Deborah Sacco

Involvement of the P2X7 purinergic receptor in colonic motor dysfunction associated with bowel inflammation in rats.

Background and Purpose Recent evidence indicates an involvement of P2X7 purinergic receptor (P2X7R) in the fine tuning of immune functions, as well as in driving enteric neuron apoptosis under intestinal inflammation. However, the participation of this receptor in the regulation of enteric neuromuscular functions remains undetermined. This study was aimed at investigating the role of P2X7Rs in the control of colonic motility in experimental colitis. Experimental Approach Colitis was induced in rats by 2,4-dinitrobenzenesulfonic acid. P2X7R distribution was examined by immunofluorescence analysis. The effects of A804598 (selective P2X7R antagonist) and BzATP (P2X7R agonist) were tested on contractions of longitudinal smooth muscle evoked by electrical stimulation or by carbachol in the presence of tetrodotoxin. Key Results P2X7Rs were predominantly located in myenteric neurons, but, in the presence of colitis, their expression increased in the neuromuscular layer. In normal preparations, A804598 elicited a negligible increase in electrically induced contractions, while a significant enhancement was recorded in inflamed tissues. In the presence of Nω-propyl-L-arginine (NPA, neuronal nitric oxide synthase inhibitor) the A804598 effects were lost. P2X7R stimulation with BzATP did not significantly affect electrical-induced contractions in normal colon, while a marked reduction was recorded under inflammation. The inhibitory effect of BzATP was antagonized by A804598, and it was also markedly blunted by NPA. Both P2X7R ligands did not affect carbachol-induced contractions. Conclusions and Implications The purinergic system contributes to functional neuromuscular changes associated with bowel inflammation via P2X7Rs, which modulate the activity of excitatory cholinergic nerves through a facilitatory control on inhibitory nitrergic pathways.

The AMPK enzyme-complex: from the regulation of cellular energy homeostasis to a possible new molecular target in the management of chronic inflammatory disorders

Introduction: Adenosine monophosphate-activated protein kinase (AMPK), known as an enzymatic complex that regulates the energetic metabolism, is emerging as a pivotal enzyme and enzymatic pathway involved in the regulation of immune homeostatic networks. It is also involved in the molecular mechanisms underlying the pathophysiology of chronic inflammatory diseases. Areas covered: AMPK is expressed in several immune cell types including macrophages, lymphocytes, neutrophils and dendritic cells, and governs a broad array of cell functions, which include cytokine production, chemotaxis, cytotoxicity, apoptosis and proliferation. Based on its wide variety of immunoregulatory actions, the AMPK system has been targeted to reveal its impact on the course of immune-related diseases, such as atherosclerosis, psoriasis, joint inflammation and inflammatory bowel diseases. Expert opinion: The identification of AMPK subunits responsible for specific anti-inflammatory actions and the understanding of the underlying molecular mechanisms will promote the generation of novel AMPK activators, endowed with improved pharmacodynamic and pharmacokinetic profiles. These new tools will aid us to utilize AMPK pathway activation in the management of acute and chronic inflammatory diseases, while minimizing potential adverse reactions related to the effects of AMPK on metabolic energy.

Small bowel protection against NSAID-injury in rats: Effect of rifaximin, a poorly absorbed, GI targeted, antibiotic

Nonsteroidal anti-inflammatory drugs, besides exerting detrimental effects on the upper digestive tract, can also damage the small and large intestine. Although the underlying mechanisms remain unclear, there is evidence that enteric bacteria play a pivotal role. The present study examined the enteroprotective effects of a delayed-release formulation of rifaximin-EIR (R-EIR, 50mg/kg BID, i.g.), a poorly absorbed antibiotic with a broad spectrum of antibacterial activity, in a rat model of enteropathy induced by indomethacin (IND, 1.5mg/kg BID for 14 days) administration. R-EIR was administered starting 7 days before or in concomitance with IND administration. At the end of treatments, blood samples were collected to evaluate hemoglobin (Hb) concentration (as an index of digestive bleeding). Small intestine was processed for: (1) histological assessment of intestinal damage (percentage length of lesions over the total length examined); (2) assay of tissue myeloperoxidase (MPO) and TNF levels, as markers of inflammation; (3) assay of tissue malondialdehyde (MDA) and protein carbonyl concentrations, as an index of lipid and protein peroxidation, respectively; (4) evaluation of the major bacterial phyla. IND significantly decreased Hb levels, this effect being significantly blunted by R-EIR. IND also induced the occurrence of lesions in the jejunum and ileum. In both intestinal regions, R-EIR significantly reduced the percentage of lesions, as compared with rats receiving IND alone. Either the markers of inflammation and tissue peroxidation were significantly increased in jejunum and ileum from IND-treated rats. However, in rats treated with R-EIR, these parameters were not significantly different from those observed in controls. R-EIR was also able to counterbalance the increase in Proteobacteria and Firmicutes abundance induced by INDO. To summarize, R-EIR treatment significantly prevents IND-induced intestinal damage, this enteroprotective effect being associated with a decrease in tissue inflammation, oxidative stress and digestive bleeding as well as reversal of NSAID-induced alterations in bacterial population.

SACCHAROMYCES BOULARDIIREDUCES THE SEVERITY OF HERPES SIMPLEX VIRUS TYPE 1- INDUCED GASTROINTESTINAL DYSFUNCTION

INTRODUCTION: WOPN is a frequent sequel of acute necrotizing pancreatitis. The best approach for drainage of these collections is still controversial. We present our retrospective data comparing the two endoscopic methods for drainage of WOPN. AIMS & METHODS: Outcomes of patients undergoing EUS guided transmural drainage (EUTMD) using a newly designed fully covered large-bore wide-flare metal stent (Nagi stent) (Gr I) were compared to the outcomes of patients who underwent placement of multiple plastic stents (Gr II). The pre-op CECT confirmed suitability of endoscopic drainage based on location, wall thickness & contents. Visual quantification of necrosis (450% solid debris) by EUS excluded 8 patients (3 in Gr I and 5 in Gr. II). The procedure in both groups is done by standard technique by a single endoscopist. The difference between the two groups was tract dilatation (6 mm in Gr I vs. 18 mm in Gr II). Placement of NCT and subsequent necrosectomy was done whenever necessary. Follow-up imaging was done at 72 hrs and thereafter at 2, 4, & 6 weeks. The outcomes were compared in terms of clinical success, need for surgery, complications, hospital stay and mortality. RESULTS:N: 21(Gr. I), 61(Gr. II). The two groups were comparable in terms of demographics, etiology of pancreatitis, cyst location, size and amount of debris. Placement of NCT, need of necrosectomy and no of sessions required were also not different between the two groups. Clinical success defined as resolution of symptoms was seen in 100% of Gr. I patients vs. 73% in Gr. II (p1⁄4 0.048). None of the patients in Gr I required subsequent surgery vs 20/61 (32.7%) in Gr. II (p1⁄4 0.025). Complications: 15% in Gr. I vs 37% in Gr. II (p1⁄4 0.016) Mean hospital stay was 4 days (1-33) in Gr. I vs 8 (4-65) in Gr II (p1⁄4 0.012). Mortality was none in Gr. I vs. 6.5% (4/61) in Gr. II (p1⁄4 0.22) CONCLUSION: The Nagi stent is effective and safe for EUTMD of WOPN. It permits rapid clinical resolution with 100% technical and clinical success rates. It offers distinct advantage over plastic stents although further prospective studies are warranted. Disclosure of Interest: None declared

Alterations of colonic cholinergic and tachykininergic motility in a rat model of Parkinson’s Disease

Objective: In gastrointestinal diseases, drug discovery targeting 5-HT receptors has been developed focusing on antiemetic and treatment for irritable bowel syndrome targeting 5-HT3 receptors and on gastrointestinal motility activation targeting 5-HT4 receptors. Recently, we found a new pharmacological activity mediated 5-HT receptors showing actions of neural regeneration and neurogenesis. Methods: In this study, we are focusing on promoting effect of 5-HT4 receptor-activation on in vivo neural regeneration and neurogenesis in rodent rectal transection and anastomosis (RTA) and intestinal transection and anastomosis (ITA) models. Results: In rat and guinea-pig RTA models, local and oral treatment with mosapride citrate (10–100 l mol L) promoted enteric neural regeneration and neurogenesis at the anastomotic site from neural stem cells for 2 weeks after the surgery. In mouse ITA model, oral treatment with mosapride citrate (100 l mol L) promoted enteric neural regeneration and neurogenesis at the anastomotic site for 1 week after the surgery. Especially, in guinea pig model, the recovery of rectal distension-induced internal anal sphincter (IAS) relaxation reflex response was found for 2 weeks after the surgery. 5-HT4 receptor antagonists, GR113808 (10 l mol L) and SB 207266 (10–50 l mol L) suppressed 5-HT4 receptor activation induced neural regeneration and neurogenesis, and the recovery of IAS relaxation reflex response. In addition, we found mosapride citrate enhanced mobilization of neural stem cells by subcutaneous transplantation of gel sponge experiments in rats. This effect contributes to in vivo neural regeneration and neurogenesis. Furthermore, we confirmed transplanted embryonic neural stem cells of central nervous system from tail vein mobilized at the anastomotic site in mouse ITA model with oral application of mosapride for 1 week. Conclusion: Drug discovery based on the evidence of the present study will propose the possibility contributing to pharmacotherapy for defecation dysfunction after surgery and gastrointestinal motility dysfunction due to decreased enteric neurons in diabetic patients, pseudo-Hirschsprung’s disease patients and elders. 002 Mechanosensitive myenteric neurons in the guinea pig gastric corpus G. MAZZUOLI and M. SCHEMANN Techn. Universität München, Inst. für Human Biologie, Freising, Germany, and TU Munich, Human Biology, Freising, Germany