Tetrahydrobiopterin supplementation reduces atherosclerosis and vascular inflammation in apolipoprotein E-knockout mice

摘要

BH 4 (tetrahydrobiopterin) supplementation improves endothelial function in models of vascular disease by maintaining eNOS (endothelial nitric oxide synthase) coupling and NO (nitric oxide) bioavailability. However, the cellular mechanisms through which enhanced endothelial function leads to reduced atherosclerosis remain unclear.We have used a pharmaceutical BH 4 formulation to investigate the effects of BH 4 supplementation on atherosclerosis progression in ApoE-KO (apolipoprotein E-knockout) mice. Single oral dose pharmacokinetic studies revealed rapid BH 4 uptake into plasma and organs. Plasma BH 4 levels returned to baseline by 8 h after oral dosing, but remained markedly increased in aorta at 24 h. Daily oral BH 4 supplementation in ApoE-KO mice from 8 weeks of age, for a period of 8 or 12 weeks, had no effect on plasma lipids or haemodynamic parameters, but significantly reduced aortic root atherosclerosis compared with placebo-treated animals. BH 4 supplementation significantly reduced VCAM-1 (vascular cell adhesion molecule 1) mRNA levels in aortic endothelial cells, markedly reduced the infiltration of T-cells, macrophages and monocytes into plaques, and reduced T-cell infiltration in the adjacent adventitia, but importantly had no effect on circulating leucocytes. GCH (GTP cyclohydrolase I)-transgenic mice, with a specific increase in endothelial BH 4 levels, exhibited a similar reduction in vascular immune cell infiltration compared with BH 4-deficient controls, suggesting that BH 4 reduces vascular inflammation via endothelial cell signalling. In conclusion, BH 4 supplementation reduces vascular immune cell infiltration in atherosclerosis and may therefore be a rational therapeutic approach to reduce the progression of atherosclerosis.