American journal of physiology. Gastrointestinal and liver physiology最新文献

Functional loss of the motor protein myosin Vb (MYO5B) induces various defects in intestinal epithelial function and causes a congenital diarrheal disorder, namely, microvillus inclusion disease (MVID). Utilizing the MVID model mice Vil1-Cre^ERT2;Myo5b^flox/flox (MYO5BΔIEC) and Vil1-Cre^ERT2;Myo5b^flox/G519R [MYO5B(G519R)], we previously reported that functional MYO5B loss disrupts progenitor cell differentiation and enterocyte maturation that result in villus blunting and deadly malabsorption symptoms. In this study, we determined that both absence and a point mutation of MYO5B impair lipid metabolism and alter mitochondrial structure, which may underlie the progenitor cell malfunction observed in the MVID intestine. Along with a decrease in fatty acid oxidation, the lipogenesis pathway was enhanced in the MYO5BΔIEC small intestine. Consistent with these observations in vivo, RNA sequencing of enteroids generated from the two MVID mouse strains showed similar downregulation of energy metabolic enzymes, including mitochondrial oxidative phosphorylation genes. In our previous studies, we reported that lysophosphatidic acid (LPA) signaling ameliorated epithelial cell defects in MYO5BΔIEC tissues and enteroids. The present study demonstrated that the highly soluble LPA receptor (LPAR)5-preferred agonist Compound-1 improved sodium transporter localization and absorptive function and tuft cell differentiation in patient-modeled MVID animals that carry independent mutations in MYO5B. Body weight loss in male MYO5B(G519R) mice was ameliorated by Compound-1. These observations suggest that Compound-1 treatment has a trophic effect on the intestine with MYO5B functional loss through epithelial cell-autonomous pathways that can accelerate the differentiation of progenitor cells and the maturation of enterocytes. Targeting LPAR5 may represent an effective therapeutic approach for the treatment of MVID symptoms induced by different point mutations in MYO5B.NEW & NOTEWORTHY This study demonstrates the importance of MYO5B for cellular lipid metabolism and mitochondria in intestinal epithelial cells, previously unexplored functions of MYO5B. The alterations may underlie the progenitor cell malfunction observed in microvillus inclusion disease (MVID) intestines. To examine the therapeutic potential of progenitor-targeted treatments, the effects of the LPAR5-preferred agonist Compound-1 were investigated utilizing several MVID model mice and enteroids. Our observations suggest that Compound-1 may provide a therapeutic approach for treating MVID.

The enteric nervous system (ENS) continues to be exposed to various disturbances throughout life, which causes apoptosis in the ENS. Therefore, it is assumed that neurogenesis is induced to maintain the neuronal network in the adult ENS. However, these underlying mechanisms are largely unknown. We aimed to investigate adult neurogenesis in the DSS-induced colitis mouse colon.

Methods: male C57BL/6N mice (12-week-old) were administered 2% DSS in their drinking water for 8 days. After DSS treatment, cross-sections and longitudinal muscle and myenteric plexus preparations from the colon were used for immunohistochemistry. The segments of colons were mounted in organ baths and then exposed to a voltage-gated sodium channel activator veratridine.

Results: in the motility study, veratridine-induced colonic contractions were significantly suppressed in DSS-induced colitis mice compared to normal mice. Immunohistochemical analyses revealed that the proportion of nitrergic neurons per ganglion was significantly increased in the colons of DSS-induced colitis mice compared to normal mice. Furthermore, the proportion of Sox2 (new-born neuron marker)-positive neurons per ganglion was not significantly different between normal mice and DSS-induced colitis mice, whereas the proportion of Sox2-positive nitrergic neurons to Sox2-positive neurons per ganglion was significantly increased in the colons of DSS-induced colitis mice compared to normal mice. In addition, NOS inhibitor significantly enhanced veratridine-induced colonic contractions in DSS-induced colitis mice compared with normal mice.

Conclusions: these findings suggested that colitis caused an imbalance in the enteric neural circuit composed of excitatory neurons and inhibitory neurons in the myenteric plexus of the colon, which resulted in colonic dysmotility.

Background and aims: Chronic pancreatitis (CP) is a fibro-inflammatory disease of the pancreas with no specific cure. Research highlighting the pathogenesis and especially the therapeutic aspect remains limited. Aberrant activation of developmental pathways in adults have been implicated in several diseases. Hedgehog pathway is a notable embryonic signaling pathway, known to promote fibrosis of various organs when over-activated. The aim of this study is to explore the role of hedgehog pathway in the progression of CP and evaluate its inhibition as a novel therapeutic strategy against CP.

Methods: CP was induced in mice by repeated injections of L-arginine or Caerulein in two separate models. Mice were administered with the FDA approved pharmacological hedgehog pathway inhibitor, Vismodegib during or after establishing the disease condition to inhibit hedgehog signaling. Various parameters of CP were analyzed to determine the effect of hedgehog pathway inhibition on the severity and progression of the disease.

Results: Our study shows that hedgehog signaling was over-activated during CP and its inhibition was effective in improving the histopathological parameters associated with CP. Vismodegib administration not only halted the progression of CP but was also able to resolve already established fibrosis. Additionally, inhibition of hedgehog signaling resulted in reversal of pancreatic stellate cell activation ex vivo. Conclusions: Findings from our study justify conducting clinical trials using Vismodegib against CP and thus, could lead to development of novel therapeutic strategy for the treatment of CP.

Total parenteral nutrition (TPN) provides lifesaving nutritional support intravenously; however, it is associated with significant side effects. Given gut microbial alterations noted with TPN, we hypothesized that transferring fecal microbiota from healthy controls would restore gut-systemic signaling in TPN and mitigate injury. Using our novel ambulatory model (US Patent: US 63/136,165), 31 piglets were randomly allocated to enteral nutrition (EN), TPN only, TPN + antibiotics (TPN-A), or TPN + intraduodenal fecal microbiota transplant (TPN + FMT) for 14 days. Gut, liver, and serum were assessed through histology, biochemistry, and qPCR. Stool samples underwent 16 s rRNA sequencing. Permutational multivariate analysis of variance, Jaccard, and Bray-Curtis metrics were performed. Significant bilirubin elevation in TPN and TPN-A versus EN (P < 0.0001) was prevented with FMT. IFN-G, TNF-α, IL-β, IL-8, and lipopolysaccharide (LPS) were significantly higher in TPN (P = 0.009, P = 0.001, P = 0.043, P = 0.011, P < 0.0001), with preservation upon FMT. Significant gut atrophy by villous-to-crypt ratio in TPN (P < 0.0001) and TPN-A (P = 0.0001) versus EN was prevented by FMT (P = 0.426 vs. EN). Microbiota profiles using principal coordinate analysis demonstrated significant FMT and EN overlap, with the largest separation in TPN-A followed by TPN, driven primarily by Firmicutes and Fusobacteria. TPN-altered gut barrier was preserved upon FMT; upregulated cholesterol 7 α-hydroxylase and bile salt export pump in TPN and TPN-A and downregulated fibroblast growth factor receptor 4, EGF, farnesoid X receptor, and Takeda G Protein-coupled Receptor 5 (TGR5) versus EN was prevented by FMT. This study provides novel evidence of prevention of gut atrophy, liver injury, and microbial dysbiosis with intraduodenal FMT, challenging current paradigms into TPN injury mechanisms and underscores the importance of gut microbes as prime targets for therapeutics and drug discovery.NEW & NOTEWORTHY Intraduodenal fecal microbiota transplantation presents a novel strategy to mitigate complications associated with total parenteral nutrition (TPN), highlighting gut microbiota as a prime target for therapeutic and diagnostic approaches. These results from a highly translatable model provide hope for TPN side effect mitigation for thousands of chronically TPN-dependent patients.

The gut microbiome plays a critical role in the development, progression, and treatment of cancer. As interest in microbiome-immune-cancer interactions expands, the prevalence of fecal microbial transplant (FMT) models has increased proportionally. However, current literature does not provide adequate details or consistent approaches to allow for necessary rigor and experimental reproducibility. In this review, we evaluate key studies using FMT to investigate the relationship between the gut microbiome and various types of cancer. In addition, we will discuss the common pitfalls of these experiments and methods for improved standardization and validation as the field uses FMT with greater frequency. Finally, this review focuses on the impacts of the gut and extraintestinal microbes, prebiotics, probiotics, and postbiotics in cancer risk and response to therapy across a variety of tumor types.NEW & NOTEWORTHY The microbiome impacts the onset, progression, and therapy response of certain types of cancer. Fecal microbial transplants (FMTs) are an increasingly prevalent tool to test these mechanisms that require standardization by the field.

In this study, we uncovered the novel mechanism of IL-1α-mediated downregulated in adenoma (DRA) (SLC26A3) downregulation in the context of Brachyspira spp.-induced malabsorptive diarrhea. Experimentally infected pigs with Brachyspira spp. had significantly reduced DRA expression in the colon accompanied by IL-1α upregulation. This response was recapitulated in vitro by exposing Caco-2 cells to either Brachyspira lysate or IL-1α. Both p38 and MAPK-activated protein kinase 2 (MAPKAPK-2 also referred as MK-2) showed an increased phosphorylation after exposure to either. SB203580 application, a p38 inhibitor blocked the MK-2 phosphorylation and attenuated the DRA and IL-1α response to both lysate and IL-1α. Exposure to IL-1 receptor antagonist (IL-1RA) produced a similar response. In addition, exposure of cells to either of these blockers without IL-1α or lysate results in increased DRA and decreased IL-1α expression, revealing that DRA needs IL-1α signaling for basal physiological expression. Dual inhibition with both blockers completely inhibited the effect from IL-1α while significantly attenuating the response from Brachyspira lysate, suggesting a minor contribution from another pathway. Together this demonstrates that Brachyspira activates p38 MAPK signaling driving IL-1α expression, which activates IL-1R1 causing DRA downregulation while also driving upregulation of IL-1α through p38 in a positive feedback mechanism. In conclusion, we elucidated a major pathway involved in DRA downregulation and its role in Brachyspira-induced diarrhea. In addition, these observations will aid in our understanding of other inflammatory and infectious diarrhea conditions.NEW & NOTEWORTHY The diarrheal disease caused by the two infectious spirochete spp. B. hyodysenteriae and B. hampsonii reduced the expression of DRA (SLC26A3), a major Cl^-/HCO^-₃ exchanger involved in Cl^- absorption. This is attributed to the upregulation of IL-1α driven by p38 MAPK. This work also describes a potential new mechanism in inflammatory diseases while showing the importance of IL-1α in maintaining DRA levels.

The interplay between genetic and environmental factors during pregnancy can predispose to inflammatory diseases postnatally, including eosinophilic esophagitis (EoE), a chronic allergic disease triggered by food. Herein, we examined the effects of amniotic fluid (AF) on esophageal epithelial differentiation and responsiveness to proallergic stimuli. Multiplex analysis of AF revealed the expression of 66 cytokines, whereas five cytokines including IL-4 and thymic stromal lymphopoietin (TSLP) were not detected. Several proinflammatory cytokines including TNFα and IL-12 were highly expressed in the AF from women who underwent preterm birth, whereas EGF was the highest in term birth samples. Exposure of esophageal epithelial cells to AF resulted in transient phosphorylation of ERK1/2 and the transcription of early response genes, highlighting the direct impact of AF on esophageal epithelial cells. In a three-dimensional spheroid model, AF modified the esophageal epithelial differentiation program and enhanced the transcription of IL-13-target genes, including CCL26 and CAPN14, which encodes for a major genetic susceptibility locus for eosinophilic esophagitis. Notably, CAPN14 exhibited upregulation in spheroids exposed to preterm but not term AF following differentiation. Collectively, our findings call attention to the role of AF as a potential mediator of the intrauterine environment that influences subsequent esophageal disorders.NEW & NOTEWORTHY The interaction between amniotic fluid and the esophageal epithelium during pregnancy modifies esophageal epithelial differentiation and subsequent responsiveness to inflammatory stimuli, including interleukin 13 (IL-13). This interaction may predispose individuals to inflammatory conditions of the esophagus, such as eosinophilic esophagitis (EoE), in later stages of life.

Congenital heart disease (CHD) is the most common birth defect, occurring in roughly 40,000 U.S. births annually. Malnutrition and feeding intolerance (FI) in CHD range from 30% to 42% and are associated with longer hospitalization and increased mortality. Cardiopulmonary bypass (CPB) required for surgical repair of CHD induces a systemic inflammatory response worsening intestinal dysbiosis and leading to intestinal epithelial barrier dysfunction (EBD), possibly contributing to postoperative FI. The objective of this study was to determine the relationship of postoperative FI with intestinal microbiome, short-chain fatty acids (SCFAs), and EBD in pediatric CHD after cardiac surgery. This was a prospective study of patients aged 0-15 years undergoing cardiac surgery with CPB. Samples were collected preoperatively and postoperatively to evaluate the gut microbiome, plasma EBD markers, short-chain fatty acids (SCFAs), and plasma cytokines. Clinical data were collected to calculate a FI score and evaluate patient status postoperatively. We enrolled 26 CPB patients and identified FI (n = 13). Patients with FI had unique microbial shifts with the reduced SCFA-producing organisms Rothia, Clostridium innocuum, and Intestinimonas. Patients who developed FI had associated elevations in the plasma EBD markers claudin-2 (P < 0.05), claudin-3 (P < 0.01), and fatty acid binding protein (P < 0.01). Patients with FI had reduced plasma and stool SCFAs. Mediation analysis showed the microbiome functional shift was associated with reductions in stool butyric and propionic acid in patients with FI. In conclusion, we provide novel evidence that intestinal dysbiosis, markers of EBD, and SCFA depletion are associated with FI. These data will help identify mechanisms and therapeutics to improve clinical outcomes following pediatric cardiac surgery.NEW & NOTEWORTHY Feeding intolerance contributes to postoperative morbidity following pediatric cardiac surgery. The intestinal microbiome and milieu play a vital role in gut function. Short-chain fatty acids are gut and cardioprotective metabolites produced by commensal bacteria and help maintain appropriate barrier function. Depletion of these metabolites and barrier dysfunction contribute to postoperative feeding intolerance following cardiac surgery. Identifying mechanistic targets to improve the intestinal milieu with the goal of improved nutrition and clinical outcomes is critical.

Mesenteric ischemia increases gut permeability and bacterial translocation. In human colon, chemical hypoxia induced by 2,4-dinitrophenol (DNP) activates basolateral intermediate conductance K⁺ (IK) channels (designated KCa3.1 or KCNN4) and increases paracellular shunt conductance/permeability (G_S), but whether this leads to increased macromolecule permeability is unclear. Somatostatin (SOM) inhibits IK channels and prevents hypoxia-induced increases in G_S. Thus, we examined whether octreotide (OCT), a synthetic SOM analog, prevents hypoxia-induced increases G_S in human colon and hypoxia-induced increases in total epithelial conductance (G_T) and permeability to FITC-dextran 4000 (FITC) in rat colon. The effects of serosal SOM and OCT on increases in G_S induced by 100 µM DNP were compared in isolated human colon. The effects of OCT on DNP-induced increases in G_T and transepithelial FITC movement were evaluated in isolated rat distal colon. G_S in DNP-treated human colon was 52% greater than in controls (P = 0.003). G_S was similar when 2 µM SOM was added after or before DNP treatment, in both cases being less (P < 0.05) than with DNP alone. OCT (0.2 µM) was equally effective preventing hypoxia-induced increases in G_S, whether added after or before DNP treatment. In rat distal colon, DNP significantly increased G_T by 18% (P = 0.016) and mucosa-to-serosa FITC movement by 43% (P = 0.01), and 0.2 µM OCT pretreatment completely prevented these changes. We conclude that OCT prevents hypoxia-induced increases in paracellular/macromolecule permeability and speculate that it may limit ischemia-induced gut hyperpermeability during abdominal surgery, thereby reducing bacterial/bacterial toxin translocation and sepsis.NEW & NOTEWORTHY Somatostatin (SOM, 2 µM) and octreotide (OCT, 0.2 µM, a long-acting synthetic analog of SOM) were equally effective in preventing chemical hypoxia-induced increases in paracellular shunt permeability/conductance in isolated human colon. In rat distal colon, chemical hypoxia significantly increased total epithelial conductance and transepithelial movement of FITC-dextran 4000, changes completely prevented by 0.2 µM OCT. OCT may prevent or limit gut ischemia during abdominal surgery, thereby decreasing the risk of bacterial/bacterial toxin translocation and sepsis.