The integrin alpha2beta1 agonist, aggretin, promotes proliferation and migration of VSMC through NF-kB translocation and PDGF production.
OBJECTIVE
During the development of atherosclerotic plaques, vascular smooth muscle cells (VSMCs) migrate from the media to the intima through the basement membrane and interstitial collagenous matrix, and proliferate to form neointima. Here, we investigate the mechanism of VSMC migration and proliferation caused by aggretin, a snake venom integrin alpha2beta1 agonist.


METHODS
Cultures of rat and human VSMCs were treated with aggretin and the signal transduction pathways induced by this agonist were examined by Western blotting, immunoprecipitation and electrophoretic mobility shift assay techniques.


RESULTS
Aggretin-induced VSMC proliferation was blocked by a monoclonal antibody (mAb) against integrin alpha2 (AII2E10) or against the platelet-derived growth factor receptor (PDGFR)-beta. Proliferation was also blocked by inhibition of the tyrosine kinase Src with PP2, phospholipase C (PLC) with U73122, extracellular signal-regulated kinase (ERK) with PD98059 or nuclear factor-kappa B (NF-kB) activation with pyrrolidine dithiocarbamate (PDTC). VSMC migration towards immobilized aggretin was increased in a modified Boyden chamber and this effect was blocked by alpha2beta1-Src-PLC-MAPK axis inhibitors, but not by PDTC, PDGFR-beta mAb, or a phosphoinositide-3 kinase inhibitor, LY294002. Aggretin stimulated the phosphorylation of PDGFR-beta, Src and ERK in a time-dependent manner. NF-kB translocation and platelet-derived growth factor (PDGF)-BB production were also observed. The ERK activation, NF-kB translocation and PDGF-BB production were blocked by PP2, U73122 and PD98059.


CONCLUSIONS
Aggretin induces VSMC proliferation and migration mainly through binding to integrin alpha2beta1, and subsequently activates Src, PLC and ERK pathways, inducing NF-kB activation and PDGF production.
Chung
Ching-Hu
CH
Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
Lin
Kuan-Ting
KT
Chang
Chien-Hsin
CH
Peng
Hui-Chin
HC
Huang
Tur-Fu
TF
D000818:Animals; D000077214:Becaplermin; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D038982:Integrin alpha2beta1 / Q000819:agonists* / Q000502:physiology; D037181:Lectins, C-Type; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis*; D021381:Protein Transport; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000819:agonists; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000502:physiology; D014757:Viper Venoms / Q000494:pharmacology*; D019061:src-Family Kinases / Q000378:metabolism
D038982:Integrin alpha2beta1; D037181:Lectins, C-Type; D016328:NF-kappa B; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D014757:Viper Venoms; C112292:rhodocytin protein, Calloselasma rhodostoma; D000077214:Becaplermin; D020797:Receptor, Platelet-Derived Growth Factor beta; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D010738:Type C Phospholipases