Darr D, Combs S, Pinnell S
Division of Dermatology, Duke University Medical Center, Durham, North Carolina 27710.
Arch Biochem Biophys. 1993 Dec;307(2):331-5. doi: 10.1006/abbi.1993.1596.
Ascorbic acid positively affects the synthesis of collagen, the most abundant extracellular protein. The mechanism by which ascorbate mediates the increased synthesis is debated. One recent hypothesis suggests that ascorbic acid induces an increase in lipid peroxidation and that this increase, in some manner, up-regulates collagen gene expression. Evidence is presented that indicate increases in lipid peroxidation [thiobarbituric acid (TBA)-reactive material] is coincidental to collagen increases in ascorbate-treated cells, not a causal factor. Thus, cell impermeable iron chelators totally abolish ascorbate-mediated lipid peroxidation but do not affect collagen synthesis in the least. Decreases in TBA-reactive products seen at higher ascorbate levels (indicative of the well known pro- to antioxidant conversion of ascorbate in vitro) are paralleled by decreases in collagen synthesis. The decrease seen in collagen is completely reversed by treatment of the cell cultures with superoxide dismutase and catalase while the measure of lipid peroxidation is unaffected by coincubation with these antioxidant enzymes. Additionally, incubation conditions used to measure ascorbate induction of TBA-reactive material (buffers vs media, adherent vs detached cells) were found to be very important and results support the thesis that lipid peroxidation and collagen synthesis can be dissociated. While these results do not rule out a role for lipid mediators in regulating collagen synthesis at some level, they suggest this mechanism need not be involved for collagen increases seen in ascorbic acid-treated cells.
抗坏血酸对胶原蛋白（最丰富的细胞外蛋白质）的合成有积极影响。抗坏血酸盐介导合成增加的机制存在争议。最近的一种假设认为，抗坏血酸会导致脂质过氧化增加，并且这种增加以某种方式上调胶原蛋白基因表达。有证据表明，在抗坏血酸处理的细胞中，脂质过氧化增加[硫代巴比妥酸（TBA）反应性物质]与胶原蛋白增加是同时发生的，并非因果关系。因此，细胞不可渗透的铁螯合剂完全消除了抗坏血酸介导的脂质过氧化，但对胶原蛋白合成毫无影响。在较高抗坏血酸水平下观察到的TBA反应性产物减少（这表明抗坏血酸在体外由促氧化剂向抗氧化剂的转化是众所周知的）与胶原蛋白合成减少平行。用超氧化物歧化酶和过氧化氢酶处理细胞培养物可完全逆转胶原蛋白的减少，而脂质过氧化的测量不受与这些抗氧化酶共同孵育的影响。此外，发现用于测量抗坏血酸诱导的TBA反应性物质的孵育条件（缓冲液与培养基、贴壁细胞与悬浮细胞）非常重要，结果支持脂质过氧化和胶原蛋白合成可以分离的论点。虽然这些结果不排除脂质介质在某种程度上调节胶原蛋白合成中的作用，但它们表明抗坏血酸处理的细胞中胶原蛋白增加不一定涉及这种机制。
