PMID- 16195541 OWN - NLM STAT- MEDLINE DCOM- 20060223 LR - 20211203 IS - 1044-1549 (Print) IS - 1535-4989 (Electronic) IS - 1044-1549 (Linking) VI - 34 IP - 2 DP - 2006 Feb TI - Serotonin-induced growth of pulmonary artery smooth muscle requires activation of phosphatidylinositol 3-kinase/serine-threonine protein kinase B/mammalian target of rapamycin/p70 ribosomal S6 kinase 1. PG - 182-91 AB - We have previously found that both mitogen-activated protein kinase (MAPK)- and Rho kinase (ROCK)-related signaling pathways are necessary for the induction of pulmonary artery smooth muscle cell (SMC) proliferation by serotonin (5-hydroxytryptamine [5-HT]). In the present study, we investigated the possible additional participation of a phosphatidylinositol 3-kinase (PI3K)/serine-threonine protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (S6K1) pathway in this growth response. We found transient activation of Akt (Ser473) and more prolonged activation of S6K1 by 5-HT. Inhibition of PI3K with Wortmannin and LY294002 completely blocked these activations, but not that of MAPK or the ROCK substrate myosin phosphatase targeting subunit. Similarly, inhibition of MAPK and ROCK failed to block the Akt activation. Inhibition of Akt with NL-71-101 and downregulation of Akt expression with Akt small interfering RNA blocked 5-HT-induced S6K1 phosphorylation. Wortmannin, LY294002, and NL-71-101 dose-dependently inhibited 5-HT-induced SMC proliferation. 5-HT stimulated mTOR phosphorylation and the mTOR inhibitor, rapamycin, blocked activations of S6K1 and S6 ribosomal protein, and inhibited 5-HT-induced SMC proliferation. Akt phosphorylation and cell proliferation were also blocked by the antioxidants, N-acetyl-l-cysteine, Ginko biloba 501, and tiron, the reduced nicotinamide adenine dinucleotide phosphate oxidase inhibitor, diphenyleneiodonium, and the 5-HT2 receptor antagonists ketanserin and mianserin, but not by the 5-HT serotonin transporter or 5-HT 1B/1D receptor antagonists. We conclude from these studies that a parallel PI3K- and reactive oxygen species-dependent Akt/mTOR/S6K1 pathway participates independently from MAPK and Rho/ROCK in the mitogenic effect of 5-HT on pulmonary artery SMCs. From these and other studies, we postulate that independent signaling pathways leading to 5-HT-induced SMC proliferation are initiated through multiple 5-HT receptors and serotonin transporter at the cell surface. FAU - Liu, Yinglin AU - Liu Y AD - Pulmonary, Critical Care, and Sleep Division, Tufts-New England Medical Center, 750 Washington Street, Boston, MA 02111, USA. FAU - Fanburg, Barry L AU - Fanburg BL LA - eng GR - HL32723/HL/NHLBI NIH HHS/United States PT - Journal Article PT - Research Support, N.I.H., Extramural DEP - 20050929 PL - United States TA - Am J Respir Cell Mol Biol JT - American journal of respiratory cell and molecular biology JID - 8917225 RN - 0 (Antioxidants) RN - 0 (Enzyme Inhibitors) RN - 0 (Enzymes) RN - 0 (Intracellular Signaling Peptides and Proteins) RN - 0 (Reactive Oxygen Species) RN - 0 (Receptor, Serotonin, 5-HT2A) RN - 0 (Serotonin 5-HT2 Receptor Antagonists) RN - 333DO1RDJY (Serotonin) RN - EC 2.7.- (Protein Kinases) RN - EC 2.7.11.1 (Oncogene Protein v-akt) RN - EC 2.7.11.1 (Protein Serine-Threonine Kinases) RN - EC 2.7.11.1 (Proto-Oncogene Proteins c-akt) RN - EC 2.7.11.1 (Ribosomal Protein S6 Kinases, 90-kDa) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) RN - EC 2.7.11.1 (rho-Associated Kinases) SB - IM MH - Animals MH - Antioxidants/pharmacology MH - Cattle MH - Cell Proliferation/drug effects MH - Cells, Cultured MH - Enzyme Activation MH - Enzyme Inhibitors/pharmacology MH - Enzymes/drug effects/*metabolism MH - Intracellular Signaling Peptides and Proteins MH - Muscle, Smooth, Vascular/*drug effects/growth & development/metabolism MH - Oncogene Protein v-akt/drug effects/metabolism MH - Phosphatidylinositol 3-Kinases/drug effects/metabolism MH - Phosphorylation/drug effects MH - Protein Kinases/metabolism MH - Protein Serine-Threonine Kinases/drug effects/metabolism MH - Proto-Oncogene Proteins c-akt/drug effects/metabolism MH - Pulmonary Artery/cytology/*drug effects/metabolism MH - Reactive Oxygen Species/metabolism MH - Receptor, Serotonin, 5-HT2A/drug effects/metabolism MH - Ribosomal Protein S6 Kinases, 90-kDa/drug effects/metabolism MH - Serotonin/*pharmacology MH - Serotonin 5-HT2 Receptor Antagonists MH - TOR Serine-Threonine Kinases MH - rho-Associated Kinases PMC - PMC2644181 EDAT- 2005/10/01 09:00 MHDA- 2006/02/24 09:00 PMCR- 2007/02/01 CRDT- 2005/10/01 09:00 PHST- 2005/10/01 09:00 [pubmed] PHST- 2006/02/24 09:00 [medline] PHST- 2005/10/01 09:00 [entrez] PHST- 2007/02/01 00:00 [pmc-release] AID - 2005-0163OC [pii] AID - ajrcmb342182 [pii] AID - 10.1165/rcmb.2005-0163OC [doi] PST - ppublish SO - Am J Respir Cell Mol Biol. 2006 Feb;34(2):182-91. doi: 10.1165/rcmb.2005-0163OC. Epub 2005 Sep 29.