Autocrine expression of osteopontin contributes to PDGF-mediated arterial smooth muscle cell migration.
OBJECTIVE
Migration of smooth muscle cells (SMCs) from the media to the intima of arteries is involved in intimal thickening. The platelet-derived growth factor (PDGF) BB is recognized as a major migratory factor for arterial SMCs both in vitro and during neointima formation. Since PDGF acts in synergy with the matrix protein osteopontin (OPN) and also induces its expression, the present study was conceived to explore the role of the OPN produced in an autocrine fashion by PDGF-stimulated SMCs in the migration process and to define regulatory mechanisms of OPN expression.


RESULTS
PDGF stimulation of quiescent rat aortic SMCs induced their migration (transfilter assays) and the increase of OPN expression (mRNA and protein assays). Blockade of either OPN expression by a specific short interference RNA (siRNA) or of its function by a blocking antibody decreased the PDGF-stimulated migration by about 70%, demonstrating that autocrine production and excretion of OPN are integral to the PDGF-induced SMC migration. In parallel, SMC stimulation by PDGF also activated the transcription factor CREB essentially through mitogen-activated protein kinase (MAPK) 1/2 and protein kinase A (PKA) pathways. Inhibition of either CREB expression (via siRNA) or function (via dominant-negative CREB) decreased both PDGF-induced SMC migration and OPN expression. SMC transfection with OPN promoter reporter constructs demonstrated that PDGF-induced OPN transcription is mediated by CREB binding to two functional sites of the OPN promoter: a CRE site located at -1403 and an AP-1 site located at -76.


CONCLUSIONS
The present study demonstrates that the autocrine expression of OPN plays a major role in PDGF-induced SMC migration. It further shows that the transcription factor CREB, activated in PDGF-stimulated SMCs, plays a key role in PDGF-induced SMC migration, probably by regulating OPN expression.
Jalvy
Sandra
S
INSERM, U441, Pessac, F-33600, France.
Renault
Marie-Ange
MA
Leen
Laetitia Lam Shang
LL
Belloc
Isabelle
I
Bonnet
Jacques
J
Gadeau
Alain-Pierre
AP
Desgranges
Claude
C
D000818:Animals; D050197:Atherosclerosis / Q000378:metabolism / Q000473:pathology; D019898:Autocrine Communication / Q000502:physiology*; D000077214:Becaplermin; D002114:Calcinosis / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology*; D053495:Osteopontin / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013268:Stimulation, Chemical; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection / Q000379:methods; D017539:Tunica Intima / Q000473:pathology*
D017362:Cyclic AMP Response Element-Binding Protein; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053495:Osteopontin; D000077214:Becaplermin; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases