Education project for pathophysiology of gastrointestinal motility.
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Education, Medical, Continuing↗
Biomedical subjects
T Shea-Donohue
Publications and source records attributed to T Shea-Donohue.
A teaching module on cellular control of small intestinal motility.
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Animals↗
A teaching module on irritable bowel syndrome.
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Education, Medical↗
Changes in enteric neural circuitry and smooth muscle in the inflamed and infected gut.
Much of the morbidity associated with inflammatory bowel disease (IBD) and infection is caused by disordered gastrointestinal motor and secretory functions. Given that intestinal smooth muscle tone and epithelial cell secretion are regulated by the enteric nervous system (ENS), it is quite likely that inflammation-induced changes in the enteric neural circuitry contribute to intestinal dysmotility and diarrhoea. Indeed, discoveries over the past decades have demonstrated that gut inflammation and infections are associated with changes in key elements all along the enteric neural circuitry from the sensory transducers, the enterochromaffin (EC) cells, to the terminals of motor neurones.
Animals↗
Complement inhibitor, complement receptor 1-related gene/protein y-Ig attenuates intestinal damage after the onset of mesenteric ischemia/reperfusion injury in mice.
Complement receptor 1-related gene/protein y (Crry) is a murine membrane protein that regulates the activity of both classical and alternative complement pathways. We used a recombinant soluble form of Crry fused to the hinge, CH2, and CH3 domains of mouse IgG1 (Crry-Ig) to determine whether inhibition of complement activation prevents and/or reverses mesenteric ischemia/reperfusion-induced injury in mice. Mice were subjected to 30 min of ischemia, followed by 2 h of reperfusion. Crry-Ig was administered either 5 min before or 30 min after initiation of the reperfusion phase. Pretreatment with Crry-Ig reduced local intestinal mucosal injury and decreased generation of leukotriene B(4) (LTB(4)). When given 30 min after the beginning of the reperfusion phase, Crry-Ig resulted in a decrease in ischemia/reperfusion-induced intestinal mucosal injury comparable to that occurring when it was given 5 min before initiation of the reperfusion phase. The beneficial effect of Crry-Ig administered 30 min after the initiation of reperfusion coincided with a decrease in PGE(2) generation despite the fact that it did not prevent local infiltration of neutrophils and did not have a significant effect on LTB(4) production. These data suggest that complement inhibition protects animals from reperfusion-induced intestinal damage even if administered as late as 30 min into reperfusion and that the mechanism of protection is independent of neutrophil infiltration or LTB(4) inhibition.
Animals↗
The role of IL-4 in Heligmosomoides polygyrus-induced alterations in murine intestinal epithelial cell function.
IL-4 and IL-13 promote gastrointestinal worm expulsion, at least in part, through effects on nonlymphoid cells, such as intestinal epithelial cells. The role of IL-4/IL-13 in the regulation of intestinal epithelial function during Heligmosomoides polygyrus (Hp) infection was investigated in BALB/c mice infected with Hp or treated with a long-lasting formulation of recombinant mouse IL-4/alphaIL-4 complexes (IL-4C) for 7 days. Separate groups of BALB/c mice were drug-cured of initial infection and later reinfected and treated with anti-IL-4R mAb, an antagonist of IL-4 and IL-13 receptor binding, or with a control mAb. Segments of jejunum were mounted in Ussing chambers, and short circuit current responses to acetylcholine, histamine, serotonin, PGE2, and glucose were determined. Although only modest changes in epithelial cell function were observed during primary Hp infection, IL-4C or a secondary Hp infection each induced more dramatic changes, including increased mucosal permeability, reduced sodium-linked glucose absorption, and increased Cl- secretory response to PGE2. Some, but not all, effects of IL-4C and Hp infection were dependent on enteric nerves. Hp-induced changes in epithelial function were attenuated or prevented by anti-IL-4R mAb. Thus, IL-4/IL-13 mediate many of the effects of Hp infection on intestinal epithelial cell function and do so both through direct effects on epithelial cells and through indirect, enteric nerve-mediated prosecretory effects. These immune system-independent effector functions of IL-4/IL-13 may be important for host protection against gastrointestinal nematodes.
Animals↗
Alterations in spontaneous contractions in vitro after repeated inflammation of rat distal colon.
In inflammatory bowel disease, smooth muscle function reportedly varies with disease duration. The aim of these studies was to determine changes in the control of spontaneous contractions in a model of experimental colitis that included reinflammation of the healed area. The amplitude and frequency of spontaneous contractions in circular smooth muscle were determined after intrarectal administration of trinitrobenzenesulfonic acid in rat distal colon. With the use of a novel paradigm, rats were studied 4 h (acute) or 28 days (healed) after the initial inflammation. At 28 days, rats were studied 4 h after a second inflammation (reinflamed) of the colon. Colitis induced transient increases in the amplitude of spontaneous contractions coincident with a loss of nitric oxide synthase activity. The frequency of contractions was controlled by constitutive nitric oxide in controls. Frequency was increased in healed and reinflamed colon and was associated with a shift in the dominance of neural constitutive nitric oxide synthase control to that of inducible nitric oxide synthase (iNOS). The initial colitis induced a remodeling of the neural control of spontaneous contractions reflecting changes in their regulation by constitutive nitric oxide synthase and iNOS.
Animals↗
Pro- and anti-inflammatory gene expression in the murine small intestine and liver after chronic exposure to alcohol.
BACKGROUND: Endotoxin has been proposed to play a primary role in ALD, by initiating an inflammatory cascade within the liver. Although the source of these cytokines has been presumed to be circulating monocytes or tissue macrophages, ethanol-induced, nonhepatic sources of soluble mediators recently have been identified. One potential, but not clearly defined, extrahepatic source of cytokines in ALD is the intestine. In the current study, we hypothesized that alcohol would alter cytokine expression within the small intestine of mice exposed to ethanol and that LPS would alter levels of cytokine expression even more dramatically. METHODS: Mice were fed a modified Lieber-DeCarli liquid ethanol or control diet for up to 14 days prior to injecting either saline or LPS. Plasma alanine aminotransferase (ALT) and cytokine levels, histology, and RT-PCR of pro- and anti-inflammatory cytokine gene expression were determined from distal ileum and liver samples. Translocation of intestinal bacterial flora also was assessed. RESULTS: Ethanol exposure upregulated basal gene expression of IL-1 beta, TNF-alpha, IL-6, and iNOS in the distal ileum, but similar effects of ethanol on the liver were not observed. In contrast, LPS challenge of ethanol-exposed mice increased intestinal gene expression of some cytokines, but decreased expression of others. These effects were not associated with bacterial translocation. Also, ethanol alone induced a modest increase in both ICAM-1 and TLR4 mRNA expression in the intestine, but expression of both molecules was inhibited in mice that received both ethanol and LPS. Finally, whereas basal levels of hepatic IL-11 mRNA were not elevated by exposure to ethanol, intestinal IL-11 mRNA levels were increased more than 100-fold. CONCLUSIONS: These studies are the first to show that ethanol affects cytokine gene expression in the ileum and identifies the ileum as a potential target for ethanol effects. In addition, our results suggest that IL-11 expression may be enhanced in the intestine to help repair or protect this organ from alcohol-induced damage. Collectively, these studies suggest that both pro- and anti-inflammatory soluble mediators in the intestine maintain and exacerbate the local hepatic response to ethanol.
Alanine Transaminase↗
Colitis-induced alterations in adrenergic control of circular smooth muscle in vitro in rats.
The present study investigated inflammation-induced changes in adrenergic regulation of smooth muscle. Colitis was induced in rats by intrarectal administration of trinitrobenzenesulfonic acid in ethanol. After 4 h (acute) or 7 days (chronic), in vitro isometric tension was measured in strips of circular smooth muscle taken from the distal colon. In controls, the major inhibitory control of smooth muscle responses to nerve stimulation was mediated by nitric oxide and beta adrenergic receptors. There was less evidence of alpha adrenergic control. Studies with the beta3 receptor antagonist cyanopindolol and the beta3 receptor agonist BRL37344 revealed that beta adrenergic regulation of spontaneous contractions and responses to nerve stimulation were mediated primarily by the beta3 adrenoreceptor. Both acute and chronic colitis significantly increased responses to electrical field stimulation. This effect was attributed to a loss of inhibitory nitrergic regulation as well as to selective changes in the beta adrenergic control of colonic circular smooth muscle. Inflammation did not alter alpha adrenergic control. Chronic colitis also decreased the sensitivity to nerve stimulation and pharmacological contractile agents. Acute and chronic inflammation reduced the ability of BRL37344 to inhibit contractions in response to nerve stimulation. In addition, in inflamed colon, BRL37344 was less effective in relaxing carbachol-induced precontractions. Finally, inflammation resulted in a loss of the ability of the cyanopindolol to increase the amplitude of both spontaneous contractions and contractions in response to nerve stimulation. These effects indicated that colitis induced a down-regulation of inhibitory beta3 adrenergic control of colonic smooth muscle function. This loss of adrenergic regulation may contribute to the diarrhea in inflammatory bowel disease.
Adrenergic Agonists↗
Sustained nitric oxide production via l-arginine administration ameliorates effects of intestinal ischemia-reperfusion.
BACKGROUND: The role of nitric oxide in intestinal ischemia-reperfusion is unclear-some studies link it to the harmful effects of ischemia-reperfusion, while others report it to be protective. We propose that nitric oxide levels diminish in the reperfusion period in conjunction with the onset of increased capillary permeability. The aim of this study is to determine the effect of supplementing nitric oxide synthase with its substrate, l-arginine, on development of local mucosal injury and systemic capillary leak. MATERIALS AND METHODS: Rats underwent 30 min of superior mesenteric artery occlusion followed by 4 h of reperfusion. The vehicle groups received l-arginine either intravenously (4 mg/kg/min) or into the intestinal lumen. The intravenous groups received l-arginine either before the ischemic event or after 30 min of reperfusion. Capillary leak in the gut and lung were measured, as were degree of mucosal injury and number of infiltrating neutrophils. Appropriate controls were performed. RESULTS: Thirty minutes of mesenteric ischemia followed by 4 h of reperfusion significantly increased gut and lung leak, neutrophil infiltration, and the severity of mucosal injury. l-Arginine given iv prior to ischemia inhibited lung leak, mucosal injury, and neutrophil infiltration. When arginine was given during the reperfusion period, lung leak and neutrophil infiltration but not mucosal injury were reduced. Intraluminal l-arginine reduced mucosa injury, but had no effect on capillary leak. CONCLUSIONS: Supplementation with l-arginine enhances NO production, resulting in reduced systemic endothelial dysfunction. This may act as a useful clinical adjunct in the management of trauma patients in preventing the development of ARDS and multiple organ failure.
Animals↗
Neutrophil priming state predicts capillary leak after gut ischemia in rats.
BACKGROUND: Multiple organ failure after serious injury or illness is a major determinant of mortality. An initial insult is believed to "prime" circulating neutrophils and induce systemic inflammation. Thereafter, a second insult will precipitate distant organ injury. The aim of these studies was to evaluate circulating neutrophil function after mesenteric ischemia-reperfusion to determine the neutrophil "priming state," a quantitative and clinically useful predictor of multiple organ failure. MATERIALS AND METHODS: Anesthetized Sprague-Dawley rats underwent superior mesenteric artery occlusion for 30 min or sham operation and were euthanized after 2, 6, or 24 h of reperfusion. Control animals had blood taken without any intervention. To determine changes in lung capillary permeability, another group of rats received Evan's blue, a dye that binds albumin, 1 h before sacrifice. Flow cytometric analysis was performed on 5 million white blood cells after removal of red cells by lysis and centrifugation. Neutrophil number, oxidative burst, and CD18 expression were measured. RESULTS: The number of circulating neutrophils was elevated similarly in rats subjected to sham operation or ischemia-reperfusion. Oxidative burst potential was increased at 2 h, maximum at 6 h, and normal at 24 h after reperfusion, but not in sham rats. CD18 expression was similar in all groups. There was a significant temporal correlation between the "priming state" of the circulating neutrophil, defined as the product of the neutrophil number times oxidative burst, and lung leak. CONCLUSIONS: The neutrophil "priming state" may allow the clinician to better predict those patients at greatest risk for multiple organ failure.
Animals↗
Antiinflammatory effects of soluble complement receptor type 1 promote rapid recovery of ischemia/reperfusion injury in rat small intestine.
We examined the effect of soluble complement receptor type 1 (sCR1) on mucosal injury and inflammation in a rat model of ischemia/reperfusion. Groups of vehicle- and sCR1-treated rats underwent 30 min of mesenteric ischemia followed by 60 or 120 min of reperfusion. When compared to vehicle-treated rats, treatment with sCR1 (12 mg/kg) prior to 120 min of reperfusion significantly reduced mucosal injury, neutrophil infiltration, leukotriene B4 production, and restored villus height to control levels. The protective effect of sCR1 evident at 120 min of reperfusion was not observed at 60 min of reperfusion despite rapid inactivation of complement. These data suggest that complement inhibition minimized mucosal disruption by facilitating mucosal restitution or interrupting the inflammatory process. Delayed administration of sCR1 for 30 or 60 min into the reperfusion period progressively reduced the protection. sCR1-mediated rapid recovery of rat intestine after ischemia/reperfusion underscores the fundamental role of complement activation in neutrophil-mediated tissue injury.
Animals↗
Ischemia-reperfusion protects the rat small intestine against subsequent injury.
BACKGROUND: It has been suggested that multiple sublethal insults are commonly associated with the development of multiple organ failure (MOF). The gut is considered to be pivotal in the pathogenesis of MOF. This study investigated the effects of repeated ischemia-reperfusion of the rat small intestine. METHODS: Groups of rats underwent 30 min of superior mesenteric artery occlusion or sham operation followed by 24 h of reperfusion. They then received an additional 30 min of superior mesenteric artery occlusion and 2 h of reperfusion or sham operation. Small intestine was examined for mucosal injury, neutrophil infiltration, goblet cell number, and generation of the eicosanoids, prostaglandin E2, and leukotriene B4. Activation of neutrophils was assessed in systemic venous blood. RESULTS: Animals subjected to two insults of ischemia-reperfusion demonstrated significantly less mucosal injury than animals undergoing one episode of ischemia and 2 h of reperfusion, despite increased neutrophil infiltration, leukotriene B4, and activated systemic neutrophils. Goblet cell number was elevated in animals 24 h after the first ischemia-reperfusion insult and remained enhanced after the second episode of ischemia-reperfusion. CONCLUSIONS: The initial episode of ischemia-reperfusion caused an adaptive response associated with cytoarchitectural preservation following the subsequent insult. Increased mucus production was associated with mucosal protection. Nevertheless, repeated ischemia-reperfusion potentiated the local inflammatory response and the systemic activation of neutrophils.
Animals↗
Hyperthermia prevents functional, histological and biochemical abnormalities induced during ileitis.
Inflammatory bowel disease is associated with altered intestinal motility and epithelial damage. Hyperthermia induces heat shock protein expression, components of a basic cellular defence mechanism, and consequently prevents ischaemic damage. Here we investigate whether hyperthermia may prevent altered smooth muscle function as well as underlying inflammation in a model of inflammatory bowel disease. Ileal heat shock protein expression was induced in rats by hyperthermic shock (41.5 degrees C; 5 min). Two hours after heating or sham treatment, ileitis was evoked by TNBS. Ileal samples were taken 4 h later to determine the contractile response of circular muscle strips, and to measure heat shock protein expression, LTB4 generation and damage/inflammation. Ileitis was associated with an increase in the contractile response of circular muscle to substance P but not neurokinin A or nerve stimulation. Hyperthermia induced heat shock protein expression and also prevented this functional change as well as TNBS-induced LTB4 production, subsequent infiltration of neutrophils and epithelial damage. Thus, intestinal inflammation is associated with alterations in tachykinergic control of smooth muscle as well as inflammatory changes. Hyperthermia prevents these changes and induces heat shock protein expression. Pharmacological induction of these proteins may offer a novel clinical strategy in treating both of these aspects of disease.
Animals↗
Progressive alterations in circular smooth muscle contractility in TNBS-induced colitis in rats.
The present study was designed to investigate inflammation-induced changes in smooth muscle responses to acetylcholine and the tachykinins that may contribute to the abnormal motility associated with inflammatory bowel disease. Colitis was induced in male Sprague-Dawley rats by intrarectal administration of trinitrobenzenesulphonic acid in ethanol. After either 4 h (acute) or 7 days (chronic) the distal colon was taken for in vitro measurement of smooth muscle tension and histological assessment. Acute colitis featured injury and neutrophilic infiltration confined to the mucosa while chronic inflammation showed marked injury, lymphocytic infiltration and muscle thickening. Acute inflammation increased responses to substance P and acetylcholine but decreased responses to neurokinin A. The enhanced response to substance P was dependent on nerves, while the decreased response to neurokinin A reflected a reduction in activity at the level of the smooth muscle. In the saline group, there was evidence of cholinergic interaction with substance P, but not neurokinin A. Substance P modulation of cholinergic nerves was absent in acute inflammation. Responses to all neurotransmitters were decreased in the chronic stage. These data demonstrate progressive changes in the smooth muscle function during acute and chronic colitis that may contribute to the abnormal motility associated with inflammatory bowel disease.
Acetylcholine↗
Anti-inflammatory effects of U74389F in a rat model of intestinal ischemia/reperfusion injury.
OBJECTIVE: To investigate the role of eicosanoid generation and neutrophilic infiltration in the protective effects of U74389F against ischemia/reperfusion injury in the small intestines of rats. DESIGN: Prospective, randomized, controlled study. SETTING: University research laboratory. SUBJECTS: Adult, male Sprague-Dawley rats weighing between 200 and 300 g. INTERVENTIONS: Groups (5-8) of rats treated with U74389F or vehicle were subjected to a sham operation and 30 mins of ischemia by occlusion of the superior mesenteric artery or 30 mins of ischemia followed by 60 or 120 mins of reperfusion. U74389F (2.5 mg/kg i.v.) or vehicle (citrate buffer) were slowly injected 2 mins before ischemia. MEASUREMENTS AND MAIN RESULTS: Ischemia significantly (p < .05) increased mucosal injury (0 [normal] to 5) in both U74389F and untreated rats. In contrast, U74389F significantly (p < .05) attenuated the severity of injury after reperfusion. In vehicle-treated rats, ischemia/reperfusion significantly reduced villus height in both U74389F and untreated groups. However, the surface epithelial layer was intact in the U74389F but not in the vehicle-treated group. In addition, compared with the vehicle-treated group, U74389F significantly reduced neutrophil infiltration and prevented the increase in leukotriene B4 and prostaglandin E2 in response to ischemia and reperfusion. CONCLUSIONS: This study demonstrates that the mechanism of U74389F against mesenteric ischemia/reperfusion includes a delay and reduction of neutrophilic infiltrate, an inhibition of leukotriene B4 production, and a facilitation of mucosal restitution.
Animals↗
Nitric oxide mediates acute lung injury by modulation of inflammation.
Nitric Oxide's (NO) function in vasomotor control, inflammation, and signal transduction makes it an attractive potential mediator of the capillary leak seen in acute lung injury. Despite extensive study, the role of NO in intestinal ischemia/reperfusion-induced capillary leak remains controversial. Rats were treated with vehicle, norepinephrine, or L-NNA (nitric oxide synthase inhibitor) and then underwent sham laparotomy or 30 min SMA occlusion followed by 1 to 12 h of reperfusion. Evan's Blue dye was administered 1 h before animals were euthanized. Ratios of bronchoalveolar lavage or small-intestine lavage to serum dye concentrations were calculated as measures of capillary leak. Circulating neutrophil activation was measured with a nitroblue tetrazolium reduction assay. In vehicle-treated animals, both capillary leakage and PMN activation peaked at 4 h of reperfusion. These parameters returned to baseline by 12 h. Treatment with L-NNA accelerated ischemia/reperfusion-induced PMN activation as well as accelerated capillary leak from 4 to 1 h. Treatment with norepinephrine (hypertensive control) increased the magnitude of lung capillary leak but had no effect on the timing of ischemia/reperfusion-induced PMN activation or ischemia/reperfusion-induced capillary leak. These data show that intestinal ischemia/reperfusion-induced systemic capillary leak is associated with systemic neutrophil activation. Nitric oxide synthase inhibition accelerates ischemia/reperfusion-induced capillary leak and mediates the capillary leak seen in acute lung injury by modulating neutrophil activation.
Acute Disease↗
Induction of the heat shock response prevents tissue injury during acute inflammation of the rat ileum.
OBJECTIVES: To determine if prior total body hyperthermia protected against subsequent acute ileitis induced by the cytotoxic lectin, ricin, in rats. The time course of heat shock mRNA and protein expression in the ileum was determined. The effects of heat stress on small intestinal mucosal integrity, arachidonic acid metabolism, and neutrophilic infiltrate were compared in heated and nonheated rats receiving vehicle or ricin intraluminally. The effect of hyperthermia on the circulating neutrophil superoxide production was also evaluated. DESIGN: Prospective, randomized, controlled trial. SETTING: University research laboratory. SUBJECTS: Forty-one adult, male Sprague-Dawley rats, weighing 150 to 250 g, and 32 adult, inbred, male Fisher 344 rats, weighing 175 to 250 g. INTERVENTIONS: Exposure to whole body hyperthermia and production of acute ileitis. Sprague-Dawley rats were divided randomly into four experimental groups: nonheated control group, heated control group, nonheated ricin group (1 mg/mL water, intraluminal), and heated ricin group. Sprague-Dawley rats in a separate study were assigned to seven groups based on the time of removal of the terminal ileum following hyperthermia: 0 min, or 1, 2, 4, 8, 12, and 24 hrs. Inbred Fisher 344 rats were allocated to the heated and nonheated groups for peripheral neutrophil superoxide generation studies. MEASUREMENTS AND MAIN RESULTS: Whole body hyperthermia to a rectal temperature of 41 degrees C to 42 degrees C for 15 to 20 mins: a) was associated with marked mucosal cytoprotection against subsequent ricin-induced ileitis (Injury grade [from 0 = normal to 5 = severe]: 0.4 +/- 0.1 vs. 2.5 +/- 0.2, p < .001); b) prevented the ricin-induced reduction in villus height to crypt depth ratio (2.4 +/- 0.1 vs. 1.9 +/- 0.1, p < .01); and c) significantly reduced the number of infiltrating neutrophils when compared with nonheated ricin-treated rats (11 +/- 2 vs. 32 +/- 3 neutrophils/high-power field, p < .001). The hyperthermia-induced peak increase in heat shock protein (HSP)-70 mRNA at 2 hrs preceded that of HSP 70i at 4 hrs. Heat shock significantly reduced the ricin-induced increase in both basal (8.0 +/- 1.9 vs. 33.0 +/- 8.1 pg of leukotriene B4/mg protein, p < .05) and ionophore-stimulated (16.0 +/- 4.9 vs. 80.0 +/- 15.5 pg of leukotriene B4/mg protein, p < .001) generation of ileal leukotriene B4, but did not alter the cyclooxygenase product, prostaglandin E2. Hyperthermia did not alter peripheral neutrophil superoxide production. CONCLUSIONS: This study assessed the effects of heat shock in the normal and acutely inflamed intestine. These data suggest that heat stress and increased expression of HSP 70i protect against acute intestinal inflammation. This protection is associated with significant reductions in ileal leukotriene B4 generation and neutrophilic infiltrate. Hyperthermia did not alter circulating neutrophil superoxide production. Thus, the mechanism of heat stress protection against acute ileitis may involve local intestinal inhibition of leukotriene B4 production and subsequent neutrophilic infiltration without altering the ability of systemic neutrophils to be activated.
Animals↗