Antioxidants relieve phosphatase inhibition and reduce PDGF signaling in cultured VSMCs and in restenosis.
OBJECTIVE
Growth factor- and reactive oxygen species (ROS)-induced activation of VSMCs is involved in vascular disease. This study investigates whether inhibitory oxidation of protein tyrosine phosphatases (PTPs) contributes to signaling in VSMCs in vitro and in vivo, and analyzes whether ROS- and growth factor-dependent vascular smooth muscle cell (VSMC) signaling is blunted by antioxidants that are able to activate oxidized PTPs.


RESULTS
Signaling induced by H2O2 and platelet-derived growth factor (PDGF) was analyzed in VSMCs with or without the antioxidants N-acetyl-cysteine (NAC) and tempol. Effects of antioxidants on PDGF-stimulated chemotaxis and proliferation were determined. In vivo effects of antioxidants were analyzed in the rat carotid balloon-injury model, by analyzing neointima formation, cell proliferation, PDGF beta-receptor status, and PTP expression and activity. NAC treatment prevented H2O2-induced PTP inhibition, and reduced H2O2- and ligand-induced PDGF beta-receptor phosphorylation, PDGF-induced proliferation, and chemotaxis of VSMCs. Antioxidants inhibited neointima formation and reduced PDGF receptor phosphorylation in the neointima and also increased PTP activity.


CONCLUSIONS
PTP-inhibition was identified as an intrinsic component of H2O2- and PDGF-induced signaling in cultured VSMCs. The reduction in PDGF beta-receptor phosphorylation in vivo, and the increase in PTP activity, by antioxidants indicate activation of oxidized PTPs as a previously unrecognized mechanism for the antirestenotic effects of antioxidants. The findings thus suggest, in general terms, reactivation of oxidized PTPs as a novel antirestenotic strategy.
Kappert
Kai
K
Department of Oncology-Pathology, Karolinska Institutet, 17176 Stockholm, Sweden.
Sparwel
Jan
J
Sandin
Asa
A
Seiler
Alexander
A
Siebolts
Udo
U
Leppänen
Olli
O
Rosenkranz
Stephan
S
Ostman
Arne
A
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D023903:Coronary Restenosis / Q000235:genetics / Q000378:metabolism*; D003497:Cyclic N-Oxides / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D013113:Spin Labels
D000975:Antioxidants; D003497:Cyclic N-Oxides; D010982:Platelet-Derived Growth Factor; D017382:Reactive Oxygen Species; D013113:Spin Labels; D006861:Hydrogen Peroxide; D017479:Receptors, Platelet-Derived Growth Factor; D017027:Protein Tyrosine Phosphatases; C001803:tempol; D000111:Acetylcysteine