Antimicrobial polypeptides

Interplay between group A Streptococcus and host innate immune responses

SUMMARYGroup A Streptococcus (GAS), also known as Streptococcus pyogenes, is a clinically well-adapted human pathogen that harbors rich virulence determinants contributing to a broad spectrum of diseases. GAS is capable of invading epithelial, endothelial, and professional phagocytic cells while evading host innate immune responses, including phagocytosis, selective autophagy, light chain 3-associated phagocytosis, and inflammation. However, without a more complete understanding of the different ways invasive GAS infections develop, it is difficult to appreciate how GAS survives and multiplies in host cells that have interactive immune networks. This review article attempts to provide an overview of the behaviors and mechanisms that allow pathogenic GAS to invade cells, along with the strategies that host cells practice to constrain GAS infection. We highlight the counteractions taken by GAS to apply virulence factors such as streptolysin O, nicotinamide-adenine dinucleotidase, and streptococcal pyrogenic exotoxin B as a hindrance to host innate immune responses.

Balancing Act of the Intestinal Antimicrobial Proteins on Gut Microbiota and Health

The human gut houses a diverse and dynamic microbiome critical for digestion, metabolism, and immune development, exerting profound effects on human health. However, these microorganisms pose a potential threat by breaching the gut barrier, entering host tissues, and triggering infections, uncontrolled inflammation, and even sepsis. The intestinal epithelial cells form the primary defense, acting as a frontline barrier against microbial invasion. Antimicrobial proteins (AMPs), produced by these cells, serve as innate immune effectors that regulate the gut microbiome by directly killing or inhibiting microbes. Abnormal AMP production, whether insufficient or excessive, can disturb the microbiome equilibrium, contributing to various intestinal diseases. This review delves into the complex interactions between AMPs and the gut microbiota and sheds light on the role of AMPs in governing host-microbiota interactions. We discuss the function and mechanisms of action of AMPs, their regulation by the gut microbiota, microbial evasion strategies, and the consequences of AMP dysregulation in disease. Understanding these complex interactions between AMPs and the gut microbiota is crucial for developing strategies to enhance immune responses and combat infections within the gut microbiota. Ongoing research continues to uncover novel aspects of this intricate relationship, deepening our understanding of the factors shaping gut health. This knowledge has the potential to revolutionize therapeutic interventions, offering enhanced treatments for a wide range of gut-related diseases.

Lysozyme: A Natural Product with Multiple and Useful Antiviral Properties

Lysozyme, especially the one obtained from hen's egg white, continues to show new pharmacological properties. The fact that only a few of these properties can be translated into therapeutic applications is due to the lack of suitable clinical studies. However, this lack cannot hide the evidence that is emerging from scientific research. This review for the first time examines, from a pharmacological point of view, all the relevant studies on the antiviral properties of lysozyme, analyzing its possible mechanism of action and its ability to block viral infections and, in some cases, inhibit viral replication. Lysozyme can interact with nucleic acids and alter their function, but this effect is uncoupled from the catalytic activity that determines its antibacterial activity; it is present in intact lysozyme but is equally potent in a heat-degraded lysozyme or in a nonapeptide isolated by proteolytic digestion. An analysis of the literature shows that lysozyme can be used both as a disinfectant for raw and processed foods and as a drug to combat viral infections in animals and humans. To summarize, it can be said that lysozyme has important antiviral properties, as already suspected in the initial studies conducted over 50 years ago, and it should be explored in suitable clinical studies on humans.

Alpha-defensins inhibit ERK/STAT3 signaling during monocyte-macrophage differentiation and impede macrophage function

Alpha-1-antitrypsin deficiency (AATD) is a genetic disorder associated with a 5-tenfold decrease in lung levels of alpha-1-antitrypsin (AAT) and an increased risk for obstructive lung disease. α-defensins are cationic broad-spectrum cytotoxic and pro-inflammatory peptides found in the azurophilic granules of neutrophils. The concentration of α-defensins is less than 30 nM in the bronchoalveolar lavage fluid of healthy controls but is up to 6 μM in AATD individuals with significant lung function impairment. Alveolar macrophages are generally classified into pro-inflammatory (M1) or anti-inflammatory (M2) subsets that play distinct roles in the initiation and resolution of inflammation. Therefore, monocyte-macrophage differentiation should be tightly controlled to maintain lung integrity. In this study, we determined the effect of α-defensins on monocyte-macrophage differentiation and identified the molecular mechanism of this effect. The results of this study demonstrate that 2.5 μM of α-defensins inhibit the phosphorylation of ERK1/2 and STAT3 and suppress the expression of M2 macrophage markers, CD163 and CD206. In addition, a scratch assay shows that the high concentration of α-defensins inhibits cell movement by ~ 50%, and the phagocytosis assay using flow cytometry shows that α-defensins significantly reduce the bacterial phagocytosis rate of monocyte-derived macrophages (MDMs). To examine whether exogenous AAT is able to alleviate the inhibitory effect of α-defensins on macrophage function, we incubated MDMs with AAT prior to α-defensin treatment and demonstrate that AAT improves the migratory ability and phagocytic ability of MDMs compared with MDMs incubated only with α-defensins. Taken together, this study suggests that a high concentration of α-defensins inhibits the activation of ERK/STAT3 signaling, negatively regulates the expression of M2 macrophage markers, and impairs innate immune function of macrophages.

The destruction of mucosal barriers, epithelial remodeling, and impaired mucociliary clearance: possible pathogenic mechanisms of Pseudomonas aeruginosa and Staphylococcus aureus in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a pathological condition characterized by persistent inflammation in the upper respiratory tract and paranasal sinuses. The epithelium serves as the first line of defense against potential threats and protects the nasal mucosa. The fundamental mechanical barrier is formed by the cell-cell contact and mucociliary clearance (MCC) systems. The physical-mechanical barrier is comprised of many cellular structures, including adhesion junctions and tight junctions (TJs). To this end, different factors, such as the dysfunction of MCC, destruction of epithelial barriers, and tissue remodeling, are related to the onset and development of CRS. Recently published studies reported the critical role of different microorganisms, such as Staphylococcus aureus and Pseudomonas aeruginosa, in the induction of the mentioned factors. Bacteria could result in diminished ciliary stimulation capacity, and enhance the chance of CRS by reducing basal ciliary beat frequency. Additionally, bacterial exoproteins have been demonstrated to disrupt the epithelial barrier and induce downregulation of transmembrane proteins such as occludin, claudin, and tricellulin. Moreover, bacteria exert an influence on TJ proteins, leading to an increase in the permeability of polarized epithelial cells. Noteworthy, it is evident that the activation of TLR2 by staphylococcal enterotoxin can potentially undermine the structural integrity of TJs and the epithelial barrier through the induction of pro-inflammatory cytokines. The purpose of this article is an attempt to investigate the possible role of the most important microorganisms associated with CRS and their pathogenic mechanisms against mucosal surfaces and epithelial barriers in the paranasal sinuses. Video Abstract.

Pharmacological Modulation of Host Immunity with Hen Egg White Lysozyme (HEWL)-A Review

In the 100 years since its discovery, lysozyme has become an important molecule, both as model for studies in different fields and as a candidate for the therapy of various pathological conditions. Of the dozens of known lysozymes, in this review we focus on one in particular, lysozyme extracted from hen egg white (HEWL), and its interaction with the immune system when it is administered orally. Experimental data show that there is an axis that directs immune system activation from GALT (gut-associated lymphoid tissue) and the intestinal lymphocyte clusters. Although a contribution of peptidoglycans from digestion of the bacterial cell wall in the intestinal lumen cannot be excluded, immune stimulation is not dependent on the enzymatic activity of HEWL. The immune responses suggest that HEWL is able to recover from immunodepression caused by tumor growth or immunosuppressants, and that it also improves the success of chemotherapy. The positive results obtained in a small Phase 2 study in patients, the ease of oral administration of this protein, and the absence of adverse effects suggest that HEWL may play an important role in all diseases where the immune system is weakened or where its enhancement plays a critical role in the resolution of the pathology.

Novel Peptides with Dual Properties for Treating Pseudomonas aeruginosa Keratitis: Antibacterial and Corneal Wound Healing

The corneal epithelium is a layer in the anterior part of eye that contributes to light refraction onto the retina and to the ocular immune defense. Although an intact corneal epithelium is an excellent barrier against microbial pathogens and injuries, corneal abrasions can lead to devastating eye infections. Among them, Pseudomonas aeruginosa-associated keratitis often results in severe deterioration of the corneal tissue and even blindness. Hence, the discovery of new drugs able not only to eradicate ocular infections, which are often resistant to antibiotics, but also to elicit corneal wound repair is highly demanded. Recently, we demonstrated the potent antipseudomonal activity of two peptides, Esc(1-21) and its diastereomer Esc(1-21)-1c. In this study, by means of a mouse model of P. aeruginosa keratitis and an in vivo corneal debridement wound, we discovered the efficacy of these peptides, particularly Esc(1-21)-1c, to cure keratitis and to promote corneal wound healing. This latter property was also supported by in vitro cell scratch and ELISA assays. Overall, the current study highlights Esc peptides as novel ophthalmic agents for treating corneal infection and injury, being able to display a dual function, antimicrobial and wound healing, rarely identified in a single peptide at the same micromolar concentration range.

Structure-activity relationships of antibacterial peptides

Antimicrobial peptides play a crucial role in innate immunity, whose components are mainly peptide-based molecules with antibacterial properties. Indeed, the exploration of the immune system over the past 40 years has revealed a number of natural peptides playing a pivotal role in the defence mechanisms of vertebrates and invertebrates, including amphibians, insects, and mammalians. This review provides a discussion regarding the antibacterial mechanisms of peptide-based agents and their structure-activity relationships (SARs) with the aim of describing a topic that is not yet fully explored. Some growing evidence suggests that innate immunity should be strongly considered for the development of novel antibiotic peptide-based libraries. Also, due to the constantly rising concern of antibiotic resistance, the development of new antibiotic drugs is becoming a priority of global importance. Hence, the study and the understanding of defence phenomena occurring in the immune system may inspire the development of novel antibiotic compound libraries and set the stage to overcome drug-resistant pathogens. Here, we provide an overview of the importance of peptide-based antibacterial sources, focusing on accurately selected molecular structures, their SARs including recently introduced modifications, their latest biotechnology applications, and their potential against multi-drug resistant pathogens. Last, we provide cues to describe how antibacterial peptides show a better scope of action selectivity than several anti-infective agents, which are characterized by non-selective activities and non-targeted actions toward pathogens.

Preventing Respiratory Viral Diseases with Antimicrobial Peptide Master Regulators in the Lung Airway Habitat

The vast surface area of the respiratory system acts as an initial site of contact for microbes and foreign particles. The whole respiratory epithelium is covered with a thin layer of the airway and alveolar secretions. Respiratory secretions contain host defense peptides (HDPs), such as defensins and cathelicidins, which are the best-studied antimicrobial components expressed in the respiratory tract. HDPs have an important role in the human body's initial line of defense against pathogenic microbes. Epithelial and immunological cells produce HDPs in the surface fluids of the lungs, which act as endogenous antibiotics in the respiratory tract. The production and action of these antimicrobial peptides (AMPs) are critical in the host's defense against respiratory infections. In this study, we have described all the HDPs secreted in the respiratory tract as well as how their expression is regulated during respiratory disorders. We focused on the transcriptional expression and regulation mechanisms of respiratory tract HDPs. Understanding how HDPs are controlled throughout infections might provide an alternative to relying on the host's innate immunity to combat respiratory viral infections.

Endo-lysosomal protein concentrations in CSF from patients with frontotemporal dementia caused by CHMP2B mutation

Introduction

Increasing evidence implicates proteostatic dysfunction as an early event in the development of frontotemporal dementia (FTD). This study aimed to explore potential cerebrospinal fluid (CSF) biomarkers associated with the proteolytic systems in genetic FTD caused by CHMP2B mutation.

Methods

Combining solid-phase extraction and parallel reaction monitoring mass spectrometry, a panel of 47 peptides derived from 20 proteins was analyzed in CSF from 31 members of the Danish CHMP2B-FTD family.

Results

Compared with family controls, mutation carriers had significantly higher levels of complement C9, lysozyme and transcobalamin II, and lower levels of ubiquitin, cathepsin B, and amyloid precursor protein.

Discussion

Lower CSF ubiquitin concentrations in CHMP2B mutation carriers indicate that ubiquitin levels relate to the specific disease pathology, rather than all-cause neurodegeneration. Increased lysozyme and complement proteins may indicate innate immune activation. Altered levels of amyloid precursor protein and cathepsins have previously been associated with impaired lysosomal proteolysis in FTD.

Highlights

CSF markers of proteostasis were explored in CHMP2B-mediated frontotemporal dementia (FTD).31 members of the Danish CHMP2B-FTD family were included.We used solid-phase extraction and parallel reaction monitoring mass spectrometry.Six protein levels were significantly altered in CHMP2B-FTD compared with controls.Lower CSF ubiquitin levels in patients suggest association with disease mechanisms.

Recent Insights Into the Prognostic and Therapeutic Applications of Lysozymes

Lysozymes are naturally occurring enzymes present in a variety of biological organisms, such as bacteria, fungi, and animal bodily secretions and tissues. It is also the main ingredient of many ethnomedicines. It is well known that lysozymes and lysozyme-like enzymes can be used as anti-bacterial agents by degrading bacterial cell wall peptidoglycan that leads to cell death, and can also inhibit fungi, yeasts, and viruses. In addition to its direct antimicrobial activity, lysozyme is also an important component of the innate immune system in most mammals. Increasing evidence has shown the immune-modulatory effects of lysozymes against infection and inflammation. More recently, studies have revealed the anti-cancer activities of lysozyme in multiple types of tumors, potentially through its immune-modulatory activities. In this review, we summarized the major functions and underlying mechanisms of lysozymes derived from animal and plant sources. We highlighted the therapeutic applications and recent advances of lysozymes in cancers, hypertension, and viral diseases, aiming toseeking alternative therapies for standard medical treatment bypassing side effects. We also evaluated the role of lysozyme as a promising cancer marker for prognosis to indicate the outcomes recurrence for patients.

Gastric Microenvironment-A Partnership between Innate Immunity and Gastric Microbiota Tricks Helicobacter pylori

Helicobacter pylori (H. pylori) carcinogenicity depends on three major factors: bacterial virulence constituents, environmental factors and host's genetic susceptibility. The relationship between microenvironmental factors and H. pylori virulence factors are incontestable. H. pylori infection has a major impact on both gastric and colonic microbiota. The presence of non-H. pylori bacteria within the gastric ecosystem is particularly important since they might persistently act as an antigenic stimulus or establish a partnership with H. pylori in order to augment the subsequent inflammatory responses. The gastric ecosystem, i.e., microbiota composition in children with H. pylori infection is dominated by Streptoccocus, Neisseria, Rothia and Staphylococcus. The impairment of this ecosystem enhances growth and invasion of different pathogenic bacteria, further impairing the balance between the immune system and mucosal barrier. Moreover, altered microbiota due to H. pylori infection is involved in increasing the gastric T regulatory cells response in children. Since gastric homeostasis is defined by the partnership between commensal bacteria and host's immune system, this review is focused on how pathogen recognition through toll-like receptors (TLRs-an essential class of pathogen recognition receptors-PRRs) on the surface of macrophages and dendritic cells impact the immune response in the setting of H. pylori infection. Further studies are required for delineate precise role of bacterial community features and of immune system components.

Lipid-Coated MCM-41 Mesoporous Silica Nanoparticles Loaded with Berberine Improved Inhibition of Acetylcholine Esterase and Amyloid Formation

Selective permeability of the blood-brain barrier limits effective treatment of neurodegenerative disorders. In the present study, brain-targeted lipid-coated mesoporous silica nanoparticles (MSNs) containing berberine (BBR) were synthesized for the effective treatment of Alzheimer's disease (AD). The study involved synthesis of Mobil Composition of Matter-41 (MCM-41) mesoporous silica nanoparticles (MSNs), BBR loading, and lipid coating of MSNs (MSNs-BBR-L) and in vitro and in vivo characterization of MSNs-BBR-L. The liposomes (for lipid coating) were prepared by the thin-film hydration method. Transmission electron microscopy (TEM) images indicated 5 nm thickness of the lipid coating. Dynamic light scattering (DLS) and TEM results confirmed that the size of synthesized MSNs-BBR-L was in the range of 80-100 nm. The X-ray diffraction (XRD) pattern demonstrated retention of the ordered structure of BBR after encapsulation and lipid coating. Fourier transform infrared (FTIR) spectrum confirmed the formation of a lipid coat over the MSN particles. MSNs-BBR-L displayed significantly (p < 0.05) higher acetylcholine esterase (AChE) inhibitory activity. The study confirmed significant (p < 0.05) amyloid fibrillation inhibition and decreased the malondialdehyde (MDA) level by MSNs-BBR-L. Pure BBR- and MSNs-BBR-L-treated AD animals showed a significant decrease in the BACE-1 level compared to scopolamine-intoxicated mice. Eight times higher area under the curve for MSNs-BBR-L (2400 ± 27.44 ng h/mL) was recorded compared to the pure BBR (295.5 ± 0.755 ng h/mL). Overall, these results highlight the utility of MSNs-BBR-L as promising drug delivery vehicles for brain delivery of drugs.

Non-Reflex Defense Mechanisms of Upper Airway Mucosa: Possible Clinical Application

The sinonasal mucosa has an essential role in defense mechanisms of the upper respiratory tract. The innate immune system presents the primary defense against noxious microorganisms followed by induction of the adaptive immune mechanisms as a consequence of the presence of pathogens. This well-known activation of adaptive immune system in response to presence of the antigen on mucosal surfaces is now broadly applicated in vaccinology research. Prevention of infectious diseases belongs to substantial challenges in maintaining the population health. Non-invasive, easily applicable mucosal vaccination purposes various research opportunities that could be usable in daily practice. However, the existence of multiple limitations such as rapid clearance of vaccine from nasal mucosa by means of mucociliary transport represents a great challenge in development of safe and efficient vaccines. Here we give an updated view on nasal functions with focus on nasal mucosal immunity and its potential application in vaccination in nearly future.

Effects of synbiotics on the gut microbiota, blood and rearing parameters of chickens

The aim of the study was to assess the safety of three newly developed synbiotic preparations in feeding chickens. The study was carried out on 84 Specific Pathogen Free chickens, between 1st and 21st day of their life. Animals were divided into four groups fed ad libitum: three with an addition of synbiotics A, B or C and a control group (feed with no additives). Synbiotics contained Lactobacillus, Saccharomyces cerevisiae and inulin (prebiotic). Rearing parameters were determined taking into account undesirable clinical and sectional symptoms, daily mortality and body weight of birds. In addition, chicken blood parameters were determined based on haematological, biochemical and serological tests. Samples of the intestinal content and of the excreta constituted a material for research aimed at determination of the dominant chicken gut microbiota. On the basis of the conducted investigation, it was found that synbiotics met the basic requirements for this type of formulas regarding the safety of use and had a positive effect on the health of chickens. Therefore, further research is being carried out on the application of these formulas in large-scale production. The next step of the research will be the comparison of effects of synbiotics with commercial probiotics.

Phagocytosis: Our Current Understanding of a Universal Biological Process

Phagocytosis is a cellular process for ingesting and eliminating particles larger than 0.5 μm in diameter, including microorganisms, foreign substances, and apoptotic cells. Phagocytosis is found in many types of cells and it is, in consequence an essential process for tissue homeostasis. However, only specialized cells termed professional phagocytes accomplish phagocytosis with high efficiency. Macrophages, neutrophils, monocytes, dendritic cells, and osteoclasts are among these dedicated cells. These professional phagocytes express several phagocytic receptors that activate signaling pathways resulting in phagocytosis. The process of phagocytosis involves several phases: i) detection of the particle to be ingested, ii) activation of the internalization process, iii) formation of a specialized vacuole called phagosome, and iv) maturation of the phagosome to transform it into a phagolysosome. In this review, we present a general view of our current understanding on cells, phagocytic receptors and phases involved in phagocytosis.

Effects of Carbohydrate Mouth Rinsing on Salivary Lysozyme, Mood States and Running Performance Among Recreational Runners

Introduction

Carbohydrate (CHO) mouth rinsing can enhance sports performance through a central action mediated by receptors in the mouth. This study examined the effect of a CHO mouth rinse on salivary lysozyme concentrations, mood states and running performances.

Methods

Ten males recreational runners were randomised to three running trials with a 1 week recovery period between the trials. Each trial involved running at 75% maximum heart rate (HRmax) for 1 h, followed by a 15 min time trial. The participants used a CHO mouth rinse, placebo (PLA) solution or control (CON, no solution) every 15 min during the exercise. Heart rate (HR), rating of perceived exertion (RPE) and mood states were recorded pre-, during and post-exercise. Saliva samples were collected pre-, post- and 1 h post-exercise.

Results

There was no significant interaction and time effect (P > 0.05) on the salivary lysozyme concentration and running performance, but it was significant (P < 0.05) for HR and RPE (increase in all trials). However, there was no significant difference (P > 0.05) in salivary lysozyme concentrations, running performances, HR values or RPE between the trials. Mood states were not significantly different (P > 0.05) between the trials, but one of the mood sub-scales showed a significant (P < 0.001) time effect (increase fatigue in all trials).

Conclusion

CHO mouth rinsing did not affect physiological parameters, salivary lysozyme concentrations, mood states or running performance among recreational runners.

The Role of Neutrophils in the Immune System: An Overview

Neutrophils, also known as polymorphonuclear neutrophils (PMNs), have long been considered as the short-lived, nonspecific white cells that form pus-and also happen to kill invading microbes. Indeed, neutrophils were often neglected (and largely not considered) as immune cells. This historic view of neutrophils has changed considerably over the past several decades, and we now know that in addition to playing the predominant role in the clearance of bacteria and fungi, they have a major role in shaping the host response to infection and immune system homeostasis. The change in our view of the role of neutrophils in the immune system has been due in large part to the study of these cells in vitro. Such work has been made possible by new and/or improved methods and approaches used to investigate neutrophils. These methods are the focus of this volume.

Endo-lysosomal proteins and ubiquitin CSF concentrations in Alzheimer's and Parkinson's disease

BACKGROUND

Increasing evidence implicates dysfunctional proteostasis and the involvement of the autophagic and endo-lysosomal system and the ubiquitin-proteasome system in neurodegenerative diseases. In Alzheimer's disease (AD), there is an accumulation of autophagic vacuoles within the neurons. In Parkinson's disease (PD), susceptibility has been linked to genes encoding proteins involved in autophagy and lysosomal function, as well as mutations causing lysosomal disorders. Furthermore, both diseases are characterized by the accumulation of protein aggregates.

METHODS

Proteins associated with endocytosis, lysosomal function, and the ubiquitin-proteasome system were identified in the cerebrospinal fluid (CSF) and targeted by combining solid-phase extraction and parallel reaction monitoring mass spectrometry. In total, 50 peptides from 18 proteins were quantified in three cross-sectional cohorts including AD (N = 61), PD (N = 21), prodromal AD (N = 10), stable mild cognitive impairment (N = 15), and controls (N = 68).

RESULTS

A pilot study, including subjects selected based on their AD CSF core biomarker concentrations, showed increased concentrations of several targeted proteins in subjects with core biomarker levels indicating AD pathology compared to controls. Next, in a clinically characterized cohort, lower concentrations in CSF of proteins in PD were found compared to subjects with prodromal AD. Further investigation in an additional clinical study again revealed lower concentrations in CSF of proteins in PD compared to controls and AD.

CONCLUSION

In summary, significantly different peptide CSF concentrations were identified from proteins AP2B1, C9, CTSB, CTSF, GM2A, LAMP1, LAMP2, TCN2, and ubiquitin. Proteins found to have altered concentrations in more than one study were AP2B1, CTSB, CTSF, GM2A, LAMP2, and ubiquitin. Interestingly, given the genetic implication of lysosomal function in PD, we did identify the CSF concentrations of CTSB, CTSF, GM2A, and LAMP2 to be altered. However, we also found differences in proteins associated with endocytosis (AP2B1) and the ubiquitin-proteasome system (ubiquitin). No difference in any peptide CSF concentration was found in clinically characterized subjects with AD compared to controls. In conclusion, CSF analyses of subjects with PD suggest a general lysosomal dysfunction, which resonates well with recent genetic findings, while such changes are minor or absent in AD.

Male reproductive tract antimicrobial expression in the extremes of ages of rats

Alterations in the global gene expression profile are considered to contribute to the various physiological and pathological changes during the course of ageing. Genes that code for the molecular components of the innate system are alter markedly as ageing occurs; and this may define the susceptibility of very young and very old individuals to reproductive tract infections. The expression pattern of genes that code for beta-defensins (effectors of innate immune response) in male reproductive tract tissues of different stages of ageing is not yet reported. Further, the induction of beta-defensins during endotoxin challenge and whether epigenetic modulators can influence the expression of these genes in different stages of ageing are not reported. We analyzed the basal mRNA levels of beta-defensins and defensin-like proteins (Sperm Associated Antigen 11 (SPAG11) family members), their induction during endotoxin challenge and modulation by epigenetic modifiers (Trichostatin A and Azacytidine) in the caput, cauda, testis, prostate and seminal vesicle of rats that represent early stage to late stages of life (20 day to 730 day old). We observed differential basal gene expression pattern in the male reproductive tract tissues and the induction by LPS was not consistent neither among the age groups not the tissues analyzed. Trichostatin A and Azacytidine also influenced antimicrobial gene expression and the pattern was not consistent in different tissues obtained from different age groups. Results of this study demonstrate that antimicrobial gene expression varies to a great extent during ageing and is strongly influenced by endotoxins and epigenetic modulators.

A Novel View of Human Helicobacter pylori Infections: Interplay between Microbiota and Beta-Defensins

The gut microbiota is significantly involved in the preservation of the immune system of the host, protecting it against the pathogenic bacteria of the stomach. The correlation between gut microbiota and the host response supports human gastric homeostasis. Gut microbes may be shifted in Helicobacter pylori (Hp)-infected individuals to advance gastric inflammation and distinguished diseases. Particularly interesting is the establishment of cooperation between gut microbiota and antimicrobial peptides (AMPs) of the host in the gastrointestinal tract. AMPs have great importance in the innate immune reactions to Hp and participate in conservative co-evolution with an intricate microbiome. β-Defensins, a class of short, cationic, arginine-rich proteins belonging to the AMP group, are produced by epithelial and immunological cells. Their expression is enhanced during Hp infection. In this review, we discuss the impact of the gut microbiome on the host response, with particular regard to β-defensins in Hp-associated infections. In microbial infections, mostly in precancerous lesions induced by Hp infection, these modifications could lead to different outcomes.

Lysozyme as the anti-proliferative agent to block the interaction between S100A6 and the RAGE V domain

In this report, using NMR and molecular modeling, we have studied the structure of lysozyme-S100A6 complex and the influence of tranilast [N-(3, 4-dimethoxycinnamoyl) anthranilic acid], an antiallergic drug which binds to lysozyme, on lysozyme-S100A6 and S100A6-RAGE complex formation and, finally, on cell proliferation. We have found that tranilast may block the S100A6-lysozyme interaction and enhance binding of S100A6 to RAGE. Using WST1 assay, we have found that lysozyme, most probably by blocking the interaction between S100A6 and RAGE, inhibits cell proliferation while tranilast may reverse this effect by binding to lysozyme. In conclusion, studies presented in this work, describing the protein-protein/-drug interactions, are of great importance for designing new therapies to treat diseases associated with cell proliferation such as cancers.

Rapid Detection and Identification of Antimicrobial Peptide Fingerprints of Nasal Fluid by Mesoporous Silica Particles and MALDI-TOF/TOF Mass Spectrometry: From the Analytical Approach to the Diagnostic Applicability in Precision Medicine

Background: Antimicrobial peptides (AMP) play a pivotal role in innate host defense and in immune response. The delineation of new MS-based profiling tools, which are able to produce panels of AMP of the nasal fluid (NF), may be attractive for the discovery of new potential diagnostic markers of respiratory disorders. Methods: Swabs collected NF from healthy patients and from patients with respiratory disorders. We used a fast procedure based on mesoporous silica particles (MPS) to enrich NF in its AMP component in combination with MALDI-TOF/TOF MS as a key tool for rapidly analyzing clinical samples. Results: Reproducible MS peptide fingerprints were generated for each subject and several AMP were detected including (Human Neutrophil Peptides) HNPs, Statherin, Thymosin-β4, Peptide P-D, II-2, β-MSP, SLPI, Lysozyme-C, and their proteo-forms. In particular, Statherin, Thymosin-β4, and Peptide P-D were accurately identified by direct MS/MS sequencing. Examples of applicability of this tool are shown. AMP fingerprints were obtained before and after a nasal polypectomy as well as before and post-treatment with azelastine/fluticasone in one case of allergic rhinitis. Conclusion: The potential of our platform to be implemented by new mesoporous materials for capturing a wider picture of AMP might offer an amazing opportunity for diagnostic clinical studies on individual and population scales.

Gut Microbiota as a Modulator of Paneth Cells During Parenteral Nutrition in Mice

BACKGROUND

Parenteral nutrition (PN) leads to decreased production of Paneth cell-derived antimicrobial peptides and is accompanied by dysbiosis of the gut. The role of gut microbiota in regulating Paneth cell function during PN is unknown.

METHODS

Male C57BL/6 mice received either an antibiotic cocktail (Abx) or nothing (Normal) in their drinking water for 2 weeks before being fed either standard laboratory chow (Abx-Chow and Normal-Chow) or a continuous infusion of PN solution (Abx-PN and Normal-PN) for 7 days. In a separate experiment, the intestinal contents of mice having received 7 days of Chow or PN were transferred by gavage to germ-free (GF) mice.

RESULTS

Antibiotic treatment decreased the protein levels of lysozyme and RegIIIγ and the mRNA level of α-defensin 5, with no further effect by PN compared with chow. However, these measurements were higher in Abx-PN mice than in Normal-PN mice. When compared with Chow→GF, PN→GF mice demonstrated lower body weight, shorter intestinal length, severe atrophy of the ileum villus, and lower levels of lysozyme and RegIIIγ protein and α-defensin 5 mRNA. Interleukin (IL)-22 and IL-17 mRNA levels declined in the ileum. Principal component analysis revealed major differences between the metabolite compositions of the Chow and PN, as well as the Chow→GF and PN→GF groups that appears to indicate aberrant tryptophan metabolism.

CONCLUSIONS

Gut microbiota plays a vital role in PN-related Paneth cell dysfunction. Dysbiosis during PN might alter the production of microbial metabolites, thereby influencing the production of Paneth cell-derived antimicrobial peptides.

Aryl hydrocarbon receptor/IL-22/Stat3 signaling pathway is involved in the modulation of intestinal mucosa antimicrobial molecules by commensal microbiota in mice

Compelling evidence demonstrates the crucial role of the commensal microbiota in host physiology and the detrimental effects of its perturbations following antibiotic treatment. However, the effects of commensal microbiota on intestinal mucosa antimicrobial molecules have not been elucidated systematically. Here, we investigate the impacts of antibiotic-induced depletion and subsequent restoration of the intestinal microbiota on the murine antimicrobial molecules in intestinal mucosa. Our results demonstrate that depletion of commensal microbiota leads to intestinal mucosa atrophy and reduction of antimicrobial molecules, including lysozyme, regenerating islet-derived protein 3 gamma (RegIIIγ), and cryptdin 5 mRNA, whereas subsequent reconstitution of intestinal microbiota by fecal microbiota transplantation (FMT) rescues mucosa morphology and antimicrobials. Importantly, our study shows that down-regulation of aryl hydrocarbon receptor (AhR), interleukin-22 (IL-22), and phosphorylated Stat3 (p-Stat3) is associated with decreased antimicrobials, which might mediate the antibiotic-associated intestinal mucosa injury. Last, exogenous activation of the AhR/IL-22/Stat3 signaling pathway with the AhR agonist 6-formylindolo(3,2-b)carbazole (Ficz) rescued antimicrobial molecule levels markedly after antibiotic treatment to levels similar to those following reconstitution of intestinal microbiota by FMT. Together, our results demonstrate that the AhR/IL-22/Stat3 signaling pathway is involved in the modulation of intestinal mucosa antimicrobial molecules by commensal microbiota and suggest this pathway as a promising target in the treatment of antibiotic-associated gut barrier damage.

Pulmonary Regnase-1 orchestrates the interplay of epithelium and adaptive immune systems to protect against pneumonia

Inhaled pathogens including Pseudomonas aeruginosa initially encounter airway epithelial cells (AECs), which are poised to evoke cell-intrinsic innate defense, affecting second tier of hematopoietic cell-mediated immune reaction. However, it is largely unknown how pulmonary immune responses mediated by a variety of immune cells are coordinated. Here we show that Regnase-1, an endoribonuclease expressed in AECs and immune cells, plays an essential role in coordinating innate responses and adaptive immunity against P. aeruginosa infection. Intratracheal treatment of mice with heat-killed P. aeruginosa resulted in prolonged disappearance of Regnase-1 consistent with sustained expression of Regnase-1 target inflammatory genes, whereas the transcription factor NF-κB was only transiently activated. AEC-specific deletion of Regnase-1 not only augmented innate defenses against P. aeruginosa but also enhanced secretion of Pseudomonas-specific IgA and Th17 accumulation in the lung, culminating in conferring significant resistance against P. aeruginosa re-infection in vivo. Although Regnase-1 directly controls distinct sets of genes in each of AECs and T cells, degradation of Regnase-1 in both cell types is beneficial for maximizing acquired immune responses. Collectively, these results demonstrate that Regnase-1 orchestrates AEC-mediated and immune cell-mediated host defense against pulmonary bacterial infection.

Control of Phagocytosis by Microbial Pathogens

Phagocytosis is a fundamental process of cells to capture and ingest foreign particles. Small unicellular organisms such as free-living amoeba use this process to acquire food. In pluricellular organisms, phagocytosis is a universal phenomenon that all cells are able to perform (including epithelial, endothelial, fibroblasts, etc.), but some specialized cells (such as neutrophils and macrophages) perform this very efficiently and were therefore named professional phagocytes by Rabinovitch. Cells use phagocytosis to capture and clear all particles larger than 0.5 µm, including pathogenic microorganisms and cellular debris. Phagocytosis involves a series of steps from recognition of the target particle, ingestion of it in a phagosome (phagocytic vacuole), maturation of this phagosome into a phagolysosome, to the final destruction of the ingested particle in the robust antimicrobial environment of the phagolysosome. For the most part, phagocytosis is an efficient process that eliminates invading pathogens and helps maintaining homeostasis. However, several pathogens have also evolved different strategies to prevent phagocytosis from proceeding in a normal way. These pathogens have a clear advantage to perpetuate the infection and continue their replication. Here, we present an overview of the phagocytic process with emphasis on the antimicrobial elements professional phagocytes use. We also summarize the current knowledge on the microbial strategies different pathogens use to prevent phagocytosis either at the level of ingestion, phagosome formation, and maturation, and even complete escape from phagosomes.

N-3 polyunsaturated fatty acid-enriched lipid emulsion improves Paneth cell function via the IL-22/Stat3 pathway in a mouse model of total parenteral nutrition

Total parenteral nutrition (TPN) is a life-saving therapy for patients with gastrointestinal dysfunction or failure. Long-term TPN impairs gut barrier function and contributes to infections and poor clinical outcomes. However, the underlying mechanisms of TPN-related gut barrier damage have not been fully elucidated, and effective measures are still rare. Here, we compared the effects of a predominantly n-6 polyunsaturated fatty acids emulsion (PUFAs; Intralipid) and a lipid emulsion containing n-3 PUFAs (Intralipid plus Omegaven) on antimicrobial peptides produced by Paneth cells. Our results show for the first time that n-3 PUFAs markedly ameliorated intestine atrophy, and increased protein levels of lysozyme, RegIIIγ, and α-cryptdin 5, and their mRNA expression, compared to the n-6 PUFAs emulsion. Importantly, our study reveals that downregulation of IL-22 and phosphorylated Stat3 (p-Stat3) is associated with Paneth cell dysfunction, which may mediate TPN-related gut barrier damage. Lastly, n-3 PUFAs upregulated levels of IL-22 and increased the p-Stat3/Stat3 ratio in ileal tissue, suggesting that n-3 PUFAs improve Paneth cell function through activation of the IL-22/Stat3 pathway. Therefore, our study provides a cogent explanation for the beneficial effects of n-3 PUFAs, and indicates the IL-22/Stat3 pathway as a promising target in the treatment of TPN-related gut barrier damage.

Ultrastructure and immunohistochemical characterization of proteins concerned with the secretory machinery in goat ceruminous glands

The expression of soluble N-ethylmaleimide sensitive fusion attachment protein receptor (SNARE) proteins in apocrine glands has not been fully elucidated. In addition to performing ultrastructural observation of the ceruminous glands in goats, our study focuses on the demonstration of β-defensins, SNARE proteins and Rab3D in these glands with the use of immunohistochemical methods. The secretory cells were equipped with two types of vesicles, Golgi apparatus and abundant rough endoplasmic reticulum (ER). Additionally, in some of them, the characteristic concentric structures composed of rough ER were observed in their circum- and infranuclear parts. The expression of phosphorylated inositol requiring enzyme 1rrwas also detected. These findings may indicate their ability to produce numerous secretory proteins and the maintenance of homeostasis in the glandular cells. Furthermore, β-defensins were demonstrated as products of the ceruminous glands. The present investigation also revealed the presence of SNARE proteins and Rab3D. It is suggested that these proteins are concerned with the secretory machinery of this gland type.

Beneficial effects of increased lysozyme levels in Alzheimer's disease modelled in Drosophila melanogaster

Genetic polymorphisms of immune genes that associate with higher risk to develop Alzheimer's disease (AD) have led to an increased research interest on the involvement of the immune system in AD pathogenesis. A link between amyloid pathology and immune gene expression was suggested in a genome‐wide gene expression study of transgenic amyloid mouse models. In this study, the gene expression of lysozyme, a major player in the innate immune system, was found to be increased in a comparable pattern as the amyloid pathology developed in transgenic mouse models of AD. A similar pattern was seen at protein levels of lysozyme in human AD brain and CSF, but this lysozyme pattern was not seen in a tau transgenic mouse model. Lysozyme was demonstrated to be beneficial for different Drosophila melanogaster models of AD. In flies that expressed Aβ_1‐42 or AβPP together with BACE1 in the eyes, the rough eye phenotype indicative of toxicity was completely rescued by coexpression of lysozyme. In Drosophila flies bearing the Aβ_1‐42 variant with the Arctic gene mutation, lysozyme increased the fly survival and decreased locomotor dysfunction dose dependently. An interaction between lysozyme and Aβ_1‐42 in the Drosophila eye was discovered. We propose that the increased levels of lysozyme, seen in mouse models of AD and in human AD cases, were triggered by Aβ_1‐42 and caused a beneficial effect by binding of lysozyme to toxic species of Aβ_1‐42, which prevented these from exerting their toxic effects. These results emphasize the possibility of lysozyme as biomarker and therapeutic target for AD.

Arsenic alters transcriptional responses to Pseudomonas aeruginosa infection and decreases antimicrobial defense of human airway epithelial cells

Arsenic contamination of drinking water and food threatens the health of hundreds of millions of people worldwide by increasing the risk of numerous diseases. Arsenic exposure has been associated with infectious lung disease in epidemiological studies, but it is not yet understood how ingestion of low levels of arsenic increases susceptibility to bacterial infection. Accordingly, the goal of this study was to examine the effect of arsenic on gene expression in primary human bronchial epithelial (HBE) cells and to determine if arsenic altered epithelial cell responses to Pseudomonas aeruginosa, an opportunistic pathogen. Bronchial epithelial cells line the airway surface, providing a physical barrier and serving critical roles in antimicrobial defense and signaling to professional immune cells. We used RNA-seq to define the transcriptional response of HBE cells to Pseudomonas aeruginosa, and investigated how arsenic affected HBE gene networks in the presence and absence of the bacterial challenge. Environmentally relevant levels of arsenic significantly changed the expression of genes involved in cellular redox homeostasis and host defense to bacterial infection, and decreased genes that code for secreted antimicrobial factors such as lysozyme. Using pathway analysis, we identified Sox4 and Nrf2-regulated gene networks that are predicted to mediate the arsenic-induced decrease in lysozyme secretion. In addition, we demonstrated that arsenic decreased lysozyme in the airway surface liquid, resulting in reduced lysis of Microccocus luteus. Thus, arsenic alters the expression of genes and proteins in innate host defense pathways, thereby decreasing the ability of the lung epithelium to fight bacterial infection.

HSP70 is associated with the severity of inflammation in chronic rhinosinusitis

BACKGROUND

Nasal secretions include cytokines and inflammatory mediators that are involved in the pathogenesis of upper airway inflammation.

OBJECTIVE

We tried to find unknown biomolecules that are involved in the pathogenesis of chronic rhinosinusitis (CRS).

METHODS

We collected nasal mucosal secretions from patients who were diagnosed as having CRS and who underwent endoscopic sinus surgery. A total of 63 patients who underwent nasal secretion collection were reviewed. Enzyme-linked immunosorbent assay was performed by using nasal lavage samples to evaluate which biomolecules were associated with the severity of inflammation based on the Lund-Mackay score. By using human nasal epithelial cells, we performed Western blot, real-time polymerase chain reaction, and enzyme-linked immunosorbent assay to evaluate the secretory mechanism of heat shock protein (HSP) 70.

RESULTS

We found that the level of interleukin 8 and HSP70 were significantly associated with the Lund-Mackay score and interleukin 17C, C-X-C motif chemokine 10, and HSP27 were not significantly associated. HSP70 was also significantly associated with the surgical outcome of the enrolled patients. Furthermore, we found that exposure to hypoxia and treatment of lipoteichoic acid induced the secretion of HSP70 but that lipopolysaccharide did not induce the secretion of HSP70 in human nasal epithelial cells.

CONCLUSION

Our findings indicated that HSP70 might play a role in the pathogenesis of CRS and the possibility of HSP70 as a biomolecule that represents the severity of CRS.

Mucosal Ecological Network of Epithelium and Immune Cells for Gut Homeostasis and Tissue Healing

The intestinal epithelial barrier includes columnar epithelial, Paneth, goblet, enteroendocrine, and tuft cells as well as other cell populations, all of which contribute properties essential for gastrointestinal homeostasis. The intestinal mucosa is covered by mucin, which contains antimicrobial peptides and secretory IgA and prevents luminal bacteria, fungi, and viruses from stimulating intestinal immune responses. Conversely, the transport of luminal microorganisms-mediated by M, dendritic, and goblet cells-into intestinal tissues facilitates the harmonization of active and quiescent mucosal immune responses. The bacterial population within gut-associated lymphoid tissues creates the intratissue cohabitations for harmonized mucosal immunity. Intermolecular and intercellular communication among epithelial, immune, and mesenchymal cells creates an environment conducive for epithelial regeneration and mucosal healing. This review summarizes the so-called intestinal mucosal ecological network-the complex but vital molecular and cellular interactions of epithelial mesenchymal cells, immune cells, and commensal microbiota that achieve intestinal homeostasis, regeneration, and healing.

Functional Characterization of a c-type Lysozyme from Indian Shrimp Fenneropenaeus indicus

Lysozyme gene from Fenneropenaeus indicus was cloned, expressed in Escherichia coli and characterized. The cDNA consists of 477 base pairs and encodes amino acid sequence of 159 residues. F. indicus lysozyme had high identity (98%) with Fenneropenaeus merguiensis and Fenneropenaeus chinensis and exhibits low to moderate identities with lysozymes of other invertebrates and vertebrates. This lysozyme is presumed to be chicken types as it possesses two catalytic and eight cysteine residues that are conserved across c-type lysozymes and a c-terminal extension, which is a characteristic of lysozymes from marine invertebrates. Further, the antimicrobial properties of the recombinant lysozyme from F. indicus were determined in comparison with recombinant hen egg white lysozyme. This exhibited high activity against a Gram-negative pathogenic bacterium Salmonella typhimurium and two fungal strains Pichia pastoris and Saccharomyces cerevisiae in turbidimetric assay. Distribution of lysozyme gene and protein in tissues of shrimps infected with white spot syndrome virus revealed that the high levels of lysozyme are correlated with low and high viral load in abdominal muscle and tail, respectively. In conclusion, lysozyme from F. indicus has a broad spectrum of antimicrobial properties, which once again emphasizes its role in shrimp innate immune response.

Proteomic analysis of egg white heparin-binding proteins: towards the identification of natural antibacterial molecules

The chicken egg resists most environmental microbes suggesting that it potentially contains efficient antimicrobial molecules. Considering that some heparin-binding proteins in mammals are antibacterial, we investigated the presence and the antimicrobial activity of heparin-binding proteins from chicken egg white. Mass spectrometry analysis of the proteins recovered after heparin-affinity chromatography, revealed 20 proteins, including known antimicrobial proteins (avidin, lysozyme, TENP, ovalbumin-related protein X and avian bêta-defensin 11). The antibacterial activity of three new egg candidates (vitelline membrane outer layer protein 1, beta-microseminoprotein-like (LOC101750704) and pleiotrophin) was demonstrated against Listeria monocytogenes and/or Salmonella enterica Enteritidis. We showed that all these molecules share the property to inhibit bacterial growth through their heparin-binding domains. However, vitelline membrane outer layer 1 has additional specific structural features that can contribute to its antimicrobial potential. Moreover, we identified potential supplementary effectors of innate immunity including mucin 5B, E-selectin ligand 1, whey acidic protein 3, peptidyl prolyl isomerase B and retinoic acid receptor responder protein 2. These data support the concept of using heparin affinity combined to mass spectrometry to obtain an overview of the various effectors of innate immunity composing biological milieus, and to identify novel antimicrobial candidates of interest in the race for alternatives to antibiotics.

Expression of Innate Immunity Genes in Epithelial Cells of Hypertrophic Adenoids with and without Pediatric Chronic Rhinosinusitis: A Preliminary Report

BACKGROUND

Adenoid hypertrophy (AH) is associated with pediatric chronic rhinosinusitis (pCRS), but its role in the inflammatory process of pCRS is unclear. It is thought that innate immunity gene expression is disrupted in the epithelium of patients with chronic rhinosinusitis (CRS), including antimicrobial peptides and pattern recognition receptors (PRRs). The aim of this preliminary study was to detect the expression of innate immunity genes in epithelial cells of hypertrophic adenoids with and without pCRS to better understand their role in pCRS.

METHODS

Nine pCRS patients and nine simple AH patients undergoing adenoidectomy were recruited for the study. Adenoidal epithelium was isolated, and real-time quantitative polymerase chain reaction (RT-qPCR) was employed to measure relative expression levels of the following messenger RNAs in hypertrophic adenoid epithelial cells of pediatric patients with and without CRS: Human β-defensin (HBD) 2 and 3, surfactant protein (SP)-A and D, toll-like receptors 1-10, nucleotide-binding oligomerization domain (NOD)-like receptors NOD 1, NOD 2, and NACHT, LRR and PYD domains-containing protein 3, retinoic acid-induced gene 1, melanoma differentiation-associated gene 5, and nuclear factor-κB (NF-κB). RT-qPCR data from two groups were analyzed by independent sample t-tests and Mann-Whitney U-tests.

RESULTS

The relative expression of SP-D in adenoidal epithelium of pCRS group was significantly lower than that in AH group (pCRS 0.73 ± 0.10 vs. AH 1.21 ± 0.15; P = 0.0173, t = 2.654). The relative expression levels of all tested PRRs and NF-κB, as well as HBD-2, HBD-3, and SP-A, showed no statistically significant differences in isolated adenoidal epithelium between pCRS group and AH group.

CONCLUSIONS

Down-regulated SP-D levels in adenoidal epithelium may contribute to the development of pCRS. PRRs, however, are unlikely to play a significant role in the inflammatory process of pCRS.

Bacterial Metabolism in the Host Environment: Pathogen Growth and Nutrient Assimilation in the Mammalian Upper Respiratory Tract

Pathogens evolve in specific host niches and microenvironments that provide the physical and nutritional requirements conducive to their growth. In addition to using the host as a source of food, bacterial pathogens must avoid the immune response to their presence. The mammalian upper respiratory tract is a site that is exposed to the external environment, and is readily colonized by bacteria that live as resident flora or as pathogens. These bacteria can remain localized, descend to the lower respiratory tract, or traverse the epithelium to disseminate throughout the body. By virtue of their successful colonization of the respiratory epithelium, these bacteria obtain the nutrients needed for growth, either directly from host resources or from other microbes. This chapter describes the upper respiratory tract environment, including its tissue and mucosal structure, prokaryotic biota, and biochemical composition that would support microbial life. Neisseria meningitidis and the Bordetella species are discussed as examples of bacteria that have no known external reservoirs but have evolved to obligately colonize the mammalian upper respiratory tract.

Biomedical applications of nisin

Nisin is a bacteriocin produced by a group of Gram-positive bacteria that belongs to Lactococcus and Streptococcus species. Nisin is classified as a Type A (I) lantibiotic that is synthesized from mRNA and the translated peptide contains several unusual amino acids due to post-translational modifications. Over the past few decades, nisin has been used widely as a food biopreservative. Since then, many natural and genetically modified variants of nisin have been identified and studied for their unique antimicrobial properties. Nisin is FDA approved and generally regarded as a safe peptide with recognized potential for clinical use. Over the past two decades the application of nisin has been extended to biomedical fields. Studies have reported that nisin can prevent the growth of drug-resistant bacterial strains, such as methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, Enterococci and Clostridium difficile. Nisin has now been shown to have antimicrobial activity against both Gram-positive and Gram-negative disease-associated pathogens. Nisin has been reported to have anti-biofilm properties and can work synergistically in combination with conventional therapeutic drugs. In addition, like host-defence peptides, nisin may activate the adaptive immune response and have an immunomodulatory role. Increasing evidence indicates that nisin can influence the growth of tumours and exhibit selective cytotoxicity towards cancer cells. Collectively, the application of nisin has advanced beyond its role as a food biopreservative. Thus, this review will describe and compare studies on nisin and provide insight into its future biomedical applications.

Antimicrobial proteins and peptides in human lung diseases: A friend and foe partnership with host proteases

Lung antimicrobial proteins and peptides (AMPs) are major sentinels of innate immunity by preventing microbial colonization and infection. Nevertheless bactericidal activity of AMPs against Gram-positive and Gram-negative bacteria is compromised in patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and asthma. Evidence is accumulating that expression of harmful human serine proteases, matrix metalloproteases and cysteine cathepsins is markedely increased in these chronic lung diseases. The local imbalance between proteases and protease inhibitors compromises lung tissue integrity and function, by not only degrading extracellular matrix components, but also non-matrix proteins. Despite the fact that AMPs are somewhat resistant to proteolytic degradation, some human proteases cleave them efficiently and impair their antimicrobial potency. By contrast, certain AMPs may be effective as antiproteases. Host proteases participate in concert with bacterial proteases in the degradation of key innate immunity peptides/proteins and thus may play immunomodulatory activities during chronic lung diseases. In this context, the present review highlights the current knowledge and recent discoveries on the ability of host enzymes to interact with AMPs, providing a better understanding of the role of human proteases in innate host defense.

Fighting microbial infections: A lesson from amphibian skin-derived esculentin-1 peptides

Due to the growing emergence of resistance to commercially available antibiotics/antimycotics in virtually all clinical microbial pathogens, the discovery of alternative anti-infective agents, is greatly needed. Gene-encoded antimicrobial peptides (AMPs) hold promise as novel therapeutics. In particular, amphibian skin is one of the richest storehouses of AMPs, especially that of the genus Rana, with esculentins-1 being among the longest (46 amino acids) AMPs found in nature to date. Here, we report on the recently discovered in vitro and in vivo activities and mechanism of action of two derivatives of the N-terminal part of esculentin-1a and -1b peptides, primarily against two relevant opportunistic microorganisms causing a large number of life-threatening infections worldwide; i.e. the Gram-negative bacterium Pseudomonas aeruginosa and the yeast Candida albicans. Because of distinct advantages compared to several mammalian AMPs, the two selected frog skin AMP-derivatives represent attractive candidates for the development of new antimicrobial compounds with expanded properties, for both human and veterinary medicine.

Protective properties of lysozyme on β-amyloid pathology: implications for Alzheimer disease

The hallmarks of Alzheimer disease are amyloid-β plaques and neurofibrillary tangles accompanied by signs of neuroinflammation. Lysozyme is a major player in the innate immune system and has recently been shown to prevent the aggregation of amyloid-β1-40 in vitro. In this study we found that patients with Alzheimer disease have increased lysozyme levels in the cerebrospinal fluid and lysozyme co-localized with amyloid-β in plaques. In Drosophila neuronal co-expression of lysozyme and amyloid-β1-42 reduced the formation of soluble and insoluble amyloid-β species, prolonged survival and improved the activity of amyloid-β1-42 transgenic flies. This suggests that lysozyme levels rise in Alzheimer disease as a compensatory response to amyloid-β increases and aggregation. In support of this, in vitro aggregation assays revealed that lysozyme associates with amyloid-β1-42 and alters its aggregation pathway to counteract the formation of toxic amyloid-β species. Overall, these studies establish a protective role for lysozyme against amyloid-β associated toxicities and identify increased lysozyme in patients with Alzheimer disease. Therefore, lysozyme has potential as a new biomarker as well as a therapeutic target for Alzheimer disease.

Structural basis of a temporin 1b analogue antimicrobial activity against Gram negative bacteria determined by CD and NMR techniques in cellular environment

We here report an original approach to elucidate mechanisms of action of antimicrobial peptides and derive crucial structural requirements for the design of novel therapeutic agents. The high resolution structure of TB_KKG6A, an antimicrobial peptide designed to amplify the spectrum of action of Temporin B, bound to E. coli is here determined by means of CD and NMR methodologies. We have also defined, through STD analysis, the residues in closer proximity to the bacterial membrane.

Antimicrobial defense of the intestine

The mammalian gastrointestinal tract is home to a dense community of resident bacteria and is also exposed to microorganisms from the external environment. The epithelial surface of the intestine plays a critical role in host protection by producing a diverse repertoire of antimicrobial proteins that directly kill or hinder the growth of microorganisms. Here we discuss the general principles that govern the mechanisms of action of epithelial antimicrobial proteins, regulation of antimicrobial protein expression and activity, and in vivo functions of intestinal antimicrobial proteins. We also consider how altered antimicrobial protein expression and function can contribute to disease and how these endogenous antibiotics might be harnessed for the benefit of human health.

pH modulates the activity and synergism of the airway surface liquid antimicrobials β-defensin-3 and LL-37

The pulmonary airways are continuously exposed to bacteria. As a first line of defense against infection, the airway surface liquid (ASL) contains a complex mixture of antimicrobial factors that kill inhaled and aspirated bacteria. The composition of ASL is critical for antimicrobial effectiveness. For example, in cystic fibrosis an abnormally acidic ASL inhibits antimicrobial activity. Here, we tested the effect of pH on the activity of an ASL defensin, human β-defensin-3 (hBD-3), and the cathelicidin-related peptide, LL-37. We found that reducing pH from 8.0 to 6.8 reduced the ability of both peptides to kill Staphylococcus aureus. An acidic pH also attenuated LL-37 killing of Pseudomonas aeruginosa. In addition, we discovered synergism between hBD-3 and LL-37 in killing S. aureus. LL-37 and lysozyme were also synergistic. Importantly, an acidic pH reduced the synergistic effects of combinations of ASL antibacterials. These results indicate that an acidic pH reduces the activity of individual ASL antimicrobials, impairs synergism between them, and thus may disrupt an important airway host defense mechanism.

Linking increased airway hydration, ciliary beating, and mucociliary clearance through ENaC inhibition

Airway dehydration causes mucus stasis and bacterial overgrowth in cystic fibrosis and chronic bronchitis (CB). Rehydration by hypertonic saline is efficacious but suffers from a short duration of action. We tested whether epithelial sodium channel (ENaC) inhibition would rehydrate normal and dehydrated airways to increase mucociliary clearance (MCC) over a significant time frame. For this, we used a tool compound (Compound A), which displays nanomolar ENaC affinity and retention in the airway surface liquid (ASL). Using normal human bronchial epithelial cultures (HBECs) grown at an air-liquid interface, we evaluated in vitro potency and efficacy using short-circuit current (I(sc)) and ASL height measurements where it inhibited I(sc) and increased ASL height by ∼ 50% (0.052 μM at 6 h), respectively. The in vivo efficacy was investigated in a modified guinea pig tracheal potential difference model, where we observed an effective dose (ED50) of 5 μg/kg (i.t.), and by MCC measures in rats and sheep, where we demonstrated max clearance rates at 100 μg/kg (i.t.) and 75 μg/kg (i.t.), respectively. Acute cigarette smoke-induced ASL height depletion in HBECs was used to mimic the situation in patients with CB, and pretreatment prevented both cigarette smoke-induced ASL dehydration and lessened the decrease in ciliary beat frequency. Furthermore, when added after cigarette smoke exposure, Compound A increased the rate of ASL rehydration. In conclusion, Compound A demonstrated significant effects and a link between increased airway hydration, ciliary function, and MCC. These data support the hypothesis that ENaC inhibition may be efficacious in the restoration of mucus hydration and transport in patients with CB.