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IL1β- and LPS-induced serotonin secretion is increased in EC cells derived from Crohn’s disease


Mark Kidd PhD, Department of Surgery, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
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Abstract  Gut mucosal enterochromaffin (EC) cells are regarded as key regulators of intestinal motility and fluid secretion via secretion of serotonin (5HT), are increased in numbers in mucosal inflammation and located in close proximity to immune cells. We examined whether interleukin (IL)1β and Escherichia coli lipopolysaccharide (LPS) induced EC cell 5HT release through Toll-like/IL-1 (TIL) receptor activation, nuclear factor kappa B (NFκB) and mitogen-activated protein kinase (MAPK) phosphorylation and evaluated whether somatostatin could inhibit this phenomenon. Pure (>98%) human intestinal EC cells were isolated by fluorescent activated cell sorting from preparations of normal (= 5) and Crohn’s colitis (= 6) mucosa. 5HT release was measured (ELISA), and NFκB and ERK phosphorylation quantitated (ELISA) in response to IL1β and LPS. 5HT secretion was increased by both E. coli LPS (EC50 = 5 ng mL−1) and IL1β (EC50 = 0.05 pmol L−1) >2-fold (< 0.05) in Crohn’s EC cells compared with normal EC cells. Secretion was reversible by the TLR4 antagonist, E. coli K12 LPS (IC50 = 12 ng mL−1) and the IL1β receptor antagonist (ILRA; IC50 = 3.4 ng mL−1). IL1β caused significant (< 0.05) NFκB and MAPK phosphorylation (40–55%). The somatostatin analogue, lanreotide inhibited IL1β-stimulated secretion in Crohn’s (IC50 = 0.61 nmol L−1) and normal EC cells (IC50 = 1.8 nmol L−1). Interleukins (IL1β) and bacterial products (E. coli LPS) stimulated 5HT secretion from Crohn’s EC cells via TIL receptor activation (TLR4 and IL1β). Immune-mediated alterations in EC cell secretion of 5HT may represent a component of the pathogenesis of abnormal bowel function in Crohn’s disease. Inhibition of EC cell-mediated 5HT secretion may be an alternative therapeutic strategy in the amelioration of inflammatory bowel disease symptomatology.