Serotonin mechanisms in heart valve disease II: the 5-HT2 receptor and its signaling pathway in aortic valve interstitial cells.
Serotonin [5-hydroxytryptamine (5-HT)]-mediated cardiac valvular disease has been commonly observed in patients with carcinoid tumors. Previous research by others using reverse transcriptase-polymerase chain reaction demonstrated that aortic valve cells expressed predominantly 5-HT(2A/2B) receptors (5-HT(2A)R). Related investigations by our group using sheep aortic valve interstitial cell (SAVIC) cultures demonstrated that 5-HT both up-regulates transforming growth factor (TGF)-beta1 expression and activity, and also results in increased phospholipase C (PLC) activity. Thus, the present study investigated the hypothesis that the 5-HT signaling pathway in SAVICs involves 5-HT(2)Rs with associated G-protein signal transduction. The objectives were to functionally characterize in SAVIC cultures the native serotonin receptor subtypes using specific agonists and antagonists, and to delineate the serotonin-signaling pathway. 5-HT administration caused a marked stimulation of PLC activity. SAVIC studies of specific agents that target the 5-HT(2)R subtypes indicate that this response seemed to be mediated predominantly by 5-HT(2A)Rs. Furthermore, the sheep 5-HT(2A)R was identified by reverse transcriptase-polymerase chain reaction with sequence confirmation including comparisons to pig and human 5-HT(2A)R. Extracellular signal-regulated kinase (Erk 1/2) is a signaling molecule downstream from the 5-HT(2A)R. Both a protein kinase C inhibitor, GF109203X, and a Src inhibitor, PP1, attenuated 5-HT-stimulated Erk 1/2 activation. However, a 5-HT(2A)R antagonist, MDL 100907, inhibited 5-HT up-regulation of PLC and TGF-beta1, while having far less pronounced effects on Erk 1/2. In conclusion, these studies of the signal transduction activity of SAVICs in response to 5-HT have demonstrated that the 5-HT(2A)Rs are the most functionally active of the 5-HT(2)Rs in this cell type. Furthermore, 5-HT(2A)Rs are also involved in 5-HT up-regulation of active TGF-beta. 5-HT also mediated strong Erk 1/2 signaling via the MAP-kinase pathway, which was only in part because of 5-HT(2A)R activity. Thus, major 5-HT Erk 1/2 signaling beyond that controlled by 5-HT(2)Rs must involve other serotonin receptor types and/or secondary signaling events.
Xu
Jie
J
Cardiology Research Laboratory, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Jian
Bo
B
Chu
Richard
R
Lu
Zhibin
Z
Li
Quanyi
Q
Dunlop
John
J
Rosenzweig-Lipson
Sharon
S
McGonigle
Paul
P
Levy
Robert J
RJ
Liang
Bruce
B
D000818:Animals; D001021:Aortic Valve / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D005260:Female; D005464:Fluorobenzenes / Q000494:pharmacology; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin / Q000378:metabolism*; D016415:Sequence Alignment; D012701:Serotonin / Q000378:metabolism / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D012756:Sheep; D015398:Signal Transduction / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D005464:Fluorobenzenes; D010880:Piperidines; D011720:Pyrazoles; D011743:Pyrimidines; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; C079049:volinanserin