title: ERK activation contributes to regulation of spontaneous contractile tone via superoxide anion in isolated rat aorta of angiotensin II-induced hypertension.
abstract: Arteries from hypertensive animals and humans have increased spontaneous tone. Increased superoxide anion (superoxide) contributes to elevated blood pressure (BP) and spontaneous tone in hypertension. The association between the extracellular signaling-regulated kinase 1/2 (ERK1/2)-mitogen-activated protein kinase (MAPK) signaling pathway and generation of superoxide and spontaneous tone in isolated aorta was studied in angiotensin II (ANG II)-infused hypertensive (HT) rats. Systolic BP, phosphorylation of ERK, aortic superoxide formation, and aortic spontaneous tone were compared in sham normotensive and HT rats. Infusion of ANG II (0.5 mg x kg(-1) x day(-1) for 6 days) significantly elevated the systolic BP (P<0.01). The phosphorylation of ERK1/2 vs. total ERK1/2 in thoracic aorta was enhanced, and superoxide was increased in the HT vs. the sham group (P<0.01). Spontaneous tone developed in the HT group, but not in the normotensive group. MAPK/ERK1/2 (MEK1/2)-ERK1/2 signaling pathway inhibitors, PD-98059 (10 micromol/l), and U-0126 (10 micromol/l), significantly reduced the phosphorylation of ERK1/2, superoxide generation (P<0.01), and spontaneous tone (P<0.01) in HT. These findings suggest that ANG II infusion induces the production of superoxide and spontaneous tone and that both are dependent on ERK-MAPK activation. In endothelium-denuded aorta, however, MEK1/2 inhibitors did not inhibit the spontaneous tone, even though they significantly reduced superoxide generation similar to endothelium-intact aorta. These data suggest that inhibition of ERK1/2 signaling pathway, via PD-98059 or U-0126, may regulate spontaneous tone in an endothelium-dependent manner. In conclusion, these findings support the importance of the ERK1/2 signaling pathway in modulating vascular oxidative stress and subsequently mediating spontaneous tone in HT.
authors.affiliation: Department of Community Health Sciences, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3Y6, Canada.
authors.forename: Lili
authors.initials: L
authors.lastname: Ding
authors.forename: Alexander
authors.initials: A
authors.lastname: Chapman
authors.forename: Ryan
authors.initials: R
authors.lastname: Boyd
authors.forename: Hui Di
authors.initials: HD
authors.lastname: Wang
mesh_terms: D000804:Angiotensin II; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D001794:Blood Pressure; D002070:Butadienes / Q000494:pharmacology; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism / Q000503:physiopathology; D004789:Enzyme Activation; D005419:Flavonoids / Q000494:pharmacology; D006973:Hypertension / Q000139:chemically induced / Q000201:enzymology / Q000378:metabolism* / Q000503:physiopathology; D020935:MAP Kinase Signaling System; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013481:Superoxides / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D002070:Butadienes; D005419:Flavonoids; D009570:Nitriles; D047428:Protein Kinase Inhibitors; C113580:U 0126; D013481:Superoxides; D000804:Angiotensin II; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one