Biomedical subjects

M H Perdue

Publications and source records attributed to M H Perdue.

At least 37 records · Page 2Linked to original sources

PubMed1999

Role for IL-4 in macromolecular transport across human intestinal epithelium.

Increased epithelial permeability is associated with intestinal inflammation, but there is little information on factors that regulate barrier function in the absence of or before inflammation. We examined if interleukin (IL)-4, or serum from atopic individuals, could alter the barrier function of human colonic epithelial (T84) monolayers to antigenic-sized macromolecules. IL-4 and atopic serum significantly decreased T84 monolayer resistance and increased transepithelial horseradish peroxidase (HRP) transport. Bidirectional transport studies demonstrated that IL-4 selectively enhanced apical-to-basal movement of HRP. HRP transport induced by IL-4 was inhibited by cold (4 degrees C) and the tyrosine kinase inhibitor genistein, but not the protein kinase C inhibitor staurosporine. Electron microscopic analysis demonstrated that both transcellular and paracellular pathways were affected. Anti-IL-4 antibodies abolished the increase in HRP transport in response to both IL-4 and serum. We speculate that enhanced production of IL-4 in allergic conditions may be a predisposing factor to inflammation by allowing uptake of luminal antigens that gain access to the mucosal immune system.

Adult↗

PubMed1999

Mucosal immunity and inflammation. III. The mucosal antigen barrier: cross talk with mucosal cytokines.

We have known for many years that mucosal responses to antigens are regulated by immune cells and their molecular signals. More recently, it has become clear that epithelial cells also synthesize and secrete chemokines and cytokines. A sophisticated system of bidirectional cytokine signals is responsible for immune activation in the case of enteropathogens vs. immune suppression to food and commensal microbial antigens. A key factor in determining antigen handling is the route taken by antigens across the epithelial barrier. Cytokines and other mucosal messenger molecules play a critical role in the regulation of transepithelial antigen transport.

Animals↗

PubMed1999

Corticotropin-releasing hormone mimics stress-induced colonic epithelial pathophysiology in the rat.

We examined the effect of stress on colonic epithelial physiology, the role of corticotropin-releasing hormone (CRH), and the pathways involved. Rats were restrained or injected intraperitoneally with CRH or saline. Colonic segments were mounted in Ussing chambers, in which ion secretion and permeability (conductance and probe fluxes) were measured. To test the pathways involved in CRH-induced changes, rats were pretreated with hexamethonium, atropine, bretylium, doxantrazole, alpha-helical CRH-(9-41) (all intraperitoneally), or aminoglutethimide (subcutaneously). Restraint stress increased colonic ion secretion and permeability to ions, the bacterial peptide FMLP, and horseradish peroxidase (HRP). These changes were prevented by alpha-helical CRH-(9-41) and mimicked by CRH (50 microgram/kg). CRH-induced changes in ion secretion were abolished by alpha-helical CRH-(9-41), hexamethonium, atropine, or doxantrazole. CRH-stimulated conductance was significantly inhibited by alpha-helical CRH-(9-41), hexamethonium, bretylium, or doxantrazole. CRH-induced enhancement of HRP flux was significantly reduced by all drugs but aminoglutethimide. Peripheral CRH reproduced stress-induced colonic epithelial pathophysiology via cholinergic and adrenergic nerves and mast cells. Modulation of stress responses may be relevant to the management of colonic disorders.

Animals↗

PubMed1999

Pertussis adjuvant prolongs intestinal hypersensitivity.

BACKGROUND: Immediate hypersensitivity reactions are a hallmark of allergic disease, and result in the clinical features of food allergy, hayfever, and atopic asthma. The mechanism by which an individual becomes sensitized to an ingested or airborne allergen is not clear, however exposure to bacteria or bacterial products that act as adjuvants may be a contributing factor. The purpose of this study was to examine the role of pertussis toxin (PT) in inducing intestinal hypersensitivity reactions, particularly the ability of the adjuvant to prolong the sensitization. METHODS: Rats were sensitized to ovalbumin (OA) by injection of OA alone or with 50 ng PT. Secretory responses to OA challenge and nerve stimulation were assessed in jejunal tissues mounted in Ussing chambers. RESULTS: Jejunal segments from rats sensitized to OA alone responded to antigen challenge with ion secretion, but sensitization was transient in that specific IgE titers and responses to luminal antigen disappeared by 14 days. In contrast, co-administration of 50 ng PT with OA resulted in long-lasting sensitization. Secretory responses to both luminal and serosal OA challenge were present 8 months after primary immunization. Enhanced secretory responses to nerve stimulation, increased mucosal mast cell numbers, as well as elevated IgE titers were also induced and may have contributed to the overall responsiveness of the intestine to antigen challenge. CONCLUSIONS: Our findings indicate nanogram quantities of PT, when administered with a food protein, result in long-term sensitization to the antigen, and altered intestinal neuroimmune function. These data suggest that exposure to bacterial pathogens may prolong the normally transient immune responsiveness to inert food antigens.

Adjuvants, Immunologic↗

PubMed1999

Immune-epithelial interactions in host defense.

Over the past 15 years, it has become very clear that the immune system can have profound effects on epithelial function. Acute immune-mediated changes in epithelial physiology are beneficial to host defense against enteric pathogens. For example, ion secretion washes out noxious luminal contents and increased permeability allows phagocytic cells and antibodies to enter the gut lumen. However, ongoing immune activation results in chronic effects that may be pathophysiologic. Responses are mediated by soluble immune mediators that act directly on the epithelium, or indirectly via nerves that also serve to amplify the epithelial response. Here, we will review some of the recent advances that have been made in the field of immunophysiology. The effect of mast cells on transport functions of the epithelium will be reviewed, with emphasis on the consequence of interactions between mast cells and nerves. The use of in vitro coculture systems has recently provided considerable information on the effects of neutrophils, eosinophils, monocytes, and lymphocytes on epithelial functions; the contribution of each immunocyte will be highlighted. Finally, we will describe evidence for the active participation of the epithelium in mucosal immune activation, including pathogen or cytokine induced epithelial cytokine synthesis or secretion and adhesion molecule expression.

Animals↗

PubMed1999

Improved effects of novel glucocorticosteroids on immune-induced epithelial pathophysiology.

Glucocorticosteroids are a mainstay therapy in inflammatory bowel disease and other chronic inflammatory conditions. However, severe systemic side effects are associated with their long-term use. The new generation of glucocorticosteroids have a high degree of topical activity with reduced systemic effects due to rapid metabolism. We previously described an in vitro model of inflammation in which monolayers of the human T84 colonic epithelial cell line displayed altered ion secretion and increased permeability after coculture with endotoxin-activated monocytes/macrophages (MPhi). Here, we tested the effects of budesonide and two novel analogs, D5519 and S1316, on MPhi-induced epithelial changes. Filter-grown T84 monolayers were cocultured with activated MPhi and single daily doses of drug were added to the luminal (physiological) side of the monolayer. Basal and stimulated epithelial ion transport [baseline short-circuit current (Isc) and DeltaIsc to forskolin, respectively] and barrier (transepithelial resistance) parameters were measured 48 h later in Ussing chambers. D5519, S1316, and budesonide (10(-7) to 10(-9) M) dose dependently inhibited the MPhi-induced epithelial abnormalities, restoring normal resistance, decreasing the elevated baseline Isc, and improving the reduced Isc response to forskolin. Of the drugs tested, D5519 was consistently the most potent and effective in inhibiting the MPhi-induced epithelial irregularities. Coupled with a further improvement in their rate of hepatic inactivation, our findings indicate that the novel steroids, particularly D5519, will be a valuable addition to current treatment strategies for inflammatory bowel disease and other chronic inflammatory conditions.

Budesonide↗

PubMed1998

The influence of mast cells on pathways of transepithelial antigen transport in rat intestine.

Luminal Ag challenge of intestinal segments from sensitized rats results in a rapid (approximately 3 min) secretory response. We previously showed in horseradish peroxidase (HRP)-sensitized rats that the initial phase of transepithelial Ag transport occurred via a transcellular route and was enhanced by sensitization. However, following the hypersensitivity reaction, Ag also crossed between epithelial cells. The aim of this study was to determine the role of mast cells in the altered transepithelial Ag transport. White spotting mast cell-deficient rats and +/+ littermate controls were sensitized to HRP. After 10 to 14 days, jejunal segments were resected, mounted in Ussing chambers, and challenged with HRP on the luminal side. Electron microscopy of jejunum fixed at 2 min showed a similarly enhanced endocytic transport of HRP in sensitized +/+ and Ws/Ws rats compared with naive controls. In sensitized +/+ rats, a secretory response occurred approximately 3 min after challenge, and tissue conductance increased thereafter. Naive +/+ and sensitized Ws/Ws rats did not demonstrate a secretory response to HRP challenge, and conductance remained at baseline levels. The flux of HRP was elevated across tissue from sensitized +/+ rats but not across tissue from naive controls or sensitized Ws/Ws rats. The results indicate that sensitization enhances the initial phase of transepithelial uptake of Ag by transcytosis in a mast cell-independent manner. However, subsequent recruitment of the paracellular pathway for Ag transport in sensitized rats is dependent upon the presence of mast cells and occurs after the activation of such cells.

Animals↗

PubMed1998

Signal transduction pathways involved in enterohemorrhagic Escherichia coli-induced alterations in T84 epithelial permeability.

Enterohemorrhagic Escherichia coli (EHEC) infection is associated with watery diarrhea and can lead to complications, including hemorrhagic colitis and the hemolytic-uremic syndrome. The mechanisms by which these organisms produce diarrheal disease remain to be elucidated. Changes in T84 epithelial cell electrophysiology were examined following EHEC infection. T84 cell monolayers infected with EHEC O157:H7 displayed a time-dependent decrease in transepithelial resistance. Increases in the transepithelial flux of both [3H]mannitol and 51Cr-EDTA accompanied the EHEC-induced decreases in T84 resistance. Altered barrier function induced by EHEC occurred at the level of the tight junction since immunofluorescent staining of the tight-junction-associated protein ZO-1 was disrupted when examined by confocal microscopy. Decreased resistance induced by EHEC involved a protein kinase C (PKC)-dependent pathway as the highly specific PKC inhibitor, CGP41251, abrogated the EHEC-induced drop in resistance. PKC activity was also increased in T84 cells infected with EHEC. Calmodulin and myosin light chain kinase played a role in EHEC-induced resistance changes as inhibition of these effector molecules partially reversed the effects of EHEC on barrier function. These studies demonstrate that intracellular signal transduction pathways activated following EHEC infection link the increases in T84 epithelial permeability induced by this pathogen.

Calmodulin↗

PubMed1998

Monocyte/macrophages evoke epithelial dysfunction: indirect role of tumor necrosis factor-alpha.

We examined the ability of monocytes (MPhi) activated by bacterial products to alter epithelial physiology. Confluent monolayers of the T84 colonic epithelial cell line were grown on filter supports and then cocultured in the presence of human MPhi with or without the activating agents bacterial lipopolysaccharide and the bacterial tripeptide formyl-methionyl-leucyl-phenylalanine. After 24 or 48 h, monolayers were mounted in Ussing chambers where parameters of epithelial function were measured. Exposure to activated MPhi resulted in a significant increase (P < 0.05) in baseline short-circuit current (250% after 48 h) that was associated with enhanced secretion of Cl-. In addition, epithelial permeability was significantly increased as shown by reduced transepithelial resistance and increased flux of 51Cr-EDTA. Activated MPhi produced substantial amounts (approximately 3 ng/ml at 48 h) of tumor necrosis factor-alpha (TNF-alpha). TNF-alpha was identified as a key mediator acting via an autocrine mechanism to induce epithelial pathophysiology. Our data show that MPhi, when activated by common bacterial components, are potent effector cells capable of initiating significant changes in the transport and barrier properties of a model epithelium.

Adult↗

PubMed1998

Stress stimulates transepithelial macromolecular uptake in rat jejunum.

Evidence suggests that stress may be a contributing factor in intestinal inflammatory disease; however, the involved mechanisms have not been elucidated. We previously reported that acute stress alters epithelial physiology of rat intestine. In this study, we documented stress-induced macromolecular transport across intestinal epithelium. After exposure of Wistar-Kyoto rats to acute restraint stress, transport of a model protein, horseradish peroxidase (HRP), was assessed in isolated segments of jejunum. The flux of intact HRP was significantly enhanced across intestine from stressed rats compared with controls. Electron microscopy revealed HRP-containing endosomes within enterocytes, goblet cells, and Paneth cells of stressed rats. The number and area of HRP endosomes within enterocytes were found to be significantly increased by stress. HRP was also visualized in paracellular spaces between adjacent epithelial cells only in intestine from stressed rats. Atropine treatment of rats prevented the stress-induced abnormalities of protein transport. Our results suggest that stress, via a mechanism that involves release of acetylcholine, causes epithelial dysfunction that includes enhanced uptake of macromolecular protein antigens. We speculate that immune reactions to such foreign proteins may initiate or exacerbate inflammation.

Animals↗

PubMed1998

Epithelial ion transport and barrier abnormalities evoked by superantigen-activated immune cells are inhibited by interleukin-10 but not interleukin-4.

Many studies have indicated an association between bacteria and the severity of enteric secretory or inflammatory disorders. We previously showed that monolayers of human T84 epithelial cells display altered ion transport and permeability after coculture with Staphylococcus aureus enterotoxin B (SEB, a model superantigen)-activated immune cells, where interferon-gamma and tumor necrosis factor-alpha were key mediators in the pathophysiology. Here we examined whether the regulatory Th2-type cytokines, interleukin (IL)-10 and IL-4, could prevent these epithelial irregularities. T84 monolayers were cocultured with human peripheral blood mononuclear cells (PBMC) or T cell-enriched, monocyte-depleted PBMC (T + B cells) +/- SEB for 20 hr in the presence or absence of IL-10 or IL-4. Subsequently, T84 monolayers were mounted in Ussing chambers and ion transport (short-circuit current (Isc) and DeltaIsc evoked by forskolin) and permeability (ion resistance and probe fluxes) were assessed. IL-10 dose-dependently inhibited the increased T84 permeability and the reduced responsiveness to forskolin that were evoked by coculture with SEB-activated PBMC or T + B cells. Similar changes in T84 function occurred in response to conditioned medium from SEB-activated immune cells; however, addition of IL-10 to the conditioned medium did not prevent the changes in epithelial function. In contrast, when PBMC were stimulated with SEB in the presence of IL-10, the subsequent conditioned medium was less effective in evoking altered epithelial function. These data suggest that the affect of IL-10 was due to effects on the immune cells and not directly on the epithelium. In contrast to IL-10, IL-4 did not ameliorate any of the immune-mediated changes in T84 function. We conclude that IL-10 can reduce the epithelial functional changes caused by SEB-activated immune cells and this data adds further support for IL-10 immunotherapy in the treatment of intestinal secretory or inflammatory disorders.

Cell Line↗

PubMed1997

Rapid transepithelial antigen transport in rat jejunum: impact of sensitization and the hypersensitivity reaction.

BACKGROUND & AIMS: Intestine from sensitized rats develops a rapid secretory response to luminal antigen challenge that depends on activation of subepithelial mast cells. The aim of this study was to determine the timing and route of the transepithelial protein antigen transport. METHODS: Rats were sensitized to horseradish peroxidase (HRP). After 10-14 days, jejunal segments were resected, mounted in Ussing chambers, and challenged with HRP on the luminal side. RESULTS: Electron microscopy of tissue specimens fixed at 2 minutes (before mast cell activation) showed enhanced endocytic uptake of HRP in enterocytes of HRP-sensitized rats compared with ovalbumin-sensitized or saline-injected controls. At this time, HRP was distributed throughout epithelial cells and was already evident in the lamina propria. In contrast, HRP was restricted to the apical region of enterocytes in controls. At 30 minutes (after mast cell activation), in HRP-sensitized rats only, HRP was also located within tight junctions and the paracellular region between epithelial cells. Tissue conductance was increased in HRP-sensitized rats beginning 30 minutes after HRP addition and correlated with the overall flux of HRP across the tissue. CONCLUSIONS: The results show that specific sensitization enhances the initial uptake and transcytosis of antigen across intestinal epithelium. Subsequent to activation of mast cells, antigen transport is further enhanced by penetration through the paracellular pathway.

Animals↗

PubMed1997

Review article: In vitro models in inflammatory bowel disease research--a critical review.

Research efforts in inflammatory bowel disease (IBD) have been directed towards the epithelium as it has become clear that epithelial cells play a critical role in inflammatory response. Most research involving IBD employs in vitro techniques. In vitro epithelial cell studies have played and are continuing to play a major role in providing specific information relevant to IBD. Thus, such studies have provided irrefutable evidence that epithelial responses can be induced by microbes/microbial products and by immune activation. Culture experiments have provided insights into the effects of individual cytokines and other inflammatory mediators on epithelial pathophysiology, injury and repair, apoptosis, necrosis, and other processes that may be involved in IBD. Activated epithelial cells can participate in and even orchestrate immune responses, by stimulating T cells (and possibly others) and by producing cytokines that recruit specific inflammatory cells. Physiological regulation of epithelial tight junctions has been demonstrated by in vitro studies; the implication of this information for treating IBD is just beginning to be explored. It is becoming increasingly clear that epithelial processing and presentation of antigens is critical to the outcome of the immune response.

Animals↗

PubMed1997

Mast cell mediated ion transport in intestine from patients with and without inflammatory bowel disease.

BACKGROUND: Mast cells have been shown to regulate intestinal ion transport in animal models and normal human colon but their physiological role in human intestinal inflammatory disorders is unknown. AIMS: To examine mast cell regulation of ion transport in inflammatory bowel disease (IBD). SUBJECTS AND METHODS: Small and large intestine was obtained from patients with and without IBD undergoing surgical resection. Short circuit current (Isc) responses to rabbit antihuman IgE, histamine, and electrical stimulation were measured in Ussing chambers. Specimens were also examined for mast cell numbers and degree of inflammation. RESULTS: Isc responses to anti-IgE and histamine were smaller in magnitude in IBD compared with non-IBD tissues. In all tissues, anti-IgE Isc responses were reduced by about 80% in chloride free buffer. The histamine H1 receptor antagonist, pyrilamine, decreased anti-IgE responses in non-IBD tissues. Greater inhibition with pyrilamine was seen in IBD small intestine but its effect was less in IBD colon. Histamine pretreatment of non-IBD control tissues reduced anti-IgE responses to levels seen in IBD colon but had no effect in small intestine. Mast cell numbers were greater in IBD compared with non-IBD small intestine while no differences were observed between the colonic groups. Isc responses to anti-IgE were not correlated with the degree of mucosal inflammation. CONCLUSIONS: This study provides further evidence that mast cells are capable of mediating alterations of ion transport in human gut but that this regulatory role may be altered in IBD. The data suggest that prior activation of mast cells with release of histamine may account for the reduced secretory response to anti-IgE observed in IBD colonic tissues.

Animals↗

PubMed1997

Cholinergic nerves mediate stress-induced intestinal transport abnormalities in Wistar-Kyoto rats.

We have previously reported that acute stress alters intestinal transport physiology in Wistar-Kyoto rats, a stress-susceptible strain. In this study, we tested the hypothesis that the abnormalities in these rats are due to cholinergic mechanisms. Atropine- or saline-treated rats were exposed to acute restraint stress, and, subsequently, electrophysiological parameters of excised jejunal segments were assessed in Ussing chambers. Compared with the parent Wistar rat strain, Wistar-Kyoto rats demonstrated significantly greater stress-induced changes in ion secretion and permeability. The activity of cholinesterase in intestinal mucosal homogenates was significantly less in Wistar-Kyoto than in Wistar rats. Atropine pretreatment of rats before stress corrected the epithelial pathophysiology. Our results suggest that stress stimulated the release of acetylcholine, resulting in altered epithelial function in these genetically predisposed rats.

Animals↗

PubMed1997

Translocation of verotoxin-1 across T84 monolayers: mechanism of bacterial toxin penetration of epithelium.

Verotoxin-producing Escherichia coli (VTEC) are pathogenic bacteria associated with diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Verotoxins (VTs) elaborated by these organisms produce cytopathic effects on a restricted number of cell types, including endothelial cells lining the microvasculature of the bowel and the kidney. Because human intestinal epithelial cells lack the globotriaosylceramide receptor for VT binding, it is unclear how the toxin moves across the intestinal mucosa to the systemic circulation. The aims of this study were to determine the effects of VT-1 on intestinal epithelial cell function and to characterize VT-1 translocation across monolayers of T84 cells, an intestinal epithelial cell line. VT-1 at concentrations up to 1 microgram/ml had no effect on the barrier function of T84 monolayers as assessed by measuring transmonolayer electrical resistance (102 +/- 8% of control monolayers). In contrast, both VT-positive and VT-negative VTEC bacterial strains lowered T84 transmonolayer resistance (45 +/- 7 and 38 +/- 6% of controls, respectively). Comparable amounts of toxin moved across monolayers of T84 cells, exhibiting high-resistance values, as monolayers with VTEC-induced decreases in barrier function, suggesting a transcellular mode of transport. Translocation of VT-1 across T84 monolayers paralleled the movement of a comparably sized protein, horseradish peroxidase. Immunoelectron microscopy confirmed transcellular transport of VT-1, since the toxin was observed within endosomes and associated with specific intracellular targets, including the Golgi network and endoplasmic reticulum. These data present a mode of VT-1 uptake by toxin-insensitive cells and suggest a general mechanism by which bacterial toxins lacking specific intestinal receptors can penetrate the intestinal epithelial barrier.

Animals↗

PubMed1996

Neuroimmune mechanisms in health and disease: 2. Disease.

In the second part of their article on the emerging field of neuroimmunology, the authors present an overview of the role of neuroimmune mechanisms in defence against infectious diseases and in immune disorders. During acute febrile illness, immune-derived cytokines initiate an acute phase response, which is characterized by fever, inactivity, fatigue, anorexia and catabolism. Profound neuroendocrine and metabolic changes take place: acute phase proteins are produced in the liver, bone marrow function and the metabolic activity of leukocytes are greatly increased, and specific immune reactivity is suppressed. Defects in regulatory processes, which are fundamental to immune disorders and inflammatory diseases, may lie in the immune system, the neuro endocrine system or both. Defects in the hypothalamus-pituitary-adrenal axis have been observed in autoimmune and rheumatic diseases, chronic inflammatory disease, chronic fatigue syndrome and fibromyalgia. Prolactin levels are often elevated in patients with systemic lupus erythematosus and other autoimmune diseases, whereas the bioactivity of prolactin is decreased in patients with rheumatoid arthritis. Levels of sex hormones and thyroid hormone are decreased during severe inflammatory disease. Defective neural regulation of inflammation likely plays a pathogenic role in allergy and asthma, in the symmetrical form of rheumatoid arthritis and in gastrointestinal inflammatory disease. A better understanding of neuroimmunoregulation holds the promise of new approaches to the treatment of immune and inflammatory diseases with the use of hormones, neurotransmitters, neuropeptides and drugs that modulate these newly recognized immune regulators.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Neuroimmune mechanisms in health and disease: 1. Health.

A novel scientific discipline that examines the complex interdependence of the neural, endocrine and immune systems in health and disease has emerged in recent years. In health, the neuroimmunoregulatory network is fundamental to host defence and to the transfer of immunity to offspring; the network also plays important roles in intestinal physiology and in tissue regeneration, healing and reproduction. The proliferation of lymphocytes in primary lymphoid organs (bone marrow, bursa of Fabricius [in birds] and thymus) and in secondary lymphoid organs (spleen, lymph nodes and mucosal lymphoid tissue) depends on prolactin and growth hormone. These hormones allow immune cells to respond to antigen and to soluble mediators, called cytokines. Immune-derived cytokines are capable of inducing fever and of altering neuro-transmitter activity in the brain and hormone secretion by the pituitary gland. The activation of the hypothalamus-pituitary-adrenal axis by cytokines leads to immunosuppression. Lymphoid organs are innervated, and tissue mast cells respond to neurologic stimuli. In general, acetylcholine and substance P exert immunostimulatory and proinflammatory effects, whereas epinephrine and somatostatin are immunosuppressive and anti-inflammatory. In this article, the authors predict that novel approaches to immunomodulation will be possible by altering the level or efficacy of immunoregulatory hormones and neurotransmitters.

Humans↗