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  • Title: Cross talk between endothelial and smooth muscle cells in pulmonary hypertension: critical role for serotonin-induced smooth muscle hyperplasia.
    Author: Eddahibi S, Guignabert C, Barlier-Mur AM, Dewachter L, Fadel E, Dartevelle P, Humbert M, Simonneau G, Hanoun N, Saurini F, Hamon M, Adnot S.
    Journal: Circulation; 2006 Apr 18; 113(15):1857-64. PubMed ID: 16606791.
    Abstract:
    BACKGROUND: The mechanism of pulmonary artery smooth muscle cell (PA-SMC) hyperplasia in idiopathic pulmonary artery hypertension (iPH) may involve both an inherent characteristic of PA-SMCs and abnormal control by external stimuli. We investigated the role of pulmonary microvascular endothelial cells (P-ECs) in controlling PA-SMC growth. METHODS AND RESULTS: Serum-free medium of quiescent P-ECs elicited marked PA-SMC proliferation, and this effect was greater with P-ECs from patients with iPH than from control subjects and greater with PA-SMCs from these patients than from control subjects. Fluoxetine, which inhibits serotonin-induced mitogenesis by blocking the serotonin transporter, and p-chlorophenylalanine, which inhibits serotonin synthesis by blocking tryptophan hydroxylase (TPH), caused a similar 60% reduction in the growth-promoting effect of P-EC media, whereas endothelin receptor blockers had no effect. Assays of TPH activity in P-EC medium based on p-chlorophenylalanine-sensitive 5-hydroxytryptophan accumulation or serotonin determination indicated serotonin synthesis by P-ECs and an increase in this TPH-dependent process in iPH. Expression of the tph1 gene encoding the peripheral form of the TPH enzyme was increased in lungs and P-ECs from patients with iPH. Lung TPH1 immunostaining was confined to the pulmonary vessel intima. CONCLUSIONS: P-ECs produce paracrine factors governing PA-SMC growth. Serotonin, the main P-EC-derived growth factor, is overproduced in iPH and contributes to PA-SMC hyperplasia.
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