Nerve fiber outgrowth is increased in the intestinal mucosa of patients with irritable bowel syndrome.

BACKGROUND & AIMS: Mediators released by the intestinal mucosa of patients with irritable bowel syndrome (IBS) affect the function of enteric and extrinsic sensory nerves, which can contribute to the development of symptoms. Little is known about the effects of mucosal mediators on intestinal neuroplasticity. We investigated how these mediators affect the phenotypes of colonic mucosa nerve fibers, neuron differentiation, and fiber outgrowth. METHODS: We analyzed mucosal biopsy samples collected from 101 patients with IBS and 23 asymptomatic healthy individuals (controls). We measured levels of neuronal-specific enolase, growth-associated protein 43, nerve growth factor (NGF), and tyrosine kinase receptor A (NTRK1) by immunohistochemistry and enzyme-linked immunosorbent assay. Primary rat enteric neurons and human SH-SY5Y cells were incubated with supernatants from the mucosal biopsies and analyzed by morphometric and polymerase chain reaction analyses. RESULTS: Compared with mucosal tissues of controls, mucosa from patients with IBS had a significant increase in the area of lamina propria occupied by neuronal-specific enolase-positive (57.7% increase) and growth-associated protein 43-positive fibers (56.1% increase) and staining density of NGF (89.3% increase) (P < .05 for all). Levels of NGF protein were also increased in tissues from patients with IBS vs controls (18% increase; P = .16) along with levels of NTRK1 (64% increase; P < .05). Mucosal supernatants from tissues of patients with IBS induced higher levels of neuritogenesis in primary culture of enteric neurons, compared with controls, and more NGF-dependent neuronal sprouting in SH-SY5Y cells. CONCLUSIONS: Nerve fiber density and sprouting, as well as expression of NGF and NTRK1, are significantly increased in mucosal tissues of patients with IBS. Mucosal mediators participate to these neuroplastic changes.

Animal models of chemically induced intestinal inflammation: predictivity and ethical issues.

The debate about the ethical and scientific issues regarding the use of animals in research is mainly focused on these questions: a) whether preclinical studies in animals are still ethically acceptable; b) whether it is possible to establish more soundly their predictivity; c) what measures should be taken to reduce the clinical attrition often due to biased preclinical assessment of potential efficacy of new drugs. This review aims at a critical revision of animal models of chemically induced intestinal inflammation in drug development. These models, notwithstanding differences among species, still represent a major source of information about biological systems and can have undisputable translational value, provided that appropriate measures are taken to ensure that experiments are both scientifically and ethically justified. These measures include: a) more stringent application to preclinical experiments of standards used in clinical studies (such as sample size, randomization, inclusion/exclusion criteria, blinding); b) selection of the animal model after careful pathophysiological scrutiny bearing in mind inherent limitations of each model (e.g. acute self-limiting vs chronic disease, animal species, role of the intestinal immune system and microbiome); and c) experimental design duly considering the specific pharmacological profile of each agent to be screened (such as bioavailability, route of administration, full consideration of the pharmacological spectrum). In this perspective, the new European legislation is an opportunity to fully apply these standards so that in vivo animal models can provide an invaluable mean to study complex physiological and biochemical interactions, which cannot be completely simulated in silico and/or in vitro.

Barrier effect of Esoxx(®) on esophageal mucosal damage: experimental study on ex-vivo swine model.

The aim of the present study was to assess the potential barrier effect of Esoxx(®), a new nonprescription medication under development for the relief of gastroesophageal reflux symptoms. Esoxx is based on a mixture of hyaluronic acid and chondroitin sulfate in a bioadhesive suspension of Lutrol(®) F 127 polymer (poloxamer 407) which facilitates the product adhesion on the esophageal mucosa. The mucosal damage was induced by 15 to 90 minutes of perfusion with an acidic solution (HCl, pH 1.47) with or without pepsin (2000 U/mL, acidified to pH 2; Sigma-Aldrich). Mucosal esophageal specimens were histologically evaluated and Evans blue dye solution was used to assess the permeability of the swine mucosa after the chemical injury. The results show that: (1) esophageal mucosal damage is related to the perfusion time and to the presence of pepsin, (2) mucosal damage is associated with an increased permeability, documented by an evident Evans blue staining, (3) perfusion with Esoxx is able to reduce the permeability of the injured mucosa, even after saline washing of the swine esophagus. These preliminary results support further clinical studies of Esoxx in the topical treatment of gastroesophageal reflux symptoms.

Portal hypertension and liver cirrhosis in rats: effect of the ß3-adrenoceptor agonist SR58611A.

BACKGROUND AND PURPOSE: ß(3) -Adrenoceptors participate in the regulation of vascular tone in physiological and pathological conditions. We aimed to assess the effect of pharmacological modulation of ß(3) -adrenoceptors on portal pressure (PP) and systemic haemodynamics and their expression in the liver and mesenteric vessels of cirrhotic rats. EXPERIMENTAL APPROACH: PP, central venous pressure (CVP) and systemic haemodynamics were invasively assessed in control and CCl(4) -treated cirrhotic rats before and during infusion of the selective ß(3) -adrenoceptor agonist, SR58611A. Tissue samples were also collected from liver, heart, portal vein and mesenteric artery for immunohistochemistry and molecular biology analysis. The effect of SR58611A on isolated portal vein was assessed. KEY RESULTS: At baseline, cirrhotic rats showed portal hypertension, reduced CVP and hyperdynamic circulation. SR58611A induced a significant, dose-dependent decrease in PP in cirrhotic rats, but not in controls. Although both groups manifested a dose-dependent reduction in mean arterial pressure, this effect was associated with decreased cardiac index (CI) and unchanged indicized peripheral vascular resistance (PVRI) in cirrhotic rats and increased CI and decreased PVRI in control animals. Pretreatment with the selective ß(3) -adrenoceptor antagonist SR59230 prevented all SR58611A-induced changes in cirrhotic rats. SR58611A concentration-dependently relaxed portal vein in cirrhotic rats to a significantly greater extent than in healthy rats; pretreatment with SR59230A completely prevented SR58611A-induced cirrhotic portal vein relaxation. Finally, ß(3) -adrenoceptors were identified in the liver, heart and portal vein of cirrhotic and control animals; their expression was increased in cirrhotic rats. CONCLUSIONS AND IMPLICATIONS: ß(3) -Adrenoceptors are altered in portal hypertension of experimental cirrhosis and may represent a novel therapeutic target.

Intestinal serotonin release, sensory neuron activation, and abdominal pain in irritable bowel syndrome.

OBJECTIVES: Serotonin (5-hydroxytryptamine, 5-HT) metabolism may be altered in gut disorders, including in the irritable bowel syndrome (IBS). We assessed in patients with IBS vs. healthy controls (HCs) the number of colonic 5-HT-positive cells; the amount of mucosal 5-HT release; their correlation with mast cell counts and mediator release, as well as IBS symptoms; and the effects of mucosal 5-HT on electrophysiological responses in vitro. METHODS: We enrolled 25 Rome II IBS patients and 12 HCs. IBS symptom severity and frequency were graded 0-4. 5-HT-positive enterochromaffin cells and tryptase-positive mast cells were assessed with quantitative immunohistochemistry on colonic biopsies. Mucosal 5-HT and mast cell mediators were assessed by high-performance liquid chromatography or immunoenzymatic assay, respectively. The impact of mucosal 5-HT on electrophysiological activity of rat mesenteric afferent nerves was evaluated in vitro. RESULTS: Compared with HCs, patients with IBS showed a significant increase in 5-HT-positive cell counts (0.37 ± 0.16% vs. 0.56 ± 0.26%; P=0.039), which was significantly greater in patients with diarrhea-predominant IBS vs. constipation-predominant IBS (P=0.035). Compared with HCs, 5-HT release in patients with IBS was 10-fold significantly increased (P < 0.001), irrespective of bowel habit, and was correlated with mast cell counts. A significant correlation was found between the mucosal 5-HT release and the severity of abdominal pain (r(s)=0.582, P=0.047). The area under the curve, but not peak sensory afferent discharge evoked by IBS samples in rat jejunum, was significantly inhibited by the 5-HT3 receptor antagonist granisetron (P<0.005). CONCLUSIONS: In patients with IBS, 5-HT spontaneous release was significantly increased irrespective of bowel habit and correlated with mast cell counts and the severity of abdominal pain. Our results suggest that increased 5-HT release contributes to development of abdominal pain in IBS, probably through mucosal immune activation.

Proinflammatory role of vasopressin through V1b receptors in hapten-induced experimental colitis in rodents: implication in IBD.

Vasopressin and its receptors modulate several gut functions, but their role in intestinal inflammation is unknown. Our aims were to determine 1) the localization of V1b receptors in human and rodent colon, 2) the role of vasopressin and V1b receptors in experimental colitis using two approaches: V1b⁻(/)⁻ mice and a selective V1b receptor antagonist, SSR149415, and 3) the mechanisms involved. V1b receptors were localized in normal and inflamed colon from humans and rats. Experimental colitis was induced in rats and mice and some groups were treated before or after colitis induction with oral SSR149415 (3-30 mg/kg). Other groups of mice were submitted to dehydration to increase vasopressin plasma levels, prior to colitis induction. Body weight, damage scores, MPO, and TNF-α tissue levels were determined. Finally, colonic segments of wild-type (WT) and V1b⁻(/)⁻ mice were mounted in Ussing chambers and paracellular permeability in response to vasopressin was studied. V1b receptors were expressed in enterocytes and ganglia cells of the enteric nervous system of human and rat intestine. Expression levels were independent from inflammatory status. Colitis was less severe in rodents treated by either preventive or curative SSR149415 and in V1b⁻(/)⁻ mice. 2,4,6-Trinitrobenzene sulfonic acid induced a strong mortality in dehydrated animals that was reversed by preventive SSR149415 or mast cell stabilizer. Vasopressin significantly increased paracellular permeability in WT, but not in V1b⁻(/)⁻ mice. Preincubation of colon tissues with SSR149415 abolished the vasopressin effect. Similarly, vasopressin had no effect in colonic preparations from WT mice pretreated with mast cell stabilizers. Vasopressin, through V1b receptor interaction, has proinflammatory properties linked to mast cell activation and downstream alterations of the colonic epithelial barrier. These findings underline the potential interest of V1b receptor blockers in gut inflammatory diseases.

Non-peptidyl low molecular weight radical scavenger IAC attenuates DSS-induced colitis in rats.

AIM: To investigate the effects of the free radical scavenger bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate (IAC) in the dextran sodium sulphate (DSS) experimental model of ulcerative colitis. METHODS: Colitis was induced in Sprague Dawley male rats by administration of 5% DSS in drinking water. IAC (30 mg/kg, lipophilic or hydrophilic form) was administered daily (orally or ip) for 6 d until sacrifice. Colonic damage was assessed by means of indirect (Disease Activity Index score) and direct measures (macroscopic and microscopic scores) and myeloperoxidase (MPO) activity. Neutrophil infiltration within the tissue and glutathione S-transferase activity were also investigated. RESULTS: DSS-induced colitis impaired body weight gain and markedly increased all inflammatory parameters. Six-day treatment with lipophilic IAC significantly reduced intestinal damage caused by inflammation, induced a down-regulation in MPO activity (0.72 +/- 0.12 and 0.45 +/- 0.12 with lipophilic IAC po and ip, respectively, vs 1.10 +/- 0.27 in untreated DSS colitis animals) and minimized DSS-induced neutrophil infiltration, while hydrophilic IAC administered orally did not ameliorate DSS-induced damage. CONCLUSION: These results support the hypothesis that reactive oxygen metabolites contribute to inflammation and that the radical scavenger IAC has therapeutic potential in inflammatory bowel disease.

Anticancer drugs and cardiotoxicity: Insights and perspectives in the era of targeted therapy.

Drug-induced cardiotoxicity is emerging as an important issue among cancer survivors. For several decades, this topic was almost exclusively associated with anthracyclines, for which cumulative dose-related cardiac damage was the limiting step in their use. Although a number of efforts have been directed towards prediction of risk, so far no consensus exists on the strategies to prevent and monitor chemotherapy-related cardiotoxicity. Recently, a new dimension of the problem has emerged when drugs targeting the activity of certain tyrosine kinases or tumor receptors were recognized to carry an unwanted effect on the cardiovascular system. Moreover, the higher than expected incidence of cardiac dysfunction occurring in patients treated with a combination of old and new chemotherapeutics (e.g. anthracyclines and trastuzumab) prompted clinicians and researchers to find an effective approach to the problem. From the pharmacological standpoint, putative molecular mechanisms involved in chemotherapy-induced cardiotoxicity will be reviewed. From the clinical standpoint, current strategies to reduce cardiotoxicity will be critically addressed. In this perspective, the precise identification of the antitarget (i.e. the unwanted target causing heart damage) and the development of guidelines to monitor patients undergoing treatment with cardiotoxic agents appear to constitute the basis for the management of drug-induced cardiotoxicity.

The beta3-adrenoceptor as a therapeutic target: current perspectives.

beta(3)-Adrenoceptors (beta(3)-ARs) are located not only on the plasma membrane of both white and brown adipocytes, but also exist in human heart, gall bladder, gastrointestinal tract, prostate, urinary bladder detrusor, brain and in near-term myometrium. They are now recognized as an attractive target for drug discovery and several efforts have been made in this field to understand their function and regulation in different human tissues. The aim of this review is to highlight the functional role of beta(3)-ARs as well as to discuss their potential for drug development.

Effects of the non-peptidyl low molecular weight radical scavenger IAC in DNBS-induced colitis in rats.

Intestinal inflammation is accompanied by excessive production of reactive oxygen and nitrogen radical species because of the massive infiltration of polymorphonuclear and mononuclear leukocytes. Antioxidant compounds seem to protect against experimental colitis. Here we investigated the effects of the innovative non-peptidyl, low molecular weight radical scavenger bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate (IAC), which is highly reactive with most oxygen, nitrogen and carbon centred radicals and is easily distributed in cell membranes and intra-extra cellular compartments, in the DNBS model of colitis. Colitis was induced in male SD rats by intrarectal administration of DNBS (15 mg/rat). IAC (30 mg/kg b.w., hydrophilic or lipophilic form) was administered daily (orally or i.p.) starting from the day before the induction of colitis for 7 days (n=6-8 per group). Colonic damage was assessed by means of macroscopic and histological scores, myeloperoxidase activity (MPO) and TNF-alpha tissue levels. Colitis impaired body weight gain and markedly increased all inflammatory parameters. IAC significantly counteracted the reduction in body weight gain, decreased colonic damage and inflammation and TNF-alpha levels in DNBS-colitis. The antioxidant IAC significantly ameliorates experimental colitis in rats. This strengthens the notion that antioxidant compounds may have therapeutic potential in inflammatory bowel disease.

Protection from DNBS-induced colitis by the tachykinin NK(1) receptor antagonist SR140333 in rats.

Inflammation is known to be associated with changes in tachykinin expression both in human and animal models: substance P and NK(1) receptor expression are increased in patients with inflammatory bowel disease, and similar changes are reported in experimental models of inflammation. We investigated the effect of the tachykinin NK(1) receptor antagonist SR140333 (10 mg/kg orally) on 2,4-dinitrobenzene sulfonic acid (DNBS)-induced colitis in rats. Colonic damage was assessed by means of macroscopic and microscopic scores, myeloperoxidase activity (MPO) and TNF-alpha tissue levels on day 6 after induction of colitis. An enzyme immunoassay technique was used to measure colonic substance P levels. DNBS administration impaired body weight gain and markedly increased all inflammatory parameters as well as colonic tissue levels of substance P. Treatment with SR140333 significantly counteracted the impairment in body weight gain, decreased macroscopic and histological scores and reduced colonic myeloperoxidase activity and TNF-alpha tissue levels. Colonic tissue levels of substance P were also reduced by SR140333, although this effect did not reach statistical significance. In conclusion, treatment with SR140333 protects from DNBS-induced colitis in rats. These results suggest a role for NK(1) receptors and substance P in the development of intestinal inflammation and indicate tachykinin receptors as a potential pharmacological target in the treatment of inflammatory bowel disease.

The hERG K+ channel: target and antitarget strategies in drug development.

The human ether-à-go-go related gene (hERG) K+ channel is of great interest for both basic researchers and clinicians because its blockade by drugs can lead to QT prolongation, which is a risk factor for torsades de pointes, a potentially life-threatening arrhythmia. A growing list of agents with "QT liability" have been withdrawn from the market or restricted in their use, whereas others did not even receive regulatory approval for this reason. Thus, hERG K+ channels have become a primary antitarget (i.e. an unwanted target) in drug development because their blockade causes potentially serious side effects. On the other hand, the recent identification and functional characterization of hERG K+ channels not only in the heart, but also in several other tissues (e.g. neurons, smooth muscle and cancer cells) may have far reaching implications for drug development for a possible exploitation of hERG as a target, especially in oncology and cardiology.

Intestinal effects of nonselective and selective cyclooxygenase inhibitors in the rat.

It is now widely recognized that nonsteroidal anti-inflammatory drugs (NSAIDs) may cause extensive damage to the intestine. The pathogenesis of NSAID-induced intestinal injury, however, is still controversial and both local irritant actions and cyclooxygenase (COX) inhibition have been proposed as underlying mechanisms. In this study we investigated further on NSAID-induced intestinal damage by using nonselective (indomethacin and ibuprofen), COX-1 selective (SC-560) or COX-2 selective (celecoxib) inhibitors. NSAIDs were administered orally to conscious rats and small intestinal injury was evaluated 24 h afterwards in terms of macroscopic and microscopic alterations, myeloperoxidase activity, lipid peroxidation, number of enterobacteria in the mucosa and epithelial mucin content. Oral administration of indomethacin (20 mg/kg) induced macroscopic and microscopic damage to the small intestine, increased translocation of enterobacteria from lumen into the mucosa, myeloperoxidase activity and lipid peroxidation. Ibuprofen (120 mg/kg), SC-560 (20 mg/kg), celecoxib (60 mg/kg) or the combination of SC-560 plus celecoxib did not cause any intestinal injury nor modified the number of bacteria in mucosal homogenates. SC-560 significantly increased both myeloperoxidase activity and lipid peroxidation, whereas celecoxib significantly reduced myeloperoxidase levels, while leaving unaltered lipid peroxidation. Finally, all NSAIDs, mostly indomethacin, increased neutral mucins and decreased acidic mucins in the intestinal goblet cells. These results indicate that inhibition of cyclooxygenase, although variably influencing mucosal integrity homeostasis, is not sufficient to initiate acute intestinal damage in rats. Moreover, topical mucosal injury induced by the NSAID molecule seems to be a critical factor in the development of intestinal injury.

Enteric neuroplasticity evoked by inflammation.

Neuroplastic changes in the enteric nervous system (ENS) may be observed in physiological states, such as development and aging, or occur as a consequence of different pathological conditions, ranging from enteric neuropathies (e.g., Hirschsprung's disease) to intestinal (e.g., inflammatory bowel disease) or extra-intestinal diseases (e.g., Parkinson's disease). Studying ENS plasticity may help to elucidate the pathophysiology of several diseases and have a bearing on the development of new pharmacological interventions. In the present review, we would like to focus on neuronal plasticity evoked by gastrointestinal inflammation occurring in inflammatory bowel disease and in a subset of patients with severe derangement of gut motility due to an enteric neuropathy characterized by an inflammatory infiltrate of the enteric plexuses. Major features of neuroplasticity within the enteric microenvironment encompass structural abnormalities ranging from nerve re-arrangement (e.g., hypertrophy and hyperplasia) to degeneration and loss of enteric ganglion cells; altered synthesis, content and release of neurotransmitters as well as up- or down-regulation of receptor systems; gastrointestinal dysfunction characterized by sensory-motor and secretory impairment of the gut. Interestingly, neuronal changes may also occur in segments of the gastrointestinal tract remote from the site of the original inflammation, e.g. the ileum may show neuroplastic changes during colitis. Sometimes, the inflamed site may even be outside the gut. Among potential mechanisms underlying ENS plasticity, neurotrophins and enteric glia deserve special attention. A better comprehension of ENS plasticity during inflammation could be instrumental to develop new therapeutic options for patients with IBD and inflammatory enteric neuropathies.

Antibacterial macrolides: a drug class with a complex pharmacological profile.

Macrolides are widely used antibacterial agents. Although generally well tolerated, they have a number of important additional pharmacological effects, which can sometimes result in significant adverse reactions. This review focuses on three of these side effects: the prokinetic action associated with stimulation of motilin receptors, the proarrhythmic effect due to prolongation of the QT interval of the electrocardiogram and the potential for drug interactions due to inhibition of drug metabolising enzymes. For macrolides that have obtained marketing authorisation in Italy, United Kingdom or United States of America, we also considered whether these actions are properly reported in the approved summaries of the product characteristics and tried to provide strategies to identify patients at risk of significant side effects when macrolides are administered.

Prokinetics in the treatment of acute intestinal pseudo-obstruction.

Acute colonic pseudo-obstruction (Ogilvie's syndrome) is characterized by an acute obstruction of the large bowel that is unrelated to mechanical causes. The evidence that cholinesterase inhibitors are effective in relieving acute colonic pseudo-obstruction raised interest in the pharmacological management of this condition. This review analyzes the pharmacological treatment of patients with Ogilvie's syndrome. Intravenous neostigmine is the best pharmacological treatment, leading to rapid colonic decompression. New colokinetic agents, including 5-HT(4) receptor agonists and motilides, may represent other useful therapeutic options for Ogilvie's syndrome.