Paneth cells, antimicrobial peptides and maintenance of intestinal homeostasis. Nat Rev Microbiol. 2011;9:356-368. [PMID: 21423246 DOI: 10.1038/nrmicro2546]

The Gut in Critical Illness

PURPOSE OF REVIEW

The purpose of this narrative review is to describe the mechanisms for gut dysfunction during critical illness, outline hypotheses of gut-derived inflammation, and identify nutrition and non-nutritional therapies that have direct and indirect effects on preserving both epithelial barrier function and gut microbiota during critical illness.

RECENT FINDINGS

Clinical and animal model studies have demonstrated that critical illness pathophysiology and interventions breach epithelial barrier function and convert a normally commensal gut microbiome into a pathobiome. As a result, the gut has been postulated to be the "motor" of critical illness and numerous hypotheses have been put forward to explain how it contributes to systemic inflammation and drives multiple organ failure. Strategies to ameliorate gut dysfunction have focused on maintaining gut barrier function and promoting gut microbiota commensalism. The trajectory of critical illness may be closely related to gut epithelial barrier function, the gut microbiome and interventions that may contribute towards a deleterious pathobiome with immune dysregulation.

Microbial diversity and fitness in the gut-brain axis: influences on developmental risk for Alzheimer's disease

The gut-brain axis (GBA) denotes the dynamic and bidirectional communication system that connects the gastrointestinal tract and the central nervous system (CNS). This review explored this axis, focusing on the role of microbial diversity and fitness in maintaining gastrointestinal health and preventing neurodegeneration, particularly in Alzheimer's disease (AD). Gut dysbiosis, characterized by the imbalance in populations of beneficial and harmful bacteria, has been associated with increased systemic inflammation, neuroinflammation, and the progression of AD through pathogenic mechanisms involving amyloid deposition, tauopathy, and increased blood-brain barrier (BBB) permeability. Emerging evidence highlighted the therapeutic potential of probiotics, dietary interventions, and intermittent fasting in restoring microbial balance, reducing inflammation, and minimizing neurodegenerative risks. Probiotics and synbiotics are promising in helping improve cognitive function and metabolic health, while dietary patterns like the Mediterranean diet were linked to decreased neuroinflammation and enhanced gut-brain communication. Despite significant advancement, further research is needed to elucidate the specific microbial strains, metabolites, and mechanisms influencing brain health. Future studies employing longitudinal designs and advanced omics technologies are essential to developing targeted microbiome-based therapies for managing AD-related disorders.

Human Defensins: Structure, Function, and Potential as Therapeutic Antimicrobial Agents with Highlights Against SARS CoV-2

The human defensins are a group of cationic antimicrobial peptides that range in size from 2 to 5 kDa and share a common structural motif of six disulphide-linked cysteines. Several naturally occurring human α- and β-defensins have been identified over the past two decades. They have a wide variety of antimicrobial effects, and their potential to avoid the development of resistance to antimicrobial treatment makes them attractive as therapeutic agents. Human defensins have recently been the focus of medical and molecular biology studies due to their promising application in medicine and the pharmaceutical industry. This work aims to provide a comprehensive summary of the current developments of human defensins, including their identification, categorization, molecular features, expression, modes of action, and potential application in medical settings. Current obstacles and future opportunities for using human defensins are also covered. Furthermore, we shed light on the potential of this class as an antiviral agent, particularly against SARS CoV-2, by providing an in silico-based investigation of their plausible mechanisms of action.

AhR-Dependent Induction of β-Defensin 1 in Colonic Epithelial Cells Regulates Cross-Talk between Gut Microbiota and Immune Response Leading to Attenuation of Colitis

The aryl hydrocarbon receptor (AhR) acts as a critical signaling hub that connects immune cells, food and environmental cues, and microbiota to regulate intestinal homeostasis. In the current study, the role of AhR in the regulation of an antimicrobial peptide, β-defensin1 (BD-1) is investigated to control colitis. Human patients with ulcerative colitis (UC) and Crohn's disease (CD), and mice with three different models of colitis, express a significant decrease in the expression of BD-1 in colonic epithelial cells (CECs). Dietary and environmental AhR ligands induce the expression of BD-1 in CECs through the activation of two dioxin-responsive elements (DREs) expressed on its promoter. AhR ligands attenuate colitis in wild-type (WT) mice while inducing BD-1. However, AhR ligands fail to induce BD-1 and protect mice from colitis when there is an intestinal epithelial cell (IEC)-specific deletion of AhR. Blocking BD1 in vivo using antibodies prevents the ability of AhR ligands to ameliorate colitis, restore dysbiosis, and attenuate colonic inflammation. The current study identifies a novel pathway involving dietary, environmental, and endogenous AhR ligands to induce the antimicrobial peptide BD-1 in IECs, which in turn, plays a critical role in the regulation of intestinal homeostasis.

The signature of the small intestinal epithelial and immune cells in health and diseases

ABSTRACT

The small intestine is essential for digestion, nutrient absorption, immune regulation, and microbial balance. Its epithelial lining, containing specialized cells like Paneth and tuft cells, is crucial for maintaining intestinal homeostasis. Paneth cells produce antimicrobial peptides and growth factors that support microbial regulation and intestinal stem cells, while tuft cells act as chemosensors, detecting environmental changes and modulating immune responses. Along with immune cells such as intraepithelial lymphocytes, innate lymphoid cells, T cells, and macrophages, they form a strong defense system that protects the epithelial barrier. Disruptions in this balance contribute to chronic inflammation, microbial dysbiosis, and compromised barrier function-key features of inflammatory bowel disease, celiac disease, and metabolic syndromes. Furthermore, dysfunctions in the small intestine and immune cells are linked to systemic diseases like obesity, diabetes, and autoimmune disorders. Recent research highlights promising therapeutic strategies, including modulation of epithelial and immune cell functions, probiotics, and gene editing to restore gut health and address systemic effects. This review emphasizes the pivotal roles of small intestinal epithelia and immune cells in maintaining intestinal homeostasis, their involvement in disease development, and emerging treatments for intestinal and systemic disorders.

Lipid Shape as a Membrane Activity Modulator of a Fusogenic Antimicrobial Peptide

An intriguing feature of many bacterial membranes is their prevalence of non-bilayer-forming lipids, such as the cone-shaped phosphatidylethanolamines and cardiolipins. Many membrane-active antimicrobial peptides lower the bilayer-to-hexagonal phase transition energy barrier in membranes containing such types of cone-shaped lipids. Here, we systematically studied how the molecular shape of lipids affects the activity of antimicrobial peptide EcDBS1R4, which is known to be an efficient fusogenic peptide. Using coarse-grained molecular dynamics simulations, we show the ability of EcDBS1R4 to form "hourglass-shaped" pores, which is inhibited by cone-shaped lipids. The abundance of cone-shaped lipids further correlates with the propensity of this peptide to oligomerize preferentially in antiparallel dimers. We also observe that EcDBS1R4 promotes the segregation of the anionic lipids. When coupled to dimerization, this charge segregation leads to regions in the bilayer that are devoid of peptides and rich in zwitterionic lipids. Our results indicate a protective role of cone-shaped lipids in bacterial membranes against pore-mediated permeabilization by EcDBS1R4.

Immune modulation for the patterns of epithelial cell death in inflammatory bowel disease

Inflammatory bowel disease (IBD) is an inflammatory disease of the intestine whose primary pathological presentation is the destruction of the intestinal epithelium. The intestinal epithelium, located between the lumen and lamina propria, transmits luminal microbial signals to the immune cells in the lamina propria, which also modulate the intestinal epithelium. In IBD patients, intestinal epithelial cells (IECs) die dysfunction and the mucosal barrier is disrupted, leading to the recruitment of immune cells and the release of cytokines. In this review, we describe the structure and functions of the intestinal epithelium and mucosal barrier in the physiological state and under IBD conditions, as well as the patterns of epithelial cell death and how immune cells modulate the intestinal epithelium providing a reference for clinical research and drug development of IBD. In addition, according to the targeting of epithelial apoptosis and necroptotic pathways and the regulation of immune cells, we summarized some new methods for the treatment of IBD, such as necroptosis inhibitors, microbiome regulation, which provide potential ideas for the treatment of IBD. This review also describes the potential for integrating AI-driven approaches into innovation in IBD treatments.

Distribution of epithelial endoplasmic reticulum stress-related proteins in adult and pediatric Crohn's disease: Association with inflammation and fibrosis

BACKGROUND/AIMS

Intestinal strictures in Crohn's disease (CD), driven by fibrosis remain challenging to treat. Current treatments focus on inflammation, but are less effective against fibrosis. Endoplasmic Reticulum Stress-Related Proteins, including Protein disulfide isomerases (PDIs), may contribute to fibrosis; their roles in CD remain unclear. This study investigated the distribution of AGR2, BiP, PDIA6, ERP44 in intestinal epithelium and their association with fibrosis and inflammation in pediatric and adult CD.

METHODS

We retrospectively analyzed 224 patients (2009-2023). CD patients with and without strictures, non IBD controls, and ulcerative colitis patients were compared. Immunohistochemistry assessed Endoplasmic Reticulum Stress-Related protein distribution in epithelium. H&E and Masson's trichrome staining evaluated inflammation and fibrosis. Correlations between protein distribution, inflammation and fibrosis were examined.

RESULTS

AGR2 and BiP were increased in fibro-inflammatory and fibrotic intestinal epithelial tissues, especially in pediatric-onset CD. ERP44 was associated with fibrosis exclusively in pediatric CD. PDIA6 was upregulated in CD compared to non IBD, without fibrosis association. Distinct protein distribution patterns were observed between pediatric and adult CD, and between ileum and colon.

CONCLUSIONS

Distinct patterns of AGR2, BiP, PDIA6, and ERP44 in fibrotic and inflammatory intestinal tissues suggest potential roles in CD-associated fibrosis, warranting exploration as biomarkers or therapeutic targets.

The impact of ivermectin-loaded solid lipid nanoparticles on the enteric phase of experimental trichinellosis

Trichinellosis is a global zoonotic disease affecting humans and nearly all animal species. The intestinal (enteric) phase of trichinellosis is critical, as it determines the course and prognosis of the disease. The medications used in the management of trichinellosis demonstrate inadequate bioavailability, along with a significant level of resistance. Therefore, there is a need for the development of novel agents that enhance the bioavailability of administered medications. Nanobiotechnology has emerged as a significant strategy in treating parasitic diseases. This study examined the use of solid lipid nanoparticles (SLNs) to improve the efficacy of oral ivermectin (IVM) in treating the enteric phase of trichinellosis. Thirty-five Swiss albino mice were divided into seven equal groups as follows: negative control, positive control, albendazole, ivermectin, SLNs, ivermectin loaded on solid lipid nanoparticles (IVM-SLNs), and a combination of IVM-SLNs and albendazole. Mice were sacrificed on the seventh day post-infection. The drugs' effects were assessed using parasitological, biochemical, histological, histochemical and immunohistochemical analyses. The co-administration of albendazole and IVM-SLNs resulted in a significant decrease in adult burden, inflammatory cell infiltration, and apoptosis. Furthermore, a significant reduction in Cyclooxygenase-2 (COX-2) expression was observed compared to the infected untreated control group, along with improved liver and kidney function indices. In conclusion, the potent trichinocidal effect of a single oral dose of IVM-SLNs against Trichinella adults makes them a promising alternative or adjunct to existing nematicidal agents.

Commensalism and pathogenesis of Candida albicans at the mucosal interface

Fungi are important and often underestimated human pathogens. Infections with fungi mostly originate from the environment, from soil or airborne spores. By contrast, Candida albicans, one of the most common and clinically important fungal pathogens, permanently exists in the vast majority of healthy individuals as a member of the human mucosal microbiota. Only under certain circumstances will these commensals cause infections. However, although the pathogenic behaviour and disease manifestation of C. albicans have been at the centre of research for many years, its asymptomatic colonization of mucosal surfaces remains surprisingly understudied. In this Review, we discuss the interplay of the fungus, the host and the microbiome on the dualism of commensal and pathogenic life of C. albicans, and how commensal growth is controlled and permitted. We explore hypotheses that could explain how the mucosal environment shapes C. albicans adaptations to its commensal lifestyle, while still maintaining or even increasing its pathogenic potential.

Inulin Diet Alleviates Abdominal Aortic Aneurysm by Increasing Akkermansia and Improving Intestinal Barrier

Background/Objectives: Previous studies have shown varying efficacy of high-fiber diets containing different ingredients in abdominal aortic aneurysms (AAAs). This study aimed to identify which high-fiber diet protects against AAA in mice and elucidate the underlying mechanisms. Methods: This study compared inulin, cellulose, and chow diets in terms of their impact on aneurysm enlargement, elastin degradation, matrix metalloproteinase 2 and 9 expressions, CD3+ T cell and CD68+ macrophage infiltration, and macrophage differentiation. It also examined gut microbiota composition, focusing on Akkermansia, and evaluated intestinal barrier function and systemic inflammatory response. Results: The inulin diet, but not the cellulose diet, compared with the chow diet, reduced aneurysm enlargement, elastin degradation, matrix metalloproteinase 2 and 9 expressions, CD3+ T cell and CD68+ macrophage infiltration, and skewed macrophage towards M2 differentiation. The inulin diet enriched Akkermansia in both the small and large intestine. The inulin diet also enhanced the intestinal barrier by augmenting goblet cells, upregulating the gene related to the epithelial barrier and antibacterial peptides in the small intestine, and reducing circulating lipopolysaccharide and interleukin-1β levels. The inulin diet lowered the proportion of Ly6Chi monocytes and C-C chemokine receptor 2 expression on these cells in the bone marrow, reducing aneurysm infiltration. Administering Akkermansia to AAA mice decreased intestinal permeability and mitigated AAA. Conclusions: A diet rich in fermentable fiber inulin, as opposed to cellulose, alleviates AAA in mice. This beneficial effect is attributed to the enhanced presence of Akkermansia bacteria and improvement of the intestinal barrier.

Microscopic messengers: Extracellular vesicles shaping gastrointestinal health and disease

The field of extracellular vesicles (EVs) is advancing rapidly, and this review aims to synthesize the latest research connected to EVs and the gastrointestinal tract. We will address new and emerging roles for EVs derived from internal sources such as the pancreas and immune system and how these miniature messengers alter organismal health or the inflammatory response within the GI tract. We will examine what is known about external EVs from dietary and bacterial sources and the immense anti-inflammatory, immune-modulatory, and proliferative potential within these nano-sized information carriers. EV interactions with the intestinal and colonic epithelium and associated immune cells at homeostatic and disease states, such as necrotizing enterocolitis (NEC) and inflammatory bowel disease (IBD) will also be covered. We will discuss how EVs are being leveraged as therapeutics or for drug delivery and conclude with a series of unanswered questions in the field.

Post-stroke depression: exploring gut microbiota-mediated barrier dysfunction through immune regulation

Post-stroke depression (PSD) is one of the most common and devastating neuropsychiatric complications in stroke patients, affecting more than one-third of survivors of ischemic stroke (IS). Despite its high incidence, PSD is often overlooked or undertreated in clinical practice, and effective preventive measures and therapeutic interventions remain limited. Although the exact mechanisms of PSD are not fully understood, emerging evidence suggests that the gut microbiota plays a key role in regulating gut-brain communication. This has sparked great interest in the relationship between the microbiota-gut-brain axis (MGBA) and PSD, especially in the context of cerebral ischemia. In addition to the gut microbiota, another important factor is the gut barrier, which acts as a frontline sensor distinguishing between beneficial and harmful microbes, regulating inflammatory responses and immunomodulation. Based on this, this paper proposes a new approach, the microbiota-immune-barrier axis, which is not only closely related to the pathophysiology of IS but may also play a critical role in the occurrence and progression of PSD. This review aims to systematically analyze how the gut microbiota affects the integrity and function of the barrier after IS through inflammatory responses and immunomodulation, leading to the production or exacerbation of depressive symptoms in the context of cerebral ischemia. In addition, we will explore existing technologies that can assess the MGBA and potential therapeutic strategies for PSD, with the hope of providing new insights for future research and clinical interventions.

Environmental contamination by bisphenols: From plastic production to modulation of the intestinal morphophysiology in experimental models

Bisphenols are frequently found in a range of plastic products and have been associated with the development of diseases such as diabetes mellitus type 2 and obesity. These compounds are known as endocrine disruptors and have led to restrictions on their use due to their presence in the environment and their association with non-communicable chronic diseases. The gastrointestinal tract, being the primary site of food and water absorption, is particularly vulnerable to the effects of bisphenols. For this reason, a review of studies showing associations between bisphenols exposure and adverse effects in the gut microbiota, morphology tissue, gut permeability, and on the enteric nervous system was carried out. We have included perinatal studies and in different adult experimental models. The effects of bisphenol exposure on the gut microbiota are complex and varied. Bisphenol exposure generally leads to a decrease in microbial diversity and may impact the integrity of the intestinal barrier, resulting in elevated levels of inflammation, changes in morphological and metabolic characteristics of the gut, modifications in tight junction expression, and changes in goblet cell expression. In addition, bisphenol exposure in the perinatal phase can lead to important intestinal changes, including increased colonic inflammation and decreased colonic paracellular permeability.

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.

Intestinal mucus: the unsung hero in the battle against viral gastroenteritis

Intestinal mucus plays a crucial role in defending against enteric infections by protecting the vulnerable intestinal epithelial cells both physically and through its various constituents. Despite this, numerous gastroenteritis-causing viruses, such as rotavirus, coronavirus, adenovirus, astrovirus, calicivirus, and enterovirus, continue to pose significant threats to humans and animals. While several studies have examined the interactions between these viruses and intestinal mucus, significant gaps remain in understanding the full protective potential of intestinal mucus against these pathogens. This review aims to elucidate the protective role of intestinal mucus in viral gastroenteritis. It begins with a comprehensive literature overview of (i) intestinal mucus, (ii) enteric viruses of medical and veterinary importance, and (iii) the known interactions between various enteric viruses and intestinal mucus. Following this, a case study is presented to highlight the age-dependent blocking effect of porcine intestinal mucus against transmissible gastroenteritis virus, a porcine coronavirus. Finally, the review discusses future investigation directions to further explore the potential of intestinal mucus as a defense mechanism against viral gastroenteritis to stimulate further research in this dynamic and critical area.

Detection of chimeric alpha-defensin transcripts and peptides in mouse Paneth cells

Introduction

In mammals, Paneth cells, located in the crypts of the small intestine, produceantimicrobial peptides that serve to keep the intestinal microbiome under control. a-Defensins are the primary antimicrobial peptides produced by these cells.

Methods

We used 148 publicly available bulk RNA-seq samples on purified PCs, proteomics on enriched purified PC proteins and Defa peptide activity assays to detect all Defa transcrips, including potential chimeric transcrips.

Results

We identified 28 expressed Defa genes in mice, with up to 85% of Paneth cell RNA reads mapping to these genes. Chimeric mRNAs, involving sequences from two different Defa genes, were detected in most experiments. Despite their low abundance (less than 0.3%), mass spectrometry confirmed the presence of chimeric peptides. Synthetic versions of these peptides demonstrated antibacterial activity against multiple bacterial species.

Conclusion

We show the existence of chimeric Defa transcripts and peptides in mice that are biologically active. We propose a possible stochatic mechanism or that the activation of the UPR patway may play a role in their production.

Zebrafish as a model for human epithelial pathology

Zebrafish (Danio rerio) have emerged as an influential model for studying human epithelial pathology, particularly because of their genetic similarity to humans and their unique physiological traits. This review explores the structural and functional homology between zebrafish and human epithelial tissues in organs, such as the gastrointestinal system, liver, and kidneys. Zebrafish possess significant cellular and functional homology with mammals, which facilitates the investigation of various diseases, including inflammatory bowel disease, nonalcoholic fatty liver disease, and polycystic kidney disease. The advantages of using zebrafish as a model organism include rapid external development, ease of genetic manipulation, and advanced imaging capabilities, allowing for the real-time observation of disease processes. However, limitations exist, particularly concerning the lack of organs in zebrafish and the potential for incomplete phenocopy of human conditions. Despite these challenges, ongoing research in adult zebrafish promises to enhance our understanding of the disease mechanisms and regenerative processes. By revealing the similarities and differences in epithelial cell function and disease pathways, this review highlights the value of zebrafish as a translational model for advancing our knowledge of human health and developing targeted therapies.

Neutrophil heterogeneity and plasticity: unveiling the multifaceted roles in health and disease

Neutrophils, the most abundant circulating leukocytes, have long been recognized as key players in innate immunity and inflammation. However, recent discoveries unveil their remarkable heterogeneity and plasticity, challenging the traditional view of neutrophils as a homogeneous population with a limited functional repertoire. Advances in single-cell technologies and functional assays have revealed distinct neutrophil subsets with diverse phenotypes and functions and their ability to adapt to microenvironmental cues. This review provides a comprehensive overview of the multidimensional landscape of neutrophil heterogeneity, discussing the various axes along which diversity manifests, including maturation state, density, surface marker expression, and functional polarization. We highlight the molecular mechanisms underpinning neutrophil plasticity, focusing on the complex interplay of signaling pathways, transcriptional regulators, and epigenetic modifications that shape neutrophil responses. Furthermore, we explore the implications of neutrophil heterogeneity and plasticity in physiological processes and pathological conditions, including host defense, inflammation, tissue repair, and cancer. By integrating insights from cutting-edge research, this review aims to provide a framework for understanding the multifaceted roles of neutrophils and their potential as therapeutic targets in a wide range of diseases.

A Trade-Off Between Antimicrobial Peptide Resistance and Sensitivity to Host Immune Effectors in Staphylococcus aureus In Vivo

Antimicrobial peptides (AMPs) are essential immune effectors of multicellular organisms. Bacteria can evolve resistance to AMPs. Surprisingly, when used to challenge the yellow mealworm beetle, Tenebrio molitor, Staphylococcus aureus resistant to an abundant AMP (tenecin 1) of the very same host species did not increase host mortality or bacterial load compared to infections with wild-type S. aureus. A possible explanation is that antimicrobial resistance is costly due to the collaterally increased sensitivity of AMP-resistant strains to other immune effectors. Here, we study the sensitivity of a group of AMP-resistant S. aureus strains (resistant to tenecin 1 or a combination of tenecin 1 + 2) to other immune effectors such as phenoloxidase and other AMPs in vivo. Using RNAi-based knockdown, we investigate S. aureus survival in insect hosts lacking selected immune effectors. We find that all except one AMP-resistant strain displayed collateral sensitivity toward phenoloxidase. Some AMP-resistant strains show sensitivity to components of the yellow mealworm beetle AMP defense cocktail. Our findings are consistent with the idea that resistance to AMPs does not translate into changes in virulence because it is balanced by the collaterally increased sensitivity to other host immune effectors. AMP resistance fails to provide a net survival advantage to S. aureus in a host environment that is dominated by AMPs.

Microbial adaptive pathogenicity strategies to the host inflammatory environment

Pathogenic microorganisms can infect a variety of niches in the human body. During infection, these microbes can only persist if they adapt adequately to the dynamic host environment and the stresses imposed by the immune system. While viruses entirely rely on host cells to replicate, bacteria and fungi use their pathogenicity mechanisms for the acquisition of essential nutrients that lie under host restriction. An inappropriate deployment of pathogenicity mechanisms will alert host defence mechanisms that aim to eradicate the pathogen. Thus, these adaptations require tight regulation to guarantee nutritional access without eliciting strong immune activation. To work efficiently, the immune system relies on a complex signalling network, involving a myriad of immune mediators, some of which are quite directly associated with imminent danger for the pathogen. To manipulate the host immune system, viruses have evolved cytokine receptors and viral cytokines. However, among bacteria and fungi, selected pathogens have evolved the capacity to use these inflammatory response-specific signals to regulate their pathogenicity. In this review, we explore how bacterial and fungal pathogens can sense the immune system and use adaptive pathogenicity strategies to evade and escape host defence to ensure their persistence in the host.

Immunology and treatments of fatty liver disease

Alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are two major chronic liver diseases worldwide. The triggers for fatty liver can be derived from external sources such as adipose tissue, the gut, personal diet, and genetics, or internal sources, including immune cell responses, lipotoxicity, hepatocyte death, mitochondrial dysfunction, and extracellular vesicles. However, their pathogenesis varies to some extent. This review summarizes various immune mechanisms and therapeutic targets associated with these two types of fatty liver disease. It describes the gut-liver axis and adipose tissue-liver crosstalk, as well as the roles of different immune cells (both innate and adaptive immune cells) in fatty liver disease. Additionally, mitochondrial dysfunction, extracellular vesicles, microRNAs (miRNAs), and gastrointestinal hormones are also related to the pathogenesis of fatty liver. Understanding the pathogenesis of fatty liver and corresponding therapeutic strategies provides a new perspective for developing novel treatments for fatty liver disease.

Delving the depths of 'terra incognita' in the human intestine - the small intestinal microbiota

The small intestinal microbiota has a crucial role in gastrointestinal health, affecting digestion, immune function, bile acid homeostasis and nutrient metabolism. The challenges of accessibility at this site mean that our knowledge of the small intestinal microbiota is less developed than of the colonic or faecal microbiota. Here, we summarize the features and fluctuations of the microbiota along the small intestinal tract, focusing on humans, and discuss physicochemical factors and assessment methods, including the technical challenges of investigating the low microbial biomass of the proximal small bowel. We highlight the essential protective mechanisms of the small intestine, including motility, the paracellular barrier and mucus, and secretory immunity, to show their roles in limiting excessive exposure of host tissues to microbial metabolites. We address current knowledge gaps, particularly the variability among individuals, the effects of dysbiosis of the small intestinal microbiota on health and how different taxa in small intestinal microbiota could compensate for each other functionally.

Host-microbiota interactions in the infant gut revealed by daily faecal sample time series

Aim: This study aims to explore the interplay between host immune factors and gut microbiota in human infants in vivo using time-series daily stool samples and identify biomarkers of host-microbe interactions. Methods: 216 faecal samples collected from infants aged 5-6 or 11-12 months were analysed for gut microbiota composition, total bacterial load, and biomarkers of immune function. Results: We identified indications of microbial stimulation of eosinophil cationic protein (ECP), IgA, calprotectin (Cal), intestinal alkaline phosphatase (IAP), and Bactericidal/permeability-increasing protein (BPI) at 6 and 12 months, as well as stimulation of lipocalin 2 (LCN2), lactoferrin (LTF), and alpha-defensin-5 only at 6 months. The associations between biomarker concentrations and bacterial population growth were primarily positive at 6 months and mostly negative at 12 months, suggesting increasing host regulation of the microbiota with age. The exceptions were IAP, which was predictive of declining bacterial populations at both time points, and Cal, whose associations changed from negative at 6 months to positive at 12 months. Conclusion: There is an age-associated development in the correlation pattern between bacterial population growth and the biomarker concentrations, suggesting that host-microbe interactions change during early development. Albumin appeared as a potential marker of gut permeability, while LCN2 seemed to correlate with gut transit time. Mucin degradation appeared to decrease with age. Mucin2 and IAP emerged as potentially important regulators of the bacterial populations in the infant gut. The study demonstrates the utility of biomarker and bacteria profiling from daily stool samples for analysing in vivo associations between the immune system and the gut microbiota and provides evidence of host regulation of the microbiota in infants.

Intratumoral Fusobacterium nucleatum in Pancreatic Cancer: Current and Future Perspectives

The intratumoral microbiome plays a significant role in many cancers, such as lung, pancreatic, and colorectal cancer. Pancreatic cancer (PC) is one of the most lethal malignancies and is often diagnosed at advanced stages. Fusobacterium nucleatum (Fn), an anaerobic Gram-negative bacterium primarily residing in the oral cavity, has garnered significant attention for its emerging role in several extra-oral human diseases and, lately, in pancreatic cancer progression and prognosis. It is now recognized as oncobacterium. Fn engages in pancreatic tumorigenesis and metastasis through multifaceted mechanisms, including immune response modulation, virulence factors, control of cell proliferation, intestinal metabolite interactions, DNA damage, and epithelial-mesenchymal transition. Additionally, compelling research suggests that Fn may exert detrimental effects on cancer treatment outcomes. This paper extends the perspective to pancreatic cancer associated with Fn. The central focus is to unravel the oncogenomic changes driven by Fn in colonization, initiation, and promotion of pancreatic cancer development. The presence of Fusobacterium species can be considered a prognostic marker of PC, and it is also correlated to chemoresistance. Furthermore, this review underscores the clinical research significance of Fn as a potential tumor biomarker and therapeutic target, offering a novel outlook on its applicability in cancer detection and prognostic assessment. It is thought that given the role of Fn in tumor formation and metastasis processes via its FadA, FapA, Fap2, and RadD, new therapies for tumor treatment targeting Fn will be developed.

Investigation of Intestinal Microbes of Five Zokor Species Based on 16S rRNA Sequences

Zokor is a group of subterranean rodents that are adapted to underground life and feed on plant roots. Here, we investigated the intestinal microbes of five zokor species (Eospalax cansus, Eospalax rothschildi, Eospalax smithi, Myospalax aspalax, and Myospalax psilurus) using 16S amplicon technology combined with bioinformatics. Microbial composition analysis showed similar intestinal microbes but different proportions among five zokor species, and their dominant bacteria corresponded to those of herbivores. To visualize the relationships among samples, PCoA and PERMANOVA tests showed that the intestinal microbes of zokors are largely clustered by host species, but less so by genetics and geographical location. To find microbes that differ among species, LefSe analysis identified Lactobacillus, Muribaculaceae, Lachnospiraceae_NK4A136_group, unclassified_f_Christensenellaceae, and Desulfovibrio as biomarkers for E. cansus, E. rothschildi, E. smithi, M. aspalax, and M. psilurus, respectively. PICRUSt metagenome predictions revealed enriched microbial genes for carbohydrate and amino acid metabolism in E. cansus and E. smithi, and for cofactor and vitamin metabolism as well as glycan biosynthesis and metabolism in E. rothschildi, M. aspalax, and M. psilurus. Our results demonstrated differences in the microbial composition and functions among five zokor species, potentially related to host genetics, and host ecology including dietary habits and habitat environment. These works would provide new insight into understanding how subterranean zokors adapt to their habitats by regulating intestinal microbes.

The Role of Gut Microbiome in Irritable Bowel Syndrome: Implications for Clinical Therapeutics

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder (FGID) characterized by chronic or recurrent gastrointestinal symptoms without organic changes, and it is also a common disorder of gut-brain interaction (DGBIs).. The symptoms of IBS not only affect the quality of life for individual patients but also place a significant burden on global healthcare systems. The lack of established and universally applicable biomarkers for IBS, along with the substantial variability in symptoms and progression, presents challenges in developing effective clinical treatments. In recent years, preclinical and clinical studies have linked the pathogenesis of IBS to alterations in the composition and function of the intestinal microbiota. Within the complex microbial community of the gut, intricate metabolic and spatial interactions occur among its members and between microbes and their hosts. Amid the multifaceted pathophysiology of IBS, the role of intestinal microenvironment factors in symptom development has become more apparent. This review aims to delve into the changes in the composition and structure of the gut microbiome in individuals with IBS. It explores how diet-mediated alterations in intestinal microbes and their byproducts play a role in regulating the pathogenesis of IBS by influencing the "brain-gut" axis, intestinal barrier function, immune responses, and more. By doing so, this review seeks to lay a theoretical foundation for advancing the development of clinical therapeutics for IBS.

Immunomodulatory peptides: new therapeutic horizons for emerging and re-emerging infectious diseases

The emergence and re-emergence of multi-drug-resistant (MDR) infectious diseases have once again posed a significant global health challenge, largely attributed to the development of bacterial resistance to conventional anti-microbial treatments. To mitigate the risk of drug resistance globally, both antibiotics and immunotherapy are essential. Antimicrobial peptides (AMPs), also referred to as host defense peptides (HDPs), present a promising therapeutic alternative for treating drug-resistant infections due to their various mechanisms of action, which encompass antimicrobial and immunomodulatory effects. Many eukaryotic organisms produce HDPs as a defense mechanism, for example Purothionin from Triticum aestivum plant, Defensins, Cathelicidins, and Histatins from humans and many such peptides are currently the focus of research because of their antibacterial, antiviral and anti-fungicidal properties. This article offers a comprehensive review of the immunomodulatory activities of HDPs derived from eukaryotic organisms including humans, plants, birds, amphibians, reptiles, and marine species along with their mechanisms of action and therapeutic benefits.

Alterations in Ileal Secretory Cells of The DSS-Induced Colitis Model Mice

Inflammatory bowel disease is triggered by abnormalities in epithelial barrier function and immunological responses, although its pathogenesis is poorly understood. The dextran sodium sulphate (DSS)-induced colitis model has been used to examine inflammation in the colon. Damage to mucosa primality occurs in the large intestine and scarcely in the small intestine. To evaluate the effect on the ileum, we histologically analyzed the inflammatory and recovery phases in DSS model mice, and 40 kDa FITC-dextran was used to investigate barrier function. In the inflammatory phase, histological damage was insignificant. However, expanded crypts, hypertrophic goblet and Paneth cells, increased mucus production and secretion were observed. The cellular morphology was restored to that of the control in the recovery phase. According to in situ hybridization and lectin histochemistry, the expression of intestinal stem cell markers, secretory cell differentiation factors, and glycosylation of secretory granules in Paneth cells differed in the DSS model. DSS-treatment did not influence the barrier function in the ileum, and FITC-dextran did not diffuse via the paracellular pathway into the mucosa. However, cells incorporating FITC appeared even under normal conditions. The number of FITC-positive Paneth cells was lower in the DSS group than the control group. Our results showed morphological and functional alterations in ileal epithelial cells, especially secretory cells, in the DSS colitis model.

Gut microbiota mediated T cells regulation and autoimmune diseases

Gut microbiota regulates the immune system, the development and progression of autoimmune diseases (AIDs) and overall health. Recent studies have played a crucial part in understanding the specific role of different gut bacterial strains and their metabolites in different AIDs. Microbial signatures in AIDs are revealed by advanced sequencing and metabolomics studies. Microbes such as Faecalibacterium prausnitzii, Akkermansia muciniphila, Anaerostipes caccae, Bacteroides sp., Roseburia sp., Blautia sp., Blautia faecis, Clostridium lavalense, Christensenellaceae sp., Coprococcus sp., Firmicutes sp., Ruminococcaceae sp., Lachnospiraceae sp., Megamonas sp., Monoglobus sp., Streptococcus pneumoniae and Bifidobacterium sp. help maintain immune homeostasis; whereas, Prevotella copri, Ruminococcus gnavus, Lactobacillus salivarius, Enterococcus gallinarum, Elizabeth menigoseptica, Collinsella sp., Escherichia sp., Fusobacterium sp., Enterobacter ludwigii, Enterobacteriaceae sp., Proteobacteria, Porphyromonas gingivalis, Porphyromonas nigrescens, Dorea sp., and Clostridium sp. cause immuno-pathogenesis. A complex web of interactions is revealed by understanding the influence of gut microbiota on immune cells and various T cell subsets such as CD4+ T cells, CD8+ T cells, natural killer T cells, γδ T cells, etc. Certain AIDs, including rheumatoid arthritis, diabetes mellitus, atopic asthma, inflammatory bowel disease and non-alcoholic fatty liver disease exhibit a state of dysbiosis, characterized by alterations in microbial diversity and relative abundance of specific taxa. This review summarizes recent developments in understanding the role of certain microbiota composition in specific AIDs, and the factors affecting specific regulatory T cells through certain microbial metabolites and also focuses the potential application and therapeutic significance of gut microbiota-based interventions as novel adjunctive therapies for AIDs. Further research to determine the precise association of each gut bacterial strain in specific diseases is required.

Identification of Key Genes in Fetal Gut Development at Single-Cell Level by Exploiting Machine Learning Techniques

The study of fetal gut development is critical due to its substantial influence on immediate neonatal and long-term adult health. Current research largely focuses on microbiome colonization, gut immunity, and barrier function, alongside the impact of external factors on these phenomena. Limited research has been dedicated to the categorization of developing fetal gut cells. Our study aimed to enhance our understanding of fetal gut development by employing advanced machine-learning techniques on single-cell sequencing data. This dataset consisted of 62,849 samples, each characterized by 33,694 distinct gene features. Four feature ranking algorithms were utilized to sort features according to their significance, resulting in four feature lists. Then, these lists were fed into an incremental feature selection method to extract essential genes, classification rules, and build efficient classifiers. Several important genes were recognized by multiple feature ranking algorithms, such as FGG, MDK, RBP1, RBP2, IGFBP7, and SPON2. These features were key in differentiating specific developing intestinal cells, including epithelial, immune, mesenchymal, and vasculature cells of the colon, duo jejunum, and ileum cells. The classification rules showed special gene expression patterns on some intestinal cell types and the efficient classifiers can be useful tools for identifying intestinal cells.

Targeting gut microbiota as a therapeutic target in T2DM: A review of multi-target interactions of probiotics, prebiotics, postbiotics, and synbiotics with the intestinal barrier

The global epidemic of type 2 diabetes mellitus (T2DM) imposes a substantial burden on public health and healthcare expenditures, thereby driving the pursuit of cost-effective preventive and therapeutic strategies. Emerging evidence suggests a potential association between dysbiosis of gut microbiota and its metabolites with T2DM, indicating that targeted interventions aimed at modulating gut microbiota may represent a promising therapeutic approach for the management of T2DM. In this review, we concentrated on the multifaceted interactions between the gut microbiota and the intestinal barrier in the context of T2DM. We systematically summarized that the imbalance of beneficial gut microbiota and its metabolites may constitute a viable therapeutic approach for the management of T2DM. Meanwhile, the mechanisms by which gut microbiota interventions, such as probiotics, prebiotics, postbiotics, and synbiotics, synergistically improve insulin resistance in T2DM are summarized. These mechanisms include the restoration of gut microbiota structure, upregulation of intestinal epithelial cell proliferation and differentiation, enhancement of tight junction protein expression, promotion of mucin secretion by goblet cells, and the immunosuppressive functions of regulatory T cells (Treg) and M2 macrophages. Collectively, these actions contribute to the amelioration of the body's metabolic inflammatory status. Our objective is to furnish evidence that supports the clinical application of probiotics, prebiotics, and postbiotics in the management of T2DM.

Development of a deep learning algorithm for Paneth cell density quantification for inflammatory bowel disease

BACKGROUND

Alterations in ileal Paneth cell (PC) density have been described in gut inflammatory diseases such as Crohn's disease (CD) and could be used as a biomarker for disease prognosis. However, quantifying PCs is time-intensive, a barrier for clinical workflow. Deep learning (DL) has transformed the development of robust and accurate tools for complex image evaluation. Our aim was to use DL to quantify PCs for use as a quantitative biomarker.

METHODS

A retrospective cohort of whole slide images (WSI) of ileal tissue samples from patients with/without inflammatory bowel disease (IBD) was used for the study. A pathologist-annotated training set of WSI were used to train a U-net two-stage DL model to quantify PC number, crypt number, and PC density. For validation, a cohort of 48 WSIs were manually quantified by study pathologists and compared to the DL algorithm, using root mean square error (RMSE) and the coefficient of determination (r2) as metrics. To test the value of PC quantification as a biomarker, resection specimens from patients with CD (n = 142) and without IBD (n = 48) patients were analysed with the DL model. Finally, we compared time to disease recurrence in patients with CD with low versus high DL-quantified PC density using Log-rank test.

FINDINGS

Initial one-stage DL model showed moderate accuracy in predicting PC density in cross-validation tests (RMSE = 1.880, r2 = 0.641), but adding a second stage significantly improved accuracy (RMSE = 0.802, r2 = 0.748). In the validation of the two-stage model compared to expert pathologists, the algorithm showed good performance up to RMSE = 1.148, r2 = 0.708. The retrospective cross-sectional cohort had mean ages of 62.1 years in the patients without IBD and 38.6 years for the patients with CD. In the non-IBD cohort, 43.75% of the patients were male, compared to 49.3% of the patients with CD. Analysis by the DL model showed significantly higher PC density in non-IBD controls compared to the patients with CD (4.04 versus 2.99 PC/crypt). Finally, the algorithm quantification of PCs density in patients with CD showed patients with the lowest 25% PC density (Quartile 1) have significantly shorter recurrence-free interval (p = 0.0399).

INTERPRETATION

The current model performance demonstrates the feasibility of developing a DL-based tool to measure PC density as a predictive biomarker for future clinical practice.

FUNDING

This study was funded by the National Institutes of Health (NIH).

Antiviral and antibacterial peptides: Mechanisms of action

Antimicrobial peptides (AMPs) present promising alternatives for addressing bacterial and viral multidrug resistance due to their distinctive properties. Understanding the mechanisms of these compounds is essential for achieving this objective. Therefore, this comprehensive review aims to highlight primary natural sources of AMPs and elucidate various aspects of the modes of action of antiviral and antibacterial peptides (ABPs). It emphasizes that antiviral peptides (AVPs) can disrupt the replication cycle of both enveloped and non-enveloped viruses at several stages, including pre-fusion, fusion, and post-entry into the host cell. Additionally, the review discusses the inhibitory effects of ABPs on bacterial growth, outlining their extracellular actions as well as their intracellular activities following membrane translocation. Factors such as structure, size, electric charge, environmental factors, degrading enzymes, and microbial resistance against AMPs can affect the function of AMPs.

Review of the Relationships Between Human Gut Microbiome, Diet, and Obesity

Obesity is a complex disease that increases the risk of other pathologies. Its prevention and long-term weight loss maintenance are problematic. Gut microbiome is considered a potential obesity modulator. The objective of the present study was to summarize recent findings regarding the relationships between obesity, gut microbiota, and diet (vegetable/animal proteins, high-fat diets, restriction of carbohydrates), with an emphasis on dietary fiber and resistant starch. The composition of the human gut microbiome and the methods of its quantification are described. Products of the gut microbiome metabolism, such as short-chain fatty acids and secondary bile acids, and their effects on the gut microbiota, intestinal barrier function and immune homeostasis are discussed in the context of obesity. The importance of dietary fiber and resistant starch is emphasized as far as effects of the host diet on the composition and function of the gut microbiome are concerned. The complex relationships between human gut microbiome and obesity are finally summarized.

Impact of probiotics-derived extracellular vesicles on livestock gut barrier function

Probiotic extracellular vesicles (pEVs) are biologically active nanoparticle structures that can regulate the intestinal tract through direct or indirect mechanisms. They enhance the intestinal barrier function in livestock and poultry and help alleviate intestinal diseases. The specific effects of pEVs depend on their internal functional components, including nucleic acids, proteins, lipids, and other substances. This paper presents a narrative review of the impact of pEVs on the intestinal barrier across various segments of the intestinal tract, exploring their mechanisms of action while highlighting the limitations of current research. Investigating the mechanisms through which probiotics operate via pEVs could deepen our understanding and provide a theoretical foundation for their application in livestock production.

Sulfated fucans from algae Saccharina japonica promotes intestinal stem cell-mediated intestinal development in juvenile mouse by modulating the gut microbiota

Intestinal development has a crucial role in the absorption of nutrients and the ability to resist infections in the early stages of life. This study utilized a 3-week-old C57BL/6 mice model to evaluate the beneficial impacts of sulfated fucans from Saccharina japonica (SJ-FUC) on the growth and development of the intestines. SJ-FUC enhanced the dimensions of the intestine, specifically the length, height of villi, and depth of the crypts. Additionally, it raised the mRNA expression of ZO-1 and Occludin, hence enhancing the structural integrity of the intestinal epithelium. SJ-FUC significantly increased mRNA expression of Lyz1, Muc2, and Math1, which resulted in the promotion of intestinal epithelial development. Furthermore, SJ-FUC augmented the mRNA levels of the ISC markers (Lgr5, Olfm4, and Ascl2). Our further research uncovered that SJ-FUC has a positive impact on the growth of beneficial bacteria, such as Akkermansia, Dubosiella, and Lactobacillus, which in turn promotes epithelial development of the intestine. In summary, our research indicates that SJ-FUC has a beneficial impact on the growth of the intestines in young mice. This is achieved by enhancing the stemness of intestinal stem cells (ISCs) and promoting the formation of the intestinal epithelium through the regulation of gut bacteria.

Gastrointestinal Biofilms: Endoscopic Detection, Disease Relevance, and Therapeutic Strategies

Gastrointestinal biofilms are matrix-enclosed, highly heterogenic and spatially organized polymicrobial communities that can cover large areas in the gastrointestinal tract. Gut microbiota dysbiosis, mucus disruption, and epithelial invasion are associated with pathogenic biofilms that have been linked to gastrointestinal disorders such as irritable bowel syndrome, inflammatory bowel diseases, gastric cancer, and colorectal cancer. Intestinal biofilms are highly prevalent in ulcerative colitis and irritable bowel syndrome patients, and most endoscopists will have observed such biofilms during colonoscopy, maybe without appreciating their biological and clinical importance. Gut biofilms have a protective extracellular matrix that renders them challenging to treat, and effective therapies are yet to be developed. This review covers gastrointestinal biofilm formation, growth, appearance and detection, biofilm architecture and signalling, human host defence mechanisms, disease and clinical relevance of biofilms, therapeutic approaches, and future perspectives. Critical knowledge gaps and open research questions regarding the biofilm's exact pathophysiological relevance and key hurdles in translating therapeutic advances into the clinic are discussed. Taken together, this review summarizes the status quo in gut biofilm research and provides perspectives and guidance for future research and therapeutic strategies.

The Role of Iron in Intestinal Mucus: Perspectives from Both the Host and Gut Microbiota

Although research on the role of iron in host immunity has a history spanning decades, it is only relatively recently that attention has been directed toward the biological effects of iron on the intestinal mucus layer, prompted by an evolving understanding of the role of this material in immune defense. The mucus layer, secreted by intestinal goblet cells, covers the intestinal epithelium, and given its unique location, interactions between the host and gut microbiota, as well as among constituent microbiota, occur frequently within the mucus layer. Iron, as an essential nutrient for the vast majority of life forms, regulates immune responses from both the host and microbial perspectives. In this review, we summarize the iron metabolism of both the host and gut microbiota and describe how iron contributes to intestinal mucosal homeostasis via the intestinal mucus layer with respect to both host and constituent gut microbiota. The findings described herein offer a new perspective on iron-mediated intestinal mucosal barrier function.

Novel structural determinants and bacterial death-related regulatory effects of the scorpion defensin BmKDfsin4 against gram-positive bacteria

Numerous defensins constitute a family of cationic antimicrobial peptides with high degrees of sequence variability, and in-depth characterization of their structural basis and antibacterial mechanisms remains limited. Here, a representative scorpion defensin, BmKDfsin4, with two distinct hydrophobic and basic residue clusters, was extensively investigated. The hydrophobic residue cluster, formed by Phe2, Pro5, Phe6, Phe28 and Leu29 residues, strongly influences the antibacterial activity of BmKDfsin4 against Gram-positive bacteria. Compared with the three scattered Lys13, Lys30 and Arg32 residues, the basic residue cluster, consisting of the Arg19, Arg20, Arg21 and Arg37 residues, played a less important role. The synergistic interaction between the basic residue cluster and Arg32 significantly affected BmKDfsin4 function. The bacterial growth inhibition by BmKDfsin4 was associated with regulating expression levels of cell division-related genes, cell wall synthesis-related genes and bacterial autolysis-related genes rather than destroying the bacterial cell membrane. The coincubation of BmKDfsin4 with the bacterial strains induced gradual changes in the bacterial surface from a rough and thin surface to a noticeably wrinkled surface together with abundant white spots and even complete cavities within the bacteria. These findings revealed novel structural determinants and bacterial death-related regulatory effects of the defensin BmKDfsin4 and highlighted diverse antibacterial mechanisms of defensins.

Role of mechanosensitive channel Piezo1 protein in intestinal inflammation regulation: A potential target

The intestine is a hollow tract that primarily transports and digests food. It often encounters mechanical forces and exotic threats, resulting in increased intestinal inflammation attributed to the consistent threat of foreign pathogens. Piezo1, a mechanosensitive ion channel, is distributed broadly and abundantly in the intestinal tissue. It transduces mechanical signals into electrochemical signals and participates in many critical life activities, such as proliferation, differentiation, cell apoptosis, immune cell activation, and migration. Its effect on inflammation has been discussed in detail in systems, such as musculoskeletal (osteoarthritis) and cardiac (myocarditis), but the effects on intestinal inflammation remain unelucidated. Piezo1 regulates mucosal layer and epithelial barrier homeostasis during the complex intestinal handling of foreign antigens and tissue trauma. It initiates and spreads immune responses and causes distant effects of inflammation in the vascular and lymphatic systems, but reports of the effects of Piezo1 in intestinal inflammation are scarce. Therefore, this study aimed to discuss the role of Piezo1 in intestinal inflammation and explore novel therapeutic targets.

Impaired activation of succinate-induced type 2 immunity and secretory cell production in the small intestines of Ptk6-/- male mice

Protein tyrosine kinase 6 (PTK6) is an intracellular tyrosine kinase that is distantly related to the SRC family of tyrosine kinases. It is expressed in epithelial linings and regulates regeneration and repair of the intestinal epithelium. Analysis of publicly available datasets showed Ptk6 is upregulated in tuft cells upon activation of type 2 immunity. We found that disruption of Ptk6 influences gene expression involved in intestinal immune responses. Administration of succinate, which mimics infection and activates tuft cells, revealed PTK6-dependent activation of innate immune responses in male but not female mice. In contrast to all wild type and Ptk6-/- female mice, Ptk6-/- male mice do not activate innate immunity or upregulate differentiation of the tuft and goblet secretory cell lineages following succinate treatment. Mechanistically, we found that PTK6 regulates Il25 and Irag2, genes that are required for tuft cell effector functions and activation of type 2 innate immunity, in organoids derived from intestines of male but not female mice. In patients with Crohn's disease, PTK6 is upregulated in tuft cells in noninflamed regions of intestine. These data highlight roles for PTK6 in contributing to sex differences in intestinal innate immunity and provide new insights into the regulation of IL-25.

Manipulation of feeding patterns in high fat diet fed rats improves microbiota composition dynamics, inflammation and gut-brain signaling

Chronic consumption of high fat (HF) diets has been shown to increase meal size and meal frequency in rodents, resulting in overeating. Reducing meal frequency and establishing periods of fasting, independently of caloric intake, may improve obesity-associated metabolic disorders. Additionally, diet-driven changes in microbiota composition have been shown to play a critical role in the development and maintenance of metabolic disorders. In this study, we used a pair-feeding paradigm to reduce meal frequency and snacking episodes while maintaining overall intake and body weight in HF fed rats. We hypothesized that manipulation of feeding patterns would improve microbiota composition and metabolic outcomes. Male Wistar rats were placed in three groups consuming either a HF, low fat diet (LF, matched for sugar), or pair-fed HF diet for 7 weeks (n = 11-12/group). Pair-fed animals received the same amount of food consumed by the HF fed group once daily before dark onset (HF-PF). Rats underwent oral glucose tolerance and gut peptide cholecystokinin sensitivity tests. Bacterial DNA was extracted from the feces collected during both dark and light cycles and sequenced via Illumina MiSeq sequencing of the 16S V4 region. Our pair-feeding paradigm reduced meal numbers, especially small meals in the inactive phase, without changing total caloric intake. This shift in feeding patterns reduced relative abundances of obesity-associated bacteria and maintained circadian fluctuations in microbial abundances. These changes were associated with improved gastrointestinal (GI) function, reduced inflammation, and improved glucose tolerance and gut to brain signaling. We concluded from these data that targeting snacking may help improve metabolic outcomes, independently of energy content of the diet and hyperphagia.

[Immunological foundations of neurological diseases]

BACKGROUND

Neurodegenerative diseases represent an increasing challenge in ageing societies, as only limited treatment options are currently available.

OBJECTIVE

New research methods and interdisciplinary interaction of different disciplines have changed the way neurological disorders are viewed and paved the way for the comparatively new field of neuroimmunology, which was established in the early 1980s. Starting from neurological autoimmune diseases, such as multiple sclerosis, knowledge about the involvement of immunological processes in other contexts, such as stroke or traumatic brain injury, has been significantly expanded in recent years.

MATERIAL AND METHODS

This review article provides an overview of the role of the immune system and the resulting potential for novel treatment approaches.

RESULTS

The immune system plays a central role in fighting infections but is also able to react to the body's own signals under sterile conditions and cause inflammation and subsequent adaptive immune responses through the release of immune mediators and the recruitment and differentiation of certain immune cell types. This can be beneficial in initiating healing processes; however, chronic inflammatory conditions usually have destructive consequences for the tissue and the organism and must be interrupted.

CONCLUSION

It is now known that different cells of the immune system play an important role in neurological diseases. Regulatory mechanisms, which are mediated by regulatory T cells or Th2 cells, are usually associated with a good prognosis, whereas inflammatory processes and polarization towards Th1 or Th17 have a destructive character. Novel immunomodulators, which are also increasingly being used in cancer treatment, can now be used in a tissue-specific manner and therefore offer great potential for use in neurological diseases.

Western diet reduces small intestinal intraepithelial lymphocytes via FXR-Interferon pathway

The prevalence of obesity in the United States has continued to increase over the past several decades. Understanding how diet-induced obesity modulates mucosal immunity is of clinical relevance. We previously showed that consumption of a high fat, high sugar "Western" diet (WD) reduces the density and function of small intestinal Paneth cells, a small intestinal epithelial cell type with innate immune function. We hypothesized that obesity could also result in repressed gut adaptive immunity. Using small intestinal intraepithelial lymphocytes (IEL) as a readout, we found that in non-inflammatory bowel disease (IBD) subjects, high body mass index correlated with reduced IEL density. We recapitulated this in wild type (WT) mice fed with WD. A 4-week WD consumption was able to reduce IEL but not splenic, blood, or bone marrow lymphocytes, and the effect was reversible after another 2 weeks of standard diet (SD) washout. Importantly, WD-associated IEL reduction was not dependent on the presence of gut microbiota, as WD-fed germ-free mice also showed IEL reduction. We further found that WD-mediated Farnesoid X Receptor (FXR) activation in the gut triggered IEL reduction, and this was partially mediated by intestinal phagocytes. Activated FXR signaling stimulated phagocytes to secrete type I IFN, and inhibition of either FXR or type I IFN signaling within the phagocytes prevented WD-mediated IEL loss. Therefore, WD consumption represses both innate and adaptive immunity in the gut. These findings have significant clinical implications in the understanding of how diet modulates mucosal immunity.

Understanding the Dynamics of Human Defensin Antimicrobial Peptides: Pathogen Resistance and Commensal Induction

Antimicrobial peptides (AMPs), also known as host defense peptides, are petite molecules with inherent microbicidal properties that are synthesized by the host's innate immune response. These peptides serve as an initial barrier against pathogenic microorganisms, effectively eliminating them. Human defensin (HD) AMPs represent a prominent group of peptides involved in the innate immune response of humans. These peptides are primarily produced by neutrophils and epithelial cells, serving as a crucial defense mechanism against invading pathogens. The extensive research conducted has focused on the broad spectrum of antimicrobial activities and multifaceted immunomodulatory functions exhibited by human defensin AMPs. During the process of co-evolution between hosts and bacterial pathogens, bacteria have developed the ability to recognize and develop an adaptive response to AMPs to counterattack their bactericidal activity by different antibiotic-resistant mechanisms. However, numerous non-pathogenic commensal bacteria elicit the upregulation of defensins as a means to surmount the resistance mechanisms implemented by pathogens. The precise mechanism underlying the induction of HD by commensal organisms remains to be fully understood. This review summarizes the most recent research on the expression of human defensin by pathogens and discusses the various defense mechanisms used by pathogens to counter host AMP production. We also mention recent developments in the commensal induction of defensin AMPs. A better knowledge of the pathogens' defensin AMP resistance mechanisms and commensals' induction of AMP expression may shed light on the creation of fresh antibacterial tactics to get rid of bacterial infection.

Lung antimicrobial proteins and peptides: from host defense to therapeutic strategies

Representing severe morbidity and mortality globally, respiratory infections associated with chronic respiratory diseases, including complicated pneumonia, asthma, interstitial lung disease, and chronic obstructive pulmonary disease, are a major public health concern. Lung health and the prevention of pulmonary disease rely on the mechanisms of airway surface fluid secretion, mucociliary clearance, and adequate immune response to eradicate inhaled pathogens and particulate matter from the environment. The antimicrobial proteins and peptides contribute to maintaining an antimicrobial milieu in human lungs to eliminate pathogens and prevent them from causing pulmonary diseases. The predominant antimicrobial molecules of the lung environment include human α- and β-defensins and cathelicidins, among numerous other host defense molecules with antimicrobial and antibiofilm activity such as PLUNC (palate, lung, and nasal epithelium clone) family proteins, elafin, collectins, lactoferrin, lysozymes, mucins, secretory leukocyte proteinase inhibitor, surfactant proteins SP-A and SP-D, and RNases. It has been demonstrated that changes in antimicrobial molecule expression levels are associated with regulating inflammation, potentiating exacerbations, pathological changes, and modifications in chronic lung disease severity. Antimicrobial molecules also display roles in both anticancer and tumorigenic effects. Lung antimicrobial proteins and peptides are promising alternative therapeutics for treating and preventing multidrug-resistant bacterial infections and anticancer therapies.

Early-Life Gut Microbiota: A Possible Link Between Maternal Exposure to Non-Nutritive Sweeteners and Metabolic Syndrome in Offspring

Metabolic syndrome (MetS) is recognized as a group of metabolic abnormalities, characterized by clustered interconnected traits that elevate the risks of obesity, cardiovascular and atherosclerotic diseases, hyperlipidemia, and type 2 diabetes mellitus. Non-nutritive sweeteners (NNS) are commonly consumed by those with imbalanced calorie intake, especially in the perinatal period. In the past, accumulating evidence showed the transgenerational and mediated roles of human microbiota in the development of early-life MetS. Maternal exposure to NNS has been recognized as a risk factor for filial metabolic disturbance through various mechanisms, among which gut microbiota and derived metabolites function as nodes linking NNS and MetS in early life. Despite the widespread consumption of NNS, there remain growing concerns about their transgenerational impact on metabolic health. There is growing evidence of NNS being implicated in the development of metabolic abnormalities. Intricate complexities exist and a comprehensive understanding of how the gut microbiota interacts with mechanisms related to maternal NNS intake and disrupts metabolic homeostasis of offspring is critical to realize its full potential in preventing early-life MetS. This review aims to elucidate the effects of early-life gut microbiota and links to maternal NNS exposure and imbalanced offspring metabolic homeostasis and discusses potential perspectives and challenges, which may provide enlightenment and understanding into optimal perinatal nutritional management.

The gut homeostasis-immune system axis: novel insights into rheumatoid arthritis pathogenesis and treatment

Rheumatoid arthritis is a widely prevalent autoimmune bone disease that imposes a significant burden on global healthcare systems due to its increasing incidence. In recent years, attention has focused on the interaction between gut homeostasis and the immune system, particularly in relation to bone health. Dysbiosis, which refers to an imbalance in the composition and function of the gut microbiota, has been shown to drive immune dysregulation through mechanisms such as the release of pro-inflammatory metabolites, increased gut permeability, and impaired regulatory T cell function. These factors collectively contribute to immune system imbalance, promoting the onset and progression of Rheumatoid arthritis. Dysbiosis induces both local and systemic inflammatory responses, activating key pro-inflammatory cytokines such as tumor necrosis factor-alpha, Interleukin-6, and Interleukin-17, which exacerbate joint inflammation and damage. Investigating the complex interactions between gut homeostasis and immune regulation in the context of Rheumatoid arthritis pathogenesis holds promise for identifying new therapeutic targets, revealing novel mechanisms of disease progression, and offering innovative strategies for clinical treatment.