Trophic effects induced by alpha1D-adrenoceptors on endothelial cells are potentiated by hypoxia.
Catecholamines have been shown to be involved in vascular remodeling through the stimulation of alpha(1)-adrenoceptors (alpha(1)-ARs). Recently, it has been demonstrated that catecholamines can stimulate angiogenesis in pathological conditions, even if the mechanisms and the AR subtypes involved still remain unclear. We investigated the influence of hypoxia (3% O(2)) on the ability of picomolar concentrations of phenylephrine (PHE), which are unable to induce any vascular contraction, to induce a trophic effect in human endothelial cells through stimulation of the alpha(1D)-subtype ARs. PHE, at picomolar concentrations, significantly promoted pseudocapillary formation from fragments of human mature vessels in vitro. Exposure to hypoxia significantly potentiated this effect, which was inhibited by the selective alpha(1D)-AR antagonist BMY-7378 and by the nitric oxide synthase inhibitor L-NAME, suggesting that alpha(1D)-ARs were involved in this effect through activation of the nitric oxide pathway. Proliferation and migration of HUVEC were also affected by picomolar PHE concentrations. Again, these effects were significantly potentiated in cells exposed to hypoxia and were inhibited by BMY-7378 and by N(G)-nitro-L-arginine methyl ester. Conversely, the alpha(1A)-AR-selective antagonist (S)-(+)-niguldipine hydrochloride and the alpha(1B)-AR antagonist chloroethylclonidine dihydrochloride did not modify endothelial cell migration and proliferation in response to PHE. These results demonstrate that the stimulation of alpha(1D)-ARs, triggered by picomolar PHE concentrations devoid of any contractile vascular effects, induces a proangiogenic phenotype in human endothelial cells that is enhanced in a hypoxic environment. The role of alpha(1D)-ARs may become more prominent in the adaptive responses to hypoxic vasculature injury.
Laboratory of Vascular Pharmacology, Department of Preclinical and Clinical Pharmacology, University of Florence, Florence, Italy.
Maria Cristina
MC
Vinci
Lydia
L
Bellik
Sandra
S
Filippi
Fabrizio
F
Ledda
Astrid
A
Parenti
D018674:Adrenergic Antagonists / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D015687:Cell Hypoxia; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009924:Organ Culture Techniques; D010656:Phenylephrine / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects* / Q000378:metabolism; D014469:Umbilical Arteries / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
C547719:ADRA1D protein, human; D018674:Adrenergic Antagonists; D000316:Adrenergic alpha-Agonists; D004791:Enzyme Inhibitors; D010879:Piperazines; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; C053428:BMY 7378; D019331:NG-Nitroarginine Methyl Ester