Endothelial alpha1-adrenoceptors regulate neo-angiogenesis.
OBJECTIVE
Intact endothelium plays a pivotal role in post-ischaemic angiogenesis. It is a phenomenon finely tuned by activation and inhibition of several endothelial receptors. The presence of alpha(1)-adrenoceptors on the endothelium suggests that these receptors may participate in regenerative phenomena by regulating the responses of endothelial cells involved in neo-angiogenesis.


METHODS
We evaluated the expression of the subtypes of the alpha(1)-adrenoceptor in isolated endothelial cells harvested from Wistar-Kyoto (WKY) rats. We explored the possibility these alpha(1)-adrenoceptors may influence the pro-angiogenic phenotype of endothelial cells in vitro. In vivo, we used a model of hindlimb ischaemia in WKY rats, to assess the effects of alpha(1) adrenoceptor agonist or antagonist on angiogenesis in the ischaemic hindlimb by laser Doppler blood flow measurements, digital angiographies, hindlimb perfusion with dyed beads and histological evaluation.


RESULTS
In vitro, pharmacological antagonism of alpha(1)-adrenoceptors in endothelial cells from WKY rats by doxazosin enhanced, while stimulation of these adrenoceptors with phenylephrine, inhibited endothelial cell proliferation and DNA synthesis, ERK and retinoblastoma protein (Rb) phosphorylation, cell migration and tubule formation. In vivo, we found increased alpha(1)-adrenoceptor density in the ischaemic hindlimb, compared to non-ischaemic hindlimb, suggesting an enhanced alpha(1)-adrenoceptor tone in the ischaemic tissue. Treatment with doxazosin (0.06 mg kg(-1) day(-1) for 14 days) did not alter systemic blood pressure but enhanced neo-angiogenesis in the ischaemic hindlimb, as measured by all our assays.


CONCLUSIONS
Our findings support the hypothesis that the alpha(1)-adrenoceptors in endothelial cells provide a negative regulation of angiogenesis.
Ciccarelli
M
M
Division of Internal Medicine, Department of Clinical Medicine & Cardiovascular Sciences, Federico II University of Naples, Naples, Italy.
Santulli
G
G
Campanile
A
A
Galasso
G
G
Cervèro
P
P
Altobelli
G G
GG
Cimini
V
V
Pastore
L
L
Piscione
F
F
Trimarco
B
B
Iaccarino
G
G
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D017292:Doxazosin / Q000494:pharmacology; D042783:Endothelial Cells / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D006614:Hindlimb / Q000098:blood supply / Q000473:pathology; D066298:In Vitro Techniques; D007511:Ischemia / Q000503:physiopathology*; D018919:Neovascularization, Physiologic; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D017292:Doxazosin