Abstract 14993: Phosphodiesterase 3 Mediates OxLDL-induced P66shc Activation: Implications For Atherogenesis
Background. p66Shc is an adaptor protein mediating oxidative stress and considered a promising therapeutic target against reactive oxygen species (ROS)-related vascular dysfunction. High fat diet, as well as oxidized low density lipoprotein (oxLDL), enhance p66Shc expression and consequently induce endothelial dysfunction and atherosclerotic plaque formation. In line with this, p66Shc-/- mice have decreased aortic lesion, reduced oxidative stress and less foam cells. The present study was designed to study the effect of NO on oxLDL-induced p66Shc expression in human aortic endothelial cells.
Methods and Results. oxLDL transiently induced p66Shc phosphorylation at Ser-36 within 15 minutes. DetaNO (NO donor) reduced p66Shc phosphorylation in a dose-dependent manner. Inhibition of nitric oxide, either by silencing endothelial nitric oxide synthase or L-NAME (inhibitor of nitric oxide synthase), extended p66Shc phosphorylation up to 60 minutes suggesting that the NO has an inhibitory effect on p66Shc phosphorylation. Cyclic guanosine monophosphate (cGMP), but not cyclic adenosine monophosphate (cAMP), inhibited the phosphorylation of p66Shc. This result was confirmed by ODQ treatment (inhibitor of soluble guanylyl cyclase), which also extended phosphorylation of p66Shc suggesting that the effect of NO on p66Shc phosphorylation goes through cGMP pathway. After 24 hours of stimulation with oxLDL, a second wave of p66Shc phosphorylation was observed which could be reduced by DetaNO. Treatments with cGMP or cAMP prevented oxLDL-induced phosphorylation of p66Shc after 24 hours, suggesting that early and late phase p66Shc activation is under the control of different pathways which may involoved phosphodiesterase. Furthermore, cilostazole (inhibitor of PDE3), but not BAY-60-7550 (inhibitor of PDE2) inhibited p66Shc phosphorylation, indicating that PDE3 plays a protective role.
Conclusion. This study demonstrates that NO prevents oxLDL-induced p66Shc activation through phosphodiesterase 3. This observation holds important implications with respect to the regulation of p66Shc, a key mediator of vascular dysfunction in atherosclerosis.
- © 2011 by American Heart Association, Inc.