EP receptor expression in human intestinal epithelium and localization relative to the stem cell zone of the crypts

Disruption of epithelium integrity by inflammation-associated fibroblasts through prostaglandin signaling

Inflammation-associated fibroblasts (IAFs) are associated with progression and drug resistance of chronic inflammatory diseases such as inflammatory bowel disease (IBD), but their direct impact on epithelial cells is unknown. Here, we developed an in vitro model whereby human colon fibroblasts are induced by specific cytokines and recapitulate key features of IAFs in vivo. When cocultured with patient-derived colon organoids (colonoids), IAFs induced rapid colonoid expansion and barrier disruption due to swelling and rupture of individual epithelial cells. Colonoids cocultured with IAFs also show increased DNA damage, mitotic errors, and proliferation arrest. These IAF-induced epithelial defects are mediated by a paracrine pathway involving prostaglandin E2 and its receptor EP4, leading to protein kinase A -dependent activation of the cystic fibrosis transmembrane conductance regulator. EP4-specific chemical inhibitors effectively prevented IAF-induced colonoid swelling and restored normal proliferation and genome stability. These findings reveal a mechanism by which IAFs could promote and perpetuate IBD and suggest a therapeutic avenue to mitigate inflammation-associated epithelial injury.

Disruption of Epithelium Integrity by Inflammation-Associated Fibroblasts through Prostaglandin Signaling: IAFs disrupt colon epithelium via PGE2-EP4

Inflammation-associated fibroblasts (IAFs) are associated with the progression and drug resistance of chronic inflammatory diseases such as inflammatory bowel disease (IBD), but their direct impact on epithelial function and architecture is unknown. In this study, we developed an in vitro model whereby human colon fibroblasts are induced to become IAFs by specific cytokines and recapitulate key features of IAFs in vivo. When co-cultured with patient-derived colon organoids (colonoids), IAFs induced rapid colonoid swelling and barrier disruption due to swelling and rupture of individual epithelial cells. Epithelial cells co-cultured with IAFs also exhibit increased DNA damage, mitotic errors, and proliferation arrest. These IAF-induced epithelial defects are mediated through a paracrine pathway involving prostaglandin E2 (PGE2) and the PGE2 receptor EP4, leading to PKA-dependent activation of the CFTR chloride channel. Importantly, EP4-specific chemical inhibitors effectively prevented colonoid swelling and restored normal proliferation and genome stability of IAF-exposed epithelial cells. These findings reveal a mechanism by which IAFs could promote and perpetuate IBD and suggest a potential treatment to mitigate inflammation-associated epithelial injury.

IL-33 mediates Pseudomonas induced airway fibrogenesis and is associated with CLAD

BACKGROUND

Long term outcomes of lung transplantation are impacted by the occurrence of chronic lung allograft dysfunction (CLAD). Recent evidence suggests a role for the lung microbiome in the occurrence of CLAD, but the exact mechanisms are not well defined. We hypothesize that the lung microbiome inhibits epithelial autophagic clearance of pro-fibrotic proteins in an IL-33 dependent manner, thereby augmenting fibrogenesis and risk for CLAD.

METHODS

Autopsy derived CLAD and non-CLAD lungs were collected. IL-33, P62 and LC3 immunofluorescence was performed and assessed using confocal microscopy. Pseudomonas aeruginosa (PsA), Streptococcus Pneumoniae (SP), Prevotella Melaninogenica (PM), recombinant IL-33 or PsA-lipopolysaccharide was co-cultured with primary human bronchial epithelial cells (PBEC) and lung fibroblasts in the presence or absence of IL-33 blockade. Western blot analysis and quantitative reverse transcription (qRT) PCR was performed to evaluate IL-33 expression, autophagy, cytokines and fibroblast differentiation markers. These experiments were repeated after siRNA silencing and upregulation (plasmid vector) of Beclin-1.

RESULTS

Human CLAD lungs demonstrated markedly increased expression of IL-33 and reduced basal autophagy compared to non-CLAD lungs. Exposure of co-cultured PBECs to PsA, SP induced IL-33, and inhibited PBEC autophagy, while PM elicited no significant response. Further, PsA exposure increased myofibroblast differentiation and collagen formation. IL-33 blockade in these co-cultures recovered Beclin-1, cellular autophagy and attenuated myofibroblast activation in a Beclin-1 dependent manner.

CONCLUSION

CLAD is associated with increased airway IL-33 expression and reduced basal autophagy. PsA induces a fibrogenic response by inhibiting airway epithelial autophagy in an IL-33 dependent manner.

Mucosal Serotonin Reuptake Transporter Expression in Irritable Bowel Syndrome Is Modulated by Gut Microbiota Via Mast Cell-Prostaglandin E2

BACKGROUND & AIMS

Increased colonic serotonin (5-HT) level and decreased serotonin reuptake transporter (SERT) expression in irritable bowel syndrome (IBS) may contribute to diarrhea and visceral hypersensitivity. We investigated whether mucosal SERT is modulated by gut microbiota via a mast cell-prostaglandin E2 (PGE2) pathway.

METHODS

C57Bl/6 mice received intracolonic infusion of fecal supernatant (FS) from healthy controls or patients with diarrhea-predominant irritable bowel syndrome (IBS-D). The role of mast cells was studied in mast cell-deficient mice. Colonic organoids and/or mast cells were used for in vitro experiments. SERT expression was measured by quantitative polymerase chain reaction and Western blot. Visceromotor responses to colorectal distension and colonic transit were assessed.

RESULTS

Intracolonic infusion of IBS-D FS in mice caused an increase in mucosal 5-HT compared with healthy control FS, accompanied by ∼50% reduction in SERT expression. Mast cell stabilizers, cyclooxygenase-2 inhibitors, and PGE2 receptor antagonist prevented SERT downregulation. Intracolonic infusion of IBS-D FS failed to reduce SERT expression in mast cell-deficient (W/Wv) mice. This response was restored by mast cell reconstitution. The downregulation of SERT expression evoked by IBS FS was prevented by lipopolysaccharide (LPS) antagonist LPS from Rhodobacter sphaeroides and a bacterial trypsin inhibitor. In vitro LPS treatment caused increased cyclooxygenase-2 expression and PGE2 release from cultured mouse mast cells. Intracolonic infusion of IBS-D FS in mice reduced colonic transit, increased fecal water content, and increased visceromotor responses to colorectal distension. Ondansetron prevented these changes.

CONCLUSIONS

Fecal LPS acting in concert with trypsin in patients with IBS-D stimulates mucosal mast cells to release PGE2, which downregulates mucosal SERT, resulting in increased mucosal 5-HT. This may contribute to diarrhea and abdominal pain common in IBS.

Possible cytoprotective mechanisms of oxytocin against 5-fluorouracil-induced gastrointestinal mucositis

Gastrointestinal mucositis is a common and dose-limiting side effect characterized by ulcerative lesions in the mucosa of the digestive tract in patients receiving anticancer drugs such as 5-fluorouracil (5-FU), a potent antineoplastic drug. Several protocols have reported the efficacy of therapeutic interventions to prevent this side effect, although complete success has not yet been achieved and mucositis remains one of the most serious complications associated with 5-FU therapy. Oxytocin, a well-known antistress agent, has been reported to have comparable effects to ranitidine. Previous studies have shown that oxytocin inhibits gastric acid secretion and the expression of proinflammatory cytokines in rats. If oxytocin can reduce stress-induced ulcers via antioxidant, antiapoptotic, and anti-inflammatory pathways, then it may have a dose-dependent effect on gastrointestinal mucositis caused by 5-FU.

TNFα Induces LGR5+ Stem Cell Dysfunction In Patients With Crohn's Disease

BACKGROUND & AIMS

Tumor necrosis factor alpha (TNFα) is considered a major tissue damage-promoting effector in Crohn's disease (CD) pathogenesis. Patient-derived intestinal organoid (enteroid) recapitulates the disease-specific characteristics of the intestinal epithelium. This study aimed to evaluate the intestinal epithelial responses to TNFα in enteroids derived from healthy controls and compare them with those of CD patient-derived enteroids.

METHODS

Human enteroids derived from patients with CD and controls were treated with TNFα (30 ng/mL), and cell viability and gene expression patterns were evaluated.

RESULTS

TNFα induced MLKL-mediated necroptotic cell death, which was more pronounced in CD patient-derived enteroids than in control enteroids. Immunohistochemistry and RNA sequencing revealed that treatment with TNFα caused expansion of the intestinal stem cell (ISC) populations. However, expanded ISC subpopulations differed in control and CD patient-derived enteroids, with LGR5+ active ISCs in control enteroids and reserve ISCs, such as BMI1+ cells, in CD patient-derived enteroids. In single-cell RNA sequencing, LGR5+ ISC-enriched cell cluster showed strong expression of TNFRSF1B (TNFR2) and cyclooxygenase-prostaglandin E2 (PGE2) activation. In TNFα-treated CD patient-derived enteroids, exogenous PGE2 (10 nmol/L) induced the expansion of the LGR5+ ISC population and improved organoid-forming efficiency, viability, and wound healing.

CONCLUSIONS

TNFα increases necroptosis of differentiated cells and induces the expansion of LGR5+ ISCs. In CD patient-derived enteroids, TNFα causes LGR5+ stem cell dysfunction (expansion failure), and exogenous PGE2 treatment restored the functions of LGR5+ stem cells. Therefore, PGE2 can be used to promote mucosal healing in patients with CD.

Unique Regulation of Intestinal Villus Epithelial Cl-/HCO3- Exchange by Cyclooxygenase Pathway Metabolites of Arachidonic Acid in a Mouse Model of Spontaneous Ileitis

Electrolytes (NaCl) and fluid malabsorption cause diarrhea in inflammatory bowel disease (IBD). Coupled NaCl absorption, mediated by Na⁺/H⁺ and Cl^-/HCO₃^- exchanges on the intestinal villus cells brush border membrane (BBM), is inhibited in IBD. Arachidonic acid metabolites (AAMs) formed via cyclooxygenase (COX) or lipoxygenase (LOX) pathways are elevated in IBD. However, their effects on NaCl absorption are not known. We treated SAMP1/YitFc (SAMP1) mice, a model of spontaneous ileitis resembling human IBD, with Arachidonyl Trifluoro Methylketone (ATMK, AAM inhibitor), or with piroxicam or MK-886, to inhibit COX or LOX pathways, respectively. Cl^-/HCO₃^- exchange, measured as DIDS-sensitive ³⁶Cl uptake, was significantly inhibited in villus cells and BBM vesicles of SAMP1 mice compared to AKR/J controls, an effect reversed by ATMK. Piroxicam, but not MK-886, also reversed the inhibition. Kinetic studies showed that inhibition was secondary to altered K_m with no effects on V_max. Whole cell or BBM protein levels of Down-Regulated in Adenoma (SLC26A3) and putative anion transporter-1 (SLC26A6), the two key BBM Cl^-/HCO₃^- exchangers, were unaltered. Thus, inhibition of villus cell Cl^-/HCO₃^- exchange by COX pathway AAMs, such as prostaglandins, via reducing the affinity of the exchanger for Cl^-, and thereby causing NaCl malabsorption, could significantly contribute to IBD-associated diarrhea.

Prostaglandin E2 receptors and their role in gastrointestinal motility - Potential therapeutic targets

Prostaglandin E₂ (PGE₂) is found throughout the gastrointestinal tract in a diverse variety of functions and roles. The recent discovery of four PGE₂ receptor subtypes in intestinal muscle layers as well as in the enteric plexus has led to much interest in the study of their roles in gut motility. Gut dysmotility has been implicated in functional disease processes including irritable bowel syndrome (IBS) and slow transit constipation, and lubiprostone, a PGE₂ derivative, has recently been licensed to treat both conditions. The diversity of actions of PGE₂ in the intestinal tract is attributed to its differing effects on its downstream receptor types, as well as their varied distribution in the gut, in both health and disease. This review aims to identify the role and distribution of PGE₂ receptors in the intestinal tract, and aims to elucidate their distinct role in gut motor function, with a specific focus on functional intestinal pathologies.

The Role of Cyclooxygenases-2 in Benzo(a)pyrene-Induced Neurotoxicity of Cortical Neurons

With the help of particulate matter, benzo(a)pyrene (BaP) has become a widely distributed environmental contaminant. In addition to the well-known carcinogenicity, a growing number of studies have focused on the neurotoxicity of BaP, especially on adverse neurobehavioral effects. However, the molecular modulating mechanisms remain unclear. In this paper, we confirmed that BaP exposure produced a neuronal insult via its metabolite benzo(a)pyrene diol epoxide (BPDE) on the primary cultured cortical neuron in vitro and mice in vivo models, and the effects were largely achieved by activating cyclooxygenases-2 (COX-2) enhancement. Also, the action of BaP on elevating COX-2 was initiated by BPDE firmly binding to the active pockets of COX-2, then followed by the production of prostaglandin E₂ (PGE₂) and upregulation of its EP2 and EP4 receptors, finally stimulating the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signaling pathway. Our results reveal a mechanistic association underlying BaP exposure and increased risk for neurological dysfunction and clarify the ways to prevent and treat brain injuries in polluted environments.

Prostaglandin E2 accelerated recovery of chemotherapy-induced intestinal damage by increasing expression of cyclin D

Intestinal stem cells (ISCs) play a crucial role in maintaining intestinal homeostasis upon chemotherapy and radiotherapy. It has been documented that prostaglandin E2 (PGE2) treatment improved hematopoietic stem cell function in vitro and in vivo, while the relationship between PGE2 and intestinal stem cells remains unclear. Presently, mice were exposed to PGE1, dmPGE2 and indomethacin. Numbers and function of ISCs were assessed by analyzing Olfm4⁺ ISCs. Intestinal protection of dmPGE2 was investigated on a 5-fluorouracil (5FU)-induced intestinal damage mouse model. The results showed that dmPGE2 treatment, but not PGE1, increased numbers of Olfm4⁺ ISCs in dose- and time-dependent manners. Indomethacin treatment decreased numbers of Olfm4⁺ ISCs. The beneficial effects of short-term dmPGE2 treatment on intestine were supported in a 5FU-induced intestinal damage model. Our data showed that 5FU treatment significantly decreased numbers of Olfm4⁺ ISCs and goblet cells in intestine, which could be ameliorated by dmPGE2 treatment. dmPGE2 treatment accelerated the recovery of 5FU-induced ISC injury via increasing expression of cyclin D1 and D2 in intestine. Furthermore, dmPGE2 treatment-induced expression of cyclin D1 and D2 might be mediated by up-regulation of FOXM1 expression in intestine. These findings feature PGE2 as an effective protector against chemotherapy-induced intestinal damage.

Eicosanoid receptors: Targets for the treatment of disrupted intestinal epithelial homeostasis

The importance of cyclooxygenase and lipoxygenase pathways and the consequent eicosanoid synthesis in the physiology and pathophysiology of the intestinal epithelium is currently being established. Each eicosanoid (prostanoid, leukotriene, hydroxyeicosatetraenoic acid) preferentially recognizes one or more receptors coupled to one or more signal-transduction processes. This overview focuses on the role of eicosanoid receptors in the maintenance of intestinal epithelium physiology through the control of proliferation/differentiation/apoptosis processes. Furthermore, it is reported that the role of these receptors on the regulation of the barrier function of the intestinal epithelium have arisen through the regulation of absorption/secretion processes, tight-junction state and the control of the intestinal immune response. Also, this review considers the implication of AA cascade in the disruption of epithelial homeostasis during inflammatory bowel diseases and colorectal cancer as well as the therapeutic values and potential of the eicosanoid receptors as novel targets for the treatments of the pathologies above mentioned.

Colonic Saturated Fatty Acid Concentrations and Expression of COX-1, but not Diet, Predict Prostaglandin E2 in Normal Human Colon Tissue

Prostaglandin E2 (PGE2) in the colon is a pro-inflammatory mediator that is associated with increased risk of colon cancer. In this study, expression of genes in the PGE2 pathway were quantified in colon biopsies from a trial of a Mediterranean versus a Healthy Eating diet in 113 individuals at high risk for colon cancer. Colon biopsies were obtained before and after 6 months of intervention. Quantitative, real-time PCR was used to measure mRNA expression of prostaglandin H synthases (PTGS1 and 2), prostaglandin E synthases (PTGES1 and 3), prostaglandin dehydrogenase (HPGD), and PGE2 receptors (PTGER2, PTGER4). The most highly expressed genes were HPGD and PTGS1. In multivariate linear regression models of baseline data, both colon saturated fatty acid concentrations and PTGS1 expression were significant, positive predictors of colon PGE2 concentrations after controlling for nonsteroidal anti-inflammatory drug use, gender, age, and smoking status. The effects of dietary intervention on gene expression were minimal with small increases in expression noted for PTGES3 in both arms and in PTGER4 in the Mediterranean arm. These results indicate that short-term dietary change had little effect on enzymes in the prostaglandin pathway in the colon and other factors, such as differences in fatty acid metabolism, might be more influential.

Oxidative Stress and Carbonyl Lesions in Ulcerative Colitis and Associated Colorectal Cancer

Oxidative stress has long been known as a pathogenic factor of ulcerative colitis (UC) and colitis-associated colorectal cancer (CAC), but the effects of secondary carbonyl lesions receive less emphasis. In inflammatory conditions, reactive oxygen species (ROS), such as superoxide anion free radical (O2 (∙-)), hydrogen peroxide (H2O2), and hydroxyl radical (HO(∙)), are produced at high levels and accumulated to cause oxidative stress (OS). In oxidative status, accumulated ROS can cause protein dysfunction and DNA damage, leading to gene mutations and cell death. Accumulated ROS could also act as chemical messengers to activate signaling pathways, such as NF-κB and p38 MAPK, to affect cell proliferation, differentiation, and apoptosis. More importantly, electrophilic carbonyl compounds produced by lipid peroxidation may function as secondary pathogenic factors, causing further protein and membrane lesions. This may in turn exaggerate oxidative stress, forming a vicious cycle. Electrophilic carbonyls could also cause DNA mutations and breaks, driving malignant progression of UC. The secondary lesions caused by carbonyl compounds may be exceptionally important in the case of host carbonyl defensive system deficit, such as aldo-keto reductase 1B10 deficiency. This review article updates the current understanding of oxidative stress and carbonyl lesions in the development and progression of UC and CAC.

Vitamin D, Inflammation, and Colorectal Cancer Progression: A Review of Mechanistic Studies and Future Directions for Epidemiological Studies

Survival from colorectal cancer is positively associated with vitamin D status. However, whether this association is causal remains unclear. Inflammatory processes may link vitamin D to colorectal cancer survival, and therefore investigating inflammatory markers as potential mediators may be a valuable next step. This review starts with an overview of inflammatory processes suggested to be involved in colorectal cancer progression and regulated by vitamin D. Next, we provide recommendations on how to study inflammatory markers in future epidemiologic studies on vitamin D and colorectal cancer survival. Mechanistic studies have shown that calcitriol-active form of vitamin D-influences inflammatory processes involved in cancer progression, including the enzyme cyclooxygenase 2, the NF-κB pathway, and the expression of the cytokines TNFα, IL1β, IL6, IL8, IL17, and TGFβ1. Based on this and taking into account methodologic issues, we recommend to include analysis of specific soluble peptides and proteins, such as cytokines, in future epidemiologic studies on this issue. Vitamin D and the markers should preferably be measured at multiple time points during disease progression or recovery and analyzed using mediation analysis. Including these markers in epidemiologic studies may help answer whether inflammation mediates a causal relationship between vitamin D and colorectal cancer survival.

Oxytocin evokes a pulsatile PGE2 release from ileum mucosa and is required for repair of intestinal epithelium after injury

We measured the short-circuit current (I_sc) in rat ileum mucosa to identify the effect of oxytocin (OT) on mucosal secretion in small intestine. We identified a COX-2-derived pulsatile PGE2 release triggered by OT in rat ileum mucosa. OT receptors (OTR) are expressed in intestine crypt epithelial cells. Notably, OT evoked a dynamic change of [Ca²⁺]_i in ileum crypts, which was responsible for this pulsatile release of PGE2. OT ameliorated 5-FU-, radiation- or DSS- induced injury in vivo, including the improvement of weight loss, reduced villus height and impaired survival of crypt transit-amplifying cells as well as crypt. Moreover, these protective effects of OT against intestinal injury were eliminated by coadministration of a selective inhibitor of PGE2, AH6809. Our findings strongly suggest that OT, a novel and important regulator of intestine mucosa barrier, is required for repair of intestinal epithelium after injury. Considering that OT is an FDA-approved drug, this work reveals a potential novel and safe way to combat or prevent chemo-radiotherapy induced intestine injury or to treat IBD.

Sodium caprate-induced increases in intestinal permeability and epithelial damage are prevented by misoprostol

Epithelial damage caused by intestinal permeation enhancers is a source of debate concerning safety. The medium chain fatty acid, sodium caprate (C10), causes reversible membrane perturbation at high dose levels required for efficacy in vivo, so the aim was to model it in vitro. Exposure of Caco-2 monolayers to 8.5mM C10 for 60min followed by incubation in fresh buffer led to (i) recovery in epithelial permeability (i.e. transepithelial electrical resistance (TEER) and apparent permeability coefficient (Papp) of [(14)C]-mannitol), (ii) recovery of cell viability parameters (monolayer morphology, plasma membrane potential, mitochondrial membrane potential, and intracellular calcium) and (iii) reduction in mRNA expression associated with inflammation (IL-8). Pre-incubation of monolayers with a mucosal prostaglandin cytoprotectant was attempted in order to further decipher the mechanism of C10. Misoprostol (100nM), inhibited C10-induced changes in monolayer parameters, an effect that was partially attenuated by the EP1 receptor antagonist, SC51322. In rat isolated intestinal tissue mucosae and in situ loop instillations, C10-induced respective increases in the [(14)C]-mannitol Papp and the AUC of FITC-dextran 4000 (FD-4) were similarly inhibited by misoprostol, with accompanying morphological damage spared. These data support a temporary membrane perturbation effect of C10, which is linked to its capacity to mainly increase paracellular flux, but which can be prevented by pre-exposure to misoprostol.

Low n-3 long-chain polyunsaturated fatty acids in newly diagnosed celiac disease in children with preexisting type 1 diabetes mellitus

OBJECTIVE

Fat malabsorption can occur in celiac disease (CD) owing to villus atrophy and inflammation of small intestinal mucosa. Abnormal fatty acid (FA) status of intestinal mucosa in children with CD was reported earlier. Previously we found significantly reduced availability of n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) in children and young adults with type 1 diabetes mellitus (DM). The aim of this study was to investigate FAs in plasma lipid classes in children with newly diagnosed CD with or without preexisting DM.

METHODS

FA composition of plasma samples of children with untreated CD only (n = 20) and with preexisting DM (CDDM, n = 8) were compared with those of healthy controls (n = 21). Detailed analysis of phospholipid, triacylglycerol, and sterol ester FAs was performed by high-resolution capillary gas-liquid chromatography.

RESULTS

Significantly decreased docosapentaenoic (C22:5n-3), docosahexaenoic (C22:6n-3), n-3 polyunsaturated fatty acids (n-3 PUFA), and n-3 LCPUFA values were found in CDDM group compared with controls and patients with CD. When compared with healthy controls, no significant difference was found in plasma FAs of children with newly diagnosed CD only.

CONCLUSIONS

Children with CDDM showed marked signs of reduced availability of n-3 PUFA and n-3 LCPUFA in circulating lipids. Although different tissues express membrane FAs differently, our present study suggests that CD on its own does not necessarily lead to detectable disturbances of essential FA metabolism in plasma and supports the concept that DM has significant impact on plasma FA composition in children.

Degradation of IF1 controls energy metabolism during osteogenic differentiation of stem cells

Differentiation of human mesenchymal stem cells (hMSCs) requires the rewiring of energy metabolism. Herein, we demonstrate that the ATPase inhibitory factor 1 (IF1) is expressed in hMSCs and in prostate and colon stem cells but is not expressed in the differentiated cells. IF1 inhibits oxidative phosphorylation and regulates the activity of aerobic glycolysis in hMSCs. Silencing of IF1 in hMSCs mimics the metabolic changes observed in osteocytes and accelerates cellular differentiation. Activation of IF1 degradation acts as the switch that regulates energy metabolism during differentiation. We conclude that IF1 is a stemness marker important for maintaining the quiescence state.