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PubMed Central (PMC3 - NLM DTD) (2,833,227 recursos)
Archive of life sciences journal literature at the U.S. National Institutes of Health (NIH), developed and managed by NIH's National Center for Biotechnology Information (NCBI) in the National Library of Medicine (NLM).

American Journal of Physiology - Gastrointestinal and Liver Physiology

Mostrando recursos 1 - 20 de 877

1. Mesenchymal stem cells induce epithelial proliferation within the inflamed stomach - Donnelly, Jessica M.; Engevik, Amy; Feng, Rui; Xiao, Chang; Boivin, Gregory P.; Li, Jing; Houghton, JeanMarie; Zavros, Yana
Bone marrow-derived mesenchymal stem cells (MSCs) sustain cancer cells by creating a microenvironment favorable for tumor growth. In particular, MSCs have been implicated in gastric cancer development. There is extensive evidence suggesting that Hedgehog signaling regulates tumor growth. However, very little is known regarding the precise roles of Hedgehog signaling and MSCs in tumor development within the stomach. The current study tests that hypothesis that Sonic Hedgehog (Shh), secreted from MSCs, provides a proliferative stimulus for the gastric epithelium in the presence of inflammation. Red fluorescent protein-expressing MSCs transformed in vitro (stMSCs) were transduced with lentiviral constructs containing a vector...

2. Hyperosmolarity in the small intestine contributes to postprandial ghrelin suppression - Overduin, Joost; Tylee, Tracy S.; Frayo, R. Scott; Cummings, David E.
Plasma levels of the orexigenic hormone ghrelin are suppressed by meals with an efficacy dependent on their macronutrient composition. We hypothesized that heterogeneity in osmolarity among macronutrient classes contributes to these differences. In three studies, the impact of small intestinal hyperosmolarity was examined in Sprague-Dawley rats. In study 1, isotonic, 2.5×, and 5× hypertonic solutions of several agents with diverse absorption and metabolism properties were infused duodenally at a physiological rate (3 ml/10 min). Jugular vein blood was sampled before and at 30, 60, 90, 120, 180, 240, and 300 min after infusion. Plasma ghrelin was suppressed dose dependently and...

3. RNA sequencing shows transcriptomic changes in rectosigmoid mucosa in patients with irritable bowel syndrome-diarrhea: a pilot case-control study - Camilleri, Michael; Carlson, Paula; Acosta, Andres; Busciglio, Irene; Nair, Asha A.; Gibbons, Simon J.; Farrugia, Gianrico; Klee, Eric W.
Our aim was to conduct a pilot case-control study of RNA expression profile using RNA sequencing of rectosigmoid mucosa of nine females with -diarrhea-predominant irritable bowel syndrome (IBS-D) with accelerated colonic transit and nine female healthy controls. Mucosal total RNA was isolated and purified, and next-generation pair-end sequencing was performed using Illumina TruSeq. Analysis was carried out using a targeted approach toward 12 genes previously associated with IBS and a hypothesis-generating approach. Of the 12 targeted genes tested, patients with IBS-D had decreased mRNA expression of TNFSF15 (fold change controls to IBS-D: 1.53, P = 0.01). Overall, up- and downregulated...

4. Ron receptor signaling is protective against DSS-induced colitis in mice - Kulkarni, Rishikesh M.; Stuart, William D.; Gurusamy, Devikala; Waltz, Susan E.
Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of the intestine that result in painful and debilitating complications. Currently no cure exists for IBD, and treatments are primarily aimed at reducing inflammation to alleviate symptoms. Genome-wide linkage studies have identified the Ron receptor tyrosine kinase (TK) and its ligand, hepatocyte growth factor-like protein (HGFL), as genes highly associated with IBD. However, only scant information exists on the role of Ron or HGFL in IBD. Based on the linkage of Ron to IBD, we directly examined the biological role of Ron in colitis. Wild-type mice and mice lacking the TK signaling...

5. Colonic inflammation and secondary bile acids in alcoholic cirrhosis - Kakiyama, Genta; Hylemon, Phillip B.; Zhou, Huiping; Pandak, William M.; Heuman, Douglas M.; Kang, Dae Joong; Takei, Hajime; Nittono, Hiroshi; Ridlon, Jason M.; Fuchs, Michael; Gurley, Emily C.; Wang, Yun; Liu, Runping; Sanyal, Arun J.; Gillevet, Patrick M.; Bajaj, Jasmohan S.
Alcohol abuse with/without cirrhosis is associated with an impaired gut barrier and inflammation. Gut microbiota can transform primary bile acids (BA) to secondary BAs, which can adversely impact the gut barrier. The purpose of this study was to define the effect of active alcohol intake on fecal BA levels and ileal and colonic inflammation in cirrhosis. Five age-matched groups {two noncirrhotic (control and drinkers) and three cirrhotic [nondrinkers/nonalcoholics (NAlc), abstinent alcoholic for >3 mo (AbsAlc), currently drinking (CurrAlc)]} were included. Fecal and serum BA analysis, serum endotoxin, and stool microbiota using pyrosequencing were performed. A subgroup of controls, NAlc, and...

6. Disruption of epithelial barrier by quorum-sensing N-3-(oxododecanoyl)-homoserine lactone is mediated by matrix metalloproteinases - Eum, Sung Yong; Jaraki, Dima; Bertrand, Luc; András, Ibolya E.; Toborek, Michal
The intestinal epithelium forms a selective barrier maintained by tight junctions (TJs) and separating the luminal environment from the submucosal tissues. N-acylhomoserine lactone (AHL) quorum-sensing molecules produced by gram-negative bacteria in the gut can influence homeostasis of the host intestinal epithelium. In the present study, we evaluated the regulatory mechanisms affecting the impact of two representative long- and short-chain AHLs, N-3-(oxododecanoyl)-homoserine lactone (C12-HSL) and N-butyryl homoserine lactone (C4-HSL), on barrier function of human intestinal epithelial Caco-2 cells. Treatment with C12-HSL, but not with C4-HSL, perturbed Caco-2 barrier function; the effect was associated with decreased levels of the TJ proteins occludin...

7. Acute murine colitis reduces colonic 5-aminosalicylic acid metabolism by regulation of N-acetyltransferase-2 - Ramírez-Alcántara, Verónica; Montrose, Marshall H.
Pharmacotherapy based on 5-aminosalicylic acid (5-ASA) is a preferred treatment for ulcerative colitis, but variable patient response to this therapy is observed. Inflammation can affect therapeutic outcomes by regulating the expression and activity of drug-metabolizing enzymes; its effect on 5-ASA metabolism by the colonic arylamine N-acetyltransferase (NAT) enzyme isoforms is not firmly established. We examined if inflammation affects the capacity for colonic 5-ASA metabolism and NAT enzyme expression. 5-ASA metabolism by colonic mucosal homogenates was directly measured with a novel fluorimetric rate assay. 5-ASA metabolism reported by the assay was dependent on Ac-CoA, inhibited by alternative NAT substrates (isoniazid, p-aminobenzoylglutamate),...

8. Pharmacological ceramide reduction alleviates alcohol-induced steatosis and hepatomegaly in adiponectin knockout mice - Correnti, Jason M.; Juskeviciute, Egle; Swarup, Aditi; Hoek, Jan B.
Hepatosteatosis, the ectopic accumulation of lipid in the liver, is one of the earliest clinical signs of alcoholic liver disease (ALD). Alcohol-dependent deregulation of liver ceramide levels as well as inhibition of AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor α (PPAR-α) activity are thought to contribute to hepatosteatosis development. Adiponectin can regulate lipid handling in the liver and has been shown to reduce ceramide levels and activate AMPK and PPAR-α. However, the mechanisms by which adiponectin prevents alcoholic hepatosteatosis remain incompletely characterized. To address this question, we assessed ALD progression in wild-type (WT) and adiponectin knockout (KO) mice fed...

9. Lactobacillus rhamnosus HN001 decreases the severity of necrotizing enterocolitis in neonatal mice and preterm piglets: evidence in mice for a role of TLR9 - Good, Misty; Sodhi, Chhinder P.; Ozolek, John A.; Buck, Rachael H.; Goehring, Karen C.; Thomas, Debra L.; Vikram, Amit; Bibby, Kyle; Morowitz, Michael J.; Firek, Brian; Lu, Peng; Hackam, David J.
Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants and develops partly from an exaggerated intestinal epithelial immune response to indigenous microbes. There has been interest in administering probiotic bacteria to reduce NEC severity, yet concerns exist regarding infection risk. Mechanisms of probiotic activity in NEC are unknown although activation of the microbial DNA receptor Toll-like receptor-9 (TLR9) has been postulated. We now hypothesize that the Gram-positive bacterium Lactobacillus rhamnosus HN001 can attenuate NEC in small and large animal models, that its microbial DNA is sufficient for its protective effects, and that protection requires...

10. Differential eosinophil and mast cell regulation: Mast cell viability and accumulation in inflammatory tissue are independent of proton-sensing receptor GPR65 - Zhu, Xiang; Mose, Eucabeth; Hogan, Simon P.; Zimmermann, Nives
Extracellular acidification has been observed in allergic inflammatory diseases. Recently, we demonstrated that the proton-sensing receptor G protein-coupled receptor 65 (GPR65) regulates eosinophil survival in an acidic environment in vitro and eosinophil accumulation in an allergic lung inflammation model. For mast cells, another inflammatory cell type critical for allergic responses, it remains unknown whether GPR65 is expressed and/or regulates mast cell viability. Thus, in the present study, we employed in vitro experiments and an intestinal anaphylaxis model in which both mastocytosis and eosinophilia can be observed, particularly in the gastrointestinal tract, to enable us to directly compare the effect of...

11. Cyclic stretch disrupts apical junctional complexes in Caco-2 cell monolayers by a JNK-2-, c-Src-, and MLCK-dependent mechanism - Samak, Geetha; Gangwar, Ruchika; Crosby, Lynn M.; Desai, Leena P.; Wilhelm, Kristina; Waters, Christopher M.; Rao, RadhaKrishna
The intestinal epithelium is subjected to various types of mechanical stress. In this study, we investigated the impact of cyclic stretch on tight junction and adherens junction integrity in Caco-2 cell monolayers. Stretch for 2 h resulted in a dramatic modulation of tight junction protein distribution from a linear organization into wavy structure. Continuation of cyclic stretch for 6 h led to redistribution of tight junction proteins from the intercellular junctions into the intracellular compartment. Disruption of tight junctions was associated with redistribution of adherens junction proteins, E-cadherin and β-catenin, and dissociation of the actin cytoskeleton at the actomyosin belt....

12. Triptolide activates unfolded protein response leading to chronic ER stress in pancreatic cancer cells - Mujumdar, Nameeta; Banerjee, Sulagna; Chen, Zhiyu; Sangwan, Veena; Chugh, Rohit; Dudeja, Vikas; Yamamoto, Masato; Vickers, Selwyn M.; Saluja, Ashok K.
Pancreatic cancer is a devastating disease with a survival rate of <5%. Moreover, pancreatic cancer aggressiveness is closely related to high levels of prosurvival mediators, which can ultimately lead to rapid disease progression. One of the mechanisms that enables tumor cells to evade cellular stress and promote unhindered proliferation is the endoplasmic reticulum (ER) stress response. Disturbances in the normal functions of the ER lead to an evolutionarily conserved cell stress response, the unfolded protein response (UPR). The UPR initially compensates for damage, but it eventually triggers cell death if ER dysfunction is severe or prolonged. Triptolide, a diterpene triepoxide,...

13. Aging-associated oxidative stress leads to decrease in IAS tone via RhoA/ROCK downregulation - Singh, Jagmohan; Kumar, Sumit; Krishna, Chadalavada Vijay; Rattan, Satish
Internal anal sphincter (IAS) tone plays an important role in rectoanal incontinence (RI). IAS tone may be compromised during aging, leading to RI in certain patients. We examined the influence of oxidative stress in the aging-associated decrease in IAS tone (AADI). Using adult (4–6 mo old) and aging (24–30 mo old) rats, we determined the effect of oxidative stress on IAS tone and the regulatory RhoA/ROCK signal transduction cascade. We determined the effect of the oxidative stress inducer LY83583, which produces superoxide anions (O2·−), on basal and stimulated IAS tone before and after treatment of intact smooth muscle strips and...

14. Animal models of gastrointestinal and liver diseases. Animal models of necrotizing enterocolitis: pathophysiology, translational relevance, and challenges - Lu, Peng; Sodhi, Chhinder P.; Jia, Hongpeng; Shaffiey, Shahab; Good, Misty; Branca, Maria F.; Hackam, David J.
Necrotizing enterocolitis is the leading cause of morbidity and mortality from gastrointestinal disease in premature infants and is characterized by initial feeding intolerance and abdominal distention followed by the rapid progression to coagulation necrosis of the intestine and death in many cases. Although the risk factors for NEC development remain well accepted, namely premature birth and formula feeding, the underlying mechanisms remain incompletely understood. Current thinking indicates that NEC develops in response to an abnormal interaction between the mucosal immune system of the premature host and an abnormal indigenous microflora, leading to an exaggerated mucosal inflammatory response and impaired mesenteric...

15. Substance P is essential for maintaining gut muscle contractility: a novel role for coneurotransmission revealed by botulinum toxin - Li, Cuiping; Micci, Maria-Adelaide; Murthy, Karnam S.; Pasricha, Pankaj Jay
Substance P (SP) is commonly coexpressed with ACh in enteric motor neurons, and, according to the classical paradigm, both these neurotransmitters excite smooth muscle via parallel pathways. We hypothesized that, in addition, SP was responsible for maintaining the muscular responsiveness to ACh. We tested this hypothesis by using botulinum toxin (BoNT/A), a known blocker of vesicular release of neurotransmitters including ACh and neuropeptides. BoNT/A was injected into rat pyloric sphincter in different doses; as control we used boiled BoNT/A. At the desired time point, pylorus was dissected out and pyloric contractility was measured ex vivo in an organ bath and...

16. Animals Models of Gastrointestinal and Liver Diseases. Animal models of alcohol-induced liver disease: pathophysiology, translational relevance, and challenges - Mathews, Stephanie; Xu, Mingjiang; Wang, Hua; Bertola, Adeline; Gao, Bin
Over the last four decades, chronic ethanol feeding studies in rodents using either ad libitum feeding or intragastric infusion models have significantly enhanced our understanding of the pathogenesis of alcoholic liver disease (ALD). Recently, we developed a chronic plus binge alcohol feeding model in mice that is similar to the drinking patterns of many alcoholic hepatitis patients: a history of chronic drinking and recent excessive alcohol consumption. Chronic+binge ethanol feeding synergistically induced steatosis, liver injury, and neutrophil infiltration in mice, which may be useful for the study of early alcoholic liver injury and inflammation. Using this chronic+binge model, researchers have...

17. Epithelial VEGF signaling is required in the mouse liver for proper sinusoid endothelial cell identity and hepatocyte zonation in vivo - Walter, Teagan J.; Cast, Ashley E.; Huppert, Kari A.; Huppert, Stacey S.
Vascular endothelial growth factor (VEGF) is crucial for vascular development in several organs. However, the specific contribution of epithelial-VEGF signaling in the liver has not been tested. We used a mouse model to specifically delete Vegf from the liver epithelial lineages during midgestational development and assessed the cell identities and architectures of epithelial and endothelial tissues. We find that without epithelial-derived VEGF, the zonal endothelial and hepatocyte cell identities are altered. We also find decreased portal vein and hepatic artery branching coincident with an increase in hepatic hypoxia postnatally. Together, these data indicate that VEGF secreted from the hepatic epithelium...

18. Intestinal alkaline phosphatase promotes gut bacterial growth by reducing the concentration of luminal nucleotide triphosphates - Malo, Madhu S.; Moaven, Omeed; Muhammad, Nur; Biswas, Brishti; Alam, Sayeda N.; Economopoulos, Konstantinos P.; Gul, Sarah Shireen; Hamarneh, Sulaiman R.; Malo, Nondita S.; Teshager, Abeba; Mohamed, Mussa M. Rafat; Tao, Qingsong; Narisawa, Sonoko; Millán, José Luis; Hohmann, Elizabeth L.; Warren, H. Shaw; Robson, Simon C.; Hodin, Richard A.
The intestinal microbiota plays a pivotal role in maintaining human health and well-being. Previously, we have shown that mice deficient in the brush-border enzyme intestinal alkaline phosphatase (IAP) suffer from dysbiosis and that oral IAP supplementation normalizes the gut flora. Here we aimed to decipher the molecular mechanism by which IAP promotes bacterial growth. We used an isolated mouse intestinal loop model to directly examine the effect of exogenous IAP on the growth of specific intestinal bacterial species. We studied the effects of various IAP targets on the growth of stool aerobic and anaerobic bacteria as well as on a...

19. Role of intracellular calcium and NADPH oxidase NOX5-S in acid-induced DNA damage in Barrett's cells and Barrett's esophageal adenocarcinoma cells - Li, Dan; Cao, Weibiao
Mechanisms whereby acid reflux may accelerate the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. Acid and reactive oxygen species (ROS) have been reported to cause DNA damage in Barrett's cells. We have previously shown that NADPH oxidase NOX5-S is responsible for acid-induced H2O2 production in Barrett's cells and in EA cells. In this study we examined the role of intracellular calcium and NADPH oxidase NOX5-S in acid-induced DNA damage in a Barrett's EA cell line FLO and a Barrett's cell line CP-A. We found that pulsed acid treatment significantly increased tail moment in FLO...

20. Regulation of hepatic insulin receptor activity following injury - Jiang, Shaoning; Gavrikova, Tatyana A.; Messina, Joseph L.
Impaired insulin receptor (IR) activity has been found in various models of insulin resistance, including models of injury or critical illness and Type 2 diabetes. However, mechanisms that modulate IR function remain unclear. With an animal model of critical-illness diabetes, we found insulin-induced IR tyrosine phosphorylation in the liver was impaired as early as 15 min following trauma and hemorrhage. Possible mechanisms for this defect were examined, including IR protein levels and IR posttranslational modifications. The total amounts of hepatic IRα and IRβ subunits and the membrane localization of the IR were not altered by trauma and hemorrhage, and, likewise,...

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