The effect of hypercholesterolemia on vascular function was studied in humans. To eliminate the potential confounding effects of atherosclerosis, vascular reactivity was measured in the forearm resistance vessels of 11 normal subjects (serum LDL cholesterol = 111 +/- 7 mg/dl) and 13 patients with hypercholesterolemia (serum LDL cholesterol = 211 +/- 19 mg/dl, P less than 0.05). Each subject received intrabrachial artery infusions of methacholine, which releases endothelium-derived relaxant factor, and nitroprusside which directly stimulates guanylate cyclase in vascular smooth muscle. Maximal vasodilatory potential was determined during reactive hyperemia. Vasoconstrictive responsiveness was examined during intra-arterial phenylephrine infusion. Forearm blood flow was determined by venous occlusion plethysmography. Basal forearm blood flow in normal and hypercholesterolemic subjects was comparable. Similarly, reactive hyperemic blood flow did not differ between the two groups. In contrast, the maximal forearm blood flow response to methacholine in hypercholesterolemic subjects was less than that observed in normal subjects. In addition, the forearm blood flow response to nitroprusside was less in hypercholesterolemic subjects. There was no difference in the forearm vasoconstrictive response to phenylephrine in the two groups. Thus, the vasodilator responses to methacholine and nitroprusside were blunted in patients with hypercholesterolemia. We conclude that in humans with hypercholesterolemia, there is a decreased effect of nitrovasodilators, including endothelium-derived relaxing factor, on the vascular smooth muscle of resistance vessels.

Endothelium-dependent vasodilation is impaired in hypercholesterolemia, even before the development of atherosclerosis. The purpose of this study was to determine whether infusion of L-arginine, the precursor of the endothelium-derived relaxing factor, nitric oxide, improves endothelium-dependent vasodilation in hypercholesterolemic humans. Vascular reactivity was measured in the forearm resistance vessels of 11 normal subjects (serum LDL cholesterol = 2.76 +/- 0.10 mmol/liter) and 14 age-matched patients with hypercholesterolemia (serum LDL cholesterol = 4.65 +/- 0.36 mmol/liter, P < 0.05). The vasodilative response to the endothelium-dependent vasodilator, methacholine chloride, was depressed in the hypercholesterolemic group, whereas endothelium-independent vasodilation, induced by nitroprusside, was similar in each group. Intravenous administration of L-arginine augmented the forearm blood flow response to methacholine in the hypercholesterolemic individuals, but not in the normal subjects. L-arginine did not alter the effect of nitroprusside in either group. D-arginine had no effect on forearm vascular reactivity in either group. It is concluded that endothelium-dependent vasodilation is impaired in hypercholesterolemic humans. This abnormality can be improved acutely by administration of L-arginine, possibly by increasing the synthesis of endothelium-derived relaxing factor.

It is postulated that vascular disease involves a disturbance in the homeostatic balance of factors regulating vascular tone and structure. Recent developments in gene transfer techniques have emerged as an exciting therapeutic option to treat vascular disease. Several studies have established the feasibility of direct in vivo gene transfer into the vasculature by using reporter genes such as beta-galactosidase or luciferase. To date no study has documented therapeutic effects with in vivo gene transfer of a cDNA encoding a functional enzyme. This study tests the hypothesis that endothelium-derived nitric oxide is an endogenous inhibitor of vascular lesion formation. After denudation by balloon injury of the endothelium of rat carotid arteries, we restored endothelial cell nitric oxide synthase (ec-NOS) expression in the vessel wall by using the highly efficient Sendai virus/liposome in vivo gene transfer technique. ec-NOS gene transfection not only restored NO production to levels seen in normal untreated vessels but also increased vascular reactivity of the injured vessels. Neointima formation at day 14 after balloon injury was inhibited by 70%. These findings provide direct evidence that NO is an endogenous inhibitor of vascular lesion formation in vivo (by inhibiting smooth muscle cell proliferation and migration) and suggest the possibility of ec-NOS transfection as a potential therapeutic approach to treat neointimal hyperplasia.

Background — Statins inhibit HMG-CoA reductase to reduce the synthesis of cholesterol and isoprenoids that modulate diverse cell functions. We investigated the effect of the statins cerivastatin and atorvastatin on angiogenesis in vitro and in vivo. Methods and Results — Endothelial cell proliferation, migration, and differentiation were enhanced at low concentrations (0.005 to 0.01 μmol/L) but significantly inhibited at high statin concentrations (0.05 to 1 μmol/L). Antiangiogenic effects at high concentrations were associated with decreased endothelial release of vascular endothelial growth factor and increased endothelial apoptosis and were reversed by geranylgeranyl pyrophosphate. In murine models, inflammation-induced angiogenesis was enhanced with low-dose statin therapy (0.5 mg · kg ⁻¹ · d ⁻¹ ) but significantly inhibited with high concentrations of cerivastatin or atorvastatin (2.5 mg · kg ⁻¹ · d ⁻¹ ). Despite the fact that high-dose statin treatment was effective at reducing lipid levels in hyperlipidemic apolipoprotein E–deficient mice, it impaired rather than enhanced angiogenesis. Finally, high-dose cerivastatin decreased tumor growth and tumor vascularization in a murine Lewis lung cancer model. Conclusions — HMG-CoA reductase inhibition has a biphasic dose-dependent effect on angiogenesis that is lipid independent and associated with alterations in endothelial apoptosis and vascular endothelial growth factor signaling. Statins have proangiogenic effects at low therapeutic concentrations but angiostatic effects at high concentrations that are reversed by geranylgeranyl pyrophosphate. At clinically relevant doses, statins may modulate angiogenesis in humans via effects on geranylated proteins.