Angiotensin II (ATII)-inducible platelet-derived growth factor A-chain gene expression is p42/44 extracellular signal-regulated kinase-1/2 and Egr-1-dependent and mediated via the ATII type 1 but not type 2 receptor. Induction by ATII antagonized by nitric oxide.
Angiotensin II (ATII) and platelet-derived growth factor (PDGF) are two vasoconstrictors implicated in the maintenance of normal vascular homeostasis. PDGF A-chain levels increase in cultured vascular smooth muscle cells (SMCs) exposed to ATII. The molecular mechanisms underlying this induction are not known. We used transient transfection analysis to show that ATII can increase reporter gene activity driven by fragments of the PDGF-A promoter bearing recognition elements for the transcription factor, Egr-1. Nuclear run-off experiments indicate that ATII induces Egr-1 expression at the level of transcription. Gel shift and supershift studies show that Egr-1 protein accumulates in the nuclei of SMCs exposed to ATII and binds to the proximal region of the PDGF-A promoter in a specific, time-dependent manner. ATII induced extracellular-signal regulated kinase (p42/44 ERK) activity as did phorbol 12-myristate 13-acetate. The specific MEK1/2 inhibitor, PD98059, suppressed both PDGF-A and Egr-1 endogenous and promoter-dependent expression inducible by ATII. The ATII type 1 receptor (AT1) antagonist, Losartan, inhibited ATII-induction of p42/44 ERK, as well as Egr-1 and PDGF-A, whereas neither PD123319, an AT2 receptor antagonist, nor wortmannin, an inhibitor of phosphatidylinositol 3-kinase and c-Jun N-terminal kinase, had any effect. ATII-induction of Egr-1 and PDGF-A was blocked by SIN-1, a NO donor. In addition, this pathway was blocked by overexpression of NO synthase. Collectively, these findings demonstrate that ATII activation of the PDGF-A promoter is mediated via the MEK/ERK/Egr-1 pathway and AT1 receptor and that this process is antagonized by NO.
Day
F L
FL
Centre for Thrombosis and Vascular Research, The University of New South Wales, Department of Haematology, Prince of Wales Hospital, Sydney, New South Wales 2052, Australia.
Rafty
L A
LA
Chesterman
C N
CN
Khachigian
L M
LM
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology*; D051766:Early Growth Response Protein 1; D005786:Gene Expression Regulation / Q000187:drug effects*; D017874:Immediate-Early Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D009569:Nitric Oxide / Q000502:physiology; D010982:Platelet-Derived Growth Factor / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D011945:Receptors, Angiotensin / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology*
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D017874:Immediate-Early Proteins; D016328:NF-kappa B; D010982:Platelet-Derived Growth Factor; D011945:Receptors, Angiotensin; D014157:Transcription Factors; C075278:platelet-derived growth factor A; D000804:Angiotensin II; D009569:Nitric Oxide; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases