Ascorbic acid uptake and regulation of type I collagen synthesis in cultured vascular smooth muscle cells.
OBJECTIVE
Vascular smooth muscle cells contribute both to the structure and function of arteries, but are also involved in pathologic changes that accompany inflammatory diseases such as atherosclerosis. Since inflammation is associated with oxidant stress, we examined the uptake and cellular effects of the antioxidant vitamin ascorbic acid in cultured A10 vascular smooth muscle cells.


RESULTS
A10 cells concentrated ascorbate against a gradient in a sodium-dependent manner, most likely on the sodium-dependent vitamin C transporter type 2 (SVCT2) ascorbate transporter, which was present in immunoblots of cell extracts. Although ascorbate did not affect A10 cell proliferation, it stimulated radiolabeled proline incorporation and type I collagen synthesis. The latter was evident in the cells as increases in proalpha1(I) collagen and conversion of proalpha1(I) and proalpha2(I) collagen to mature forms that were released from the cells and deposited as extracellular matrix. Intracellular type I procollagen maturation was optimal at intracellular ascorbate concentrations of 200 microM and below, which were readily achieved by culture of the cells at plasma physiologic ascorbate concentrations.


CONCLUSIONS
These results show that the SVCT2 facilitates ascorbate uptake by vascular smooth muscle cells, which in turn increases both the synthesis and maturation of type I collagen.
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Huan
H
Qiao
Jason
J
Bell
Saul
S
Juliao
Liying
L
Li
James M
JM
May
D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D002478:Cells, Cultured; D024042:Collagen Type I / Q000096:biosynthesis*; D005978:Glutathione / Q000378:metabolism; D062385:Hydroxybenzoates / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D029363:Organic Anion Transporters, Sodium-Dependent / Q000378:metabolism; D051381:Rats; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters / Q000378:metabolism
D024042:Collagen Type I; D062385:Hydroxybenzoates; D029363:Organic Anion Transporters, Sodium-Dependent; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; C452809:ethyl 2,4-dihydroxybenzoate; D005978:Glutathione; D001205:Ascorbic Acid