From birth to death: The hardworking life of Paneth cell in the small intestine

A New Strategy for Dietary Nutrition to Improve Intestinal Homeostasis in Diarrheal Irritable Bowel Syndrome: A Perspective on Intestinal Flora and Intestinal Epithelial Interaction

BACKGROUND AND OBJECTIVES

Although a reasonable diet is essential for promoting human health, precise nutritional regulation presents a challenge for different physiological conditions. Irritable Bowel Syndrome (IBS) is characterized by recurrent abdominal pain and abnormal bowel habits, and diarrheal IBS (IBS-D) is the most common, seriously affecting patients' quality of life. Therefore, the implementation of precise nutritional interventions for IBS-D has become an urgent challenge in the fields of nutrition and food science. IBS-D intestinal homeostatic imbalance involves intestinal flora disorganization and impaired intestinal epithelial barrier function. A familiar interaction is evident between intestinal flora and intestinal epithelial cells (IECs), which together maintain intestinal homeostasis and health. Dietary patterns, such as the Mediterranean diet, have been shown to regulate gut flora, which in turn improves the body's health by influencing the immune system, the hormonal system, and other metabolic pathways.

METHODS

This review summarized the relationship between intestinal flora, IECs, and IBS-D. It analyzed the mechanism behind IBS-D intestinal homeostatic imbalance by examining the interactions between intestinal flora and IECs, and proposed a precise dietary nutrient intervention strategy.

RESULTS AND CONCLUSION

This increases the understanding of the IBS-D-targeted regulation pathways and provides guidance for designing related nutritional intervention strategies.

Nur77 as a novel regulator of Paneth cell differentiation and function

Serving as a part of intestinal innate immunity, Paneth cells play an important role in intestinal homeostasis maintenance via their multiple functions. However, the regulation of Paneth cells has been proven to be complex and diverse. Here, we identified nuclear receptor Nur77 as a novel regulator of Paneth cell differentiation and function. Nur77 deficiency led to the loss of Paneth cells in murine ileal crypts. Intestinal tissues or organoids with Nur77 deficiency exhibited the impaired intestinal stem cell niche and failed to enhance antimicrobial peptide expression after Paneth cell degranulation. The defects in Paneth cells and antimicrobial peptides in Nur7-/- mice led to intestinal microbiota disorders. Nur77 deficiency rendered postnatal mice susceptible to necrotizing enterocolitis. Mechanistically, Nur77 transcriptionally inhibited Dact1 expression to activate Wnt signaling activity, thus promoting Paneth cell differentiation and function. Taken together, our data suggest the regulatory role of Nur77 in Paneth cell differentiation and function and reveal a novel Dact1-mediated Wnt inhibition mechanism in Paneth cell development.

LPA5-Dependent signaling regulates regeneration of the intestinal epithelium following irradiation

Lysophosphatidic acid (LPA) is a bioactive lipid molecule that regulates a wide array of cellular functions, including proliferation, differentiation, and survival, via activation of cognate receptors. The LPA5 receptor is highly expressed in the intestinal epithelium, but its function in restoring intestinal epithelial integrity following injury has not been examined. Here, we use a radiation-induced injury model to study the role of LPA5 in regulating intestinal epithelial regeneration. Control mice (Lpar5f/f) and mice with an inducible, epithelial cell-specific deletion of Lpar5 in the small intestine (Lpar5IECKO) were subjected to 10 Gy total body X-ray irradiation and analyzed during recovery. Repair of the intestinal mucosa was delayed in Lpar5IECKO mice with reduced epithelial proliferation and increased crypt cell apoptosis. These effects were accompanied by reduced numbers of OLFM4+ intestinal stem cells (ISCs). The effects of LPA5 on ISCs were corroborated by studies using organoids derived from Lgr5-lineage tracking reporter mice with deletion of Lpar5 in Lgr5+-stem cells (Lgr5Cont or Lgr5ΔLpar5). Irradiation of organoids resulted in fewer numbers of Lgr5ΔLpar5 organoids retaining Lgr5+-derived progenitor cells compared with Lgr5Cont organoids. Finally, we observed that impaired regeneration in Lpar5IECKO mice was associated with reduced numbers of Paneth cells and decreased expression of Yes-associated protein (YAP), a critical factor for intestinal epithelial repair. Our study highlights a novel role for LPA5 in regeneration of the intestinal epithelium following irradiation and its effect on the maintenance of Paneth cells that support the stem cell niche.NEW & NOTEWORTHY We used mice lacking expression of the lysophosphatidic acid receptor 5 (LPA5) in intestinal epithelial cells and intestinal organoids to show that the LPA5 receptor protects intestinal stem cells and progenitors from radiation-induced injury. We show that LPA5 induces YAP signaling and regulates Paneth cells.

Efferocytosis by macrophages in physiological and pathological conditions: regulatory pathways and molecular mechanisms

Efferocytosis is defined as the highly effective phagocytic removal of apoptotic cells (ACs) by professional or non-professional phagocytes. Tissue-resident professional phagocytes ("efferocytes"), such as macrophages, have high phagocytic capacity and are crucial to resolve inflammation and aid in homeostasis. Recently, numerous exciting discoveries have revealed divergent (and even diametrically opposite) findings regarding metabolic immune reprogramming associated with efferocytosis by macrophages. In this review, we highlight the key metabolites involved in the three phases of efferocytosis and immune reprogramming of macrophages under physiological and pathological conditions. The next decade is expected to yield further breakthroughs in the regulatory pathways and molecular mechanisms connecting immunological outcomes to metabolic cues as well as avenues for "personalized" therapeutic intervention.

The intersection between host-pathogen interactions and metabolism during Vibrio cholerae infection

Vibrio cholerae (V. cholerae), the etiological agent of cholera, uses cholera toxin (CT) to cause severe diarrheal disease. Cholera is still a significant cause of mortality worldwide with about half of all cholera cases and deaths occurring in children under five. Owing to the lack of cost-effective vaccination and poor vaccine efficacy in children, there is a need for alternative preventative and therapeutic strategies. Recent advances in our knowledge of the interplay between CT-induced disease and host-pathogen metabolism have opened the door for investigating how modulation of intestinal metabolism by V. cholerae during disease impacts host intestinal immunity, the gut microbiota, and pathogen-phage interactions. In this review article, we examine recent progress in our understanding of host-pathogen interactions during V. cholerae infection and discuss future work deciphering how modulation of gut metabolism during cholera intersects these processes to enable successful fecal-oral transmission of the pathogen.

The importance of the gut microbiome and its signals for a healthy nervous system and the multifaceted mechanisms of neuropsychiatric disorders

Increasing evidence links the gut microbiome and the nervous system in health and disease. This narrative review discusses current views on the interaction between the gut microbiota, the intestinal epithelium, and the brain, and provides an overview of the communication routes and signals of the bidirectional interactions between gut microbiota and the brain, including circulatory, immunological, neuroanatomical, and neuroendocrine pathways. Similarities and differences in healthy gut microbiota in humans and mice exist that are relevant for the translational gap between non-human model systems and patients. There is an increasing spectrum of metabolites and neurotransmitters that are released and/or modulated by the gut microbiota in both homeostatic and pathological conditions. Dysbiotic disruptions occur as consequences of critical illnesses such as cancer, cardiovascular and chronic kidney disease but also neurological, mental, and pain disorders, as well as ischemic and traumatic brain injury. Changes in the gut microbiota (dysbiosis) and a concomitant imbalance in the release of mediators may be cause or consequence of diseases of the central nervous system and are increasingly emerging as critical links to the disruption of healthy physiological function, alterations in nutrition intake, exposure to hypoxic conditions and others, observed in brain disorders. Despite the generally accepted importance of the gut microbiome, the bidirectional communication routes between brain and gut are not fully understood. Elucidating these routes and signaling pathways in more detail offers novel mechanistic insight into the pathophysiology and multifaceted aspects of brain disorders.

Porcine β-defensin-2 alleviates aflatoxin B1 induced intestinal mucosal damage via ROS-Erk1/2 signaling pathway

Aflatoxin B1 (AFB1) is a highly toxic fungal toxin that causes severe damage to animal intestines. Porcine beta-defensin-2 (pBD-2) is a well-studied antimicrobial peptide in pigs that can protect animal intestines and improve productivity. This study aimed to investigate the molecular mechanisms of pBD-2 in alleviating AFB1-induced oxidative stress and intestinal mucosal damage using porcine intestinal epithelial cells (IPEC-J2 cells) and Kunming (KM) mice. The maximum destructive concentration of AFB1 for IPEC-J2 cells and the optimal therapeutic concentration of pBD-2 were determined by CCK-8 and RT-qPCR. We then investigated the oxidative stress and intestinal damage induced by AFB1 and the alleviating effect of pBD-2 by detecting changes of reactive oxygen species (ROS), inflammatory cytokines, tight junction proteins (TJPs) and mucin. Finally, the molecular mechanism of pBD-2 mitigates AFB1-induced oxidative stress and intestinal mucosal damage were explored by adding ROS and Erk1/2 pathway inhibitors to comparative analysis. In vivo, the therapeutic effect of pBD-2 on AFB1-induced intestinal damage was analyzed from aspects such as average daily gain (ADG), pathological damage, inflammation, and mucosal barrier in KM mice. The study found that low doses of pBD-2 promoted cell proliferation and prevented AFB1-induced cell death, and pBD-2 significantly restored the feed conversion rate and ADG of KM mice reduced by long-term exposed AFB1. Increasing the intracellular ROS and the expression and phosphorylation of Erk1/2, AFB1 promoted inflammation by altering inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8, and disrupted the mucosal barrier by interfering with Claudin-3, Occludin, and MUC2, while pBD-2 significantly reduced ROS and decreased the expression and phosphorylation of Erk1/2 to restored their expression to alleviate AFB1-induced oxidative stress and intestinal mucosal damage in IPEC-J2 cells and the small intestine of mice.

Gut commensal bacteria exacerbate toxoplasmosis associated with TgSheepCHn5 (ToxoDB#2) and TgRedpandaCHn1 (ToxoDB#20) through Th1 immune response

Oral infection of mice with several strains of Toxoplasma gondii results in intestinal pathological lesions, which contributes to the invasion of this parasite. However, the exact mechanism is unclear, and only a few strains have been explored. Here, T. gondii TgSheepCHn5 and TgRedpandaCHn1 strains from sheep and red panda were evaluated. The TgSheepCHn5 and TgRedpandaCHn1 strains induced intestinal lesions, loss of Paneth cells, and gut commensal bacteria dysbiosis in Swiss Webster mice. The lesions and loss of Paneth cells were dependent on IFN-γ and gut commensal bacteria during T. gondii infection. Deleting IFN-γ or gut commensal bacteria suppressed the Th1 immune response, alleviated the lesions and parasite loading, and upregulated the number of Paneth cells. Loss of IFN-γ production accelerated mice death, whereas the deletion of gut commensal bacteria enhanced the survival time of the host. The Th1 cell immune responses have positive and negative effects on toxoplasmosis, resistance to T. gondii infection, and acceleration intestine lesions. Adjustment of Th1 cell responses and gut commensal bacteria may be effective treatments for toxoplasmosis.

Homemade: building the structure of the neurogenic niche

Neural stem/progenitor cells live in an intricate cellular environment, the neurogenic niche, which supports their function and enables neurogenesis. The niche is made of a diversity of cell types, including neurons, glia and the vasculature, which are able to signal to and are structurally organised around neural stem/progenitor cells. While the focus has been on how individual cell types signal to and influence the behaviour of neural stem/progenitor cells, very little is actually known on how the niche is assembled during development from multiple cellular origins, and on the role of the resulting topology on these cells. This review proposes to draw a state-of-the art picture of this emerging field of research, with the aim to expose our knowledge on niche architecture and formation from different animal models (mouse, zebrafish and fruit fly). We will span its multiple aspects, from the existence and importance of local, adhesive interactions to the potential emergence of larger-scale topological properties through the careful assembly of diverse cellular and acellular components.

Paneth cells protect intestinal stem cell niche to alleviate deoxynivalenol-induced intestinal injury

Deoxynivalenol (DON) is a common toxin in grains and feeds, and DON exposure triggers severe small intestinal injury and inflammation, which harms the health of humans and livestock. DON treatment leads to a decrease in Paneth cells, whereas the role of Paneth cells in DON-induced intestinal injury is poorly understood. We utilized dithizone (40 mg/kg) to keep murine Paneth cell number at a low level. The results showed that dithizone-mediated long-term disruption of Paneth cells aggravated intestinal injury, intestinal stem cell (ISC) loss, and microbiota disorder in DON (2 mg/kg)-treated mice. Unexpectedly, the number of goblet cells and proliferative cells was boosted in mice treated with dithizone and DON. After dithizone and DON treatments, the Firmicutes/Bacteroidetes (F/B) ratio was reduced, and the increased abundance of Dubosiella and the decreased abundance of Lactobacillus were observed in mice. The functional recovery of Paneth cells by lysozyme (200 U/day) supplementation improved intestinal injury and ISC loss in mice after DON challenge. In addition, lysozyme also promoted the growth and ISC activity of intestinal organoids. Taken together, these results demonstrate the protective role of Paneth cells in DON-induced intestinal injury. Our study raises a novel target, Paneth cell, for the treatment of DON exposure.

Cellular evidence of mucus cell immunological and differentiation characteristics in allogeneic crucian carp intestinal lamina propria

The allogeneic crucian carp is an important fish farm animal with a very different digestive system structure from that of mammals. The lamina propria of the fish intestine is also considered to be an important site of intestinal immunity in fish, but functional histological studies of the lamina propria of the allogeneic crucian carp intestine are still lacking. In this study, Identification of the ubiquitous lamina propria mucus cells in the lamina propria of the intestine by hematoxylin-eosin staining, and determination of the mucocytic properties, class, and distribution of these cells in each intestinal segment by Alcian Blue-Periodic Acid-Schiff (AB-PAS) staining. The results show that type III mucus cells were abundant in the lamina propria of the foregut and midgut, while type II and type IV mucus cells predominate in the hindgut, possibly reflecting the distinct functions of these intestinal segments. Transmission electron microscopy dissected the differentiation of mucus cells in the lamina propria of the intestine at the ultrastructural level and investigated their morphology and distribution patterns in different intestinal segments, the findings revealed that lamina propria mucus cells perform rudimentary functions such as mucous secretion, phagocytosis, and degradation functions. Moreover, immunohistochemistry labeling with CD68 and LAMP1 revealed that numerous cells in the anterior, middle, and posterior intestines were positive for both proteins. Immunofluorescence double-labeling demonstrated that these cells highly co-expressed CD68 and LAMP1. Besides, the distribution and morphology of CD68+ and LAMP1+ cells were similar to those of AB-PAS positive cells and they accounted for the majority of parenchyma cells. Considering the above results, there were abundant cells with both mucous secretion and phagocytosis in the intestinal lamina propria of allogeneic crucian carp, which are a essential component of the intestinal immune process of allogeneic crucian carp.

Long Non-Coding RNAs and Their "Discrete" Contribution to IBD and Johne's Disease-What Stands out in the Current Picture? A Comprehensive Review

Non-coding RNAs (ncRNA) have paved the way to new perspectives on the regulation of gene expression, not only in biology and medicine, but also in associated fields and technologies, ensuring advances in diagnostic means and therapeutic modalities. Critical in this multistep approach are the associations of long non-coding RNA (lncRNA) with diseases and their causal genes in their networks of interactions, gene enrichment and expression analysis, associated pathways, the monitoring of the involved genes and their functional roles during disease progression from one stage to another. Studies have shown that Johne's Disease (JD), caused by Mycobacterium avium subspecies partuberculosis (MAP), shares common lncRNAs, clinical findings, and other molecular entities with Crohn's Disease (CD). This has been a subject of vigorous investigation owing to the zoonotic nature of this condition, although results are still inconclusive. In this review, on one hand, the current knowledge of lncRNAs in cells is presented, focusing on the pathogenesis of gastrointestinal-related pathologies and MAP-related infections and, on the other hand, we attempt to dissect the associated genes and pathways involved. Furthermore, the recently characterized and novel lncRNAs share common pathologies with IBD and JD, including the expression, molecular networks, and dataset analysis results. These are also presented in an attempt to identify potential biomarkers pertinent to cattle and human disease phenotypes.

Paneth cells in farm animals: current status and future direction

A healthy intestine plays an important role in the growth and development of farm animals. In small intestine, Paneth cells are well known for their regulation of intestinal microbiota and intestinal stem cells (ISCs). Although there has been a lot of studies and reviews on human and murine Paneth cells under intestinal homeostasis or disorders, little is known about Paneth cells in farm animals. Most farm animals possess Paneth cells in their small intestine, as identified by various staining methods, and Paneth cells of various livestock species exhibit noticeable differences in cell shape, granule number, and intestinal distribution. Paneth cells in farm animals and their antimicrobial peptides (AMPs) are susceptible to multiple factors such as dietary nutrients and intestinal infection. Thus, the comprehensive understanding of Paneth cells in different livestock species will contribute to the improvement of intestinal health. This review first summarizes the current status of Paneth cells in pig, cattle, sheep, horse, chicken and rabbit, and points out future directions for the investigation of Paneth cells in the reviewed animals.

Wnt Signaling in Brain Tumors: A Challenging Therapeutic Target

The involvement of Wnt signaling in normal tissue homeostasis and disease has been widely demonstrated over the last 20 years. In particular, dysregulation of Wnt pathway components has been suggested as a relevant hallmark of several neoplastic malignancies, playing a role in cancer onset, progression, and response to treatments. In this review, we summarize the current knowledge on the instructions provided by Wnt signaling during organogenesis and, particularly, brain development. Moreover, we recapitulate the most relevant mechanisms through which aberrant Wnt pathway activation may impact on brain tumorigenesis and brain tumor aggressiveness, with a particular focus on the mutual interdependency existing between Wnt signaling components and the brain tumor microenvironment. Finally, the latest anti-cancer therapeutic approaches employing the specific targeting of Wnt signaling are extensively reviewed and discussed. In conclusion, here we provide evidence that Wnt signaling, due to its pleiotropic involvement in several brain tumor features, may represent a relevant target in this context, although additional efforts will be needed to: (i) demonstrate the real clinical impact of Wnt inhibition in these tumors; (ii) overcome some still unsolved concerns about the potential systemic effects of such approaches; (iii) achieve efficient brain penetration.