Luminal regulation of normal and neoplastic human EC cell serotonin release is mediated by bile salts, amines, tastants, and olfactants.
Mechanisms by which gut luminal content regulates secretion and motility are ill understood. We evaluated whether neuroendocrine enterochromaffin (EC) cells act as luminal sensors for a wide variety of nutrients and defined the secretory mechanisms of this process. Pure (98-99%) FACS-sorted human EC cells and neoplastic EC cells (KRJ-I) were studied. RT-PCR identified transcripts for T2R1 (bitter), OR1G1 (class II olfactory) and trace amine (TAR1) G protein-coupled receptors (GPCRs) and transporters for glutamine (SNAT1/2), glucose (GLUT1/3/SGLT1), and bile salts (ABST). Glutamine and sodium deoxycholate stimulated 5-HT release (EC(50) = 0.002-0.2 microM; 2-fold release) but were 10-100 times more potent in neoplastic EC cells, which also secreted 6-13 times more 5-HT. Tastants (caffeine, tyramine, octopamine) and olfactants (thymol and eugenol) also stimulated normal and neoplastic EC cell 5-HT secretion (EC(50) = 1.2 nM to 2.1 microM and 0.05 nM to 0.1 microM release, respectively); 2-deoxyglucose and the artificial sweetener sucralose also stimulated (EC(50) = 9.2 and 0.38 nM). 5-HT release was associated with ERK phosphorylation (1.5-fold, P < 0.02) and could be inhibited by a somatostatin analog (IC(50) = 1 pM). Eleven secretory associated genes including the vesicle docking inhibitor STXBP3 were upregulated in response to glutamine and bile salt stimulation in neoplastic EC cells. Targeting STXBP3 expression by use of antisense knockdown significantly (P < 0.05) reduced 5-HT secretion. In conclusion, EC cells express GPCRs and transporters for luminal tastants, olfactants, glutamine, glucose, and bile salts. Activation includes a panel of secretory genes, ERK phosphorylation, and 5-HT secretion. Luminal EC cell regulation is likely to be as important as G cell regulation in gastric acid secretion; development of agents to target EC cell function is therefore a critical therapeutic goal.
1Gastrointestinal Pathobiology Research Group, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Mark
M
Kidd
Irvin M
IM
Modlin
Bjorn I
BI
Gustafsson
Ignat
I
Drozdov
Oyvind
O
Hauso
Roswitha
R
Pfragner
D026924:Amino Acid Transport System A / Q000502:physiology; D001647:Bile Acids and Salts / Q000502:physiology*; D002110:Caffeine / Q000494:pharmacology; D002276:Carcinoid Tumor / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003840:Deoxycholic Acid / Q000494:pharmacology; D003847:Deoxyglucose / Q000494:pharmacology; D004759:Enterochromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D051246:Glucose Transport Proteins, Facilitative / Q000502:physiology; D005973:Glutamine / Q000494:pharmacology; D006801:Humans; D007414:Intestinal Neoplasms / Q000235:genetics / Q000378:metabolism*; D007421:Intestine, Small; D029363:Organic Anion Transporters, Sodium-Dependent / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology; D018035:Receptors, Odorant / Q000502:physiology; D012701:Serotonin / Q000378:metabolism*; D051269:Sodium-Glucose Transporter 1 / Q000502:physiology; D013004:Somatostatin / Q000494:pharmacology; D013395:Sucrose / Q000031:analogs & derivatives / Q000494:pharmacology; D027981:Symporters / Q000502:physiology; D014443:Tyrosine / Q000494:pharmacology; D000098706:Taste Receptors, Type 2; D000095383:Trace Amine-Associated Receptors
D026924:Amino Acid Transport System A; D001647:Bile Acids and Salts; D002110:Caffeine; D003840:Deoxycholic Acid; D003847:Deoxyglucose; D048049:Extracellular Signal-Regulated MAP Kinases; D051246:Glucose Transport Proteins, Facilitative; D005973:Glutamine; D029363:Organic Anion Transporters, Sodium-Dependent; D043562:Receptors, G-Protein-Coupled; D018094:Receptors, Metabotropic Glutamate; D018035:Receptors, Odorant; D012701:Serotonin; D051269:Sodium-Glucose Transporter 1; D013004:Somatostatin; D013395:Sucrose; D027981:Symporters; D014443:Tyrosine; D000098706:Taste Receptors, Type 2; D000095383:Trace Amine-Associated Receptors; C498797:SLC38A2 protein, human; C495674:SLC5A1 protein, human; C431926:taste receptors, type 1; C071908:sodium-bile acid cotransporter; C026285:trichlorosucrose; C108823:metabotropic glutamate receptor 4