title: Serotonin provides an accessory signal to enhance T-cell activation by signaling through the 5-HT7 receptor.
abstract: Although typically considered a neurotransmitter, there is substantial evidence that serotonin (5-HT) plays an important role in the pathogenesis of inflammatory disorders. Despite these findings, the precise role of 5-HT in modulating immune function, particularly T-cell function, remains elusive. We report that naive T cells predominantly express the type 7 5-HT receptor (5-HTR), and expression of this protein is substantially enhanced on T-cell activation. In addition, T-cell activation leads to expression of the 5-HT(1B) and 5-HT(2A) receptors. Significantly, exogenous 5-HT induces rapid phosphorylation of extracellular signal-regulated kinase-1 and -2 (ERK1/2) and IkappaBalpha in naive T cells. 5-HT-induced activation of ERK1/2 and NFkappaB is inhibited by preincubation with a specific 5-HT(7) receptor antagonist. Thus, 5-HT signaling via the 5-HT(7) receptor may contribute to early T-cell activation. In turn, 5-HT synthesized by T cells may act as an autocrine factor. Consistent with this hypothesis, we found that inhibition of 5-HT synthesis with parachlorophenylalanine (PCPA) impairs T-cell activation and proliferation. Combined, these data demonstrate a fundamental role for 5-HT as an intrinsic cofactor in T-cell activation and function and suggest an alternative mechanism through which immune function may be regulated by indoleamine 2,3-dioxygenase-mediated catabolism of tryptophan.
authors.affiliation: Robarts Research Institute, 100 Perth Drive, London, Ontario, Canada.
authors.forename: Matilde
authors.initials: M
authors.lastname: León-Ponte
authors.forename: Gerard P
authors.initials: GP
authors.lastname: Ahern
authors.forename: Peta J
authors.initials: PJ
authors.lastname: O'Connell
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D010134:Fenclonine / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D020672:I-kappa B Proteins / Q000276:immunology / Q000378:metabolism; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000276:immunology / Q000378:metabolism; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000276:immunology / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000276:immunology / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000276:immunology; D044302:Receptor, Serotonin, 5-HT1B / Q000096:biosynthesis / Q000276:immunology; D011985:Receptors, Serotonin / Q000276:immunology* / Q000378:metabolism; D012701:Serotonin / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism
chemical_list: D020672:I-kappa B Proteins; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase; C000606205:Nfkbia protein, mouse; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; C104425:serotonin 7 receptor; D000072000:NF-KappaB Inhibitor alpha; D012701:Serotonin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010134:Fenclonine