Multifaceted immune functions of human defensins and underlying mechanisms

Human β-defensins and their synthetic analogs: Natural defenders and prospective new drugs of oral health

As a family of cationic host defense peptides, human β-defensins (HBDs) are ubiquitous in the oral cavity and are mainly synthesized primarily by epithelial cells, serving as the primary barrier and aiming to prevent microbial invasion, inflammation, and disease while maintaining physiological homeostasis. In recent decades, there has been great interest in their biological functions, structure-activity relationships, mechanisms of action, and therapeutic potential in oral diseases. Meanwhile, researchers are dedicated to improving the properties of HBDs for clinical application. In this review, we first describe the classification, structural characteristics, functions, and mechanisms of HBDs. Next, we cover the role of HBDs and their synthetic analogs in oral diseases, including dental caries and pulp infections, periodontitis, peri-implantitis, fungal/viral infections and oral mucosal diseases, and oral squamous cell carcinoma. Finally, we discuss the limitations and challenges of clinical translation of HBDs and their synthetic analogs, including, but not limited to, stability, bioavailability, antimicrobial activity, resistance, and toxicity. Above all, this review summarizes the biological functions, mechanisms of action, and therapeutic potential of both natural HBDs and their synthetic analogs in oral diseases, as well as the challenges associated with clinical translation, thus providing substantial insights into the laboratory development and clinical application of HBDs in oral diseases.

Roles of airway and intestinal epithelia in responding to pathogens and maintaining tissue homeostasis

Epithelial cells form a resilient barrier and orchestrate defensive and reparative mechanisms to maintain tissue stability. This review focuses on gut and airway epithelia, which are positioned where the body interfaces with the outside world. We review the many signaling pathways and mechanisms by which epithelial cells at the interface respond to invading pathogens to mount an innate immune response and initiate adaptive immunity and communicate with other cells, including resident microbiota, to heal damaged tissue and maintain homeostasis. We compare and contrast how airway and gut epithelial cells detect pathogens, release antimicrobial effectors, collaborate with macrophages, Tregs and epithelial stem cells to mount an immune response and orchestrate tissue repair. We also describe advanced research models for studying epithelial communication and behaviors during inflammation, tissue injury and disease.

Human β-defensin-1 affects the mammalian target of rapamycin pathway and autophagy in colon cancer cells through long non-coding RNA TCONS_00014506

BACKGROUND

Colorectal cancer has a low 5-year survival rate and high mortality. Human β-defensin-1 (hBD-1) may play an integral function in the innate immune system, contributing to the recognition and destruction of cancer cells. Long non-coding RNAs (lncRNAs) are involved in the process of cell differentiation and growth.

AIM

To investigate the effect of hBD-1 on the mammalian target of rapamycin (mTOR) pathway and autophagy in human colon cancer SW620 cells.

METHODS

CCK8 assay was utilized for the detection of cell proliferation and determination of the optimal drug concentration. Colony formation assay was employed to assess the effect of hBD-1 on SW620 cell proliferation. Bioinformatics was used to screen potentially biologically significant lncRNAs related to the mTOR pathway. Additionally, p-mTOR (Ser2448), Beclin1, and LC3II/I expression levels in SW620 cells were assessed through Western blot analysis.

RESULTS

hBD-1 inhibited the proliferative ability of SW620 cells, as evidenced by the reduction in the colony formation capacity of SW620 cells upon exposure to hBD-1. hBD-1 decreased the expression of p-mTOR (Ser2448) protein and increased the expression of Beclin1 and LC3II/I protein. Furthermore, bioinformatics analysis identified seven lncRNAs (2 upregulated and 5 downregulated) related to the mTOR pathway. The lncRNA TCONS_00014506 was ultimately selected. Following the inhibition of the lncRNA TCONS_00014506, exposure to hBD-1 inhibited p-mTOR (Ser2448) and promoted Beclin1 and LC3II/I protein expression.

CONCLUSION

hBD-1 inhibits the mTOR pathway and promotes autophagy by upregulating the expression of the lncRNA TCONS_00014506 in SW620 cells.

Intercalated cell function, kidney innate immunity, and urinary tract infections

Intercalated cells (ICs) in the kidney collecting duct have a versatile role in acid-base and electrolyte regulation along with the host immune defense. Located in the terminal kidney tubule segment, ICs are among the first kidney cells to encounter bacteria when bacteria ascend from the bladder into the kidney. ICs have developed several mechanisms to combat bacterial infections of the kidneys. For example, ICs produce antimicrobial peptides (AMPs), which have direct bactericidal activity, and in many cases are upregulated in response to infections. Some AMP genes with IC-specific kidney expression are multiallelic, and having more copies of the gene confers increased resistance to bacterial infections of the kidney and urinary tract. Similarly, studies in human children demonstrate that those with history of UTIs are more likely to have single-nucleotide polymorphisms in IC-expressed AMP genes that impair the AMP's bactericidal activity. In murine models, depleted or impaired ICs result in decreased clearance of bacterial load following transurethral challenge with uropathogenic E. coli. A 2021 study demonstrated that ICs even act as phagocytes and acidify bacteria within phagolysosomes. Several immune signaling pathways have been identified in ICs which may represent future therapeutic targets in managing kidney infections or inflammation. This review's objective is to highlight IC structure and function with an emphasis on current knowledge of IC's diverse innate immune capabilities.

Human Neutrophil Alpha-Defensins Promote NETosis and Liver Injury in Alcohol-Related Liver Cirrhosis: Potential Therapeutic Agents

Background: Neutrophils are thought to play a pivotal role in the pathogenesis of many inflammatory diseases, such as hepatitis, liver cirrhosis, etc. Activated human neutrophils release human neutrophil peptides (HNP1-3) or alpha-defensins that are antimicrobial peptides in azurophil granules. Furthermore, HNP1-3 build a scaffold of neutrophil extracellular traps (NETs) and promote the process of programmed cell death called NETosis. Our study aimed to investigate the role of alpha-defensins in the pathogenesis of alcohol-related liver cirrhosis (ALC). Methods: The concentrations of alpha-defensins in the plasma of 62 patients with ALC and 24 healthy subjects were measured by ELISA. The patients with ALC were prospectively recruited based on the severity of liver dysfunction according to the Child-Pugh and Model of End-Stage Liver Disease-Natrium (MELD-Na) scores, modified Maddrey's Discriminant Function (mDF), and the presence of ALC complications. Results: The concentrations of alpha-defensins in plasma were significantly higher in the ALC patients than in the controls. The plasma levels of HNP1-3 correlated with the MELD and mDF scores. ALC subgroups with MELD > 20 and mDF > 32 displayed significantly higher HNP1-3 concentrations. The plasma levels of HNP1-3 revealed a good predictive AUC for hepatic encephalopathy and ascites development (0.81 and 0.74, respectively) and for patient survival (0.87) in those over 40 years of age. Conclusion: These findings suggest that alpha-defensins play an important role in the assessment of ALC.

Antimicrobial peptides and other potential biomarkers of critical illness in SARS-CoV-2 patients with acute kidney injury. AMPAKI-CoV study

Antimicrobial peptides (AMPs) constitute a complex network of 10-100 amino acid sequence molecules widely distributed in nature. While over 300 AMPs have been described in mammals, cathelicidins and defensins remain the most extensively studied. Some publications have explored the role of AMPs in COVID-19, but these findings are preliminary, and in vivo studies are still lacking. In this study, we report the plasma levels of five AMPs (LL-37, α-defensin 1, α-defensin 3, β-defensin 1, and β-defensin 3), using the ELISA technique (MyBioSource, San Diego, CA, United States, kits MBS2601339 (beta-defensin 1), MBS2602513 (beta-defensin 3), MBS703879 (alpha-defensin 1), MBS706289 (alpha-defensin 3), MBS7234921 (LL37)), and the measurement of six cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1), through the magnetic bead immunoassay Milliplex® and the MAGPIX® System (MilliporeSigma, Darmstadt, Germany, kit HCYTOMAG-60 K (cytokines)), in 15 healthy volunteers, 36 COVID-19 patients without Acute Kidney Injury (AKI) and 17 COVID-19 patients with AKI. We found increased levels of α-defensin 1, α-defensin 3 and β-defensin 3, in our COVID-19 population, when compared to healthy controls, along with higher levels of interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1. These findings suggest that these AMPs and cytokines may play a crucial role in the systemic inflammatory response and tissue damage characterizing severe COVID-19. The levels of α-defensin 1 and α-defensin 3 were significantly higher in COVID-19 AKI group in comparison to the non-AKI group. Furthermore, IL-10 and the product IL-10 × IL-1B showed excellent performance in discriminating AKI, with AUCs of 0.86 and 0.88, respectively. Among patients with COVID-19, AMPs may play a key role in the inflammation process and disease progression. Additionally, α-defensin 1 and α-defensin 3 may mediate the AKI process in these patients, representing an opportunity for further research and potential therapeutic alternatives in the future.

Combating bacterial infections with host defense peptides: Shifting focus from bacteria to host immunity

The increasing prevalence of multidrug-resistant bacterial infections necessitates the exploration of novel paradigms for anti-infective therapy. Antimicrobial peptides (AMPs), also known as host defense peptides (HDPs), have garnered extensive recognition as immunomodulatory molecules that leverage natural host mechanisms to enhance therapeutic benefits. The unique immune mechanism exhibited by certain HDPs that involves self-assembly into supramolecular nanonets capable of inducing bacterial agglutination and entrapping is significantly important. This process effectively prevents microbial invasion and subsequent dissemination and significantly mitigates selective pressure for the evolution of microbial resistance, highlighting the potential of HDP-based antimicrobial therapy. Recent advancements in this field have focused on developing bio-responsive materials in the form of supramolecular nanonets. A comprehensive overview of the immunomodulatory and bacteria-agglutinating activities of HDPs, along with a discussion on optimization strategies for synthetic derivatives, is presented in this article. These optimized derivatives exhibit improved biological properties and therapeutic potential, making them suitable for future clinical applications as effective anti-infective therapeutics.

Filipendula glaberrima Nakai extract inhibits the bacterial infection by induction of HBD2 and HBD3 expression, and reduction of the inflammatory activity

Defensins and inflammation are innate immune barriers of the body against infectious pathogens. Searching for a compound that can inhibit infectious diseases by affecting human β-defensin (HBD) and proinflammatory cytokines is the new trend in research to control bacterial infection. The aim of this study is to provide a natural compound, Filipendula glaberrima Nakai extract (FGE), which is able to induce the expression of an antimicrobial defensin as well as reduce inflammation. FGE induced the expression of HBD2 and HBD3 through activating both p38 and NF-κB signaling pathways. Furthermore, FGE inhibited the expression of TNF-α and IL-6 via p38 and NF-κB pathways in Staphylococcus aureus-stimulated THP1 cells. Injection of FGE alleviated cutaneous erythema and swelling caused by S. aureus injection in mice ears. Taken together, FGE could reduce bacterial infection by inducing the expression of defensin and anti-inflammatory activity.

Macrophages immunomodulation induced by Porphyromonas gingivalis and oral antimicrobial peptides

Porphyromonas gingivalis is a keystone pathogen associated with periodontitis development, a chronic inflammatory pathology characterized by the destruction of the supporting teeth structure. Macrophages are recruited cells in the inflammatory infiltrate from patients with periodontitis. They are activated by the P. gingivalis virulence factors arsenal, promoting an inflammatory microenvironment characterized by cytokine production (TNF-α, IL-1β, IL-6), prostaglandins, and metalloproteinases (MMPs) that foster the tissular destruction characteristic of periodontitis. Furthermore, P. gingivalis suppresses the generation of nitric oxide, a potent antimicrobial molecule, through its degradation, and incorporating its byproducts as a source of energy. Oral antimicrobial peptides can contribute to controlling the disease due to their antimicrobial and immunoregulatory activity, which allows them to maintain homeostasis in the oral cavity. This study aimed to analyze the immunopathological role of macrophages activated by P. gingivalis in periodontitis and suggested using antimicrobial peptides as therapeutic agents to treat the disease.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Emerging Trends and Focus in Human Skin Microbiome Over the Last Decade: A Bibliometric Analysis and Literature Review

Background

Human skin microbiome is the first barrier against exogenous attack and is associated with various skin disease pathogenesis and progression. Advancements in high-throughput sequencing technologies have paved the way for a deeper understanding of this field. Based on the bibliometric analysis, this investigation aimed to identify the hotspots and future research trends associated with human skin microbiomes studied over the past decade.

Methods

The published research on skin microbiome from January 2013 to January 2023 was retrieved from the Web of Science Core Collection. Data cleaning processes to ensure robust data and the bibliometrix packages R, CiteSpace, VOSviewer, Origin, and Scimago Graphica for bibliometric and visual analyses were utilized.

Results

A total of 1629 published documents were analyzed. The overall publication trend steadily increased, with relatively fast growth in 2017 and 2020. The United States of America has the highest number of publications and citations and shows close collaborations with China and Germany. The University of California, San Diego, indicated a higher number of publications than other institutions and the fastest growth rate. The top three most publishing journals on this topic are Microorganisms, Frontiers in Microbiology, and Experimental dermatology. Gallo RL is the most influential author with the highest h- and g-index and most publications in skin microecology, followed by Grice EA and Kong HH. The top 10 most frequently used keywords in recent years included skin microbiome, microbiome, staphylococcus aureus, diversity, atopic dermatitis, skin, bacteria, infections, gut microbiota, and disease.

Conclusion

The skin microbiome is an area of research that requires continuous analysis, and even with much-achieved progress, future research will further be aided as technology develops.

Human beta defensin-3 mediated activation of β-catenin during human respiratory syncytial virus infection: interaction of HBD3 with LDL receptor-related protein 5

Respiratory Syncytial Virus (RSV) is a non-segmented negative-sense RNA virus belonging to the paramyxovirus family. RSV infects the respiratory tract to cause pneumonia and bronchiolitis in infants, elderly, and immunocompromised patients. Effective clinical therapeutic options and vaccines to combat RSV infection are still lacking. Therefore, to develop effective therapeutic interventions, it is imperative to understand virus-host interactions during RSV infection. Cytoplasmic stabilization of β-catenin protein results in activation of canonical Wingless (Wnt)/β-catenin signaling pathway that culminates in transcriptional activation of various genes regulated by T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factors. This pathway is involved in various biological and physiological functions. Our study shows RSV infection of human lung epithelial A549 cells triggering β-catenin protein stabilization and induction of β-catenin mediated transcriptional activity. Functionally, the activated β-catenin pathway promoted a pro-inflammatory response during RSV infection of lung epithelial cells. Studies with β-catenin inhibitors and A549 cells lacking optimal β-catenin activity demonstrated a significant loss of pro-inflammatory chemokine interleukin-8 (IL-8) release from RSV-infected cells. Mechanistically, our studies revealed a role of extracellular human beta defensin-3 (HBD3) in interacting with cell surface Wnt receptor LDL receptor-related protein-5 (LRP5) to activate the non-canonical Wnt independent β-catenin pathway during RSV infection. We showed gene expression and release of HBD3 from RSV-infected cells and silencing of HBD3 expression resulted in reduced stabilization of β-catenin protein during RSV infection. Furthermore, we observed the binding of extracellular HBD3 with cell surface localized LRP5 protein, and our in silico and protein-protein interaction studies have highlighted a direct interaction of HBD3 with LRP5. Thus, our studies have identified the β-catenin pathway as a key regulator of pro-inflammatory response during RSV infection of human lung epithelial cells. This pathway was induced during RSV infection via a non-canonical Wnt-independent mechanism involving paracrine/autocrine action of extracellular HBD3 activating cell surface Wnt receptor complex by directly interacting with the LRP5 receptor.

Immunomodulatory Effects of the Pea Defensin Psd1 in the Caco-2/Immune Cells Co-Culture upon Candida albicans Infection

Candidiasis is one of the most common fungal diseases that can pose a threat to life in immunodeficient individuals, particularly in its disseminated form. Not only fungal invasion but also fatal infection-related inflammation are common causes of systemic candidiasis. In this study, we investigated in vitro immunomodulatory properties of the antifungal pea defensin Psd1 upon Candida albicans infection. Using the real-time PCR, we showed that Psd1 inhibited the antimicrobial peptide HBD-2 and pro-inflammatory cytokines IL-1 and IL-8 downregulation at mRNA level in epithelium cells caused by C. albicans infection. By using the Caco-2/immune cells co-culture upon C. albicans infection and the multiplex xMAP assay, we demonstrated that this pathogenic fungus induced a pronounced host defense response; however, the cytokine responses were different in the presence of dendritic cells or monocytes. We revealed that Psd1 at a low concentration (2 µM) had a pronounced immunomodulatory effect on the Caco-2/immune cells co-culture upon fungal infection. Thus, we hypothesized that the pea defensin Psd1 might be an effective agent in the treatment of candidiasis not only due to its antifungal activity, but also owing to its ability to modulate a protective immune response upon infection.

Vesicoureteral Reflux and Innate Immune System: Physiology, Physiopathology, and Clinical Aspects

Vesicoureteral reflux represents one of the most concerning topics in pediatric nephrology due to its frequency, clinical expression with the potential to evolve into chronic kidney disease, and last but not least, its socio-economic implications. The presence of vesicoureteral reflux, the occurrence of urinary tract infections, and the development of reflux nephropathy, hypertension, chronic kidney disease, and finally, end-stage renal disease represent a progressive spectrum of a single physiopathological condition. For the proper management of these patients with the best clinical outcomes, and in an attempt to prevent the spread of uropathogens' resistance to antibacterial therapy, we must better understand the physiopathology of urinary tract infections in patients with vesicoureteral reflux, and at the same time, we should acknowledge the implication and response of the innate immune system in this progressive pathological condition. The present paper focuses on theoretical aspects regarding the physiopathology of vesicoureteral reflux and the interconditionality between urinary tract infections and the innate immune system. In addition, we detailed aspects regarding cytokines, interleukins, antimicrobial peptides, and proteins involved in the innate immune response as well as their implications in the physiopathology of reflux nephropathy. New directions of study should focus on using these innate immune system effectors as diagnostic and therapeutic tools in renal pathology.

MSF Enhances Human Antimicrobial Peptide β-Defensin (HBD2 and HBD3) Expression and Attenuates Inflammation via the NF-κB and p38 Signaling Pathways

Both defensin and inflammation are part of the human innate immune system that responds rapidly to pathogens. The combination of defensins with pro- or anti-inflammatory effects can be a potential research direction for the treatment of infection by pathogens. This study aimed to identify whether MSF (Miracle Synergy material made using Filipendula glaberrima), a probiotic lysate of Filipendula glaberrima extracts fermented with Lactiplantibacillus plantarum K8, activates the expression of human β-defensin (HBD2 and HBD3) to protect the host against pathogens and inhibit inflammation caused by S. aureus, in vitro with Western blot analysis, qRT-PCR and in vivo studies with a mouse model were used to evaluate the effects of MSF. The MSF treatment induced HBD2 and HBD3 expression via the p38 and NF-κB pathways. Furthermore, MSF treatment significantly reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-8), also through p38 and NF-κB in S. aureus-induced inflammatory condition. MSF treatment remarkably reduced erythema in mice ears caused by the injection of S. aureus, while K8 lysate treatment did not initiate a strong recovery. Taken together, MSF induced the expression of HBD2 and HDB3 and activated anti-inflammatory activity more than the probiotic lysates of L. plantarum K8. These findings show that MSF is a potential defensin inducer and anti-inflammatory agent.

Role of Defensins in Tumor Biology

Defensins have long been considered as merely antimicrobial peptides. Throughout the years, more immune-related functions have been discovered for both the α-defensin and β-defensin subfamily. This review provides insights into the role of defensins in tumor immunity. Since defensins are present and differentially expressed in certain cancer types, researchers started to unravel their role in the tumor microenvironment. The human neutrophil peptides have been demonstrated to be directly oncolytic by permealizing the cell membrane. Further, defensins can inflict DNA damage and induce apoptosis of tumor cells. In the tumor microenvironment, defensins can act as chemoattractants for subsets of immune cells, such as T cells, immature dendritic cells, monocytes and mast cells. Additionally, by activating the targeted leukocytes, defensins generate pro-inflammatory signals. Moreover, immuno-adjuvant effects have been reported in a variety of models. Therefore, the action of defensins reaches beyond their direct antimicrobial effect, i.e., the lysis of microbes invading the mucosal surfaces. By causing an increase in pro-inflammatory signaling events, cell lysis (generating antigens) and attraction and activation of antigen presenting cells, defensins could have a relevant role in activating the adaptive immune system and generating anti-tumor immunity, and could thus contribute to the success of immune therapy.

Altered Expression of Antimicrobial Peptides in the Upper Gastrointestinal Tract of Patients with Diabetes Mellitus

Antimicrobial peptides (AMP) are essential components of innate immunity with a broad range of antimicrobial activities against bacteria, viruses, and fungi. The aim of this study was to investigate AMP expression in the upper gastrointestinal tract in normal and pathological metabolic states in humans. Furthermore, we examined the correlation between vitamin D levels and AMP expression in the same cohort. Serum concentrations of 25-hydroxyvitamin D3 were measured, and mRNA expression of β-defensins HBD-1, -2, -3, -4, α-defensins HD-5 and -6 and cathelicidin in the upper gastrointestinal tract epithelia were determined by quantitative RT-PCR in 31 individuals (10 with type 2 diabetes, 10 with insulin resistance, and 11 healthy controls). The majority of the cohort showed low vitamin D concentrations, which were negatively correlated with mRNA expression levels of HBD-3 in corpus mucosa. HBD-1 and HBD-3 mRNA were expressed in corpus mucosa, with the former significantly decreased in patients with diabetes. Hence, we conclude that type 2 diabetes is associated with reduced AMP expression in the upper gastrointestinal tract, which might contribute towards epithelial barrier dysfunction and increased bacterial translocation in these patients.

Anti-Cancer Peptides: Status and Future Prospects

The dramatic rise in cancer incidence, alongside treatment deficiencies, has elevated cancer to the second-leading cause of death globally. The increasing morbidity and mortality of this disease can be traced back to a number of causes, including treatment-related side effects, drug resistance, inadequate curative treatment and tumor relapse. Recently, anti-cancer bioactive peptides (ACPs) have emerged as a potential therapeutic choice within the pharmaceutical arsenal due to their high penetration, specificity and fewer side effects. In this contribution, we present a general overview of the literature concerning the conformational structures, modes of action and membrane interaction mechanisms of ACPs, as well as provide recent examples of their successful employment as targeting ligands in cancer treatment. The use of ACPs as a diagnostic tool is summarized, and their advantages in these applications are highlighted. This review expounds on the main approaches for peptide synthesis along with their reconstruction and modification needed to enhance their therapeutic effect. Computational approaches that could predict therapeutic efficacy and suggest ACP candidates for experimental studies are discussed. Future research prospects in this rapidly expanding area are also offered.

Human beta-defensin 1 circulating level and gene polymorphism in non-segmental vitiligo Egyptian patients

BACKGROUND

Vitiligo is an acquired depigmented skin disorder. It has a genetic and autoimmune background. Human beta defensin-1(HBD-1) plus its gene polymorphism were linked to some autoimmune disorders.

OBJECTIVE

To elucidate the possible role of HBD-1 in the pathogenesis of non-segmental vitiligo (NSV) through evaluation of HBD-1 serum levels and its single nucleotide polymorphism (SNP) in patients having NSV, in addition, to correlating the results with the extent of vitiligo in those patients.

METHODS

A current case-control study included 50 patients having NSV and 50 controls. The authors used Vitiligo Area Scoring Index (VASI) score to assess vitiligo severity and laboratory investigations to assess serum HBD-1 level using ELISA and defensin-beta1 (DEFB1) SNP using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

There were significantly lower HBD-1 serum levels in NSV cases than in controls (p < 0.001). There was a significant predominance of GG DEFB1 genotype and G allele in NSV patients in comparison to controls (p < 0.001). The levels of serum HBD-1 and DEFB1 genotypes were not associated or correlated significantly with any of the personal and clinical parameters of vitiligo patients.

STUDY LIMITATION

The small sample size.

CONCLUSIONS

DEFB1 gene polymorphism (GG genotype and G allele) may modulate vitiligo risk and contribute to vitiligo development in Egyptian populations. Decreased circulating HBD-1 levels might have an active role in vitiligo etiopathogenesis that could be mediated through its possible anti-inflammatory effects.

Bioactive peptides for anticancer therapies

Cancer is a serious concern in public health worldwide. Numerous modalities including surgery, radiotherapy, and chemotherapy, have been used for cancer therapies in clinic. Despite progress in anticancer therapies, the usage of these methods for cancer treatment is often related to deleterious side effects and multidrug resistance of conventional anticancer drugs, which have prompted the development of novel therapeutic methods. Anticancer peptides (ACPs), derived from naturally occurring and modified peptides, have received great attention in these years and emerge as novel therapeutic and diagnostic candidates for cancer therapies, because of several advantages over the current treatment modalities. In this review, the classification and properties of ACPs, the mode of action and mechanism of membrane disruption, as well as the natural sources of bioactive peptides with anticancer activities were summarised. Because of their high efficacy for inducing cancer cell death, certain ACPs have been developed to work as drugs and vaccines, evaluated in varied phases of clinical trials. We expect that this summary could facilitate the understanding and design of ACPs with increased specificity and toxicity towards malignant cells and with reduced side effects to normal cells.

Junctional epithelium and hemidesmosomes: Tape and rivets for solving the "percutaneous device dilemma" in dental and other permanent implants

The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the "device"/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant - as a model percutaneous device - placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists.

Evaluation of human β‑defensins in the cerebrospinal fluid of suspected meningitis

Human β-defensins (HBDs) are an important class of antimicrobial peptides that have immunomodulatory functions; however, the role of HBDs have not been well explored in the pathogenesis of meningitis. A cross-sectional study was performed to explore the levels of HBD1, HBD2, HBD3, and HBD4 in the cerebrospinal fluid (CSF) of 176 suspected meningitis cases. CSF samples were first subjected to PCR analysis using a set of universal primers targeting a portion of the eubacteria 16S rRNA gene. The analysis demonstrated that 66 samples (37.5%) were PCR-positive, whilst 110 samples (62.5%) were PCR-negative. DNA sequence analysis of the PCR-positive products identified two broad categories of bacteria, Gram-negative (68.2%) and Gram-positive (31.8%). A total of 88 PCR-negative CSF samples showed abnormal leukocyte counts, glucose concentrations, and/or protein concentrations, and were considered abnormal (ABN). The remaining 22 CSF samples were considered normal (NOR). HBD1, HBD2, and HBD4 levels did not exhibit significant differences between PCR-positive, ABN, and NOR CSF samples. However, HBD3 levels were significantly higher in the ABN CSF samples than in the NOR CSF samples (P=0.005). HBD3 levels were also elevated in the PCR-positive CSF samples compared with the NOR CSF samples, but the difference was not significant (P=0.151). HBD2, HBD3, and HBD4 were correlated with leukocyte counts, glucose concentration, and protein concentration. In conclusion, HBD3 levels were significantly elevated in the CSF of suspected meningitis cases regardless of the cause of meningitis. The CSF levels of certain HBDs were affected by specific diagnostic laboratory parameters for meningitis, including leukocyte counts, glucose concentration, and protein concentration.

Role of defensins in diabetic wound healing

The adverse consequences resulting from diabetes are often presented as severe complications. Diabetic wounds are one of the most commonly occurring complications in diabetes, and the control and treatment of this is costly. Due to a series of pathophysiological mechanisms, diabetic wounds remain in the inflammatory phase for a prolonged period of time, and face difficulty in entering the proliferative phase, thus leading to chronic non-healing wounds. The current consensus on the treatment of diabetic wounds is through multidisciplinary comprehensive management, however, standard wound treatment methods are still limited and therefore, more effective methods are required. In recent years, defensins have been found to play diverse roles in a variety of diseases; however, the molecular mechanisms underlying these activities are still largely unknown. Defensins can be constitutively or inductively produced in the skin, therefore, their local distribution is affected by the microenvironment of these diabetic wounds. Current evidence suggests that defensins are involved in the diabetic wound pathogenesis, and can potentially promote the early completion of each stage, thus making research on defensins a promising area for developing novel treatments for diabetic wounds. In this review, we describe the complex function of human defensins in the development of diabetic wounds, and suggest potential thera-peutic benefits.

Toll-like receptor-1, -2, and -6 genotypes in relation to salivary human beta-defensin-1, -2, -3 and human neutrophilic peptide-1

AIM

To examine whether functional gene polymorphisms of toll-like receptor (TLR)1, TLR2, and TLR6 are related to the salivary concentrations of human beta-defensins (hBDs)-1, -2, -3, and human neutrophilic peptide (HNP)-1.

MATERIALS AND METHODS

Polymorphisms of TLR1 (rs5743618), TLR2 (rs5743708), and TLR6 (rs5743810) were genotyped by PCR-based pyrosequencing from the salivary samples of 230 adults. Salivary hBD-1, -2, -3, and HNP-1 concentrations were measured using enzyme-linked immunosorbent assay. General and periodontal health examinations, including panoramic radiography, were available for all participants.

RESULTS

The genotype frequencies for wild types and variant types were as follows: 66.5% and 33.5% for TLR1, 95.5% and 4.5% for TLR2, and 25.1% and 74.9% for TLR6, respectively. The TLR2 heterozygote variant group exhibited higher salivary hBD-2 concentrations than the TLR2 wild-type group (p = .038). On the contrary, elevated hBD-2 concentrations were detected in the TLR6 wild-type group compared with the TLR6 heterozygote and homozygote variant group (p = .028). The associations between TLR6 genotypes and salivary hBD-2 concentrations remained significant after adjusting them for periodontal status, age, and smoking.

CONCLUSION

hBD-2 concentrations in saliva are related to TLR2 and TLR6 polymorphisms, but only the TLR6 genotype seems to exhibit an independent association with the salivary hBD-2 concentrations.

Inflammatory bowel disease-associated adherent-invasive Escherichia coli have elevated host-defense peptide resistance

Adherent-invasive Escherichia coli (AIEC) are isolated from inflammatory bowel disease (IBD) patients at a higher rate than from control patients. Using a collection of E. coli strains collected from Crohn's disease (CD), ulcerative colitis (UC), or non-IBD control patients, antibiotic and resistance to the antimicrobial peptides HBD-3 and LL-37 was assessed. Carriage of bacterial-encoded omptin protease genes was assessed by PCR and omptin protease activity was measured using a whole-cell based fluorescence assay. Elevated resistance to antibiotics and host defense peptides in IBD-associated AIEC were observed. IBD-associated strains showed increased (but statistically non-significant) antibiotic resistance. CD-associated strains showed greater (but statistically non-significant) resistance to HBD3-mediated killing while UC-associated strains showed statistically greater resistance to LL-37 mediated killing. High-level resistance to LL-37 was associated with carriage of omptin protease genes and with increased omptin protease activity. Antimicrobial host defense peptide resistance may be an adaptive feature of AIEC leading to enhanced pathogenesis during the initiation or progression of IBD.

Composite immune marker scores associated with severe mental disorders and illness course

Background

Low-grade inflammation has been implicated in the pathophysiology of severe mental disorders (SMDs) and a link between immune activation and clinical characteristics is suggested. However, few studies have investigated how patterns across immune markers are related to diagnosis and illness course.

Methods

A total of 948 participants with a diagnosis of schizophrenia (SCZ, N = 602) or bipolar (BD, N = 346) spectrum disorder, and 814 healthy controls (HC) were included. Twenty-five immune markers comprising cell adhesion molecules (CAMs), interleukin (IL)-18-system factors, defensins, chemokines and other markers, related to neuroinflammation, blood-brain barrier (BBB) function, inflammasome activation and immune cell orchestration were analyzed. Eight immune principal component (PC) scores were constructed by PC Analysis (PCA) and applied in general linear models with diagnosis and illness course characteristics.

Results

Three PC scores were significantly associated with a SCZ and/or BD diagnosis (HC reference), with largest, however small, effect sizes of scores based on CAMs, BBB markers and defensins (p < 0.001, partial η² = 0.02–0.03). Number of psychotic episodes per year in SCZ was associated with a PC score based on IL-18 system markers and the potential neuroprotective cytokine A proliferation-inducing ligand (p = 0.006, partial η² = 0.071).

Conclusion

Analyses of composite immune markers scores identified specific patterns suggesting CAMs-mediated BBB dysregulation pathways associated with SMDs and interrelated pro-inflammatory and neuronal integrity processes associated with severity of illness course. This suggests a complex pattern of immune pathways involved in SMDs and SCZ illness course.

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Composite score of VCAM-1, ICAM-1, NCAD and IL-18BP associated with SCZ and BD.

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Composite score of MadCAM-1 and BD-1 associated with SCZ and BD.

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Composite score of S100B, furin, HNP1-3 and BD-1 associated with BD.

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Composite score of APRIL and IL-18R markers associated with psychotic episode rate.

Could AMPs and B-cells be the missing link in understanding periodontitis?

Periodontal diseases are common inflammatory conditions characterized by bone loss in response to simultaneous bacterial aggression and host defenses. The etiology of such diseases is still not completely understood, however. It has been shown that specific pathogens involved in the build-up of dysbiotic biofilms participate actively in the establishment of periodontitis. This multifactorial pathology also depends on environmental factors and host characteristics, especially defenses. The immune response to the pathogens seems to be critical in preventing the disease from starting but also contributes to tissue damage. It is known that small molecules known as antimicrobial peptides (AMPs) are key actors in the innate immune response. They not only target microbes, but also act as immuno-modulators. They can help to recruit or activate cells such as neutrophils, monocytes, dendritic cells, or lymphocytes. AMPs have already been described in the periodontium, and their expression seems to be connected to disease activity. Alpha and beta defensins and LL37 are the AMPs most frequently linked to periodontitis. Additionally, leukocyte infiltrates, especially B-cells, have also been linked to the severity of periodontitis. Indeed, the particular subpopulations of B-cells in these infiltrates have been linked to inflammation and bone resorption. A link between B-cells and AMP could be relevant to understanding B-cells' action. Some AMP receptors, such as chemokines receptors, toll-like receptors, or purinergic receptors, have been shown to be expressed by B-cells. Consequently, the action of AMPs on B-cell subpopulations could participate to B-cell recruitment, their differentiation, and their implication in both periodontal defense and destruction.

Defensins: defenders of human reproductive health

BACKGROUND

Reproductive tract infection is an important factor leading to male and female infertility. Among female infertility factors, microbial and viral infections are the main factors affecting female reproductive health and causing tubal infertility, ectopic tubal pregnancy and premature delivery. Among male infertility factors, 13-15% of male infertility is related to infection. Defensins are cationic antibacterial and antiviral peptides, classified into α-defensins, β-defensins and θ-defensins. Humans only have α-defensins and β-defensins. Apart from their direct antimicrobial functions, defensins have an immunomodulatory function and are involved in many physiological processes. Studies have shown that defensins are widely distributed in the female reproductive tract (FRT) and male reproductive tract (MRT), playing a dual role of host defence and fertility protection. However, to our knowledge, the distribution, regulation and function of defensins in the reproductive tract and their relation to reproduction have not been reviewed.

OBJECTIVE AND RATIONALE

This review summarizes the expression, distribution and regulation of defensins in the reproductive tracts to reveal the updated research on the dual role of defensins in host defence and the protection of fertility.

SEARCH METHODS

A systematic search was conducted in PubMed using the related keywords through April 2022. Related data from original researches and reviews were integrated to comprehensively review the current findings and understanding of defensins in the human reproductive system. Meanwhile, female and male transcriptome data in the GEO database were screened to analyze defensins in the human reproductive tracts.

OUTCOMES

Two transcriptome databases from the GEO database (GSE7307 and GSE150852) combined with existing researches reveal the expression levels and role of the defensins in the reproductive tracts. In the FRT, a high expression level of α-defensin is found, and the expression levels of defensins in the vulva and vagina are higher than those in other organs. The expression of defensins in the endometrium varies with menstrual cycle stages and with microbial invasion. Defensins also participate in the local immune response to regulate the risk of spontaneous preterm birth. In the MRT, a high expression level of β-defensins is also found. It is mainly highly expressed in the epididymal caput and corpus, indicating that defensins play an important role in sperm maturation. The expression of defensins in the MRT varies with androgen levels, age and the status of microbial invasion. They protect the male reproductive system from bacterial infections by neutralizing lipopolysaccharide and downregulating pro-inflammatory cytokines. In addition, animal and clinical studies have shown that defensins play an important role in sperm maturation, motility and fertilization.

WIDER IMPLICATIONS

As a broad-spectrum antimicrobial peptide without drug resistance, defensin has great potential for developing new natural antimicrobial treatments for reproductive tract infections. However, increasing evidence has shown that defensins can not only inhibit microbial invasion but can also promote the invasion and adhesion of some microorganisms in certain biological environments, such as human immunodeficiency virus. Therefore, the safety of defensins as reproductive tract anti-infective drugs needs more in-depth research. In addition, the modulatory role of defensins in fertility requires more in-depth research since the current conclusions are based on small-size samples. At present, scientists have made many attempts at the clinical transformation of defensins. However, defensins have problems such as poor stability, low bioavailability and difficulties in their synthesis. Therefore, the production of safe, effective and low-cost drugs remains a challenge.

Transcriptome Analysis Reveals the Multiple Functions of pBD2 in IPEC-J2 Cells against E. coli

Defensins play an important role in fighting bacteria, and are a good candidate for bactericidal agents. However, the function and mechanism of defensins in regulating host responses against bacteria is unclear. In this study, transcriptome analysis was used to study the comprehensive functions of pBD2 in IPEC-J2 cells against E. coli. In total, 230 differentially expressed genes (DEGs) were identified in IPEC-J2 cells between the control and E. coli groups, and were found by KEGG analysis to be involved in many signaling pathways related to immunity. Furthermore, 812 DEGs were observed between E. coli and E. coli +pBD2 groups, involved in the ribosome, oxidative phosphorylation, and certain disease pathways. Among these, 94 overlapping DEGs were in the two DEG groups, and 85 DEGs were reverse expression, which is involved in microRNA in cancer, while PTEN and CDC6 were key genes according to PPI net analysis. The results of qRT-PCR verified those of RNA-seq. The results indicated that pBD2 plays an important role against E. coli by acting on the genes related to immune response, cell cycle, ribosomes, oxidative phosphorylation, etc. The results provide new insights into the potential function and mechanism of pBD2 against E. coli. Meanwhile, this study provides a certain theoretical basis for research and the development of novel peptide drugs.

N-Acetylcysteine and Other Sulfur-Donors as a Preventative and Adjunct Therapy for COVID-19

The airway epithelial glycocalyx plays an important role in preventing severe acute respiratory syndrome coronavirus 2 entry into the epithelial cells, while the endothelial glycocalyx contributes to vascular permeability and tone, as well as modulating immune, inflammatory, and coagulation responses. With ample evidence in the scientific literature that coronavirus disease 2019 (COVID-19) is related to epithelial and endothelial dysfunction, preserving the glycocalyx should be the main focus of any COVID-19 treatment protocol. The most studied functional unit of the glycocalyx is the glycosaminoglycan heparan sulfate, where the degree and position of the sulfate groups determine the biological activity. N-acetylcysteine (NAC) and other sulfur donors contribute to the inorganic sulfate pool, the rate-limiting molecule in sulfation. NAC is not only a precursor to glutathione but also converts to hydrogen sulfide, inorganic sulfate, taurine, Coenzyme A, and albumin. By optimising inorganic sulfate availability, and therefore sulfation, it is proposed that COVID-19 can be prevented or at least most of the symptoms attenuated. A comprehensive COVID-19 treatment protocol is needed to preserve the glycocalyx in both the prevention and treatment of COVID-19. The use of NAC at a dosage of 600 mg bid for the prevention of COVID-19 is proposed, but a higher dosage of NAC (1200 mg bid) should be administered upon the first onset of symptoms. In the severe to critically ill, it is advised that IV NAC should be administered immediately upon hospital admission, and in the late stage of the disease, IV sodium thiosulfate should be considered. Doxycycline as a protease inhibitor will prevent shedding and further degradation of the glycocalyx.

“Iron triangle” of regulating the uterine microecology: Endometrial microbiota, immunity and endometrium

The uterus is the core place for breeding new life. The balance and imbalance of uterine microecology can directly affect or even dominate the female reproductive health. Emerging data demonstrate that endometrial microbiota, endometrium and immunity play an irreplaceable role in regulating uterine microecology, forming a dynamic iron triangle relationship. Up to nowadays, it remains unclear how the three factors affect and interact with each other, which is also a frontier topic in the emerging field of reproductive tract microecology. From this new perspective, we aim to clarify the relationship and mechanism of the interaction of these three factors, especially their pairwise interactions. Finally, the limitations and future perspectives of the current studies are summarized. In general, these three factors have a dynamic relationship of mutual dependence, promotion and restriction under the physiological or pathological conditions of uterus, among which the regulatory mechanism of microbiota and immunity plays a role of bridge. These findings can provide new insights and measures for the regulation of uterine microecology, the prevention and treatment of endometrial diseases, and the further multi-disciplinary integration between microbiology, immunology and reproductive medicine.

Glycosaminoglycan, Antimicrobial Defence Molecule and Cytokine Appearance in Tracheal Hyaline Cartilage of Healthy Humans

Hyaline cartilage is an important tracheal structure, yet little is known about its molecular composition, complicating investigation of pathologies and replacement options. Our aim was to research tracheal hyaline cartilage structure, protective tissue factors and variations in healthy humans. The tissue material was obtained from 10 cadavers obtained from the Riga Stradins University Institute of Anatomy and Anthropology archive. Tissues were stained with Bismarck brown and PAS for glycosaminoglycans, and immunohistochemistry was performed for HBD-2, HBD-3, HBD-4, IL-10 and LL-37. The slides were inspected by light microscopy and Spearman's rank correlation coefficient was calculated. The extracellular matrix was positive across hyaline cartilage for PAS, yet Bismarck brown marked positive proliferation and growth zones. Numerous positive cells for both factors were found in all zones. All of the antimicrobial defence molecules and cytokines were found in a moderate number of cells, except in the mature cell zone with few positive cells. Spearman's rank correlation coefficient revealed strong and moderate correlations between studied factors. Hyaline cartilage is a tracheal defence structure with a moderate number of antimicrobial defence protein and cytokine immunoreactive cells as well as numerous glycosaminoglycan positive cells. The extracellular matrix glycosaminoglycans provide structural scaffolding and intercellular signalling. The correlations between the studied factors confirm the synergistic activity of them.

Evaluation of the multiple tissue factors in bone of primary osteoplasty and rhinoplasty in patients affected by cleft lip palate

Clefts of the lip and/or palate (CLP) are visible disruptions of standard facial structure. The aim of our study was to determine a relative number and appearance of the tissue factors in bone of patients with CLP during first time plastic alveolar osteoplasty or rhinoplasty. Immunohistochemistry was performed with matrix metalloproteinase-8 (MMP-8), matrix metalloproteinase-9 (MMP-9), osteopontin (OPN), osteocalcin (OC), Runt-related transcription factor 2 (Runx2), beta-defensin-2 (βdef-2), beta-defensin-3 (βdef-3), interleukin-1 alpha (IL-1α), and interleukin-10 (IL-10). The bone formation was observed by Masson-trichrome (Masson) staining. For the quantification of structures, the semi-quantitative census method was used. Spearman rank order correlation coefficient and Mann-Whitney U test were used for the statistical analysis. A significantly higher number of OPN positive osteocytes was observed in the CLP group when compared to the control group (p=0.002). The number of OC positive osteocytes (p=0.000) and βdef-2 positive osteocytes (p=0.003) was significantly lower in the CLP group in comparison to the control group. Strong, positive correlations between IL-10 and OC (rs=0.608; p=0.002), IL-1α and MMP-9 (rs=0.666; p=0.000), OPN and MMP-8 (rs=0.620; p=0.002) were detected in the CLP group. A tendency for the increased appearance of MMP-8, MMP-9 positive osteocytes of the patients with CLP, suggests elevated tissue remodelling properties. Increased appearance of OPN positive osteocytes in bone of the patients with CLP shows increased bone homeostasis based on seriously decreased mineralization, which may be a possible compensatory reaction to decreased quality of postsurgical bone.

The recombinant defensin/HSA fusion protein that inhibits NF-κb associated with intensive macropinocytosis shows potent efficacy against pancreatic cancer

KRAS mutation and NF-κB both play crucial role in pancreatic cancer; in addition, defensin, the peptide mediator in innate immunity, can inhibit NF-κB. Assuming a strategy that targets both NF-κB and concomitantly the mutated KRAS indirectly via intensive macropinocytosis, we designed and generated a recombinant protein DF2-HSA which consists of two molecules of human beta-defensin 2 (HBD2) and a moiety of human serum albumin (HSA). As shown, the recombinant protein DF2-HSA markedly down-regulated NF-κB in both KRAS mutant MIA PaCa-2 cells and wild type BxPC-3 cells. Determined by confocal microscopy, the uptake of DF2-HSA in MIA PaCa-2 cells was more intense than that in BxPC-3 cells. The uptake was blocked by the specific inhibitor EIPA, indicating that DF2-HSA internalized via macropinocytosis. DF2-HSA displayed more potent cytotoxicity to cancer cells than HBD2. DF2-HSA induced apoptosis in cancer cells. Notably, DF2-HSA inhibited tumor cell spheroid formation, an effect comparable to that of salinomycin. DF2-HSA inhibited tumor cell migration and invasion. As detected with scanning electron microscopy, DF2-HSA strongly depleted filopodia on cell surface; and salinomycin induced similar changes. By in vivo imaging, DF2-HSA displayed intense tumor-site accumulation and lasting retention for over 14 days; however, HBD2 showed much less tumor-site accumulation and a shorter retention time for only 24 h. DF2-HSA suppressed the growth of pancreatic cancer MIA PaCa-2 xenograft in athymic mice; and its combination with gemcitabine achieved higher antitumor efficacy. In summary, the recombinant defensin/HSA fusion protein that inhibits NF-κb associated with intensive macropinocytosis is highly effective against pancreatic cancer.

Antimicrobial Peptide Expression at the Ocular Surface and Their Therapeutic Use in the Treatment of Microbial Keratitis

Microbial keratitis is a common cause of ocular pain and visual impairment worldwide. The ocular surface has a relatively paucicellular microbial community, mostly found in the conjunctiva, while the cornea would be considered relatively sterile. However, in patients with microbial keratitis, the cornea can be infected with multiple pathogens including Staphylococcus aureus, Pseudomonas aeruginosa, and Fusarium sp. Treatment with topical antimicrobials serves as the standard of care for microbial keratitis, however, due to high rates of pathogen resistance to current antimicrobial medications, alternative therapeutic strategies must be developed. Multiple studies have characterized the expression and activity of antimicrobial peptides (AMPs), endogenous peptides with key antimicrobial and wound healing properties, on the ocular surface. Recent studies and clinical trials provide promise for the use of AMPs as therapeutic agents. This article reviews the repertoire of AMPs expressed at the ocular surface, how expression of these AMPs can be modulated, and the potential for harnessing the AMPs as potential therapeutics for patients with microbial keratitis.

Strategies to Improve the Activity and Biocompatibility: Modification of Peptide Antibiotics

As host defense peptides, peptide antibiotics exist in almost all organisms. Many of their activities come from their inactivation of bacteria, yeast, fungi, and even cancer cells. However, natural peptide antibiotics are relatively poor in stability and penetration, and have high hemolytic properties, which makes them difficult to directly apply. Therefore, natural peptide antibiotics can be modified to enhance their activity and biocompatibility. Based on the characteristics of amino acids, amino acid substitutions can be performed to study the effect of amino acid types on the activity of peptide antibiotics. The design of ultrashort peptides, cyclic peptides, and self-assembling peptides is also a way to improve the activity of peptide antibiotics. In addition, antibacterial peptides can also be conjugated with antibiotics, lipids, or metal ions to prepare antibacterial peptides with special activities. This review introduces several methods for modifying peptide antibiotics and their specific applications, providing a theoretical basis for the further application of peptide antibiotics.

CCR6 activation links innate immune responses to mucosa-associated lymphoid tissue lymphoma development

The genesis of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is driven by oncogenic co-operation among immunological stimulations and acquired genetic changes. We previously identified recurrent CCR6 mutations in MALT lymphoma, with majority predicted to result in truncated proteins lacking the phosphorylation motif important for receptor desensitization. Functional consequences of these mutational changes, the molecular mechanisms of CCR6 activation and how this receptor signaling contributes to MALT lymphoma development remain to be investigated. In the present study, we demonstrated that these mutations impaired CCR6 receptor internalization and were activating changes, being more potent in apoptosis resistance, malignant transformation, migration and intracellular signaling, particularly in the presence of the ligands CCL20, HBD2 (human b defensin 2) and HD5 (human a defensin 5). CCR6 was highly expressed in malignant B cells irrespective of the lymphoma sites. HBD2 and CCL20 were constitutively expressed by the duct epithelial cells of salivary glands, and also those involved in lymphoepithelial lesions (LEL) in salivary gland MALT lymphoma. While in the gastric setting, HBD2, and HD5, to a less extent CCL20, were highly expressed in epithelial cells of pyloric and intestinal metaplasia respectively including those involved in LEL, which are adaptive responses to chronic Helicobacter pylori infection. These findings suggest that CCR6 signaling is most likely active in MALT lymphoma, independent of its mutation status. The observations explain why the emergence of malignant B cells and their clonal expansion in MALT lymphoma are typically around LEL, linking the innate immune responses to lymphoma genesis.

Recombinant porcine beta defensin 2 alleviates inflammatory responses induced by Escherichia coli in IPEC-J2 cells

pBD2 is one of the porcine beta defensins with broad antimicrobial activity, and plays an important role in immune regulation. However, the activities and mechanisms of pBD2 regulating host resistance to Escherichia coli infection are unclear. In this study, the immunomodulatory activity and mechanisms of recombinant pBD2 against Escherichia coli infection were explored in IPEC-J2 cells. Recombinant pBD2 had no obvious effect on the growth of cells below 80 μg/mL, however, it reduced the number of E. coli adhering to cells. Furthermore, pBD2 restored the abnormal expression of ZO-1 and occludin in cells challenged with E. coli. pBD2 treatment also reduced cell apoptosis and decreased the expression of the apoptosis-related genes Cox-2 and Caspase-3, and decreased the expression of the pro-inflammatory IL-6, IL-8, IL-1α and TNF-α, and Cxcl2 and Ccl20. pBD2 also reduced the expression of TAK1, and inhibited the phosphorylation of NF-κB p65 following E. coli infection. In addition, pBD2 was localized in the cytoplasm. Collectively, pBD2 appeared to penetrate cells and alleviate inflammatory responses via the TAK1-NF-κB signaling pathway. Our results revealed the immunomodulatory activity of recombinant pBD2 against E. coli and provided insights into the molecular mechanisms that protected cells from E. coli infection.

Expression of Antimicrobial Peptide Genes in the Canine Amniotic Membrane

The human amniotic membrane has been successfully used in human ocular reconstruction. Several studies have demonstrated its properties, including antimicrobial features. As a result of the restricted availability of human amniotic membrane for veterinary use, canine amniotic membrane has become an attractive alternative. Clinical studies of the application of canine amniotic membrane in animals and the understanding of its biological properties are limited. This study aimed to determine the expression of peptide genes of natural antimicrobials in canine amniotic membrane. Expressions of canine β-defensin 1, 102, and 103, and canine Elafin were determined in healthy puppies by real-time quantitative polymerase chain reaction. Canine β-defensin 1, 103, and Elafin were expressed in all samples, possibly suggesting a role in the innate immune system of normal canine amniotic membrane. Further investigations of protein expression and localization are recommended.

Host Defence Peptides: A Potent Alternative to Combat Antimicrobial Resistance in the Era of the COVID-19 Pandemic

One of the greatest challenges facing the medical community today is the ever-increasing trajectory of antimicrobial resistance (AMR), which is being compounded by the decrease in our antimicrobial armamentarium. From their initial discovery to the current day, antibiotics have seen an exponential increase in their usage, from medical to agricultural use. Benefits aside, this has led to an exponential increase in AMR, with the fear that over 10 million lives are predicted to be lost by 2050, according to the World Health Organisation (WHO). As such, medical researchers are turning their focus to discovering novel alternatives to antimicrobials, one being Host Defence Peptides (HDPs). These small cationic peptides have shown great efficacy in being used as an antimicrobial therapy for currently resistant microbial variants. With the sudden emergence of the SARS-CoV-2 variant and the subsequent global pandemic, the great versatility and potential use of HDPs as an alternative to conventional antibiotics in treating as well as preventing the spread of COVID-19 has been reviewed. Thus, to allow the reader to have a full understanding of the multifaceted therapeutic use of HDPs, this literature review shall cover the association between COVID-19 and AMR whilst discussing and evaluating the use of HDPs as an answer to antimicrobial resistance (AMR).

Defensin-lipid interactions in membrane targeting: mechanisms of action and opportunities for the development of antimicrobial and anticancer therapeutics

Defensins are a class of host defence peptides (HDPs) that often harbour antimicrobial and anticancer activities, making them attractive candidates as novel therapeutics. In comparison with current antimicrobial and cancer treatments, defensins uniquely target specific membrane lipids via mechanisms distinct from other HDPs. Therefore, defensins could be potentially developed as therapeutics with increased selectivity and reduced susceptibility to the resistance mechanisms of tumour cells and infectious pathogens. In this review, we highlight recent advances in defensin research with a particular focus on membrane lipid-targeting in cancer and infection settings. In doing so, we discuss strategies to harness lipid-binding defensins for anticancer and anti-infective therapies.

PEGylation enhances the antibacterial and therapeutic potential of amphibian host defence peptides

Aurein 2.1, aurein 2.6 and aurein 3.1 are amphibian host defence peptides that kill bacteria via the use of lytic amphiphilic α-helical structures. The C-terminal PEGylation of these peptides led to decreased antibacterial activity (Minimum Lethal Concentration (MLCs) ↓ circa one and a half to threefold), reduced levels of amphiphilic α-helical structure in solvents (α-helicity ↓ circa 15.0%) and lower surface activity (Δπ ↓ > 1.5 mN m^-1). This PEGylation of aureins also led to decreased levels of amphiphilic α-helical structure in the presence of anionic membranes and zwitterionic membranes (α-helicity↓ > 10.0%) as well as reduced levels of penetration (Δπ ↓ > 3.0 mN m^-1) and lysis (lysis ↓ > 10.0%) of these membranes. Based on these data, it was proposed that the antibacterial action of PEGylated aureins involved the adoption of α-helical structures that promote the lysis of bacterial membranes, but with lower efficacy than their native counterparts. However, PEGylation also reduced the haemolytic activity of native aureins to negligible levels (haemolysis ↓ from circa 10% to 3% or less) and improved their relative therapeutic indices (RTIs ↑ circa three to sixfold). Based on these data, it is proposed that PEGylated aureins possess the potential for therapeutic development; for example, to combat infections due to multi-drug resistant strains of S. aureus, designated as high priority by the World Health Organization.

[Mucosal immunity and vaccines against viral infections]

Mucosal immunity is realized through a structural and functional system called mucose-associated lymphoid tissue (MALT). MALT is subdivided into parts (clusters) depending on their anatomical location, but they all have a similar structure: mucus layer, epithelial tissue, lamina propria and lymphoid follicles. Plasma cells of MALT produce a unique type of immunoglobulins, IgA, which have the ability to polymerize. In mucosal immunization, the predominant form of IgA is a secretory dimer, sIgA, which is concentrated in large quantities in the mucosa. Mucosal IgA acts as a first line of defense and neutralizes viruses efficiently at the portal of entry, preventing infection of epithelial cells and generalization of infection. To date, several mucosal antiviral vaccines have been licensed, which include attenuated strains of the corresponding viruses: poliomyelitis, influenza, and rotavirus. Despite the tremendous success of these vaccines, in particular, in the eradication of poliomyelitis, significant disadvantages of using attenuated viral strains in their composition are the risk of reactogenicity and the possibility of reversion to a virulent strain during vaccination. Nevertheless, it is mucosal vaccination, which mimics a natural infection, is able to induce a fast and effective immune response and thus help prevent and possibly stop outbreaks of many viral infections. Currently, a number of intranasal vaccines based on a new vector approach are successfully undergoing clinical trials. In these vaccines, the safe viral vectors are used to deliver protectively significant immunogens of pathogenic viruses. The most tested vector for intranasal vaccines is adenovirus, and the most significant immunogen is SARSCoV-2 S protein. Mucosal vector vaccines against human respiratory syncytial virus and human immunodeficiency virus type 1 based on Sendai virus, which is able to replicate asymptomatically in cells of bronchial epithelium, are also being investigated.

[The assessment of a role of muramyl peptides in the treatment of patients with aggressive form of periodontitis]

THE AIM OF THE STUDY

Was to determine the effect of the drug based on the composition of muramyl peptides isolated from the cell walls of gram-negative bacteria on the production of α-defensins and the detectability of Porphyromonas gingivalis in patients with an aggressive form of periodontitis.

MATERIAL AND METHODS

60 patients aged 28 to 40 years with an aggressive form of periodontitis were randomized into two equal groups, the main and control. In both groups, patients were removed dental deposits and taught the rules of oral hygiene, followed by three-fold control. In the main group, 200 micrograms of the drug based on the composition of muramyl peptides were additionally administered intramuscularly daily for 7 days. Initially and after 7, 21, 90 days, the level of human neutrophil peptides (hnp_1-3) in blood serum and periodontal pockets was determined by the enzyme immunoassay, as well as the presence of P. gingivalis in periodontal pockets by polymerase chain reaction (PCR).

RESULTS

In patients of the control group, the concentration of hnp_1-3 in periodontal pockets and blood serum did not change significantly during the entire study. The use of PM in the main group caused an increase in the local and systemic levels of hnp_1-3, which correlated with a persistent decrease in the detectability of P. gingivalis.

CONCLUSION

The drug based on the composition of muramyl peptides of the cell wall of gram-negative bacteria potentiates the eradication of P. gingivalis by stimulating the production of hnp_1-3 in patients with an aggressive form of periodontitis.

Innate Immunity as an Executor of the Programmed Death of Individual Organisms for the Benefit of the Entire Population

In humans, over-activation of innate immunity in response to viral or bacterial infections often causes severe illness and death. Furthermore, similar mechanisms related to innate immunity can cause pathogenesis and death in sepsis, massive trauma (including surgery and burns), ischemia/reperfusion, some toxic lesions, and viral infections including COVID-19. Based on the reviewed observations, we suggest that such severe outcomes may be manifestations of a controlled suicidal strategy protecting the entire population from the spread of pathogens and from dangerous pathologies rather than an aberrant hyperstimulation of defense responses. We argue that innate immunity may be involved in the implementation of an altruistic programmed death of an organism aimed at increasing the well-being of the whole community. We discuss possible ways to suppress this atavistic program by interfering with innate immunity and suggest that combating this program should be a major goal of future medicine.

Pathogenesis of COVID-19 described through the lens of an undersulfated and degraded epithelial and endothelial glycocalyx

The glycocalyx surrounds every eukaryotic cell and is a complex mesh of proteins and carbohydrates. It consists of proteoglycans with glycosaminoglycan side chains, which are highly sulfated under normal physiological conditions. The degree of sulfation and the position of the sulfate groups mainly determine biological function. The intact highly sulfated glycocalyx of the epithelium may repel severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) through electrostatic forces. However, if the glycocalyx is undersulfated and 3-O-sulfotransferase 3B (3OST-3B) is overexpressed, as is the case during chronic inflammatory conditions, SARS-CoV-2 entry may be facilitated by the glycocalyx. The degree of sulfation and position of the sulfate groups will also affect functions such as immune modulation, the inflammatory response, vascular permeability and tone, coagulation, mediation of sheer stress, and protection against oxidative stress. The rate-limiting factor to sulfation is the availability of inorganic sulfate. Various genetic and epigenetic factors will affect sulfur metabolism and inorganic sulfate availability, such as various dietary factors, and exposure to drugs, environmental toxins, and biotoxins, which will deplete inorganic sulfate. The role that undersulfation plays in the various comorbid conditions that predispose to coronavirus disease 2019 (COVID-19), is also considered. The undersulfated glycocalyx may not only increase susceptibility to SARS-CoV-2 infection, but would also result in a hyperinflammatory response, vascular permeability, and shedding of the glycocalyx components, giving rise to a procoagulant and antifibrinolytic state and eventual multiple organ failure. These symptoms relate to a diagnosis of systemic septic shock seen in almost all COVID-19 deaths. The focus of prevention and treatment protocols proposed is the preservation of epithelial and endothelial glycocalyx integrity.