Vitamin C is an essential antioxidant that enhances survival of oxidatively stressed human vascular endothelial cells in the presence of a vast molar excess of glutathione.
Cellular glutathione levels may exceed vitamin C levels by 10-fold, generating the question about the real antioxidant role that low intracellular concentrations of vitamin C can play in the presence of a vast molar excess of glutathione. We characterized the metabolism of vitamin C and its relationship with glutathione in primary cultures of human endothelial cells oxidatively challenged by treatment with hydrogen peroxide or with activated cells undergoing the respiratory burst, and analyzed the manner in which vitamin C interacts with glutathione to increase the antioxidant capacity of cells. Our data indicate that: (i) endothelial cells express transporters for reduced and oxidized vitamin C and accumulate ascorbic acid with participation of glutathione-dependent dehydroascorbic acid reductases, (ii) although increased intracellular levels of vitamin C or glutathione caused augmented resistance to oxidative stress, 10-times more glutathione than vitamin C was required, (iii) full antioxidant protection required the simultaneous presence of intracellular and extracellular vitamin C at concentrations normally found in vivo, and (iv) intracellular vitamin C cooperated in enhancing glutathione recovery after oxidative challenge thus providing cells with enhanced survival potential, while extracellular vitamin C was recycled through a mechanism involving the simultaneous neutralization of oxidant species. Therefore, in endothelial cells under oxidative challenge, vitamin C functions as an essential cellular antioxidant even in the presence of a vast molar excess of glutathione.
Montecinos
Viviana
V
Departamento de Fisiopatología, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160C, Concepción, Chile.
Guzmán
Paula
P
Barra
Valeria
V
Villagrán
Marcelo
M
Muñoz-Montesino
Carola
C
Sotomayor
Kirsty
K
Escobar
Elizabeth
E
Godoy
Alejandro
A
Mardones
Lorena
L
Sotomayor
Paula
P
Guzmán
Catherine
C
Vásquez
Osmán
O
Gallardo
Victoria
V
van Zundert
Brigitte
B
Bono
María Rosa
MR
Oñate
Sergio A
SA
Bustamante
Marcelo
M
Cárcamo
Juan G
JG
Rivas
Coralia I
CI
Vera
Juan Carlos
JC
D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000378:metabolism*; D005978:Glutathione / Q000494:pharmacology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D010088:Oxidoreductases / Q000378:metabolism; D016897:Respiratory Burst / Q000187:drug effects
D000975:Antioxidants; D016877:Oxidants; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D005978:Glutathione; D001205:Ascorbic Acid