Ascorbic Acid Uptake and Regulation of Type I Collagen Synthesis in Cultured Vascular Smooth Muscle Cells

Abstract

Background/Aims: 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. Methods/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 proα1(I) collagen and conversion of proα1(I) and proα2(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 μ M and below, which were readily achieved by culture of the cells at plasma physiologic ascorbate concentrations. Conclusion: 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.