The NADPH oxidase inhibitor apocynin induces nitric oxide synthesis via oxidative stress.
We have recently shown that apocynin elicits an oxidative stress in N11 mouse glial cells and other cell types. Here we report that apocynin increased the accumulation of nitrite, the stable derivative of nitric oxide (NO), in the extracellular medium of N11 cell cultures, and the NO synthase (NOS) activity in cell lysates. The increased synthesis of NO was associated with increased expression of inducible NOS (iNOS) mRNA, increased nuclear translocation of the redox-sensitive transcription factor NF-kappa B and decreased intracellular level of its inhibitor IkB alpha. These effects, accompanied by increased production of H2O2, were very similar to those observed after incubation with bacterial lipopolysaccharide (LPS) and were inhibited by catalase. These results suggest that apocynin, similarly to LPS, induces increased NO synthesis by eliciting a generation of reactive oxygen species (ROS), which in turn causes NF-kappa B activation and increased expression of iNOS. Therefore, the increased bioavailability of NO reported in the literature after in vivo or in vitro treatments with apocynin might depend, at least partly, on the drug-elicited induction of iNOS, and not only on the inhibition of NADPH oxidase and the subsequent decreased scavenging of NO by oxidase-derived ROS, as it is often supposed.
Riganti
Chiara
C
Dipartimento di Genetica, Biologia e Biochimica, Università di Torino, Via Santena 5/bis, 10126 Torino, Italy. chiara.riganti@unito.it <chiara.riganti@unito.it>
Costamagna
Costanzo
C
Doublier
Sophie
S
Miraglia
Erica
E
Polimeni
Manuela
M
Bosia
Amalia
A
Ghigo
Dario
D
D000098:Acetophenones / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D009573:Nitrites / Q000378:metabolism; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism
D000098:Acetophenones; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009573:Nitrites; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; C056165:acetovanillone; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019255:NADPH Oxidases