US EPA

3232143 

Journal Article 

Tetrahydrobiopterin deficiency increases neuronal vulnerability to hypoxia 

Delgado-Esteban, M; Almeida, A; Medina, JM 

2002 

Yes 

Journal of Neurochemistry
ISSN: 0022-3042
EISSN: 1471-4159 

82 

5 

1148-1159 

WOS:000177522900015 

Tetrahydrobiopterin (BH4 ) is an essential co-factor for
nitric oxide synthases (NOS). The aim of the present work was to study whether BH4 deficiency
affects the vulnerability of neurones in primary culture to hypoxia. Intracellular BH4 levels
were depleted by pre-incubating neurones with 5 mM 2,4-diamino-6-hydroxypyrimidine (DAHP) for 18
h, after which cells were exposed for 1 h to normoxic or hypoxic conditions. Our results showed
that whereas neurones were resistant to hypoxia-induced cellular damage, BH4 deficiency in
neurones led to oxidative stress, mitochondrial depolarization, ATP depletion and necrosis after
1 h of hypoxia. Indeed, hypoxia specifically inhibited mitochondrial complex IV activity in BH4-
deficient neurones. All these effects were counteracted whenneuronal BH4 levels were restored by
incubating cells with exogenous BH4 during the hypoxic period. Moreover, hypoxia-induced damage
in BH4 -deficient neurones was prevented when N-omega -nitro-l-arginine monomethyl ester (NAME),
haemoglobin or superoxide dismutase plus catalase were present during the hypoxic period,
suggesting that peroxynitrite might be involved in the process. In fact, BH4 deficiency elicited
neuronal NO dysfunction, resulting in an increase in peroxynitrite generation by cells, as shown
by the enhancement in tyrosine nitration; this was prevented by supplements of BH4 , NAME,
haemoglobin or superoxide dismutase plus catalase during hypoxia. Our results suggest that BH4
deficiency converts neuronal NOS into an efficient peroxynitrite synthase, which is responsible
for the increase in neuronal vulnerability tohypoxia-induced mitochondrial damage and necrosis. 

glutathione; neurones; nitric oxide; mitochondria; tetrahydrobiopterin