Interleukin 1 beta-induced increase in substance P in rat myenteric plexus

Circulating levels of cytokines, chemokines and growth factors in patients with achalasia

Idiopathic achalasia is a disease that is characterized by the absence of peristalsis and incomplete relaxation of the lower esophageal sphincter, which is accompanied by dysphagia, regurgitation, chest pain and weight loss. The role of inflammatory infiltrates in the pathogenesis of achalasia remains controversial, although the infiltrating cell profile in the tissue has been previously characterized histologically and immunohistochemically. The present study aimed to evaluate the serum levels of 27 protein biomarkers to determine their association with achalasia and the clinical disease characteristics. The cytokine, chemokine and growth factor serum profiles of 68 patients with achalasia and 39 healthy individuals were explored using the 27-Bio-Plex Pro Human Cytokine assay. Reductions in the levels of inflammatory mediators IL-1β, IL-2, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-15, IL-17, fibroblast growth factor, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interferon-γ, monocyte chemoattractant protein-1, macrophage inflammatory protein-1 (MIP-1)α and MIP-1β, regulated upon activation normal T cell expressed and presumably secreted, TNF-α and VEGF were detected in the serum samples of patients with achalasia compared with those in the control group (P<0.05). However, significant associations between the expression in the levels of inflammatory factors and clinical characteristics of the patients were not found (P>0.05). These results suggest that achalasia is a disease that has a local but not a systemic inflammatory pattern. Further studies are required to improve the current understanding of the mechanism underlying this disease.

The Enteric Network: Interactions between the Immune and Nervous Systems of the Gut

Interactions between the nervous and immune systems enable the gut to respond to the variety of dietary products that it absorbs, the broad spectrum of pathogens that it encounters, and the diverse microbiome that it harbors. The enteric nervous system (ENS) senses and reacts to the dynamic ecosystem of the gastrointestinal (GI) tract by translating chemical cues from the environment into neuronal impulses that propagate throughout the gut and into other organs in the body, including the central nervous system (CNS). This review will describe the current understanding of the anatomy and physiology of the GI tract by focusing on the ENS and the mucosal immune system. We highlight emerging literature that the ENS is essential for important aspects of microbe-induced immune responses in the gut. Although most basic and applied research in neuroscience has focused on the brain, the proximity of the ENS to the immune system and its interface with the external environment suggest that novel paradigms for nervous system function await discovery.

Gastrointestinal Parasites and the Neural Control of Gut Functions

Gastrointestinal motility and transport of water and electrolytes play key roles in the pathophysiology of diarrhea upon exposure to enteric parasites. These processes are actively modulated by the enteric nervous system (ENS), which includes efferent, and afferent neurons, as well as interneurons. ENS integrity is essential to the maintenance of homeostatic gut responses. A number of gastrointestinal parasites are known to cause disease by altering the ENS. The mechanisms remain incompletely understood. Cryptosporidium parvum, Giardia duodenalis (syn. Giardia intestinalis, Giardia lamblia), Trypanosoma cruzi, Schistosoma species and others alter gastrointestinal motility, absorption, or secretion at least in part via effects on the ENS. Recent findings also implicate enteric parasites such as C. parvum and G. duodenalis in the development of post-infectious complications such as irritable bowel syndrome, which further underscores their effects on the gut-brain axis. This article critically reviews recent advances and the current state of knowledge on the impact of enteric parasitism on the neural control of gut functions, and provides insights into mechanisms underlying these abnormalities.

Interleukin-6 modulates colonic transepithelial ion transport in the stress-sensitive wistar kyoto rat

Immunological challenge stimulates secretion of the pro-inflammatory cytokine interleukin (IL)-6, resulting in variety of biological responses. In the gastrointestinal tract, IL-6 modulates the excitability of submucosal neurons and stimulates secretion into the colonic lumen. When considered in the context of the functional bowel disorder, irritable bowel syndrome (IBS), where plasma levels of IL-6 are elevated, this may reflect an important molecular mechanism contributing to symptom flares, particularly in the diarrhea-predominant phenotype. In these studies, colonic ion transport, an indicator of absorption and secretion, was assessed in the stress-sensitive Wistar Kyoto (WKY) rat model of IBS. Mucosa-submucosal colonic preparations from WKY and control Sprague Dawley (SD) rats were mounted in Ussing chambers and the basal short circuit current (I_SC) was electrophysiologically recorded and compared between the strains. Exposure to IL-6 (1 nM) stimulated a secretory current of greater amplitude in WKY as compared to SD samples. Furthermore, the observed IL-6-mediated potentiation of secretory currents evoked by veratridine and capsaicin in SD rats was blunted in WKY rats. Exposure to IL-6 also stimulated an increase in transepithelial resistance in both SD and WKY colonic tissue. These studies demonstrate that the neuroexcitatory effects of IL-6 on submucosal plexi have functional consequences with alterations in both colonic secretory activity and permeability. The IL-6-induced increase in colonic secretory activity appears to neurally mediated. Thus, local increases in IL-6 levels and subsequent activation of enteric neurons may underlie alterations in absorpto-secretory function in the WKY model of IBS.

Colonic soluble mediators from the maternal separation model of irritable bowel syndrome activate submucosal neurons via an interleukin-6-dependent mechanism

Irritable bowel syndrome (IBS) is characterized by episodic bouts of abdominal pain, bloating, and altered bowel habit. Accumulating evidence has linked immune activation with IBS, including reports of increases in circulating levels of the proinflammatory cytokine interleukin (IL)-6. However, it is unknown whether IL-6 contributes directly to disease manifestation. As enteric nervous activity mediates motility and secretory function, the aims of this study were to determine the effects of IL-6 on submucosal neurons and related gastrointestinal (GI) function. In these studies, we examined the colons of maternally separated (MS) rats, which exhibit elevated circulating levels of IL-6 in addition to GI dysfunction. To our knowledge, these studies are the first to provide evidence of the sensitivity of submucosal neurons to colonic secretions from MS rats (n = 50, P < 0.05), thus recapitulating clinical biopsy data. Moreover, we demonstrated that the excitatory action is IL-6 dependent. Thereafter, the impact of IL-6 on neuronal and glial activation and absorpto/secretory function was pharmacologically characterized. Other proinflammatory cytokines including IL-8 (n = 30, P > 0.05), IL-1β (n = 56, P > 0.05), and TNF-α (n = 56, P > 0.05) excited fewer neurons. Both muscarinic and nicotinic cholinergic receptors participate in the effect and cause downstream activation of ERK, JAK-STAT, and NF-κB signaling cascades. Functionally, IL-6 increases transepithelial resistance and enhances neurally and cholinergically mediated ion transport. These data provide a role for IL-6 in colonic secretory functions and relate these effects to GI dysfunction in an animal model of IBS, thereby elucidating a potential relationship between circulating levels of IL-6 and aberrant GI function.

Three days after a single exposure to ozone, the mechanism of airway hyperreactivity is dependent on substance P and nerve growth factor

Ozone causes persistent airway hyperreactivity in humans and animals. One day after ozone exposure, airway hyperreactivity is mediated by release of eosinophil major basic protein that inhibits neuronal M(2) muscarinic receptors, resulting in increased acetylcholine release and increased smooth muscle contraction in guinea pigs. Three days after ozone, IL-1β, not eosinophils, mediates ozone-induced airway hyperreactivity, but the mechanism at this time point is largely unknown. IL-1β increases NGF and the tachykinin substance P, both of which are involved in neural plasticity. These experiments were designed to test whether there is a role for NGF and tachykinins in sustained airway hyperreactivity following a single ozone exposure. Guinea pigs were exposed to filtered air or ozone (2 parts per million, 4 h). In anesthetized and vagotomized animals, ozone potentiated vagally mediated airway hyperreactivity 24 h later, an effect that was sustained over 3 days. Pretreatment with antibody to NGF completely prevented ozone-induced airway hyperreactivity 3 days, but not 1 day, after ozone and significantly reduced the number of substance P-positive airway nerve bundles. Three days after ozone, NK(1) and NK(2) receptor antagonists also blocked this sustained hyperreactivity. Although the effect of inhibiting NK(2) receptors was independent of ozone, the NK(1) receptor antagonist selectively blocked vagal hyperreactivity 3 days after ozone. These data confirm mechanisms of ozone-induced airway hyperreactivity change over time and demonstrate 3 days after ozone that there is an NGF-mediated role for substance P, or another NK(1) receptor agonist, that enhances acetylcholine release and was not present 1 day after ozone.

An increased proportion of inflammatory cells express tumor necrosis factor alpha in idiopathic achalasia of the esophagus

Achalasia is a motility disorder characterized by the absence of coordinated peristalsis and incomplete relaxation of the lower esophageal sphincter. The etiology remains unclear although dense inflammatory infiltrates within the myenteric plexus have been described. The nature of these infiltrating cells is unknown. The aim of this study was to evaluate the expression of proinflammatory cytokines - namely, tumor necrosis factor alpha and interleukin-2 - in the distal esophageal muscle in patients with achalasia. Lower esophageal sphincter muscle from eight patients undergoing myotomy or esophagectomy for achalasia of the esophagus were obtained at the time of surgery. Control specimens consisted of similar muscle taken from eight patients undergoing operation for cancer or Barrett's esophagus. The expression of tumor necrosis factor alpha and interleukin-2 were assessed by immunohistochemistry. The total number of inflammatory cells within the myenteric plexus were counted in five high power fields. The percentage of infiltrating cells expressing tumor necrosis factor alpha or interleukin-2 was calculated. Clinical data including demographics, preoperative lower esophageal sphincter pressure, duration of symptoms, and dysphagia score (1 = no dysphagia to 5 = dysphagia to saliva) were obtained through electronic medical records. Statistical comparisons between the groups were made using the unpaired t-test, Fisher's exact test, or Mann-Whitney U test, with a two-tailed P-value less than 0.05 being considered significant. The total number of inflammatory cells was found to be similar between the groups. A significantly higher proportion of inflammatory cells expressed tumor necrosis factor alpha in achalasia as compared with controls (22 vs. 11%; P= 0.02). A similar percentage of infiltrating cells expressed interleukin-2 (40 vs. 41%; P= 0.87). Age, gender, preoperative lower esophageal sphincter pressure, or dysphagia score were not correlated to expression of these cytokines. There was, however, a significant inverse correlation between duration of symptoms and the proportion of inflammatory cells expressing tumor necrosis factor alpha in achalasia (P= 0.007). In conclusion, a higher proportion of infiltrating inflammatory cells expressed tumor necrosis factor alpha in achalasia. Furthermore, this proportion appears to be highest early in the disease process. Further studies are required to more clearly delineate the role of tumor necrosis factor alpha in the pathogenesis of this idiopathic disease.

Endogenous and exogenous ghrelin enhance the colonic and gastric manifestations of dextran sodium sulphate-induced colitis in mice

Ghrelin is an important orexigenic peptide that not only exerts gastroprokinetic but also immunoregulatory effects. This study aimed to assess the role of endogenous and exogenous ghrelin in the pathogenesis of colitis and in the disturbances of gastric emptying and colonic contractility during this process. Dextran sodium sulphate colitis was induced for 5 days in (i) ghrelin(+/+) and ghrelin(-/-) mice and clinical and histological parameters were monitored at days 5, 10 and 26 and (ii) in Naval Medical Research Institute non-inbred Swiss (NMRI) mice treated with ghrelin (100 nmol kg(-1)) twice daily for 5 or 10 days. Neural contractility changes were measured in colonic smooth muscle strips, whereas gastric emptying was measured with the (14)C octanoic acid breath test. Inflammation increased ghrelin plasma levels. Body weight loss, histological damage, myeloperoxidase activity and IL-1beta levels were attenuated in ghrelin(-/-) mice. Whereas absence of ghrelin did not affect changes in colonic contractility, gastric emptying in the acute phase was accelerated in ghrelin(+/+) but not in ghrelin(-/-) mice. In agreement with the studies in ghrelin knockout mice, 10 days treatment of NMRI mice with exogenous ghrelin enhanced the clinical disease activity and promoted infiltration of neutrophils and colonic IL-1beta levels. Unexpectedly, ghrelin treatment decreased excitatory and inhibitory neural responses in the colon of healthy but not of inflamed NMRI mice. Endogenous ghrelin enhances the course of the inflammatory process and is involved in the disturbances of gastric emptying associated with colitis. Treatment with exogenous ghrelin aggravates colitis, thereby limiting the potential therapeutic properties of ghrelin during intestinal inflammation.

The beta3-adrenoceptor agonist SR58611A ameliorates experimental colitis in rats

Beta(3)-adrenoceptor agonists protect against experimental gastric ulcers. We investigated the effects of the beta(3)-adrenoceptor agonist SR58611A on 2,4-dinitrobenzene sulphonic acid-induced colitis in rats and analysed the expression of beta(3)-adrenoceptors in the colonic wall. SR58611A was administered orally (1-10 mg kg(-1)) for 7 days, starting the day before induction of colitis. Colitis was assessed by macroscopic and histological scores, tissue myeloperoxidase activity, interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) levels. Reverse transcription-polymerase chain reaction and immunohistochemical analysis were used to examine the expression of beta(3)-adrenoceptors. SR58611A significantly reduced the severity of colitis as well as the tissue levels of TNF-alpha, IL-1beta and IL-6. Colitis was associated with a decreased expression of beta(3)-adrenoceptor mRNA in the mucosal/submucosal layer of distal colon and this reduction was not affected by SR58611A. Immunohistochemical analysis revealed beta(3)-adrenoceptors within the muscularis externa, in myenteric neurons and nerve fibres and in the submucosa. beta(3)-Adrenoceptor immunoreactivity was decreased in inflamed tissues compared to controls, particularly in the myenteric plexus; this reduction was counteracted by SR58611A. Amelioration of experimental colitis by the selective beta(3)-adrenoceptor agonist SR58611A suggests that beta(3)-adrenoceptors may represent a therapeutic target in gut inflammation.

IL-1 receptors mediate persistent, but not acute, airway hyperreactivity to ozone in guinea pigs

Ozone exposure in the lab and environment causes airway hyperreactivity lasting at least 3 days in humans and animals. In guinea pigs 1 day after ozone exposure, airway hyperreactivity is mediated by eosinophils that block neuronal M(2) muscarinic receptor function, thus increasing acetylcholine release from airway parasympathetic nerves. However, mechanisms of ozone-induced airway hyperreactivity change over time, so that depleting eosinophils 3 days after ozone makes airway hyperreactivity worse rather than better. Ozone exposure increases IL-1beta in bone marrow, which may contribute to acute and chronic airway hyperreactivity. To test whether IL-1beta mediates ozone-induced airway hyperreactivity 1 and 3 days after ozone exposure, guinea pigs were pretreated with an IL-1 receptor antagonist (anakinra, 30 mg/kg, intraperitoneally) 30 minutes before exposure to filtered air or to ozone (2 ppm, 4 h). One or three days after exposure, airway reactivity was measured in anesthetized guinea pigs. The IL-1 receptor antagonist prevented ozone-induced airway hyperreactivity 3 days, but not 1 day, after ozone exposure. Ozone-induced airway hyperreactivity was vagally mediated, since bronchoconstriction induced by intravenous acetylcholine was not changed by ozone. The IL-1 receptor antagonist selectively prevented ozone-induced reduction of eosinophils around nerves and prevented ozone-induced deposition of extracellular eosinophil major basic protein in airways. These data demonstrate that IL-1 mediates ozone-induced airway hyperreactivity at 3 days, but not 1 day, after ozone exposure. Furthermore, preventing hyperreactivity was accompanied by decreased eosinophil major basic protein deposition within the lung, suggesting that IL-1 affects eosinophil activation 3 days after ozone exposure.

T cells in the myenteric plexus of achalasia patients show a skewed TCR repertoire and react to HSV-1 antigens

OBJECTIVE

The loss of myenteric neurons in the lower esophageal sphincter (LES) characterizes achalasia, an esophageal motor disorder. Because the presence of lymphocytic infiltrates suggests an immuno-mediated mechanism ongoing at the sites of disease, we investigated the T-cell receptor (TCR) repertoire and the ability to recognize human herpes virus type 1 (HSV-1) antigens of LES-infiltrating T lymphocytes in achalasia patients.

METHODS

Fifty-nine patients with idiopathic achalasia and 38 heart-beating cadaveric multiorgan donors (controls) were studied. By flow cytometry evaluation and CDR3 length spectratyping analysis, the lymphocytes of 18 patients and 15 controls were analyzed, whereas 41 patients and 23 controls were employed for functional assays.

RESULTS

Achalasia patients were characterized by a significantly higher esophagus lymphocytic infiltrate than controls (24.71%+/- 3.11 and 9.54%+/- 1.34, respectively; P < 0.05), mainly represented by CD3+CD8+ T cells. The characterization of TCR beta chain repertoire of CD3+ cells showed the expression of a limited number of TCR beta variable (BV) gene families (from two to five out of 26), with highly restricted spectratypes, suggesting a disease-associated oligoclonal selection of T cells. Furthermore, lymphocytes from achalasia LES specifically responded to exposure to HSV-1 antigens in vitro as showed by increased proliferation and Th-1 type cytokines release.

CONCLUSIONS

These data suggest that the oligoclonal lymphocytic infiltrate within the LES of achalasia patients may represent the trace of an immune-inflammatory reaction triggered by HSV-1 antigens and that the Th1-type cytokines released by the activated lymphocytes may contribute to establish the neuronal damage accounting for the clinical features of idiopathic achalasia.

Neural mechanisms of early postinflammatory dysmotility in rat small intestine

Although human postinflammatory dysmotility is known, so far animal studies have primarily investigated changes during inflammation. Here, we focused on postinflammatory changes in rat jejunal myenteric plexus and jejunal motility. Evolution of ethanol/2,4,6-tri-nitrobenzene sulphonic acid (TNBS)-induced inflammation was assessed histologically and by measuring myeloperoxidase activity (MPO). Electromyography and immunohistochemistry were performed 1 week after ethanol/TNBS and also after N(G)-nitro-L-arginine methyl ester (L-NAME) administration. Ethanol/TNBS induced a transient inflammation, with normalization of MPO and histological signs of an early phase of recovery after 1 week. The number of cholinergic neurones was not altered, but myenteric neuronal nitric oxide synthase (nNOS)-immunoreactivity was significantly lower in the early phase of recovery after TNBS compared with water (1.8 +/- 0.2 vs 3.5 +/- 0.2 neurones ganglion(-1), P < 0.001). Interdigestive motility was disrupted with a loss of phase 1 quiescence, an increase of migrating myoelectric complex cycle length, a higher number of non-propagated activity fronts and a decrease of adequately propagated phase 3 s after TNBS. Administration of L-NAME resulted in a similar disruption of interdigestive motility patterns. In the early phase of recovery after ethanol/TNBS-induced jejunal inflammation, a loss of motor inhibition occurs due to a decrease of myenteric nNOS activity. These observations may provide a model for early postinflammatory dysmotility syndromes.

Intestinal dysmotility in inflammatory bowel disease: mechanisms of the reduced activity of smooth muscle contraction

Inflammation suppresses intestinal motility, which secondarily induces abnormal growth of intestinal flora. Disturbance of this flora plays a role in the pathogenesis of mucosal inflammation, which in turn aggravates the intestinal dysmotility. Therefore, it is important to know the mechanism of alteration in motor function in the inflamed intestine. Recent studies have shown molecular mechanisms responsible for the motility disorder in the inflamed gut. These include an increase in the activity of myosin light-chain phosphatase and an alteration of ion channel activity in smooth muscle cells.

Inflammation as a basis for functional GI disorders

The term 'Functional diseases' implies symptoms arising from an organ without overt pathology. However this is more apparent than real since inflammation often leaves changes in nerves and mucosal function only apparent with specialised techniques. Acute onset functional dyspepsia accounts for around 1/5 of functional dyspepsia and is characterised by early satiety, nausea, vomiting and weight loss. Impaired postcibal fundal accommodation may underlie some of these symptoms. Post infectious gastroparesis is much rarer and is associated with markedly delayed gastric emptying and antral hypomotility. Approximately 1/10 of IBS cases describe a post infectious onset. Post infectious IBS is typically of the diarrhoea-predominant type. Post inflammatory functional diseases tend to be associated with less psychological abnormalities and have a better prognosis than other functional diseases. There are isolated anecdotal reports of symptom response to anti-inflammatory treatments but larger controlled trials are needed.

Inflammation as a basis for functional GI disorders

The term 'Functional diseases' implies symptoms arising from an organ without overt pathology. However this is more apparent than real since inflammation often leaves changes in nerves and mucosal function only apparent with specialised techniques. Acute onset functional dyspepsia accounts for around 1/5 of functional dyspepsia and is characterised by early satiety, nausea, vomiting and weight loss. Impaired postcibal fundal accommodation may underlie some of these symptoms. Post infectious gastroparesis is much rarer and is associated with markedly delayed gastric emptying and antral hypomotility. Approximately 1/10 of IBS cases describe a post infectious onset. Post infectious IBS is typically of the diarrhoea-predominant type. Post inflammatory functional diseases tend to be associated with less psychological abnormalities and have a better prognosis than other functional diseases. There are isolated anecdotal reports of symptom response to anti-inflammatory treatments but larger controlled trials are needed.

Interleukin-1 beta selectively increases substance P release and augments the ascending phase of the peristaltic reflex

Exposure of muscle strips to interleukin (IL)-1beta stimulates substance P (SP) expression, suggesting a link between IL-1beta and the increase in SP expression during intestinal inflammation. The present study examined whether the SP expression induced by IL-1beta is reflected by enhanced SP release and SP-mediated reflex activity. Exposure of innervated longitudinal colonic muscle strips to IL-1beta for 8 h increased SP synthesis in, and greater SP release from excitatory motor neurones in response to KCl or electrical field stimulation (EFS), and enhanced longitudinal muscle contraction in response to EFS. IL-1 Ra and IL-1beta antibody blocked IL-1beta-induced increase in SP release and muscle contraction. Neither vasoactive intestinal peptide (VIP) nor somatostatin release was increased. The increase in SP release was reflected in enhanced circular muscle contraction in response to stretch. VIP-mediated descending relaxation of circular muscle was not affected. The selective increase in ascending contraction induced by exposure to IL-1beta was blocked by IL-1 Ra or IL-1beta antibody. We conclude that the selective increase in SP expression induced by IL-1beta in excitatory motor neurones is reflected by enhanced SP release and longitudinal muscle contraction in response to EFS, and enhanced SP release and circular muscle contraction during the ascending phase of the peristaltic reflex.

Chronic treatment with interleukin-1beta attenuates contractions by decreasing the activities of CPI-17 and MYPT-1 in intestinal smooth muscle

Interleukin-1beta (IL-1beta) is a proinflammatory cytokine that plays a central role in inflammatory bowel disease (IBD). In order to elucidate the mechanism of motility disorders frequently observed in IBD, we investigated the long term effects of IL-1beta on rat ileal smooth muscle contractility by using an organ culture system. When ileal smooth muscle strips were cultured with IL-1beta (10 ng/ml), contractions elicited by high K+ and carbachol were inhibited in a time-dependent manner. IL-1beta more strongly inhibited the carbachol-induced contractions than high K+ with decreasing myosin light chain phosphorylation. In the alpha-toxin-permeabilized ileal muscle, carbachol with GTP or guanosine 5'-3-O-(thio)triphosphate increased the Ca2+ sensitivity of contractile elements, and this G protein-coupled Ca2+ sensitization was significantly reduced in the IL-1beta-treated ileum. Among the functional proteins involved in the smooth muscle Ca2+ sensitization, CPI-17 expression was significantly reduced after the culture with IL-1beta, whereas the expressions of RhoA, ROCK-I, ROCK-II, MYPT-1, myosin light chain kinase, and myosin phosphatase (PP1) were unchanged. The phosphorylation level of CPI-17 by carbachol was low in accordance with the decrease in CPI-17 expression due to IL-1beta treatment. In contrast, constitutively phosphorylated MYPT-1 was also decreased in the IL-1beta-treated muscles. These results suggest that long term treatment with IL-1beta decreases either CPI-17 expression or MYPT-1 phosphorylation, which may result in an increase in myosin phosphatase activity to reduce force generation. Based on these findings, we consider IL-1beta to be an important mediator of gastrointestinal motility disorders in IBD, and CPI-17 and MYPT-1 are key molecules in the decreased smooth muscle contractility due to IL-1beta.

Interleukin-1beta-induced airway hyperresponsiveness enhances substance P in intrinsic neurons of ferret airway

Interleukin (IL)-1beta causes airway inflammation, enhances airway smooth muscle responsiveness, and alters neurotransmitter expression in sensory, sympathetic, and myenteric neurons. This study examines the role of intrinsic airway neurons in airway hyperresponsiveness (AHR) induced by IL-1beta. Ferrets were instilled intratracheally with IL-1beta (0.3 microg/0.3 ml) or saline (0.3 ml) once daily for 5 days. Tracheal smooth muscle contractility in vitro and substance P (SP) expression in tracheal neurons were assessed. Tracheal smooth muscle reactivity to acetylcholine (ACh) and methacholine (MCh) and smooth muscle contractions to electric field stimulation (EFS) both increased after IL-1beta. The IL-1beta-induced AHR was maintained in tracheal segments cultured for 24 h, a procedure that depletes SP from sensory nerves while maintaining viability of intrinsic airway neurons. Pretreatment with CP-99994, an antagonist of neurokinin 1 receptor, attenuated the IL-1beta-induced hyperreactivity to ACh and MCh and to EFS in cultured tracheal segments. SP-containing neurons in longitudinal trunk, SP innervation of superficial muscular plexus neurons, and SP nerve fiber density in tracheal smooth muscle all increased after treatment with IL-1beta. These results show that IL-1beta-enhanced cholinergic airway smooth muscle contractile responses are mediated by the actions of SP released from intrinsic airway neurons.

Expression of neuropeptides and cytokines at the extensor carpi radialis brevis muscle origin

To reveal whether neuropeptides and cytokines affect the pathogenesis of tennis elbow, expressions of substance P, calcitonin gene-related peptide, interleukin 1 alpha, and transforming growth factor beta1 at the origin of the extensor carpi radialis brevis muscle were investigated in patients with tennis elbow (n = 10). Innervation in the origin was determined with use of the protein gene product 9.5. Substance P-like immunoreactivity and calcitonin gene-related peptide-like immunoreactivity were observed in the nerve fibers around small vessels without apparent infiltration of inflammatory cells. Cells showing positive interleukin 1 alpha or transforming growth factor beta1 immunoreactivity were noted in small vessels and the dense collagen meshwork in 5 of 10 cases. The results suggested that these neuropeptides and cytokines might promote inflammation and stimulate proliferation and matrix synthesis of fibroblasts, contributing to the pathology of tennis elbow.

Immune-mediated neural dysfunction in a murine model of chronic Helicobacter pylori infection

BACKGROUND & AIMS

Neuromuscular changes producing dysmotility and hyperalgesia may underlie symptom generation in functional gastrointestinal disorders. We investigated whether chronic Helicobacter pylori-induced gastritis causes neuromuscular dysfunction.

METHODS

In vitro muscle contractility and acetylcholine release were evaluated in mice before and after H. pylori eradication. H. pylori colonization and gastritis were graded histologically. Substance P (SP)-, vasoactive intestinal polypeptide (VIP)-, and calcitonin gene-related peptide (CGRP) immunoreactivity (IR) and macrophages were studied by immunohistochemistry.

RESULTS

In Balb/c mice, chronic H. pylori infection did not affect muscle function but augmented antral relaxation after nerve electric field stimulation. Infected mice had lower acetylcholine release by electric field stimulation and had higher density of SP-, CGRP-, and VIP-IR nerves in the stomach and of SP- and CGRP-IR in the spinal cord. Cholinergic nerve dysfunction worsened progressively and was associated with increasing macrophage and mononuclear but not polymorphonuclear infiltrate or bacterial colonization. SCID mice had unchanged acetylcholine release despite high H. pylori colonization and macrophage infiltration. Eradication of H. pylori normalized functional and morphologic abnormalities except for increased density of gastric SP- and CGRP-IR nerves.

CONCLUSIONS

H. pylori infection induces functional and morphologic changes in the gastric neural circuitry that are progressive and lymphocyte dependent, and some persist after H. pylori eradication. The data have direct implications regarding the role of H. pylori infection in functional dyspepsia.

Integrative neuroimmunomodulation of gastrointestinal function during enteric parasitism

Enteric helminths have a significant impact on the structure, function, and neural control of the gastrointestinal (GI) tract of the host. Interactions between the host's nervous and immune systems redirect activity in neuronal circuits intrinsic to the gut into an alternative repertoire of defensive and adaptive motor programs. Gut inflammation and activation of the enteric neuroimmune axis play integral roles in the dynamic interaction between host and parasite that occurs at the mucosal surface. Three inter-related themes are stressed in this review to underscore the pivotal role that neural control mechanisms play in the host's GI tract functional responses to enteric parasitism. First, we address the discovery that signaling molecules of both parasite and host origin can reorient the dynamic ecology of enteric host-parasite interactions. Second, we explore what has been learned from investigations of altered gut propulsive and secretomotor reflex activities that occur during enteric parasitic infections and the emerging picture derived from these studies that elucidates how nerves help facilitate and orchestrate functional reorganization of the parasitized gut. Third, we provide an overview of the direct impact that enteric parasitism has on nerve cell function and neurotransmission pathways in both the enteric and central nervous systems of the host. In summary, this review highlights and clarifies the complex mechanisms underlying integrative neuroimmunophysiological responses to the presence of both invasive and noninvasive enteric helminths and identifies directions for future research investigations in this highly important but understudied area.

Effect of recombinant human interleukin-11 on motilin and substance P release in normal and inflamed rabbits

Recombinant human interleukin-11 (rhIL-11) normalizes depressed smooth muscle tension generation towards motilin and substance P (SP) in rabbits with colitis. The aim of this paper was to evaluate the effect of rhIL-11 treatment on motilin and SP release which could have an effect on the contractility changes. Rabbits received 4, 40, 72 or 720 microg/kg rhIL-11 s.c. or saline, 1 h later a continuous s.c. administration of rhIL-11 was started with or without the induction of colitis (135 mg/kg TNBS) for 5 days. Motilin and SP levels were measured by RIA, motilin mRNA expression by RT-PCR. TNBS-colitis did not affect plasma motilin levels but increased the motilin content of the duodenal mucosa 1.7-fold. rhIL-11 treatment dose-dependently increased plasma motilin levels (720 microg/kg day: 3.5-fold) and the motilin content of the duodenal mucosa (720 microg/kg day: 3.0-fold). The effects of rhIL-11 were similar in normal rabbits and were accompanied by an increased motilin mRNA expression. TNBS-colitis decreased plasma SP levels 2.7-fold and the SP content in the colonic muscle layer 7.1-fold. The decrease in the muscle layer, but not in the plasma, was normalized by rhIL-11 treatment. In normal rabbits, rhIL-11 caused a decrease in plasma SP levels, but had no effect on the tissue content of SP. In conclusion, treatment of inflamed or normal rabbits with rhIL-11 increases plasma and tissue levels of motilin in the duodenal mucosa via an increased expression of motilin in the endocrine cells and induces the release of SP from extrinsic neurons. These changes do not explain the beneficial effect of rhIL-11 on the lowered contractility in inflamed rabbits although a change in balance of neuropeptides may influence gastro-intestinal inflammation.

Consequences of intestinal inflammation on the enteric nervous system: neuronal activation induced by inflammatory mediators

The ENS is responsible for the regulation and control of all gastrointestinal functions. Because of this critical role, and probably as a consequence of its remarkable plasticity, the ENS is often relatively well preserved in conditions where the architecture of the intestine is seriously disrupted, such as in IBD. There are structural and functional changes in the enteric innervation in animal models of experimental intestinal inflammation and in IBD. These include both up and down regulation of transmitter expression and the induction of new genes in enteric neurons. Using Fos expression as a surrogate marker of neuronal activation it is now well established that enteric neurons (and also enteric glia) respond to inflammation. Whether this "activation" is limited to a short-term functional response, such as increased neuronal excitability, or reflects a long-term change in some aspect of the neuronal phenotype (or both) has yet to be firmly established, but it appears that enteric neurons are highly plastic in their response to inflammation.

Induction of nociceptive responses by intrathecal injection of interleukin-1 in mice

Intrathecal (i.t.) injection (between lumbar vertebrae 5 and 6) into mice of a markedly low dose of IL-1alpha (3x10(-4) fmol or 5.4 fg in 5 microl per mouse) induced behaviors involving scratching, biting, and licking of non-stimulated hindpaws. The IL-1-induced behaviors appeared within 10 min of the injection of IL-1alpha, peaked at 20-40 min, and had disappeared 60 min after the injection. The IL-1-induced behaviors were similar to the nociceptive responses induced in mice by i.t. injection of substance P (SP) or subcutaneous (s.c.) injection of formalin into the footpad. The IL-1-induced behaviors were suppressed by intraperitoneal morphine, indicating that they are nociceptive responses. The nociceptive responses induced by 3x10(-4) (5.4 fg) of IL-1alpha were almost completely suppressed by co-injection of 0.3 fmol (7.2 pg) of an IL-1 receptor antagonist (IL-1ra). An antiserum against substance P, but not an antiserum against somatostatin, suppressed the IL-1-induced nociceptive responses. The nociceptive responses induced by s.c. injection of 2% formalin into the footpad were also inhibited by i.t. injection of 30 pmol (720 ng) of IL-1ra. These results suggest that IL-1 may play a role in hyperalgesia in mice by acting as a factor augmenting pain transmission in the spinal cord at least in part by either directly or indirectly releasing substance P.

IL-1beta and IL-6 excite neurons and suppress nicotinic and noradrenergic neurotransmission in guinea pig enteric nervous system

Conventional intracellular microelectrodes and injection of biocytin were used to study the actions of IL-1beta and IL-6 on electrical and synaptic behavior in morphologically identified guinea pig small intestinal submucous neurons. Exposure to nanomolar concentrations of either IL-1beta or IL-6 stimulated neuronal excitability. The excitatory action consisted of depolarization of the membrane potential, decreased membrane conductance, and increased discharge of action potentials. Excitatory action of IL-1beta was suppressed by the natural IL-1beta human receptor antagonist. Electrical stimulation of sympathetic postganglionic axons evoked inhibitory postsynaptic potentials (IPSPs), and stimulation of cholinergic axons evoked nicotinic fast excitatory postsynaptic potentials (EPSPs). Both kinds of synaptic potentials occurred in neurons with uniaxonal morphology believed to be secretomotor neurons. Either IL-1beta or IL-6 suppressed the noradrenergic IPSPs and the fast EPSPs, and the two acted synergistically when applied in combination. Suppression of the IPSP resulted from presynaptic inhibition of the release of norepinephrine from sympathetic nerves. The results suggest that the presence of either or both inflammatory cytokines will release the sympathetic brake from secretomotor neurons to the intestinal crypts and from nicotinic synapses in the integrative microcircuits, where norepinephrine is known to have a presynaptic inhibitory action. This, in concert with excitation of secretomotor neurons, may lead to neurogenic secretory diarrhea.

Effect of interleukin-1beta on the ascending and descending reflex in rat small intestine

Acute inflammation of the intestine is associated with motility changes. We investigated the acute effect of inflammatory mediators such as interleukin-1beta, interleukin-2 and tumor necrosis factor-alpha (TNF-alpha) on electrically stimulated ascending and descending reflex responses of the rat small intestine. Exogenous application of interleukin-1beta caused a concentration-dependent inhibition of the oral contraction (0.1 ng/ml: -22.9+/-3.8%, 10 ng/ml: -57.0+/-7.4%, P < 0.05, n=10) but had no effect on anal relaxation. The interleukin-1 receptor antagonist alone had no significant effect on the reflex response, but prevented the inhibitory effect of interleukin-1beta (10 ng/ml: -3.9+/-11.4%, n=8). Interleukin-2 and TNF-alpha had no significant effect on the oral contractile and the anal inhibitory response (n.s., n=10). Using reverse transcriptase polymerase chain reaction (RT-PCR) the presence of mRNA of the interleukin-1 receptor was demonstrated in the rat small intestine. Preincubation of the preparation with indomethacin (10(-6) M), the histamine H1 receptor antagonist, pyrilamine (10(-8) M), and the histamine H3 receptor antagonist, clobenpropit (10(-8) M), decreased the oral contraction by 60.1+/-7.7%, 42.8+/-6.9% and 44.4+/-14.2% as well as the anal relaxation. These data suggest that acute administration of interleukin-1beta inhibits the ascending and descending contractile reflex pathway and this effect seems not to be mediated by prostaglandins or histamine receptors.

What role does Helicobacter pylori play in dyspepsia and nonulcer dyspepsia? Arguments for and against H. pylori being associated with dyspeptic symptoms

A major role for Helicobacter pylori gastritis in nonulcer dyspepsia (NUD) is controversial. Gastroduodenal dysfunction may be associated with H. pylori infection, but there is little evidence for a causal link with dyspepsia. Population-based studies with appropriate methodology have generally failed to confirm an association between H. pylori and NUD. Furthermore, no definite association between subgroups of NUD (ulcer-like, dysmotility-like, reflux-like, and nonspecific) and H. pylori has been identified however the subgroups have been defined, and no specific symptom pattern characterizes patients with H. pylori infection. Whether H. pylori-induced alterations of gastric physiology can explain NUD remains open to debate while we await the results of more specific experiments. Although acid secretion in response to gastrin-releasing peptide may be increased in a subset of NUD patients who are infected with H. pylori, uninfected patients with NUD have not been assessed and the results require confirmation. Most studies suggest no association between H. pylori and gastroduodenal motor or sensory dysfunction in NUD. Treatment trials have been unconvincing. The trials with bismuth therapy have not been adequately blinded. Furthermore, some studies suggest that H. pylori-negative patients with NUD may respond to bismuth treatment, although the results have not been uniform. Therapies aimed at curing H. pylori infection have produced mixed results, with small positive and negative trials. The trials that have used adequate outcome measures have more often than not been negative. Based on current evidence, H. pylori is not established to be of causal importance in NUD.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.

Toxicological considerations in evaluating indoor air quality and human health: impact of new carpet emissions

This review article considers evidence regarding the toxicological impact of new carpet emissions on indoor air quality and human health. It compares emissions data from several studies and describes the dominant compounds found in those emissions. The toxicity of each these compounds is assessed for animal and human data, with a focus on inhalation exposure. Data for acute and chronic exposures are presented, and synergistic effects are considered. Differences and similarities between health responses caused by toxicity and/or by immunological reactions are discussed. Possible neurogenic pathways and associations between these and immune changes are considered as they might relate to inflammatory-based human reactions. Additionally, factors affecting human odor responses are described. The roles that a variety of psychological factors may also play in the etiology of potentially related phenomena, such as the sick building syndrome, pathogenic illness, and multiple chemical sensitivity, are considered. Gaps in the literature are identified within the article and suggestions for future research are offered. In particular, it is noted that few, if any, prior studies have evaluated both neurogenic and immune-mediated inflammation status within the same study. Based on the present information available, it is concluded that under normal environmental circumstances, VOC emissions from new carpets are sufficiently low such that they should not adversely affect indoor air quality or pose significant health risk to people.

Increased expression of interferon-gamma in a rat model of chronic intestinal allograft rejection

Chronic rejection remains a major cause of late graft dysfunction. Although much research has focused on acute rejection, little is known about the mechanisms of chronic rejection. Our group has recently reported evidence of significant intestinal smooth muscle hypertrophy and hyperplasia associated with abnormal contractile and electrical activities in a rat model of chronic intestinal rejection. The changes in the smooth muscle layer are associated with a significant inflammatory infiltrate. In order to further delineate the immune mechanisms of chronic rejection, we sought to clarify the nature of this infiltrate. Orthotopic small bowel transplantation was performed using an allogeneic (ACI-Lewis) rat combination. The rats only received immunosuppression for the first 28 days posttransplantation (cyclosporine 15 mg/kg daily from postoperative day 0 to 6 and every other day from postoperative day 7 to 28). This led to chronic rejection of the graft by day 90, at which time the rats were sacrificed. Analysis by immunohistochemistry revealed NK and CD5+ leukocytes infiltrating the muscular layer. Examination of cytokine production by radiolabeled polymerase chain reaction showed high levels of steady state interferon-gamma mRNA in full thickness intestinal segments and within the isolated muscularis of chronically rejecting intestinal allografts as compared to syngeneic and control grafts. Interferon-gamma mRNA was localized to both the muscularis and mucosa. Interestingly, positively hybridized cells within the muscularis tended to preferentially localize to the myenteric and submucosal plexuses suggesting potential role for this cytokine in chronic intestinal ejection.

Effect of interleukin-1 beta on the release of substance P from rat isolated spinal cord

Superfusion of rat spinal cord slices with rat interleukin-1 beta resulted in a significant enhancement of electrically evoked substance P-like immunoreactivity with a maximal effect (> 2-fold increase) at 0.1 ng/ml, whereas higher concentration (10-50 ng/ml) of the cytokine inhibited (approximately 50%) the release of the neuropeptide. Interleukin-1 beta (0.1 ng/ml) potentiation of substance P-like immunoreactivity release was abrogated by co-perfusion with interleukin-1 receptor antagonist (10-100 ng/ml) or with indomethacin (1 microM). Superfusion of spinal cord with interleukin-1 beta inhibited electrically evoked calcitonin gene-related peptide-like immunoreactivity release. Modulation of substance P-like immunoreactivity release from the spinal cord by interleukin-1 beta may represent a mechanism responsible for the hyperalgesic action of the cytokine characteristic of the inflammatory response.

Involvement of eicosanoids and macrophage-like cells in cytokine-mediated changes in rat myenteric nerves

BACKGROUND & AIMS

Proinflammatory cytokines alter function in enteric nerves, but little is known about underlying mechanisms. This study was designed to investigate the roles of prostanoids and of macrophage-like cells in cytokine-induced suppression of [3H]norepinephrine release from rat myenteric plexus.

METHODS

The release of 3H from jejunal longitudinal muscle-myenteric plexus preparations that had been loaded with [3H]norepinephrine was measured. Measurements of 3H release as well as concentrations of prostaglandin E2 and leukotriene were made in preparations exposed to interleukin 1 beta plus interleukin 6 and in the presence or absence of piroxicam, 5-lipoxygenase inhibitor MK886, cycloheximide, or cyclosporin A. An ultrastructural analysis was also performed to investigate the presence of macrophage-like cells in the myenteric plexus.

RESULTS

Interleukin 1 beta plus interleukin 6 suppressed 3H release and caused an increase in tissue prostaglandin E2 but not leukotriene E4. Piroxicam and cycloheximide but not MK886 attenuated the cytokine-induced increase in prostaglandin E2 and the suppression of [3H]norepinephrine release. Ultrastructural analysis showed macrophage-like cells in the plexus, and the cytokine effects were inhibited by cyclosporin A.

CONCLUSIONS

Prostanoids but not leukotrienes mediate the cytokine-induced suppression of norepinephrine release, and the results of this study suggest that macrophage-like cells are also involved.

Implication of NK1 and NK2 receptors in rat colonic hypersecretion induced by interleukin 1 beta: role of nitric oxide

BACKGROUND & AIMS

Interleukin (IL) 1 beta is known to induce a neurally mediated colonic water secretion in vivo. The aim of this study was to investigate the mechanism of action of IL-1 beta on colonic net water flux and the role of tachykinins and nitric oxide.

METHODS

In anesthetized rats, isolated colonic loops were infused with Ringer's buffer containing [14C]polyethylene glycol 4000. Net water flux was calculated according to 14C activity determined in the effluent that was collected at 15-minute intervals.

RESULTS

Recombinant human IL-1 beta induced a 30-minute colonic hypersecretion. This effect was blocked by NK1 and NK2 antagonists, tetrodotoxin, and NG-methyl-L-arginine (L-NMA). L-arginine reversed the antisecretory effect of L-NMA on IL-1 beta-induced hypersecretion but did not modify the IL-1 beta-induced hypersecretion. Both NK1 and NK2 agonists induced a colonic hypersecretion, and their effects were blocked by L-NMA and tetrodotoxin. The NK3 agonist had no effect on water movements. The NK2 antagonist abolished the secretory effect of NK1 agonist; in contrast, the NK1 antagonist had no effect on the NK2 agonist-induced secretion.

CONCLUSIONS

IL-1 beta-induced colonic hypersecretion in vivo involves NK1- and NK2-receptor activation in cascade, suggesting a release of substance P and neurokinin A acting through NO release.