title: Neuronal nitric oxide synthase is up-regulated by angiotensin II and attenuates NADPH oxidase activity and facilitates relaxation in murine left ventricular myocytes.
abstract: Angiotensin II (Ang II) is critical in myocardial pathogenesis, mostly via stimulating NADPH oxidase. Neuronal nitric oxide synthase (nNOS) has recently been shown to play important roles in modulating myocardial oxidative stress and contractility. Here, we examine whether nNOS is regulated by Ang II and affects NADPH oxidase production of intracellular reactive oxygen species (ROS(i)) and contractile function in left ventricular (LV) myocytes. Our results showed that Ang II induced biphasic effects on ROS(i) and LV myocyte relaxation (TR(50)) without affecting the amplitude of sarcomere shortening and L-type Ca(2+) current density: TR(50) was prolonged at 30 min but was shortened after 3h (or after Ang II treatment in vivo). Correspondingly, ROS(i) was increased, followed by a reduction to control level. Quantitative RT-PCR and immunoblotting experiments showed that Ang II (3h) increased the mRNA and protein expression of nNOS and increased NO production (nitrite assay) in LV myocyte homogenates, suggesting that nNOS activity may be enhanced and involved in mediating the effects of Ang II. Indeed, n(omega)-nitro-l-arginine methyl ester (l-NAME) or a selective nNOS inhibitor, S-methyl-l-thiocitrulline (SMTC) increased NADPH oxidase production of superoxide/ROS(i) and abolished faster myocyte relaxation induced by Ang II. The positive lusitropic effect of Ang II was not mediated by PKA-, CaMKII-dependent signaling or peroxynitrite. Conversely, inhibition of cGMP/PKG pathway abolished the Ang II-induced faster relaxation by reducing phospholamban (PLN) Ser(16) phosphorylation. Taken together, these results clearly demonstrate that myocardial nNOS is up-regulated by Ang II and functions as an early adaptive mechanism to attenuate NADPH oxidase activity and facilitate myocardial relaxation.
authors.affiliation: Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Chun Zi
authors.initials: CZ
authors.lastname: Jin
authors.forename: Ji Hyun
authors.initials: JH
authors.lastname: Jang
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Jae Gon
authors.initials: JG
authors.lastname: Kim
authors.forename: Young Min
authors.initials: YM
authors.lastname: Bae
authors.forename: Jun
authors.initials: J
authors.lastname: Shi
authors.forename: Cheng Ri
authors.initials: CR
authors.lastname: Che
authors.forename: Sung Joon
authors.initials: SJ
authors.lastname: Kim
authors.forename: Yin Hua
authors.initials: YH
authors.lastname: Zhang
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D003971:Diastole / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects* / Q000201:enzymology*; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology*; D019255:NADPH Oxidases / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000804:Angiotensin II; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; D019255:NADPH Oxidases