Protection against vascular aging in Nox2-deficient mice: Impact on endothelial progenitor cells and reparative neovascularization.
BACKGROUND
Aging is associated with increased oxidative stress levels and impaired neovascularization following ischemia. Because Nox2-containing NADPH oxidase is a major source of ROS in the vasculature, we investigated its potential role for the modulation of ischemia-induced neovascularization in the context of aging.


RESULTS
Hindlimb ischemia was surgically induced by femoral artery removal in young (2 months) and old (10 months) Nox2-deficient (Nox2(-/-)) and wild type mice. We found that Nox2 expression is increased by aging in ischemic muscles of wild type mice. This is associated with a significant reduction of blood flow recovery after ischemia in old compared to young mice at day 21 after surgery (Doppler flow ratios: 0.51 ± 0.05 vs. 0.72 ± 0.05; p < 0.05). We also demonstrate that capillary and arteriolar densities are significantly reduced in ischemic muscles of old animals, while oxidative stress levels are increased (nitrotyrosine immunostaining). Importantly, Nox2 deficiency reduces oxidative stress levels in ischemic tissues and restores blood flow recuperation and vascular densities in old animals. Endothelial progenitor cells (EPCs) have an important role for postnatal neovascularization. Here we show that the functional activities of EPCs (migration, adhesion to mature endothelial cells) are significantly impaired in old compared to young mice. However, Nox2 deficiency rescues EPC functional activities in old animals. We also demonstrate an age-dependent pathological increase of oxidative stress levels in EPCs (DHE, DCF-DA) that is not present in Nox2-deficient animals.


CONCLUSIONS
Nox2-containing NADPH oxidase deficiency protects against age-dependent impairment of neovascularization. Potential mechanisms include reduced ROS generation in ischemic tissues and preserved angiogenic activities of EPCs.
Department of Cardiovascular Research, Centre Hospitalier de l'Université de Montréal, Québec, Canada.
Julie
J
Turgeon
Paola
P
Haddad
Sylvie
S
Dussault
Jessika
J
Groleau
Fritz
F
Maingrette
Gemma
G
Perez
Alain
A
Rivard
D000367:Age Factors; D000375:Aging / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001783:Blood Flow Velocity; D002448:Cell Adhesion; D002465:Cell Movement; D002478:Cells, Cultured; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000201:enzymology* / Q000473:pathology; D006614:Hindlimb; D007511:Ischemia / Q000201:enzymology* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry; D008562:Membrane Glycoproteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000098:blood supply*; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency* / Q000235:genetics; D018919:Neovascularization, Physiologic; D018384:Oxidative Stress; D020127:Recovery of Function; D012039:Regional Blood Flow; D013234:Stem Cells / Q000201:enzymology* / Q000473:pathology; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D014652:Vascular Diseases / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*
D008562:Membrane Glycoproteins; D013481:Superoxides; C002744:3-nitrotyrosine; D014443:Tyrosine; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases