Exogenous NADPH increases cerebral blood flow through NADPH oxidase-dependent and -independent mechanisms.
OBJECTIVE
NADPH, a substrate for the superoxide-producing enzyme NADPH oxidase, produces vasodilation in the cerebral circulation. However, the mechanisms of the effect have not been fully elucidated. We used a peptide inhibitor of NADPH oxidase (gp91ds-tat) and null mice lacking the gp91phox subunit of NADPH oxidase to examine the mechanisms of the cerebrovascular effects of exogenous NADPH.


RESULTS
Cerebral blood flow (CBF) was assessed by laser-Doppler flowmetry in anesthetized mice equipped with a cranial window. Superfusion with NADPH increased CBF (27% at 100 micromol/L) without affecting the EEG. The CBF increase was attenuated by the free-radical scavenger MnTBAP (-54%, P<0.05) but not by the H2O2 scavenger catalase. The response was also attenuated by gp91ds-tat (-64%, P<0.05) and by the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (-44%, P<0.05). The increase in CBF produced by NADPH was attenuated in gp91-null mice (-41%, P<0.05). NADPH increased production of reactive oxygen species, assessed by hydroethidine microfluorography, an effect blocked by MnTBAP or gp91ds-tat and not observed in gp91-null mice.


CONCLUSIONS
These data suggest that the mechanisms of the CBF increases produced by exogenous NADPH are multifactorial and include NADPH oxidase-dependent and -independent factors.
Division of Neurobiology, Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA.
Laibaik
L
Park
Josef
J
Anrather
Ping
P
Zhou
Kelly
K
Frys
Gang
G
Wang
Costantino
C
Iadecola
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003433:Crosses, Genetic; D004569:Electroencephalography / Q000379:methods; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism / Q000494:pharmacology; D006023:Glycoproteins / Q000494:pharmacology; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009249:NADP / Q000502:physiology*; D019255:NADPH Oxidases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine / Q000494:pharmacology; D009861:Onium Compounds / Q000494:pharmacology; D010617:Phenanthridines / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014664:Vasodilation / Q000502:physiology
D005456:Fluorescent Dyes; D016166:Free Radical Scavengers; D006023:Glycoproteins; D009861:Onium Compounds; D010617:Phenanthridines; D017382:Reactive Oxygen Species; C473031:gp91ds-tat protein, chimeric; D019335:Nitroarginine; C058428:hydroethidine; D009249:NADP; C007517:diphenyleneiodonium; D019001:Nitric Oxide Synthase; D019255:NADPH Oxidases