PDGF induces SphK1 expression via Egr-1 to promote pulmonary artery smooth muscle cell proliferation.
Pulmonary arterial hypertension (PAH) is a progressive, life-threatening disease for which there is currently no curative treatment available. Pathologic changes in this disease involve remodeling of the pulmonary vasculature, including marked proliferation of pulmonary artery smooth muscle cells (PASMCs). Recently, the bioactive lipid sphingosine-1-phosphate (S1P) and its activating kinase, sphingosine kinase 1 (SphK1), have been shown to be upregulated in PAH and promote PASMC proliferation. The mechanisms regulating the transcriptional upregulation of SphK1 in PASMCs are unknown. In this study, we investigated the role of platelet-derived growth factor (PDGF), a PAH-relevant stimuli associated with enhanced PASMC proliferation, on SphK1 expression regulation. In human PASMCs (hPASMCs), PDGF significantly increased SphK1 mRNA and protein expression and induced cell proliferation. Selective inhibition of SphK1 attenuated PDGF-induced hPASMC proliferation. In silico promoter analysis for SphK1 identified several binding sites for early growth response protein 1 (Egr-1), a PDGF-associated transcription factor. Luciferase assays demonstrated that PDGF activates the SphK1 promoter in hPASMCs, and truncation of the 5'-promoter reduced PDGF-induced SphK1 expression. Stimulation of hPASMCs with PDGF induced Egr-1 protein expression, and direct binding of Egr-1 to the SphK1 promoter was confirmed by chromatin immunoprecipitation analysis. Inhibition of ERK signaling prevented induction of Egr-1 by PDGF. Silencing of Egr-1 attenuated PDGF-induced SphK1 expression and hPASMC proliferation. These studies demonstrate that SphK1 is regulated by PDGF in hPASMCs via the transcription factor Egr-1, promoting cell proliferation. This novel mechanism of SphK1 regulation may be a therapeutic target in pulmonary vascular remodeling in PAH.
Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; Department of Pharmacology, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; and Medical Scientist Training Program, University of Illinois at Chicago, Chicago, Illinois.
Justin R
JR
Sysol
Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; Department of Pharmacology, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; and.
Viswanathan
V
Natarajan
Department of Medicine, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; Department of Pharmacology, Division of Pulmonary, Critical Care, Sleep and Allergy, University of Illinois at Chicago, Chicago, Illinois; and machador@uic.edu.
Roberto F
RF
Machado
D000077214:Becaplermin; D001665:Binding Sites; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism*; D004790:Enzyme Induction; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D020574:Proto-Oncogene Proteins c-sis / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D066253:Vascular Remodeling / Q000187:drug effects; D000099157:Sphingosine Kinase
D000077214:Becaplermin; D051766:Early Growth Response Protein 1; D048049:Extracellular Signal-Regulated MAP Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D020574:Proto-Oncogene Proteins c-sis; D000099157:Sphingosine Kinase; C497325:EGR1 protein, human
Egr1; PASMC; PDGF; SphK1; gene expression; proliferation