Superoxide anion mediates angiotensin II-induced potentiation of contractile response to sympathetic stimulation.
Angiotensin II is known to potentiate vasoconstriction induced by electrical field stimulation (EFS), but the underlying mechanisms for this potentiation are not fully understood. This study was designed to investigate the role of superoxide anion in the potentiation effects of angiotensin II. Contraction of rat mesenteric arterial segments was induced by perivascular nerve stimulation with EFS, and superoxide production was measured with lucigenin-enhanced chemiluminescence. Extracellular signal-regulated kinase (ERK) phosphorylation was determined in cultured smooth muscle cells with Western blot. Angiotensin II concentration dependently potentiated the contraction of rat mesenteric arteries to EFS, which is frequency-dependent. This potentiation was blunted by an angiotensin AT(1) receptor antagonist (2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylic acid, CV-11974), NAD(P)H oxidase inhibitor (apocynin), superoxide dismutase (SOD) and its mimetic tiron, but not affected by angiotensin AT(2) receptor antagonist and inhibitors of xanthine oxidase, cytochrome P450, and cyclooxygenase. Angiotensin II increased superoxide production by mesenteric arteries, which was blunted by angiotensin AT(1) receptor antagonist CV-11974, and NAD(P)H oxidase inhibitor apocynin. Superoxide generating compound pyrogallol mimicked the effects of angiotensin II. Tyrosine kinase inhibitor (tyrphostin A25) and mitogen-activated protein kinase (MAPK)/ERK inhibitors (1,4-diamino-2,3-dicyano-1,4-bis [2-aminophenylthio]butadiene (U 0126)) inhibited angiotensin II- and pyrogallol-induced potentiation of EFS-induced contraction, while inactive forms of these inhibitors did not show any inhibitory effects. In cultured smooth muscle cells from mesenteric arteries, angiotensin II and superoxide similarly induced ERK phosphorylation. These results showed that superoxide mediated angiotensin II-induced potentiation of contractile response to EFS and tyrosine kinase-MAPK/ERK activation was involved.
Lu
Chao
C
Smooth Muscle Research Program and Department of Anaesthesia, McMaster University, Hamilton, ON, Canada.
Su
Li-Ying
LY
Lee
Robert M K W
RM
Gao
Yu-Jing
YJ
D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000294:innervation / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000294:innervation / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D047228:Angiotensin II Type 1 Receptor Blockers; D000975:Antioxidants; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D014662:Vasoconstrictor Agents; D013481:Superoxides; D000804:Angiotensin II; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D019255:NADPH Oxidases; D048049:Extracellular Signal-Regulated MAP Kinases