The aim of my thesis was to investigate the role of cyclic nucleotide phosphodiesterases (cAMP-PDEs) in the regulation of cAMP-dependent signaling in vascular smooth muscle cells (VSMCs), and to assess their functional involvement in vascular reactivity and their potential alteration in a pathophysiological model of heart failure (HF). My work was based on two models of vascular smooth muscle:(1) Isolated VSMCs in culture having acquired a synthetic phenotype, in which an approach of real-time imaging (FRET: Fluorescence Resonance Energy Transfer) was applied in situ to visualize the spatiotemporal dynamics of cAMP-dependent signals. Our results indicate that, in these cells, increased levels of cAMP induced by β-adrenergic stimulation (β-AR) involve different β-ARs subtypes according to the intracellular compartment considered (β1-and β2-ARs in the cytosol and only β2-ARs in the submembrane compartment). We also observed that the mRNA expression of cAMP-PDEs isoforms and the functional contribution of these enzymes in the regulation of intracellular cAMP signals were dependent on the VSMCs seeding density in culture.(2) Arterial blood vessels from two different vascular beds (aorta and mesenteric artery) isolated from healthy and HF rats, to study their contractile function and thus the regulation by the cAMP pathway. We showed that cAMP-PDE families contribute differently to the control of vascular tone in the thoracic aorta (PDE3 = PDE4, no PDE2) and mesenteric artery (PDE4 > PDE2, no PDE3), endothelium exerting a crucial role in the regulation of their functional activities, especially through the production of nitric oxide (NO). We also demonstrated alterations in vascular reactivity during HF, including its control through the cAMP-PDEs. In the aorta, endothelial dysfunction associated with the alteration of the NO pathway leads to an increase in PDE3 activity which masks PDE4 activity and β-AR relaxation. In mesenteric artery from HF rats, endothelial function is preserved and PDE2, 3 and 4 are functional.This study underlines the importance of PDEs in regulating vascular cAMP signaling, and shows that the activity and function of different cAMP-PDE families are tightly modulated by many parameters (VSMCs phenotype and seeding density) and/or physiopathological situations (vascular bed, endothelium and HF).
