title: Reciprocal regulation of Rac1 and PAK-1 by HIF-1alpha: a positive-feedback loop promoting pulmonary vascular remodeling.
abstract: Pulmonary vascular remodeling associated with pulmonary hypertension is characterized by media thickening, disordered proliferation, and in situ thrombosis. The p21-activated kinase-1 (PAK-1) can control growth, migration, and prothrombotic activity, and the hypoxia-inducible transcription factor HIF-1alpha was associated with pulmonary vascular remodeling. Here we studied whether PAK-1 and HIF-1alpha are linked in pulmonary vascular remodeling. PAK-1 was expressed in the media of remodeled pulmonary vessels from patients with pulmonary vasculopathy and was upregulated, together with its upstream regulator Rac1 and HIF-1alpha in lung tissue from lambs with pulmonary vascular remodeling. PAK-1 and Rac1 were activated by thrombin involving calcium, thus resulting in enhanced generation of reactive oxygen species (ROS) in human pulmonary artery smooth muscle cells (PASMCs). Activation of PAK-1 stimulated HIF activity and HIF-1alpha expression involving ROS and NF-kappaB, enhanced the expression of the HIF-1 target gene plasminogen activator inhibitor-1, and stimulated PASMC proliferation. Importantly, HIF-1 itself bound to the Rac1 promoter and enhanced Rac1 and PAK-1 transcription. Thus, PAK-1 and its activator Rac1 are novel HIF-1 targets that may constitute a positive-feedback loop for induction of HIF-1alpha by thrombin and ROS, thus explaining elevated levels of PAK-1, Rac1, and HIF-1alpha in remodeled pulmonary vessels.
authors.affiliation: Department of Pediatric Cardiology, Technical University Munich, Munich, Germany.
authors.forename: Isabel
authors.initials: I
authors.lastname: Diebold
authors.forename: Andreas
authors.initials: A
authors.lastname: Petry
authors.forename: Talija
authors.initials: T
authors.lastname: Djordjevic
authors.forename: Rachida S
authors.initials: RS
authors.lastname: Belaiba
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Fineman
authors.forename: Stephen
authors.initials: S
authors.lastname: Black
authors.forename: Christian
authors.initials: C
authors.lastname: Schreiber
authors.forename: Sohrab
authors.initials: S
authors.lastname: Fratz
authors.forename: John
authors.initials: J
authors.lastname: Hess
authors.forename: Thomas
authors.initials: T
authors.lastname: Kietzmann
authors.forename: Agnes
authors.initials: A
authors.lastname: Görlach
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D056945:Hep G2 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D011247:Pregnancy; D011651:Pulmonary Artery / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012756:Sheep; D013917:Thrombin / Q000494:pharmacology; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D054462:p21-Activated Kinases; D013917:Thrombin; D020830:rac1 GTP-Binding Protein; D002118:Calcium