Innate immunity in the small intestine

Understanding the Impact of Ostomy Dejecta Constituents on Peristomal Skin Health and Models for Its Characterisation

An ostomy, or stoma, is a surgically created percutaneous aperture from a hollow organ (e.g., small intestine) to the body's surface. Physicians may recommend an ostomy as a temporary or permanent solution to a range of disorders of the gastrointestinal tract, with up to 130 000 ostomies performed annually in the United States. An ostomy facilitates the expulsion of waste products, termed dejecta and circumvents the compromised organs. While an ostomy can be a lifesaving treatment, it is a disruption of regular digestive flow and has a number of associated complications including hernia, prolapse and necrosis. The most commonly observed complications are peristomal skin complications (PSCs), attributed to the leakage of dejecta onto the peristomal skin or the skin directly surrounding the stoma. Despite the prevalence of PSCs, little is known about the precise etiological factors that play a role in PSC formation. This review discusses the constituents of dejecta and their possible roles in PSC formation. Additionally, we identify a number of in vitro and in vivo skin models that could be used to study PSCs. Identification of the components of dejecta and understanding their interaction with skin models can facilitate the development of interventions to treat and prevent PSCs.

Gut-resident regulatory T cells (GTregs) play a pivotal role in maintaining bone health under postmenopausal osteoporotic conditions

Osteoporosis is a skeletal condition characterized by the deterioration of bone tissue. The immune system plays a crucial role in maintaining bone homeostasis and combating the development of osteoporosis. Immunoporosis is the term used to describe the recent convergence of research on the immune system's role in osteoporosis. The gut harbors the largest component of the immune system, and there is growing evidence that intestinal immunity plays a vital role in regulating bone health. Gut-resident regulatory T cells are essential in inhibiting immune responses and preventing various inflammatory manifestations. Our findings show that gut-resident regulatory T cells are pivotal in the pathophysiology of postmenopausal osteoporosis. We investigated the potential of gut-resident regulatory T cells in regulating the development of bone cells in vitro. We observed that gut-resident regulatory T cells significantly enhance osteoblastogenesis with concomitant inhibition of osteoclastogenesis in a cell ratio-dependent manner. We further report that the deficiency of short-chain fatty acids in osteoporotic conditions substantially disrupts the composition of gut-resident regulatory T cells, leading to a loss of peripherally derived regulatory T cells and an expansion of thymus-derived regulatory T cells. Moreover, the administration of probiotics Lactobacillus rhamnosus (UBLR-58) and Bifidobacterium longum (UBBL-64) modulated the gut-resident regulatory T cells compartment in a short-chain fatty acid-dependent manner to mitigate inflammatory bone loss in postmenopausal osteoporosis. Notably, short-chain fatty acid-primed gut-resident regulatory T cells were found to be significantly more effective in inhibiting osteoclastogenesis compared with unprimed gut-resident regulatory T cells. Altogether our results, for the first time, highlight the crucial role of gut-resident regulatory T cells in the pathophysiology of postmenopausal osteoporosis, with potential clinical implications.

Andrographis paniculata restores gut health by suppressing inflammation and strengthening mucosal immunity

Background

Gut immunity plays a critical role in overall health by balancing tolerance to food antigens and microbiota while defending against pathogens. Inflammation and infection in the gut can disrupt this balance, leading to disease. Andrographis paniculata, a plant used in traditional medicine, is known for its anti-inflammatory and immune-modulating properties, making it a promising candidate for treating gut-related conditions.

Methods

A. paniculata ethanolic extract (ApEtOH) was prepared by ethanol extraction of leaves, and bioactive compounds were identified using HPLC. Anti-inflammatory effects were evaluated in vitro using a Caco-2/RAW264.7 co-culture inflammation model via ELISA. Gene expression of chemokines in Caco-2 cells infected with Salmonella Typhimurium was assessed via quantitative real-time PCR. For in vivo studies, BALB/c mice were treated with ApEtOH at different doses, and the effects on bacterial load, immune response, and inflammation were assessed.

Results

ApEtOH significantly downregulated the chemokines RANTES, MCP-1, and ENA-78, reducing the pro-inflammatory cytokines TNF-α and IL-6 in vitro. In vivo studies demonstrated reduced bacterial colonization in the spleen, lower systemic markers of infection, and restoration of intestinal homeostasis. ApEtOH normalized serum IgA, increased IgG, and decreased TNF-α and IL-10 levels. It also increased the expression of mucin (Muc-2) and lysozyme (Lyz-1), which are critical for epithelial integrity and antimicrobial defense.

Conclusion

ApEtOH shows significant therapeutic potential for gut health by reducing bacterial colonization, modulating inflammation, and enhancing both innate and adaptive immunity. It may be a promising natural remedy for microbial induced gastrointestinal diseases and restoration of gut homeostasis.

The Immune Environment in Colorectal Adenoma: A Systematic Review

Background/Objectives: Research on colorectal adenoma is significantly less comprehensive compared to studies on colorectal carcinoma. Although colorectal adenoma is a precursor of the majority of sporadic colorectal cancers, not all adenomas develop into carcinomas. The complex interaction of immune responses in the premalignant tumor microenvironment might be a factor for that. Methods: In this systematic review, we aim to provide a thorough analysis of the current research examining the immune infiltration patterns in sporadic colorectal adenoma tissues in the context of immune cell-based, cytokine-based, and other immunological factor-related changes along the conventional adenoma-carcinoma sequence. The articles included in the review extend up to December 2024 in PubMed and Web of Science databases. Results: Most included studies have shown significant differences in immune cell counts, densities, and cytokine expression levels associated with premalignant colorectal lesions (and/or colorectal cancer). No consensus on the immune-related tendencies concerning CD4+T cells and CD8+T cells was reached. Decreasing expression of mDCs and plasma and naïve B cells were detected along the ACS. The increased density of tissue eosinophils in the adenoma tissue dramatically diminishes after the transition to carcinoma. As the adenoma progresses, the increasing expression of IL-1α, IL-4, IL-6, IL-8, IL-10, IL-17A, IL-21, IL-23, IL-33, and TGF-β and decreasing levels of IL-12A, IL-18, IFN-γ, and TNFα cytokines in the invasive carcinoma stage is being detected. The over-expression of COX-2, PD-1/PD-L1, CTLA-4, and ICOS/ICOSLG in the colorectal adenomatous and cancerous tissues was also observed. Conclusions: Further studies are needed for a better understanding of the whole picture of colorectal adenoma-associated immunity and its impact on precancerous lesion's potential to progress.

Immunomodulatory Effects of a Standardized Botanical Mixture Comprising Angelica gigas Roots and Pueraria lobata Flowers Through the TLR2/6 Pathway in RAW 264.7 Macrophages and Cyclophosphamide-Induced Immunosuppression Mice

Background: As the population ages, enhancing immune function is crucial to mitigating age-related physiological decline. Since immunostimulant drugs are known to have potential side effects, medicinal plants emerge as promising candidates offering a safer alternative. To leverage the advantages of medicinal plants with fewer side effects and develop a potent immune-enhancing agent, we investigated the efficacy of a novel immunomodulatory candidate derived from the combination of Angelica gigas and Pueraria lobata (CHL). Methods: In vitro, CHL was treated in RAW 264.7 macrophages at various time points, and the experiments conducted in the study were performed using ELISA, Western blot, and RT-qPCR analysis. In vivo, C57BL/6 mice were administrated CHL for 16 days (p.o.) and CTX on the three days (i.p.), and experiments were conducted with ELISA, western blot, RT-qPCR analysis, H&E staining, flow cytometry, gut microbiome, and correlation analysis. Results: In vitro, CHL has upregulated NO and cytokines expression, substantially enhancing the NF-κB and MAPK activation. Furthermore, CHL promoted the TAK1, TRAF6, and MyD88 via TLR2/6 signaling. In vivo, the CHL improved the reduced body weight and immune organs' indices and recovered various cytokines expression, NK cell cytotoxicity activity, and immune cell population. CHL also improved the histological structure and tight junction markers, mucin-2, and TLR2/6 in the intestines of CTX-induced mice. Conclusions: Overall, CHL demonstrated immunostimulatory potential by enhancing immune responses and restoring immune function, suggesting its promise as a safe and effective immune-enhancing agent.

A spatial expression atlas of the adult human proximal small intestine

The mouse small intestine shows profound variability in gene expression along the crypt-villus axis1,2. Whether similar spatial heterogeneity exists in the adult human gut remains unclear. Here we use spatial transcriptomics, spatial proteomics and single-molecule fluorescence in situ hybridization to reconstruct a comprehensive spatial expression atlas of the adult human proximal small intestine. We describe zonated expression and cell type representation for epithelial, mesenchymal and immune cell types. We find that migrating enterocytes switch from lipid droplet assembly and iron uptake at the villus bottom to chylomicron biosynthesis and iron release at the tip. Villus tip cells are pro-immunogenic, recruiting γδ T cells and macrophages to the tip, in contrast to their immunosuppressive roles in mouse. We also show that the human small intestine contains abundant serrated and branched villi that are enriched at the tops of circular folds. Our study presents a detailed resource for understanding the biology of the adult human small intestine.

Dynamic RNA polymerase II occupancy drives differentiation of the intestine under the direction of HNF4

Terminal differentiation requires massive restructuring of the transcriptome. During intestinal differentiation, the expression patterns of nearly 4,000 genes are altered as cells transition from progenitor cells in crypts to differentiated cells in villi. We identify dynamic occupancy of RNA polymerase II (Pol II) to gene promoters as the primary driver of transcriptomic shifts during intestinal differentiation in vivo. Changes in enhancer-promoter looping interactions accompany dynamic Pol II occupancy and are dependent upon HNF4, a pro-differentiation transcription factor. Using genetic loss-of-function, chromatin immunoprecipitation sequencing (ChIP-seq), and immunoprecipitation (IP) mass spectrometry, we demonstrate that HNF4 collaborates with chromatin remodelers and loop-stabilizing proteins and facilitates Pol II occupancy at hundreds of genes pivotal to differentiation. We also explore alternate mechanisms that drive differentiation gene expression and find that pause-release of Pol II and post-transcriptional mRNA stability regulate smaller subsets of differentially expressed genes. These studies provide insights into the mechanisms of differentiation in renewing adult tissue.

Basophil-Derived IL-4 and IL-13 Protect Intestinal Barrier Integrity and Control Bacterial Translocation during Malaria

Our previous work demonstrated that basophils regulate a suite of malaria phenotypes, including intestinal mastocytosis and permeability, the immune response to infection, gametocytemia, and parasite transmission to the malaria mosquito Anopheles stephensi. Given that activated basophils are primary sources of the regulatory cytokines IL-4 and IL-13, we sought to examine the contributions of these mediators to basophil-dependent phenotypes in malaria. We generated mice with basophils depleted for IL-4 and IL-13 (baso IL-4/IL-13 (-)) and genotype controls (baso IL-4/IL-13 (+)) by crossing mcpt8-Cre and Il4/Il13fl/fl mice and infected them with Plasmodium yoelii yoelii 17XNL. Conditional deletion was associated with ileal mastocytosis and mast cell (MC) activation, increased intestinal permeability, and increased bacterial 16S levels in blood, but it had no effect on neutrophil activation, parasitemia, or transmission to A. stephensi. Increased intestinal permeability in baso IL-4/IL-13 (-) mice was correlated with elevated plasma eotaxin (CCL11), a potent eosinophil chemoattractant, and increased ileal MCs, proinflammatory IL-17A, and the chemokines MIP-1α (CCL3) and MIP-1β (CCL4). Blood bacterial 16S copies were positively but weakly correlated with plasma proinflammatory cytokines IFN-γ and IL-12p40, suggesting that baso IL-4/IL-13 (-) mice failed to control bacterial translocation into the blood during malaria infection. These observations suggest that basophil-derived IL-4 and IL-13 do not contribute to basophil-dependent regulation of parasite transmission, but these cytokines do orchestrate protection of intestinal barrier integrity after P. yoelii infection. Specifically, basophil-dependent IL-4/IL-13 control MC activation and prevent infection-induced intestinal barrier damage and bacteremia, perhaps via regulation of eosinophils, macrophages, and Th17-mediated inflammation.

Mechanisms of intestinal dysbiosis: new insights into tuft cell functions

Symbiosis between the host and intestinal microbial communities is essential for human health. Disruption in this symbiosis is linked to gastrointestinal diseases, including inflammatory bowel diseases, as well as extra-gastrointestinal diseases. Unbalanced gut microbiome or gut dysbiosis contributes in multiple ways to disease frequency, severity and progression. Microbiome taxonomic profiling and metabolomics approaches greatly improved our understanding of gut dysbiosis features; however, the precise mechanisms involved in gut dysbiosis establishment still need to be clarified. The aim of this review is to present new actors and mechanisms underlying gut dysbiosis formation following parasitic infection or in a context of altered Paneth cells, revealing the existence of a critical crosstalk between Paneth and tuft cells to control microbiome composition.

The Potential Role of Intestinal Stem Cells and Microbiota for the Treatment of Colorectal Cancer

Colorectal cancer is a global health concern with high incidence and mortality rates. Conventional treatments like surgery, chemotherapy, and radiation therapy have limitations in improving patient survival rates. Recent research highlights the role of gut microbiota and intestinal stem cells in maintaining intestinal health and their potential therapeutic applications in colorectal cancer treatment. The interaction between gut microbiota and stem cells influences epithelial self-renewal and overall intestinal homeostasis. Novel therapeutic approaches, including immunotherapy, targeted therapy, regenerative medicine using stem cells, and modulation of gut microbiota, are being explored to improve treatment outcomes. Accordingly, this chapter provides an overview of the potential therapeutic applications of gut microbiota and intestinal stem cells in treating colorectal cancer.

Dynamic RNA Polymerase II Recruitment Drives Differentiation of the Intestine under the direction of HNF4

Terminal differentiation requires a massive restructuring of the transcriptome. During intestinal differentiation, the expression patterns of nearly 4000 genes are altered as cells transition from progenitor cells in crypts to differentiated cells in villi. We identified dynamic recruitment of RNA Polymerase II (Pol II) to gene promoters as the primary driver of transcriptomic shifts during intestinal differentiation in vivo. Changes in enhancer-promoter looping interactions accompany dynamic Pol II recruitment and are dependent upon HNF4, a pro-differentiation transcription factor. Using genetic loss-of- function, ChIP-seq and IP mass spectrometry, we demonstrate that HNF4 collaborates with chromatin remodelers and loop-stabilizing proteins and facilitates Pol II recruitment at hundreds of genes pivotal to differentiation. We also explore alternate mechanisms which drive differentiation gene expression and find pause-release of Pol II and post- transcriptional mRNA stability regulate smaller subsets of differentially expressed genes. These studies provide insights into the mechanisms of differentiation in a renewing adult tissue.

Paneth cell dysfunction in radiation injury and radio-mitigation by human α-defensin 5

Introduction

The mechanism underlying radiation-induced gut microbiota dysbiosis is undefined. This study examined the effect of radiation on the intestinal Paneth cell α-defensin expression and its impact on microbiota composition and mucosal tissue injury and evaluated the radio-mitigative effect of human α-defensin 5 (HD5).

Methods

Adult mice were subjected to total body irradiation, and Paneth cell α-defensin expression was evaluated by measuring α-defensin mRNA by RT-PCR and α-defensin peptide levels by mass spectrometry. Vascular-to-luminal flux of FITC-inulin was measured to evaluate intestinal mucosal permeability and endotoxemia by measuring plasma lipopolysaccharide. HD5 was administered in a liquid diet 24 hours before or after irradiation. Gut microbiota was analyzed by 16S rRNA sequencing. Intestinal epithelial junctions were analyzed by immunofluorescence confocal microscopy and mucosal inflammatory response by cytokine expression. Systemic inflammation was evaluated by measuring plasma cytokine levels.

Results

Ionizing radiation reduced the Paneth cell α-defensin expression and depleted α-defensin peptides in the intestinal lumen. α-Defensin down-regulation was associated with the time-dependent alteration of gut microbiota composition, increased gut permeability, and endotoxemia. Administration of human α-defensin 5 (HD5) in the diet 24 hours before irradiation (prophylactic) significantly blocked radiation-induced gut microbiota dysbiosis, disruption of intestinal epithelial tight junction and adherens junction, mucosal barrier dysfunction, and mucosal inflammatory response. HD5, administered 24 hours after irradiation (treatment), reversed radiation-induced microbiota dysbiosis, tight junction and adherens junction disruption, and barrier dysfunction. Furthermore, HD5 treatment also prevents and reverses radiation-induced endotoxemia and systemic inflammation.

Conclusion

These data demonstrate that radiation induces Paneth cell dysfunction in the intestine, and HD5 feeding prevents and mitigates radiation-induced intestinal mucosal injury, endotoxemia, and systemic inflammation.

Human Bone Marrow-Derived Mesenchymal Stromal Cells Reduce the Severity of Experimental Necrotizing Enterocolitis in a Concentration-Dependent Manner

Necrotizing enterocolitis (NEC) is a devastating gut disease in preterm neonates. In NEC animal models, mesenchymal stromal cells (MSCs) administration has reduced the incidence and severity of NEC. We developed and characterized a novel mouse model of NEC to evaluate the effect of human bone marrow-derived MSCs (hBM-MSCs) in tissue regeneration and epithelial gut repair. NEC was induced in C57BL/6 mouse pups at postnatal days (PND) 3-6 by (A) gavage feeding term infant formula, (B) hypoxia/hypothermia, and (C) lipopolysaccharide. Intraperitoneal injections of PBS or two hBM-MSCs doses (0.5 × 10⁶ or 1 × 10⁶) were given on PND2. At PND 6, we harvested intestine samples from all groups. The NEC group showed an incidence of NEC of 50% compared with controls (p < 0.001). Severity of bowel damage was reduced by hBM-MSCs compared to the PBS-treated NEC group in a concentration-dependent manner, with hBM-MSCs (1 × 10⁶) inducing a NEC incidence reduction of up to 0% (p < 0.001). We showed that hBM-MSCs enhanced intestinal cell survival, preserving intestinal barrier integrity and decreasing mucosal inflammation and apoptosis. In conclusion, we established a novel NEC animal model and demonstrated that hBM-MSCs administration reduced the NEC incidence and severity in a concentration-dependent manner, enhancing intestinal barrier integrity.

miR-92b-5p negatively regulates IKK through targeting its ORF region in the innate immune responses of amphioxus (Branchiostoma belcheri)

Cephalochordate (Amphioxus), situated at a key phylogenetic position in the phylum Chordata, serves as a model organism for studying the origin and evolution of the vertebrate innate immune. In this study, five members of precursor miR-92 family (miR-92a-1, miR-92a-2, miR-92b, miR-92c and miR-92d) are identified in Branchiostoma belcheri, and their evolutionary conservation and potential molecular functions in innate immunity are analyzed. Among them, miR-92b-5p was validated in HEK293 cells to target the coding region but not classic 3'UTR of IKK (inhibitor of nuclear factor kappa-B kinase) mRNA, one integral component of MAPK and TLR4 immune signaling. Furthermore, the spatiotemporal expression patterns of miR-92b-5p and IKK were examined in different tissues or different time points (2 h, 4 h, 8 h, 12 h, 24 h and 48 h) post LPS stimulation at RNA and protein level in vivo. The seemingly inverse expression pattern between miR-92b-5p and IKK supports the involvement of miR-92b-5p in Branchiostoma belcheri innate immune response. In conclusion, our work not only illustrates the evolutionary pattern of Branchiostoma belcheri miR-92 family across chordates, but also reveals that miR-92b-5p could target IKK expression to regulate innate immune response.

Changes in intestinal homeostasis and immunity in a cigarette smoke- and LPS-induced murine model for COPD: the lung-gut axis

Chronic obstructive pulmonary disease (COPD) is often associated with intestinal comorbidities. In this study, changes in intestinal homeostasis and immunity in a cigarette smoke (CS)- and lipopolysaccharide (LPS)-induced COPD model were investigated. Mice were exposed to cigarette smoke or air for 72 days, except days 42, 52, and 62 on which the mice were treated with saline or LPS via intratracheal instillation. Cigarette smoke exposure increased the airway inflammatory cell numbers, mucus production, and different inflammatory mediators, including C-reactive protein (CRP) and keratinocyte-derived chemokine (KC), in bronchoalveolar lavage (BAL) fluid and serum. LPS did not further impact airway inflammatory cell numbers or mucus production but decreased inflammatory mediator levels in BAL fluid. T helper (Th) 1 cells were enhanced in the spleen after cigarette smoke exposure; however, in combination with LPS, cigarette exposure caused an increase in Th1 and Th2 cells. Histomorphological changes were observed in the proximal small intestine after cigarette smoke exposure, and addition of LPS had no effect. Cigarette smoke activated the intestinal immune network for IgA production in the distal small intestine that was associated with increased fecal sIgA levels and enlargement of Peyer's patches. Cigarette smoke plus LPS decreased fecal sIgA levels and the size of Peyer's patches. In conclusion, cigarette smoke with or without LPS affects intestinal health as observed by changes in intestinal histomorphology and immune network for IgA production. Elevated systemic mediators might play a role in the lung-gut cross talk. These findings contribute to a better understanding of intestinal disorders related to COPD.

Beneficial effect of Xuebijing against Pseudomonas aeruginosa infection in Caenorhabditis elegans

In the clinical intensive care units (ICU), the traditional Chinese medicine (TCM) formulation of Xuebijing has been frequently used for treating sepsis. Nevertheless, the underlying pharmacological mechanisms of Xuebijing remain largely unclear. Caenorhabditis elegans is an important experimental host for bacterial infections. Using C. elegans as an animal model, we here examined the potential of Xuebijing treatment against bacterial infection and the underlying mechanisms. Xuebijing treatment could inhibit the reduction tendency of lifespan caused by Pseudomonas aeruginosa infection. For the cellular mechanisms of this antibacterial infection property, we found that Xuebijing treatment rescued C. elegans lifespan to be against P. aeruginosa infection by inhibiting Pseudomonas colonization in the intestinal lumen. Meanwhile, the increase in the expression of antimicrobial genes induced by Pseudomonas infection was also suppressed by Xuebijing treatment. Moreover, the beneficial effect of Xuebijing against Pseudomonas infection depended on insulin, p38 MAPK, Wnt, DBL-1/TGF-β, ELT-2, and programmed cell death (PCD)-related signals. Although Xuebijing did not show obvious antibacterial activity, Xuebijing (100%) treatment could inhibit the Pseudomonas biofilm formation and decrease the expression of virulence genes (lasA, lasB, rhlA, rhlC, phzA, phzM, phzH, and phzS) and quorum sensing (QS)-related genes (lasI, lasR, rhlI, rhlR, pqsA, and pqsR). Our results support the potential role of Xuebijing treatment against bacterial infection in hosts.

Mechanisms involved in controlling RNA virus-induced intestinal inflammation

Gastroenteritis is inflammation of the lining of stomach and intestines and causes significant morbidity and mortality worldwide. Many viruses, especially RNA viruses are the most common cause of enteritis. Innate immunity is the first line of host defense against enteric RNA viruses and virus-induced intestinal inflammation. The first layer of defense against enteric RNA viruses in the intestinal tract is intestinal epithelial cells (IECs), dendritic cells and macrophages under the intestinal epithelium. These innate immune cells express pathogen-recognition receptors (PRRs) for recognizing enteric RNA viruses through sensing viral pathogen-associated molecular patterns (PAMPs). As a result of this recognition type I interferon (IFN), type III IFN and inflammasome activation occurs, which function cooperatively to clear infection and reduce viral-induced intestinal inflammation. In this review, we summarize recent findings about mechanisms involved in enteric RNA virus-induced intestinal inflammation. We will provide an overview of the enteric RNA viruses, their RNA sensing mechanisms by host PRRs, and signaling pathways triggered by host PRRs, which shape the intestinal immune response to maintain intestinal homeostasis.

Effect of Supplementing Different Levels of L-Glutamine on Holstein Calves during Weaning

Weaning stress affects the health and performance of calves. L-glutamine (L-Gln) is commonly used as a functional antioxidant and energy supplement in the body. However, dietary L-Gln supplementation improving weaning stress of calves is unclear. Thus, we aimed to explore the effects of L-Gln (provided by rumen-protected L-Gln) on calves during weaning. Seventy-five Holstein calves (54.0 ± 2.68 kg; 42 ± 2.1 d of age) were assigned to five groups: no supplementation and L-Gln with 1%, 2%, 3%, and 4% dry matter daily intake (DMI) supplementation groups, respectively. The experiment lasted for 28 days (42–70 d of age of calves), and the calves were weaned at 15 d of experiment. DMI and body weekly weight of all calves were recorded. Blood samples of nine healthy calves with similar body weight were collected from each group at 0, 7, 14, 16, 18, 21, and 28 d of experiment for detecting serum L-Gln, glucose, insulin, urea nitrogen, D-lactate, cortisol, haptoglobin, interleukin-8, immunoglobulin (Ig) G, IgA, IgM, total antioxidant capacity, superoxide dismutase, glutathione peroxidase, catalase, and malondialdehyde. At the end of the experiment, six healthy calves with similar body weight from each group were selected for slaughter and morphological analysis of small intestine tissue. The results showed that the L-Gln supplementation in the diets improved the negative effects of sudden weaning in calves. Furthermore, compared to the higher-level L-Gln supple-mentation (3 and 4% of DMI) groups, the dietary lower-level L-Gln supplementation (1 and 2% of DMI) had higher average daily gain, glutathione peroxidase and IgG concentration, and villus height/crypt depth of the duodenum and jejunum, as well as lower cortisol, haptoglobin, and interleukin-8 concentration of weaned calves. These results provided effective reference for relieving the negative effects of calves during weaning.

Bacterial Toxin and Effector Regulation of Intestinal Immune Signaling

The host immune response is highly effective to detect and clear infecting bacterial pathogens. Given the elaborate surveillance systems of the host, it is evident that in order to productively infect a host, the bacteria often coordinate virulence factors to fine-tune the host response during infection. These coordinated events can include either suppressing or activating the signaling pathways that control the immune response and thereby promote bacterial colonization and infection. This review will cover the surveillance and signaling systems for detection of bacteria in the intestine and a sample of the toxins and effectors that have been characterized that cirumvent these signaling pathways. These factors that promote infection and disease progression have also been redirected as tools or therapeutics. Thus, these toxins are enemies deployed to enhance infection, but can also be redeployed as allies to enable research and protect against infection.

MicroRNA-based host response to toxicant exposure is influenced by the presence of gut microbial populations

Segmented filamentous bacteria (SFB) and Bacteroides fragilis are known to interact with the host immune response through the aryl hydrocarbon receptor (Ahr). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an environmental toxicant and a high-affinity Ahr ligand has the potential to modify the effect of SFB and B. fragilis. MicroRNAs (miRNA) with their role in regulating gene expression post-transcriptionally, may potentially be used to observe such interactions between SFB, B. fragilis, and TCDD. However, little is known regarding the impact of gut microbial members on miRNA expression or its modulation in the presence of an environmental toxicant. This information is important in understanding toxicant-mediated dysbiosis in gut microbiome and the resulting human health impacts. In this study, C57BL/6 germ-free (GF) mice were colonized with SFB and B. fragilis and administered 30 μg/kg TCDD every 4 d for 28 d and miRNA were measured. Compared to GF mice, colonization with SFB resulted in an increase in up- and down-regulated Ileal miRNAs. TCDD treatment of this group decreased the number of upregulated miRNA and increased the number of down-regulated miRNAs. Association with SFB and B. fragilis together had a similar but less pronounced effect in response to TCDD treatment. TCDD treatment of GF mice had no miRNA expression response. Immune and inflammatory responses and T-cell differentiation were the key functions impacted by these miRNAs. Overall, these results reveal that the host response to toxicants may also depend on the presence of specific gut microbial populations.

Early-life fingolimod treatment improves intestinal homeostasis and pancreatic immune tolerance in non-obese diabetic mice

Fingolimod has beneficial effects on multiple diseases, including type 1 diabetes (T1D) and numerous preclinical models of colitis. Intestinal dysbiosis and intestinal immune dysfunction contribute to disease pathogenesis of T1D. Thus, the beneficial effect of fingolimod on T1D may occur via the maintenance of intestinal homeostasis to some extent. Herein, we investigated the role of fingolimod in intestinal dysfunction in non-obese diabetic (NOD) mice and possible mechanisms. NOD mice were treated with fingolimod (1 mg · kg-1 per day, i.g.) from weaning (3-week-old) to 31 weeks of age. We found that fingolimod administration significantly enhanced the gut barrier (evidenced by enhanced expression of tight junction proteins and reduced intestinal permeability), attenuated intestinal microbial dysbiosis (evidenced by the reduction of enteric pathogenic Proteobacteria clusters), as well as intestinal immune dysfunction (evidenced by inhibition of CD4+ cells activation, reduction of T helper type 1 cells and macrophages, and the expansion of regulatory T cells). We further revealed that fingolimod administration suppressed the activation of CD4+ cells and the differentiation of T helper type 1 cells, promoted the expansion of regulatory T cells in the pancreas, which might contribute to the maintenance of pancreatic immune tolerance and the reduction of T1D incidence. The protection might be due to fingolimod inhibiting the toll-like receptor 2/4/nuclear factor-κB/NOD-like receptor protein 3 inflammasome pathway in the colon. Collectively, early-life fingolimod treatment attenuates intestinal microbial dysbiosis and intestinal immune dysfunction in the T1D setting, which might contribute to its anti-diabetic effect.

Probiotics Modulate Mouse Gut Microbiota and Influence Intestinal Immune and Serotonergic Gene Expression in a Site-Specific Fashion

Probiotic microorganisms may benefit the host by influencing diverse physiological processes, whose nature and underlying mechanisms are still largely unexplored. Animal models are a unique tool to understand the complexity of the interactions between probiotic microorganisms, the intestinal microbiota, and the host. In this regard, in this pilot study, we compared the effects of 5-day administration of three different probiotic bacterial strains (Bifidobacterium bifidum MIMBb23sg, Lactobacillus helveticus MIMLh5, and Lacticaseibacillus paracasei DG) on three distinct murine intestinal sites (ileum, cecum, and colon). All probiotics preferentially colonized the cecum and colon. In addition, probiotics reduced in the ileum and increased in the cecum and colon the relative abundance of numerous bacterial taxonomic units. MIMBb23sg and DG increased the inducible nitric oxide synthase (iNOS) in the ileum, which is involved in epithelial homeostasis. In addition, MIMBb23sg upregulated cytokine IL-10 in the ileum and downregulated the cyclooxygenase COX-2 in the colon, suggesting an anti-inflammatory/regulatory activity. MIMBb23sg significantly affected the expression of the main gene involved in serotonin synthesis (TPH1) and the gene coding for the serotonin reuptake protein (SERT) in the ileum and colon, suggesting a potential propulsive effect toward the distal part of the gut, whereas the impact of MIMLh5 and DG on serotonergic genes suggested an effect toward motility control. The three probiotics decreased the expression of the permeability marker zonulin in gut distal sites. This preliminary in vivo study demonstrated the safety of the tested probiotic strains and their common ability to modulate the intestinal microbiota. The probiotics affected host gene expression in a strain-specific manner. Notably, the observed effects in the gut were site dependent. This study provides a rationale for investigating the effects of probiotics on the serotonergic system, which is a topic still widely unexplored.

Presence and Germination of the Probiotic Bacillus subtilis DE111® in the Human Small Intestinal Tract: A Randomized, Crossover, Double-Blind, and Placebo-Controlled Study

Spore-based probiotics offer important advantages over other probiotics as they can survive the harsh gastric conditions of the stomach and bile salts in the small intestine, ultimately germinating in the digestive tract. A novel clinical trial in 11 ileostomy participants was conducted to directly investigate the presence and germination of the probiotic strain Bacillus subtilis DE111^® in the small intestine. Three hours following ingestion of DE111^®, B. subtilis spores (6.4 × 10⁴ ± 1.3 × 10⁵ CFU/g effluent dry weight) and vegetative cells (4.7 × 10⁴ ± 1.1 × 10⁵ CFU/g effluent dry weight) began to appear in the ileum effluent. Six hours after ingestion, spore concentration increased to 9.7 × 10⁷ ± 8.1 × 10⁷ CFU/g and remained constant to the final time point of 8 h. Vegetative cells reached a concentration of 7.3 × 10⁷ ± 1.4 × 10⁸ CFU/g at 7 h following ingestion. These results reveal orally ingested B. subtilis DE111^® spores are able to remain viable during transit through the stomach and germinate in the small intestine of humans within 3 h of ingestion.

Lactiplantibacillus plantarum 299v (LP299V®): three decades of research

This review aims to provide a comprehensive overview of the in vitro, animal, and clinical studies with the bacterial strain Lactiplantibacillus plantarum 299v (L. plantarum 299v; formerly named Lactobacillus plantarum 299v) published up until June 30, 2020. L. plantarum 299v is the most documented L. plantarum strain in the world, described in over 170 scientific publications out of which more than 60 are human clinical studies. The genome sequence of L. plantarum 299v has been determined and is available in the public domain (GenBank Accession number: NZ_LEAV01000004). The probiotic strain L. plantarum 299v was isolated from healthy human intestinal mucosa three decades ago by scientists at Lund University, Sweden. Thirty years later, a wealth of data coming from in vitro, animal, and clinical studies exist, showing benefits primarily for gastrointestinal health, such as reduced flatulence and abdominal pain in patients with irritable bowel syndrome (IBS). Moreover, several clinical studies have shown positive effects of L. plantarum 299v on iron absorption and more recently also on iron status. L. plantarum 299v is safe for human consumption and does not confer antibiotic resistance. It survives the harsh conditions of the human gastrointestinal tract, adheres to mannose residues on the intestinal epithelial cells and has in some cases been re-isolated more than ten days after administration ceased. Besides studying health benefits, research groups around the globe have investigated L. plantarum 299v in a range of applications and processes. L. plantarum 299v is used in many different food applications as well as in various dietary supplements. In a freeze-dried format, L. plantarum 299v is robust and stable at room temperature, enabling long shelf-lives of consumer healthcare products such as capsules, tablets, or powder sachets. The strain is patent protected for a wide range of indications and applications worldwide as well as trademarked as LP299V^®.

A New Target Organ of Leishmania (Viannia) braziliensis Chronic Infection: The Intestine

Leishmania (Viannia) braziliensis is one of the main causes of cutaneous leishmaniasis in the Americas. This species presents genetic polymorphism that can cause destructive lesions in oral, nasal, and oropharyngeal tracts. In a previous study, the parasite caused several histopathological changes to hamster ileums. Our study evaluates immune response components, morphological changes, and effects on neurons in the ileums of hamsters infected by three different strains of L. (V.) braziliensis in two infection periods. For the experiment, we separated hamsters into four groups: a control group and three infected groups. Infected hamsters were euthanized 90- or 120-days post infection. We used three strains of L. (V.) braziliensis: the reference MHOM/BR/1975/M2903 and two strains isolated from patients who had different responses to Glucantime^® treatment (MHOM/BR/2003/2314 and MHOM/BR/2000/1655). After laparotomy, ileums were collected for histological processing, biochemical analysis, and evaluation of neurons in the myenteric and submucosal plexuses of the enteric nervous system (ENS). The results demonstrated the increase of blood leukocytes after the infection. Optical microscopy analysis showed histopathological changes with inflammatory infiltrates, edemas, ganglionitis, and Leishmania amastigotes in the ileums of infected hamsters. We observed changes in the organ histoarchitecture of infected hamsters when compared to control groups, such as thicker muscular and submucosa layers, deeper and wider crypts, and taller and broader villi. The number of intraepithelial lymphocytes and TGF-β-immunoreactive cells increased in all infected groups when compared to the control groups. Mast cells increased with longer infection periods. The infection also caused remodeling of intestinal collagen and morphometry of myenteric and submucosal plexus neurons; but this effect was dependent on infection duration. Our results show that L. (V.) braziliensis infection caused time-dependent alterations in hamster ileums. This was demonstrated by the reduction of inflammatory cells and the increase of tissue regeneration factors at 120 days of infection. The infected groups demonstrated different profiles in organ histoarchitecture, migration of immune cells, and morphometry of ENS neurons. These findings suggest that the small intestine (or at least the ileum) is a target organ for L. (V.) braziliensis infection, as the infection caused changes that were dependent on duration and strain.

Influence of immunomodulatory drugs on the gut microbiota

Immunomodulatory medications are a mainstay of treatment for autoimmune diseases and malignancies. In addition to their direct effects on immune cells, these medications also impact the gut microbiota. Drug-induced shifts in commensal microbes can lead to indirect but important changes in the immune response. We performed a comprehensive literature search focusing on immunotherapy/microbe interactions. Immunotherapies were categorized into 5 subtypes based on their mechanisms of action: cell trafficking inhibitors, immune checkpoint inhibitors, immunomodulators, antiproliferative drugs, and inflammatory cytokine inhibitors. Although no consistent relationships were observed between types of immunotherapy and microbiota, most immunotherapies were associated with shifts in specific colonizing bacterial taxa. The relationships between colonizing microbes and drug efficacy were not well-studied for autoimmune diseases. In contrast, the efficacy of immune checkpoint inhibitors for cancer was tied to the baseline composition of the gut microbiota. There was a paucity of high-quality data; existing data were generated using heterogeneous sampling and analytic techniques, and most studies involved small numbers of participants. Further work is needed to elucidate the extent and clinical significance of immunotherapy effects on the human microbiome.

The interplay between gut microbiota and autism spectrum disorders: A focus on immunological pathways

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders characterized by impairments in social and cognitive activities, stereotypical and repetitive behaviors and restricted areas of interest. A remarkable proportion of ASD patients represent immune dysregulation as well as gastrointestinal complications. Hence, a novel concept has recently emerged, addressing the possible intercommunication between the brain, the immune system, the gut and its commensals. Here, we provide an overview of how gut microbes and their metabolites are associated with neurobehavioral features of ASD through various immunologic mechanisms. Moreover, we discuss the potential therapeutic options that could modify these features.

Mucosal immunity and tRNA, tRF, and tiRNA

Mucosal immunity has crucial roles in human diseases such as respiratory tract infection, inflammatory bowel diseases (IBD), and colorectal cancer (CRC). Recent studies suggest that the mononuclear phagocyte system, cancer cells, bacteria, and viruses induce the mucosal immune reaction by various pathways, and can be major factors in the pathogenesis of these diseases. Transfer RNA (tRNA) and its fragments, including tRNA-derived RNA fragments (tRFs) and tRNA-derived stress-induced RNAs (tiRNAs), have emerged as a hot topic in recent years. They not only are verified as essential for transcription and translation but also play roles in cellular homeostasis and functions, such as cell metastasis, proliferation, and apoptosis. However, the specific relationship between their biological regulation and mucosal immunity remains unclear to date. In the present review, we carry out a comprehensive discussion on the specific roles of tRNA, tRFs, and tiRNAs relevant to mucosal immunity and related diseases.

A porcine ligated loop model reveals new insight into the host immune response against Campylobacter jejuni

The symptoms of infectious diarrheal disease are mediated by a combination of a pathogen's virulence factors and the host immune system. Campylobacter jejuni is the leading bacterial cause of diarrhea worldwide due to its near-ubiquitous zoonotic association with poultry. One of the outstanding questions is to what extent the bacteria are responsible for the diarrheal symptoms via intestinal cell necrosis versus immune cell initiated tissue damage. To determine the stepwise process of inflammation that leads to diarrhea, we used a piglet ligated intestinal loop model to study the intestinal response to C. jejuni. Pigs were chosen due to the anatomical similarity between the porcine and the human intestine. We found that the abundance of neutrophil related proteins increased in the intestinal lumen during C. jejuni infection, including proteins related to neutrophil migration (neutrophil elastase and MMP9), actin reorganization (Arp2/3), and antimicrobial proteins (lipocalin-2, myeloperoxidase, S100A8, and S100A9). The appearance of neutrophil proteins also corresponded with increases of the inflammatory cytokines IL-8 and TNF-α. Compared to infection with the C. jejuni wild-type strain, infection with the noninvasive C. jejuni ∆ciaD mutant resulted in a blunted inflammatory response, with less inflammatory cytokines and neutrophil markers. These findings indicate that intestinal inflammation is driven by C. jejuni virulence and that neutrophils are the predominant cell type responding to C. jejuni infection. We propose that this model can be used as a platform to study the early immune events during infection with intestinal pathogens.

SOD1 suppresses pro-inflammatory immune responses by protecting against oxidative stress in colitis

Superoxide dismutase 1 (SOD1) binds copper and zinc ions and is one of three superoxide dismutases responsible for destroying free superoxide radicals in the body. Reactive oxygen species (ROS), including free superoxide radicals, play important roles in colitis. However, the role of SOD1 in oxidative stress under colitis remains unclear. Here, we examined the role of SOD1 in the DSS-induced mouse model of colitis. SOD1 deficiency resulted in severe oxidative stress with body weight loss, epithelial barrier disruption and decreased antioxidant enzyme activities. The levels of neutrophils, monocytes, pro-inflammatory CD11c⁺ macrophages and CD11b⁺CD103^- dendritic cells (DCs) were increased, while anti-inflammatory CD206⁺ macrophages and CD11b^-CD103⁺ DCs were decreased, in DSS-treated SOD1-knockout (KO) mice compared to DSS-treated wild-type mice. Furthermore, rescue of SOD activity in SOD1-KO mice by oral gavage of B. amyloliquefaciens SOD (BA SOD) significantly ameliorated enhanced DSS-induced colitis in these mice by suppressing p38-MAPK/NF-κB signaling, which can induce inflammation and apoptosis. Taken together, our results suggest that SOD1-mediated inhibitory responses play a crucial role in limiting the development of DSS-induced colitis, and that BA SOD is a promising candidate for treating colitis.

Changes in expression of antimicrobial peptides and Fc receptors in the small intestines of neonatal calves during the passive immunity period

The contribution of colostrum to passive immunity transfer and intestinal protection is well known; however, the effects of colostrum intake on the expression of antimicrobial peptides (AP) and Fc receptors in the intestine of neonatal calves are unclear. Our aim was to investigate changes in the expression of AP and Fc receptor in the small intestine of calves in the first 36 h postpartum. Twenty-four Holstein bull calves were used in this study, of which 18 calves were administered 3.2 L of pooled colostrum for each calf per meal via an esophageal tube. Calves were slaughtered at 8 h (1 meal at 1-2 h), 24 h (2 meals at 1-2 h and 10-12 h), and 36 h (3 meals at 1-2 h, 10-12 h, and 22-24 h) postpartum. The remaining 6 calves without any milk administration were slaughtered at 2 h postpartum. Samples of blood and jejunum digesta were collected to determine immunoglobulin concentration using ELISA. Samples of the duodenum, jejunum, and ileum tissues after slaughter were collected to determine AP and Fc receptor expression using quantitative real-time PCR. In calves administered colostrum, IgG concentration in jejunum digesta rapidly decreased in an age-dependent manner (33.41, 9.47, and 0.34 mg/mL at 8, 24, and 36 h, respectively), whereas serum IgG concentration increased significantly, from 0.25 μg/mL at 2 h to 21.72 mg/mL at 24 h. Cathelicidin-4, β-defensin (DEFB)-7, and enteric β-defensin expression was upregulated at 8 h postpartum in the duodenum and jejunum compared with that at 2 h, but progressive recovery was detected from 24 h onward. Higher expression of cathelicidin-4, regenerating family member 3γ, lysozyme (LYZ), LYZ1, and LYZ2 and lower expression of DEFB, DEFB1, DEFB7, DEFB10, and enteric β-defensin were observed in the duodenum and jejunum compared with the ileum. Differences in AP expression between intestinal regions suggested that the innate immune defense mechanism varied significantly among the duodenum, jejunum, and ileum. No difference in the expression of Fc fragment of the IgG receptor was observed either among ages or small intestinal regions. The Fcγ receptor (FcγR)Ia and FcγRIIb expression was the highest at 8 h compared with that at 2, 24, and 36 h, and expression of FcγRIa, FcγRIIb, and FcγRIIIa was higher in the duodenum and jejunum than in the ileum. These results indicated that AP and Fcγ receptors might play important roles in intestinal defense during the passive immunity period.

Impact of a Multistrain Probiotic Formulation with High Bifidobacterial Content on the Fecal Bacterial Community and Short-Chain Fatty Acid Levels of Healthy Adults

The consumption of probiotic products is continually increasing, supported by growing scientific evidence of their efficacy. Considering that probiotics may primarily affect health (either positively or negatively) through gut microbiota modulation, the first aspect that should be evaluated is their impact on the intestinal microbial ecosystem. In this study, we longitudinally analyzed the bacterial taxonomic composition and organic acid levels in four fecal samples collected over the course of four weeks from 19 healthy adults who ingested one capsule a day for two weeks of a formulation containing at least 70 billion colony-forming units, consisting of 25% lactobacilli and 75% Bifidobacterium animalis subsp. lactis. We found that 16S rRNA gene profiling showed that probiotic intake only induced an increase in a single operational taxonomic unit ascribed to B. animalis, plausibly corresponding to the ingested bifidobacterial strain. Furthermore, liquid chromatography/mass spectrometry revealed a significant increase in the lactate and acetate/butyrate ratio and a trend toward a decrease in succinate following probiotic administration. The presented results indicate that the investigated probiotic formulation did not alter the intestinal bacterial ecosystem of healthy adults and suggest its potential ability to promote colonization resistance in the gut through a transient increase in fecal bifidobacteria, lactic acid, and the acetate/butyrate ratio.

Effect of arginine or glutamine supplementation and milk feeding allowance on small intestine development in calves

The development of the small intestine (SI) is important for the health and growth of neonatal calves. This study evaluated the effect of arginine (Arg) and glutamine (Gln) supplementation and 2 levels of milk allowance on the histomorphological development of the SI in preweaning calves. Sixty mixed-sex Friesian × Jersey calves (3-5 d of age) were offered reconstituted whole milk (125 g/L, 26% fat, 26% protein) at either high (20% of arrival body weight/d; HM) or low (10% of arrival body weight/d; LM) milk allowance without (Ctrl) or with supplementary Arg or Gln (at 1% of milk dry matter) in a 2 × 3 factorial design (n = 10/treatment). After 35 d on the diets, all calves were slaughtered to collect tissues for examination of SI development. Calves in the HM group had higher milk intake, total weight gain, and average daily gain compared with LM calves, but no effect of AA supplementation nor an interaction between milk allowance and AA supplementation was observed. For the duodenum, we observed an AA by milk allowance interaction for villus height and width, and goblet cell number per villus (HM-Arg > HM-Gln > HM-Ctrl), and villus height to crypt depth ratio (HM-Arg > HM-Gln = HM-Ctrl), but no effect of AA supplementation in the LM group. Goblet cell numbers per 100 µm of SI were greater in Arg-supplemented calves than in unsupplemented controls, with Gln-supplemented calves intermediate to but not different from the other groups. Epithelium thickness was greater in LM than in HM calves. Villus density, crypt depth, and muscle thickness did not differ between groups. For the jejunum, there was an AA by milk allowance interaction for villus height, villus surface area, and villus height to crypt depth ratio (HM-Arg = HM-Gln > HM-Ctrl), with no effect of AA supplementation in the LM groups. Amino acid supplementation affected goblet cell number per villus (HM-Gln > HM-Ctrl calves, HM-Arg intermediate), and both LM-Arg and LM-Gln calves had greater numbers than LM-Ctrl calves. Villus width, crypt depth, and muscle thickness were greater in HM than LM calves but there was no effect of AA supplementation. Villus density, goblet cell number per 100 µm of SI, and epithelium thickness were unaffected by AA supplementation and milk allowance. Milk allowance and AA supplementation had no effect on SI morphology in the ileum. Increasing milk allowance improved villus height, width, and surface area but only in Arg- or Gln-supplemented calves, not in control calves. The observed changes in development may be important for intestinal functionality, integrity, and barrier function in preweaning calves, potentially through increased cell growth and proliferation or reduced levels of cellular atrophy.

The Role of Glycosaminoglycans in Protection from Neonatal Necrotizing Enterocolitis: A Narrative Review

Necrotizing enterocolitis, a potentially fatal intestinal inflammatory disorder affecting primarily premature infants, is a significant cause of morbidity and mortality in neonates. While the etiology of the disease is, as yet, unknown, a number of risk factors for the development of necrotizing enterocolitis have been identified. One such risk factor, formula feeding, has been shown to contribute to both increased incidence and severity of the disease. The protective influences afforded by breastfeeding are likely attributable to the unique composition of human milk, an extremely potent, biologically active fluid. This review brings together knowledge on the pathogenesis of necrotizing enterocolitis and current thinking on the instrumental role of one of the more prominent classes of bioactive components in human breast milk, glycosaminoglycans.

Gastrointestinal tract modeling using organoids engineered with cellular and microbiota niches

The recent emergence of organoid technology has attracted great attention in gastroenterology because the gastrointestinal (GI) tract can be recapitulated in vitro using organoids, enabling disease modeling and mechanistic studies. However, to more precisely emulate the GI microenvironment in vivo, several neighboring cell types and types of microbiota need to be integrated into GI organoids. This article reviews the recent progress made in elucidating the crosstalk between GI organoids and components of their microenvironment. We outline the effects of stromal cells (such as fibroblasts, neural cells, immune cells, and vascular cells) on the gastric and intestinal epithelia of organoids. Because of the important roles that microbiota play in the physiology and function of the GI tract, we also highlight interactions between organoids and commensal, symbiotic, and pathogenic microorganisms and viruses. GI organoid models that contain niche components will provide new insight into gastroenterological pathophysiology and disease mechanisms.

Burn-Induced Impairment of Ileal Muscle Contractility Is Associated with Increased Extracellular Matrix Components

INTRODUCTION

Severe burns lead to marked impairment of gastrointestinal motility, such as delayed gastric emptying and small and large intestinal ileus. However, the cellular mechanism of these pathologic changes remains largely unknown.

METHODS

Male Sprague Dawley rats approximately 3 months old and weighing 300-350 g were randomized to either a 60% total body surface area full-thickness scald burn or sham procedure and were sacrificed 24 h after the procedure. Gastric emptying, gastric antrum contractility ileal smooth muscle contractility, and colonic contractility were measured. Muscularis externa was isolated from the ileal segment to prepare smooth muscle protein extracts for Western blot analysis.

RESULTS

Compared with sham controls, the baseline rhythmic contractile activities of the antral, ileal, and colonic smooth muscle strips were impaired in the burned rats. Simultaneously, our data showed that ileal muscularis ECM proteins fibronectin and laminin were significantly up-regulated in burned rats compared with sham rats. TGF-β signaling is an important stimulating factor for ECM protein expression. Our results revealed that TGF-β signaling was activated in the ileal muscle of burned rats evidenced by the activation of Smad2/3 expression and phosphorylation. In addition, the total and phosphorylated AKT, which is an important downstream factor of ECM signaling in smooth muscle cells, was also up-regulated in burned rats' ileal muscle. Notably, these changes were not seen in the colonic or gastric tissues.

CONCLUSION

Deposition of fibrosis-related proteins after severe burn is contributors to decreased small intestinal motility.

Microbial Control of Intestinal Homeostasis via Enteroendocrine Cell Innate Immune Signaling

A community of commensal microbes, known as the intestinal microbiota, resides within the gastrointestinal tract of animals and plays a role in maintenance of host metabolic homeostasis and resistance to pathogen invasion. Enteroendocrine cells, which are relatively rare in the intestinal epithelium, have evolved to sense and respond to these commensal microbes. Specifically, they express G-protein-coupled receptors and functional innate immune signaling pathways that recognize products of microbial metabolism and microbe-associated molecular patterns, respectively. Here we review recent evidence from Drosophila melanogaster that microbial cues recruit antimicrobial, mechanical, and metabolic branches of the enteroendocrine innate immune system and argue that this response may play a role not only in maintaining host metabolic homeostasis but also in intestinal resistance to invasion by bacterial, viral, and parasitic pathogens.

NHR-14 loss of function couples intestinal iron uptake with innate immunity in C. elegans through PQM-1 signaling

Iron is essential for survival of most organisms. All organisms have thus developed mechanisms to sense, acquire and sequester iron. In C. elegans, iron uptake and sequestration are regulated by HIF-1. We previously showed that hif-1 mutants are developmentally delayed when grown under iron limitation. Here we identify nhr-14, encoding a nuclear receptor, in a screen conducted for mutations that rescue the developmental delay of hif-1 mutants under iron limitation. nhr-14 loss upregulates the intestinal metal transporter SMF-3 to increase iron uptake in hif-1 mutants. nhr-14 mutants display increased expression of innate immune genes and DAF-16/FoxO-Class II genes, and enhanced resistance to Pseudomonas aeruginosa. These responses are dependent on the transcription factor PQM-1, which localizes to intestinal cell nuclei in nhr-14 mutants. Our data reveal how C. elegans utilizes nuclear receptors to regulate innate immunity and iron availability, and show iron sequestration as a component of the innate immune response.

Curcumin and Intestinal Inflammatory Diseases: Molecular Mechanisms of Protection

Intestinal inflammatory diseases, such as Crohn’s disease, ulcerative colitis, and necrotizing enterocolitis, are becoming increasingly prevalent. While knowledge of the pathogenesis of these related diseases is currently incomplete, each of these conditions is thought to involve a dysfunctional, or overstated, host immunological response to both bacteria and dietary antigens, resulting in unchecked intestinal inflammation and, often, alterations in the intestinal microbiome. This inflammation can result in an impaired intestinal barrier allowing for bacterial translocation, potentially resulting in systemic inflammation and, in severe cases, sepsis. Chronic inflammation of this nature, in the case of inflammatory bowel disease, can even spur cancer growth in the longer-term. Recent research has indicated certain natural products with anti-inflammatory properties, such as curcumin, can help tame the inflammation involved in intestinal inflammatory diseases, thus improving intestinal barrier function, and potentially, clinical outcomes. In this review, we explore the potential therapeutic properties of curcumin on intestinal inflammatory diseases, including its antimicrobial and immunomodulatory properties, as well as its potential to alter the intestinal microbiome. Curcumin may play a significant role in intestinal inflammatory disease treatment in the future, particularly as an adjuvant therapy.

Toll-Like Receptors: Regulators of the Immune Response in the Human Gut

Toll-like receptors (TLRs) are powerful molecular regulators by which the immune system may "sense" the environment and protect the host from pathogens or endogenous threats. In mammalian cells, several TLRs were identified with a tissue and cell type-specific distribution. Understanding the functions of specific TLRs is crucial for the development and discovery of compounds useful to maintaining or re-establishing homeostasis in the gastrointestinal tract (GIT). Due to their relevance in regulating the inflammatory response in the GIT, we will focus here on TLR2, TLR4, and TLR5. In particular, we describe (a) the molecular pathways activated by the stimulation of these receptors with their known bacterial ligands; (b) the non-bacterial ligands known to interact directly with TLR2 and TLR4 and their soluble forms. The scope of this minireview is to highlight the importance of bacterial and non-bacterial compounds in affecting the gut immune functions via the activation of the TLRs.

Dietary N-Glycans from Bovine Lactoferrin and TLR Modulation

SCOPE

Bovine lactoferrin (bLF) is an ingredient of food supplements and infant formulas given its antimicrobial and antiviral properties. We modified bLF enzymatically to alter its N-glycosylation and to isolate the glycan chains. The aims of this study include (1) to evaluate whether such derivates induce responses via pattern recognition receptors namely Toll-like receptors (TLRs) and (2) to relate those responses to their different glycosylation profiles.

METHODS AND RESULTS

The unmodified and modified bLF fractions are incubated with reporter cell lines expressing pattern recognition receptors. Afterwards, we screen for TLRs and analyze for nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) activation. Activation of reporter cell lines show that signaling is highly dependent on TLRs. The activation pattern of bLF is reduced with the desialylated form and increased with the demannosylated form. In reporter cells for TLR, bLF activate TLR-4 and inhibit TLR-3. The isolated glycans from bLF inhibit TLR-8. TLR-2, TLR-5, TLR-7, and TLR-9 are not significantly altered.

CONCLUSION

The profile of glycosylation is key for the biological activity of bLF. By understanding how this affects the human defense responses, the bLF glycan profile can be modified to enhance its immunomodulatory effects when used as a dietary ingredient.

Regulation of low-density lipoprotein cholesterol by intestinal inflammation and the acute phase response

Systemic inflammation, induced by disease or experimental intervention, is well established to result in elevated levels of circulating triglycerides, and reduced levels of high-density lipoprotein-cholesterol (HDL-C), in most mammalian species. However, the relationship between inflammation and low-density lipoprotein-cholesterol (LDL-C) concentrations is less clear. Most reports indicate that systemic inflammation, as observed during sepsis or following high dose experimental endotoxaemia, lowers total, and LDL-C in man. However, isolated reports have suggested that certain inflammatory conditions are associated with increased LDL-C. In this review, we summarize the emerging evidence that low-grade inflammation specifically of intestinal origin may be associated with increased serum LDL-C levels. Preliminary insights into potential mechanisms that may mediate these effects, including those connecting inflammation to trans-intestinal cholesterol efflux (TICE), are considered. We conclude that this evidence supports the potential downregulation of major mediators of TICE by inflammatory mediators in vitro and during intestinal inflammation in vivo. The TICE-inflammation axis therefore merits further study in terms of its potential to regulate serum LDL-C, and as a readily druggable target for hypercholesterolaemia.

Enhanced Rg3 negatively regulates Th1 cell responses

Background

Korean Red Ginseng (KRG; Panax ginseng Meyer) is a widely used medicinal herb known to exert various immune modulatory functions. KRG and one of its purified components, ginsenoside Rg3, are known to possess anti-inflammatory activities. How they impact helper T cell-mediated responses is not fully explored. In this study, we attempted to evaluate the effect of KRG extract (KRGE) and ginsenoside Rg3 on Th1 cell responses.

Methods

Using well-characterized T cell in vitro differentiation systems, we examined the effects of KRGE or enhanced Rg3 on the Th1-inducing cytokine production from dendritic cells (DC) and the naïve CD4⁺ T cells differentiation to Th1 cells. Furthermore, we examined the change of Th1 cell population in the intestine after treatment of enhanced Rg3. The influence of KRGE or enhanced Rg3 on Th1 cell differentiation was evaluated by fluorescence-activated cell sorting, enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction.

Results

KRGE significantly inhibited the production level of IL-12 from DCs and subsequent Th1 cell differentiation. Similarly, enhanced Rg3 significantly suppressed the expression of interferon gamma (IFNγ) and T-bet in T cells under Th1-skewing condition. Consistent with these effects in vitro, oral administration of enhanced Rg3 suppressed the frequency of Th1 cells in the Peyer's patch and lamina propria cells in vivo.

Conclusion

Enhanced Rg3 negatively regulates the differentiation of Th1 cell in vitro and Th1 cell responses in the gut in vivo, providing fundamental basis for the use of this agent to treat Th1-related diseases.

Relation between NOD2 genotype and changes in innate signaling in Crohn's disease on mRNA and miRNA levels

Crohn’s disease is associated with an altered innate immune response of pathogenic importance. This altered response can be associated to loss-of-function polymorphisms in the NOD2 (nucleotide-binding oligomerization domain-containing protein 2) gene, but also changes in transcriptional and post-transcriptional regulatory layers, including microRNA activity. Here, we characterized the link between NOD2 genotype and inflammatory-mediated changes in innate signaling by studying transcriptional and post-transcriptional activity in response to NOD2-agonist muramyl dipeptide in monocytes from healthy controls, and Crohn’s disease patients with and without NOD2 loss-of-function polymorphisms. We measured the expression of genes and microRNAs in monocytes from these subjects after stimulation with muramyl dipeptide. Gene expression profiles mainly distinguished the actual muramyl dipeptide response, but not the genotype. A hyper-responsive phenotype was found in Crohn’s disease patients without NOD2 mutations, characterized by upregulated cytokine receptors and general downregulation of microRNA expression. Conversely, microRNA expression could identify genotype-specific differences between subject groups but exhibited little change upon muramyl dipeptide treatment. Only two microRNAs showed muramyl dipeptide-induced response, including miR-155, which was found to regulate multiple genes and whose host gene was one of the highest muramyl dipeptide responders. miR-155 was upregulated in Crohn’s disease patients with NOD2 mutations following lipopolysaccharide and Escherichia coli treatment, but the upregulation was substantially reduced upon muramyl dipeptide treatment. While Crohn’s disease patients with NOD2 mutations on average showed a reduced muramyl dipeptide response, the cohort exhibited large individual variance: a small subset had inflammatory responses almost comparable to wild-type patients on both gene and miR-155 regulatory levels.

The genetics of people with Crohn’s disease affects the molecular drivers of their dysregulated immune responses. Some individuals with Crohn’s harbor mutations in the NOD2 gene, which encodes a pathogen recognition receptor that binds to a molecule called muramyl dipeptide (MDP). To better understand how alternations in NOD2 can lead to increased susceptibility to gut inflammation, Yun Chen, Mohammad Salem and colleagues from the University of Copenhagen and Herlev Hospital, Denmark, analyzed the expression patterns of both genes and small, regulatory microRNAs in blood cells from healthy controls and from Crohn’s patients with and without NOD2 mutations. They exposed the cells to MDP, and saw that although gene acticity changed dramatically as a response, there was little difference between subjects, regardless of genetics. Conversely, microRNA expression showed genotype-specific differences that weren not impacted by MDP treatment. The findings underscore the importance of microRNAs in Crohn’s disease.

Defensins, lectins, mucins, and secretory immunoglobulin A: microbe-binding biomolecules that contribute to mucosal immunity in the human gut

In the intestine, the mucosal immune system plays essential roles in maintaining homeostasis between the host and microorganisms, and protecting the host from pathogenic invaders. Epithelial cells produce and release a variety of biomolecules into the mucosa and lumen that contribute to immunity. In this review, we focus on a subset of these remarkable host-defense factors - enteric α-defensins, select lectins, mucins, and secretory immunoglobulin A - that have the capacity to bind microbes and thereby contribute to barrier function in the human gut. We provide an overview of the intestinal epithelium, describe specialized secretory cells named Paneth cells, and summarize our current understanding of the biophysical and functional properties of these select microbe-binding biomolecules. We intend for this compilation to complement prior reviews on intestinal host-defense factors, highlight recent advances in the field, and motivate investigations that further illuminate molecular mechanisms as well as the interplay between these molecules and microbes.