Prostacyclin signaling boosts NADPH oxidase 4 in the endothelium promoting cytoprotection and angiogenesis.
OBJECTIVE
Prostacyclin (PGI2) that is released from the vascular endothelium plays an important role in vasodilatation and thrombo-resistance, and it has long been suspected to protect cell survival. How it does so has never been clear. Recently, it has been shown that the NADPH oxidase 4 (Nox4) improves endothelial cell functions and promotes angiogenesis in vivo, but it was not known how to boost Nox4 therapeutically to exploit its protective functions in the vasculature. Here, we identified such a stimulus.


RESULTS
The selective and stable prostacyclin receptor (IP-R) agonist cicaprost increases the expression of Nox4 in human endothelial cells of several types, including endothelial progenitor cells. The elevation of cellular cyclic-AMP increased Nox4 expression and H2O2 production and prevented endothelial cell apoptosis. We delineate the intracellular signaling that promotes cytoprotection: Cicaprost acts via the IP-R/protein kinase A (PKA)/cyclic adenosine monophosphate (cAMP) response element binding (CREB) protein pathway. Importantly, the up-regulation of Nox4 by cicaprost also enhanced endothelial cell proliferation, migration, and angiogenesis, with all effects being substantially decreased by Nox4 gene silencing. Finally, cicaprost enhanced the growth of blood vessels into subcutaneous sponges implanted in mice, an effect that was also blocked by Nox4 gene silencing.


METHODS
The prostacyclin analogue cicaprost induces Nox4 via IP receptor-cAMP/PKA/CREB pathway. The activation of this pathway protects endothelial cells and enhances pro-angiogenic activity both in vitro and in vivo.


CONCLUSIONS
Prostacyclin promotes the up-regulation of Nox4 in endothelial cells, which opens up a novel strategy that protects and enhances endothelial cell functions in cardiovascular disease, such as repair after myocardial infarction or other ischemic conditions.
1 Centre for Eye Research Australia, University of Melbourne , East Melbourne, Australia .
Hitesh M
HM
Peshavariya
Guei-Sheung
GS
Liu
Catherine W T
CW
Chang
Fan
F
Jiang
Elsa C
EC
Chan
Gregory J
GJ
Dusting
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D019610:Cytoprotection / Q000235:genetics; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D011464:Epoprostenol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000096:biosynthesis*; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000378:metabolism; D051379:Mice; D009203:Myocardial Infarction / Q000235:genetics* / Q000473:pathology / Q000628:therapy; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000096:biosynthesis* / Q000235:genetics; D018919:Neovascularization, Physiologic / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
D006861:Hydrogen Peroxide; D011464:Epoprostenol; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; C043867:cicaprost