© 2001 by European Society of Cardiology
Copyright © 2001, European Society of Cardiology
Alteration of plasmalemmal caveolae mimics endothelial dysfunction observed in atheromatous rabbit aorta
aINSERM U397, CHU Rangueil, 31403 Toulouse, France
bLaboratoire de Physiologie, Faculté de médecine de Rangueil, 31062 Toulouse, France
cINSERM U466, CHU Rangueil, 31403 Toulouse, France
* Corresponding author. Present address: INSERM U397, CHU Rangueil, 31403 Toulouse Cedex, France. Tel.: +33-5-6132-2147; fax: +33-5-6132-2141 arnal{at}rangueil.inserm.fr
Objectives: In endothelial cells, nitric oxide (NO) is produced by the endothelial isoform of nitric oxide synthase (eNOS), which is localized in the cholesterol-rich plasmalemmal microdomains involved in signal transduction, known as caveolae. The present study was undertaken to evaluate the effect of hypercholesterolemia and fatty streak formation on the endothelial caveolae and on endothelial function, and attempted to determine to what extent the caveolae were involved in endothelium-derived NO production. Methods and Results: We first studied the effect of atheroma on endothelial NO production. Fatty streak infiltrated aorta of cholesterol-fed New Zealand White rabbits demonstrated an impairment of acetylcholine-induced relaxation and nearly normal calcium ionophore A23187 [GenBank] -induced maximal relaxation. The abundance of caveolae in the endothelium covering the fatty streak, as well as their grape-like clustering, appeared to be decreased. We therefore investigated the effect, on endothelial NO production, of the cholesterol-binding agents 2-hydroxypropyl-β-cyclodextrin (hp-β-CD) and filipin, known to alter caveolae structure and/or function. Treatment with either hp-β-CD (2%) or filipin (4 µg/ml) did not affect contraction to phenylephrine or relaxant responses to A23187 [GenBank] or to the NO donor sodium nitroprusside. In contrast, both treatments impaired acetylcholine-induced relaxation. Cultured bovine aortic endothelial cells (BAEC) similarly treated with hp-β-CD demonstrated a 50% decrease of total cellular cholesterol and a decreased abundance of caveolae as well as their grape-like clustering. Cholesterol depletion decreased the bradykinin-induced transient peak of free intracellular calcium and subsequent receptor-stimulated NO production (assessed using reporter cells rich in soluble guanylyl cyclase), whereas that elicited by A23187 [GenBank] remained unaltered. Conclusion: Fatty streak deposit is associated with a decrease in caveolae transductosomes abundance which appears to represent a novel mechanism of endothelial dysfunction.
KEYWORDS Endothelial function; Atherosclerosis; Nitric oxide; Cholesterol
1 These authors contributed equally to this paper.
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