Study on the Protective Effects of 6R-Tetrahydrobiopterin on the Oxidative Neuronal Injury in Mouse Cortical Cultures

ABSTRACT

OBJECTIVE: 6R-Tetrahydrobiopterin(BH4) is a cofactor for the aromatic amino acid hydroxylases which is essential for the biosynthesis of catecholamines and serotonin. It also acts as a cofactor for nitric oxide synthase, and stimulates the release of some neurotransmitters such as dopamine, serotonin, acetylcholine and glutamate. Recently, it has been reported that BH4 could induce cellular proliferation and enhance neuronal survival. This study was performed to investigate the antioxidative effect of BH4 on the various oxidative insults in mouse cerebral cortical cell cultures. METHODS: Iron ion(FeCl2), zinc ion(ZnCl2), sodium nitroprusside(SNP) and buthionine sulfoximine(BSO, a glutathione depletor) were used as oxidants. Cell death was assessed by measurement of lactate dehydrogenase efflux to bathing media at the end of exposure. RESULT: All 4 oxidants induced neuronal cell death associated with cell body swelling, which was markedly inhibited by trolox(100nM), a vitamin E analog. BH4(10-100nM) markedly inhibited the neuronal cell death induced by all 4 oxidants(20nM Cu2+, 20nM Zn2+, 1nM SNP or 1mM BSO). However, BH4 failed to inhibit the neuronal cell death induced by 24hr exposure to 20nM NMDA. CONCLUSION: These results suggest that BH4 has antioxidative action independently of any actions of enzyme cofactor.