Dose dependent effects of reactive oxygen and nitrogen species on the function of neuronal nitric oxide synthase

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• 作者：Jian Sun ; Lawrence J. Druhan ; Jay L. Zweier
• 关键词：Neuronal nitric oxide synthase ; Superoxide ; Peroxynitrite ; Hydroxyl radical ; Hydrogen peroxide ; Dose-dependent ; Tetrahydrobiopterin ; Monomerization ; Free radical ; Electron paramagnetic resonance
• 刊名：Archives of Biochemistry and Biophysics
• 出版年：2008
• 出版时间：15 March 2008
• 年：2008
• 卷：471
• 期：2
• 页码：126-133
• 全文大小：449 K

文摘

Reactive nitrogen species (RNS) and oxygen species (ROS) have been reported to modulate the function of nitric oxide synthase (NOS); however, the precise dose-dependent effects of specific RNS and ROS on NOS function are unknown. Questions remain unanswered regarding whether pathophysiological levels of RNS and ROS alter NOS function, and if this alteration is reversible. We measured the effects of peroxynitrite (ONOO⁻), superoxide (l10"">l10&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=713b653a3691227392bfe65b65e99ed6"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32>), hydroxyl radical (^.OH), and H₂O₂ on nNOS activity. The results showed that NO production was inhibited in a dose-dependent manner by all four oxidants, but only l11"">l11&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=55d94c06fb4172dd961b2cbec23bc0b5"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32> and ONOO⁻ were inhibitory at pathophysiological concentrations (lt=""less-than-or-equals, slant"" border=0>50 μM). Subsequent addition of tetrahydrobiopterin (BH₄) fully restored activity after l12"">l12&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=39fd32da31951ca11611d991c8070b5a"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32> exposure, while BH₄ partially rescued the activity decrease induced by the other three oxidants. Furthermore, treatment with either ONOO⁻ or l13"">l13&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=de836850fac6362a9c10d84bf5a68e1a"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32> stimulated nNOS uncoupling with decreased NO and enhanced l14"">l14&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=9242e8367dab467e72395cd9cb3ba0ad"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32> generation. Thus, nNOS is reversibly uncoupled by l15"">l15&_user=10&_cdi=6701&_rdoc=4&_acct=C000050221&_version=1&_userid=10&md5=54fc867617f7db13f6071f00bc00bf46"">lt=""Click to view the MathML source"" align=""absbottom"" border=""0"" height=16 width=32> (lt=""less-than-or-equals, slant"" border=0>50 μM), but irreversibly uncoupled and inactivated by ONOO⁻. Additionally, we observed that the mechanism by which oxidative stress alters nNOS activity involves not only BH₄ oxidation, but also nNOS monomerization as well as possible degradation of the heme.