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PubMed Central (PMC3 - NLM DTD) (2,750,487 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 121 - 140 de 822

121. Capsaicin induces NKCC1 internalization and inhibits chloride secretion in colonic epithelial cells independently of TRPV1 - Bouyer, Patrice G.; Tang, Xu; Weber, Christopher R.; Shen, Le; Turner, Jerrold R.; Matthews, Jeffrey B.
Colonic chloride secretion is regulated via the neurohormonal and immune systems. Exogenous chemicals (e.g., butyrate, propionate) can affect chloride secretion. Capsaicin, the pungent ingredient of the chili peppers, exerts various effects on gastrointestinal function. Capsaicin is known to activate the transient receptor potential vanilloid type 1 (TRPV1), expressed in the mesenteric nervous system. Recent studies have also demonstrated its presence in epithelial cells but its role remains uncertain. Because capsaicin has been reported to inhibit colonic chloride secretion, we tested whether this effect of capsaicin could occur by direct action on epithelial cells. In mouse colon and model T84 human...

122. Smad7 inhibits autocrine expression of TGF-β2 in intestinal epithelial cells in baboon necrotizing enterocolitis - Namachivayam, Kopperuncholan; Blanco, Cynthia L.; MohanKumar, Krishnan; Jagadeeswaran, Ramasamy; Vasquez, Margarita; McGill-Vargas, Lisa; Garzon, Steven A.; Jain, Sunil K.; Gill, Ravinder K.; Freitag, Nancy E.; Weitkamp, Jörn-Hendrik; Seidner, Steven R.; Maheshwari, Akhil
Preterm infants may be at risk of necrotizing enterocolitis (NEC) due to deficiency of transforming growth factor-β 2 (TGF-β2) in the developing intestine. We hypothesized that low epithelial TGF-β2 expression in preterm intestine and during NEC results from diminished autocrine induction of TGF-β2 in these cells. Premature baboons delivered at 67% gestation were treated per current norms for human preterm infants. NEC was diagnosed by clinical and radiological findings. Inflammatory cytokines, TGF-β2, Smad7, Ski, and strawberry notch N (SnoN)/Ski-like oncoprotein (SKIL) was measured using quantitative reverse transcriptase-polymerase chain reaction, immunoblots, and immunohistochemistry. Smad7 effects were examined in transfected IEC6 intestinal...

123. Probiotics prevent necrotizing enterocolitis by modulating enterocyte genes that regulate innate immune-mediated inflammation - Ganguli, Kriston; Meng, Di; Rautava, Samuli; Lu, Lei; Walker, W. Allan; Nanthakumar, Nanda
Necrotizing enterocolitis (NEC), an extensive intestinal inflammatory disease of premature infants, is caused, in part, by an excessive inflammatory response to initial bacterial colonization due to the immature expression of innate immune response genes. In a randomized placebo-controlled clinical trial, supplementation of very low birth weight infants with probiotics significantly reduced the incidence of NEC. The primary goal of this study was to determine whether secreted products of these two clinically effective probiotic strains, Bifidobacterium infantis and Lactobacillus acidophilus, prevented NEC by accelerating the maturation of intestinal innate immune response genes and whether both strains are required for this effect....

124. Nordihydroguaiaretic acid improves metabolic dysregulation and aberrant hepatic lipid metabolism in mice by both PPARα-dependent and -independent pathways - Zhang, Haiyan; Shen, Wen-Jun; Cortez, Yuan; Kraemer, Fredric B.; Azhar, Salman
Creosote bush-derived nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, possesses antioxidant properties and functions as a potent antihyperlipidemic agent in rodent models. Here, we examined the effect of chronic NDGA treatment of ob/ob mice on plasma dyslipidemia, hepatic steatosis, and changes in hepatic gene expression. Feeding ob/ob mice a chow diet supplemented with either low (0.83 g/kg diet) or high-dose (2.5 g/kg diet) NDGA for 16 wk significantly improved plasma triglyceride (TG), inflammatory chemokine levels, hyperinsulinemia, insulin sensitivity, and glucose intolerance. NDGA treatment caused a marked reduction in liver weight and TG content, while enhancing rates of fatty acid oxidation. Microarray...

125. Conditional knockout of the Slc5a6 gene in mouse intestine impairs biotin absorption - Ghosal, Abhisek; Lambrecht, Nils; Subramanya, Sandeep B.; Kapadia, Rubina; Said, Hamid M.
The Slc5a6 gene expresses a plasma membrane protein involved in the transport of the water-soluble vitamin biotin; the transporter is commonly referred to as the sodium-dependent multivitamin transporter (SMVT) because it also transports pantothenic acid and lipoic acid. The relative contribution of the SMVT system toward carrier-mediated biotin uptake in the native intestine in vivo has not been established. We used a Cre/lox technology to generate an intestine-specific (conditional) SMVT knockout (KO) mouse model to address this issue. The KO mice exhibited absence of expression of SMVT in the intestine compared with sex-matched littermates as well as the expected normal...

126. Mechanosensitive Cl− secretion in biliary epithelium mediated through TMEM16A - Dutta, Amal K.; Woo, Kangmee; Khimji, Al-karim; Kresge, Charles; Feranchak, Andrew P.
Bile formation by the liver is initiated by canalicular transport at the hepatocyte membrane, leading to an increase in ductular bile flow. Thus, bile duct epithelial cells (cholangiocytes), which contribute to the volume and dilution of bile through regulated Cl− transport, are exposed to changes in flow and shear force at the apical membrane. The aim of the present study was to determine if fluid flow, or shear stress, is a signal regulating cholangiocyte transport. The results demonstrate that, in human and mouse biliary cells, fluid flow, or shear, increases Cl− currents and identify TMEM16A, a Ca2+-activated Cl− channel, as...

127. Hepatocyte-specific deletion of hepatocyte nuclear factor-4α in adult mice results in increased hepatocyte proliferation - Walesky, Chad; Gunewardena, Sumedha; Terwilliger, Ernest F.; Edwards, Genea; Borude, Prachi; Apte, Udayan
Hepatocyte nuclear factor-4α (HNF4α) is known as the master regulator of hepatocyte differentiation. Recent studies indicate that HNF4α may inhibit hepatocyte proliferation via mechanisms that have yet to be identified. Using a HNF4α knockdown mouse model based on delivery of inducible Cre recombinase via an adeno-associated virus 8 viral vector, we investigated the role of HNF4α in the regulation of hepatocyte proliferation. Hepatocyte-specific deletion of HNF4α resulted in increased hepatocyte proliferation. Global gene expression analysis showed that a majority of the downregulated genes were previously known HNF4α target genes involved in hepatic differentiation. Interestingly, ≥500 upregulated genes were associated with...

128. Ethanol administration exacerbates the abnormalities in hepatic lipid oxidation in genetically obese mice - Everitt, Hannah; Hu, Ming; Ajmo, Joanne M.; Rogers, Christopher Q.; Liang, Xiaomei; Zhang, Ray; Yin, Huquan; Choi, Alison; Bennett, Eric S.; You, Min
Alcohol consumption synergistically increases the risk and severity of liver damage in obese patients. To gain insight into cellular or molecular mechanisms underlying the development of fatty liver caused by ethanol-obesity synergism, we have carried out animal experiments that examine the effects of ethanol administration in genetically obese mice. Lean wild-type (WT) and obese (ob/ob) mice were subjected to ethanol feeding for 4 wk using a modified Lieber-DeCarli diet. After ethanol feeding, the ob/ob mice displayed much more pronounced changes in terms of liver steatosis and elevated plasma levels of alanine aminotransferase and aspartate aminotransferase, indicators of liver injury, compared...

129. The hepatic bile acid transporters Ntcp and Mrp2 are downregulated in experimental necrotizing enterocolitis - Cherrington, Nathan J.; Estrada, Teresa E.; Frisk, Harrison A.; Canet, Mark J.; Hardwick, Rhiannon N.; Dvorak, Bohuslav; Lux, Katie; Halpern, Melissa D.
Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency of premature infants and is characterized by an extensive hemorrhagic inflammatory necrosis of the distal ileum and proximal colon. We have previously shown that, during the development of experimental NEC, the liver plays an important role in regulating inflammation in the ileum, and accumulation of ileal bile acids (BA) along with dysregulation of ileal BA transporters contributes to ileal damage. Given these findings, we speculated that hepatic BA transporters would also be altered in experimental NEC. Using both rat and mouse models of NEC, levels of Cyp7a1, Cyp27a1, and the hepatic...

130. Oxidative modification of the intestinal mucus layer is a critical but unrecognized component of trauma hemorrhagic shock-induced gut barrier failure - Fishman, Jordan E.; Levy, Gal; Alli, Vamsi; Sheth, Sharvil; Lu, Qu; Deitch, Edwin A.
Recent studies demonstrate that mechanisms underlying gut barrier failure include systemic processes and less studied luminal processes. We thus tested the hypothesis that mucus layer oxidation is a component of trauma/hemorrhagic shock-induced gut injury and dysfunction. Male Sprague-Dawley rats underwent trauma/hemorrhagic shock. Controls underwent trauma only. Mucus from the terminal 30 cm of the ileum was collected, processed, and analyzed for reactive nitrogen intermediates (RNI)-mediated damage, reactive oxygen species (ROS)-induced damage, and total antioxidant capacity. The distal ileum was stained to quantify the mucus layer; gut permeability was assessed physiologically. A time course study was conducted to determine the temporal...

131. Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon - Zhang, Jin; Halm, Susan T.; Halm, Dan R.
Secretagogues acting at a variety of receptor types activate electrogenic K+ secretion in guinea pig distal colon, often accompanied by Cl− secretion. Distinct blockers of KCa1.1 (BK, Kcnma1), iberiotoxin (IbTx), and paxilline inhibited the negative short-circuit current (Isc) associated with K+ secretion. Mucosal addition of IbTx inhibited epinephrine-activated Isc (epiIsc) and transepithelial conductance (epiGt) consistent with K+ secretion occurring via apical membrane KCa1.1. The concentration dependence of IbTx inhibition of epiIsc yielded an IC50 of 193 nM, with a maximal inhibition of 51%. Similarly, IbTx inhibited epiGt with an IC50 of 220 nM and maximal inhibition of 48%. Mucosally added...

132. Xenin-25 increases cytosolic free calcium levels and acetylcholine release from a subset of myenteric neurons - Zhang, Sheng; Hyrc, Krzysztof; Wang, Songyan; Wice, Burton M.
Xenin-25 (Xen) is a 25 amino acid neurotensin-related peptide reportedly produced with glucose-dependent insulinotropic polypeptide (GIP) by a subset of K cells in the proximal gut. We previously showed exogenously administered Xen, with GIP but not alone, increases insulin secretion in humans and mice. In mice, this effect is indirectly mediated via a central nervous system-independent cholinergic relay in the periphery. Xen also delays gastric emptying, reduces food intake, induces gall bladder contractions, and increases gut motility and secretion from the exocrine pancreas, suggesting that some effects of Xen could be mediated by myenteric neurons (MENs). To determine whether Xen...

133. Active vitamin D (1,25-dihydroxyvitamin D3) increases host susceptibility to Citrobacter rodentium by suppressing mucosal Th17 responses - Ryz, Natasha R.; Patterson, Scott J.; Zhang, Yiqun; Ma, Caixia; Huang, Tina; Bhinder, Ganive; Wu, Xiujuan; Chan, Justin; Glesby, Alexa; Sham, Ho Pan; Dutz, Jan P.; Levings, Megan K.; Jacobson, Kevan; Vallance, Bruce A.
Vitamin D deficiency affects more that 1 billion people worldwide and is associated with an increased risk of developing a number of inflammatory/autoimmune diseases, including inflammatory bowel disease (IBD). At present, the basis for the impact of vitamin D on IBD and mucosal immune responses is unclear; however, IBD is known to reflect exaggerated immune responses to luminal bacteria, and vitamin D has been shown to play a role in regulating bacteria-host interactions. Therefore, to test the effect of active vitamin D on host responses to enteric bacteria, we gave 1,25(OH)2D3 to mice infected with the bacterial pathogen Citrobacter rodentium,...

134. TRPV4 activation in mouse submandibular gland modulates Ca2+ influx and salivation - Zhang, Yan; Catalán, Marcelo A.; Melvin, James E.
Transient receptor potential vanilloid subtype 4 (TRPV4) is a ligand-gated nonselective cation channel that participates in the transduction of mechanical and osmotic stimuli in different tissues. TRPV4 is activated by endogenous arachidonic acid metabolites, 4α-phorbol-12,13 didecanoate, GSK1016790A, moderate heat, and mechanical stress. TRPV4 is expressed in the salivary glands, but its expression pattern and function are poorly understood. The aim of this study was to evaluate the functional role of TRPV4 channels in the mouse submandibular gland. Using RT-PCR and Western blot analysis, we detected expression of TRPV4 message and protein, respectively, in the submandibular gland. Immunolocalization studies showed that...

135. Butyrate increases IL-23 production by stimulated dendritic cells - Berndt, Bradford E.; Zhang, Min; Owyang, Stephanie Y.; Cole, Tyler S.; Wang, Teresa W.; Luther, Jay; Veniaminova, Natalia A.; Merchant, Juanita L.; Chen, Chun-Chia; Huffnagle, Gary B.; Kao, John Y.
The gut microbiota is essential for the maintenance of intestinal immune homeostasis and is responsible for breaking down dietary fiber into short-chain fatty acids (SCFAs). Butyrate, the most abundant bioactive SCFA in the gut, is a histone deacetylase inhibitor (HDACi), a class of drug that has potent immunomodulatory properties. This characteristic of butyrate, along with our previous discovery that conventional dendritic cells (DCs) are required for the development of experimental colitis, led us to speculate that butyrate may modulate DC function to regulate gut mucosal homeostasis. We found that butyrate, in addition to suppressing LPS-induced bone marrow-derived DC maturation and...

136. Hepatic microtubule acetylation and stability induced by chronic alcohol exposure impair nuclear translocation of STAT3 and STAT5B, but not Smad2/3 - Fernandez, David J.; Tuma, Dean J.; Tuma, Pamela L.
Although alcoholic liver disease is clinically well described, the molecular basis for alcohol-induced hepatotoxicity is not well understood. Previously, we found that alcohol exposure led to increased microtubule acetylation and stability in polarized, hepatic WIF-B cells and in livers from ethanol-fed rats. Because microtubules are known to regulate transcription factor nuclear translocation and dynamic microtubules are required for translocation of at least a subset of these factors, we examined whether alcohol-induced microtubule acetylation and stability impair nuclear translocation. We examined nuclear delivery of factors representing the two mechanisms by which microtubules regulate translocation. To represent factors that undergo directed delivery,...

137. Lactobacillus acidophilus upregulates intestinal NHE3 expression and function - Singh, Varsha; Raheja, Geetu; Borthakur, Alip; Kumar, Anoop; Gill, Ravinder K.; Alakkam, Anas; Malakooti, Jaleh; Dudeja, Pradeep K.
A major mechanism of electroneutral NaCl absorption in the human ileum and colon involves coupling of Na+/H+ and Cl−/HCO3− exchangers. Disturbances in these mechanisms have been implicated in diarrheal conditions. Probiotics such as Lactobacillus have been indicated to be beneficial in the management of gastrointestinal disorders, including diarrhea. However, the molecular mechanisms underlying antidiarrheal effects of probiotics have not been fully understood. We have previously demonstrated Lactobacillus acidophilus (LA) to stimulate Cl−/HCO3− exchange activity via an increase in the surface levels and expression of the Cl−/HCO3− exchanger DRA in vitro and in vivo. However, the effects of LA on NHE3,...

138. Vitamin D deficiency: protective against enteric infection? - Christakos, Sylvia

139. Association of HLA-DQ gene with bowel transit, barrier function, and inflammation in irritable bowel syndrome with diarrhea - Vazquez-Roque, Maria I.; Camilleri, Michael; Smyrk, Thomas; Murray, Joseph A.; O'Neill, Jessica; Carlson, Paula; Lamsam, Jesse; Eckert, Deborah; Janzow, Denise; Burton, Duane; Ryks, Michael; Rhoten, Deborah; Zinsmeister, Alan R.
Patients with irritable bowel syndrome (IBS) with diarrhea (IBS-D) carrying human leukocyte antigen (HLA)-DQ2/8 genotypes benefit from gluten withdrawal. Our objective was to compare gastrointestinal barrier function, mucosal inflammation, and transit in nonceliac IBS-D patients and assess association with HLA-DQ2/8 status. In 45 IBS-D patients who were naive to prior exclusion of dietary gluten, we measured small bowel (SB) and colonic mucosal permeability by cumulative urinary lactulose and mannitol excretion (0–2 h for SB and 8–24 h for colon), inflammation on duodenal and rectosigmoid mucosal biopsies (obtained in 28 of 45 patients), tight junction (TJ) protein mRNA and protein expression...

140. Downregulation of nuclear receptor FXR is associated with multiple malignant clinicopathological characteristics in human hepatocellular carcinoma - Su, Hongying; Ma, Chuang; Liu, Jingfeng; Li, Ningbo; Gao, Meiqin; Huang, Aimin; Wang, Xichun; Huang, Wendong; Huang, Xiongfei
The nuclear receptor farnesoid X receptor (FXR) acts as a liver protector by regulating normal liver homeostasis. Spontaneously developed liver tumors have been found in FXR-null mice. However, the role of FXR in the tumorigenesis of human hepatocellular carcinoma (HCC) is still poorly understood. In this study, we measured the expression of FXR and its primary target gene, small heterodimer partner, and analyzed the clinical significance of FXR expression in HCC patients. A lentiviral vector that selectively overexpresses FXR was used to investigate the function of FXR in HCC cell proliferation both in vitro and in vivo. Our data showed...

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