Stimulation of Collagen Gene Expression by Ascorbic Acid in Cultured Human Fibroblasts: A role for lipid peroxidation?

Abstract

Ascorbic acid stimulates collagen gene expression in cultural fibroblasts (Lyons, B. L., and Schwartz, R. L. (1984) Nucleic Acids Res. 12, 2569-2579), but the mechanisms responsible for this effect are poorly understood. In the presence of the transitional metal iron, ascorbic acid could induce lipid peroxidation with the formation of reactive aldehydes. Since another aldehyde, acetaldehyde, the first metabolite of ethanol, also stimulates collagen transcription in cultured fibroblasts (Brenner, D. A., and Chojkier, M. (1987) J. Biol. Chem 262, 17690-17696), we investigated whether ascorbic acid induces lipid peroxidation in cultured cells and if this is the mechanism by which ascorbic acid stimulates collagen gene expression. Ascorbic acid (0.2 mM) induced lipid peroxidation in cultured human fibroblasts judging by the production of thiobarbituric acid-reactive substances and carbonyl groups, and by the presence of malondialdehyde- and 4-hydroxynonenal-protein adducts. Ascorbic acid stimulated (2-3-fold) the net production of collagen relative to total proteins, the levels of procollagen alpha 1 (I) mRNA and the transcription of this gene. Inhibition of the ascorbic acid-induced lipid peroxidation in cultured human fibroblasts with alpha-tocopherol (50 microM) or methylene blue (10 microM) prevented the stimulation of collagen gene expression. The addition of malondialdehyde (200 microM), a product of lipid peroxidation, to cultured human fibroblasts also increased 2-3-fold collagen production and procollagen alpha 1 (I) mRNA levels. Thus, ascorbic acid induces lipid peroxidation and reactive aldehydes and this step may be necessary for the stimulation of collagen gene expression by ascorbic acid in cultured human fibroblasts.