Increased inducible nitric oxide synthase protein but limited nitric oxide formation occurs in astrocytes of the hph-1 (tetrahydrobiopterin deficient) mouse.
It has been suggested that decreased tetrahydrobiopterin (BH4) availability may be a useful tool for limiting excessive nitric oxide (NO) formation. In order to test this hypothesis we utilised cultured astrocytes derived from the brain of the hph-1 (BH4 deficient) mouse. In response to treatment with lipopolysaccharide and interferon-gamma (LPS/gammaIFN) levels of BH4 doubled in both wild type and hph-1 astrocytes. However, levels of BH4 in hph-1 astrocytes remained only 25% of the wild type astrocytes. Nitric oxide formation, measured with an NO-electrode, was 45% less from LPS/gammaIFN stimulated hph-1 astrocytes compared with wild type stimulated astrocytes. In contrast, iNOS specific activity and iNOS protein were enhanced in hph-1 stimulated astrocytes by 40 and 60%, respectively when compared with wild type. In conclusion it appears that whilst a decrease in BH4 may limit NO release per se, the possibility and consequences of long term 'over' induction of iNOS protein requires further consideration.
Barker
J E
JE
Department of Neurochemistry, Institute of Neurology, Queen Square, London WC1N 3BG, UK. barkerje@svhm.org.au
Strangward
H M
HM
Brand
M P
MP
Hurst
R D
RD
Land
J M
JM
Clark
J B
JB
Heales
S J
SJ
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000172:deficiency / Q000378:metabolism; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009994:Osmolar Concentration
D008070:Lipopolysaccharides; D001708:Biopterins; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C003402:sapropterin