Mitochondrial monoamine oxidase-A-mediated hydrogen peroxide generation enhances 5-hydroxytryptamine-induced contraction of rat basilar artery.
OBJECTIVE
We evaluated the role(s) of monoamine oxidase (MAO)-mediated H₂O₂ generation on 5-hydroxytryptamine (5-HT)-induced tension development of isolated basilar artery of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats.


METHODS
Basilar artery (endothelium-denuded) was isolated for tension measurement and Western blots. Enzymically dissociated single myocytes from basilar arteries were used for patch-clamp electrophysiological and confocal microscopic studies.


RESULTS
Under resting tension, 5-HT elicited a concentration-dependent tension development with a greater sensitivity (with unchanged maximum tension development) in SHR compared with WKY (EC(50) : 28.4 ± 4.1 nM vs. 98.2 ± 9.4 nM). The exaggerated component of 5-HT-induced tension development in SHR was eradicated by polyethylene glycol-catalase, clorgyline and citalopram whereas exogenously applied H₂O₂ enhanced the 5-HT-elicited tension development in WKY. A greater protein expression of MAO-A was detected in basilar arteries from SHR than in those from WKY. In single myocytes and the entire basilar artery, 5-HT generated (clorgyline-sensitive) a greater amount of H₂O₂ in SHR compared with WKY. Whole-cell iberiotoxin-sensitive Ca(2+) -activated K(+) (BK(Ca) ) amplitude measured in myocytes of SHR was approximately threefold greater than that in WKY (at +60 mV: 7.61 ± 0.89 pA·pF(-1) vs. 2.61 ± 0.66 pA·pF(-1) ). In SHR myocytes, 5-HT caused a greater inhibition (clorgyline-, polyethylene glycol-catalase- and reduced glutathione-sensitive) of BK(Ca) amplitude than in those from WKY.


CONCLUSIONS
5-HT caused an increased generation of mitochondrial H₂O₂ via MAO-A-mediated 5-HT metabolism, which caused a greater inhibition of BK(Ca) gating in basilar artery myocytes, leading to exaggerated basilar artery tension development in SHR.
School of Biomedical Sciences (Programme in Vascular and Metabolic Biology), Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China.
Christina Chui Wa
CC
Poon
Sai Wang
SW
Seto
Alice Lai Shan
AL
Au
Qian
Q
Zhang
Rachel Wai Sum
RW
Li
Wayne Yuk Wai
WY
Lee
George Pak Heng
GP
Leung
Siu Kai
SK
Kong
John Hok Keung
JH
Yeung
Sai Ming
SM
Ngai
Ho Pui
HP
Ho
Simon Ming Yuen
SM
Lee
Shun Wan
SW
Chan
Yiu Wa
YW
Kwan
D000818:Animals; D001488:Basilar Artery / Q000187:drug effects / Q000378:metabolism; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000378:metabolism*; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D008995:Monoamine Oxidase / Q000378:metabolism*; D032342:Muscle Cells / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects
D010455:Peptides; D024681:Potassium Channels, Calcium-Activated; D012701:Serotonin; C064719:iberiotoxin; D006861:Hydrogen Peroxide; D008995:Monoamine Oxidase