bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular mechanisms of leukocyte recruitment in postischemic liver microcirculation
Authors: Kubes Paul , Payne Derrice , Woodman Richard C.
Published: March 2015

Evidence shows that leukocyte recruitment into inflamed liver sinusoids does not require selectins, with one notable exception: ischemia-reperfusion (I/R). We used intravital microscopy to directly visualize the liver microcirculation during I/R and localized endotoxemia (liver superfused with lipopolysaccharide). General anti-selectin therapy (fucoidan) or anti-adhesion therapy with an antithrombin inhibitor (hirudin) was also used. Many neutrophils rolled and adhered in postsinusoidal vessels and sequestered in the sinusoids during I/R and local endotoxin superfusion. Although fucoidan blocked rolling in both forms of inflammation, leukocyte recruitment into sinusoids was only blocked in I/R. Adhesion was also inhibited in postischemic sinusoids with a second anti-adhesive agent (hirudin). Because liver I/R inevitably induces ischemia upstream in the intestine, anti-selectin therapy may prevent intestinal injury, which could prevent downstream liver inflammation. To test this hypothesis, we completely removed the intestine and rerouted blood flow from the superior mesenteric artery to the superior mesenteric vein. I/R was induced in the liver microcirculation, and many leukocytes rolled and adhered in postsinusoidal venules and adhered in sinusoids. Although fucoidan significantly reduced the rolling in postsinusoidal vessels, adhesion persisted in the sinusoids. Our data suggest that anti-adhesion therapy is effective in liver I/R in the sinusoids and postsinusoidal venules, perhaps in part due to its beneficial effect on the intestine.
TRPC5 as a candidate for the nonselective cation channel activated by muscarinic stimulation in murine stomach
Authors: Lee Young Mee , Kim Byung Joo , Kim Hyun Jin , Yang Dong Ki , Zhu Mei Hong , Lee Kyu Pil , So Insuk , Kim Ki Whan
Published: March 2015

We investigated which transient receptor potential (TRP) channel is responsible for the nonselective cation channel (NSCC) activated by carbachol (CCh) in murine stomach with RT-PCR and the electrophysiological method. All seven types of TRP mRNA were detected in murine stomach with RT-PCR. When each TRP channel was expressed, the current-voltage relationship of mTRP5 was most similar to that recorded in murine gastric myocytes. mTRP5 showed a conductance order of Cs+> K+> Na+, similar to that in the murine stomach. With 0.2 mM GTPγS in the pipette solution, the current was activated transiently in both NSCC in the murine stomach and the expressed mTRP5. Both NSCC activated by CCh in murine stomach and mTRP5 were inhibited by intracellularly applied anti-Gq/11antibody, PLC inhibitor U-73122, IICR inhibitor 2-aminoethoxydiphenylborate, and nonspecific cation channel blockers La3+and flufenamate. There were two other unique properties. Both the native NSCC and mTRP5 were activated by 1-oleoyl-2-acetyl-sn-glycerol. Without the activation of NSCC by CCh, the NSCC in murine stomach was constitutively active like mTRP5. From the above results, we suggest that mTRP5 might be a candidate for the NSCC activated by ACh or CCh in murine stomach.
Ameliorating effect of anti-Fas ligand MAb on wasting disease in murine model of chronic colitis
Authors: Dan N. , Kanai T. , Totsuka T. , Iiyama R. , Yamazaki M. , Sawada T. , Miyata T. , Yagita H. , Okumura K. , Watanabe M.
Published: March 2015

Fas/Fas ligand (FasL) interaction has been implicated in the pathogenesis of various diseases. To clarify the involvement of Fas/FasL in the pathogenesis of intestinal inflammation, we investigated the preventive and therapeutic effects of neutralizing anti-FasL monoclonal antibody (MAb) on the development of chronic colitis induced by adaptive transfer of CD4+CD45RBhigh T cells to SCID mice. Administration of anti-FasL MAb from 1 day after T cell transfer (prevention study) resulted in a significant improvement of clinical manifestations such as wasting and diarrhea. However, histological examination showed that mucosal inflammation in the colon, such as infiltration of T cells and macrophages, was not improved by the anti-FasL MAb treatment. In vitro studies showed that anti-FasL MAb did not inhibit IFN-γ production by anti-CD3/CD28-stimulated lamina propria CD4+ T cells but suppressed TNF-α and IL-1β production by lamina propria mononuclear cells. Therapeutic administration of anti-FasL MAb from 3 wk after T cell transfer also improved ongoing wasting disease but not intestinal inflammation. These results suggest that the Fas/FasL interaction plays a critical role in regulating systemic wasting disease but not local intestinal inflammation.
Interleukin-1β activates specific populations of enteric neurons and enteric glia in the guinea pig ileum and colon
Authors: Tjwa Eric T. T. L. , Bradley Joelle M. , Keenan Catherine M. , Kroese Alfons B. A. , Sharkey Keith A.
Published: March 2015

Fos expression was used to assess whether the proinflammatory cytokine interleukin-1β (IL-1β) activated specific, chemically coded neuronal populations in isolated preparations of guinea pig ileum and colon. Whether the effects of IL-1β were mediated through a prostaglandin pathway and whether IL-1β induced the expression of cyclooxygenase (COX)-2 was also examined. Single- and double-labeling immunohistochemistry was used after treatment of isolated tissues with IL-1β (0.1-10 ng/ml). IL-1β induced Fos expression in enteric neurons and also in enteric glia in the ileum and colon. For enteric neurons, activation was concentration-dependent and sensitive to indomethacin, in both the myenteric and submucosal plexuses in both regions of the gut. The maximum proportion of activated neurons differed between the ileal (∼15%) and colonic (∼42%) myenteric and ileal (∼60%) and colonic (∼75%) submucosal plexuses. The majority of neurons activated in the myenteric plexus of the ileum expressed nitric oxide synthase (NOS) or enkephalin immunoreactivity. In the colon, activated myenteric neurons expressed NOS. In the submucosal plexus of both regions of the gut, the majority of activated neurons were vasoactive intestinal polypeptide (VIP) immunoreactive. After treatment with IL-1β, COX-2 immunoreactivity was detected in the wall of the gut in both neurons and nonneuronal cells. In conclusion, we have found that the proinflammatory cytokine IL-1β specifically activates certain neurochemically defined neural pathways and that these changes may lead to disturbances in motility observed in the inflamed bowel.
A 5-HT4 agonist mosapride enhances rectorectal and rectoanal reflexes in guinea pigs
Authors: Shimatani Hidehiko , Kojima Yu , Kadowaki Makoto , Nakagawa Tadashi , Fujii Hisao , Nakajima Yoshiyuki , Takaki Miyako
Published: March 2015

The rectal distension-evoked reflex rectal (R-R) contractions and internal anal sphincter (R-IAS) relaxations in guinea pigs were generated through the extrinsic sacral excitatory nerve pathway (pelvic nerves) and the intrinsic cholinergic excitatory and nitrergic inhibitory nerve pathways. The aim of the present study was to evaluate whether a prokinetic benzamide, mosapride, enhances the R-R and R-IAS reflexes mediated via 5-HT4 receptors in the guinea pig. The mechanical activities of the R and IAS were recorded with a balloon connected to a pressure transducer and a strain gauge force transducer in the anesthetized guinea pig with intact spinal-intestinal pathways. Gradual and sustained rectal distension evoked R-R contractions and synchronous R-IAS relaxations. Mosapride (0.1–1.0 mg/kg iv) dose-dependently enhanced both R-R and R-IAS reflex responses. Reflex indexes for R-R and R-IAS maximally increased from 1.0 (control) to 1.92 and 1.88, respectively. A specific 5-HT4 receptor antagonist, GR 113808 (1.0 mg/kg iv), antagonized the enhancement of the R-R and R-IAS reflexes induced by mosapride 1.0 mg/kg iv. The present results indicate that mosapride enhanced the R-R and R-IAS reflexes mediated through 5-HT4 receptors.
Local presentation of Steel factor increases expression of c-kit immunoreactive interstitial cells of Cajal in culture
Authors: Rich Adam , Miller Steven M. , Gibbons Simon J. , Malysz John , Szurszewski Joseph H. , Farrugia G.
Published: March 2015

The binding of Steel factor (SF) to c-kit initiates a signaling pathway essential for development and maintenance of interstitial cells of Cajal (ICC). Soluble and membrane-bound isoforms of SF are expressed in the gastrointestinal tract, but the role for either isoform in supporting ICC development is unknown. The aim of this study was to determine the role of SF in supporting ICC in culture. ICC were cultured from dissociated mouse jejunum and grown with fibroblast cell lines that produced either soluble, membrane-bound or membrane-restricted SF. ICC were identified and counted by c-kit immunoreactivity. The number of c-kit immunoreactive cells was greater in the coculture system compared with cultures grown without SF-producing fibroblasts. All forms of SF-producing fibroblasts increased ICC number in culture but physical separation of the fibroblasts from the c-kit immunoreactive cells, the addition of exogenous SF to the culture medium, or fibroblast-conditioned media did not. These results are consistent with the hypothesis that the membrane-bound form of SF preferentially contributes to expression of c-kit-positive ICC under cell culture conditions.
Enterocyte apoptosis after enterectomy in mice is activated independent of the extrinsic death receptor pathway
Authors: Knott Andrew W. , O'Brien David P. , Juno Russell J. , Zhang Yufang , Williams Jodi L. , Erwin Christopher R. , Warner Brad W.
Published: March 2015

Intestinal adaptation following small bowel resection (SBR) is associated with greater rates of enterocyte apoptosis by unknown mechanism(s). Because postresection adaptation is associated with increased translocation of luminal bacteria, we sought to characterize the role for the extrinsic, death receptor pathway for the activation of enterocyte apoptosis after massive SBR. We first performed SBR or sham operations in mice, and the temporal expression of caspases 8, 9, and 3, death receptors tumor necrosis factor receptor-1 (TNFR1) and Fas and corresponding ligands (TNF and Fas ligand) was determined in the remnant intestine at various postoperative time points. Ileal TNFR1and Fas expression were then measured after SBR in the setting of increased (waved-2 mice) or decreased (exogenous EGF administration) apoptosis. Finally, intestinal adaptation and apoptosis were recorded in the remnant ileum after SBR in TNFR1-null and Fas-null mice. The expression of death receptor family proteins and caspases demonstrated only modest changes after SBR and did not correlate with the histological appearance of apoptosis. In the setting of accelerated apoptosis, TNFR1and Fas expression were paradoxically decreased. Apoptotic and adaptive responses were preserved in both TNFR1-null and Fas-null mice. These results suggest that the mechanism for increased enterocyte apoptosis following massive SBR does not appear to involve the extrinsic, death receptor-mediated pathway.
Role of ICAM-1 in chronic ethanol consumption-enhanced liver injury after gut ischemia-reperfusion in rats
Authors: Horie Yoshinori , Yamagishi Yoshiyuki , Kato Shinzo , Kajihara Mikio , Tamai Hironao , Granger D. Neil , Ishii Hiromasa
Published: March 2015

Intercellular adhesion molecule-1 (ICAM-1) has been implicated in the hepatic microvascular dysfunction elicited by gut ischemia-reperfusion (I/R). Although the effects of chronic ethanol (EtOH) consumption on the liver are well known, it remains unclear whether this condition renders the hepatic microcirculation more vulnerable to the deleterious effects of gut and/or hepatic I/R. The objectives of this study were to determine whether chronic EtOH consumption alters the severity of gut I/R-induced hepatic microvascular dysfunction and hepatocellular injury and to determine whether ICAM-1 contributes to this response. Male Wistar rats, pair fed for 6 wk a liquid diet containing EtOH or an isocaloric control diet, were exposed to gut I/R. Intravital video microscopy was used to monitor leukocyte recruitment in the hepatic microcirculation, the number of nonperfused sinusoids (NPS), and plasma concentrations of endotoxin and tumor necrosis factor-α. Plasma alanine aminotransferase (ALT) levels were measured 6 h after the onset of reperfusion. In control rats, gut I/R elicited increases in the number of stationary leukocytes, NPS, and plasma endotoxin, tumor necrosis factor-α, and ALT. In EtOH-fed rats, the gut I/R-induced increases in NPS and leukostasis were blunted in the midzonal region, while exaggerated leukostasis was noted in the pericentral region and terminal hepatic venules. Chronic EtOH consumption also enhanced the gut I/R-induced increase in plasma endotoxin and ALT. The exaggerated responses to gut I/R normally seen in EtOH-fed rats were largely prevented by pretreatment with a blocking anti-ICAM-1 monoclonal antibody. In conclusion, these results suggest that chronic EtOH consumption enhances gut I/R-induced hepatic microvascular dysfunction and hepatocellular injury in the pericentral region and terminal hepatic venules via an enhanced hepatic expression of ICAM-1.
Iron activates NF-κB in Kupffer cells
Authors: She Hongyun , Xiong Shigang , Lin Min , Zandi Ebrahim , Giulivi Cecilia , Tsukamoto Hidekazu
Published: March 2015

10.1152/ajpgi.00108. 2002.— Iron exacerbates various types of liver injury in which nuclear factor (NF)-κB-driven genes are implicated. This study tested a hypothesis that iron directly elicits the signaling required for activation of NF-κB and stimulation of tumor necrosis factor (TNF)-α gene expression in Kupffer cells. Addition of Fe2+but not Fe3+(∼5–50 μM) to cultured rat Kupffer cells increased TNF-α release and TNF-α promoter activity in a NF-κB-dependent manner. Cu+but not Cu2+stimulated TNF-α protein release and promoter activity but with less potency. Fe2+caused a disappearance of the cytosolic inhibitor κBα, a concomitant increase in nuclear p65 protein, and increased DNA binding of p50/p50 and p65/p50 without affecting activator protein-1 binding. Addition of Fe2+to the cells resulted in an increase in electron paramagnetic resonance-detectable ·OH peaking at 15 min, preceding activation of NF-κB but coinciding with activation of inhibitor κB kinase (IKK) but not c-Jun NH2-terminal kinase. In conclusion, Fe2+serves as a direct agonist to activate IKK, NF-κB, and TNF-α promoter activity and to induce the release of TNF-α protein by cultured Kupffer cells in a redox status-dependent manner. We propose that this finding offers a molecular basis for iron-mediated accentuation of TNF-α-dependent liver injury.
Regulation of atrial natriuretic peptide secretion by cholinergic and PACAP neurons of the gastric antrum
Authors: Gower William R. , Dietz John R. , McCuen Robert W. , Fabri Peter J. , Lerner Ethan A. , Schubert Mitchell L.
Published: March 2015

Atrial natriuretic peptide (ANP) released from enterochromaffin cells helps regulate antral somatostatin secretion, but the mechanisms regulating ANP secretion are not known. We superfused rat antral segments with selective neural agonists/antagonists to identify the neural pathways regulating ANP secretion. The nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium (DMPP) stimulated ANP secretion; the effect was abolished by hexamethonium but doubled by atropine. Atropine's effect implied that DMPP activated concomitantly cholinergic neurons that inhibit and noncholinergic neurons that stimulate ANP secretion, the latter effect predominating. Methacholine inhibited ANP secretion. Neither bombesin nor vasoactive intestinal polypeptide stimulated ANP secretion, whereas pituitary adenylate cyclase-activating polypeptide (PACAP)-27, PACAP-38, and maxadilan [PACAP type 1 (PAC1) agonist] each stimulated ANP secretion. The PAC1 antagonist M65 1) abolished PACAP-27/38-stimulated ANP secretion; 2) inhibited basal ANP secretion by 28 ± 5%, implying that endogenous PACAP stimulates ANP secretion; and 3) converted the ANP response to DMPP from 109 ± 21% above to 40 ± 5% below basal, unmasking the cholinergic component and indicating that DMPP activated PACAP neurons that stimulate ANP secretion. Combined atropine and M65 restored DMPP-stimulated ANP secretion to basal levels. ANP secretion in the antrum is thus regulated by intramural cholinergic and PACAP neurons; cholinergic neurons inhibit and PACAP neurons stimulate ANP secretion.
IV. Visceral afferents: an update
Authors: Raybould Helen E.
Published: March 2015

The number of articles published in American Journal of Physiology Gastrointestinal and Liver Physiology over the last 15 years on visceral afferents has increased dramatically. This reflects our growing ability to study the characteristics and function of visceral afferents and also the recognition of their importance in the maintenance of homeostasis and also in a number of pathophysiological conditions. However, there are several key unanswered questions concerning the function of visceral afferents that await further investigation.
Curcumin ameliorates ethanol and nonethanol experimental pancreatitis
Authors: Gukovsky Ilya , Reyes Christopher N. , Vaquero Eva C. , Gukovskaya Anna S. , Pandol Stephen J.
Published: March 2015

Treatments for pancreatitis are limited. Activation of transcription factor NF-κB, a key regulator of inflammatory molecule expression, is an early event in experimental pancreatitis and correlates with the inflammatory response. We report here that curcumin, a natural phytochemical known to inhibit NF-κB and activator protein (AP)-1, another important proinflammatory transcription factor, ameliorates pancreatitis in two rat models. In both cerulein pancreatitis and pancreatitis induced by a combination of ethanol diet and low-dose CCK, curcumin improved the severity of the disease as measured by a number of parameters (histology, serum amylase, pancreatic trypsin, and neutrophil infiltration). Curcumin markedly inhibited NF-κB and AP-1 activation, assessed by DNA binding and degradation of inhibitory IκB proteins, and the induction of mRNAs for cytokines IL-6 and TNF-α, the chemokine KC, and inducible nitric oxide synthase in pancreas. Curcumin also blocked CCK-induced NF-κB and AP-1 activation in isolated pancreatic acini. Our findings indicate that blocking key signals of the inflammatory response ameliorates pancreatitis in both ethanol and nonethanol models. They suggest that curcumin, which is currently in clinical trials for cancer prevention, may be useful for treatment of pancreatitis.
ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization
Authors: Catalán Marcelo , Cornejo Isabel , Figueroa Carlos D. , Niemeyer María Isabel , Sepúlveda Francisco V. , Cid L. Pablo
Published: March 2015

The principal function of the colon in fluid homeostasis is the absorption of NaCl and water. Apical membrane Na+ channels, Na+/H+ and Cl−/HCO[Formula: see text] exchangers, have all been postulated to mediate NaCl entry into colonocytes. The identity of the basolateral exit pathway for Cl− is unknown. We have previously demonstrated the presence of the ClC-2 transcript in the guinea pig intestine. Now we explore in more detail, the tissue and cellular distribution of chloride channel ClC-2 in the distal colon by in situ hybridization and immunohistochemistry. The patch-clamp technique was used to characterize Cl− currents in isolated surface epithelial cells from guinea pig distal colon and these were compared with those mediated by recombinant guinea pig (gp)ClC-2. ClC-2 mRNA and protein were found in the surface epithelium of the distal colon. Immunolocalization revealed that, in addition to some intracellular labeling, ClC-2 was present in the basolateral membranes but absent from the apical pole of colonocytes. Isolated surface epithelial cells exhibited hyperpolarization-activated chloride currents showing a Cl− > I− permeability and Cd2+ sensitivity. These characteristics, as well as some details of the kinetics of activation and deactivation, were very similar to those of recombinant gpClC-2 measured in parallel experiments. The presence of active ClC-2 type currents in surface colonic epithelium, coupled to a basolateral location for ClC-2 in the distal colon, suggests a role for ClC-2 channel in mediating basolateral membrane exit of Cl− as an essential step in a NaCl absorption process.
Gut perception in humans is modulated by interacting gut stimuli
Authors: Accarino Anna M. , Azpiroz Fernando , Malagelada Juan-R
Published: March 2015

Digestive symptoms depend on multiple interacting gut stimuli, but integration of visceral afferent traffic is poorly understood. Our aim was to elucidate the contribution of simultaneous intestinal stimuli to conscious perception. In 17 healthy subjects, we performed stimulus-response trials of jejunal distensions (1-min duration at 5-min intervals in 8-ml increments) either alone or with a background electrical stimulus, and stimulus-response trials of electrical stimuli (1-min duration at 5-min intervals in 6-mA steps) either alone or with a background intestinal distension. The four stimulus-response trials were performed concomitantly applying the different types of stimuli in random order. Perception was measured on a scale of 0 to 6. Background stimulation markedly increased perception of test stimuli, reducing tolerance from 44 ± 3 to 32 ± 3 ml and from 67 ± 6 to 33 ± 4 mA ( P < 0.05 for both). However, whereas jejunal distensions below the perception threshold did not modify perception of the background stimulus (4 ± 1% change; not significant), unperceived electrical stimuli exerted a sensitizing effect and increased perception of the background distension up to uncomfortable levels (111 ± 40% increment; P < 0.05). In conclusion, activation of different pools of jejunal afferents produces summative effects on perception, and this sensitizing effect can be exerted by unperceived stimulation of mechanoinsensitive jejunal afferents.
II. Neural control of the aging gut: can an old dog learn new tricks?
Authors: Hall Karen E.
Published: March 2015

There has been a dramatic increase in funding available for aging research, primarily due to the fact that answers to questions on aging are likely to have a major impact on the well-being and healthy aging of the world's population for decades to come. The incidence of certain gastrointestinal problems, such as dysphagia and constipation, increases dramatically with age. Changes in gastrointestinal neuromuscular function with aging have been demonstrated in both human and animal models of aging. This article focuses on recent advances in our knowledge of the effects of aging on gastrointestinal function, treatment options, and future opportunities for research.
Differences in intestinal calcium and phosphate transport between low and high bone density mice
Authors: Armbrecht H. J. , Boltz M. A. , Hodam T. L.
Published: March 2015

The purpose of this study was to determine whether there are differences in intestinal Ca and phosphate transport in mice having different peak bone densities. Intestinal transport was measured in C57BL/6 (C57, low bone density) and C3H/He (C3H, high bone density) female mice. Unidirectional (mucosal to serosal) transport of Ca was 58% higher in C3H compared with C57 mice, as measured by everted duodenal sacs. The capacity of the duodenal mucosa to take up Ca was also higher in the C3H mice. This uptake highly correlated with Ca transport across the intestine. 1,25-Dihydroxyvitamin D3[1,25(OH)2D3], which stimulates intestinal Ca absorption, markedly stimulated unidirectional Ca transport and uptake to similar levels in both strains of mice. On the other hand, unidirectional phosphate transport in C3H mice was only 36% that of C57 mice. mRNA levels of the plasma membrane Ca pump were 90% higher in the duodenum of C3H mice. There was no difference between strains in duodenal calbindin or 24-hydroxylase mRNA levels. Regarding vitamin D metabolism, there was no difference in serum 1,25(OH)2D3levels or in renal 1α-hydroxylase mRNA levels. The combination of high intestinal Ca transport and low phosphate transport may contribute to the high peak bone density seen in the C3H relative to the C57 mouse.
IL-6 is essential for development of gut barrier dysfunction after hemorrhagic shock and resuscitation in mice
Authors: Yang Runkuan , Han Xiaonan , Uchiyama Takashi , Watkins Simon K. , Yaguchi Arino , Delude Russell L. , Fink Mitchell P.
Published: March 2015

We sought to determine the role of IL-6 as a mediator of the alterations in gut barrier function that occur after hemorrhagic shock and resuscitation (HS/R). C57Bl/6 wild-type (WT) and IL-6 knockout (KO) mice on a C57Bl/6 background were subjected to either a sham procedure or HS/R. Organ and tissue samples were obtained 4 h after resuscitation. In WT mice, HS/R significantly increased ileal mucosal permeability to fluorescein isothiocyanate-labeled dextran (average molecular mass, 4 kDa) and bacterial translocation to mesenteric lymph nodes. These alterations in gut barrier function were not observed in IL-6 KO animals. HS/R increased ileal steady-state mRNA levels for IL-6, TNF, and IL-10 in WT but not in IL-6 KO mice. Ileal mucosal expression of the tight junction protein, ZO-1, decreased after HS/R in WT but not IL-6 KO mice. Collectively, these data support the view that expression of IL-6 is essential for the development of gut barrier dysfunction after HS/R.
Mechanisms by which endogenous glucocorticoid protects against indomethacin-induced gastric injury in rats
Authors: Filaretova Ludmila , Tanaka Akiko , Miyazawa Tohru , Kato Shinichi , Takeuchi Koji
Published: March 2015

We investigated the mechanisms underlying the protective action of glucocorticoids against indomethacin-induced gastric lesions. One-week adrenalectomized rats with or without corticosterone replacement (4 mg/kg sc) were administered indomethacin (25 mg/kg sc), and gastric secretion (acid, pepsin, and mucus), motility, microvascular permeability, and blood glucose levels were examined. Indomethacin caused gastric lesions in sham-operated rats, with an increase in gastric motility and microvascular permeability as well as a decrease in mucus secretion. Adrenalectomy significantly worsened the lesions and potentiated these functional disorders. Glucose levels were lowered by indomethacin in sham-operated rats, and this response was enhanced by adrenalectomy. The changes observed in adrenalectomized rats were prevented by supplementations of corticosterone at a dose mimicking the indomethacin-induced rise in corticosterone, whereas the protective effect of corticosterone was attenuated by RU-38486, a glucocorticoid receptor antagonist. We conclude that the gastroprotective action of endogenous glucocorticoids may be provided by their support of glucose homeostasis and inhibitory effects on enhanced gastric motility and microvascular permeability as well as maintaining the production of mucus.
Cosensitivity of vagal mucosal afferents to histamine and 5-HT in the rat jejunum
Authors: Kreis M. E. , Jiang W. , Kirkup A. J. , Grundy D.
Published: March 2015

A complex sensitivity of afferent nerves in the mesentery of the rat jejunum to systemic administration of histamine has recently been demonstrated. In the present study, we aimed to characterize subpopulations of mesenteric afferents that mediate this afferent nerve response. Multiunit afferent discharge was recorded from mesenteric nerves supplying the proximal jejunum in anesthetized rats. The majority of mesenteric bundles (84%) exhibited biphasic responses to histamine (8 μmol/kg), and these bundles also responded to 2-methyl-5-HT (2m5HT). In contrast, monophasic responses lacked a short-latency component, and these bundles failed to respond to 2m5HT. Single-unit analysis revealed a population of afferents that possessed cosensitivity for 2m5HT and histamine. This population of afferents was absent in chronically vagotomized animals, whereas mucosal anesthesia with luminal lidocaine reversibly converted the biphasic profile to a monophasic one. Ondansetron (500 μg/kg) blocked the response to 2m5HT with no effect on the profile of the histamine response, whereas pyrilamine (5 mg/kg) blocked the histamine response without affecting the response to 2m5HT. We conclude that histamine-sensitive afferents exist in the rat proximal jejunum that also respond to 5-HT via the 5-HT3receptor. These fibers appear to be vagal afferents originating in the intestinal mucosa and may be involved in the organization of mast cell-mediated responses.
Electrical activity induced by nitric oxide in canine colonic circular muscle
Authors: Keef K. D. , Anderson U. , O'Driscoll K. , Ward S. M. , Sanders K. M.
Published: March 2015

Nitric oxide generates slow electrical oscillations (SEOs) in cells near the myenteric edge of the circular muscle layer, which resemble slow waves generated by interstitial cells of Cajal (ICCs) at the submucosal edge of this muscle. The properties of SEOs were studied to determine whether these events are similar to slow waves. Rapid frequency membrane potential oscillations (MPOs; 16 ± 1 cycles/min and 9.6 ± 0.2 mV) were recorded from control muscles near the myenteric edge. Sodium nitroprusside (0.3 μM) reduced MPOs and initiated SEOs (1.3 ± 0.3 cycles/min and 13.4 ± 1.4 mV amplitude). SEOs were abolished by the guanylate cyclase inhibitor 1H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxaline-1-one (10 μM). MPOs were abolished by nifedipine (1 μM), whereas SEO frequency increased and the amount of depolarization decreased. BAY K 8644 (1 μM) prolonged SEOs and reduced their frequency. SEOs were abolished by Ni2+ (0.5 mM), low Ca2+ solution (0.1 mM Ca2+), cyclopiazonic acid (10 μM), and the mitochondrial uncouplers antimycin (10 μM) and carbonyl cyanide p-trifluoromethoxyphenylhydrazone (1 μM). Oligomycin (10 μM) was without effect. These effects are similar to those described for colonic slow waves. Our results suggest that nitric oxide-induced SEOs are similar in mechanism to slow waves, an activity not previously thought to be generated by myenteric pacemakers.
STAT1 plays an essential role in LPS/D-galactosamine-induced liver apoptosis and injury
Authors: Kim Won-Ho , Hong Feng , Radaeva Svetlana , Jaruga Barbara , Fan Saijun , Gao Bin
Published: March 2015

Interferon-γ (IFN-γ) has been implicated in liver damage in animal models and chronic hepatitis C infection; however, the underlying mechanism is not clear. Here we examined the role of STAT1, a key signaling molecule for IFN-γ, in a model of murine hepatitis induced by the injection of LPS/d-galactosamine and in human hepatoma Hep3B cells. STAT1 is rapidly activated and highly induced after injection of LPS/d-galactosamine. Both overexpression of STAT1 and hepatocellular damage are located in the same pericentral region. Disruption of the STAT1 gene abolishes LPS/d-galactosamine-induced liver injury. Studies from IFN-γ-deficient mice indicate that IFN-γ is the major cytokine responsible for activation and hyperexpression of STAT1 in LPS/d-galactosamine-induced hepatitis. Hep3B cells overexpressing dominant negative STAT1 are resistant to IFN-γ and IFN-γ + TNF-α-induced cell death, whereas Hep3B cells overexpressing wild-type STAT1 are more susceptible to cell death. Taken together, these findings suggest that STAT1 plays an essential role in LPS/d-galactosamine-induced liver apoptosis and injury.
Slowing of intestinal transit by fat or peptide YY depends on β-adrenergic pathway
Authors: Lin Henry C. , Neevel Corynn , Chen Peng-Sheng , Suh Gina , Chen Jin Hai
Published: March 2015

Although the enteric reflex pathway triggered by volume distension is known to depend on an adrenergic nerve, it is not known whether the slowing of intestinal transit by fat or peptide YY (PYY) also depends on an adrenergic pathway. The aim of this study was to test the hypotheses that the slowing of transit by fat or PYY may depend on a β-adrenergic pathway, and this adrenergic pathway may act via the serotonergic and opioid pathways previously observed for the slowing of transit by fat. Eighteen dogs were equipped with duodenal and midgut fistulas. The small intestine was compartmentalized into the proximal and distal half of gut. The role of adrenergic, serotonergic, and opioid pathways was then tested in the slowing of intestinal transit by fat, PYY, and norepinephrine. Intestinal transit results were compared as the cumulative percent marker of recovery over 30 min. We found that the slowing of transit by fat, PYY, or norepinephrine was reversed by propranolol. In addition, the slowing effect of fat was reversed by metoprolol (β1-adrenoreceptor antagonist) but not phentolamine (α-adrenoreceptor antagonist). Furthermore, norepinephrine-induced slowing of transit was reversed by ondansetron (5-HT3receptor antagonist) or naloxone (opioid receptor antagonist). Extending these physiological results, we also found by immunohistochemistry that β1-adrenoreceptors are expressed by neurons of the intrinsic plexuses of the small intestine. We conclude that the slowing of intestinal transit by fat or PYY depends on a β-adrenergic pathway and that this adrenergic pathway acts on serotonergic and opioid pathways.
Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells
Authors: Nakamura Eiji , Hagen Susan J.
Published: March 2015

Ammonia is a cytotoxic factor produced during Helicobacter pylori infection that may reduce the survival of surface epithelial cells. Here we examine whether ammonia kills cells and whether l-glutamine (l-Gln) protects against cell death by stimulating ammonia detoxification pathways. Cell viability and vacuolation were quantified in rat gastric epithelial (RGM1) cells incubated with ammonium chloride at pH 7.4 in the presence or absence of l-Gln. Incubation of RGM1 cells with ammonium chloride caused a dose-dependent increase in cell death and vacuolation, which were both inhibited byl-Gln. We show that RGM1 cells metabolize ammonia to urea via arginase, a process that is stimulated by l-Gln and results in reduced ammonia cytotoxicity. l-Gln also inhibits the uptake and facilitates the extrusion of ammonia from cells. Blockade of glutamine synthetase did not reduce the survival of RGM1 cells, demonstrating that the conversion ofl-glutamate and ammonia to l-Gln is not involved in ammonia detoxification. Thus our data support a role forl-Gln and arginase in protection against ammonia-induced cell death in gastric epithelial cells.
Interferon-γ activates EGF receptor and increases TGF-α in T84 cells: implications for chloride secretion
Authors: Uribe Jorge M. , McCole Declan F. , Barrett Kim E.
Published: March 2015

IFN-γ inhibits intestinal Cl−secretion, in part via downregulation of CFTR and Na+-K+-ATPase activity and expression, but the proximal signaling events were unknown. We have shown that transforming growth factor-α (TGF-α) inhibits calcium-activated Cl−secretion, and effects of IFN-γ in other systems are mediated via EGF family members. We tested whether IFN-γ inhibits Cl−secretion via EGF receptor (EGFr) activation. IFN-γ increased tyrosine phosphorylation in T84 cells at 24 h, including the EGFr. IFN-γ also increased cell-associated pro-TGF-α, as well as free TGF-α in the bathing media. However, whereas IFN-γ significantly inhibited carbachol-induced Cl−secretion, neither neutralizing antibodies to TGF-α nor an EGFr inhibitor (1 μM tyrphostin AG 1478) were able to reverse this inhibitory effect. AG 1478 also failed to reverse IFN-γ-induced tyrosine phosphorylation of the EGFr, but receptor phosphorylation was attenuated by both the neutralizing antibody to TGF-α and PP2, a Src kinase inhibitor. Moreover, PP2 reversed the inhibitory effect of IFN-γ on Cl−secretion. In total, our findings suggest an increase in functional TGF-α and activation of the EGFr in response to IFN-γ. The release of TGF-α and intracellular Src activation likely combine to mediate EGFr phosphorylation, but only Src appears to contribute to the inhibition of transport. Nevertheless, because TGF-α plays a role in restitution and repair of the intestinal epithelium after injury, we speculate that these findings reflect a feedback loop whereby IFN-γ modulates the extent of cytokine-induced intestinal damage.
Expression and endocytosis of VEGF and its receptors in human colonic vascular endothelial cells
Authors: Wang Dongfang , Lehman Richard E. , Donner David B. , Matli Mary R. , Warren Robert S. , Welton Mark L.
Published: March 2015

Normal human colonic microvascular endothelial cells (HUCMEC) have been isolated from surgical specimens by their adherence to Ulex europaeus agglutinin bound to magnetic dynabeads that bind α-l-fucosyl residues on the endothelial cell membrane. Immunocytochemistry demonstrated the presence of a range of endothelial-specific markers on HUCMEC, including the von Willebrand factor, Ulex europaeus agglutinin, and platelet endothelial cell adhesion molecule-1. The growing cells form monolayers with the characteristic cobblestone morphology of endothelial cells and eventually form tube-like structures. HUCMEC produce vascular endothelial growth factor (VEGF) and express the receptors, kinase insert domain-containing receptor (KDR) and fms-like tyrosine kinase, through which VEGF mediates its actions in the endothelium. VEGF induces the tyrosine phosphorylation of KDR and a proliferative response from HUCMEC comparable to that elicited from human umbilical vein endothelial cells (HUVEC). On binding to HUCMEC or HUVEC,125I-labeled VEGF internalizes or dissociates to the medium. Once internalized,125I-labeled VEGF is degraded and no evidence of ligand recycling was observed. However, significantly less VEGF is internalized, and more is released to the medium from HUCMEC than HUVEC. Angiogenesis results from the proliferation and migration of microvascular, not large-vessel, endothelial cells. The demonstration that microvascular endothelial cells degrade less and release more VEGF to the medium than large-vessel endothelial cells identifies a mechanism permissive of the role of microvascular cells in angiogenesis.
Activation of human and mouse Kupffer cells by lipopolysaccharide is mediated by CD14
Authors: Su Grace L. , Goyert Sanna M. , Fan Ming-Hui , Aminlari Alireza , Gong Ke Qin , Klein Richard D. , Myc Andrzej , Alarcon William H. , Steinstraesser Lars , Remick Daniel G. , Wang Stewart C.
Published: March 2015

Upregulation of CD14 in Kupffer cells has been implicated in the pathogenesis of several forms of liver injury, including alcoholic liver disease. However, it remains unclear whether CD14 mediates lipopolysaccharide (LPS) signaling in this specialized liver macrophage population. In this series of experiments, we determined the role of CD14 in LPS activation of Kupffer cells by using several complementary approaches. First, we isolated Kupffer cells from human livers and studied the effects of anti-CD14 antibodies on LPS activation of these cells. Kupffer cells were incubated with increasing concentrations of LPS in the presence and absence of recombinant human LPS binding protein (LBP). With increasing concentrations of LPS, human Kupffer cell tumor necrosis factor-α (TNF-α) production (a marker for Kupffer cell activation) increased in a dose-dependent manner in the presence and absence of LBP. In the presence of anti-human CD14 antibodies, the production of TNF-α was significantly diminished. Second, we compared LPS activation of Kupffer cells isolated from wild-type and CD14 knockout mice. Kupffer cells from CD14 knockout mice produced significantly less TNF-α in response to the same amount of LPS. Together, these data strongly support a critical role for CD14 in Kupffer cell responses to LPS.
IV. Clinical and physiological aspects of gastrointestinal motility and aging
Authors: Orr William C. , Chen C. L.
Published: March 2015

The gastrointestinal motility changes that occur as a function of age are reviewed herein. Careful attention must be given in any review of aging phenomena to exclude, or at least be cognizant of, the many comorbid conditions that can alter physiological functioning in older adults. The dramatic increase in life expectancy over the past 10–15 years demands that clinicians be aware of the various physiological and clinically relevant changes that occur with age. Gastrointestinal motility changes associated with age are relatively subtle, and in many instances only conflicting data exist. As the older adult population increases, and as the control of disease is improved, much more work needs to be done to understand the true effects of aging on gastrointestinal functioning.
Role of luminal nutrients and endogenous GLP-2 in intestinal adaptation to mid-small bowel resection
Authors: Dahly Elizabeth M. , Gillingham Melanie B. , Guo Ziwen , Murali Sangita G. , Nelson David W. , Holst Jens J. , Ney Denise M.
Published: March 2015

To elucidate the role of luminal nutrients and glucagon-like peptide-2 (GLP-2) in intestinal adaptation, rats were subjected to 70% midjejunoileal resection or ileal transection and were maintained with total parenteral nutrition (TPN) or oral feeding. TPN rats showed small bowel mucosal hyperplasia at 8 h through 7 days after resection, demonstrating that exogenous luminal nutrients are not essential for resection-induced adaptation when residual ileum and colon are present. Increased enterocyte proliferation was a stronger determinant of resection-induced mucosal growth in orally fed animals, whereas decreased apoptosis showed a greater effect in TPN animals. Resection induced significant transient increases in plasma bioactive GLP-2 during TPN, whereas resection induced sustained increases in plasma GLP-2 during oral feeding. Resection-induced adaptive growth in TPN and orally fed rats was associated with a significant positive correlation between increases in plasma bioactive GLP-2 and proglucagon mRNA expression in the colon of TPN rats and ileum of orally fed rats. These data support a significant role for endogenous GLP-2 in the adaptive response to mid-small bowel resection in both TPN and orally fed rats.
cAMP modulation of Ca2+-regulated exocytosis in ACh-stimulated antral mucous cells of guinea pig
Authors: Nakahari Takashi , Fujiwara Shoko , Shimamoto Chikao , Kojima Kumiko , Katsu Ken-Ichi , Imai Yusuke
Published: March 2015

Effects of cAMP accumulation on ATP-dependent priming and Ca2+-dependent fusion in Ca2+-regulated exocytosis were examined in antral mucous cells of guinea pigs by using video-enhanced contrast microscopy. The Ca2+-regulated exocytosis activated by 1 μM ACh consisted of two phases, an initial transient phase followed by a sustained phase, which were potentiated by cAMP accumulation. Depletion of ATP by 100 μM dinitrophenol (uncoupler of oxidative phosphorylation) or anoxia induced the sustained phase without the initial transient phase in Ca2+-regulated exocytosis. However, accumulation of cAMP before depletion of ATP induced and potentiated an initial transient phase followed by a sustained phase in Ca2+-regulated exocytosis. This suggests that the initial transient phase of Ca2+-regulated exocytosis is induced by fusion of all primed granules maintained by ATP and that accumulation of cAMP accelerates ATP-dependent priming of the exocytotic cycle. Moreover, ACh and Ca2+ dose-response studies showed that accumulation of cAMP shifted the dose-response curves to the low concentration side, suggesting that it increases Ca2+ sensitivity in the fusion of the exocytotic cycle. In conclusion, cAMP accumulation increases the number of primed granules and Ca2+ sensitivity of the fusion, which potentiates Ca2+-regulated exocytosis in antral mucous cells.
Dopaminergic inhibition of secretin-stimulated choleresis by increased PKC-γ expression and decrease of PKA activity
Authors: Glaser Shannon , Alvaro Domenico , Roskams Tania , Phinizy Jo Lynne , Stoica George , Francis Heather , Ueno Yoshiyuki , Barbaro Barbara , Marzioni Marco , Mauldin Jeremy , Rashid Sobia , Mancino Maria Grazia , LeSage Gene , Alpini Gianfranco
Published: March 2015

To determine the role and mechanisms of action by which dopaminergic innervation modulates ductal secretion in bile duct-ligated rats, we determined the expression of D1, D2, and D3 dopaminergic receptors in cholangiocytes. We evaluated whether D1, D2 (quinelorane), or D3 dopaminergic receptor agonists influence basal and secretin-stimulated choleresis and lumen expansion in intrahepatic bile duct units (IBDU) and cAMP levels in cholangiocytes in the absence or presence of BAPTA-AM, chelerythrine, 1-(5-isoquinolinylsulfonyl)-2-methyl piperazine (H7), or rottlerin. We evaluated whether 1) quinelorane effects on ductal secretion were associated with increased expression of Ca2+-dependent PKC isoforms and 2) increased expression of PKC causes inhibition of PKA activity. Quinelorane inhibited secretin-stimulated choleresis in vivo and IBDU lumen space, cAMP levels, and PKA activity in cholangiocytes. The inhibitory effects of quinelorane on secretin-stimulated ductal secretion and PKA activity were blocked by BAPTA-AM, chelerythrine, and H7. Quinelorane effects on ductal secretion were associated with activation of the Ca2+-dependent PKC-γ but not other PKC isoforms. The dopaminergic nervous system counterregulates secretin-stimulated ductal secretion in experimental cholestasis.
Increased cytochromeP-450 2E1 expression sensitizes hepatocytes to c-Jun-mediated cell death from TNF-α
Authors: Liu Hailing , Jones Brett E. , Bradham Cynthia , Czaja Mark J.
Published: March 2015

The mechanisms underlying hepatocyte sensitization to tumor necrosis factor-α (TNF-α)-mediated cell death remain unclear. Increases in hepatocellular oxidant stress such as those that occur with hepatic overexpression of cytochrome P-450 2E1 (CYP2E1) may promote TNF-α death. TNF-α treatment of hepatocyte cell lines with differential CYP2E1 expression demonstrated that overexpression of CYP2E1 converted the hepatocyte TNF-α response from proliferation to apoptotic and necrotic cell death. Death occurred despite the presence of increased levels of nuclear factor-κB transcriptional activity and was associated with increased lipid peroxidation and GSH depletion. CYP2E1-overexpressing hepatocytes had increased basal and TNF-α-induced levels of c-Jun NH2-terminal kinase (JNK) activity, as well as prolonged JNK activation after TNF-α stimulation. Sensitization to TNF-α-induced cell death by CYP2E1 overexpression was inhibited by antioxidants or adenoviral expression of a dominant-negative c-Jun. Increased CYP2E1 expression sensitized hepatocytes to TNF-α toxicity mediated by c-Jun and overwhelming oxidative stress. The chronic increase in intracellular oxidant stress created by CYP2E1 overexpression may serve as a mechanism by which hepatocytes are sensitized to TNF-α toxicity in liver disease.
Intestinal inflammation modulates expression of the synaptic vesicle protein neuronal calcium sensor-1
Authors: Lourenssen S. , Jeromin A. , Roder J. , Blennerhassett M. G.
Published: March 2015

The calcium-binding protein neuronal calcium sensor 1 (NCS-1) is involved in modulation of neurotransmitter release in the peripheral and central nervous systems. Since intestinal inflammation impairs neurotransmitter release, we evaluated the expression of NCS-1 in the normal rat colon and in dinitrobenzene sulfonic acid (DNBS)-induced colitis. Immunocytochemistry and Western blots showed high levels of NCS-1 in the myenteric plexus and in axons in the smooth muscle layers; 23 ± 2% of myenteric neurons were NCS-1 positive, with staining restricted to the largest neurons. NCS-1-positive axons decreased to 13.3 ± 0.4% of total axons by day 2 and dropped further to 7.0 ± 0.1% by day 4, returning to control levels by day 16. Dual-label Western blot analysis showed that the expression of NCS-1 relative to PGP 9.5 decreased by 50% on day 4 but returned to control by day 16. The selective loss of NCS-1 during colitis may underlie the altered neural function seen in the inflamed intestine.