Abstract 19687: High-Density Lipoprotein Leads to Stimulation of Endothelial Protein Kinase C-β2 and Inhibition of eNOS-Activating Pathways in Patients with Coronary Disease: Role of Paraoxonase-1 Inactivation
Background: High-density lipoprotein (HDL) has been shown to exert important atheroprotective effects and HDL-targeted therapies are currently evaluated as a potential novel therapy in coronary disease (CAD). However, recent evidence suggests that vascular effects of HDL can be heterogeneous. The aim of the present study was to characterize mechanisms leading to impaired endothelial-protective effects of HDL in patients with CAD.
Methods: HDL was isolated from patients with CAD (HDLCAD, n=50) and healthy subjects (HDLHS; n=25) by sequential ultracentrifugation. The effect of HDL on endothelial NO production was examined by electron spin resonance spectroscopy, and endothelial protein kinase C (PKC) beta2, Akt and eNOS phosphorylation were determined. Endothelial inflammatory activation was examined by NF-κB activity, VCAM-1 expression and monocyte adhesion. The effects of HDL on endothelial repair were characterized in a carotid injury model in nude mice. Paraoxonase-1 (PON1) activity/content in HDL and endothelial binding of radioactive labeled HDL were characterized, as well as the effects of HDL from PON1-/- mice.
Results: Whereas HDLHS stimulated eNOS-activating pathways, endothelial NO production and repair, no such effects were observed with HDLCAD. The capacity of HDLHS to stimulate endothelial NO production was critical for its anti-inflammatory effects. Endothelial binding of HDLCAD was reduced as compared to HDLHS. Notably, HDLCAD in contrast to HDLHS activated endothelial PKCbeta2 (+68.3% vs. PBS, P<0.01), which in turn inhibited eNOS-activating pathways. PON1 activity was decreased whereas PON1 content was increased in HDLCAD, suggesting inactivation of HDL-bound PON1. Of note, impaired HDL-associated PON1 activity was identified as a mechanism underlying PKCbeta2 activation by HDL. HDL from PON1-/- mice failed to stimulate endothelial NO production or to inhibit endothelial inflammatory activation.
Conclusion: In summary, the present study indicates that in patients with CAD HDL gains endothelial PKCbeta2-activating properties that are resulting from a reduced HDL-associated PON1 activity leading to inhibition of eNOS-activating pathways and a subsequent loss of important vasoprotective effects of HDL in CAD.
- © 2010 by American Heart Association, Inc.