bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative assessment and characterization of visceral nociception and hyperalgesia in mice
Authors: Kamp Elizabeth H. , Jones R. Carter W. , Tillman Shelly R. , Gebhart G. F.
Published: March 2015

Colorectal distension (CRD) is a well-characterized model of visceral nociception, which we adapted to the mouse. CRD reproducibly evoked contractions of the abdominal musculature [visceromotor response (VMR)], which was graded to stimulus intensity. The magnitude of VMR was greater in male C57BL6 and female 129S6 mice than in male 129S6 and B6.129 mice. In 129S6, C57BL6, and B6.129 mice strains, VMR was reduced dose dependently by morphine (1–10 mg/kg) and by the κ-opioid agonist U-69593 (0.2–2 mg/kg), although U-69593 was significantly less potent in C57BL6 mice. In additional experiments, the VMR was recorded from adult male 129S6 mice before and after intracolonic administration of various irritants. Only 30% ethanol significantly enhanced responses to CRD. The colon hyperalgesia persisted for 14 days and was associated with a significant shift of the morphine dose-response function to the left. We believe this will be a useful model for study of visceral nociception and hyperalgesia, including studies of transgenic mice with mutations relevant to pain.
Substitution of Trp1242of TM17 alters substrate specificity of human multidrug resistance protein 3
Authors: Oleschuk Curtis J. , Deeley Roger G. , Cole Susan P. C.
Published: March 2015

Multidrug resistance protein 3 (MRP3) is an ATP-dependent transporter of 17β-estradiol 17β(d-glucuronide) (E217βG), leukotriene C4(LTC4), methotrexate, and the bile salts taurocholate and glycocholate. In the present study, the role of a highly conserved Trp residue at position 1242 on MRP3 transport function was examined by expressing wild-type MRP3 and Ala-, Cys-, Phe-, Tyr-, and Pro-substituted mutants in human embryonic kidney 293T cells. Four MRP3-Trp1242mutants showed significantly increased E217βG uptake, whereas transport by the Pro mutant was undetectable. Similarly, the Pro mutant did not transport LTC4. By comparison, LTC4transport by the Ala, Cys, Phe, and Tyr mutants was reduced by ∼35%. The Ala, Cys, Phe, and Tyr mutants all showed greatly reduced methotrexate and leucovorin transport, except the Tyr mutant, which transported leucovorin at levels comparable with wild-type MRP3. In contrast, the MRP3-Trp1242substitutions did not significantly affect taurocholate transport or taurocholate and glycocholate inhibition of E217βG uptake. Thus Trp1242substitutions markedly alter the substrate specificity of MRP3 but leave bile salt binding and transport intact.
Increases in biliary cholesterol-to-bile acid ratio in pregnant hamsters fed low and high levels of cholesterol
Authors: Yao Lihang , Dawson Paul A. , Woollett Laura A.
Published: March 2015

Gallstones develop when the secretion of cholesterol is elevated compared with the secretion of bile acids into bile. One of the risk factors for the formation of gallstones is pregnancy. Because the pregnancy-induced increase in hepatic cholesterol synthesis rates could play a critical role in the development of cholesterol stones, the aim of the present study was to determine whether stone formation, as assessed by the ratio of cholesterol to bile acids in bile, could be ablated by blocking the pregnancy-induced increase in hepatic sterol synthesis rates. Golden Syrian hamsters were fed either ground chow or chow supplemented with 0.5% cholesterol for 3 wk and studied in the nonpregnant state or in late gestation. In chow-fed animals, a 1.6-fold increase in the ratio of cholesterol to bile acids occurred simultaneously with a sevenfold increase in hepatic sterol synthesis rate and a ninefold increase in the amount of newly synthesized cholesterol secreted into the bile in late gestation. In the cholesterol-fed dams, an increase in the ratio of cholesterol to bile acids occurred even with the lack of induction of hepatic sterol synthesis rates during pregnancy. Thus it appears that the marked induction of hepatic sterol synthesis rates during gestation is not essential for the pregnancy-induced cholesterol saturation of bile when cholesterol is fed to animals.
Plasminogen directs the pleiotropic effects of uPA in liver injury and repair
Authors: Currier Angela R. , Sabla Gregg , Locaputo Stephanie , Melin-Aldana Hector , Degen Jay L. , Bezerra Jorge A.
Published: March 2015

The urokinase-type plasminogen activator (uPA) plays a central role in liver repair. Nevertheless, the hepatic overexpression of uPA results in panlobular injury and neonatal mortality. Here, we define the molecular mechanisms of liver injury and explore whether uPA can regulate liver repair independently of plasminogen. To address the hypothesis that the liver injury in transgenic mice results from the intracellular activation of plasminogen by transgene-derived uPA (uPAT), we generated mice that overexpress uPAT and lack functional plasminogen (uPAT-Plg−). In these mice, loss of plasminogen abolished the hepatocyte-specific injury and prevented the formation of regenerative nodules displayed by uPAT littermates. Despite the increased expression of hepatic uPA, livers of uPAT-Plg−mice were unable to clear necrotic cells and restore normal lobular organization after an acute injury. Notably, high levels of circulating uPA in uPAT-Plg−mice did not prevent the long-term extrahepatic abnormalities previously associated with plasminogen deficiency. These data demonstrate that plasminogen directs the hepatocyte injury induced by uPAT and mediates the reparative properties of uPA in the liver.
Enteral glutamine stimulates protein synthesis and decreases ubiquitin mRNA level in human gut mucosa
Authors: Coëffier Moïse , Claeyssens Sophie , Hecketsweiler Bernadette , Lavoinne Alain , Ducrotté Philippe , Déchelotte Pierre
Published: March 2015

Effects of glutamine on whole body and intestinal protein synthesis and on intestinal proteolysis were assessed in humans. Two groups of healthy volunteers received in a random order enteral glutamine (0.8 mmol·kg body wt-1·h-1) compared either to saline or isonitrogenous amino acids. Intravenous [2H5]phenylalanine and [13C]leucine were simultaneously infused. After gas chromatography-mass spectrometry analysis, whole body protein turnover was estimated from traced plasma amino acid fluxes and the fractional synthesis rate (FSR) of gut mucosal protein was calculated from protein and intracellular phenylalanine and leucine enrichments in duodenal biopsies. mRNA levels for ubiquitin, cathepsin D, and m-calpain were analyzed in biopsies by RT-PCR. Glutamine significantly increased mucosal protein FSR compared with saline. Glutamine and amino acids had similar effects on FSR. The mRNA level for ubiquitin was significantly decreased after glutamine infusion compared with saline and amino acids, whereas cathepsin D and m-calpain mRNA levels were not affected. Enteral glutamine stimulates mucosal protein synthesis and may attenuate ubiquitin-dependent proteolysis and thus improve protein balance in human gut.
Similarities and differences in the propagation of slow waves and peristaltic waves
Authors: Lammers Wim J. E. P. , Stephen Betty , Slack John R.
Published: March 2015

The relationship between slow waves and peristaltic reflexes has not been well analyzed. In this study, we have recorded the electrical activity of slow waves together with that generated by spontaneous peristaltic contractions at 240 extracellular sites simultaneously. Recordings were made from five isolated tubular and six sheet segments of feline duodenum superfused in vitro. In all preparations, slow waves propagated as broad wave fronts along the longitudinal axis of the preparation in either the aborad or the orad direction. Electrical potentials recorded during peristalsis (peristaltic waves) also propagated as broad wave fronts in either directions. Peristaltic waves often spontaneously stopped conducting (46%), in contrast to slow waves that never did. Peristaltic waves propagated at a lower velocity than the slow waves (0.98 ± 0.25 and 1.29 ± 0.28 cm/s, respectively; P < 0.001; n = 24) and in a direction independent of the preceding slow wave direction (64% in the same direction, 46% in the opposite direction). In conclusion, slow waves and peristaltic waves in the isolated feline duodenum seem to constitute two separate electrical events that may drive two different mechanisms of contraction in the small intestine.
Regulation of apo A-IV transcription by lipid in newborn swine is associated with a promoter DNA-binding protein
Authors: Lu Song , Yao Ying , Wang Heng , Meng Songmei , Cheng Xiangying , Black Dennis D.
Published: March 2015

Dietary lipid acutely upregulates apolipoprotein (apo) A-IV expression by sevenfold at the pretranslational level in neonatal swine jejunum. To determine the mechanism of this regulation, two-day-old female swine received intraduodenal infusions of low- and high-triacylglycerol (TG) isocaloric diets for 24 h. Nuclear runoff assay confirmed apo A-IV gene transcriptional regulation by the high-TG diet. Footprinting analysis using the swine apo A-IV proximal promoter sequence (+14 to −246 bp) demonstrated three regions protected by the low-TG extracts. Of these three motifs, only ACCTTC showed 100% homology to the human sequence and was further studied. EMSA was performed using probes containing wild-type (WT) and mutant (M) motifs. A shift was noted with the low-TG nuclear extracts with the WT probe but not with the M probe. Excess unlabeled free WT probe competed out the shift, whereas the M probe did not. No significant shift occurred with either probe using high-TG extracts. These results suggest that a repressor protein binds to the ACCTTC motif and becomes unbound during lipid absorption, allowing transcriptional activation of the apo A-IV gene in newborn swine small intestine.
Regulation of acid secretion and paracellular permeability by F-actin in the bullfrog,Rana catesbeiana
Authors: Abdul-Ghaffar Al-Shaibani Tarik A. , Hagen Susan J.
Published: March 2015

G526, 2002. First published December 5, 2001; 10.1152/ajpgi.00393. 2001.—Many studies have implicated F-actin in the regulation of gastric acid secretion using cytochalasin D (CD) to disrupt apical actin filaments in oxyntic cells. However, it is known that CD also affects mucosal permeability by disrupting tight junction structure. Here we investigated the contribution of F-actin to mucosal permeability and acid secretion in the stomach using CD. Stomachs were mounted in Ussing chambers and acid secretion (stimulated or inhibited), transepithelial resistance (TER), mannitol flux, bicarbonate transport, and dual mannitol/sodium fluxes were determined with or without CD. H+back diffusion was predicted from its diffusion coefficient. Incubation with CD resulted in a significant reduction in stimulated acid secretion. TER was unchanged in stimulated tissues but significantly reduced in inhibited tissues. Mannitol flux, bicarbonate transport, and H+-back diffusion increased significantly with CD. However, the rates of bicarbonate and H+flux were not large enough to account for the inhibition of acid secretion. These findings demonstrate that actin filaments regulate paracellular permeability and play an essential role in the regulation of acid secretion in the stomach.
I. Hepatocyte transport of bile acids
Authors: Wolkoff Allan W. , Cohen David E.
Published: March 2015

Bile acids are cholesterol derivatives that serve as detergents in bile and the small intestine. Approximately 95% of bile acids secreted by hepatocytes into bile are absorbed from the distal ileum into the portal venous system. Extraction from the portal circulation by the hepatocyte followed by reexcretion into the bile canaliculus completes the enterohepatic circulation of these compounds. Over the past few years, candidate bile acid transport proteins of the sinusoidal and canalicular plasma membranes of the hepatocyte have been identified. The physiology of hepatocyte bile acid transport and its relationship to these transport proteins is the subject of this Themes article.
cAMP inhibits bile acid-induced apoptosis by blocking caspase activation and cytochromecrelease
Authors: Webster Cynthia R. L. , Usechak Paul , Anwer M. Sawkat
Published: March 2015

We have previously shown that cAMP protects against bile acid-induced apoptosis in cultured rat hepatocytes in a phosphoinositide 3-kinase (PI3K)-dependent manner. In the present studies, we investigated the mechanisms involved in this anti-apoptotic effect. Hepatocyte apoptosis induced by glycodeoxycholate (GCDC) was associated with mitochondrial depolarization, activation of caspases, the release of cytochrome c from the mitochondria, and translocation of BAX from the cytosol to the mitochondria. cAMP inhibited GCDC-induced apoptosis, caspase 3 and caspase 9 activation, and cytochrome c release in a PI3K-dependent manner. cAMP activated PI3K in p85 immunoprecipitates and resulted in PI3K-dependent activation of the survival kinase Akt. Chemical inhibition of Akt phosphorylation with SB-203580 partially blocked the protective effect of cAMP. cAMP resulted in wortmannin-independent phosphorylation of BAD and was associated with translocation of BAD from the mitochondria to the cytosol. These results suggest that GCDC-induced apoptosis in cultured rat hepatocytes proceeds through a caspase-dependent intracellular stress pathway and that the survival effect of cAMP is mediated in part by PI3K-dependent Akt activation at the level of the mitochondria.
Multipotential stem cells in adult mouse gastric epithelium
Authors: Bjerknes Matthew , Cheng Hazel
Published: March 2015

Previous studies of chimeric animals demonstrate that multipotential stem cells play a role in the development of the gastric epithelium; however, despite much effort, it is not clear whether they persist into adulthood. Here, chemical mutagenesis was used to label random epithelial cells by loss of transgene function in adult hemizygous ROSA26 mice, a mouse strain expressing the transgene lacZ in all tissues. Many clones derived from such cells contained all the major epithelial cell types, thereby demonstrating existence of functional multipotential stem cells in adult mouse gastric epithelium. We also observed clones containing only a single mature cell type, indicating the presence of long-lived committed progenitors in the gastric epithelium. Similar results were obtained in duodenum and colon, showing that this mouse model is suitable for lineage tracing in all regions of the gastrointestinal tract and likely useful for cell lineage studies in other adult renewing tissues.
Immunolocalization of electroneutral Na+-HCO 3 − cotransporters in human and rat salivary glands
Authors: Gresz V. , Kwon T.-H. , Vorum H. , Zelles T. , Kurtz I. , Steward M. C. , Aalkjaer C. , Nielsen S.
Published: March 2015

Patterns of salivary HCO[Formula: see text]secretion vary widely among species and among individual glands. In particular, virtually nothing is known about the molecular identity of the HCO[Formula: see text] transporters involved in human salivary secretion. We have therefore examined the distribution of several known members of the Na+-HCO[Formula: see text] cotransporter (NBC) family in the parotid and submandibular glands. By use of a combination of RT-PCR and immunoblotting analyses, the electroneutral cotransporters NBC3 and NBCn1 mRNA and protein expression were detected in both human and rat tissues. Immunohistochemistry demonstrated that NBC3 was present at the apical membranes of acinar and duct cells in both human and rat parotid and submandibular glands. NBCn1 was strongly expressed at the basolateral membrane of striated duct cells but not in the acinar cells in the human salivary glands, whereas little or no NBCn1 labeling was observed in the rat salivary glands. The presence of NBCn1 at the basolateral membrane of human striated duct cells suggests that it may contribute to ductal HCO[Formula: see text] secretion. In contrast, the expression of NBC3 at the apical membranes of acinar and duct cells in both human and rat salivary glands indicates a possible role of this isoform in HCO[Formula: see text] salvage under resting conditions.
PKC-ϵ translocation in enteric neurons and interstitial cells of Cajal in response to muscarinic stimulation
Authors: Wang Xuan-Yu , Ward Sean M. , Gerthoffer William T. , Sanders Kenton M.
Published: March 2015

Interstitial cells of Cajal in the deep muscular plexus (ICC-DMP) of the small intestine express excitatory neurotransmitter receptors. We tested whether ICC-DMP are functionally innervated by cholinergic neurons in the murine intestine. Muscles were stimulated by intrinsic nerves and ACh and processed for immunohistochemistry to determine these effects on PKC-ϵ activation. Under control conditions, PKC-ϵ-like immunoreactivy (PKC-ϵ-LI) was only observed in myenteric neurons within the tunica muscularis. Electrical field stimulation or ACh caused translocation of neural PKC-ϵ-LI from the cytosol to a peripheral compartment. After stimulation, PKC-ϵ-LI was found in spindle-shaped cells in the DMP. These cells were identified as ICC-DMP by Kit-LI and vimentin-LI. PKC-ϵ-LI in ICC-DMP and translocation of PKCϵ-LI in neurons were blocked by tetrodotoxin or atropine, suggesting that these responses were due to activation of muscarinic receptors. Western blots also confirmed translocation of PKC-ϵ-LI. In conclusion, PKC-ϵ translocation is linked to muscarinic receptor activation in ICC-DMP and a subpopulation of myenteric neurons. These studies demonstrate that ICC-DMP are functionally innervated by excitatory motoneurons.
Secretin regulates paracellular permeability in canine gastric monolayers by a Src kinase-dependent pathway
Authors: Chen Monica C. , Solomon Travis E. , Salazar Eduardo Perez , Kui Robert , Rozengurt Enrique , Soll Andrew H.
Published: March 2015

Previous studies found that epidermal growth factor (EGF) decreased paracellular permeability in gastric mucosa, but the other physiological regulators and the molecular mechanisms mediating these responses remain undefined. We investigated the role of secretin and Src in regulating paracellular permeability because secretin regulates gastric chief cell function and Src mediates events involving the cytoskeletal-membrane interface, respectively. Confluent monolayers were formed from canine gastric epithelial cells in short-term culture on Transwell filter inserts. Resistance was monitored in the presence of secretin with or without specific kinase inhibitors. Tyrosine phosphorylation of Src at Tyr416 was measured with a site-specific phosphotyrosine antibody. Basolateral, but not apical, secretin at concentrations from 1 to 100 nM dose dependently increased resistance; this response was rapid and sustained over hours. PP2 (10 μM), a selective Src tyrosine kinase inhibitor, but not the inactive isomer PP3, abolished the increase in resistance by secretin but only modestly attenuated apical EGF effects. AG-1478 (100 nM), a specific EGF receptor tyrosine kinase inhibitor, attenuated the resistance increase to EGF but not secretin. Secretin, but not EGF, induced tyrosine phosphorylation of Src at Tyr416 in a dose-dependent fashion, with the maximal response observed at 1 min. PP2, but not PP3, dramatically inhibited this tyrosine phosphorylation. Secretin increases paracellular resistance in gastric mucosa through a Src-mediated pathway, while the effect of EGF is Src independent. Src appears to mediate the physiological effects of this Gs-coupled receptor in primary epithelial cells.
Effects of NF-κB inhibition on mesenteric ischemia-reperfusion injury
Authors: Zou Lei , Attuwaybi Bashir , Kone Bruce C.
Published: March 2015

Mesenteric ischemia-reperfusion injury is a serious complication of shock. Because activation of nuclear factor-κB (NF-κB) has been implicated in this process, we treated rats with vehicle or the IκB-α inhibitor BAY 11-7085 (25 mg/kg ip) 1 h before mesenteric ischemia-reperfusion (45 min of ischemia followed by reperfusion at 30 min or 6 h) and examined the ileal injury response. Vehicle-treated rats subjected to ischemia-reperfusion exhibited severe mucosal injury, increased myeloperoxidase (MPO) activity, increased expression of interleukin-6 and intercellular adhesion molecule 1 protein, and a biphasic peak of NF-κB DNA-binding activity during the 30-min and 6-h reperfusion courses. In contrast, BAY 11-7085-pretreated rats subjected to ischemia-reperfusion exhibited less histological injury and less interleukin-6 and intercellular adhesion molecule 1 protein expression at 30 min of reperfusion but more histological injury at 6 h of reperfusion than vehicle-treated rats subjected to ischemia-reperfusion. Studies with phosphorylation site-specific antibodies demonstrated that IκB-α phosphorylation at Ser32,Ser36 was induced at 30 min of reperfusion, whereas tyrosine phosphorylation of IκB-α was induced at 6 h of reperfusion. BAY 11-7085 inhibited the former, but not the latter, phosphorylation pathway, whereas α-melanocyte-stimulating hormone, which is effective in limiting late ischemia-reperfusion injury to the intestine, inhibited tyrosine phosphorylation of IκB-α. Thus NF-κB appears to play an important role in the generation and resolution of intestinal ischemia-reperfusion injury through different activation pathways.
Inducible nitric oxide synthase is involved in acid-induced gastric hyperemia in rats and mice
Authors: Phillipson Mia , Henriksnäs Johanna , Holstad Maria , Sandler Stellan , Holm Lena
Published: March 2015

The role of different isoforms of nitric oxide synthase (NOS) in the gastric mucosal hyperemia, induced by 155 mM luminal hydrochloric acid (pH ≈ 0.8) without a barrier breaker, was investigated. Rats were anesthetized with Inactin (120 mg/kg ip), and mice were anesthetized with Forene (2.2% in 40% oxygen gas at 150 ml/min); the gastric mucosa was exteriorized. Gastric mucosal blood flow was measured with laser-Doppler flowmetry (LDF) in rats treated with Nω-nitro-l-arginine (l-NNA; unspecific NOS inhibitor), l- N6-(1-iminoethyl)lysine [l-NIL; inducible (i) NOS inhibitor], or S-methyl-l-thiocitrulline [SMTC; neuronal (n) NOS inhibitor], 10 mg/kg, followed by 3 mg · kg–1· h–1iv, in iNOS-deficient (–/–) and nNOS(–/–) mice. mRNA was isolated from the gastric mucosa in iNOS(–/–) and wild-type (wt) mice, and real-time RT-PCR was performed. The effect of 155 mM acid on gastric mucosal permeability was determined by measuring the clearance of51Cr-EDTA from blood to lumen. LDF increased by 48 ± 13% during 155 mM HCl luminally, an increase that was abolished by l-NNA, SMTC, or l-NIL. In iNOS wt mice, LDF increased by 33 ± 8% during luminal acid. The blood flow increase was attenuated substantially in iNOS(–/–) mice. RT-PCR revealed iNOS mRNA expression in the gastric mucosa in the iNOS wt groups. The blood flow increase in response to acid was not abolished in nNOS(–/–) mice (nNOS-sufficient mice, 39 ± 18%; heterozygous mice, 25 ± 19%; –/– mice, 19 ± 7%). Mucosal permeability was transiently increased during 155 mM HCl. The results suggest that iNOS is constitutively expressed in the gastric mucosa and is involved in acid-induced hyperemia, suggesting a novel role for iNOS in gastric mucosal protection.
A novel mitogenic protein that is highly expressed in cells of the gastric antrum mucosa
Authors: Martin Terence E. , Powell C. Thomas , Wang Zunde , Bhattacharyya Somnath , Walsh-Reitz Margaret M. , Agarwal Kan , Toback F. Gary
Published: March 2015

Human and pig cDNAs for a novel stomach protein, the product of a gene expressed at high levels specifically in cells of the antrum mucosa, have been characterized. The general exon/intron structure of the genomic DNA is conserved in humans and mice. The predicted protein sequences of the human and mouse mRNAs contain 185 and 184 amino acids, respectively. The protein isolated from pig antral extracts has an NH2 terminus consistent with cleavage of a 20-amino acid signal peptide. Human cDNA was expressed in E. coli to generate a protein antigen for antibody production. The antibodies detected polypeptides of ∼18 kDa in antrum extracts from all mammalian species tested. Immunocytochemistry located antrum mucosal protein (AMP)-18 to surface mucosal cells of the mouse antrum and, specifically, to secretion granules, suggesting that it is cosecreted with mucins. Antrum extracts and recombinant human AMP-18 exhibit growth-promoting activity on epithelial cells that can be blocked by the specific antisera. We suggest that AMP-18 is a “gastrokine” that maintains the integrity of the gastric mucosal epithelium.
Effect of heat shock preconditioning on NF-κB/I-κB pathway during I/R injury of the rat liver
Authors: Uchinami Hiroshi , Yamamoto Yuzo , Kume Makoto , Yonezawa Kei , Ishikawa Yasuhide , Taura Kojiro , Nakajima Akio , Hata Koichiro , Yamaoka Yoshio
Published: March 2015

Hepatic ischemia-reperfusion (I/R) injury continues to be a fatal complication after liver surgery. Heat shock (HS) preconditioning is an effective strategy for protecting the liver from I/R injury, but its exact mechanism is still unclear. Because the activation of nuclear factor-κB (NF-κB) is an important event in the hepatic I/R-induced inflammatory response, the effect of HS preconditioning on the pathway for NF-κB activation was investigated. In the control group, NF-κB was activated 60 min after reperfusion, but this activation was suppressed in the HS group. Messenger RNA expressions of proinflammatory mediators during reperfusion were also reduced with HS preconditioning. Concomitant with NF-κB activation, NF-κB inhibitor I-κB proteins were degraded in the control group, but this degradation was suppressed in the HS group. This study shows that HS preconditioning protected the liver from I/R injury by suppressing the activation of NF-κB and the subsequent expression of proinflammatory mediators through the stabilization of I-κB proteins.
Rat enterocytes secrete SLPs containing alkaline phosphatase and cubilin in response to corn oil feeding
Authors: Mahmood Akhtar , Shao Jian-su , Alpers David H.
Published: March 2015

Surfactant-like particles (SLP) are unilamellar secreted membranes associated with the process of lipid absorption and isolated previously only from the apical surface of enterocytes. In this paper, the intracellular membrane has been isolated from corn oil-fed animals, identified by its content of the marker protein intestinal alkaline phosphatase (IAP). Another brush-border protein, cubilin, and its anchoring protein megalin have been identified as components of extracellular SLP, but only cubilin is present to any extent in intracellular SLP. During fat absorption, IAP is modestly enriched in intracellular SLP, but full-length cubilin (migrating at 210 kDa in fat-fed mucosal fractions) falls by one-half, although fragments of cubilin are abundant in the intracellular SLP. Both IAP and cubilin colocalize to the same cells during corn oil absorption and colocalize around lipid droplets. This localization is more intense during feeding of corn oil with Pluronic L-81, a detergent that allows uptake of fatty acids and monoglycerides from the lumen, but blocks chylomicron secretion. Confocal microscopy confirms the colocalization of IAP and the ligand for cubilin, intrinsic factor. Possible roles for cubilin in intracellular SLP include facilitating movement of the lipid droplet through the cell and binding to the basolateral membrane before reverse endocytosis.
III. Regulation of bile acid synthesis: past progress and future challenges
Authors: Fuchs Michael
Published: March 2015

Bile acids, amphipathic detergent-like molecules synthesized from cholesterol, are highly conserved by means of enterohepatic circulation. They participate in the generation of bile flow and biliary lipid secretion and also promote absorption of fat-soluble vitamins and lipids. Conversion of cholesterol to bile acids represents a quantitatively important route to eliminate cholesterol from the body. Regulation of bile acid synthesis involves a complex and interrelated group of transcription regulators that link bile acid synthesis to cholesterol and fatty acid metabolism. Targeting key steps of bile acid synthetic pathways as well as the metabolic network that maintains homeostatic levels of lipids should provide exciting novel opportunities for the treatment of cardiovascular and liver diseases.
Activation of peroxisome proliferator-activated receptor-γ contributes to the inhibitory effects of curcumin on rat hepatic stellate cell growth
Authors: Xu Jianye , Fu Yumei , Chen Anping
Published: March 2015

Hepatic fibrogenesis occurs as a wound-healing process after many forms of chronic liver injury. Hepatic fibrosis ultimately leads to cirrhosis if not treated effectively. During liver injury, quiescent hepatic stellate cells (HSC), the most relevant cell type, become active and proliferative. Oxidative stress is a major and critical factor for HSC activation. Activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) inhibits the proliferation of nonadipocytes. The level of PPAR-γ is dramatically diminished along with activation of HSC. Curcumin, the yellow pigment in curry, is a potent antioxidant. The aims of this study were to evaluate the effect of curcumin on HSC proliferation and to begin elucidating underlying mechanisms. It was hypothesized that curcumin might inhibit the proliferation of activated HSC by inducing PPAR-γ gene expression and reviving PPAR-γ activation. Our results indicated that curcumin significantly inhibited the proliferation of activated HSC and induced apoptosis in vitro. We demonstrated, for the first time, that curcumin dramatically induced the gene expression of PPAR-γ and activated PPAR-γ in activated HSC. Blocking its trans-activating activity by a PPAR-γ antagonist markedly abrogated the effects of curcumin on inhibition of cell proliferation. Our results provide a novel insight into mechanisms underlying the inhibition of activated HSC growth by curcumin. The characteristics of curcumin, including antioxidant potential, reduction of activated HSC growth, and no adverse health effects, make it a potential antifibrotic candidate for prevention and treatment of hepatic fibrosis.
The effect of gastric electrical stimulation on canine gastric slow waves
Authors: Xing Jinhong , Brody Frederick , Rosen Michael , Chen J. D. Z. , Soffer Edy
Published: March 2015

This study determined the most efficient parameters of low-frequency/long-pulse gastric electrical stimulation (GES) required to entrain gastric slow waves and also evaluated the effect of entrainment and high-frequency, short-pulse GES on gastric electrical activity (GEA). Nine dogs were fitted with stimulation wires along the greater curvature. Entrainment was observed in six or seven animals, with long-pulse GES at six cycles per minute (cpm), at various combinations of current and pulse width and was directly related to the energy delivered. Entrainment was observed in four to seven animals, with GES at 12 cpm, and the maximal driven frequency was 6 cpm. Entrainment did not significantly increase the dominant power of GEA. High-frequency, short-pulse GES, using pulse trains of 14 Hz, 5 mA, and 330 μs, with 0.1 s on and 5 s off, and pulse trains of 40 Hz, 10 mA, and 330 μs, with 2 s on 3 s off, did not affect variables of GEA. We conclude that acute low-frequency GES but not high-frequency, short-pulse GES can entrain slow waves; the power of slow waves is not affected by either type of stimulation.
IV. Current concepts of vagal efferent projections to the gut
Authors: Chang Howard Y. , Mashimo Hiroshi , Goyal Raj K.
Published: March 2015

Vagal efferents, consisting of distinct lower motor and preganglionic parasympathetic fibers, constitute the motor limb of vagally mediated reflexes. Arising from the nucleus ambiguus, vagal lower motor neurons (LMN) mediate reflexes involving striated muscles of the orad gut. LMNs provide cholinergic innervation to motor end plates that are inhibited by myenteric nitrergic neurons. Preganglionic neurons from the dorsal motor nucleus implement parasympathetic motor and secretory functions. Cholinergic preganglionic neurons form parallel inhibitory and excitatory vagal pathways to smooth muscle viscera and stimulate postganglionic neurons via nicotinic and muscarinic receptors. In turn, the postganglionic inhibitory neurons release ATP, VIP, and NO, whereas the excitatory neurons release ACh and substance P. Vagal motor effects are dependent on the viscera's intrinsic motor activity and the interaction between the inhibitory and excitatory vagal influences. These interactions help to explain the physiology of esophageal peristalsis, gastric motility, lower esophageal sphincter, and pyloric sphincter. Vagal secretory pathways are predominantly excitatory and involve ACh and VIP as the postganglionic excitatory neurotransmitters. Vagal effects on secretory functions are exerted either directly or via release of local mediators or circulating hormones.
IV. Bile acids and death receptors
Authors: Higuchi Hajime , Gores Gregory J.
Published: March 2015

Toxic bile acids facilitate Fas and tumor necrosis factor-associated apoptosis-inducing ligand (TRAIL) death-receptor oligomerization and activation. Bile acid modulation of death-receptor signaling is multifactorial and includes trafficking of Fas to the cell surface, enhancing TRAIL-R2/DR5 expression, and suppression of function of cFLIP, an antiapoptotic protein modulating death-receptor function. Because bile acid-associated death receptor-mediated apoptosis is a common mechanism for cholestatic hepatocyte injury, inhibition of death receptors and their cascades may prove useful in attenuating liver injury during cholestasis.
Distinct epithelial responses in experimental colitis: implications for ion uptake and mucosal protection
Authors: Renes Ingrid B. , Verburg Melissa , Van Nispen Daniëlle J. P. M. , Büller Hans A. , Dekker Jan , Einerhand Alexandra W. C.
Published: March 2015

In the present study, we aimed to investigate enterocyte- and goblet cell-specific functions during the different phases of acute colitis induced with dextran sulfate sodium (DSS). Rats were treated with DSS for 7 days, followed by a 7-day recovery period. Colonic tissue was excised on days 2 (onset of disease), 7 (active disease), and 14(regenerative phase). Enterocyte functions were studied by the expression of carbonic anhydrases (CAs), sodium/hydrogen exchangers (NHEs) and intestinal fatty acid-binding protein (iFABP) and by alkaline phosphatase (AP) activity. The expression and secretion of the mucin Muc2 and trefoil factor family peptide-3 (TFF3) were used as parameters for goblet cell function. DSS induced a downregulation of the CAs, NHEs, and iFABP in some normal-appearing surface enterocytes and in most of the flattened-surface enterocytes during disease onset and active disease. During the regenerative phase most enterocytes expressed these genes again. Quantitative analysis revealed a significant decrease in CAs, NHEs, and iFABP expression levels during onset and active disease. During the regenerative phase, the expression levels of the CAs were restored, whereas the expression levels of the NHEs and iFABP remained decreased. In contrast, enterocyte-specific AP activity was maintained in normal and flattened enterocytes during DSS-induced colitis. Goblet cells continued to express MUC2 and TFF3 during and after DSS treatment. Moreover, Muc2 and TFF3 expression and secretion levels were maintained or even increased during each of the DSS-induced disease phases. In conclusion, DSS-induced colitis was associated with decreased expression of CAs, NHEs, and iFABP. The loss of these genes possibly accounts for some of the pathology seen in colitis. The maintenance or upregulation of Muc2 and TFF3 synthesis and secretion levels implies that goblet cells at least maintain their epithelial defense and repair capacity during acute inflammation induced by DSS.
Gastrin-induced gastric adenocarcinoma growth is mediated through cyclin D1
Authors: Song Diane H. , Rana Basabi , Wolfe Jessica R. , Crimmins Geoffrey , Choi Caroline , Albanese Chris , Wang Timothy C. , Pestell Richard G. , Wolfe M. Michael
Published: March 2015

Gastrin is a gastrointestinal (GI) peptide that possesses potent trophic effects on most of the normal and neoplastic mucosa of the GI tract. Despite abundant evidence for these properties, the mechanisms governing gastrin-induced proliferation are still largely unknown. To elucidate the mechanisms by which gastrin might influence mitogenesis in gastric adenocarcinoma, we analyzed its effects on the human cell line AGS-B. Amidated gastrin (G-17), one of the major circulating forms of gastrin, induced a concentration-dependent increase in [3H]thymidine incorporation of cells in culture, with the maximum effective concentration occurring with 20 nM G-17. This effect was significantly attenuated by the gastrin-specific receptor antagonist L-365260. In addition, we found that G-17 induced a significant increase in the levels of cyclin D1 transcripts, protein, and promoter activity. The results of these studies indicate that gastrin appears to exert its mitogenic effects on gastric adenocarcinoma, at least in part, through changes in cyclin D1 expression.
Transforming growth factor-β1 signaling contributes to Caco-2 cell growth inhibition induced by 1,25(OH)2D3
Authors: Chen Anping , Davis Bernard H. , Sitrin Michael D. , Brasitus Thomas A. , Bissonnette Marc
Published: March 2015

Growth of Caco-2 and many cancer cells is inhibited by 1,25(OH)2D3. Whereas TGF-β1 inhibits normal colonic epithelial cell growth, most human colon cancer-derived cells, including Caco-2 and SW480 cells, are resistant to it. The mechanisms underlying these antiproliferative actions and resistance to TGF-β growth inhibition are largely unknown. We observed that 1,25-dihydroxyvitamin D3[1,25(OH)2D3] sensitized Caco-2 and SW480 cells to TGF-β1 growth inhibitory effects. Versus 1,25(OH)2D3alone, the combination of 1,25(OH)2D3and TGF-β1 significantly reduced cell numbers. Also, the amount of active TGF-β1 was increased (∼4-fold) by this secosteroid in conditioned media from Caco-2 cells. The 1,25(OH)2D3increased the expression of IGF-II receptors (IGF-IIR), which facilitated activation of latent TGF-β1, and was found to activate TGF-β signaling in Caco-2 cells. By using neutralizing antibodies to human TGF-β1, we showed that this cytokine contributes to secosteroid-induced inhibition of Caco-2 cell growth. Also, 1,25(OH)2D3was found to enhance the type I TGF-β receptor mRNA and protein abundance in Caco-2 cells. Whereas the 1,25(OH)2D3-induced sensitization of Caco-2 cells to TGF-β1 was IGF-IIR independent, the type I TGF-β1 receptor was required for this sensitization. Thus 1,25(OH)2D3treatment of Caco-2 cells results in activation of latent TGF-β1, facilitated by the enhanced expression of IGF-IIR by this secosteroid. Also, 1,25(OH)2D3sensitized Caco-2 cells to growth inhibitory effects of TGF-β1, contributing to the inhibition of Caco-2 cell growth by this secosteroid.
Ca2+- and PKC-dependent stimulation of PGE2synthesis by deoxycholic acid in human colonic fibroblasts
Authors: Zhu Yingting , Hua Ping , Rafiq Shazia , Waffner Eric J. , Duffey Michael E. , Lance Peter
Published: March 2015

We investigated prostanoid biogenesis by human colonic fibroblasts (CCD-18Co cells and nine primary fibroblast cultures) exposed to a primary (cholic, CA) or a secondary (deoxycholic, DCA) bile acid. Basal PGE2levels in CCD-18Co cultures and fibroblast strains initiated from normal and adenocarcinomatous colon, respectively, were 1.7 ± 0.3, 4.0 ± 2.0, and 15.0 ± 4.8 ng/mg protein. Peak levels 24 h after exposure to DCA (300 μM) rose, respectively, seven-, six- and sevenfold, but CA elicited no such responses. Increases in PGE2synthesis were preceded by sequential increases in PGH synthase-2 mRNA and protein expression and were fully prevented by a nonselective (indomethacin) or a selective (celecoxib) nonsteroidal anti-inflammatory drug. DCA, but not CA, caused abrupt, transient increases in fibroblast intracellular Ca2+concentration ([Ca2+]i) ∼1 min after exposure. Increased [Ca2+]iwas required for DCA-mediated induction of PGE2synthesis, and protein kinase C was a further essential component of this signaling pathway. Colonic fibroblasts may be a major target for prostanoid biogenesis induced by fecal bile acids and, potentially, other noxious actions of these agents.
Gastritis increases resistance to aspirin-induced mucosal injury via COX-2-mediated lipoxin synthesis
Authors: Souza Marcellus H. L. P. , de Lima Octavio Menezes , Zamuner Stella R. , Fiorucci Stefano , Wallace John L.
Published: March 2015

Products of cyclooxygenase (COX)-2 contribute to mucosal defense. Acetylation of COX-2 by aspirin has been shown to result in the generation of 15(R)-epi-lipoxin A4, which exerts protective effects in the stomach. In gastritis, it is possible that lipoxin A4 makes a greater contribution to mucosal defense. We tested this hypothesis in the rat, by using the iodoacetamide-induced gastritis model. Iodoacetamide was added to the drinking water for 5 days. Rats were then given aspirin, and the extent of gastric damage was blindly assessed 3 h later. Gastric 15(R)-epi-lipoxin A4 and PGE2 levels were determined. The effects of pretreatment with a selective COX-2 inhibitor, rofecoxib, and of a lipoxin receptor antagonist were assessed. Effects of aspirin and the other test drugs on leukocyte adherence within mesenteric venules were assessed by intravital microscopy. Aspirin elicited greater lipoxin synthesis in the inflamed than in the normal stomach, and there was reduced gastric damage. Rofecoxib inhibited lipoxin synthesis and exacerbated aspirin-induced damage. The lipoxin antagonist also exacerbated aspirin-induced damage. In rats with gastritis, aspirin reduced leukocyte adherence (in contrast to an increase in normal rats), and this effect was reversed by rofecoxib or by the lipoxin antagonist. These results support the notion that aspirin-triggered lipoxin synthesis via COX-2 makes an important contribution to mucosal defense in both the normal and inflamed stomach.
Effect of prolonged gastric distension on motor function of LES and of proximal stomach
Authors: Allocca M. , Mangano M. , Penagini R.
Published: March 2015

Gastric distension is a potent stimulus of transient lower esophageal sphincter (LES) relaxation. To investigate the time effect of prolonged gastric distension on the rate of transient LES relaxations, LES pressure, and the motor and sensory functions of the proximal stomach, we performed a continuous isobaric distension of the proximal stomach at the 75% threshold pressure for discomfort for 2 h in seven healthy subjects. A multilumen assembly incorporating a sleeve and an electronic barostat was used. The rate of transient LES relaxations ( n/30 min) was constant during the first hour [4.1 ± 1.2 (0–30 min) and 5.4 ± 1.1 (30–60 min)] but markedly decreased ( P < 0.05) in the second hour [2.1 ± 0.5 (60–90 min) and 2.3 ± 0.9 (90–120 min)], whereas LES pressure, baseline volume and volume waves within the gastric bag, hunger, and fullness did not change throughout the experiment. It is concluded that the rate of transient LES relaxations decreases with time during prolonged gastric distension, thus suggesting that this type of stimulus should not be used in sequential experimental conditions.
Region-specific adaptation of apical Na/H exchangers after extensive proximal small bowel resection
Authors: Musch Mark W. , Bookstein Cres , Rocha Flavio , Lucioni Alvaro , Ren Hongyu , Daniel Janet , Xie Yue , McSwine Rebecca L. , Rao Mrinalini C. , Alverdy John , Chang Eugene B.
Published: March 2015

After massive small bowel resection (MSBR), the remnant small intestine adapts to restore Na absorptive function. The possibility that this occurs through increases in cellular Na absorptive capacity was examined by assessing the regional effects of 50% proximal MSBR on the function and expression of the apical membrane Na/H exchangers (NHEs) NHE2 and NHE3. Morphometric analysis confirmed adaptive changes consistent with villus hypertrophy, particularly distal to the anastomosis. Villus epithelium prepared by light mucosal scrapings from 2-wk-postresected and -posttransected control rats exhibited comparable brush-border hydrolase activities, total cell protein per DNA, and villin expression but increased basolateral Na-K-ATPase activity. Parallel increases of two- to threefold in protein and mRNA abundance of NHE2 and NHE3 were observed only in ileal regions distal to the anastomosis of resected rats. Basolateral NHE1 expression was unchanged. After 80% resection, increases in NHE2 and NHE3 became evident in proximal colon. We conclude that increased enterocyte expression and function of apical membrane NHEs in regions distal to the anastomosis play a role in the adaptive process after MSBR. The increased luminal Na load to distal bowel regions after proximal resection may stimulate increases in apical membrane NHE gene transcription and protein expression.
Region-specific ontogeny of α-2,6-sialyltransferase during normal and cortisone-induced maturation in mouse intestine
Authors: Dai Dingwei , Nanthakumar N. Nanda , Savidge Tor C. , Newburg David S. , Walker W. Allan
Published: March 2015

Regional differences in the ontogeny of mouse intestinal α-2,6-sialyltransferase activities (α-2,6-ST) and the influence of cortisone acetate (CA) on this expression were determined. High ST activity and α-2,6-ST mRNA levels were detected in immature small and large intestine, with activity increasing distally from the duodenum. As the mice matured, ST activity (predominantly α-2,6-ST) in the small intestine decreased rapidly to adult levels by the fourth postnatal week. CA precociously accelerated this region-specific ontogenic decline. A similar decline of ST mRNA levels reflected ST activity in the small, but not the large, intestine. Small intestinal sialyl α-2,6-linked glycoconjugates displayed similar developmental and CA induced-precocious declines when probed using Sambucus nigraagglutinin (SNA) lectin. SNA labeling demonstrated age-dependent diminished sialyl α2,6 glycoconjugate expression in goblet cells in the small (but not large) intestine, but no such regional specificity was apparent in microvillus membrane. This suggests differential regulation of sialyl α-2,6 glycoconjugates in absorptive vs. globlet cells. These age-dependent and region-specific differences in sialyl α-2,6 glycoconjugates may be mediated in part by altered α-2,6-ST gene expression regulated by trophic factors such as glucocorticoids.
II. Intestinal corticosteroid receptors
Authors: Sheppard Karen E.
Published: March 2015

Two corticosteroid receptors have been cloned; they are the glucocorticoid receptor and the mineralocorticoid receptor. These receptors are members of the steroid/thyroid/retinoid receptor family of nuclear transactivating factors, which are characterized by two highly conserved zinc fingers in the central DNA binding domain, a COOH-terminal domain that encompasses the ligand binding site, and a variable NH2-terminal domain. In addition to these cloned receptors, other corticosteroid receptors have recently been identified in intestine. Steroid binding studies have identified two novel putative corticosteroid receptors in intestinal epithelia, and molecular cloning studies have detected two low-affinity receptors in small intestine that are activated by corticosteroids and induce CYP3A gene expression. This article focuses on the identification of these novel corticosteroid receptors and the potential role they may play in intestinal physiology.