describing the different types present. These classifications pave the way for future studies on the functions and specialization of each identified cathelicidin group. Moreover, they enable potential structure-activity studies of the peptides, establishing a foundation for differentiating their key features.

Abstract

Background: Lung metastasis is a leading cause of breast cancer (BC)-related mortality, driven by the immunosuppressive traits of the metastatic tumor microenvironment. However, the mechanisms underlying cell-cell crosstalk in shaping immune evasion within the metastatic niche remain poorly defined. Neutrophil extracellular traps (NETs) and their associated proteins, such as cathelicidin, have emerged as key mediators of metastatic regulation in cancer. Here, we aimed to decipher the interaction between a neutrophil subset characterized by high expression of lymphocyte antigen 6 complex locus g (Ly6ghigh) and cluster of differentiation 8-positive T lymphocytes (CD8+ T cells), mediated via cathelicidin embedded in NETs, as well as their synergistic mechanism and cooperative role in promoting lung metastasis of BC. Methods: We characterized neutrophil heterogeneity and functional dynamics by performing single-cell RNA sequencing and flow cytometry on lung tissues derived from murine models of BC lung metastasis. We utilized cathelicidin-related antimicrobial peptide (Cramp) knockout mice to dissect the role of cathelicidin in NETs. The spatial colocalization of apoptotic CD8+ T cells and NETs was analyzed using multiplex immunofluorescence, and the molecular interactions were probed by protein binding assays. Results: Neutrophils in the lung metastatic niche were classified into 2 subsets based on the Ly6g expression: Ly6ghigh and Ly6glow neutrophils. Ly6glow neutrophils, which were recruited in the macrometastatic stage, exhibited myeloid-derived suppressor cell-like characteristics. Notably, Ly6ghigh neutrophils induced CD8+ T cell apoptosis through NET formation, with apoptotic CD8+ T cells spatially clustered within NET-rich areas. Mechanistically, NET-derived cathelicidin (Cramp in mice) directly bound to mitochondrial adenine nucleotide translocator 1 (Ant1) in CD8+ T cells, triggering conformational changes and complex formation with voltage-dependent anion channel 1 (Vdac1). These events resulted in the opening of the mitochondrial permeability transition pore and loss of mitochondrial membrane potential. Conclusions: Our study demonstrates that Ly6ghigh neutrophils play a critical role in immunosuppression and immune evasion through NET-induced apoptosis of CD8+ T cells. These findings underscore the importance of NETs and cathelicidin in BC lung metastasis, suggesting their potential as therapeutic targets in restoring antitumor immunity and in preventing metastatic progression.

Abstract

Antimicrobial peptides (AMPs), evolutionarily conserved components of innate immunity characterized by their broad-spectrum efficacy and minimal resistance development, are increasingly recognized as promising therapeutic candidates. This review aims to integrate current knowledge concerning natural and synthetic antimicrobial peptides and their therapeutic effectiveness in addressing gastrointestinal infections.

Abstract

Colorectal cancer (CRC) remains a major global health challenge, with increasing incidence and limited treatment options. The antimicrobial peptide cathelicidin (LL-37) has been implicated in both tumorigenic and tumor-suppressive roles, but its precise function in CRC progression remains unclear. This study investigates the LL-37 expression in CRC and its association with key molecular pathways, including vitamin D signaling and G protein-coupled receptors (GPCRs). We analyzed LL-37 mRNA expression in 25 CRC tissue samples and matched healthy colonic mucosa using quantitative real-time PCR. Additionally, we assessed the expression of potential LL-37 target receptors, including formyl peptide receptor 2 (FPR2), toll-like receptors (TLR3, TLR4), CXC chemokine receptor 2 (CXCR2), and mas-related gene X2 (MrgX2). The correlation between LL-37 expression and clinicopathological factors, including tumor stage and nodal metastases, was also evaluated. LL-37 expression was significantly upregulated in CRC tissues compared to normal mucosa (p<0.001), with higher expression in advanced-stage CRC (AJCC stage III) and tumors with nodal metastases (p=0.006). Molecular analysis revealed significantly increased FPR2 expression and reduced TLR3 expression in CRC tissue, suggesting their involvement in tumor progression. Our findings suggest a role for LL-37 in CRC progression, potentially mediated through FPR2 activation and TLR3 suppression. The observed discrepancies in LL-37 function across studies highlight its complex, context-dependent role in tumor biology. Further research is needed to elucidate the mechanistic basis of LL-37 signaling and its potential as a therapeutic target in CRC.

Abstract

The review summarises the basic information on non-specific factors of mammals that potentially have antimicrobial action. A comparison of previously known factors with the latest literature data is carried out. The following peptide and protein factors are considered: lysozymes, transferrins, interferons, interleukin-2, antimicrobial peptides (defensins, cathelicidins, histatins) and protective glycoproteins (mucins, lectins). These major antibacterial factors perform regulatory functions in the immune system, and some are also able to resist viral and fungal infections or oncological pathologies. The study of the internal antibacterial factors of mammals and the mechanisms of their activation is of great importance for the fight against bacterial infections, including antibiotic-resistant ones. This knowledge is necessary for the development of new approaches to the treatment of humans and farm animals.

Abstract

Cathelicidins are short cationic peptides with potent microbicidal activities and comprise an important arm of host innate immunity. Many cell types can produce cathelicidins, but they are mainly expressed by recruited immune cells and are induced in epithelial cells during infection. Although the mechanisms of bacterial killing by cathelicidins have been largely elucidated in vitro, those that regulate their activities in vivo are less well understood. Bacterial pathogens often co-opt host extracellular matrix (ECM) components and their functions to escape host defense; however, it is unclear whether such mechanisms exist against cathelicidins. Several studies have demonstrated that host heparan sulfate (HS) inhibits LL-37, the human cathelicidin, suggesting that bacteria might exploit HS to evade killing by cathelicidins. However, precisely how HS inhibits LL-37 and possibly other cathelicidins remains unknown, and the role of the HS-cathelicidin interaction in infectious disease has not been rigorously studied. Here, we found that deleting CRAMP, the murine cathelicidin, significantly increases the susceptibility of mice to Staphylococcus aureus corneal infection. We also determined that heparan compounds bind to CRAMP with low nanomolar affinity, the secondary structure of CRAMP is required for HS binding, and HS binding to CRAMP inhibits CRAMP binding to target bacterial cells. Furthermore, we found that heparan compounds inhibit the killing of S. aureus by cathelicidins derived from several mammalian species in a 2-O-sulfate-dependent manner. Additionally, we demonstrate for the first time that conditional deletion of HS2ST, the enzyme responsible for 2-O-sulfation of HS, in corneal epithelial cells significantly reduces the susceptibility of mice to corneal infection. Altogether, these data uncover an endogenous inhibition mechanism of cathelicidins where 2-O-sulfated epithelial HS tightly binds and neutralizes the antibacterial activity of cathelicidins.

Abstract

Antimicrobial peptides are integral components of the innate immune system and play a vital role in maintaining oral homeostasis. LL-37, the only human cathelicidin antimicrobial peptide, has gained increasing attention due to its broad-spectrum antimicrobial activity and diverse immunomodulatory functions within the oral cavity.

Abstract

TLR-targeted immunotherapy represents a promising strategy for combating infectious diseases by initiating or enhancing protective antimicrobial immunity. Here, we identified the first frog-derived TLR2 and TLR4 agonist, Cathelicidin-Ka (Cath-Ka), from the skin of Kaloula pulchra. The presence of Cath-Ka significantly enhanced proliferation, cytokine production, polarization, chemotaxis, phagocytosis, and intracellular bacterial killing of macrophages and peritoneal cells by targeting TLR2 and TLR4, rather than other pattern recognition receptors, and subsequently activated the downstream MyD88-MAPKs pathway. Cath-Ka also promoted macrophage polarization towards the M1 rather than M2 phenotype, and its intraperitoneal injection significantly promoted the chemotaxis of pro-inflammatory monocytes/macrophages into the peritoneal cavity. Finally, the mutant of Cath-Ka with amination at C-terminus had stronger effects on macrophage function modulation than the original peptide. These findings suggest that Cath-Ka and its amidated mutant are promising candidates for the treatment of TLR2 and TLR4-related diseases, including infections.

Abstract

Antimicrobial peptides (AMPs) are promising agents against infections caused by multidrug-resistant bacteria. Notably, the human AMPs LL-37 and α-defensin (HNP1) exhibit a cooperative effect, synergistically killing bacteria while reducing host cytotoxicity. However, the structural-function relationship of this phenomenon remains unclear. Here, we report that the previously observed neutralization of LL-37 toxicity against POPC membranes by HNP1 is not unique to this pair but can be extended to other members of the defensin family including HNP3, HNP4, and hBD1. This cooperative effect, however, was absent in HNP2. By comparing amino acid sequences, we identified that the N-terminus of the defensins modulates the cooperative effect between LL-37 and the defensins.

Abstract

Maintaining immune homeostasis is essential for livestock health and productivity, particularly in the face of infection or stress. Host defense peptides (HDPs), including β-defensins and cathelicidins, are key innate immune components with both antimicrobial and immunomodulatory properties. This study aimed to characterize the immunomodulatory effects of five bovine HDPs-BNBD1, BNBD3, LAP, Bac5, and BMAP27-on peripheral blood mononuclear cells (PBMCs) and bovine turbinate (BT) epithelial cells, under both basal and lipopolysaccharide (LPS)-stimulated inflammatory conditions. Cytokine secretion, cell viability, and real-time epithelial cell behavior were assessed to evaluate peptide-specific immune modulation.

Abstract

Excessive accumulation of cell-free DNA (cfDNA) has been identified as a primary pathogenic factor in autoimmune diseases. The circulating deoxyribonuclease (DNase) maintaining cfDNA homeostasis is suppressed, and thus exogenous DNase has been applied to degrade cfDNA for inflammation control. However, in pathological states, cfDNA and cationic endogenous peptide (e.g., LL37) form immune complexes (ICs), which not only weaken DNase efficacy but also facilitate immune cell internalization to induce an inflammatory response. With LL37-DNA as a model IC, here we found that the LL37 occupancy not only sterically hinders cfDNA's access to the catalytic sites but also induces deactivation of DNase via formation of ternary complexes (LL37-DNA-DNase I). This transition critically impairs the activity of DNase I within LL37-rich inflammatory microenvironments. Thus, we postulated that heparin, a clinically approved anionic glycosaminoglycan, could destruct the ICs and liberate cfDNAs, restoring their susceptibility to degradation. Indeed, we found that a combination of heparin and DNase I facilitates the DNA degradation and inhibits the ICs-mediated TLR9 activation in vitro. However, the therapeutic outcome observed in rheumatoid arthritis (RA) model was still suboptimal, attributed to the short plasma half-life of DNase. To validate this, we engineered a DNase nanoparticle (DNase@TANP) capable of sustained release of the enzyme. Consequently, the sequential administration of heparin and DNase@TANP (with a 30-min interval) to RA model demonstrated a synergistic cfDNA degradation efficiency, effectively suppressing Toll-like receptor (TLR) mediated inflammatory pathways and ameliorating joint inflammation. This strategy, leveraging clinically approved agents for cfDNA clearance, establishes a promising therapeutic paradigm for cfDNA-associated autoimmune disorders.

Abstract

Cathelicidins are crucial antimicrobial peptides (AMPs) that play a key role in the innate immunity of marine vertebrates. The pygmy sperm whale (Kogia breviceps), which resides in environments populated by diverse microbial communities, faces complex pathogenic threats; however, its cathelicidin family AMPs remain uncharacterized. In this study, we identified three novel cathelicidin peptides-Kb4-1, Kb4-2, and Kb5 from the whale (Kogia breviceps). All three peptides exhibited broad-spectrum and potent antibacterial activity, with Kb5, an amphipathic α-helical peptide, showing the strongest and fastest bactericidal effect. Moreover, these peptides effectively inhibited biofilm formation, disrupted pre-established biofilms, and eradicated bacterial persister cells. Notably, Kb5 induced the most pronounced bacterial membrane disruption among the three peptides. Additionally, all peptides exerted their antibacterial effects, at least partially, through the interaction with bacterial DNA and the consequent induction of reactive oxygen species (ROS) production. In a S. aureus-induced murine peritonitis model, Kb5 treatment significantly reduced bacterial load and improved survival rates in mice. These findings highlight the therapeutic potential of Kb5 and enhance our understanding of host defense mechanisms in marine mammals living in challenging environments.

Abstract

Cathelicidins are evolutionarily conserved host defence peptides known for their dual antimicrobial and immunomodulatory functions. Among them, LL-37 in humans and CRAMP in rodents have emerged as crucial regulators of both mucosal immunity and CNS inflammation. This review explores the emerging evidence that positions cathelicidins as key modulators of the gut-brain axis, a bidirectional communication network increasingly implicated in neuroinflammatory and neurodegenerative disorders. Drawing on a diverse body of animal and human research, we examine the multifaceted roles of cathelicidin in maintaining intestinal barrier integrity, shaping microbiota composition and regulating innate immune signalling. Particular attention is paid to how gut-derived metabolites, such as short-chain fatty acids and vitamin D, influence cathelicidin expression, with downstream consequences for both gastrointestinal and neural health. In the CNS, cathelicidin exhibits context-dependent effects, acting as a neuroprotective modulator when derived from neurons, but exacerbating glial-mediated inflammation when sourced from peripheral immune cells. This functional dichotomy underscores the importance of cellular origin, concentration and microenvironmental cues. Furthermore, we delineate how cathelicidin facilitates crosstalk between peripheral and central compartments, serving as both a local effector and a systemic messenger. Collectively, these insights support a reconceptualization of cathelicidin not merely as a passive antimicrobial peptide, but as an active molecular bridge between mucosal immunity and neuroinflammation, with promising implications for diagnostics and therapeutics targeting dysfunction of the gut-brain axis.

Abstract

The increasing prevalence of multidrug-resistant (MDR) bacterial infections poses global health challenges, highlighting the urgent need for new antimicrobial agents. The key advantages of antimicrobial peptides are their ability to rapid bactericidal activity and their low propensity for resistance development. In this study, we designed a series of antimicrobial peptides by fusing the two fragments of antimicrobial peptides Cathelicidin-BF (1-9) and LL-37 (17-29), and then tested against selected Gram-negative and Gram-positive bacterial strains. Among these peptides, KF-22 displayed potent antibacterial activity against a panel of Gram-negative and Gram-positive pathogens with MICs less than 5 μg/mL, with demonstrating low toxicity. Moreover, KF-22 exhibits rapid bactericidal activity and a low propensity to induce resistance, simultaneously showing excellent anti-biofilm and persisters activity. Mechanistic studies revealed that KF-22 induces membrane damage by targeting bacterial-specific membrane components, leading to the dissipate the proton motive force (PMF) and resulting in metabolic perturbations. Furthermore, in mice models no significant change was observed in plasma biochemical parameters between the treated and the control groups. In addition, in vivo studies confirmed that KF-22 are effective against drug-resistant pathogens. Taken together, the findings suggest that KF-22 is a promising candidate for further development to tackle MDR bacterial infections.

Abstract

The etiology of Alzheimer's disease (AD) remains under active debate. In this perspective, we explore the hypothesis that a primarily infection-caused chronic dysregulation and weakening of human innate immunity via the underexpression, degradation, and inactivation of innate immune proteins necessary for direct antimicrobial effects and regulation of host defense and autophagy could lead to AD. Key evidence relates to the fact that important innate immune proteins such as LL-37-which can bind Aβ and block amyloid formation-as well as Apolipoprotein E, antiviral interferons, and TNF-α can be degraded and deactivated by enzymes produced by the common oral anaerobic pathogen Porphyromonas gingivalis (Pg). Pg produces numerous virulence factors; of particular importance for AD are Pg's gingipain cysteine proteases. Deleterious effects of chronic Pg infection and gingipains include a systemic downregulation and paralysis of the interferon response, particularly the antiviral interferon-lambda response, which enables replication of endemic herpesviruses. The result is a chronic, low-level viral infectious assault on gut, nerves, and brain causing the production of Aβ antimicrobial peptides, accumulation of Aβ plaques, phosphorylation of Tau, progressive neuroinflammation, and neurodegeneration. The resultant innate immune system dysregulation, as an AD etiology, ties together the well-known amyloid cascade hypothesis and the infectious theory of AD into a unified explanation of the pathology and cause of AD. If this theory holds true, it suggests preventative approaches: (1) test for and eradicate Pg from oral flora, and/or directly deactivate the gingipains; and (2) reduce Herpesvirus exacerbations by the use of antiviral drugs and/or vaccines (e.g., Bacillus Calmette-Guérin).

Abstract

The escalating global threat of antimicrobial resistance (AMR) and chronic biofilm-associated infections underscores the urgent need for novel therapeutic agents. Antimicrobial peptides (AMPs) offer a promising alternative due to their potent activity, broad-spectrum efficacy, and low resistance induction. In this study, we identified three novel cathelicidin-like peptides-Cr-CATH-1 (Cr1), Cr-CATH-2 (Cr2), and Cr-CATH-3 (Cr3)-from Chroicocephalus ridibundus. These peptides were systematically evaluated for their physicochemical properties, antimicrobial activity, bactericidal kinetics, and effects on biofilm formation and persister cells. Cr1 exhibited the most potent and broad-spectrum antimicrobial activity, particularly against Gram-negative and aquatic pathogens. Although Cr2 and Cr3 displayed relatively weaker antimicrobial effects, both peptides were effective in biofilm eradication and persister cell killing. Cr1 also demonstrated strong bactericidal activity, low cytotoxicity, and minimal hemolysis, suggesting a favorable safety profile. Its stability under physiological salt conditions, along with its ability to disrupt bacterial membranes, bind to DNA, and induce reactive oxygen species (ROS) production, highlights its therapeutic potential. In vivo, Cr1 significantly reduced bacterial load and improved survival in a murine peritonitis model, further supporting its potential for clinical and aquaculture applications. Our results suggest that Cr1 is a promising candidate for further development, while Cr2 and Cr3 may provide valuable insights for targeted therapeutic strategies, warranting additional investigation.

Abstract

Rosacea is a chronic inflammatory skin disease characterized by persistent facial erythema and telangiectasia. The antimicrobial peptide LL37 is a key initiator in rosacea, with mast cells serving as critical inflammatory mediators. However, the precise mechanism underlying LL37-induced mast cell degranulation remains unclear.

Abstract

S protein is conserved among streptococci and contributes to group A Streptococcus virulence, but the mechanisms involved are unclear. Here we used genetic, biochemical, single-molecule, in vitro and in vivo analyses to show that S protein is crucial for resistance against host-derived antimicrobials by coordinating cell wall modification and repair. We observed that S protein was localized to the streptococcal septum dependent on its transmembrane domain, while S protein function was dependent on its peptidoglycan (PG)-binding LysM domain. Direct interactions between the pneumococcal S protein and the PG synthase PBP1a as well as the PG deacetylase PgdA were detected. Loss of S protein reduced the proportion of circumferentially moving PBP1a molecules, altered streptococcal morphology and increased susceptibility to cell-wall-targeting antibiotics, suggesting that S protein activates PBP1a. Streptococcus pneumoniae ess mutants lacking the gene encoding S protein were more susceptible to human antimicrobial peptide LL-37 and lysozyme, while their virulence was decreased compared with wild-type bacteria in zebrafish and mice. These data suggest that S protein activates the PG repair and modification complex, providing defence against host-derived and environmental antimicrobials.

Abstract

With antibiotic resistance being a major global concern, there is a huge need of new treatment options to fight bacterial infections. In this study, we highlight the antibacterial and host-protective roles of a novel synthetic antimicrobial peptide in uropathogenic Escherichia coli-infected uroepithelial cells. This peptide, designed from a fragment of human cathelicidin LL-37 and named LD4-PP, was found to be highly potent against clinical isolates of E. coli as well as ESBL-producing and multi-drug resistant E. coli. Additionally, LD4-PP inhibited the formation of new biofilm, damaging both the bacterial surface and the bacterial genome. LD4-PP also modulated the host cell lipid vacuole, caveolin-1, and Rho GTPase B affecting bacterial survival. Furthermore, LD4-PP exerts immunomodulatory effects by modulating free radical formation, expression of antioxidants, and inflammasome-mediated cell death. Pronounced uroepithelial cell death was observed after E. coli infection which was significantly inhibited by LD4-PP without affecting the cellular toxicity. Overall, the peptide LD4-PP is shown to be a strong candidate for future clinical applications, particularly to prevent and treat urinary tract infections.

Abstract

The molecular mechanisms underlying the immunomodulatory effects of cathelicidins on macrophages remain poorly characterized. This study aimed to elucidate the immunomodulatory mechanisms of QsCATH, an antimicrobial peptide derived from the Chinese spiny frog (Quasipaa spinosa), in RAW264.7 macrophages using RNA sequencing and molecular docking. Transcriptomic analysis revealed that QsCATH significantly downregulated inflammatory-related genes (tnf, il6, ccl5, il1b) and suppressed pro-inflammatory cytokine production (tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β) by inhibiting key pathways such as NF-κB, TNF, and NOD-like receptor signaling. Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses showed that QsCATH balanced inflammatory resolution with host defense by modulating biological processes including "immune system processes," "defense responses," and "oxidative stress responses." Using molecular docking simulations, potential interactions were predicted between QsCATH and membrane-associated proteins Nod2, Ripk2, and Itga3 (binding scores: - 239.00, - 213.24, and - 290.08, respectively), suggesting direct interference with receptor-mediated signaling cascades. This study presents the first transcriptome-level analysis of the immunoregulatory network of amphibian cathelicidins, providing insights for developing novel peptide-based therapeutics against drug-resistant infections and inflammatory disorders.

Abstract

The emergence of multidrug bacterial isolates, including Salmonella (S.) Typhimurium, which primarily spreads to humans through chicken products, is correlated with a rising prevalence of antimicrobial therapy failure. Thus, we performed a comprehensive analysis of the combined impact of Salmonella bacteriophage (BP) and grape seed oligomeric pro-anthocyanidins (GSOPs) on growth performance, immune functions, antioxidant capacity, cecal microbiota, gut integrity, and S. Typhimurium resistance in challenged broilers. A total of 250 Ross-308 male broiler chicks were offered either a control diet or a diet supplemented with Salmonella BP alone at concentrations of 109 PFU/0.1 ml, GSOPs alone at a level of 400 mg/kg diet, and a combination of both Salmonella BP and GSOPs, and experimentally infected with multidrug-resistant (MDR) S. Typhimurium strain at 14 days of age. Broilers administered BP, GSOPs, and their combination, particularly BP+GSOPs, had enhanced growth performance attributes even following a challenge with S. Typhimurium, alongside decreased mortality percentage, which was evidenced by increased expression of MUC-2, β-defensin-1, cathelicidins-2, JAM-2, occludin, and CLDN-1 genes, reduced S. Typhimurium abundance, and downregulating its virulence-associated genes (sopE and spvC), alongside restored intestinal histological features. GSOPs+BP fortified group exhibited higher cecal beneficial bacteria counts (Bacteroides, Firmicutes, Lactobacillus, and Bifidobacterium species), lower cecal harmful bacteria loads (Escherichia, Enterobacteriaceae, and Clostridium clusters I and IV), decreased serum oxidative markers [H2O2, reactive oxygen species (ROS), and malondialdehyde (MDA)], and increased serum antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)]. The incorporation of dietary BP, and GSOPs combination significantly downregulated the intestinal inflammatory regulated genes (IL-1β, IL-6, CCL4, CCL20, COX-2, and iNOS), and mTOR gene, and reduced the serum concentrations of LYZ, NO, CRP, and complement C3, alongside increased serum IgG, and IgM levels, and upregulation of autophagy-related genes (atg5, atg7, atg12, BCLN-1, and LC3-II). The aforementioned beneficial effects of the BP and GSOPs combination support their prospective use in avian nutrition to enhance performance and stimulate immune defense against gastrointestinal illnesses, including S. Typhimurium infection.

Abstract

Rosacea is a chronic inflammatory facial dermatosis with incompletely elucidated pathogenesis. LL37 is a key molecular mediator in rosacea development, and mast cells represent pivotal immune players in this process. However, the precise mechanism underlying LL37-induced mast cell degranulation remains undefined.

Abstract

Plasmodium-induced malaria infection remains a leading global health threat. Host defense peptides (HDPs), key components of innate immunity, target multiple stages of Plasmodium development through direct antimicrobial activity and immunomodulation. These peptides represent promising agents as antimalarial compounds due to their dual role in directly targeting Plasmodium parasites and modulating host immune responses. Several HDPs, including defensins, cathelicidins, NK-2 peptide, platelet factor 4, macrophage inflammatory protein-3α, and hepcidin play pivotal roles in protecting against malaria infection. However, the roles and specific targets of HDPs in malaria defense remain incompletely understood. This review outlines the key HDPs involved in malaria defense, as well as recent findings about their specific roles towards Plasmodium parasites and infected cells. Furthermore, advancements in understanding HDP interactions with Plasmodium at various infection stages, as well as their roles in modulating the host immune response are discussed. Also, the current limitations in uncovering the full implications of HDPs in malaria infection are highlighted.

Abstract

Bacterial extracellular vesicles (BEVs) have emerged as a promising therapeutic platform, offering the potential to be engineered for targeted molecular delivery. In this study, the human cathelicidin antimicrobial peptide (LL37) was encapsulated into extracellular vesicles derived from the fish pathogen Edwardsiella piscicida (EpEVs) through co-incubation. LL37-encapsulated EpEVs (EpEVs-LL37) were isolated by ultracentrifugation and characterized with a mean particle size of 73.6 ± 1.4 nm and a zeta potential of -11.27 ± 0.49 mV. Morphology of EpEVs-LL37 was confirmed as spherical-shaped particles. Enzymatic stability evaluation results revealed a proportionate increase in mean size and zeta potential with the pepsin concentration (0.4-2 mg/mL) at pH 2.0. EpEVs-LL37 exhibited lower toxicity than free LL37 in both Raw 264.7 cells and zebrafish larvae, while maintaining a similar level of cellular internalization as naïve EpEVs. Notably, EpEVs-LL37 demonstrated enhanced antibacterial activity against E. piscicida compared to free LL37, as evidenced by time-kill kinetics and bacterial viability assays. Mechanistically, EpEVs-LL37 damaged the bacterial cell membrane and induced higher levels of reactive oxygen species (ROS), along with bacterial membrane permeability, as observed through confocal microscopy. Additionally, EpEVs-LL37 upregulated the expression of immunomodulatory genes (Tlr2, Il1β, Il10) in both Raw 264.7 cells and zebrafish larvae. Furthermore, treatment with EpEVs-LL37 (10 µg/mL) significantly enhanced wound-healing in vitro and in vivo, reducing the cellular wound area to 11.01 ± 0.81% and increasing larval fin regeneration to 1.64 ± 0.07 mm², both outperforming free LL37. Collectively, these findings highlight EpEVs-LL37 as a promising therapeutic and drug-delivery platform for the treatment of E. piscicida-associated infections.

Abstract

Klebsiella pneumoniae is becoming increasingly difficult to treat as multidrug-resistant (MDR) strains become more prevalent. The formation of biofilm heightens this threat by embedding bacterial cells in a polysaccharide-rich matrix that limits antibiotic penetration. Here we dissect the anti-biofilm bovine host-defense cathelicidin peptide fragment bac7 (1-35), exploring its anti-biofilm mechanism, evaluating its ability to curb colonization of the vital organs by hypervirulent K. pneumoniae, and testing its breadth of activity against diverse clinical isolates. Transcriptomic profiling revealed that bac7 (1-35) simultaneously compromises the bacterial membrane and inhibits ribosomal function, a dual assault that precipitates rapid biofilm collapse and blocks bacterial spread. Further, bac7 (1-35) eradicated the strongest biofilms produced by MDR clinical isolates in the Multidrug-Resistant Organism Repository and Surveillance Network (MRSN) diversity panel. Although bac7 (1-35) kills bacterial cells via a cytosolic mechanism, membrane interaction profiles varied among MRSN isolates, correlating with differential peptide translocation. In a delayed-treatment murine skin-abscess model, bac7 (1-35) halted in vivo colonization of the vital organs by the hypervirulent strain NTUH-K2044. Collectively, these results delineate a multifaceted mode of action for bac7 (1-35) and underscore its therapeutic promise against biofilm-associated MDR K. pneumoniae infections.

Abstract

The focus of this study was to explore phage display systems employing bacteriophage lambda (λ) gene fusions to its capsid decoration protein gpD as reagent tools for tackling disease. The biological activity of gpD-fusions was examined by testing for the retained antimicrobial toxicity of cathelicidins or defensins fused to gpD. Our previous finding that only COOH fusions of either cathelicidins or defensins to gpD were toxigenic was expanded to show that only the reduced form of fused defensin antimicrobial polypeptides was found to be toxigenic. Compared in review are gene-fusion lytic display systems (where the fusion-display gene is integrated within the viral genome) with a surrogate system, employed herein, that exogenously provides the fusion-display protein for addition to phage capsid. It is easily possible to produce fully coated lambda display particles (LDP) serving as single epitope vaccines (SEV), or antimicrobials, or to produce partially coated LDP without any complex bacteriophage genetic engineering, making the system available to all. The potential to build vaccine vector phage particles (LDNAP) comprising essentially sheathed DNA vaccines encapsulated within an environmentally protective capsid is described. LDNAP are produced by introducing a cassette into the phage genome either by phage-plasmid recombination or cloning. The cassette carries a high-level eukaryotic expression promoter driving transcription of the vaccine candidate gene and is devoid of plasmid resistance elements.