A comparison of folic acid and 5-methyltetrahydrofolate for prevention of DNA damage and cell death in human lymphocytes in vitro.
A comparison of folic acid and 5-methyltetrahydrofolate for prevention of DNA damage and cell death in human lymphocytes in vitro.
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DOI：
10.1093/mutage/18.1.81
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发表时间：
2003
期刊：
影响因子：
2.7
通讯作者：
Xu Wang;M. Fenech
中科院分区：
文献类型：
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作者：
Xu Wang;M. Fenech
叶酸（FA）是叶酸的最氧化和最稳定的形式，通常用作膳食补充剂和培养基。FA必须被还原和甲基化，以成为血液中发现的代谢活性形式并被组织利用，即5-甲基四氢叶酸（5-MeTHF）。5-MeTHF是维生素B（12）依赖性甲硫氨酸合酶催化高半胱氨酸转化为甲硫氨酸所需的甲基供体。据推测，5-MeTHF在减少自发DNA损伤和改善细胞增殖方面可能比FA更有效，因为与FA不同，5-MeTHF可以为甲硫氨酸合成提供甲基，甲硫氨酸合成是通过多胺产生细胞分裂和DNA转化为S-腺苷甲硫氨酸后维持甲基化所必需的。我们的目的是确定是否FA和5-MeTHF在他们的能力不同，以防止遗传损伤和细胞增殖的人淋巴细胞在体外。将来自8名女性志愿者（40-48岁）的淋巴细胞在含有12-120 nM FA或5-MeTHF的RPMI 1640培养基中培养9天。用植物血凝素刺激有丝分裂，并在第3天和第6天更换培养基。在第8天通过加入细胞松弛素B抑制胞质分裂，在第9天收获细胞并转移到显微镜载玻片上。采用微核试验综合模式检测染色体损伤、细胞死亡和细胞停滞。结果表明，与120 nM 5-MeTHF相比，120 nM FA的双核细胞微核频率显著降低（P < 0.05），然而，与120 nM相比，12 nM浓度的两种形式的叶酸均与微核和核芽频率增加相关（P < 0.05）。细胞凋亡倾向于显着高于5-MeTHF文化与FA文化相比，然而，坏死和核分裂的文化之间是相似的。我们的结论是，5-甲基THF是不是更有效地比FA在防止人类淋巴细胞基因组不稳定性，在这个体外系统。需要进一步的研究来澄清胆碱和蛋氨酸浓度的作用以及还原叶酸载体和叶酸受体在确定5-MeTHF和FA的相对生物利用度方面对基因组稳定性的重要性。
Folic acid (FA), the most oxidized and stable form of folate, is commonly used as a dietary supplement and in culture media. FA must be reduced and methylated to become the metabolically active form found in blood and utilized by tissues, i.e. 5-methyltetrahydrofolate (5-MeTHF). 5-MeTHF is the methyl group donor required for the conversion of homocysteine to methionine catalyzed by vitamin B(12)-dependent methionine synthase. It is hypothesized that 5-MeTHF may be more effective than FA in reducing spontaneous DNA damage and improving cell proliferation because, unlike FA, it can donate a methyl group for methionine synthesis, which is required for cell division via polyamine production and for maintenance methylation of DNA after its conversion to S-adenosylmethionine. We aimed to determine whether FA and 5-MeTHF differed in their capacity to prevent genetic damage and cell proliferation of human lymphocytes in vitro. Lymphocytes from eight female volunteers (40-48 years) were cultured in RPMI 1640 medium containing 12-120 nM FA or 5-MeTHF for 9 days. Mitogenesis was stimulated with phytohemagglutinin and the medium changed on days 3 and 6. Cytokinesis was inhibited by adding cytochalasin B on day 8 and cells were harvested and transferred to microscope slides on day 9. Chromosome damage, cell death and cytostasis was measured using the cytokinesis-block micronucleus assay in its comprehensive mode. The results showed that the frequency of micronucleated binucleate cells was significantly lower at 120 nM FA compared with 120 nM 5-MeTHF (P < 0.05), however, at 12 nM concentration both forms of folate were associated with increased frequency of micronuclei and nuclear buds relative to 120 nM (P < 0.05). Apoptosis tended to be significantly higher in 5-MeTHF cultures compared with FA cultures, however, necrosis and nuclear division were similar between cultures. We conclude that 5-MeTHF is not more efficient than FA in preventing human lymphocyte genomic instability in this in vitro system. Further research is needed to clarify the role of choline and methionine concentration and the importance of the reduced folate carrier and the folate receptor in determining the relative bioavailability of 5-MeTHF and FA with regard to genome stability.