This Article Full Text Full Text (PDF) All Versions of this Article: 2005-0163OCv1 34/2/182    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liu, Y. Articles by Fanburg, B. L. Search for Related Content PubMed PubMed Citation Articles by Liu, Y. Articles by Fanburg, B. L.

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

Tufts–New England Medical Center, Pulmonary, Critical Care and Sleep Division, Tupper Research Institute, Boston, Massachusetts

Correspondence and requests for reprints should be addressed to Barry L. Fanburg, M.D., Pulmonary, Critical Care, and Sleep Division, Tufts–New England Medical Center, 750 Washington Street, #257, Boston, MA 02111. E-mail: bfanburg{at}tufts-nemc.org

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.

Key Words: mammalian target of rapamycin • p70 ribosomal S6 kinase • phosphatidylinositol 3-kinase • pulmonary hypertension • serine/threonine protein kinase • serotonin • smooth muscle cells

This article has been cited by other articles:

				A. Ogawa, A. L. Firth, W. Yao, M. M. Madani, K. M. Kerr, W. R. Auger, S. W. Jamieson, P. A. Thistlethwaite, and J. X.-J. Yuan Inhibition of mTOR attenuates store-operated Ca2+ entry in cells from endarterectomized tissues of patients with chronic thromboembolic pulmonary hypertension Am J Physiol Lung Cell Mol Physiol, October 1, 2009; 297(4): L666 - L676. [Abstract] [Full Text] [PDF]

				R. A. Pena-Silva, J. D. Miller, Y. Chu, and D. D. Heistad Serotonin produces monoamine oxidase-dependent oxidative stress in human heart valves Am J Physiol Heart Circ Physiol, October 1, 2009; 297(4): H1354 - H1360. [Abstract] [Full Text] [PDF]

				Y. Liu, W. Ren, R. Warburton, D. Toksoz, and B. L. Fanburg Serotonin induces Rho/ROCK-dependent activation of Smads 1/5/8 in pulmonary artery smooth muscle cells FASEB J, July 1, 2009; 23(7): 2299 - 2306. [Abstract] [Full Text] [PDF]

				C. Guilluy, S. Eddahibi, C. Agard, C. Guignabert, M. Izikki, L. Tu, L. Savale, M. Humbert, E. Fadel, S. Adnot, et al. RhoA and Rho Kinase Activation in Human Pulmonary Hypertension: Role of 5-HT Signaling Am. J. Respir. Crit. Care Med., June 15, 2009; 179(12): 1151 - 1158. [Abstract] [Full Text] [PDF]

				S. Ismail, A. Sturrock, P. Wu, B. Cahill, K. Norman, T. Huecksteadt, K. Sanders, T. Kennedy, and J. Hoidal NOX4 mediates hypoxia-induced proliferation of human pulmonary artery smooth muscle cells: the role of autocrine production of transforming growth factor-{beta}1 and insulin-like growth factor binding protein-3 Am J Physiol Lung Cell Mol Physiol, March 1, 2009; 296(3): L489 - L499. [Abstract] [Full Text] [PDF]

				Y. Liu and B. L. Fanburg Phospholipase D signaling in serotonin-induced mitogenesis of pulmonary artery smooth muscle cells Am J Physiol Lung Cell Mol Physiol, September 1, 2008; 295(3): L471 - L478. [Abstract] [Full Text] [PDF]

				X. Yang, C. Yang, A. Farberman, T. C. Rideout, C. F. M. de Lange, J. France, and M. Z. Fan The mammalian target of rapamycin-signaling pathway in regulating metabolism and growth J Anim Sci, April 1, 2008; 86(14_suppl): E36 - E50. [Abstract] [Full Text] [PDF]

				C. M. Carlin, A. J. Peacock, and D. J. Welsh Fluvastatin Inhibits Hypoxic Proliferation and p38 MAPK Activity in Pulmonary Artery Fibroblasts Am. J. Respir. Cell Mol. Biol., October 1, 2007; 37(4): 447 - 456. [Abstract] [Full Text] [PDF]

				Y. Liu, M. Li, R. R. Warburton, N. S. Hill, and B. L. Fanburg The 5-HT transporter transactivates the PDGF{beta} receptor in pulmonary artery smooth muscle cells FASEB J, September 1, 2007; 21(11): 2725 - 2734. [Abstract] [Full Text] [PDF]

				C. Guilluy, M. Rolli-Derkinderen, P.-L. Tharaux, G. Melino, P. Pacaud, and G. Loirand Transglutaminase-dependent RhoA Activation and Depletion by Serotonin in Vascular Smooth Muscle Cells J. Biol. Chem., February 2, 2007; 282(5): 2918 - 2928. [Abstract] [Full Text] [PDF]

				K. R. Stenmark, K. A. Fagan, and M. G. Frid Hypoxia-Induced Pulmonary Vascular Remodeling: Cellular and Molecular Mechanisms Circ. Res., September 29, 2006; 99(7): 675 - 691. [Abstract] [Full Text] [PDF]

				C. Guignabert, M. Izikki, L. I. Tu, Z. Li, P. Zadigue, A.-M. Barlier-Mur, N. Hanoun, D. Rodman, M. Hamon, S. Adnot, et al. Transgenic Mice Overexpressing the 5-Hydroxytryptamine Transporter Gene in Smooth Muscle Develop Pulmonary Hypertension Circ. Res., May 26, 2006; 98(10): 1323 - 1330. [Abstract] [Full Text] [PDF]

				J. Callebert, J. M. Esteve, P. Herve, K. Peoc'h, C. Tournois, L. Drouet, J. M. Launay, and L. Maroteaux Evidence for a Control of Plasma Serotonin Levels by 5-Hydroxytryptamine2B Receptors in Mice J. Pharmacol. Exp. Ther., May 1, 2006; 317(2): 724 - 731. [Abstract] [Full Text] [PDF]