The role of mechanical forces and adenosine in the regulation of intestinal enterochromaffin cell serotonin secretion

• Published in: American journal of physiology: Gastrointestinal and liver physiology Vol. 302; no. 3; p. G397
• Main Authors: Chin, A, Svejda, B, Gustafsson, B I, Granlund, A B, Sandvik, A K, Timberlake, A, Sumpio, B, Pfragner, R, Modlin, I M, Kidd, M
• Format: Journal Article
• Language: English
• Published: United States 01-02-2012
• Subjects: Acetamides - pharmacology; Adenosine - pharmacology; Adenosine A2 Receptor Agonists - pharmacology; Adenosine A2 Receptor Antagonists - pharmacology; Adenosine-5'-(N-ethylcarboxamide) - pharmacology; Adult; Aged; Cell Line, Tumor; Cells, Cultured; Colon - cytology; Crohn Disease - metabolism; Cyclic AMP - metabolism; Cyclic AMP Response Element-Binding Protein - metabolism; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases - metabolism; Enterochromaffin Cells - drug effects; Enterochromaffin Cells - metabolism; Enterochromaffin Cells - secretion; Female; Gene Expression - genetics; Humans; Male; MAP Kinase Kinase 1 - antagonists & inhibitors; MAP Kinase Kinase 1 - metabolism; MAP Kinase Signaling System - drug effects; MAP Kinase Signaling System - physiology; Mechanotransduction, Cellular - drug effects; Mechanotransduction, Cellular - physiology; Middle Aged; Phosphorylation - drug effects; Proto-Oncogene Proteins c-akt - antagonists & inhibitors; Proto-Oncogene Proteins c-akt - metabolism; Purines - pharmacology; Receptor, Adenosine A1 - genetics; Receptor, Adenosine A2A - genetics; Receptor, Adenosine A2B - genetics; Receptor, Adenosine A2B - metabolism; Receptor, Adenosine A3 - genetics; Serotonin - secretion; Signal Transduction - drug effects; Signal Transduction - physiology; Stress, Mechanical; Tryptophan Hydroxylase - genetics; Tryptophan Hydroxylase - metabolism; Vesicular Monoamine Transport Proteins - metabolism
• ISSN: 1522-1547
• DOI: 10.1152/ajpgi.00087.2011

Enterochromaffin (EC) cells of the diffuse neuroendocrine cell system secrete serotonin (5-HT) with activation of gut motility, secretion, and pain. These cells express adenosine (ADORA) receptors and are considered to function as mechanosensors. Physiological pathways mediating mechanosensitivity and adenosine responsiveness remain to be fully elucidated, as do their roles in inflammatory bowel disease (IBD) and neoplasia. Pure (98-99%) FACS-sorted normal and IBD human EC cells and neoplastic EC cells (KRJ-I) were studied. IBD-EC cells and KRJ-I overexpressed ADORA2B. NECA, a general ADORA receptor agonist, stimulated, whereas the A2B receptor antagonist MRS1754 inhibited, 5-HT release (EC50 = 1.8 × 10-6 M; IC50 = 3.7 × 10-8 M), which was associated with corresponding alterations in intracellular cAMP levels and pCREB (Ser133). Mechanical stimulation using a rhythmic flex model induced transcription and activation of Tph1 (tryptophan hydroxylase) and VMAT₁ (vesicular monoamine transporter 1) and the release of 5-HT, which could be inhibited by MRS1754 and amplified by NECA. Secretion was also inhibited by H-89 (PKA inhibitor) while Tph1 and VMAT₁ transcription was regulated by PKA/MAPK and PI₃K-mediated signaling. Normal and IBD-EC cells also responded to NECA and mechanical stimulation with PKA activation, cAMP production, and 5-HT release, effects reversible by MRS1754. EC cells express stimulatory ADORA2B, and rhythmic stretch induces A2B activation, PKA/MAPK/IP3-dependent transcription, and PKA-dependent secretion of 5-HT synthesis and secretion. Receptor expression is amplified in IBD and neoplasia, and 5-HT release is increased. Determination of factors that regulate EC cell function are necessary for understanding its role as a mechanosensory cell and to facilitate the development of agents that can selectively target cell function in EC cell-associated disease.