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S. LiCalzi, D. L. Purich, K. Chang, A. Afzal, A. Agarwal, J. Busik, M. Segal, M. B. Grant; Carbon Monoxide (CO) Mediates Cytoskeletal Rearrangements via Vasp Phosphorylation and Subsequent Redistribution in Vascular Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4383.
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© ARVO (1962-2015); The Authors (2016-present)
Vasodilator-Stimulated Phosphoprotein (VASP) plays a pivotal role in regulation of migration, vasodilatation, and inhibition of platelet aggregation- all critical processes for maintenance of healthy retinal vasculature. VASP contains three phosphorylation sites (Ser-157, Ser-239, and Thr-278) that are regulated by cGMP and cAMP protein kinases. We studied the effect of vasoactive angiogenic agents CO and NO on cell migration, VASP phosphorylation, and VASP cellular localization and redistribution in cells of nondiabetic and diabetic origin.
CD34+ endothelial precursor cells (EPCs) and platelets were isolated from human peripheral blood from nondiabetic and diabetic donors. After 1- and 15-min exposure to the NO donor DETA/NO or the CO donor Ru(II)Cl2(CO)3 dimer, VASP phosphorylation was examined in platelets and endothelial cells by Western analysis and FACS using phosphor-specific anti-pSer-157 or anti-pSer-239 antibodies. Immunohistochemistry was performed to evaluate VASP redistribution in endothelial cells using anti-VASP antibody following CO or NO exposure. EPC migration was evaluated following exposure to CO or NO using the modified Boyden chamber assay.
CO stimulation induced VASP phosphorylation on Ser-157, but not Ser-239, in both normal and diabetic platelets. On the contrary, NO exposure resulted in phosphorylation on Ser-157 only in normal platelets and on both Ser-157 and Ser-239 in diabetic platelets. In response to both CO and NO exposure, endothelial cell VASP was phosphorylated on Ser-239 and was redistributed to filopodia after 1 minute. At the concentrations tested, both agents induced EPC and endothelial cell migration in a dose-dependent manner.
To maintain a healthy retinal vasculature, NO and CO may compensate for one another or work synergistically to promote cytoskeletal rearrangements via site-specific phosphorylation of VASP. Through such modifications, vasoactive agents may promote retinal vascular repair by improving tissue perfusion, by increasing EPC and endothelial cell function, and by preventing platelet aggregation.
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