Abstract 18700: Accelerated Endothelial Regeneration and Survival Attenuate Vein Graft Atherosclerosis via Terahydrobiopterin-Dependent eNOS Coupling
As a result of surgical trauma, ischemia and exposure to arterial pressure the majority of endothelium in vein grafts (VG) undergo necrosis or apoptosis. We hypothesized that increased eNOS coupling could protect endothelial viability after VG surgery. To investigate this we utilized a transgenic mouse with endothelial-targeted overexpression of the essential eNOS coupling cofactor BH4. We investigated the effect of BH4 on endothelial cell survival and vascular remodeling in vitro and in vivo using ApoE-KO mice with endothelial-targeted overexpression of the rate limiting enzyme of BH4 synthesis GTP cyclohydrolase 1 (GCH) and LacZ reporter gene. BH4 levels were increased 10-fold in primary endothelium and 5-fold in aorta from GCH/ApoE-KO mice compared with ApoE-KO, without concomitant increases in eNOS protein. Despite no differences at baseline, following 4 days of culture, total endothelial cell number, colony size and number from GCH/ApoE-KO mice were increased (5-fold P=0.05; 2-fold P=0.02; 2-fold P=0.06 respectively, n=6) as were putative EPC levels from bone-marrow mononuclear cells determined by culture (15%,P=0.04) and FACS (26%, P=0.03). Vascular injury as a result of VG surgery in ApoE-KO mice led to significant neointima that was augmented by 61% (P=0.002) in GCH/ApoE-KO mice. Furthermore, endothelial repopulation was accelerated by 21% (P=0.01) and endothelial survival 44% (P=0.03) in these animals. O2- production was significantly attenuated in GCH/ApoE-KO mice measured on both aortic sections using oxidative microtopography and whole aorta by lucigenin chemiluminescence. eNOS inhibition by L-NAME reversed these effects indicating that under basal conditions GCH/ApoE-KO mice had preserved eNOS coupling promoting NO synthesis. In keeping with these findings in 219 patients with coronary artery disease, analysis of saphenous vein and internal mammary artery identified that high vascular BH4 levels were associated with greater vasorelaxations to acetylcholine (P<0.05) and reduced total L-NAME inhibitable O2- suggesting improved eNOS coupling. Availability of BH4 within the endothelium critically modulates the response to vascular injury by maintaining eNOS coupling and accelerating endothelial regeneration.
- © 2012 by American Heart Association, Inc.