title: Rapamycin reverses pulmonary artery smooth muscle cell proliferation in pulmonary hypertension.
abstract: Pulmonary artery (PA) smooth muscle cell (SMC) proliferation in pulmonary hypertension (PH) may be linked to dysregulated mammalian target of rapamycin (mTOR) signaling. The mTOR pathway involves two independent complexes, mTORC1 and mTORC2, which phosphorylate S6 kinase (S6K) and serine/threonine kinase (Akt), respectively, and differ in their sensitivity to rapamycin. Here, we evaluated rapamycin-sensitive mTOR substrates and PA-SMC proliferation in rats with monocrotaline (MCT)-induced PH (MCT-PH). Compared with cells from control rats, cultured PA-SMCs from MCT-PH rats exhibited increased growth responses to platelet-derived growth factor, serotonin (5-hydroxytryptophan), IL-1β, insulin-like growth factor-1, or fetal calf serum (FCS), with increases in phosphorylated (Ser-473)Akt, (Thr-308)Akt, glycogen synthase kinase (GSK)3, and S6K reflecting activated mTORC1 and mTORC2 signaling. Treatment with rapamycin (0.5 μM) or the Akt inhibitor, A-443654 (0.5 μM), reduced FCS-stimulated growth of PA-SMCs from MCT-PH rats to the level in control rats while inhibiting Akt, GSK3, and S6K activation. Neither the tyrosine kinase inhibitor, imatinib (0.1 μM), nor the 5-hydroxytryptophan transporter inhibitor, fluoxetine (5 μM), normalized the increased PA-SMC growth response to FCS. Rapamycin treatment (5 mg/kg/d) of MCT-PH rats from Day 21 to Day 28 markedly reduced phoshop (p)-Aky, p-GSK3, and p-S6K in PAs, and normalized growth of derived PA-SMCs. This effect was not observed after 1 week of imatinib (100 mg/kg/d) or fluoxetine (20 mg/kg/d). Rapamycin given preventively (Days 1-21) or curatively (Days 21-42) inhibited MCT-PH to a greater extent than did imatinib or fluoxetine. Experimental PH in rats is associated with a sustained proliferative PA-SMC phenotype linked to activation of both mTORC1 and mTORC2 signaling and is suppressed by rapamycin treatment.
authors.affiliation: INSERM U955 Team 8 and Département de Physiologie, Créteil, France.
authors.forename: Amal
authors.initials: A
authors.lastname: Houssaini
authors.forename: Shariq
authors.initials: S
authors.lastname: Abid
authors.forename: Nathalie
authors.initials: N
authors.lastname: Mouraret
authors.forename: Feng
authors.initials: F
authors.lastname: Wan
authors.forename: Dominique
authors.initials: D
authors.lastname: Rideau
authors.forename: Mirna
authors.initials: M
authors.lastname: Saker
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Marcos
authors.forename: Claire-Marie
authors.initials: CM
authors.lastname: Tissot
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Dubois-Randé
authors.forename: Valérie
authors.initials: V
authors.lastname: Amsellem
authors.forename: Serge
authors.initials: S
authors.lastname: Adnot
mesh_terms: D000818:Animals; D017209:Apoptosis; D001549:Benzamides / Q000494:pharmacology; D049109:Cell Proliferation; D002478:Cells, Cultured; D005473:Fluoxetine / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006976:Hypertension, Pulmonary / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D000068877:Imatinib Mesylate; D008297:Male; D016686:Monocrotaline; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D011651:Pulmonary Artery / Q000473:pathology*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology* / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D005473:Fluoxetine; D016686:Monocrotaline; D000068877:Imatinib Mesylate; C546845:mTOR protein, rat; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases; D038362:Glycogen Synthase Kinase 3; D020123:Sirolimus