Age impairs Flk-1 signaling and NO-mediated vasodilation in coronary arterioles.
Impairment of flow-induced vasodilation in coronary resistance arterioles may contribute to the decline in coronary vasodilatory reserve that occurs with advancing age. This study investigated the effects of age on flow-induced signaling and activation of nitric oxide (NO)-mediated vasodilation in coronary resistance arterioles. Coronary arterioles were isolated from young (approximately 6 mo) and old (approximately 24 mo) male Fischer-344 rats to assess vasodilation to flow, vascular endothelial growth factor (VEGF), and ACh. Flow- and VEGF-induced vasodilation of coronary arterioles was impaired with age (P<or=0.05); however, ACh-induced vasodilation was preserved with age. NG-nitro-L-arginine methyl ester (L-NAME) (1x10(-5) M) eliminated vasodilation to flow, VEGF, and ACh, indicating dependence of these responses on NO. SU-1498, an inhibitor of vascular endothelial growth factor receptor 2 (VEGFR, also known as Flk-1), abolished age-related differences in flow-induced vasodilation. Flow-stimulated phosphorylation of Flk-1 in coronary arterioles from young but not old rats and Flk-1 protein was reduced in coronary arterioles from old rats compared with those from young rats. Flow stimulated phosphorylation of endothelial nitric oxide synthase (eNOS) in coronary arterioles from both young and old rats. VEGF induced phosphorylation of both protein kinase B (Akt) and eNOS in coronary arterioles. VEGF-induced phosphorylation of Akt, but not eNOS, was significantly reduced in arterioles from old rats compared with arterioles from young rats. Wortmannin, an inhibitor of phosphatidylinositol (PI) 3-kinase, eliminated age-related differences in both flow- and VEGF-induced vasodilation. These results indicate that impairment of Flk-1/PI3-kinase signaling contributes to the reduction of flow-induced vasodilation in coronary arterioles with advancing age.
Center for Interdisciplinary Research in Cardiovascular Sciences, Department of Physiology and Pharmacology, P.O. Box 9105, 1 Medical Center Dr., West Virginia University School of Medicine, Morgantown, WV 26506, USA.
Amanda J
AJ
LeBlanc
Robert D
RD
Shipley
Lori S
LS
Kang
Judy M
JM
Muller-Delp
D000109:Acetylcholine / Q000494:pharmacology; D000367:Age Factors; D000375:Aging / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000201:enzymology; D001783:Blood Flow Velocity; D002934:Cinnamates / Q000494:pharmacology; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006834:Hydrazines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000037:antagonists & inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013314:Stress, Mechanical; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology; D000077191:Wortmannin
D000109:Acetylcholine; D000730:Androstadienes; D002934:Cinnamates; D004791:Enzyme Inhibitors; D006834:Hydrazines; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide; D020030:Nitric Oxide Donors; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D014665:Vasodilator Agents; D000077191:Wortmannin; C483044:SU 1498; C084012:1,1-diethyl-2-hydroxy-2-nitrosohydrazine; C496316:Nos3 protein, rat