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BackgroundInflammatory bowel disease is an incurable and idiopathic disease characterized by recurrent gastrointestinal tract inflammation. Tryptophan metabolism in mammalian cells and some gut microbes comprise intricate chemical networks facilitated by catalytic enzymes that affect the downstream metabolic pathways of de novo nicotinamide adenine dinucleotide (NAD+) synthesis. It is hypothesized that a correlation exists between tryptophan de novo NAD+ synthesis and chronic intestinal inflammation.MethodsTranscriptome analysis was performed using high-throughput sequencing of mRNA extracted from the distal colon and brain tissue of Winnie mice with spontaneous chronic colitis and C57BL/6 littermates. Metabolites were assessed using ultra-fast liquid chromatography to determine differences in concentrations of tryptophan metabolites. To evaluate the relative abundance of gut microbial genera involved in tryptophan and nicotinamide metabolism, we performed 16S rRNA gene amplicon sequencing of fecal samples from C57BL/6 and Winnie mice.ResultsTryptophan and nicotinamide metabolism-associated gene expression was altered in distal colons and brains of Winnie mice with chronic intestinal inflammation. Changes in these metabolic pathways were reflected by increases in colon tryptophan metabolites and decreases in brain tryptophan metabolites in Winnie mice. Furthermore, dysbiosis of gut microbiota involved in tryptophan and nicotinamide metabolism was evident in fecal samples from Winnie mice. Our findings shed light on the physiological alterations in tryptophan metabolism, specifically, its diversion from the serotonergic pathway toward the kynurenine pathway and consequential effects on de novo NAD+ synthesis in chronic intestinal inflammation.ConclusionThe results of this study reveal differential expression of tryptophan and nicotinamide metabolism-associated genes in the distal colon and brain in Winnie mice with chronic intestinal inflammation. These data provide evidence supporting the role of tryptophan metabolism and de novo NAD+ synthesis in IBD pathophysiology.

Abstract The gut has a specific vascular barrier that controls trafficking of antigens and microbiota into the bloodstream. However, the molecular mechanisms regulating the maintenance of this vascular barrier remain elusive. Here, we identified Caspase‐8 as a pro‐survival factor in mature intestinal endothelial cells that is required to actively maintain vascular homeostasis in the small intestine in an organ‐specific manner. In particular, we find that deletion of Caspase‐8 in endothelial cells results in small intestinal hemorrhages and bowel inflammation, while all other organs remained unaffected. We also show that Caspase‐8 seems to be particularly needed in lymphatic endothelial cells to maintain gut homeostasis. Our work demonstrates that endothelial cell dysfunction, leading to the breakdown of the gut‐vascular barrier, is an active driver of chronic small intestinal inflammation, highlighting the role of the intestinal vasculature as a safeguard of organ function.

Eosinophils and their regulatory molecules have been associated with chronic intestinal inflammation and gastrointestinal dysfunctions; eosinophil accumulation in the gut is prominent in inflammatory bowel disease (IBD). The chemokine receptor CCR3 plays a pivotal role in local and systemic recruitment and activation of eosinophils. In this study, we targeted CCR3-ligand interactions with a potent CCR3 receptor antagonist, SB328437, to alleviate eosinophil-associated immunological responses in the Winnie model of spontaneous chronic colitis. Winnie and C57BL/6 mice were treated with SB328437 or vehicle. Clinical and histopathological parameters of chronic colitis were assessed. Flow cytometry was performed to discern changes in colonic, splenic, circulatory, and bone marrow-derived leukocytes. Changes to the serum levels of eosinophil-associated chemokines and cytokines were measured using BioPlex. Inhibition of CCR3 receptors with SB328437 attenuated disease activity and gross morphological damage to the inflamed intestines and reduced eosinophils and their regulatory molecules in the inflamed colon and circulation. SB328437 had no effect on eosinophils and their progenitor cells in the spleen and bone marrow. This study demonstrates that targeting eosinophils via the CCR3 axis has anti-inflammatory effects in the inflamed intestine, and also contributes to understanding the role of eosinophils as potential end-point targets for IBD treatment. [ABSTRACT FROM AUTHOR]

The gut has a specific vascular barrier that controls trafficking of antigens and microbiota into the bloodstream. However, the molecular mechanisms regulating the maintenance of this vascular barrier remain elusive. Here, we identified Caspase‐8 as a pro‐survival factor in mature intestinal endothelial cells that is required to actively maintain vascular homeostasis in the small intestine in an organ‐specific manner. In particular, we find that deletion of Caspase‐8 in endothelial cells results in small intestinal hemorrhages and bowel inflammation, while all other organs remained unaffected. We also show that Caspase‐8 seems to be particularly needed in lymphatic endothelial cells to maintain gut homeostasis. Our work demonstrates that endothelial cell dysfunction, leading to the breakdown of the gut‐vascular barrier, is an active driver of chronic small intestinal inflammation, highlighting the role of the intestinal vasculature as a safeguard of organ function. SYNOPSIS: Inflammatory bowel disease (IBD) is a group of disorders that causes severe inflammation of the intestine. This study identified that vascular dysfunction in the small intestine results in classic features of IBD in mice. Adult mice lacking Caspase‐8 (Casp8) in endothelial cells (Casp8ECko) die within 3 weeks after tamoxifen treatment with severe intestine inflammation and mucosal hemorrhages, whereas all other organs are not affected.Casp8ECko mice show lymphatic and blood vessel regression in the small intestine that can be prevented by co‐deletion of MLKL.Deletion of Casp8 solely in the blood endothelium (not in lymphatics) does not manifest bowel inflammation, suggesting that Casp8 is primarily required as a pro‐survival factor in the lymphatic vasculature.Disease development in Casp8ECko mice is dependent on the presence of microbiota. [ABSTRACT FROM AUTHOR]

Introduction: Schematic illustration of the synthetic protocols and therapeutic mechanisms of HA-BSA@DS. We report a pioneering endogenous GSH-responsive nanoplatform, meticulously engineered for the controlled release of hydrogen sulfide (H 2 S) within inflamed intestinal tissues, thus offering a new avenue for gaseous intervention in chronic enteritis. [Display omitted] • Here, we report a nano-delivery platform for effective intervention in UC with H 2 S release in response to intracellular GSH. • Nano-platform can improve inflammatory response by regulating Nrf2/NF-κB/iNOS/NLRP3 signaling pathway. • Nanoparticles can modulate the homeostasis of gut microbiota. • Tese nanoparticles achieve gaseous intervention for the intervention of intestinal inflammation. Overproduction of reactive oxygen species (ROS) is a primary cause of chronic intestinal inflammation, controlled nanosequence-like drugs with GSH-responsive release have become a new focus in scavenging ROS and treating inflammation. Here, we report an endogenous GSH-responsive nanoplatform, meticulously engineered for the controlled release of hydrogen sulfide (H 2 S) within inflamed intestinal tissues, thus offering a new avenue for gaseous intervention against chronic enteritis. Diallyl trisulfide (DS) as molecular H 2 S donors was conjugated into sulfhydrylated bovine serum albumin (BSA·SH) through a 'thio-ene' click chemistry reaction, leading to the synthesis of the BSA@DS polymer. This substrate was subsequently coated with hyaluronic acid, yielding HA-BSA@DS nanoparticles. As sulfide bonds in DS are responsive to intracellular GSH to release H 2 S and HA achieves inflamed site-targeted release specifically towards CD44-overexpressed inflamed tissues, these nanoparticles attenuate pro-inflammatory cytokine outputs while concurrently upregulate anti-inflammatory factors, thus mitigating cellular oxidative perturbations and inflammatory responses in inflamed cells. Moreover, upon oral administration, these nanoparticles exhibit profound anti-inflammatory efficacy via the TLR4/MD2/MyD88/NF-κB/iNOS signal pathway and modulating the homeostasis of intestinal microbiota in a mouse model with colitis. Consequently, this convenient and targeted oral nanoparticle effectively enables gaseous multiple intervention at the inflammatory site, providing a favorable theoretical basis for subsequent oral formulations in the treatment of related inflammation. [ABSTRACT FROM AUTHOR]

Genome wide association studies have associated single nucleotide polymorphisms within the gene locus encoding protein tyrosine phosphatase non-receptor type 2 (PTPN2) with the onset of inflammatory bowel disease (IBD) and other inflammatory disorders. Expression of PTPN2 is enhanced in actively inflamed intestinal tissue featuring a marked up-regulation in intestinal epithelial cells. PTPN2 deficient mice suffer from severe intestinal and systemic inflammation and display aberrant innate and adaptive immune responses. In particular, PTPN2 is involved in the regulation of inflammatory signalling cascades, and critical for protecting intestinal epithelial barrier function, regulating innate and adaptive immune responses, and finally for maintaining intestinal homeostasis. On one hand, dysfunction of PTPN2 has drastic effects on innate host defence mechanisms, including increased secretion of pro-inflammatory cytokines, limited autophagosome formation in response to invading pathogens, and disruption of the intestinal epithelial barrier. On the other hand, PTPN2 function is crucial for controlling adaptive immune functions, by regulating T cell proliferation and differentiation as well as maintaining T cell tolerance. In this way, dysfunction of PTPN2 contributes to the manifestation of IBD. The aim of this review is to present an overview of recent findings on the role of PTPN2 in intestinal homeostasis and the impact of dysfunctional PTPN2 on intestinal inflammation.

Background: Inflammatory bowel disease is an incurable and idiopathic disease characterized by recurrent gastrointestinal tract inflammation. Tryptophan metabolism in mammalian cells and some gut microbes comprise intricate chemical networks facilitated by catalytic enzymes that affect the downstream metabolic pathways of de novo nicotinamide adenine dinucleotide (NAD + ) synthesis. It is hypothesized that a correlation exists between tryptophan de novo NAD + synthesis and chronic intestinal inflammation., Methods: Transcriptome analysis was performed using high-throughput sequencing of mRNA extracted from the distal colon and brain tissue of Winnie mice with spontaneous chronic colitis and C57BL/6 littermates. Metabolites were assessed using ultra-fast liquid chromatography to determine differences in concentrations of tryptophan metabolites. To evaluate the relative abundance of gut microbial genera involved in tryptophan and nicotinamide metabolism, we performed 16S rRNA gene amplicon sequencing of fecal samples from C57BL/6 and Winnie mice., Results: Tryptophan and nicotinamide metabolism-associated gene expression was altered in distal colons and brains of Winnie mice with chronic intestinal inflammation. Changes in these metabolic pathways were reflected by increases in colon tryptophan metabolites and decreases in brain tryptophan metabolites in Winnie mice. Furthermore, dysbiosis of gut microbiota involved in tryptophan and nicotinamide metabolism was evident in fecal samples from Winnie mice. Our findings shed light on the physiological alterations in tryptophan metabolism, specifically, its diversion from the serotonergic pathway toward the kynurenine pathway and consequential effects on de novo NAD + synthesis in chronic intestinal inflammation., Conclusion: The results of this study reveal differential expression of tryptophan and nicotinamide metabolism-associated genes in the distal colon and brain in Winnie mice with chronic intestinal inflammation. These data provide evidence supporting the role of tryptophan metabolism and de novo NAD + synthesis in IBD pathophysiology., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Devereaux, Robinson, Stavely, Davidson, Dargahi, Ephraim, Kiatos, Apostolopoulos and Nurgali.)

Purpose: To investigate if the association between dietary inflammatory potential and colorectal adenoma (CRA) is modified by race and factors known to modulate inflammation. Methods: We examined effect measure modification of race, nonsteroidal anti-inflammatory drugs (NSAIDs), cigarette smoking and body mass index (BMI) on the diet-CRA association by employing energy-adjusted dietary inflammatory index (E-DII™) to characterize dietary inflammatory potential among 587 cases and 1,313 controls participating in a colonoscopy screening-based cross-sectional study of CRA. Participants completed a food frequency questionnaire from which E-DII score was derived. E-DII score was calculated from 34 food parameters (constituents), utilizing an energy-adjusted global comparative database to compute z scores from which centered proportions were summed to create the score. CRA cases were defined as individuals whose colonoscopy detected at least one pathologically confirmed adenomatous polyp. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results: A pro-inflammatory diet was not statistically significantly associated with elevated CRA risk (OR 1.07; 95% CI 0.97–1.19; p value = 0.18) in the multivariate regression model. NSAIDs use (ORnever-users 1.19; 95% CI 1.03–1.38; ORever-users 0.96; 95% CI 0.83–1.12; Pinteraction = 0.04) and race (ORAfrican Americans 1.22; 95% CI 1.03–1.44; OREuropean Americans 0.99; 95% CI 0.86–1.14; Pinteraction = 0.14) appeared to modify the association, whereas cigarette smoking and BMI did not (Pinteraction = 0.40 and 0.78, respectively). Conclusion: NSAIDs use and race may modify the diet-CRA association. Further investigation in prospective cohort studies is warranted to confirm these findings. [ABSTRACT FROM AUTHOR]

Intestinal inflammatory disorders are associated with neurophysiological and behavioral symptoms. Conversely, many disorders of the central nervous system (CNS) are accompanied by intestinal complications. These observations suggest that intestinal and nervous system physiologies are functionally linked. Indeed, a growing body of literature has revealed multiple pathways mediating bidirectional communication between the intestine and the CNS, collectively referred to as the gut-brain axis. In particular, microbes naturally colonizing the mammalian gastrointestinal (GI) tract, termed the gut microbiota, not only correlate with but also play a causative role in regulating CNS function, development and host behavior. Despite these findings, our understanding of the cellular and molecular mechanisms that mediate gut-brain communication remains in its infancy. However, members of the gut microbiota have been established as potent modulators of intestinal, systemic and CNS-resident immune cell function, suggesting that gut-brain interactions may involve the host immune system. Multiple CNS disorders with gut microbiota associations, including neuroinflammatory, neuropsychiatric and neurodegenerative disorders, also have significant inflammatory manifestations. In this review, I discuss recent advances exploring the role of microbiota-immune interactions as a critical regulator of the gut-brain axis in the context of CNS and related disorders.

It has been shown that the gut microbiota plays a crucial role in the maintenance of intestinal homeostasis. Additionally, it has been demonstrated that dysbiosis is closely correlated with chronic intestinal inflammation, contributing to the development of chronic intestinal diseases, and also of brain pathologies, including neurodegenerative, neurodevelopmental, and psychiatric disorders. Given the paramount importance of gut microbiota for the establishment of communication between the gut and the brain, the microbiota-gut-brain axis has been increasingly explored within the scope of neurosciences. In this review article, we present an overview of key cellular signaling pathways underlying chronic intestinal inflammation and the influence of chronic intestinal inflammation and dysbiosis on brain disorders. This will include the presentation of valuable data from recent preclinical and clinical research. We will also address the importance of probiotics and prebiotics to targeting the microbiota-gut-brain axis in the context of some brain disorders, where they are seen to be promising strategies for ameliorating brain disorders. [ABSTRACT FROM AUTHOR]

Biologic activity of proteases is mainly characterized by the substrate specificity, tissue distribution, and cellular localization. The human metalloproteases meprin α and meprin β share 41% sequence identity and exhibit a similar cleavage specificity with a preference for negatively charged amino acids. However, shedding of meprin α by furin on the secretory pathway makes it a secreted enzyme in comparison with the membrane-bound meprin β. In this study, we identified human meprin α and meprin β as forming covalently linked membrane-tethered heterodimers in the early endoplasmic reticulum, thereby preventing furin-mediated secretion of meprin α. Within this newly formed enzyme complex, meprin α was able to be activated on the cell surface and detected by cleavage of a novel specific fluorogenic peptide substrate. However, the known meprin β substrates amyloid precursor protein and CD99 were not shed by membrane-tethered meprin α. On the other hand, being linked to meprin α, activation of or substrate cleavage by meprin β on the cell surface was not altered. Interestingly, proteolytic activity of both proteases was increased in the heteromeric complex, indicating an increased proteolytic potential at the plasma membrane. Because meprins are susceptibility genes for inflammatory bowel disease (IBD), and to investigate the physiologic impact of the enzyme complex, we performed transcriptome analyses of intestinal mucosa from meprin-knockout mice. Comparison of the transcriptional gene analysis data with gene analyses of IBD patients revealed that different gene subsets were dysregulated if meprin α was expressed alone or in the enzyme complex, demonstrating the physiologic and pathophysiological relevance of the meprin heterodimer formation. [ABSTRACT FROM AUTHOR]

Background and Aim: Irritable bowel syndrome (IBS) is a highly prevalent chronic functional gastrointestinal disorder. Recent studies have showed increasing important role of gut microbiota in the pathophysiological changes of IBS. Our study aims to elaborate the association between intestinal flora with the genesis and the development of IBS. Methods: Illumina high‐throughput sequencing technology was applied to investigate microbial communities of IBS patients and healthy donors. Stool specimens from the IBS‐D patients were equally premixed and implanted into germ free C57B/6 mice to construct IBS animal model, and the normal group was also transplanted with normal premixed feces. The post‐transplant defecation and intra‐epithelial lymphocyte counts were evaluated. Microbial communities were also checked by the illumina high‐throughput sequencing technology. Results: Fifteen genuses significantly different were found expressed in the gut flora of IBS patients, and six genuses showed significantly different abundances between the stool specimens of mice of IBS group and normal group. Among these differences, Parasutterella expression was remarkably different in both screening and validation experiments and also related to chronic intestinal inflammation; therefore, Parasutterella expression is considered in association with the development and progression of IBS. Conclusion: Parasutterella may be related with the genesis and development of IBS and also associated with chronic intestinal inflammation in IBS patients. [ABSTRACT FROM AUTHOR]

During chronic intestinal inflammation in rabbit intestinal villus cells brush border membrane (BBM) Na-glucose co-transport (SGLT1), but not Na/H exchange (NHE3) is inhibited. The mechanism of inhibition is secondary to a decrease in the number of BBM co-transporters. In the chronic enteritis mucosa, inducible nitric oxide (iNO) and superoxide production are known to be increased and together they produce abundant peroxynitrite (OONO), a potent oxidant. However, whether OONO mediates the SGLT1 and NHE3 changes in intestinal epithelial cells during chronic intestinal inflammation is unknown. Thus, we determined the effect of OONO on SGLT1 and NHE3 in small intestinal epithelial cell (IEC-18) monolayers grown on trans well plates. In cells treated with 100 μM SIN-1 (OONO donor) for 24 h, SGLT1 was inhibited while NHE3 activity was unaltered. SIN-1 treated cells produced 40 times more OONO fluorescence compared to control cells. Uric acid (1mM) a natural scavenger of OONO prevented the OONO mediated SGLT1 inhibition. Na+/K+-ATPase which maintains the favorable trans-cellular Na gradient for Na-dependent absorptive processes was decreased by OONO. Kinetics studies demonstrated that the mechanism of inhibition of SGLT1 by OONO was secondary to reduction in the number of co-transporters (Vmax) without an alteration in the affinity. Western blot analysis showed a significant decrease in SGLT1 protein expression. Further, p38 mitogen-activated protein (MAP) kinase pathway appeared to mediate the OONO inhibition of SGLT1. Finally, at the level of the co-transporter, 3-Nitrotyrosine formation appears to be the mechanism of inhibition of SGLT1. In conclusion, peroxynitrite inhibited BBM SGLT1, but not NHE3 in intestinal epithelial cells. These changes and the mechanism of SGLT1 inhibition by OONO in IEC-18 cells is identical to that seen in villus cells during chronic enteritis. Thus, these data indicate that peroxynitrite, known to be elevated in the mucosa, may mediate the inhibition of villus cell BBM SGLT1 in vivo in the chronically inflamed intestine.

Na-K-ATPase located on the basolateral membrane (BLM) of intestinal epithelial cells provides a favorable intracellular Na + gradient to promote all Na dependent co-transport processes across the brush border membrane (BBM). Down-regulation of Na-K-ATPase activity has been postulated to alter the absorption via Na-solute co-transporters in human inflammatory bowel disease (IBD). Further, the altered activity of a variety of Na-solute co-transporters in intact villus cells has been reported in animal models of chronic enteritis. But the molecular mechanism of down-regulation of Na-K-ATPase is not known. In the present study, using a rabbit model of chronic intestinal inflammation, which resembles human IBD, Na-K-ATPase in villus cells was shown to decrease. The relative mRNA abundance of α -1 and β -1 subunits was not altered in villus cells during chronic intestinal inflammation. Similarly, the protein levels of these subunits were also not altered in villus cells during chronic enteritis. However, the BLM concentration of α-1 and β -1 subunits was diminished in the chronically inflamed intestinal villus cells. An ankyrin–spectrin skeleton is necessary for the proper trafficking of Na-K-ATPase to the BLM of the cell. In the present study, ankyrin expression was markedly diminished in villus cells from the chronically inflamed intestine resulting in depolarization of ankyrin-G protein. The decrease of Na-K-ATPase activity was comparable to that seen in ankyrin knockdown IEC-18 cells. Therefore, altered localization of Na-K-ATPase as a result of transcriptional down-regulation of ankyrin-G mediates the down-regulation of Na-K-ATPase activity during chronic intestinal inflammation. [ABSTRACT FROM AUTHOR]

Leukotriene D4 (LTD4) is an important immune inflammatory mediator that is known to be elevated in the mucosa of chronically inflamed intestine and alter nutrient absorption. LTD4 inhibits Na-alanine cotransport in intestinal epithelial cells by decreasing the affinity of the cotransporter ASCT1. LTD4 is known to increase intracellular Ca++ and cAMP concentrations. However, the intracellular signaling mechanism of LTD4-mediated ASCT1 inhibition is unknown. In the present study, pre-treatment with calcium chelator BAPTA-AM or inhibition of Ca++-dependent protein kinase C (PKC), specifically PKCa, resulted in the reversal of LTD4-mediated inhibition of ASCT1, revealing the involvement of the Ca++-activated PKC pathway. PKCa is known to phosphorylate Raf kinase inhibitor protein (RKIP), thus activating its downstream signaling pathway. Immunoblotting with anti-RKIP-Ser153 antibody showed an increase in phosphorylation levels of RKIP in LTD4-treated cells. Downregulation of endogenous RKIP showed no decrease in ASCT1 activity by LTD4, thus confirming its involvement in ASCT1 regulation. Phosphorylation of RKIP by PKC is known to activate different signaling pathways, and in this study it was found to activate cAMP-activated protein kinase A (PKA) pathway. Although protein abundance of ASCT1 was not altered in any of the experimental conditions, there was an increase in the levels of phosphothreonine in ASCT1 protein, thus showing that phosphorylation changes were responsible for the altered affinity of ASCT1 by LTD4. In conclusion, LTD4 inhibits ASCT1 through PKC-mediated phosphorylation of RKIP, leading to the subsequent activation of PKA pathway, possibly through β2-andrenergic receptor activation. [ABSTRACT FROM AUTHOR]

The inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis, are chronic inflammatory disorders of the intestine. The prevalence in the United States is greater than 200 cases per 100,000, with the total number of IBD patients between 1 and 1.5 million. Crohn’s disease may affect all parts of the gastrointestinal tract, from mouth to anus, but most commonly involves the distal part of the small intestine or ileum, and colon. Ulcerative colitis results in colonic inflammation that can affect the rectum only, or can progress proximally to involve part of or the entire colon. Clinical symptoms include diarrhea, abdominal pain, gastrointestinal bleeding and weight loss. A serious long-term complication of chronic inflammation is the development of colorectal cancer. A genetic basis for IBD had long been recognized based on the increased familial risk. However, significant discordance for Crohn’s disease in twins, and a much less robust phenotypic concordance for ulcerative colitis, suggested additional factors play a role in disease pathogenesis, including environmental factors. In the past several years, progress in understanding the molecular basis of IBD has accelerated, beginning with the generation of animal models of colitis and progressing to the identification of specific genetic markers from candidate gene, gene linkage and genome wide association analyses . Genetic studies have also resulted in the recognition of the importance of environmental factors, particularly the crucial role of the gut microbiota in Crohn’s disease and ulcerative colitis. Altered immune responses to the normal intestinal flora are key factors in IBD pathogenesis. In this Research Topic, the genetic basis of IBD, the genetic and cellular alterations associated with colitis-associated colon cancer, and the emerging role of the intestinal microbiota and other environmental factors will be reviewed.

The inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the intestine. The prevalence in the United States is greater than 200 cases per 100,000, with the total number of IBD patients between 1 and 1.5 million. CD may affect all parts of the gastrointestinal tract, from mouth to anus, but most commonly involves the distal part of the small intestine or ileum, and colon. UC results in colonic inflammation that can affect the rectum only, or can progress proximally to involve part of or the entire colon. Clinical symptoms include diarrhea, abdominal pain, gastrointestinal bleeding, and weight loss. A serious long-term complication of chronic inflammation is the development of colorectal cancer. A genetic basis for IBD had long been recognized based on the increased familial risk. However, significant discordance for CD in twins, and a much less robust phenotypic concordance for UC, suggested additional factors play a role in disease pathogenesis, including environmental factors. In the past several years, progress in understanding the molecular basis of IBD has accelerated, beginning with the generation of animal models of colitis and progressing to the identification of specific genetic markers from candidate gene, gene linkage, and genome-wide association analyses. Genetic studies have also resulted in the recognition of the importance of environmental factors, particularly the crucial role of the gut microbiota in CD and UC. Altered immune responses to the normal intestinal flora are key factors in IBD pathogenesis. In this research topic, the genetic basis of IBD, the genetic and cellular alterations associated with colitis-associated colon cancer, and the emerging role of the intestinal microbiota and other environmental factors will be reviewed. [ABSTRACT FROM AUTHOR]

Abstract: The gastrointestinal (GI) tract has many important biological functions. One is to serve as a barrier between the fish and the external environment. A decreased physical barrier function of the intestine may lead to increased inflow of luminal content and subsequent activation of the intestinal mucosal immune system. This activation is governed by the ability of various compounds to induce cytokine release and immune cell activity, leading to an immune response. In mammals, the impact of stress on the intestinal barrier is well documented and results in increased intestinal permeability and thus increased stimulation of the mucosal immune system. Fish reared in sea cages may at times be exposed to unfavourable environmental conditions leading to chronic stress and disturbed intestinal integrity. This change in permeability may increase the exposure of the mucosal immune system to activating compounds. In the present study, the effect of a prolonged stress on the intestinal mucosal immune system of fish is therefore addressed. Atlantic salmon were exposed to low levels (50%) of dissolved oxygen (DO) for 6–7 weeks in consecutive experiments performed at 8 and 16 °C. Immune parameters were assessed in terms of mRNA expression of the key cytokines, interleukin-1β (IL-1β), IL-8, IL-10, interferon-γ (IFNγ) and transforming growth factor-β (TGFβ) as well as the immune regulatory inhibitor of nuclear factor κB (IκB). In the experiment at 8 °C also mucosal neutrophil infiltration was monitored. Subjecting the fish to low DO levels at 8 °C resulted in an increased mucosal neutrophil infiltration together with a down-regulation of IκB. At the higher temperature, 16 °C, low DO levels created decreased expression of the pro-inflammatory cytokine IL-1β in both intestinal regions as well as an increased expression of IL-10 in the proximal intestine. These results suggest that husbandry conditions in sea cages with DO levels as low as 50% clearly affects the intestinal mucosal immune system and results in a chronic inflammation. Moreover, the effects of low DO levels on the immune factors examined were more pronounced in the 16 °C experiment suggesting additive effects of high temperatures. [Copyright &y& Elsevier]

Caecal samples from wild-type and TNFdeltaARE mice were cultured on selective media containing bile salts, amino acids or casein macro-peptides. Twenty-two strains were isolated and identified by 16S rRNA gene sequencing. Twenty-one strains showed >98% similarity to known bacteria ( Blautia spp., Clostridium innocuum, Enterococcus spp., Escherichia coli, Lactobacillus murinus, Parabacteroides goldsteinii and Shigella dysenteriae). One additional isolate, strain A-C2-0, was a new bacterium. The closest relatives were Bacteroides massiliensis, Bacteroides dorei and Bacteroides vulgatus (≤94% similarity). Strain A-C2-0 is a Gram-negative rod that does not form spores and has a G + C content of DNA of 41.5%. Its major cellular fatty acid is C15:0 ANTEISO, and its major respiratory quinone is MK-9. Cells are aerotolerant but grow only under strict anoxic conditions. They are resistant to cefotaxime and tobramycin. When compared with related Bacteroides spp., the new bacterium was positive for α-arabinosidase, negative for glutamyl glutamic acid arylamidase and did not metabolise galactose, glucose, fructose, mannose, raffinose and sucrose. Strain A-C2-0 therefore merits recognition as a member of a novel species within the genus Bacteroides, for which the name Bacteroides sartorii is proposed. The type strain is A-C2-0T (= DSM 21941T = CCUG 57211T). [ABSTRACT FROM AUTHOR]

Simple Summary: Colorectal carcinoma (CRC) is one of the most frequent cancers in western countries, and non-invasive methods for early detection are still needed. Circulating tumor cells (CTC) in blood of CRC patients have been proven as prognostic and predictive biomarker; however, the suitability of CTC-associated markers for early CRC detection and discrimination from benign diseases has not been analyzed. Thus, this study investigated whether CTC-associated markers can also be detected in the blood of patients with benign inflammatory intestinal disease (IID) or whether they are specific for malignancy. The detection rate of CK20 and DEFA5 clearly differed in diseased patients and healthy controls, while LAD1 and PLS3 was found in all samples but with clear qualitative differences in gene expression. No association between inflammation severity and CTC marker expression was found in IID patients. Finally, PLS3 was identified to be a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls. Colorectal carcinoma (CRC) belongs to the most common tumor entities in western countries. Circulating tumor cells (CTC) in blood of CRC patients are a powerful prognostic and predictive biomarker. However, whether CTC-associated markers can also be used for early CRC detection and discrimination from benign diseases is not known. This study investigated the presence of CTC-associated markers CK20, PLS3, LAD1, and DEFA5 in blood of patients with benign inflammatory intestinal disease (IID) and their correlation with malignancy. The detection rate of CK20 and DEFA5 significantly differed between diseased patients and healthy controls. LAD1 and PLS3 were detected in all samples with clear differences in gene expression. DEFA5 expression was higher in CRC and IID patients compared to healthy donors, while CK20 and PLS3 were lower in CRC compared to IID patients or healthy controls. Overall, all CTC-associated markers were detectable in blood of IID patients, but not correlating with inflammation severity. Finally, PLS3 emerged as a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls, however its suitability for early CRC detection needs to be further validated. [ABSTRACT FROM AUTHOR]

In a rabbit model of chronic intestinal inflammation, we previously demonstrated inhibition of neutral Na-amino acid cotransport. The mechanism of the inhibition was secondary to a decrease in the affinity for amino acid rather than the number of cotransporters. Since leukotriene (LT)D4 is known to be elevated in enterocytes during chronic intestinal inflammation, we used rat intestinal epithelial cell (IEC-18) monolayers to determine the mechanism of regulation of Na-alanine cotransport (alanine, serine, cysteine transporter 1: ASCT1) by LTD4. Na-alanine cotransport was inhibited by LTD4 in IEC-18 cells. The mechanism of inhibition of ASCT1 (solute carrier, SLC1A4) by LTD4 is secondary to a decrease in the affinity of the cotransporter for alanine without a significant change in cotransporter numbers and is not secondary to an alteration in the Na! extruding capacity of the cells. Real-time quantitative PCR and Western blot analysis results indicate that ASCT1 message and protein levels are also unchanged in LTD4-treated IEC-18 cells. These results indicate that LTD4 inhibits Na-dependent neutral amino acid cotransport in TEC. The mechanism of inhibition is secondary to a decrease in the affinity for alanine, which is identical to that seen in villus cells from the chronically inflamed rabbit small intestine, where LTD4 levels are significantly increased. [ABSTRACT FROM AUTHOR]

Nonpathogenic enteric bacterial species initiate and perpetuate experimental colitis in interleukin-10 geneeficient mice (IL-10-/-). Bacteria-specific effects on the epithelium are difficult to distinguish because of the complex nature of the gut microflora. We showed that IL-10-/- mice compared to wild-type mice fail to inhibit pro-inflammatory gene expression in native intestinal epithelial cells after the colonization with colitogenic Gram-positive Enterococcus faecalis. Of interest, pro-inflammatory gene expression was transient after 1 week of E. faecalis monoassociation in IECs from wild-type mice but persisted after 14 weeks of bacterial colonization in IL-10-/- mice. Accordingly, wild-type IECs expressed phosphorylated NF-kappaB subunit RelA (p65) and phosphorylated Smad2 only at day 7 after bacterial colonization, whereas E. faecalis-monoassociated IL-10-/- mice triggered persistent RelA but no Smad2 phosphorylation in IECs at days 3, 7, 14, and 28. Consistent with the induction of TLR2-mediated RelA phosphorylation and pro-inflammatory gene expression in E. faecalis-stimulated cell lines, TLR2 protein expression was absent after day 7 from E. faecalis-monoassociated wild-type mice but persisted in IL-10-/- IECs. Of note, TGF-beta-activated Smad signaling was associated with the loss of TLR2 protein expression and the inhibition of NF-kappa Bependent gene expression in E. faecalis-stimulated IEC lines. In conclusion, E. faecalis-monoassociated IL-10-/- but not wild-type mice lack protective TGF-beta/Smad signaling and fail to inhibit TLR2-mediated pro-inflammatory gene expression in the intestinal epithelium, suggesting a critical role for IL-10 and TGF-beta in maintaining normal epithelial cell homeostasis in the interplay with commensal enteric bacteria. [ABSTRACT FROM AUTHOR]

Advancing knowledge regarding the cellular mechanisms of intestinal inflammation has led to a better understanding of the disease pathology in patients with chronic disorders of the gut including inflammatory bowel disease, coeliac disease, lymphocytic colitis and irritable bowel syndrome. An emerging new paradigm suggests that changes in the homeostasis of bacteria- and host-derived signal transduction at the epithelial cell level may lead to functional and immune disturbances of the intestinal epithelium. It has become clear from numerous studies that enteric bacteria are a critical component in the development and prevention/treatment of chronic intestinal inflammation. Signal-specific activation of mitogen-activated protein kinases (MAPK), interferon-regulated factors (IRF) and the transcription factor NF-κB through pattern recognition receptor signalling effectively induce inflammatory defence mechanisms. Unbalanced activation of these innate signalling pathways because of host genetic predispositions and/or the lack of adequate anti-inflammatory feedback mechanisms may turn a physiological response into a pathological situation including failure of bacterial clearance and development of chronic inflammation. Host-derived regulators from the immune and enteric nerve system crosstalk to the innate signalling network of the intestinal epithelium in order to shape the extent and duration of inflammatory processes. [ABSTRACT FROM AUTHOR]

Colorectal carcinoma (CRC) belongs to the most common tumor entities in western countries. Circulating tumor cells (CTC) in blood of CRC patients are a powerful prognostic and predictive biomarker. However, whether CTC-associated markers can also be used for early CRC detection and discrimination from benign diseases is not known. This study investigated the presence of CTC-associated markers CK20, PLS3, LAD1, and DEFA5 in blood of patients with benign inflammatory intestinal disease (IID) and their correlation with malignancy. The detection rate of CK20 and DEFA5 significantly differed between diseased patients and healthy controls. LAD1 and PLS3 were detected in all samples with clear differences in gene expression. DEFA5 expression was higher in CRC and IID patients compared to healthy donors, while CK20 and PLS3 were lower in CRC compared to IID patients or healthy controls. Overall, all CTC-associated markers were detectable in blood of IID patients, but not correlating with inflammation severity. Finally, PLS3 emerged as a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls, however its suitability for early CRC detection needs to be further validated.

Intestinal inflammatory disorders are associated with neurophysiological and behavioral symptoms. Conversely, many disorders of the central nervous system (CNS) are accompanied by intestinal complications. These observations suggest that intestinal and nervous system physiologies are functionally linked. Indeed, a growing body of literature has revealed multiple pathways mediating bidirectional communication between the intestine and the CNS, collectively referred to as the gut-brain axis. In particular, microbes naturally colonizing the mammalian gastrointestinal (GI) tract, termed the gut microbiota, not only correlate with but also play a causative role in regulating CNS function, development and host behavior. Despite these findings, our understanding of the cellular and molecular mechanisms that mediate gut-brain communication remains in its infancy. However, members of the gut microbiota have been established as potent modulators of intestinal, systemic and CNS-resident immune cell function, suggesting that gut-brain interactions may involve the host immune system. Multiple CNS disorders with gut microbiota associations, including neuroinflammatory, neuropsychiatric and neurodegenerative disorders, also have significant inflammatory manifestations. In this review, I discuss recent advances exploring the role of microbiota-immune interactions as a critical regulator of the gut-brain axis in the context of CNS and related disorders. [ABSTRACT FROM AUTHOR]

Background: Inflammatory bowel disease (IBD) associates with damage to the enteric nervous system (ENS), leading to gastrointestinal (GI) dysfunction. Oxidative stress is important for the pathophysiology of inflammation-induced enteric neuropathy and GI dysfunction. Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a dual functioning protein that is an essential regulator of the cellular response to oxidative stress. In this study, we aimed to determine whether an APE1/Ref-1 redox domain inhibitor, APX3330, alleviates inflammation-induced oxidative stress that leads to enteric neuropathy in the Winnie murine model of spontaneous chronic colitis., Methods: Winnie mice received APX3330 or vehicle via intraperitoneal injections over 2 weeks and were compared with C57BL/6 controls. In vivo disease activity and GI transit were evaluated. Ex vivo experiments were performed to assess functional parameters of colonic motility, immune cell infiltration, and changes to the ENS., Results: Targeting APE1/Ref-1 redox activity with APX3330 improved disease severity, reduced immune cell infiltration, restored GI function ,and provided neuroprotective effects to the enteric nervous system. Inhibition of APE1/Ref-1 redox signaling leading to reduced mitochondrial superoxide production, oxidative DNA damage, and translocation of high mobility group box 1 protein (HMGB1) was involved in neuroprotective effects of APX3330 in enteric neurons., Conclusions: This study is the first to investigate inhibition of APE1/Ref-1's redox activity via APX3330 in an animal model of chronic intestinal inflammation. Inhibition of the redox function of APE1/Ref-1 is a novel strategy that might lead to a possible application of APX3330 for the treatment of IBD., (© 2020 Crohn’s & Colitis Foundation. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Na-amino acid co-transporters (NaAAcT) are uniquely affected in rabbit intestinal villus cell brush border membrane (BBM) during chronic intestinal inflammation. Specifically, Na-alanine co-transport (ASCT1) is inhibited secondary to a reduction in the affinity of the co-transporter for alanine, whereas Na-glutamine co-transport (B0AT1) is inhibited secondary to a reduction in BBM co-transporter numbers. During chronic intestinal inflammation, there is abundant production of the potent oxidant peroxynitrite (OONO). However, whether OONO mediates the unique alteration in NaAAcT in intestinal epithelial cells during chronic intestinal inflammation is unknown. In this study, ASCT1 and B0AT1 were inhibited by OONO in vitro. The mechanism of inhibition of ASCT1 by OONO was secondary to a reduction in the affinity of the co-transporter for alanine, and secondary to a reduction in the number of co-transporters for B0AT1, which were further confirmed by Western blot analyses. In conclusion, peroxynitrite inhibited both BBM ASCT1 and B0AT1 in intestinal epithelial cells but by different mechanisms. These alterations in the villus cells are similar to those seen in the rabbit model of chronic enteritis. Therefore, this study indicates that peroxynitrite may mediate the inhibition of ASCT1 and B0AT1 during inflammation, when OONO levels are known to be elevated in the mucosa. [ABSTRACT FROM AUTHOR]

During chronic intestinal inflammation in rabbit intestinal villus cells brush border membrane (BBM) Na-glucose co-transport (SGLT1), but not Na/H exchange (NHE3) is inhibited. The mechanism of inhibition is secondary to a decrease in the number of BBM co-transporters. In the chronic enteritis mucosa, inducible nitric oxide (iNO) and superoxide production are known to be increased and together they produce abundant peroxynitrite (OONO), a potent oxidant. However, whether OONO mediates the SGLT1 and NHE3 changes in intestinal epithelial cells during chronic intestinal inflammation is unknown. Thus, we determined the effect of OONO on SGLT1 and NHE3 in small intestinal epithelial cell (IEC-18) monolayers grown on trans well plates. In cells treated with 100 μM SIN-1 (OONO donor) for 24 h, SGLT1 was inhibited while NHE3 activity was unaltered. SIN-1 treated cells produced 40 times more OONO fluorescence compared to control cells. Uric acid (1mM) a natural scavenger of OONO prevented the OONO mediated SGLT1 inhibition. Na+/K+-ATPase which maintains the favorable trans-cellular Na gradient for Na-dependent absorptive processes was decreased by OONO. Kinetics studies demonstrated that the mechanism of inhibition of SGLT1 by OONO was secondary to reduction in the number of co-transporters (Vmax) without an alteration in the affinity. Western blot analysis showed a significant decrease in SGLT1 protein expression. Further, p38 mitogen-activated protein (MAP) kinase pathway appeared to mediate the OONO inhibition of SGLT1. Finally, at the level of the co-transporter, 3-Nitrotyrosine formation appears to be the mechanism of inhibition of SGLT1. In conclusion, peroxynitrite inhibited BBM SGLT1, but not NHE3 in intestinal epithelial cells. These changes and the mechanism of SGLT1 inhibition by OONO in IEC-18 cells is identical to that seen in villus cells during chronic enteritis. Thus, these data indicate that peroxynitrite, known to be elevated in the mucosa, may mediate the inhibition of villus cell BBM SGLT1 in vivo in the chronically inflamed intestine. [ABSTRACT FROM AUTHOR]

Leukotriene D4 (LTD4) is an important immune inflammatory mediator that is known to be elevated in the mucosa of chronically inflamed intestine and alter nutrient absorption. LTD4 inhibits Na-alanine cotransport in intestinal epithelial cells by decreasing the affinity of the cotransporter ASCT1. LTD4 is known to increase intracellular Ca(++) and cAMP concentrations. However, the intracellular signaling mechanism of LTD4-mediated ASCT1 inhibition is unknown. In the present study, pretreatment with calcium chelator BAPTA-AM or inhibition of Ca(++)-dependent protein kinase C (PKC), specifically PKCα, resulted in the reversal of LTD4-mediated inhibition of ASCT1, revealing the involvement of the Ca(++)-activated PKC pathway. PKCα is known to phosphorylate Raf kinase inhibitor protein (RKIP), thus activating its downstream signaling pathway. Immunoblotting with anti-RKIP-Ser(153) antibody showed an increase in phosphorylation levels of RKIP in LTD4-treated cells. Downregulation of endogenous RKIP showed no decrease in ASCT1 activity by LTD4, thus confirming its involvement in ASCT1 regulation. Phosphorylation of RKIP by PKC is known to activate different signaling pathways, and in this study it was found to activate cAMP-activated protein kinase A (PKA) pathway. Although protein abundance of ASCT1 was not altered in any of the experimental conditions, there was an increase in the levels of phosphothreonine in ASCT1 protein, thus showing that phosphorylation changes were responsible for the altered affinity of ASCT1 by LTD4. In conclusion, LTD4 inhibits ASCT1 through PKC-mediated phosphorylation of RKIP, leading to the subsequent activation of PKA pathway, possibly through β2-andrenergic receptor activation., (Copyright © 2014 the American Physiological Society.)