von Willebrand factor activates endothelial nitric oxide synthase in blood platelets by a glycoprotein Ib‐dependent mechanism

Abstract

To cite this article: Riba R, Oberprieler NG, Roberts W, Naseem KM. von Willebrand factor activates endothelial nitric oxide synthase in blood platelets by a glycoprotein Ib-dependent mechanism. J Thromb Haemost 2006; 4: 2636-44.Summary. Background: The molecular regulation of endothelial nitric oxide synthase (eNOS) in blood platelets and the signalling events induced by platelet-derived NO are poorly defined. In particular, the ability of von Willebrand factor (VWF) to stimulate cyclic guanosine monophosphate (cGMP) formation in platelets has produced conflicting data. Objectives: To determine the mechanisms leading to eNOS activation and clarify the downstream signaling pathways activated by platelet-derived NO in response to VWF. Methods: We used three independent markers of NO signaling, [ 3 H] L-citrulline production, cGMP accrual and immunoblotting of vasodilator-stimulated phosphoprotein (VASP) to examine the NO signaling cascade in response to VWF. Results: VWF increased NO synthesis and bioavailability, as evidenced by increased [ 3 H] L-citrulline production and cGMP accrual, respectively. VWFinduced eNOS activation was GPIb-IX-dependent and independent of integrin a IIb b 3 . cGMP formation in response to VWF required Ca 2+ mobilization, Src family kinases, phosphatidylinositol 3-kinase and phospholipase C, but not protein kinase C. This suggests that a cross-talk between the signaling mechanisms regulates platelet activation and NO synthesis. VWF-induced cGMP accrual was completely blocked by apyrase and indomethacin, demonstrating an essential role for platelet-derived ADP and thromboxane A 2 (TxA 2 ). Elevated cGMP levels led to increased VASP phosphorylation at serine 239 that was both protein kinase G (PKG)-and protein kinase A (PKA)-dependent. Conclusions: We demonstrate that VWF activates eNOS through a specific Ca 2+ -dependent GPIb receptor-signaling cascade that relies on the generation of platelet-derived ADP and TxA 2 . Furthermore, we provide the first evidence to suggest that platelet derived-NO/cGMP activates PKA in addition to PKG.

Von Willebrand Factor And The Right Ventricle: The MESA-Right Ventricle Study

“…One report does suggest that vWF stimulates platelet-mediated production of nitric oxide, which could decrease pulmonary vascular resistance, pulmonary artery pressure, and RV workload 22 ; however, this report conflicts with others that suggest increased vWF is associated with decreased nitric oxide. 23 Alternatively, because our study was cross-sectional, reverse causation could explain the findings.…”

Platelet-Derived Nitric Oxide Signaling and Regulation

“…39,40 Other endogenous factors that may be involved in the regulation of platelet NOS3 activity include von Willebrand factor (vWF) and glucose. 41,42 vWF activates platelet NOS3 and increases intraplatelet cGMP, as well as inducing phosphorylation of vasodilator-stimulated phosphoprotein (VASP, a cGMP substrate). It does so by acting through its receptor GPIb, and in a Ca 2ϩ -sensitive manner which requires the participation of PI3-K and phospholipase C; it also involves the generation of ADP and TxA 2 , because vWF-induced cGMP production is blocked by apyrase and indomethacin.…”

“…It does so by acting through its receptor GPIb, and in a Ca 2ϩ -sensitive manner which requires the participation of PI3-K and phospholipase C; it also involves the generation of ADP and TxA 2 , because vWF-induced cGMP production is blocked by apyrase and indomethacin. 41 High glucose activates NOS3 in resting platelets by an osmotic mechanism that probably involves the ␤ isoform of PKC, activation of which causes an increase in intraplatelet Ca 2ϩ . 42,43 Although the importance of phosphorylation of NOS3 in the regulation of its activity in platelets is well accepted, only 1 phosphorylation site, namely that on Ser 1177 , is currently established as being of importance in this regard.…”

The role of Akt in the signaling pathway of the glycoprotein Ib-IX–induced platelet activation

“…15,19,20 In addition, vWF binding to GPIb-IX has been shown to induce NO synthesis and cGMP elevation. 15,21 Thus, it is important to understand the upstream signaling mechanisms that activate the NOcGMP-p38-ERK pathway and the role of this pathway in early GPIb-IX signaling.…”