Melatonin-Activated Receptor Signaling Pathways Mediate Protective Effects on Surfactant-Induced Increase in Jejunal Mucosal Permeability in Rats.

A well-functional intestinal mucosal barrier can be compromised as a result of various diseases, chemotherapy, radiation, and chemical exposures including surfactants. Currently, there are no approved drugs targeting a dysfunctional intestinal barrier, which emphasizes a significant medical need. One candidate drug reported to regulate intestinal mucosal permeability is melatonin. However, it is still unclear if its effect is primarily receptor mediated or antioxidative, and if it is associated with enteric neural pathways. The aim of this rat intestinal perfusion study was to investigate the mechanisms of melatonin and nicotinic acetylcholine receptors on the increase in intestinal mucosal clearance of 51Cr-labeled ethylenediaminetetraacetate induced by 15 min luminal exposure to the anionic surfactant, sodium dodecyl sulfate. Our results show that melatonin abolished the surfactant-induced increase in intestinal permeability and that this effect was inhibited by luzindole, a melatonin receptor antagonist. In addition, mecamylamine, an antagonist of nicotinic acetylcholine receptors, reduced the surfactant-induced increase in mucosal permeability, using a signaling pathway not influenced by melatonin receptor activation. In conclusion, our results support melatonin as a potentially potent candidate for the oral treatment of a compromised intestinal mucosal barrier, and that its protective effect is primarily receptor-mediated.

Elevated postischemic tissue injury and leukocyte-endothelial adhesive interactions in mice with global deficiency in caveolin-2: role of PAI-1.

Ischemia/reperfusion (I/R)-induced rapid inflammation involving activation of leukocyte-endothelial adhesive interactions and leukocyte infiltration into tissues is a major contributor to postischemic tissue injury. However, the molecular mediators involved in this pathological process are not fully known. We have previously reported that caveolin-2 (Cav-2), a protein component of plasma membrane caveolae, regulated leukocyte infiltration in mouse lung carcinoma tumors. The goal of the current study was to examine if Cav-2 plays a role in I/R injury and associated acute leukocyte-mediated inflammation. Using a mouse small intestinal I/R model, we demonstrated that I/R downregulates Cav-2 protein levels in the small bowel. Further study using Cav-2-deficient mice revealed aggravated postischemic tissue injury determined by scoring of villi length in H&E-stained tissue sections, which correlated with increased numbers of MPO-positive tissue-infiltrating leukocytes determined by IHC staining. Intravital microscopic analysis of upstream events relative to leukocyte transmigration and tissue infiltration revealed that leukocyte-endothelial cell adhesive interactions in postcapillary venules, namely leukocyte rolling and adhesion were also enhanced in Cav-2-deficient mice. Mechanistically, Cav-2 deficiency increased plasminogen activator inhibitor-1 (PAI-1) protein levels in the intestinal tissue and a pharmacological inhibition of PAI-1 had overall greater inhibitory effect on both aggravated I/R tissue injury and enhanced leukocyte-endothelial interactions in postcapillary venules in Cav-2-deficient mice. In conclusion, our data suggest that Cav-2 protein alleviates tissue injury in response to I/R by dampening PAI-1 protein levels and thereby reducing leukocyte-endothelial adhesive interactions.NEW & NOTEWORTHY The role of caveolin-2 in regulating ischemia/reperfusion (I/R) tissue injury and the mechanisms underlying its effects are unknown. This study uses caveolin-2-deficient mouse and small intestinal I/R injury models to examine the role of caveolin-2 in the leukocyte-dependent reperfusion injury. We demonstrate for the first time that caveolin-2 plays a protective role from the I/R-induced leukocyte-dependent reperfusion injury by reducing PAI-1 protein levels in intestinal tissue and leukocyte-endothelial adhesive interactions in postcapillary venules.

Identification of Circular RNAs Altered in Mouse Jejuna After Radiation.

BACKGROUND/AIMS: Circular RNAs (circRNAs) make up a large class of non-coding RNAs and play important roles in a variety of diseases, including nervous system diseases and cancers. The intestinal epithelium is sensitive to ionizing radiation, radiotherapy of abdominal or pelvic tumors or nuclear accident exposure can lead to high radiation toxicity, which can result in radiation-induced intestinal injury. The goal of this present study was to analyze the potential roles of circRNAs in radiation-induced intestinal injury. METHODS: Mice were divided into two groups: control group and irradiated group. Irradiated group was 3.5 days after 14Gy abdominal irradiation (ABI) group. We started with RNA-seq of circRNA changes in mouse jejuna after radiation and validated by RT-PCR in the following experimental. miRNAs targeted mRNAs were predicted using proprietary software based on target scan and Miranda. The network of circRNA-miRNA-mRNA was illustrated by cytoscape software. RESULTS: 2751 circRNAs were detected in the two groups. At day 3.5 post-radiation, 42 and 48 circRNAs were found to be significantly upregulated and downregulated, respectively, compared to the control (p≤0.05, Fold Change ≥2). Further, the altered expression of 10 circRNAs (chr18: 35610871-35613502+, chr15: 95864225-95894541+, chr3: 96041338-96042928-, chr5: 64096979-64108263+, chr19: 16705875-16710941-, chr5: 134491893-134500149-, chr19: 42562552-42564341+, chr5: 32640331-32664400+, chr3: 72958113-72960367- and chr8: 79343654-79372364-) were verified by RT-PCR. Compared the miRNA-targeted mRNAs with our mRNAs sequencing data, we found 14 upregulated circRNA-targeted mRNAs were also unregulated and 22 downregulated circRNAs-targeted mRNAs were also downregulated. Gene ontology and KEGG pathway analyses indicated the predicted genes were mainly involved in the MAPK signaling pathway. CONCLUSIONS: This study reveals that expression of circRNAs was altered in the jejuna of mice post-irradiation and provides a resource for the study of circRNAs in radiation-induced intestinal injury and repair.

Octreotide modulates the expression of somatostatin receptor subtypes in inflamed rat jejunum induced by Cryptosporidium parvum.

Somatostatins are proteins that are involved in gastrointestinal function. However, little is known with regard to somatostatin receptor subtype (SSTR) expression changes that occur in the jejunum during low-grade inflammation and during subsequent octreotide treatment. The aim of the present study was to investigate the expression of SSTRs in the jejunums of Cryptosporidium parvum (C. parvum)-infected rats by immunohistochemisty, reverse transcription (RT) PCR and quantitative real-time RT-PCR assays. Five-day-old suckling Sprague-Dawley rats (n = 15 for each group) were orally gavaged with 105 Nouzilly isolate (NoI) oocysts. Rats then received 50 µg/kg/day of octreotide by intraperitoneal injection from day 10 to day 17 post-infection. Animals were sacrificed on days 7 and 14 post-infection for immunohistochemical analysis and on days 14, 35 and 50 for mRNA expression analysis of SSTR subtypes. Histological analysis of jejunum tissues demonstrated infection of C. parvum along the villus brush border on day 7 post-infection and infection clearance by day 14 post-infection. Real-time PCR analysis indicated that in the inflamed jejunum, a significant increase in SSTR1 and SSTR2 expression was observed on day 14 post-infection. Octreotide therapy down-regulated the expression of SSTR2 on day 37 post-infection but significantly increased expression of SSTR1, SSTR2 and SSTR3 on day 50 post-infection. The results indicate that specific SSTRs may regulate the inflammatory pathway in the rat intestinal inflammation model.

Continuous-Flow LVAD Support Causes a Distinct Form of Intestinal Angiodysplasia.

RATIONALE: The objective of this autopsy study was to determine whether gastrointestinal angiodysplasia develops during continuous-flow left ventricular assist device (LVAD) support. OBJECTIVE: LVAD support causes pathologic degradation of von Willebrand factor (vWF) and bleeding from gastrointestinal angiodysplasia at an alarming rate. It has been speculated that LVAD support itself may cause angiodysplasia. The relationship to abnormal vWF metabolism is unknown. We tested the hypothesis that abnormal gastrointestinal vascularity develops during continuous-flow LVAD support. METHODS AND RESULTS: Small bowel was obtained from deceased humans, cows, and sheep supported with a continuous-flow LVAD (n=9 LVAD, n=11 control). Transmural sections of jejunum were stained with fluorescein isothiocyanate-conjugated isolectin-B4 for endothelium to demarcate vascular structures and quantify intestinal vascularity. Paired plasma samples were obtained from humans before LVAD implantation and during LVAD support (n=41). vWF multimers and degradation fragments were quantified with agarose and polyacrylamide gel electrophoresis and immunoblotting. Abnormal vascular architecture was observed in the submucosa of the jejunum of human patients, cows, and sheep supported with a continuous-flow LVAD. Intestinal vascularity was significantly higher after LVAD support versus controls (5.2±1.0% versus 2.1±0.4%, P=0.004). LVAD support caused significant degradation of high-molecular-weight vWF multimers (-9±1%, P<0.0001) and accumulation of low-molecular-weight vWF multimers (+40±5%, P<0.0001) and vWF degradation fragments (+53±6%, P<0.0001). CONCLUSIONS: Abnormal intestinal vascular architecture and LVAD-associated vWF degradation were consistent findings in multiple species supported with a continuous-flow LVAD. These are the first direct evidence that LVAD support causes gastrointestinal angiodysplasia. Pathologic vWF metabolism may be a mechanistic link between LVAD support, abnormal angiogenesis, gastrointestinal angiodysplasia, and bleeding.

Nitric oxide-induced oxidative stress impairs pacemaker function of murine interstitial cells of Cajal during inflammation.

The pacemaker function of interstitial cells of Cajal (ICC) is impaired during intestinal inflammation. The aim of this study is to clarify the pathophysiological mechanisms of ICC dysfunction during inflammatory condition by using intestinal cell clusters. Cell clusters were prepared from smooth muscle layer of murine jejunum and treated with interferon-gamma and lipopolysaccharide (IFN-γ+LPS) for 24h to induce inflammation. Pacemaker function of ICC was monitored by measuring cytosolic Ca(2+) oscillation in the presence of nifedipine. Treatment with IFN-γ+LPS impaired the pacemaker activity of ICC with increasing mRNA level of interleukin-1 beta, tumor necrosis factor-alpha and interleukin-6 in cell clusters; however, treatment with these cytokines individually had little effect on pacemaker activity of ICC. Treatment with IFN-γ+LPS also induced the expression of inducible nitric oxide synthase (iNOS) in smooth muscle cells and resident macrophages, but not in ICC. Pretreatment with NOS inhibitor, L-NAME or iNOS inhibitor, 1400W ameliorated IFN-γ+LPS-induced pacemaker dysfunction of ICC. Pretreatment with guanylate cyclase inhibitor, ODQ did not, but antioxidant, apocynin, to suppress NO-induced oxidative stress, significantly suppressed the impairment of ICC function induced by IFN-γ+LPS. Treatment with IFN-γ+LPS also decreased c-Kit-positive ICC, which was prevented by pretreatment with L-NAME. However, apoptotic ICC were not detected in IFN-γ+LPS-treated clusters, suggesting IFN-γ+LPS stimulation just changed the phenotype of ICC but not induced cell death. Moreover, ultrastructure of ICC was not disturbed by IFN-γ+LPS. In conclusion, ICC dysfunction during inflammation is induced by NO-induced oxidative stress rather than NO/cGMP signaling. NO-induced oxidative stress might be the main factor to induce phenotypic changes of ICC.

Protective Effects of Vitamin E on Methotrexate-Induced Jejunal Mucosal Damage in Rats.

OBJECTIVE: To investigate the possible protective effects of Vitamin E (Vit E) on oxidative stress and jejunal damage in the rat intestinal mucosa after methotrexate (MTX)-induced enterotoxicity. STUDY DESIGN: Rats were divided into 3 groups: control, MTX, and MTX+ Vit E; each group contained 8 animals. The control group was given physiological serum in addition to sunflower oil for 3 days. The second group was given sunflower oil with intragastric tube daily, followed by MTX injection (20 mg/kg intraperitoneally). To the third group, starting 3 days before injection, Vit E was given dissolved in sunflower oil (600 mg/kg orally) in addition to MTX injection. Four days after MTX injection the anesthetized rats were sacrificed, and the tissue samples obtained from their jejunums were investigated for histological and biochemical analysis. RESULTS: Vit E treatment significantly decreased the elevated tissue malondialdehyde levels and increased the reduced glutathione peroxidase and superoxide dismutase activities in comparison to the MTX-treated group. MTX treatment caused severe histopathological injury including mucosal erosions, inflammatory cell infiltration, necrosis, hemorrhage, and villous congestion. Vit E treatment significantly attenuated the severity of intestinal injury caused by MTX via inhibiting induced nitric oxide synthase levels and NF-κB p65 activation. CONCLUSION: Because of its reconstructing and antioxidant effects, Vit E pretreatment may have protective effects in the intestinal tissue of MTX-treated rats.

Glutamine ameliorates intestinal ischemia-reperfusion Injury in rats by activating the Nrf2/Are signaling pathway.

Ischemia-reperfusion (I/R)-mediated intestinal mucosal injury is usually induced by oxygen-derived toxic free radicals from the xanthine oxidase system after reperfusion, but the detailed molecular mechanisms underlying glutamine protection is still unclear. This study aims to elucidate whether glutamine prevents damage to the intestinal mucosa after I/R in rats and to investigate signaling by the Nrf2/ARE pathway induced by GLN in a rat model. Our results revealed that Glutamine pretreatment reduced jejunum injury and microvascular hyper-permeability induced by I/R. MDA level significantly increased while the SOD and GSH-Px levels decreased in the I/R group compared to the sham group and the GLN-I/R group. Both the mRNA and protein levels of the Nrf2 and HO-1 were significantly elevated by GLN pretreatment when compared to the I/R group. GLN treatment also elevated Bcl-2 levels, and accordingly suppressed apoptotic damage in the jejunum cells shown by decreased cleaved caspase-3 level. Mechanistic investigation revealed that GLN treatment augmented binding of Nrf2 onto Bcl2 gene promoter. These results indicate that glutamine has protective effects on I/R in vivo by activating the Nrf2/ARE signaling pathway to inhibit ROS production and reduce intestinal apoptosis.

Pseudomelanosis of stomach, duodenum, and jejunum.

Pseudomelanosis is a rare finding during upper gastrointestinal endoscopy, and is most commonly seen in the duodenum. Involvement of other organs in the upper gastrointestinal tract is extremely rare, with only 1 reported case involving the stomach, duodenum, and jejunum. We present a case of a 60-year-old woman with mild anemia and hematemesis, who was found to have characteristic speckled pattern of gray-black pigmentation on endoscopic examination. To the best of our knowledge, this is the second reported case of pseudomelanosis involving the stomach, duodenum, and jejunum.

Elastofibromatous change of the intestine: report of four lesions from three patients with review of the literature.

Elastofibromatous change, also referred to as elastofibromatous polyp or elastofibroma, has been extremely rarely described in the gastrointestinal tract. This lesion is characterized histopathologically by an excessive accumulation of elastic fibers occasionally with a fibrous component involving the submucosa and/or muscularis mucosae of the gastrointestinal tract. Herein, we report four additional lesions of the intestine and review the clinicopathological features of this rare lesion. Three patients (76-, 72-, and 52-year-old males) were detected with polypoid lesions in the jejunum, transverse and sigmoid colons, and sigmoid colon, respectively. All four lesions showed fundamentally the same histopathological and immunohistochemical features. The polypoid lesions were covered by non-neoplastic epithelium, and degenerated and truncated elastic fibers occasionally with a fibrous component had accumulated in the submucosa and/or muscularis mucosae. The characteristic feature was the elastofibromatous change centered around collections of elastotic submucosal vessels. Desmin-positive degenerative ruptured smooth muscle fibers were scattered within the elastic fibers in the submucosa. Our analyses of the clinicopathological features of the previously reported 32 cases of elastofibromatous change of the gastrointestinal tract as well as the present cases demonstrated that this type of lesion is most commonly found in the colon or rectum (29 cases), males, and middle-aged to elderly persons. Although the pathogenesis remains unclear, the convincing hypothesis that this lesion represents elastic degeneration of submucosal vessels by previous persistent vascular injury has been proposed. The collections of degenerative elastotic vascular walls may have an important role in the development of this lesion.

Absence of intestinal inflammation and postoperative ileus in a mouse model of laparoscopic surgery.

BACKGROUND: Postoperative ileus (POI) is characterized by impaired gastrointestinal motility resulting from intestinal handling-associated inflammation. The introduction of laparoscopic surgery has dramatically reduced the duration of POI. However, it remains unclear to what extent this results in a reduction of intestinal inflammation. The aim of the present study is to compare the degree of intestinal inflammation and gastrointestinal transit following laparoscopic surgery and open abdominal surgery. METHODS: Mice were subjected to laparoscopic surgery or laparotomy alone or, in combination with standardized intestinal manipulation of the small bowel (IM). Gastrointestinal transit and intestinal inflammation were assessed 24 h after surgery by the number of myeloperoxidase (MPO) positive cells and the level of cytokine expression. The recovery time and the degree of inflammation were also analyzed in patients subjected to colectomy under open conditions (laparotomy) or laparoscopic conditions. KEY RESULTS: Mice undergoing IM by laparotomy (open IM), but not by laparoscopy (Lap IM) developed a significant delay in gastrointestinal transit compared to laparotomy or laparoscopy alone. In addition, there was significant intestinal inflammation only after open IM. Similarly, cytokine levels in peritoneal lavage fluid were lower while recovery time was faster in patients subjected to colectomy under laparoscopic conditions compared to open colectomy. CONCLUSIONS & INFERENCES: Our data confirms that intestinal inflammation is underlying the delayed gastrointestinal transit observed after open surgery. Most importantly, we demonstrate that intestinal inflammation under laparoscopic conditions is significantly lower compared to open surgery, most likely explaining the faster recovery following laparoscopic surgery.

Glucose absorption in small intestinal diseases.

Recent developments in the field of diabetes and obesity management have established the central role of the gut in glucose homeostasis; not only is the gut the primary absorptive site, but it also triggers neurohumoral feedback responses that regulate the pre- and post-absorptive phases of glucose metabolism. Structural and/or functional disorders of the intestine have the capacity to enhance (e.g.: diabetes) or inhibit (e.g.: short-gut syndrome, critical illness) glucose absorption, with potentially detrimental outcomes. In this review, we first describe the normal physiology of glucose absorption and outline the methods by which it can be quantified. Then we focus on the structural and functional changes in the small intestine associated with obesity, critical illness, short gut syndrome and other malabsorptive states, and particularly Type 2 diabetes, which can impact upon carbohydrate absorption and overall glucose homeostasis.

[Involvement of endogenous tachykinins in the development of jejunal mucosa injury induced by on-steroidal anti-inflammatory drugs]. / Udzial endogennych tachykinin w powstawaniu uszkodzen blony sluzowej jelita czczego wywolanych niesterydowymi lekami przeciwzapalnymi.

UNLABELLED: Previous studies have shown that tachykinins, the largest family of neuropeptides, affect the development of mucosal damage in the stomach and colon. The aim of the study was to assess the influence of tachykinins receptors antagonists on the development of the mucosa injury in the proximal and distal jejunum. MATERIAL AND METHODS: Mucosal damage was induced by administration of non-steroidal anti inflammatory drugs (NSAIDs), indomethacin, celecoxib or combination of indomethacin plus celecoxib given intragastrically. NK-1 receptor antagonist (SR 140333), NK-2 receptor antagonist (SR 48968) and NK-3 receptor antagonist (SR 142801) were administered intraperitoneally twice, 30 min before treatment with NSAID and again 24 h later, 30 min before the end of the experiment. RESULTS: Administration of indomethacin, a relatively selective inhibitor for cyclooxygenase-1 (COX-1), induced mucosal lesions in the jejunum. Lesions area in the distal jejunum was 8-fold bigger than in the proximal jejunum. This effect was associated with a significant reduction in mucosal blood flow and an increase in mucosal concentration of pro-inflammatory interleukin-1beta (IL-1beta). Celecoxib, selective inhibitor for COX-2 failed to induce mucosal lesions and did not affect the mucosal blood flow and IL-1beta concentration in the proximal and distal jejunum. In rats treated with a combination of indomethacin plus celecoxib, ulcers reached maximal area. This effect was associated with the highest concentration of mucosal IL-1beta and maximal reduction in mucosal blood flow. Administration of NK-1 receptor antagonist, SR 140333 reduced jejunal damage induced by indomethacin given alone or in combination with celecoxib. This effect was associated with significant reduction in mucosal concentration of IL-1beta. Effect of SR 140333 on mucosal blood flow was statistically insignificant. Neither NK-2 nor NK-3 receptor inhibitor affected mucosal blood flow, IL-1beta concentration area of NSAIDs-induced mucosal damage in the jejunum. CONCLUSIONS: Blockade of NK-1 receptor protects the jejunum against NSAIDs-induced mucosal injury and reduces local inflammation. This observation indicates the involvement of endogenous tachykinins in deleterious effects of NSAID.

Increased expression of 5-HT3 and NK 1 receptors in 5-fluorouracil-induced mucositis in mouse jejunum.

BACKGROUND AND OBJECTIVE: Although 5-fluorouracil (5-FU) is a widely used as chemotherapy agent, severe mucositis develops in approximately 80% of patients. 5-FU-induced small intestinal mucositis can cause nausea and vomiting. The current study was designed to investigate peripheral alterations due to the 5-FU-induced mucositis of neuronal and non-neuronal 5-HT3 and NK1 receptor expression by immunohistochemical analysis. METHODS: 5-FU was administered by i.p. injection to C57BL/6 mice. After 4 days, segments of the jejunum were removed. The specimens were analyzed by immunohistochemistry, real-time PCR, and enzyme immunoassay. RESULTS: The numbers of 5-HT3 receptor immunopositive cells and nerve fibers in mucosa were increased by 5-FU treatment. The 5-HT3 receptor immunopositive cell bodies were found only in jejunal submucosa and myenteric plexus in the 5-FU-treated mice. The numbers of NK1 receptor cells in mucosa and immunopositive expression of NK1 receptors in deep muscular plexus were dramatically increased in 5-FU-treated mice. Real-time PCR demonstrated that 5-FU treatment significantly increased mRNA levels of 5-HT3A, 5-HT3B, and NK1 receptors. The amounts of 5-HT and substance P increased after 5-FU treatment. The 5-HT3 or NK1 receptor immunopositive cells colocalized with both 5-HT and substance P. Furthermore, 5-HT3 and NK1 receptors colocalized with CD11b. CONCLUSIONS: The 5-HT3 and NK1 immunopositive macrophages and mucosal mast cells in lamina propria release 5-HT and substance P, which in turn activate their corresponding receptors on mucosal cells in autocrine and paracrine manners. It is assumed to result in the release of 5-HT and substance P in mucosa.