OBJECTIVE: Epoxyeicosatrienoic acids (EETs) are potent vasodilators produced by endothelial cells. In many vessels, they are an endothelium-derived hyperpolarizing factor (EDHF). However, it is unknown whether they act as an EDHF on platelets and whether this has functional consequences. METHODS AND RESULTS: Flow cytometric measurement of platelet membrane potential using the fluorescent dye DiBac4 showed a resting potential of -58+/-9 mV. Different EET regioisomers hyperpolarized platelets down to -69+/-2 mV, which was prevented by the non-specific potassium channel inhibitor charybdotoxin and by use of a blocker of calcium-activated potassium channels of large conductance (BK(Ca) channels), iberiotoxin. EETs inhibited platelet adhesion to endothelial cells under static and flow conditions. Exposure to EETs inhibited platelet P-selectin expression in response to ADP. Stable overexpression of cytochrome P450 2C9 in EA.hy926 cells (EA.hy2C9 cells) resulted in release of EETs and a factor that hyperpolarized platelets and inhibited their adhesion to endothelial cells. These effects were again inhibited by charybdotoxin and iberiotoxin. CONCLUSIONS: EETs hyperpolarize platelets and inactivate them by inhibiting adhesion molecule expression and platelet adhesion to cultured endothelial cells in a membrane potential-dependent manner. They act as an EDHF on platelets and might be important mediators of the anti-adhesive properties of vascular endothelium.
OBJECTIVE:Epoxyeicosatrienoic acids (EETs) are potent vasodilators produced by endothelial cells. In many vessels, they are an endothelium-derived hyperpolarizing factor (EDHF). However, it is unknown whether they act as an EDHF on platelets and whether this has functional consequences. METHODS AND RESULTS: Flow cytometric measurement of platelet membrane potential using the fluorescent dye DiBac4 showed a resting potential of -58+/-9 mV. Different EET regioisomers hyperpolarized platelets down to -69+/-2 mV, which was prevented by the non-specific potassium channel inhibitor charybdotoxin and by use of a blocker of calcium-activated potassium channels of large conductance (BK(Ca) channels), iberiotoxin. EETs inhibited platelet adhesion to endothelial cells under static and flow conditions. Exposure to EETs inhibited platelet P-selectin expression in response to ADP. Stable overexpression of cytochrome P450 2C9 in EA.hy926 cells (EA.hy2C9 cells) resulted in release of EETs and a factor that hyperpolarized platelets and inhibited their adhesion to endothelial cells. These effects were again inhibited by charybdotoxin and iberiotoxin. CONCLUSIONS:EETs hyperpolarize platelets and inactivate them by inhibiting adhesion molecule expression and platelet adhesion to cultured endothelial cells in a membrane potential-dependent manner. They act as an EDHF on platelets and might be important mediators of the anti-adhesive properties of vascular endothelium.
Authors: Ishfaq A Bukhari; Abdul Jabbar Shah; Kathryn M Gauthier; Katherine A Walsh; Sreenivasulu Reddy Koduru; John D Imig; John R Falck; William B Campbell Journal: Am J Physiol Heart Circ Physiol Date: 2012-02-03 Impact factor: 4.733
Authors: William G Sanders; Christophe Morisseau; Bruce D Hammock; Alfred K Cheung; Christi M Terry Journal: Am J Physiol Cell Physiol Date: 2012-05-23 Impact factor: 4.249
Authors: Ara Askari; Scott J Thomson; Matthew L Edin; Darryl C Zeldin; David Bishop-Bailey Journal: Prostaglandins Other Lipid Mediat Date: 2013-03-06 Impact factor: 3.072