Enhancement of neuronal survival by 6R-tetrahydrobiopterin.
Recently, we have reported that 6R-tetrahydrobiopterin activates Ca2+ channels in neuronal cells independently of its cofactor activities. Several reports indicate that depolarization-induced activation of Ca2+ channels enhances neuronal survival. Here, we investigated the effects of 6R-tetrahydrobiopterin on survival of differentiated PC12 cells. Depletion of serum and nerve growth factor caused cell death, which was prevented by high potassium. 6R-Tetrahydrobiopterin also prevented death of PC12 cells cultured without serum and nerve growth factor in a dose-related manner at physiological concentrations (1-100 microM). However, surviving cells cultured with 6R-tetrahydrobiopterin showed undifferentiated form. 6S-Tetrahydrobiopterin, a diastereoisomer of 6R-tetrahydrobiopterin, also had a cell-surviving effect, but it was less potent as compared with that of 6R-tetrahydrobiopterin. The cell-surviving effect of 6R-tetrahydrobiopterin was eliminated by a Ca2+ channel blocker, but persisted in the presence of an inhibitor for tyrosine hydroxylase, dopamine, L-DOPA, an inhibitor for nitric oxide synthase and a nitric oxide generator. The effect of 6R-tetrahydrobiopterin was mimicked by a cyclic-AMP analogue and inhibited by an inhibitor for protein kinase A. Ca2+ channel activity was preserved but dopamine-releasing activity was disturbed in surviving cells cultured with 6R-tetrahydrobiopterin. 6R-Tetrahydrobiopterin had no effect on mitogen-activated protein kinase. These findings suggest that, independently of its cofactor activities and mitogen-activated protein kinase cascade, 6R-tetrahydrobiopterin enhances survival of PC12 cells by activating Ca2+ channels via the cyclic-AMP-protein kinase A pathway, but that 6R-tetrahydrobiopterin does not preserve neuronal character induced by nerve growth factor.
Koshimura
K
K
Department of Medicine, Shimane Medical University, Izumo, Japan.
Tanaka
J
J
Murakami
Y
Y
Kato
Y
Y
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D002132:Calcium Radioisotopes; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry / Q000166:cytology* / Q000201:enzymology; D009529:Nicardipine / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D016716:PC12 Cells; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D013873:Thionucleotides / Q000494:pharmacology
D000975:Antioxidants; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002132:Calcium Radioisotopes; D004791:Enzyme Inhibitors; D013873:Thionucleotides; D001708:Biopterins; C016957:adenosine-3',5'-cyclic phosphorothioate; D011189:Potassium Chloride; D009529:Nicardipine; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C003402:sapropterin; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester