Maintenance Of Intestinal Homeostasis Research Articles

Gut microecology: An important target of traditional Chinese medicine in the treatment of nonalcoholic fatty liver disease

Gut microecology plays an important role in the pathogenesis of nonalcoholic fatty liver disease. With reference to the research on traditional Chinese medicine in regulating gut microecology and treating nonalcoholic fatty liver disease,this article systematically elaborates on the association of nonalcoholic fatty liver disease with intestinal flora,gut bacterial metabolites,and gut barrier function and points out that the regulation of gut microecology and the maintenance of intestinal homeostasis are important measures for traditional Chinese medicine in the treatment of nonalcoholic fatty liver disease.

Establishment and Characterization of a Murine Mucosal Mast Cell Culture Model.

Accumulating evidence suggests that mast cells play critical roles in disruption and maintenance of intestinal homeostasis, although it remains unknown how they affect the local microenvironment. Interleukin-9 (IL-9) was found to play critical roles in intestinal mast cell accumulation induced in various pathological conditions, such as parasite infection and oral allergen-induced anaphylaxis. Newly recruited intestinal mast cells trigger inflammatory responses and damage epithelial integrity through release of a wide variety of mediators including mast cell proteases. We established a novel culture model (IL-9-modified mast cells, MCs/IL-9), in which murine IL-3-dependent bone-marrow-derived cultured mast cells (BMMCs) were further cultured in the presence of stem cell factor and IL-9. In MCs/IL-9, drastic upregulation of Mcpt1 and Mcpt2 was found. Although histamine storage and tryptase activity were significantly downregulated in the presence of SCF and IL-9, this was entirely reversed when mast cells were cocultured with a murine fibroblastic cell line, Swiss 3T3. MCs/IL-9 underwent degranulation upon IgE-mediated antigen stimulation, which was found to less sensitive to lower concentrations of IgE in comparison with BMMCs. This model might be useful for investigation of the spatiotemporal changes of newly recruited intestinal mast cells.

Autophagy deficiency exacerbates colitis through excessive oxidative stress and MAPK signaling pathway activation.

Background and aimAutophagy is an essential process involved in the pathogenesis of inflammatory bowel disease (IBD). Although there are many data showing the roles of autophagy in intestinal epithelial cells (IECs), the mechanisms involved remain to be fully elucidated. We investigated the influence of autophagy in IECs on gastrointestinal tract inflammation.MethodsMice with conditional knockout of Atg5 in IECs (Atg5flox/flox/villin-Cre mice) were subjected to dextran sulfate sodium (DSS)-induced colitis and analyzed for colitis susceptibility. Additionally, we used Atg5-silenced rat IECs (IEC6shAtg5 cells) for in vitro assays.ResultsSensitivity to DSS markedly increased in Atg5flox/flox/villin-Cre mice compared to that in wild-type mice. In IEC6shAtg5 cells, apoptosis was enhanced, and cell viability significantly decreased compared to IEC-6 cells. The expression of proinflammatory cytokines increased upon suppression of autophagy. Furthermore, silencing of Atg5 was associated with inflammation of IECs, activation of the mitogen-activated protein kinase (MAPK) signaling pathway by the intracellular reactive oxygen species accumulation, and NF-κB p65 phosphorylation.ConclusionsAutophagy in IECs plays an essential role in the maintenance of intestinal homeostasis, and autophagy deficiency triggers inflammation. Development of methods targeting autophagy might be beneficial in the treatment of IBD.

Oral delivery of pancreatitis-associated protein by Lactococcus lactis displays protective effects in dinitro-benzenesulfonic-acid-induced colitis model and is able to modulate the composition of the microbiota.

SummaryAntimicrobial peptides secreted by intestinal immune and epithelial cells are important effectors of innate immunity. They play an essential role in the maintenance of intestinal homeostasis by limiting microbial epithelium interactions and preventing unnecessary microbe‐driven inflammation. Pancreatitis‐associated protein (PAP) belongs to Regenerating islet‐derived III proteins family and is a C‐type (Ca+2 dependent) lectin. PAP protein plays a protective effect presenting anti‐inflammatory properties able to reduce the severity of colitis, preserving gut barrier and epithelial inflammation. Here, we sought to determine whether PAP delivered at intestinal lumen by recombinant Lactococcus lactis strain (LL‐PAP) before and after chemically induced colitis is able to reduce the severity in two models of colitis. After construction and characterization of our recombinant strains, we tested their effects in dinitro‐benzenesulfonic‐acid (DNBS) and Dextran sulfate sodium (DSS) colitis model. After the DNBS challenge, mice treated with LL‐PAP presented less severe colitis compared with PBS and LL‐empty‐treated mice groups. After the DSS challenge, no protective effects of LL‐PAP could be detected. We determined that after 5 days administration, LL‐PAP increase butyrate producer's bacteria, especially Eubacterium plexicaudatum. Based on our findings, we hypothesize that a treatment with LL‐PAP shifts the microbiota preventing the severity of colon inflammation in DNBS colitis model. These protective roles of LL‐PAP in DNBS colitis model might be through intestinal microbiota modulation.

Tamoxifen-induced, intestinal-specific deletion of Slc5a6 in adult mice leads to spontaneous inflammation: involvement of NF-κB, NLRP3, and gut microbiota.

The sodium-dependent multivitamin transporter (SMVT; SLC5A6) is involved in intestinal absorption of vitamin B7 (biotin). We have previously shown that mice with an embryonic intestinal-specific SMVT knockout (KO) develop biotin deficiency and severe spontaneous intestinal inflammation in addition to growth retardation, developmental delays, and death within the first 6-7 wk of life. The profound morbidity and mortality associated with the SMVT-KO has limited our ability to further characterize the intestinal inflammation and other sequelae of this deletion in adult mice with a mature gut microbiota. To overcome this limitation, we generated an intestine-specific, tamoxifen-inducible, conditional SMVT-KO (SMVT-icKO). Our results showed that adult SMVT-icKO mice have reduced body weight, biotin deficiency, shorter colonic length, and bloody diarrhea compared with age- and sex-matched control littermates. All SMVT-icKO mice also developed spontaneous intestinal inflammation associated with induction of calprotectin (S100a8/S100a9), proinflammatory cytokines (IL-1β, TNF-α, IFN-γ, and IL-6), and an increase in intestinal permeability. Additionally, the intestines of SMVT-icKO showed activation of the NF-κB pathway and the nucleotide-binding domain and leucine-rich repeat pyrin 3 domain (NLRP3) inflammasome. Notably, administration of broad-spectrum antibiotics reduced lethality and led to normalization of intestinal inflammation, proinflammatory cytokines, altered mucosal integrity, and reduced expression of the NLRP3 inflammasome. Overall, these findings support our conclusion that the biotin transport pathway plays an important role in the maintenance of intestinal homeostasis, and that NF-κB and the NLRP3 inflammasome, as well as gut microbiota, drive the development of intestinal inflammation when SMVT is absent.NEW & NOTEWORTHY This study demonstrates that deletion of the intestinal biotin uptake system in adult mice leads to the development of spontaneous gut inflammation and that luminal microbiota plays a role in its development.

Abstract 1771: Role of Tsc2-mTORC1 signaling in homeostasis of intestinal epithelium and its relation to inflammation and cancer

Abstract Intestinal tumorigenesis driven by mutations in adenomatous polyposis coli gene requires the mammalian target of rapamycin complex 1 (mTORC1) activity, whereas the physiological roles of mTORC1 in the homeostasis of intestinal epithelial cells (IECs) remain virtually unknown. We here generated mice, in which tuberous sclerosis complex 2 (Tsc2), a negative regulator of mTORC1, was specifically ablated in IECs (Tsc2 CKO mice). Tsc2 CKO mice manifested the enhanced proliferative activity of IECs in intestinal crypts as well as the promoted migration of these cells along the crypt-villus axis. In vitro study showed that conditional ablation of Tsc2 in IECs promoted development of intestinal organoids, while mTORC1 inhibitor, rapamycin, diminished this phenotype. Tsc2 CKO mice also manifested the increased apoptotic rate of IECs as well as the increased ectopic Paneth cells, which are one of the major differentiated IECs. In addition, such conditional ablation of Tsc2 resulted in a suppressed expression of Wnt target genes in the colonic epithelium. Finally, we found that Tsc2 CKO mice manifested the increased susceptibility for dextran sulfate sodium (DSS)-induced colitis. Although mTORC1 and Wnt signaling pathways are thought to cooperated to promote oncogenesis in the intestinal epithelium, our results thus suggest that the mTORC1 signaling unexpectedly counter-regulates the Wnt signaling with the maintenance of intestinal homeostasis. Citation Format: Takenori Kotani, Jajar Setiawan, Yoji Murata, Yasuyuki Saito, Takashi Matozaki. Role of Tsc2-mTORC1 signaling in homeostasis of intestinal epithelium and its relation to inflammation and cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1771.

Microbiota metabolites SCFA stimulate epithelial migration to promote wound healing through MFGE8 and PAK1

Abstract How microbiota regulate intestinal homeostasis is still not completely understood. Emerging evidence indicates that gut microbiota metabolites play crucial roles in maintenance of intestinal homeostasis and regulation of Inflammatory Bowel Disease (IBD). Many patients with IBD are deficient in the microbial metabolites of dietary fibers, short chain fatty acids (SCFAs). To date, the evidence for use of SCFAs as a treatment for IBD has been inconsistent, highlighting the need for further investigation. In this study, we demonstrate that SCFAs promote intestinal epithelial cell (IEC) wound healing. Treatment of mouse and human IEC in vitro with the SCFAs acetate, propionate, and butyrate enhanced wound closure by promoting cell migration, which was independent of cell proliferation. Further analysis of random cell migration revealed that SCFAs increased cell speed, cell persistence, and consequently mean squared displacement. To investigate the mechanism of enhanced migration, we performed microarray of mouse-derived enteroids, which identified p21 activated kinase 1 (PAK1) and milk fat globule-EGF factor 8 (MFGE8), two genes implicated in tissue repair and motility, to be highly upregulated. We confirmed upregulation of MFGE8 and PAK1 via qRT-PCR and western blot. Inhibition of PAK1 and CRISPR knockout of MFGE8 abrogated the effects of SCFAs on migration. Lastly, the above effects were dependent upon SCFAs inhibition of histone deacetylases (HDAC), as treatment of IECs with the HDAC inhibitor, trichostatin A, fully recapitulated the effects of SCFAs on migration and expression of MFGE8 and PAK1. These findings elucidate a pathway in which SCFAs inhibition of histone deacetylases may enhance wound healing in IBD.

Group 3 ILCs: Peacekeepers or Troublemakers? What's Your Gut Telling You?!

A complex network of interactions exists between the microbiome, the epithelium, and immune cells that reside along the walls of the gastrointestinal tract. The intestinal immune system has been assigned with the difficult task of discriminating between commensal, harmless bacteria, and invading pathogens that translocate across the epithelial monolayer. Importantly, it is trained to maintain tolerance against commensals, and initiate protective immune responses against pathogens to secure intestinal homeostasis. Breakdown of this fine balance between the host and its intestinal microbiota can lead to intestinal inflammation and subsequently to development of inflammatory bowel disease (IBD). A decade since their discovery, innate lymphoid cells (ILCs) are now recognized as important regulators of intestinal homeostasis. ILC3s have emerged as a critical subset in the gut. They are the most phenotypically diverse ILC population and interact directly with numerous different cell types (haematopoietic and non-haematopoeitic), as well as interface with the bacterial flora. In addition to their contribution to intestinal pathogen immunity, they also mitigate against tissue damage occurring following acute injury, by facilitating tissue repair and regeneration, a key function in the maintenance of intestinal homeostasis. However, in chronic inflammation the tables are turned and ILC3s may acquire a pro-inflammatory phenotype in the gut. Chronic ILC activation can lead to persistent inflammation contributing to IBD and/or colorectal cancer. In this review, we discuss current knowledge of group 3 ILCs and their contributions to intestinal homeostasis and disease leading to novel therapeutic targets and clinical approaches that may inform novel treatment strategies for immune-mediated disorders, including IBD.

The Impact of Chronic Intestinal Inflammation on Brain Disorders: the Microbiota-Gut-Brain Axis.

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.

Differential Responses of Colorectal Cancer Cell Lines to Enterococcus faecalis' Strains Isolated from Healthy Donors and Colorectal Cancer Patients.

The metabolites produced by the host’s gut microbiota have an important role in the maintenance of intestinal homeostasis, but can also act as toxins and induce DNA damage in colorectal epithelial cells increasing the colorectal cancer (CRC) chance. In this scenario, the impact of some of the components of the natural human gastrointestinal microbiota, such as Enterococcus faecalis (E. faecalis), at the onset of CRC progression remains controversial. Since under dysbiotic conditions it could turn into a pathogen, the aim of this study was to compare the effect of E. faecalis’ strains (isolated from CRC patients and healthy subjects’ stools) on the proliferation of different colorectal cells lines. First, we isolated and genotyping characterized the Enterococcus faecalis’ strains. Then, we analyzed the proliferation index (by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay) of three tumor and one normal intestinal cell lines, previously exposed to E. faecalis strains pre-cultured medium. Stool samples of CRC patients demonstrated a reduced frequency of E. faecalis compared to healthy subjects. In addition, the secreted metabolites of E. faecalis’ strains, isolated from healthy donors, decreased the human ileocecal adenocarcinoma cell line HCT-8 and human colon carcinoma cell line HCT-116 cell proliferation without effects on human colorectal adenocarcinoma cell line SW620 and on normal human diploid cell line CLR-1790. Notably, the metabolites of the strains isolated from CRC patients did not influence the cell growth of CRC cell lines. Our results demonstrated a new point of view in the investigation of E. faecalis’ role in CRC development, which raises awareness of the importance of not only associating the presence/absence of a unique microorganism, but also in defining the specific characteristics of the different investigated strains.

Epigenetic regulation of T helper cells and intestinal pathogenicity.

Inflammatory bowel diseases (IBDs) are characterized by relapsing and remitting chronic intestinal inflammation. Previous studies have demonstrated the contributions of genetic background, environmental factors (food, microbiota, use of antibiotics), and host immunity in the development of IBDs. More than 200 genes have been shown to influence IBD susceptibility, most of which are involved in immunity. The vertebrate immune system comprises a complex network of innate and adaptive immune cells that protect the host from infection and cancer. Dysregulation of the mutualistic relationship between the immune system and the gut environment results in IBD. Considering the fundamental role of epigenetic regulation in immune cells, epigenetic mechanisms, particularly in T helper (Th) cells, may play a major role in the complex regulation of mucosal immunity. Epigenetic regulation and dysregulation of Th cells are involved in the maintenance of intestinal homeostasis and its breakdown in IBD.

Functions of Macrophages in the Maintenance of Intestinal Homeostasis.

Intestinal macrophages constitute the largest pool of macrophages in the body and have emerged as crucial sentinels for pathogen recognition and elimination. The source and development of intestinal macrophages, as well as their distinct properties have been well documented. Intestinal macrophages exert their functions in the maintenance of intestinal homeostasis by shaping host-microbiota symbiosis, managing gut inflammation, crosstalking with T cells, and facilitating wound repair. Recently, nutritional regulation of intestinal macrophages has attracted substantial attention and is becoming a promising approach to disease prevention and control. Understanding the mechanisms employed by intestinal macrophages in mediating intestinal immune homeostasis and inflammation, as well as the mode of action of dietary nutrients in the modulating functions of intestinal macrophages, represents an opportunity to prevent and control inflammatory bowel diseases.

Indispensable role of the Ubiquitin-fold modifier 1-specific E3 ligase in maintaining intestinal homeostasis and controlling gut inflammation

Intestinal exocrine secretory cells, including Paneth and goblet cells, have a pivotal role in intestinal barrier function and mucosal immunity. Dysfunction of these cells may lead to the pathogenesis of human diseases such as inflammatory bowel disease (IBD). Therefore, identification and elucidation of key molecular mechanisms that regulate the development and function of these exocrine cells would be crucial for understanding of disease pathogenesis and discovery of new therapeutic targets. The Ufm1 conjugation system is a novel ubiquitin-like modification system that consists of Ufm1 (Ubiquitin modifier 1), Uba5 (Ufm1-activating enzyme, E1), Ufc1 (Ufm1-conjugating enzyme, E2) and poorly characterized Ufm1 E3 ligase(s). Recent mouse genetic studies have demonstrated its indispensable role in embryonic development and hematopoiesis. Yet its role in other tissues and organs remains poorly defined. In this study, we found that both Ufl1 and Ufbp1, two key components of the Ufm1 E3 ligase, were highly expressed in the intestinal exocrine cells. Ablation of either Ufl1 and Ufbp1 led to significant loss of both Paneth and goblet cells, which in turn resulted in dysbiotic microbiota and increased susceptibility to experimentally induced colitis. At the cellular and molecular levels, Ufbp1 deficiency caused elevation of endoplasmic reticulum stress and activation of the Unfolded Protein Response (UPR) and cell death program. Administration of small molecular chaperone partially prevented loss of Paneth cells caused by acute Ufbp1 deletion. Taken together, our results have provided unambiguous evidence for the crucial role of the Ufm1 E3 ligase in maintenance of intestinal homeostasis and protection from inflammatory diseases.

Roles of Autophagy-Related Genes in the Pathogenesis of Inflammatory Bowel Disease.

Autophagy is an intracellular catabolic process that is essential for a variety of cellular responses. Due to its role in the maintenance of biological homeostasis in conditions of stress, dysregulation or disruption of autophagy may be linked to human diseases such as inflammatory bowel disease (IBD). IBD is a complicated inflammatory colitis disorder; Crohn’s disease and ulcerative colitis are the principal types. Genetic studies have shown the clinical relevance of several autophagy-related genes (ATGs) in the pathogenesis of IBD. Additionally, recent studies using conditional knockout mice have led to a comprehensive understanding of ATGs that affect intestinal inflammation, Paneth cell abnormality and enteric pathogenic infection during colitis. In this review, we discuss the various ATGs involved in macroautophagy and selective autophagy, including ATG16L1, IRGM, LRRK2, ATG7, p62, optineurin and TFEB in the maintenance of intestinal homeostasis. Although advances have been made regarding the involvement of ATGs in maintaining intestinal homeostasis, determining the precise contribution of autophagy has remained elusive. Recent efforts based on direct targeting of ATGs and autophagy will further facilitate the development of new therapeutic opportunities for IBD.

Microbial-Driven Butyrate Regulates Jejunal Homeostasis in Piglets During the Weaning Stage

Microbe-derived butyrate plays an important role in the gut health of young mammals during the weaning stage. A greater understanding of how butyrate regulates intestinal development is necessary for overcoming post-weaning diarrheal diseases. We aimed to investigate whether jejunal microbial metabolite butyrate modulates the apoptosis/proliferation balance and immune response in piglets during the post-weaning period of the first 3 weeks of life. On the one hand, during the first week post-weaning, the relative abundances of the dominant bacterial families Erysipelotrichaceae (P < 0.01) and Lachnospiraceae (P < 0.01) were increased, which induced decreases in both butyrate production (P < 0.05) and its receptor (G-protein coupled receptor 43) expression (P < 0.01). The resulting intestinal inflammation (inferred from increased TNF-α and IFN-γ expression) contributed to the onset of cell apoptosis and the inhibition of cell-proliferation along the crypt-villus axis, which were followed by impaired jejunal morphology (i.e., increased crypt-depth) (P < 0.05) and intestinal dysfunction (i.e., decreased creatine kinase, and lactate dehydrogenase) (P < 0.05). On the other hand, during the second week post-weaning, the relative abundances of Lactobacillaceae (P < 0.01) and Ruminococcaceae (P < 0.05) were increased. The increases were accompanied by increased butyrate production (P < 0.05) and its receptor expression (P < 0.01), leading to the inhibition of cell apoptosis and the stimulation of cell proliferation via decreased pro-inflammatory cytokines and thereby the improvement of intestinal development and function. Herein, this study demonstrates that microbial-driven butyrate might be a key modulator in the maintenance of intestinal homeostasis after weaning. The findings suggest that strategies to promote butyrate production can maintain the apoptosis/proliferation balance via minimizing intestinal inflammation, and thereby improving post-weaning jejunal adaptation toward gut health.

Bacillus amyloliquefaciens Ameliorates Dextran Sulfate Sodium-Induced Colitis by Improving Gut Microbial Dysbiosis in Mice Model.

Several Bacillus strains exert beneficial effects on the maintenance of intestinal homeostasis and host health. However, whether Bacillus amyloliquefaciens (BA) can improve gut microbial dysbiosis and ameliorate colitis is unknown. Therefore, we conducted the present study to investigate the effects of BA administration on intestinal morphology, inflammatory response, and colonic microbial composition in a mouse model of dextran sulfate sodium (DSS)-induced colitis. Results showed that BA administration significantly ameliorated body weight loss, decreased disease activity index, and improved colonic tissue morphology in DSS-treated mice. In addition, levels of immunoglobulins, as well as pro-inflammatory cytokines, were decreased after BA administration. Importantly, colonic microbiota profiling indicated a significant (p < 0.05) difference in beta-diversity between BA-administrated and DSS-treated mice, according to weighted principal coordinate analysis (PCoA) results. The relative abundance of the Firmicutes genus was increased, whereas that of Bacteroidetes was decreased by BA administration. Furthermore, phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) analysis showed that the most significantly changed pathways between the four groups of mice were carbohydrate, lipid, and amino acid metabolism. In conclusion, our results showed that BA administration has beneficial effects on DSS-induced colitis, suggesting that this strategy might be useful for the treatment of dysbiosis during ulcerative colitis. Further, the changes in metabolism, especially amino acid metabolism, might contribute to the beneficial effects of BA on the amelioration of DSS-induced colitis.

Origin, Differentiation, and Function of Intestinal Macrophages.

Macrophages are increasingly recognized as essential players in the maintenance of intestinal homeostasis and as key sentinels of the intestinal immune system. However, somewhat paradoxically, they are also implicated in chronic pathologies of the gastrointestinal tract, such as inflammatory bowel disease (IBD) and are therefore considered potential targets for novel therapies. In this review, we will discuss recent advances in our understanding of intestinal macrophage heterogeneity, their ontogeny and the potential factors that regulate their origin. We will describe how the local environment of the intestine imprints the phenotypic and functional identity of the macrophage compartment, and how this changes during intestinal inflammation and infection. Finally, we highlight key outstanding questions that should be the focus of future research.

Dual-specificity phosphatase 6 deletion protects the colonic epithelium against inflammation and promotes both proliferation and tumorigenesis.

The Ras/mitogen‐activated protein kinase (MAPK) pathway controls fundamental cellular processes such as proliferation, differentiation, and apoptosis. The dual‐specificity phosphatase 6 (DUSP6) regulates cytoplasmic MAPK signaling by dephosphorylating and inactivating extracellular signal‐regulated kinase (ERK1/2) MAPK. To determine the role of DUSP6 in the maintenance of intestinal homeostasis, we characterized the intestinal epithelial phenotype of Dusp6 knockout (KO) mice under normal, oncogenic, and proinflammatory conditions. Our results show that loss of Dusp6 increased crypt depth and epithelial cell proliferation without altering colonic architecture. Crypt regeneration capacity was also enhanced, as revealed by ex vivo Dusp6 KO organoid cultures. Additionally, loss of Dusp6 induced goblet cell expansion without affecting enteroendocrine and absorptive cell differentiation. Our data also demonstrate that Dusp6 KO mice were protected from acute dextran sulfate sodium‐induced colitis, as opposed to wild‐type mice. In addition, Dusp6 gene deletion markedly enhanced tumor load in Apc Min/+ mice. Decreased DUSP6 expression by RNA interference in HT29 colorectal cancer cells enhanced ERK1/2 activation levels and promoted both anchorage‐independent growth in soft agar as well as invasion through Matrigel. Finally, DUSP6 mRNA expression in human colorectal tumors was decreased in advanced stage tumors compared with paired normal tissues. These results demonstrate that DUSP6 phosphatase, by controlling ERK1/2 activation, regulates colonic inflammatory responses, and protects the intestinal epithelium against oncogenic stress.

Peyer's patches-derived CD11b+ B cells recruit regulatory T cells through CXCL9 in dextran sulphate sodium-induced colitis.

Regulatory T (Treg) cells play an essential role in the maintenance of intestinal homeostasis. In Peyer's patches (PPs), which comprise the most important IgA induction site in the gut-associated lymphoid tissue, Treg cells promote IgA isotype switching. However, the mechanisms underlying their entry into PPs and isotype switching facilitation in activated B cells remain unknown. This study, based on the dextran sulphate sodium (DSS)-induced colitis model, revealed that Treg cells are significantly increased in PPs, along with CD11b+ B-cell induction. Immunofluorescence staining showed that infiltrated Treg cells were located around CD11b+ B cells and produced transforming growth factor-β, thereby inducing IgA+ B cells. Furthermore, in vivo and in vitro studies revealed that CD11b+ B cells in PPs had the capacity to recruit Treg cells into PPs rather than promoting their proliferation. Finally, we found that Treg cell recruitment was mediated by the chemokine CXCL9 derived from CD11b+ B cells in PPs. These findings demonstrate that CD11b+ B cells induced in PPs during colitis actively recruit Treg cells to accomplish IgA isotype switch in a CXCL9-dependent manner.

Faecal Microbiota Transplantation Reduces Susceptibility to Epithelial Injury and Modulates Tryptophan Metabolism of the Microbial Community in a Piglet Model.

Faecal microbiota transplantation [FMT] has shown promise as a treatment for inflammatory bowel disease [IBD]. Using a piglet model, our previous study indicated that exogenous faecal microbiota can increase the expressions of tight junction proteins, mucin and antimicrobial peptide in the intestinal mucosa, suggesting a beneficial effect of FMT on gut barrier and gastrointestinal health. However, specific connections between FMT-induced microbial changes and modulation of the intestinal barrier remain to be fully illustrated. Here, we aimed to determine the potential role of metabolic function of gut microbiota in the beneficial effects of FMT. The influence of FMT on the maintenance of intestinal homeostasis was assessed by early-life gut microbiota intervention on newborn piglets and subsequent lipopolysaccharide [LPS] challenge. Analysis of the gut microbiome and metabolome was carried out by 16S rRNA gene sequencing and multiple mass spectrometry platforms. FMT modulated the diversity and composition of colonic microbiota and reduced the susceptibility to LPS-induced destruction of epithelial integrity and severe inflammatory response. Metabolomic analysis revealed functional changes of the gut metabolome along with a significant increase of the typical microbiota-derived tryptophan catabolite indole-3-acetic acid in the colonic lumen. In concordance with the metabolome data, metagenomics prediction analysis based on 16S rRNA gene sequencing also demonstrated that FMT modulated the metabolic functions of gut microbiota associated with indole alkaloid biosynthesis, cytochrome P450 and intestinal homeostasis, which coincided with up-regulation of cytokine interleukin-22 and enhanced activation of aryl hydrocarbon receptor in the recipient colon. Our data reveal a regulatory effect of FMT on tryptophan metabolism of gut microbiota in the recipient colon, which may play a potential role in maintenance of the intestinal barrier.