Antimicrobial peptides: Defending the mucosal epithelial barrier

Salivary lactoferrin levels in Down Syndrome: a case-control study

Individuals with Down Syndrome (DS) have a high age-dependent risk of developing Alzheimer's disease (AD). In addition to genetic causes, this high risk involves dysregulated immune-inflammatory system. Low lactoferrin levels, one of the main antimicrobial proteins present in saliva, has been associated with AD. Here, we evaluated whether salivary lactoferrin levels change across the life span of individuals with DS. The study included 152 participants, 72 subjects with DS and 80 euploid individuals, and were divided into those under and over 45 years of age, accordingly with the age-dependent risk of AD. Median of salivary lactoferrin were higher among DS individual, in parallel to salivary total protein, but there were no differences in the ratio of lactoferrin to total protein in saliva between groups. Only DS individuals had higher median salivary lactoferrin levels in the age group under 45 years. Meanwhile non-significant differences were detected for the ratio salivary lactoferrin levels to total salivary protein between groups under 45 years, those levels were lower in DS subjects over 45 years old compared with the age-matched control group. Furthermore, the ratio of salivary lactoferrin levels to total protein in DS was associated with cognitive decline being lower in demented groups compared with mild and moderate cognitive impairment groups. In summary, this study indicates that salivary lactoferrin was dysregulated in DS, with significant lower ratio of salivary lactoferrin levels to total salivary proteins in individuals with DS over 45 years old, a population with a gradually increasing risk of AD.

Exploring the intricate relationship between peptic ulcers and immunohematological responses: A narrative review

Peptic ulcers have long been a focus of medical research due to their significant impact on public health worldwide. Traditionally attributed to factors such as Helicobacter pylori infection and excessive gastric acid secretion, recent scientific endeavors have increasingly unveiled the pivotal role of immunohematological responses in the pathogenesis and clinical course of peptic ulcers. This review aims to synthesize and analyze the intricate relationship between peptic ulcers and immunohematological responses, shedding light on the complex interplay between the immune system and ulcer development, progression, and healing. Immunological factors, encompassing inflammatory mediators, immune cells, and the host response to H pylori, play a substantial role in the multifaceted landscape of peptic ulcers. Inflammation orchestrated by cytokines and chemokines derived from immune cells intricately contributes to mucosal damage and repair processes. Moreover, the chronic nature of H pylori infection triggers a cascade of immune responses, involving both innate and adaptive immunity, which significantly influences the course of ulceration. This paper consolidates current knowledge while highlighting the need for further research elucidating the intricate immunological pathways involved in peptic ulcer pathogenesis. The integration of immunology into the broader context of peptic ulcer disease presents opportunities for innovative therapeutic interventions aimed at modulating immune responses for improved clinical outcomes and enhanced patient care. Ultimately, unraveling the intricate relationship between peptic ulcers and immunohematological responses holds significant promise in advancing the understanding and management of this prevalent gastrointestinal disorder.

Card9 deficiency exacerbates vulvovaginal candidiasis by impairing the IL-17 production and vaginal epithelial barrier

Vulvovaginal candidiasis (VVC) is an inflammation caused by Candida albicans with a higher recurrence rate in individuals deficient in Card9. This study aimed to elucidate the mechanisms underlying this increased susceptibility. Estrogen-treated Card9-/- mice infected with C. albicans were used to model Card9 deficiency-related VVC. Our findings indicate that Card9 deficiency leads to a reduction in Th17 cells, interleukin (IL)-17-producing γδ T cells, and IL-17A secretion, weakens epithelial tight junctions, and reduces antimicrobial peptide secretion, leading to persistent fungal invasion. This persistent invasion results in excessive neutrophil recruitment and activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) and absent in melanoma 2 inflammasomes (AIM2), causing mucosal damage. In conclusion, Card9 deficiency compromises the vaginal epithelial barrier, prolongs C. albicans infection, and increases inflammation, highlighting the critical role of Card9 in maintaining immune function of vaginal mucosa.

Viral infection and antiviral immunity in the oral cavity

Individual tissues have distinct antiviral properties garnered through various mechanisms, including physical characteristics, tissue-resident immune cells and commensal organisms. Although the oral mucosa has long been appreciated as a critical barrier tissue that is exposed to a continuous barrage of pathogens, many fundamental aspects of the antiviral immune response in this tissue remain unknown. Several viral pathogens, such as herpesviruses and human papillomaviruses, have been acknowledged both historically and at present for infections in the oral cavity that result in substantial clinical burden. However, recent viral outbreaks, including those with SARS-CoV-2 and mpox, featured oral symptoms even though these viruses are not generally considered oral pathogens. Ensuing studies have shown that the oral cavity is an important locale for viral infection and potential transmission of newly emergent or re-emergent pathogens, highlighting the need for an increased understanding of the mechanisms of antiviral immunity at this site. In this Review, we provide a broad overview of antiviral immune responses in the oral cavity and discuss common viral infections and their manifestations in the oral mucosa. In addition, we present current mouse models for the study of oral viral infections.

The Role of Beta-Defensin 2 in Preventing Preterm Birth with Chorioamnionitis: Insights into Inflammatory Responses and Epithelial Barrier Protection

Antimicrobial peptides, such as beta-defensin 2 (BD2), are vital in controlling infections and immune responses. In this study, we investigated the expression and role of BD2 in the amniotic membrane and human amniotic epithelial cells (hAECs) from patients with preterm birth and chorioamnionitis, focusing on its regulation of inflammatory cytokines and its protective effect on the epithelial barrier. Our results show increased BD2 expression in chorioamnionitis, and Lipopolysaccharide (LPS)-induced inflammation increased BD2 release from hAECs in a dose- and time-dependent manner. BD2 treatment effectively modulated the inflammatory response by reducing pro-inflammatory cytokines (IL-6, IL-1β) and enhancing the release of the anti-inflammatory cytokine IL-10. Additionally, BD2 helps preserve epithelial barrier integrity by restoring E-cadherin expression and reducing Snail expression in inflamed hAECs. In an LPS-induced preterm birth mouse model, BD2 treatment delayed preterm delivery and reduced inflammatory cytokine levels. These results suggest that BD2 plays a protective role in preventing preterm birth by regulating inflammation and maintaining epithelial barrier function, highlighting its therapeutic potential for inflammation-related preterm birth.

Remote Preconditioning Provides Protection Against Retinal Cell Death From Retinal Detachment

Purpose

Remote preconditioning involves injury to a tissue that results in protection to a subsequent injury in a distal tissue. Here, we investigated the impact of remote preconditioning on retinal detachment (RD) injury, hypothesizing that a previous contralateral RD would protect the fellow retina against inflammation and cell death following its detachment.

Methods

RD was created in adult C57BL/6J mice with subretinal sodium hyaluronate injection. Preconditioning involved RD in the right eye at 1, 3, 7, or 28 days before left eye detachment, whereas the control group only received RD to the left eye. Retinas were harvested 24 hours post-left eye detachment in both groups. Cell death was assessed using Cell Death Detection ELISA and mRNA expression was evaluated via qRT-PCR.

Results

Contralateral RD promoted a transient protection against retinal cell death from 1 to 3 days and waned by 7 days compared with control RD retinas with intact fellow retinas. Contralateral RD significantly protected against post-RD cell death (P = 0.0002) and caspase 3 cleavage (P = 0.0449), compared with control RD retinas with intact fellow retinas 1-day post-RD. Detached fellow retinas from the preconditioning group expressed significantly less Tnfa (P = 0.0066), Cxcl10 (P = 0.0099), and Fas (P = 0.0223) mRNAs, compared with the detached retinas of the control group. In contrast, upregulation of type-I-IFN pathway genes, including Irf7 (P = 0.0106) and Ifit1 (P = 0.0740), following RD was higher in the preconditioning group.

Conclusions

RD in one eye produces a transient remote preconditioning effect that protects the fellow retina against retinal cell death following subsequent RD.

Aged garlic extract enhances the production of β‑defensin 4 via activation of the Wnt/β‑catenin pathway in mouse gingiva

Periodontal disease is recognized as a chronic multifactorial inflammatory condition initiated by dysbiosis within subgingival plaque biofilms. Antimicrobial peptides exhibit a wide spectrum of antimicrobial action, and thus, provide one of the first lines of host defense against oral pathogens. Aged garlic extract (AGE) is effective for preventing the progression of periodontal disease. The present study examined whether AGE affects the production of antimicrobial peptides in mouse gingiva. Reverse transcription-quantitative PCR analysis demonstrated that oral administration of AGE in mice increased the mRNA level of Defb4 in gingival tissue, while the levels of Defb1, Defb14 and Cramp remained unaffected. AGE also upregulated the protein levels of β-defensin 4. To explore the underlying mechanism of the increased β-defensin 4 production induced by AGE, a comprehensive phosphoproteomic analysis in gingival tissues was performed. Proteomic profiling revealed activation of the canonical Wnt/β-catenin pathway in gingiva of mice treated with AGE. Treatment of mouse gingival epithelial GE1 cells with AGE resulted in an increase of β-defensin 4 in the culture medium. In support of proteomics experiments, LF3, a specific inhibitor of Wnt/β-catenin signaling, suppressed the AGE-induced production of β-defensin 4. In addition, β-catenin protein was found to accumulate within the nucleus in cells treated with AGE. In conclusion, the present findings suggested that AGE enhanced the production of β-defensin 4 in mouse gingiva through the canonical Wnt signal transduction pathway.

Positive Role of Saliva in the Oral Microbiome

Saliva plays a pivotal role in shaping the oral microbiome and maintaining oral homeostasis and health. This chapter explores the importance of saliva in promoting eubiosis of the oral microbiome and its implications for oral and systemic health. Saliva is a dynamic fluid rich in antimicrobial components and buffering agents that contribute to the microbial balance and homeostasis within the oral cavity. It provides a cleansing mechanism that facilitates the removal of bacteria and debris and limits the growth and colonization of microorganisms. The salivary antimicrobial proteins and peptides, in combination with antibodies, predominantly secretory immunoglobulin A (sIgA), are crucial for combating microbial pathogens and preventing oral infections. Saliva also possesses a buffering mechanism that regulates the pH levels within the oral cavity, which creates an environment that is inimical for the growth of acid-producing pathogens and promotes remineralization of the teeth. Furthermore, salivary proteins and glycoproteins form an inter-face (tissue coat) over the oral mucosa and teeth to protect the oral tissue from external environmental insults, maintain tissue integrity, and promote wound healing. Understanding the positive role of saliva in the oral microbiome provides an insight into potential novel strategies for promoting oral health and combating microbial dysbiosis. Recognizing the multifaceted roles of saliva as a guardian (gatekeeper) of oral microbial balance, we can unlock the therapeutic potential of saliva in enhancing the well-being of the body and averting oral and systemic diseases.

Cleavage of cell junction proteins as a host invasion strategy in leptospirosis

Infection and invasion are the prerequisites for developing the disease symptoms in a host. While the probable mechanism of host invasion and pathogenesis is known in many pathogens, very little information is available on Leptospira invasion/pathogenesis. For causing systemic infection Leptospira must transmigrate across epithelial barriers, which is the most critical and challenging step. Extracellular and membrane-bound proteases play a crucial role in the invasion process. An extensive search for the proteins experimentally proven to be involved in the invasion process through cell junction cleavage in other pathogens has resulted in identifying 26 proteins. The similarity searches on the Leptospira genome for counterparts of these 26 pathogenesis-related proteins identified at least 12 probable coding sequences. The proteins were either extracellular or membrane-bound with a proteolytic domain to cleave the cell junction proteins. This review will emphasize our current understanding of the pathogenic aspects of host cell junction-pathogenic protein interactions involved in the invasion process. Further, potential candidate proteins with cell junction cleavage properties that may be exploited in the diagnostic/therapeutic aspects of leptospirosis will also be discussed. KEY POINTS: • The review focussed on the cell junction cleavage proteins in bacterial pathogenesis • Cell junction disruptors from Leptospira genome are identified using bioinformatics • The review provides insights into the therapeutic/diagnostic interventions possible.

Multiple mechanisms enable broad-spectrum activity of the Pelargonium sidoides root extract EPs 7630 against acute respiratory tract infections

There is clinical evidence showing that the Pelargonium sidoides root extract EPs 7630 is a safe and effective treatment for a range of acute infectious respiratory illnesses. Moreover, EPs 7630 has been shown to reduce the use of antibiotics, which is important in the context of rising antibiotic resistance levels. A wide range of mechanisms appears to contribute to the beneficial effects of EPs 7630, e.g. antibacterial, antiviral, immunomodulatory, and epithelial barrier effects. This broad spectrum of pharmacological activities seems to enable the clinical activity of EPs 7630 against multiple respiratory infections. In particular, the combination of antiviral and immunomodulatory effects may enable EPs 7630 to tackle acute viral respiratory infections both in early stages of the disease process, which are driven by virus replication, as well as in later stages, which are caused by an overshooting immune response. Hence, EPs 7630 is a prime example of a plant extract with evidence-based clinical efficacy, including a solid understanding of the underlying mechanisms of action. The example of EPs 7630 demonstrates that plant extracts have a potential role as evidence-based clinical treatments and that they deserve pre-clinical and clinical testing and investigation in the same way as any other drug class.

TLR4/7-mediated host-defense responses of gingival epithelial cells

Gingival epithelial cells (GECs) are physical and immunological barriers against outward pathogens while coping with a plethora of non-pathogenic commensal bacteria. GECs express several members of Toll-like receptors (TLRs) and control subsequent innate immune responses. TLR4 senses lipopolysaccharide (LPS) while TLR7/8 recognizes single-strand RNA (ssRNA) playing important roles against viral infection. However, their distinct roles in GECs have not been fully demonstrated. Here, we analyzed biological responses of GECs to  LPS and CL075, a TLR7/8 agonist. GE1, a mouse gingival epithelial cell line, constitutively express TLR4 and TLR7, but not TLR8, like primary skin keratinocytes. Stimulation of GE1 cells with CL075 induced cytokine, chemokine, and antimicrobial peptide  expressions, the pattern of which is rather different from that with LPS: higher mRNA levels of interferon (IFN) β, CXCL10, and β-defensin (BD) 14 (mouse homolog of human BD3); lower levels of tumor necrosis factor (TNF), CCL5, CCL11, CCL20, CXCL2, and CX3CL1. As for the intracellular signal transduction of GE1 cells, CL075 rapidly induced significant AKT phosphorylation but failed to activate IKKα/β-NFκB pathway, whereas LPS induced marked IKKα/β-NFκB activation without significant AKT phosphorylation. In contrast, both CL075 and LPS induced rapid IKKα/β-NFκB activation and AKT phosphorylation in a macrophage cell line. Furthermore, specific inhibition of AKT activity abrogated CL075-induced IFNβ, CXCL10, and BD14 mRNA expression in GE1 cells. Thus, TLR4/7 ligands appear to induce rather different host-defense responses of GECs through distinct intracellular signaling mechanisms.

Tethering of soluble immune effectors to mucin and chitin reflects a convergent and dynamic role in gut immunity

The immune system employs soluble effectors to shape luminal spaces. Antibodies are soluble molecules that effect immunological responses, including neutralization, opsonization, antibody-dependent cytotoxicity and complement activation. These molecules are comprised of immunoglobulin (Ig) domains. The N-terminal Ig domains recognize antigen, and the C-terminal domains facilitate their elimination through phagocytosis (opsonization). A less-recognized function mediated by the C-terminal Ig domains of the IgG class of antibodies (Fc region) involves the formation of multiple low-affinity bonds with the mucus matrix. This association anchors the antibody molecule to the matrix to entrap potential pathogens. Even though invertebrates are not known to have antibodies, protochordates have a class of secreted molecules containing Ig domains that can bind bacteria and potentially serve a similar purpose. The VCBPs (V region-containing chitin-binding proteins) possess a C-terminal chitin-binding domain that helps tether them to chitin-rich mucus gels, mimicking the IgG-mediated Fc trapping of microbes in mucus. The broad functional similarity of these structurally divergent, Ig-containing, secreted effectors makes a case for a unique form of convergent evolution within chordates. This opinion essay highlights emerging evidence that divergent secreted immune effectors with Ig-like domains evolved to manage immune recognition at mucosal surfaces in strikingly similar ways. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Intestinal Barrier Dysfunction and Gut Microbiota in Non-Alcoholic Fatty Liver Disease: Assessment, Mechanisms, and Therapeutic Considerations

Non-alcoholic fatty liver disease (NAFLD) is a type of metabolic stress liver injury closely related to insulin resistance (IR) and genetic susceptibility without alcohol consumption, which encompasses a spectrum of liver disorders ranging from simple hepatic lipid accumulation, known as steatosis, to the more severe form of steatohepatitis (NASH). NASH can progress to cirrhosis and hepatocellular carcinoma (HCC), posing significant health risks. As a multisystem disease, NAFLD is closely associated with systemic insulin resistance, central obesity, and metabolic disorders, which contribute to its pathogenesis and the development of extrahepatic complications, such as cardiovascular disease (CVD), type 2 diabetes mellitus, chronic kidney disease, and certain extrahepatic cancers. Recent evidence highlights the indispensable roles of intestinal barrier dysfunction and gut microbiota in the onset and progression of NAFLD/NASH. This review provides a comprehensive insight into the role of intestinal barrier dysfunction and gut microbiota in NAFLD, including intestinal barrier function and assessment, inflammatory factors, TLR4 signaling, and the gut-liver axis. Finally, we conclude with a discussion on the potential therapeutic strategies targeting gut permeability and gut microbiota in individuals with NAFLD/NASH, such as interventions with medications/probiotics, fecal transplantation (FMT), and modifications in lifestyle, including exercise and diet.

The mouse retinal pigment epithelium mounts an innate immune defense response following retinal detachment

The retinal pigment epithelium (RPE) maintains photoreceptor viability and function, completes the visual cycle, and forms the outer blood-retinal barrier (oBRB). Loss of RPE function gives rise to several monogenic retinal dystrophies and contributes to age-related macular degeneration. Retinal detachment (RD) causes separation of the neurosensory retina from the underlying RPE, disrupting the functional and metabolic relationships between these layers. Although the retinal response to RD is highly studied, little is known about how the RPE responds to loss of this interaction. RNA sequencing (RNA-Seq) was used to compare normal and detached RPE in the C57BL6/J mouse. The naïve mouse RPE transcriptome was compared to previously published RPE signature gene lists and from the union of these 14 genes (Bmp4, Crim1, Degs1, Gja1, Itgav, Mfap3l, Pdpn, Ptgds, Rbp1, Rnf13, Rpe65, Slc4a2, Sulf1 and Ttr) representing a core signature gene set applicable across rodent and human RPE was derived. Gene ontology enrichment analysis (GOEA) of the mouse RPE transcriptome identified expected RPE features and functions, such as pigmentation, phagocytosis, lysosomal and proteasomal degradation of proteins, and barrier function. Differentially expressed genes (DEG) at 1 and 7 days post retinal detachment (dprd) were defined as mRNA with a significant (padj≤0.05) fold change (FC) of 0.67 ≥ FC ≥ 1.5 in detached versus naïve RPE. The RPE transcriptome exhibited dramatic changes at 1 dprd, with 2297 DEG identified. The KEGG pathways and biological process GO groups related to innate immune responses were significantly enriched. Lipocalin 2 (Lcn2) and several chemokines were upregulated, while numerous genes related to RPE functions, such as pigment synthesis, visual cycle, phagocytosis, and tight junctions were downregulated at 1 dprd. The response was largely transient, with only 18 significant DEG identified at 7 dprd, including upregulation of complement gene C4b. Validation studies confirmed RNA-Seq results. Thus, the RPE quickly downregulates cell-specific functions and mounts an innate immune defense response following RD. Our data demonstrate that the RPE contributes to the inflammatory response to RD and may play a role in attraction of immune cells to the subretinal space.

Insights into the Relationship between Periodontitis and Systemic Sclerosis Based on the New Periodontitis Classification (2018): A Cross-Sectional Study

(1) Background: This study aimed to assess the periodontitis burden in systemic sclerosis patients and the possible association between them, and the degree to which some potential risk factors and two potential diagnostic biomarkers may account for this association. (2) Methods: This cross-sectional study included a test group (systemic sclerosis patients) and a control group (non-systemic sclerosis patients). Both groups benefited from medical, periodontal examination and saliva sampling to determine the salivary flow rate and two inflammatory biomarkers (calprotectin, psoriasin). A systemic sclerosis severity scale was established. (3) Results: In the studied groups, comparable periodontitis rates of 88.68% and 85.85%, respectively, were identified. There were no significant differences in the severity of periodontitis among different systemic sclerosis severity, or in the positivity for anti-centromere and anti-SCL70 antibodies. Musculoskeletal lesions were significantly more common in stage III/IV periodontitis (n = 33, 86.84%) than in those in stage I/II (n = 1, 100%, and n = 3, 37.5%, respectively) (p = 0.007). Comparable levels of the inflammatory mediators were displayed by the two groups. There were no significant differences in calprotectin and psoriasin levels between diffuse and limited forms of systemic sclerosis. (4) Conclusions: Within the limitations of the current study, no associations between systemic sclerosis and periodontitis, or between their risk factors, could be proven.

Effects of topical application of resveratrol on tight junction barrier and antimicrobial compound production in lactating goat mammary glands

In mammary glands, the formation of less-permeable tight junctions (TJs) and the production of antimicrobial compounds like lactoferrin and defensins are important for preventing mastitis. Resveratrol, a polyphenol contained in red grapes, is known to protect mammary epithelial cells (MECs) from oxidative stress; however, oral administration of resveratrol causes a decrease in certain biological processes through conjugation and metabolic conversion. In this study, we determined the beneficial effects of resveratrol on TJs and antimicrobial compounds in cultured goat MECs by adding it to the medium, and in lactating goat mammary glands by topical application for percutaneous absorption. TJ barrier function was evaluated by transepithelial resistance and expression or localization pattern of claudins for culture model in vitro and by somatic cell count, Na+, albumin, and IgG in milk for topical application in vivo. Concentrations of antimicrobial compounds and cytokines were measured using ELISA. Activation of STAT3 was evaluated by Western blotting. Resveratrol strengthened TJ barrier function by upregulating claudin-3 in cultured MECs and topical application to udders reduced somatic cell count, Na+, albumin, and IgG in milk. Resveratrol increased β-defensin and S100A7 levels in cultured MECs and milk. In addition, resveratrol down-regulated cytokine production and STAT3 pathway. These findings suggest that the topical application of resveratrol to udders may be effective in preventing mastitis.

Bacterial synergies and antagonisms affecting Pseudomonas aeruginosa virulence in the human lung, skin and intestine

Pseudomonas aeruginosa requires a significant breach in the host defense to cause an infection. While its virulence factors are well studied, its tropism cannot be explained only by studying its interaction with the host. Why are P. aeruginosa infections so rare in the intestine compared with the lung and skin? There is not enough evidence to claim specificity in virulence factors deployed by P. aeruginosa in each anatomical site, and host physiology differences between the lung and the intestine cannot easily explain the observed differences in virulence. This perspective highlights a relatively overlooked parameter in P. aeruginosa virulence, namely, potential synergies with bacteria found in the human skin and lung, as well as antagonisms with bacteria of the human intestine.

Advances in antimicrobial hydrogels for dental tissue engineering: regenerative strategies for endodontics and periodontics

Dental tissue infections have been affecting millions of patients globally leading to pain, severe tissue damage, or even tooth loss. Commercial sterilizers may not be adequate to prevent frequent dental infections. Antimicrobial hydrogels have been introduced as an effective therapeutic strategy for endodontics and periodontics since they have the capability of imitating the native extracellular matrix of soft tissues. Hydrogel networks are considered excellent drug delivery platforms due to their high-water retention capacity. In this regard, drugs or nanoparticles can be incorporated into the hydrogels to endow antimicrobial properties as well as to improve their regenerative potential, once biocompatibility criteria are met avoiding high dosages. Herein, novel antimicrobial hydrogel formulations were discussed for the first time in the scope of endodontics and periodontics. Such hydrogels seem outstanding candidates especially when designed not only as simple volume fillers but also as smart biomaterials with condition-specific adaptability within the dynamic microenvironment of the defect site. Multifunctional hydrogels play a pivotal role against infections, inflammation, oxidative stress, etc. along the way of dental regeneration. Modern techniques (e.g., 3D and 4D-printing) hold promise to develop the next generation of antimicrobial hydrogels together with their limitations such as infeasibility of implantation.

Complementary Activities of Host Defence Peptides and Antibiotics in Combating Antimicrobial Resistant Bacteria

Due to their ability to eliminate antimicrobial resistant (AMR) bacteria and to modulate the immune response, host defence peptides (HDPs) hold great promise for the clinical treatment of bacterial infections. Whereas monotherapy with HDPs is not likely to become an effective first-line treatment, combinations of such peptides with antibiotics can potentially provide a path to future therapies for AMR infections. Therefore, we critically reviewed the recent literature regarding the antibacterial activity of combinations of HDPs and antibiotics against AMR bacteria and the approaches taken in these studies. Of the 86 studies compiled, 56 featured a formal assessment of synergy between agents. Of the combinations assessed, synergistic and additive interactions between HDPs and antibiotics amounted to 84.9% of the records, while indifferent and antagonistic interactions accounted for 15.1%. Penicillin, aminoglycoside, fluoro/quinolone, and glycopeptide antibiotic classes were the most frequently documented as interacting with HDPs, and Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium were the most reported bacterial species. Few studies formally evaluated the effects of combinations of HDPs and antibiotics on bacteria, and even fewer assessed such combinations against bacteria within biofilms, in animal models, or in advanced tissue infection models. Despite the biases of the current literature, the studies suggest that effective combinations of HDPs and antibiotics hold promise for the future treatment of infections caused by AMR bacteria.

Consensus Gene Network Analysis Identifies the Key Similarities and Differences in Endothelial and Epithelial Cell Dynamics after Candida albicans Infection

Endothelial and epithelial cells are morphologically different and play a critical role in host defense during Candida albicans infection. Both cells respond to C. albicans infection by activating various signaling pathways and gene expression patterns. Their interactions with these pathogens can have beneficial and detrimental effects, and a better understanding of these interactions can help guide the development of new therapies for C. albicans infection. To identify the differences and similarities between human endothelial and oral epithelial cell transcriptomics during C. albicans infection, we performed consensus WGCNA on 32 RNA-seq samples by relating the consensus modules to endothelial-specific modules and analyzing the genes connected. This analysis resulted in the identification of 14 distinct modules. We demonstrated that the magenta module correlates significantly with C. albicans infection in each dataset. In addition, we found that the blue and cyan modules in the two datasets had opposite correlation coefficients with a C. albicans infection. However, the correlation coefficients and p-values between the two datasets were slightly different. Functional analyses of the hub of genes from endothelial cells elucidated the enrichment in TNF, AGE-RAGE, MAPK, and NF-κB signaling. On the other hand, glycolysis, pyruvate metabolism, amino acid, fructose, mannose, and vitamin B6 metabolism were enriched in epithelial cells. However, mitophagy, necroptosis, apoptotic processes, and hypoxia were enriched in both endothelial and epithelial cells. Protein-protein interaction analysis using STRING and CytoHubba revealed STAT3, SNRPE, BIRC2, and NFKB2 as endothelial hub genes, while RRS1, SURF6, HK2, and LDHA genes were identified in epithelial cells. Understanding these similarities and differences may provide new insights into the pathogenesis of C. albicans infections and the development of new therapeutic targets and interventional strategies.

Progress towards the clinical use of antimicrobial peptides: challenges and opportunities

INTRODUCTION

To overcome the challenge of multidrug resistance, natural and synthetic peptides are candidates to become the basis of innovative therapeutics, featuring diverse mechanisms of action. Traditionally, the time elapsed from medical discoveries to their application is long. The urgency derived from the emergence of antibiotic resistance recommends an acceleration of research to put the new weapons in the hands of clinicians.

AREAS COVERED

This narrative review introduces ideas and suggestions of new strategies that may be used as a basis upon which to recommend reduced development times and to facilitate the arrival of new molecules in the fight against microbes.

EXPERT OPINION

Although studies on new innovative antimicrobial treatments are being conducted, sooner rather than later, more clinical trials, preclinical and translational research are needed to promote the development of innovative antimicrobial treatments for multidrug resistant infections. The situation is worrying, no less than that generated by pandemics such as the ones we have just experienced and conflicts such as world wars. Although from the point of view of human perception, resistance to antibiotics may not seem as serious as these other situations, it is possibly the hidden pandemic that most jeopardizes the future of medicine.

The deubiquitinase OTUD4 inhibits the expression of antimicrobial peptides in Paneth cells to support intestinal inflammation and bacterial infection

Dysfunction of the intestinal epithelial barrier causes microbial invasion that would lead to inflammation in the gut. Antimicrobial peptides (AMPs) are essential components of the intestinal epithelial barrier, while the regulatory mechanisms of AMPs expression are not fully characterized. Here, we report that the ovarian tumor family deubiquitinase 4 (OTUD4) in Paneth cells restricts the expression of AMPs and thereby promotes experimental colitis and bacterial infection. OTUD4 is upregulated in the inflamed mucosa of ulcerative colitis patients and in the colon of mice treated with dextran sulfate sodium salt (DSS). Knockout of OTUD4 promotes the expression of AMPs in intestinal organoids after stimulation with lipopolysaccharide (LPS) or peptidoglycan (PGN) and in the intestinal epithelial cells (IECs) of mice after DSS treatment or Salmonella typhimurium (S.t.) infection. Consistently, Vil-Cre;Otud4fl/fl mice and Def-Cre;Otud4fl/fl mice exhibit hyper-resistance to DSS-induced colitis and S.t. infection compared to Otud4fl/fl mice. Mechanistically, knockout of OTUD4 results in hyper K63-linked ubiquitination of MyD88 and increases the activation of NF-κB and MAPKs to promote the expression of AMPs. These findings collectively highlight an indispensable role of OTUD4 in Paneth cells to modulate AMPs production and indicate OTUD4 as a potential target for gastrointestinal inflammation and bacterial infection.

An Overview of the Potentialities of Antimicrobial Peptides Derived from Natural Sources

Antimicrobial peptides (AMPs) are constituents of the innate immune system in every kind of living organism. They can act by disrupting the microbial membrane or without affecting membrane stability. Interest in these small peptides stems from the fear of antibiotics and the emergence of microorganisms resistant to antibiotics. Through membrane or metabolic disruption, they defend an organism against invading bacteria, viruses, protozoa, and fungi. High efficacy and specificity, low drug interaction and toxicity, thermostability, solubility in water, and biological diversity suggest their applications in food, medicine, agriculture, animal husbandry, and aquaculture. Nanocarriers can be used to protect, deliver, and improve their bioavailability effectiveness. High cost of production could limit their use. This review summarizes the natural sources, structures, modes of action, and applications of microbial peptides in the food and pharmaceutical industries. Any restrictions on AMPs' large-scale production are also taken into consideration.