TY - JOUR
T1 - Effect of vitamin C on the availability of tetrahydrobiopterin in human endothelial cells
AU - Baker, Timothy A.
AU - Milstien, Sheldon
AU - Katusic, Zvonimir S.
PY - 2001
Y1 - 2001
N2 - Vitamin C has long been known for its beneficial vascular effects, but its mechanism of action remains unclear. Recent reports suggest that vitamin C may prevent endothelial dysfunction by scavenging free radicals and increasing the bioavailability of nitric oxide. To investigate this area further, we studied the effect of vitamin C (10-4 M) and Mn(III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP; 10-5 M), a scavenger of superoxide, hydrogen peroxide, and peroxynitrite, on endothelial nitric oxide synthase (eNOS) enzymatic activity in cultured human umbilical vein endothelial cells. L-Citrulline formation (a measure of eNOS enzymatic activity) was significantly increased in cells treated for 24 h with vitamin C. No effect was observed after MnTBAP treatment. Chronic administration of vitamin C also had no effect on eNOS protein expression. Treatment with vitamin C for 24 h significantly increased levels of the eNOS co-factor tetrahydrobiopterin (BH4), whereas MnTBAP did not affect its levels. Sepiapterin (10-4 M), a precursor of BH4, significantly increased eNOS activity, whereas addition of vitamin C to cells treated with sepiapterin did not cause any further increase in eNOS activity. Our results suggest that the beneficial effect of vitamin C on endothelial function is best explained by increased intracellular BH4 content and subsequent enhancement of eNOS activity. This effect appears to be independent of the ability of vitamin C to scavenge superoxide anions.
AB - Vitamin C has long been known for its beneficial vascular effects, but its mechanism of action remains unclear. Recent reports suggest that vitamin C may prevent endothelial dysfunction by scavenging free radicals and increasing the bioavailability of nitric oxide. To investigate this area further, we studied the effect of vitamin C (10-4 M) and Mn(III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP; 10-5 M), a scavenger of superoxide, hydrogen peroxide, and peroxynitrite, on endothelial nitric oxide synthase (eNOS) enzymatic activity in cultured human umbilical vein endothelial cells. L-Citrulline formation (a measure of eNOS enzymatic activity) was significantly increased in cells treated for 24 h with vitamin C. No effect was observed after MnTBAP treatment. Chronic administration of vitamin C also had no effect on eNOS protein expression. Treatment with vitamin C for 24 h significantly increased levels of the eNOS co-factor tetrahydrobiopterin (BH4), whereas MnTBAP did not affect its levels. Sepiapterin (10-4 M), a precursor of BH4, significantly increased eNOS activity, whereas addition of vitamin C to cells treated with sepiapterin did not cause any further increase in eNOS activity. Our results suggest that the beneficial effect of vitamin C on endothelial function is best explained by increased intracellular BH4 content and subsequent enhancement of eNOS activity. This effect appears to be independent of the ability of vitamin C to scavenge superoxide anions.
KW - MnTBAP
KW - Nitric oxide synthase
KW - Peroxynitrite
KW - Tetrahydrobiopterin
KW - Vitamin C
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U2 - 10.1097/00005344-200103000-00012
DO - 10.1097/00005344-200103000-00012
M3 - Article
C2 - 11243424
AN - SCOPUS:0035120543
VL - 37
SP - 333
EP - 338
JO - Journal of Cardiovascular Pharmacology
JF - Journal of Cardiovascular Pharmacology
SN - 0160-2446
IS - 3
ER -