P2X7 Receptor Regulates Collagen Expression in Human Intestinal Fibroblasts: Relevance in Intestinal Fibrosis.

Intestinal fibrosis is a common complication that affects more than 50% of Crohn´s Disease (CD) patients. There is no pharmacological treatment against this complication, with surgery being the only option. Due to the unknown role of P2X7 in intestinal fibrosis, we aim to analyze the relevance of this receptor in CD complications. Surgical resections from CD and non-Inflammatory Bowel Disease (IBD) patients were obtained. Intestinal fibrosis was induced with two different murine models: heterotopic transplant model and chronic-DSS colitis in wild-type and P2X7-/- mice. Human small intestine fibroblasts (HSIFs) were transfected with an siRNA against P2X7 and treated with TGF-ß. A gene and protein expression of P2X7 receptor was significantly increased in CD compared to non-IBD patients. The lack of P2X7 in mice provoked an enhanced collagen deposition and increased expression of several profibrotic markers in both murine models of intestinal fibrosis. Furthermore, P2X7-/- mice exhibited a higher expression of proinflammatory cytokines and a lower expression of M2 macrophage markers. Moreover, the transient silencing of the P2X7 receptor in HSIFs significantly induced the expression of Col1a1 and potentiated the expression of Col4 and Col5a1 after TGF-ß treatment. P2X7 regulates collagen expression in human intestinal fibroblasts, while the lack of this receptor aggravates intestinal fibrosis.

HIF-Overexpression and Pro-Inflammatory Priming in Human Mesenchymal Stromal Cells Improves the Healing Properties of Extracellular Vesicles in Experimental Crohn's Disease.

Extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) have therapeutic potential in the treatment of several immune disorders, including ulcerative colitis, owing to their regenerative and immunosuppressive properties. We recently showed that MSCs engineered to overexpress hypoxia-inducible factor 1-alpha and telomerase (MSC-T-HIF) and conditioned with pro-inflammatory stimuli release EVs (EVMSC-T-HIFC) with potent immunomodulatory activity. We tested the efficacy of EVMSC-T-HIFC to repolarize M1 macrophages (Mφ1) to M2-like macrophages (Mφ2-like) by analyzing surface markers and cytokines and performing functional assays in co-culture, including efferocytosis and T-cell proliferation. We also studied the capacity of EVMSC-T-HIFC to dampen the inflammatory response of activated endothelium and modulate fibrosis. Finally, we tested the therapeutic capacity of EVMSC-T-HIFC in an acute colitis model. EVMSC-T-HIFc induced the repolarization of monocytes from Mφ1 to an Mφ2-like phenotype, which was accompanied by reduced inflammatory cytokine release. EVMSC-T-HIFc-treated Mφ1 had similar effects of immunosuppression on activated peripheral blood mononuclear cells (PBMC) as Mφ2, and reduced the adhesion of PBMCs to activated endothelium. EVMSC-T-HIFc also prevented myofibroblast differentiation of TGF-ß-treated fibroblasts. Finally, administration of EVMSC-T-HIFc promoted healing in a TNBS-induced mouse colitis model in terms of preserving colon length and intestinal mucosa architecture and altering the ratio of Mφ1/ Mφ2 infiltration. In conclusion, EVMSC-T-HIFC have effective anti-inflammatory properties, making them potential therapeutic agents in cell free-based therapies for the treatment of Crohn's disease and likely other immune-mediated inflammatory diseases.

A disturbed metabolite-GPCR axis is associated with microbial dysbiosis in IBD patients: Potential role of GPR109A in macrophages.

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract characterized by disrupted immune function. Indeed, gut microbiota dysbiosis and metabolomic profile alterations, are hallmarks of IBD. In this scenario, metabolite-sensing G-protein coupled receptors (GPCRs), involved in several biological processes, have emerged as pivotal players in the pathophysiology of IBD. The aim of this study was to characterize the axis microbiota-metabolite-GPCR in intestinal surgical resections from IBD patients. Results showed that UC patients had a lower microbiota richness and bacterial load, with a higher proportion of the genus Cellulosimicrobium and a reduced proportion of Escherichia, whereas CD patients showed a decreased abundance of Enterococcus. Furthermore, metabolomic analysis revealed alterations in carboxylic acids, fatty acids, and amino acids in UC and CD samples. These patients also exhibited upregulated expression of most metabolite-sensing GPCRs analysed, which positively correlated with pro-inflammatory and pro-fibrotic markers. The role of GPR109A was studied in depth and increased expression of this receptor was detected in epithelial cells and cells from lamina propria, including CD68+ macrophages, in IBD patients. The treatment with ß-hydroxybutyrate increased gene expression of GPR109A, CD86, IL1B and NOS2 in U937-derived macrophages. Besides, when GPR109A was transiently silenced, the mRNA expression and secretion of IL-1ß, IL-6 and TNF-α were impaired in M1 macrophages. Finally, the secretome from siGPR109A M1 macrophages reduced the gene and protein expression of COL1A1 and COL3A1 in intestinal fibroblasts. A better understanding of metabolite-sensing GPCRs, such as GPR109A, could establish their potential as therapeutic targets for managing IBD.

Metabolite Sensing GPCRs: Promising Therapeutic Targets for Cancer Treatment?

G-protein-coupled receptors constitute the most diverse and largest receptor family in the human genome, with approximately 800 different members identified. Given the well-known metabolic alterations in cancer development, we will focus specifically in the 19 G-protein-coupled receptors (GPCRs), which can be selectively activated by metabolites. These metabolite sensing GPCRs control crucial processes, such as cell proliferation, differentiation, migration, and survival after their activation. In the present review, we will describe the main functions of these metabolite sensing GPCRs and shed light on the benefits of their potential use as possible pharmacological targets for cancer treatment.

Gastrin induces the interaction between human mononuclear leukocytes and endothelial cells through the endothelial expression of P-selectin and VCAM-1.

Gastric mucosal inflammation is frequently associated with hypergastrinemia, and a correlation exists between the level of gastrin and degree of gastritis. We have previously observed that gastrin promotes leukocyte-endothelial interactions and contributes to Helicobacter-induced inflammation in the rat mesentery. In the present study, we aimed to evaluate a possible proinflammatory activity of gastrin in humans. The interaction between human leukocytes [U-937 cells, peripheral blood polymorphonuclear (PMN), and peripheral blood mononuclear (PBMC) cells] and human umbilical vein endothelial cells (HUVEC) was analyzed in static and dynamic conditions. The endothelial expression of adhesion molecules [P-selectin, E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule (VCAM)-1] was analyzed by flow cytometry and fluorescent microscopy screening. Gastrin increased the static adhesion of U-937 cells to HUVEC (1 h; 10(-9) M: 122 +/- 9%; 10(-8) M: 143 +/- 17%; 10(-7) M: 162 +/- 14% vs. control, all P < 0.05). Incubation of HUVEC with gastrin (4 h) also increased PBMC rolling (vehicle: 63 +/- 12; 10(-9) M: 109 +/- 29; 10(-8) M: 141 +/- 24; 10(-7) M: 261 +/- 16 leukocytes/min, P < 0.05) and adhesion (vehicle: 3 +/- 2, 10(-9) M: 11 +/- 4, 10(-8) M: 17 +/- 5, 10(-7) M: 15 +/- 5 leukocytes/mm(2), all P < 0.05) in the parallel-plate flow chamber. Treatment of PBMC with gastrin had no effects. The cholecystokinin (CCK)-2 receptor antagonist (L-365,260, 10(-7) M) prevented the effects of gastrin. P-selectin and VCAM-1 expression were enhanced by gastrin, and neutralizing antibodies against these molecules prevented PBMC rolling and adhesion. Gastrin did not affect the interactions between HUVEC and PMN. Gastrin induces interactions between human mononuclear leukocytes and endothelial cells through the activation of CCK-2 receptors and the enhancement of endothelial P-selectin and VCAM-1.

Indomethacin Disrupts Autophagic Flux by Inducing Lysosomal Dysfunction in Gastric Cancer Cells and Increases Their Sensitivity to Cytotoxic Drugs.

NSAIDs inhibit tumorigenesis in gastrointestinal tissues and have been proposed as coadjuvant agents to chemotherapy. The ability of cancer epithelial cells to adapt to the tumour environment and to resist cytotoxic agents seems to depend on rescue mechanisms such as autophagy. In the present study we aimed to determine whether an NSAID with sensitizing properties such as indomethacin modulates autophagy in gastric cancer epithelial cells. We observed that indomethacin causes lysosomal dysfunction in AGS cells and promotes the accumulation of autophagy substrates without altering mTOR activity. Indomethacin enhanced the inhibitory effects of the lysosomotropic agent chloroquine on lysosome activity and autophagy, but lacked any effect when both functions were maximally reduced with another lysosome inhibitor (bafilomycin B1). Indomethacin, alone and in combination with chloroquine, also hindered the autophagic flux stimulated by the antineoplastic drug oxaliplatin and enhanced its toxic effect, increasing the rate of apoptosis/necrosis and undermining cell viability. In summary, our results indicate that indomethacin disrupts autophagic flux by disturbing the normal functioning of lysosomes and, by doing so, increases the sensitivity of gastric cancer cells to cytotoxic agents, an effect that could be used to overcome cancer cell resistance to antineoplastic regimes.

CD16+ Macrophages Mediate Fibrosis in Inflammatory Bowel Disease.

BACKGROUND AND AIMS: Fibrosis is a common complication of Crohn's disease [CD], and is related to dysregulated tissular repair following inflammation, in which macrophages play a central role. We have previously observed that STAT6-/- mice present delayed mucosal recovery after 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis due to a deficiency in reparatory interleukin-4 [IL4]/STAT6-dependent M2 macrophages, which can be reverted by the exogenous transfer of this cell type. In the present study, we analyse the role of STAT6-dependent macrophages in intestinal fibrosis. METHODS: Colitis was induced by weekly intra-rectal administration of TNBS [6 weeks] to STAT6-/- mice and wild-type [WT] animals. Colonic surgical resections were obtained from CD patients and from colon cancer patients. RESULTS: Chronic colitis provoked a fibrogenic response in STAT6-/- mice, but not in WT animals. An accumulation of M2 macrophages, defined as CD206+ cells, was observed in WT mice, but not in STAT6-/- animals. Instead, the latter group showed an increase in CD16+ macrophages that correlated with the expression of fibrogenic markers. CD16+ macrophages were also increased in the damaged mucosa of Crohn's disease patients with stenotic or penetrating complications. Finally, administration of IL4-treated WT macrophages to STAT6-/- mice reduced TNBS-induced fibrosis. CONCLUSIONS: Our study demonstrates that STAT6 deficiency dysregulates the macrophage response to inflammatory outbursts by increasing the presence of a population of CD16+ macrophages that seems to contribute to intestinal fibrosis.

A Single Nucleotide Polymorphism in the Vitamin D Receptor Gene Is Associated With Decreased Levels of the Protein and a Penetrating Pattern in Crohn's Disease.

Background: Vitamin D signaling modulates inflammation through the vitamin D receptor (VDR). The synonymous single nucleotide polymorphism (SNP) rs731236, located in the VDR gene, has been associated with a higher risk of Crohn's disease (CD). We analyzed differences in VDR expression levels among CD patients who were homozygous for allelic variants in this SNP and their relevance for disease course. Methods: DNA was extracted from blood samples of CD patients, and SNP genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. Fresh blood from patients was used to isolate peripheral blood mononuclear cells (PBMCs) or to determine the expression of adhesion molecules by flow cytometry. We analyzed the gene expression of VDR and several cytokines in PBMCs using real-time polymerase chain reaction and the protein levels of VDR, NFκB, and IκBα by immunoblot. In addition, we collected complete clinical data for a group of 103 patients, including age at diagnosis, disease location, and disease behavior to compare patient characteristics with respect to genotype. Results: We found that CD patients who were homozygous for the risk allele presented lower levels of VDR protein in PBMCs, and that this was associated with an upregulation of IL1ß mRNA and activation of lymphocytic adhesion molecules. These patients had a higher risk of developing a B3-penetrating phenotype and of needing to undergo surgery. Conclusion: Our data highlight the relevance of vitamin D/VDR signaling in modulating the subjacent inflammation that leads to CD-related complications.

Aspirin-induced gastrointestinal damage is associated with an inhibition of epithelial cell autophagy.

BACKGROUND: Aspirin (ASA) causes gastrotoxicity by hampering the epithelial defense against luminal contents through cyclooxygenase inhibition. Since cell survival in tough conditions may depend on rescue mechanisms like autophagy, we analyzed whether epithelial cells rely on this process to defend themselves from aspirin's damaging action. METHODS: Rats received a single dose of ASA (150 mg/kg, p.o.) with or without pretreatment with the autophagy inhibitor 3-methyladenine, and gastric injury and epithelial autophagy were evaluated 3 h later. The effects of ASA on cell viability and autophagy were also evaluated in gastric epithelial AGS cells. RESULTS: Basal autophagy in the gastric mucosa was inhibited by ASA as demonstrated by increased levels of p62 and ubiquitinated proteins and total LC3 and a reduced LC3-II/LC3-I ratio. Similarly, ASA increased p62 and decreased LC3-II accumulation and the number of EmGFP/LC3B puncta in AGS cells. ASA activated the PI3K/Akt-GSK3-mTOR pathway, which phosphorylates ULK1 to prevent autophagy initiation, changes that were inhibited by the PI3K-inhibitor wortmannin. Autophagy inhibition seems to enhance the vulnerability of gastric epithelial cells as a combination of ASA with 3-methyladenine exacerbated rat gastric damage and AGS cell apoptosis. CONCLUSIONS: Our data highlight the importance of autophagy in the gastric mucosa as a protective mechanism when the epithelium is injured. In the stomach, aspirin induces mucosal damage and reduces autophagy, thus, eliminating a protective mechanism that epithelial cells could use to escape death. We hypothesize that the combination of aspirin with drugs that activate autophagy could protect against gastric damage.

Endotoxin stimulates fecal pellet output in rats through a neural mechanism.

The effects of endotoxin on fecal pellet output and the neural mechanisms involved in this response were investigated in conscious rats. E. coli endotoxin (40 micro g/kg i.p.) significantly increased fecal excretion for 3 h after the injection. Water content in feces was not modified by endotoxin. Ablation of primary afferent neurons by systemic administration of high doses of capsaicin (20+30+50 mg/kg s.c.) to adult rats prevented the stimulatory effect of endotoxin and so did abdominal vagotomy. Adrenoceptor blockade with phentolamine (5 mg/kg i.p.) + propranolol (3 mg/kg i.p.) did not modify pellet output in endotoxin-treated rats while muscarinic receptor blockade with atropine (1 mg/kg i.p.) abolished the stimulatory effect of endotoxin. Finally, the increase in pellet output induced by endotoxin was prevented in animals receiving the substance P receptor antagonist D-Pro2, D-Trp7,9-substance P (2 mg/kg i.p.) or the NO-synthase inhibitor L-NAME (10 mg/kg i.p.). None of the above treatments modified pellet output in saline-treated rats. These observations indicate that endotoxin increases fecal pellet output through a nervous reflex in which capsaicin-sensitive afferent neurons and the release of excitatory (acetylcholine and substance P) and inhibitory (NO) neurotransmitters in the colonic wall are involved.

Progastrin represses the alternative activation of human macrophages and modulates their influence on colon cancer epithelial cells.

Macrophage infiltration is a negative prognostic factor for most cancers but gastrointestinal tumors seem to be an exception. The effect of macrophages on cancer progression depends on their phenotype, which may vary between M1 (pro-inflammatory, defensive) to M2 (tolerogenic, pro-tumoral). Gastrointestinal cancers often become an ectopic source of gastrins and macrophages present receptors for these peptides. The aim of the present study is to analyze whether gastrins can affect the pattern of macrophage infiltration in colorectal tumors. We have evaluated the relationship between gastrin expression and the pattern of macrophage infiltration in samples from colorectal cancer and the influence of these peptides on the phenotype of macrophages differentiated from human peripheral monocytes in vitro. The total number of macrophages (CD68+ cells) was similar in tumoral and normal surrounding tissue, but the number of M2 macrophages (CD206+ cells) was significantly higher in the tumor. However, the number of these tumor-associated M2 macrophages correlated negatively with the immunoreactivity for gastrin peptides in tumor epithelial cells. Macrophages differentiated from human peripheral monocytes in the presence of progastrin showed lower levels of M2-markers (CD206, IL10) with normal amounts of M1-markers (CD86, IL12). Progastrin induced similar effects in mature macrophages treated with IL4 to obtain a M2-phenotype or with LPS plus IFNγ to generate M1-macrophages. Macrophages differentiated in the presence of progastrin presented a reduced expression of Wnt ligands and decreased the number and increased cell death of co-cultured colorectal cancer epithelial cells. Our results suggest that progastrin inhibits the acquisition of a M2-phenotype in human macrophages. This effect exerted on tumor associated macrophages may modulate cancer progression and should be taken into account when analyzing the therapeutic value of gastrin immunoneutralization.

Nitric oxide induces HIF-1α stabilization and expression of intestinal trefoil factor in the damaged rat jejunum and modulates ulcer healing.

BACKGROUND: The induction of intestinal trefoil factor (ITF) has been reported to depend on hypoxia-inducible factor-1 (HIF-1). Nitric oxide modulates HIF-1 activity. The present study aims to analyze the role of nitric oxide in jejunum damage induced by indomethacin and its ability to modulate epithelial function through the expression of ITF. METHODS: Rats received indomethacin (7.5 mg/kg, s.c., twice), and a time course analysis of damage was performed (24-96 h after the first administration). In these animals, the role of nitric oxide was analyzed by using 1400W, a selective iNOS activity inhibitor (5 mg/kg, i.p./day), on: (1) intestinal damage, (2) ulcer healing, (3) the presence of nitrated proteins in the jejunum and (4) the protein expression of inducible nitric oxide synthase (iNOS), HIF-1α and ITF. RESULTS: Indomethacin induced damage in the jejunum that was apparent at 24 h and peaked at 48-72 h. An increase in iNOS, HIF-1α, ITF and nitrated proteins was observed in the injured jejunum. Immunoprecipitation of HIF-1α allowed determination of the nitration/nitrosylation of this protein by using nitrotyrosine and nitrocysteine antibodies. Blockade of iNOS activity did not significantly modify damage or iNOS expression, but did significantly impede ITF induction, HIF-1α stabilization and HIF-1α detection with antibodies against nitrated proteins. In parallel to these results, pre-treatment with 1400W delayed the healing of the ulcer provoked by indomethacin. CONCLUSIONS: These results suggest that iNOS-derived NO is involved in HIF-1α stabilization, probably through S-nitrosylation, and ITF expression in goblet cells of the damaged jejunum of indomethacin-treated rats and mediates ulcer healing.

Cephalic phase of acid secretion involves activation of medullary TRH receptor subtype 1 in rats.

Mechanisms involved in the cephalic phase of gastric acid secretion were studied in awake fasted rats with chronic gastric fistula and exposed to the sight and smell of chow for 30 min. Acid secretion was monitored using constant intragastric perfusion and automatic titration. Sham feeding induced a peak acid response reaching 82 +/- 7 micromol/10 min within 20 min compared with the average 22 +/- 2 micromol/10 min in controls. The sham-feeding response was abolished by intracisternal pretreatment with the TRH(1)-receptor antisense oligodeoxynucleotides or subcutaneous injection of atropine, whereas TRH(1) mismatch oligodeoxynucleotides had no effect. Serum gastrin was not altered by the sham feeding and increased by refeeding. Gastrin antibody did not block the rise in acid during sham feeding, although the net acid response was reduced by 47% compared with the control group. Glycine-gastrin antibody, indomethacin and nitro-l-arginine methyl ester had no effect. Atropine and gastrin antibody decreased basal acid secretion by 98 and 75%, respectively, whereas all other pretreatments did not. These results indicate that the cholinergic-dependent acid response to sham feeding is mediated by brain medullary TRH(1) receptors in rats.

Downregulation of nNOS and synthesis of PGs associated with endotoxin-induced delay in gastric emptying.

A single intraperitoneal injection of endotoxin (40 microg/kg) significantly delayed gastric emptying of a solid nutrient meal. Blockade of nitric oxide synthase (NOS) with 30 mg/kg ip N(G)-nitro-L-arginine methyl ester or 20 mg/kg ip 7-nitroindazole [neuronal NOS (nNOS) inhibitor] significantly delayed gastric emptying in control animals but failed to modify gastric emptying in endotoxin-treated rats. Administration of 2.5, 5, and 10 mg/kg ip N(6)-iminoethyl-L-lysine [inducible NOS (iNOS) inhibitor] had no effect in either experimental group. Indomethacin (5 mg/kg sc), NS-398 (cyclooxygenase-2 inhibitor; 10 mg/kg ip), and dexamethasone (10 mg/kg sc) but not quinacrine (20 mg/kg ip) significantly prevented delay in gastric emptying induced by endotoxin but failed to modify gastric emptying in vehicle-treated animals. Ca(2+)-dependent NOS activity in the antrum pylorus of the stomach was diminished by endotoxin, whereas Ca(2+)-independent NOS activity was not changed. In addition, decreased nNOS mRNA and protein were observed in the antrum pylorus of endotoxin-treated rats. Our results suggest that downregulation of nNOS in the antrum pylorus of the stomach and synthesis of prostaglandins mediate the delay in gastric emptying of a solid nutrient meal induced by endotoxin.