School of Life Sciences, Yunnan Normal University, Yunnan, China.
Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Kunming, Yunnan 650500, China.
Mutagenesis. 2023 Jun 20;38(3):160-168. doi: 10.1093/mutage/gead007.
Telomere length (TL), which is maintained by human telomerase reverse transcriptase (hTERT; component of telomerase) and/or TRF1/TRF2 (core components of shelterin) via different mechanisms, is essential for chromosomal stability and cell survival. Folates comprise a group of essential B9 vitamin that involve in DNA synthesis and methylation. This study aimed to evaluate the effects of folic acid (FA) and 5-methyltetrahydrofolate (5-MeTHF) on TL, chromosome stability, and cell survival of telomerase-negative BJ and telomerase-positive A375 cells in vitro. BJ and A375 cells were cultured in modified medium with FA or 5-MeTHF (22.6 or 2260 nM) for 28 days. TL and mRNA expression were determined by RT-qPCR. Chromosome instability (CIN) and cell death were measured by CBMN-Cyt assay. Results showed that abnormal TL elongation was observed in FA and 5-MeTHF deficient BJ cells. The TL of A375 cells showed no obvious alterations under the FA-deficient condition but was significantly elongated under the 5-MeTHF-deficient condition. In both BJ and A375 cells, FA and 5-MeTHF deficiency caused decreased TRF1, TRF2, and hTERT expression, increased CIN and cell death; while a high concentration of 5-MeTHF induced elongated TL, elevated CIN, increased TRF1 and TRF2 expression and decreased hTERT expression, when compared with the FA counterpart. These findings concluded that folate deficiency induced TL instability in both telomerase-negative and -positive cells, and FA was more efficient in maintaining TL and chromosome stability compared with 5-MeTHF.
端粒长度（TL）通过不同的机制由人类端粒酶逆转录酶（hTERT；端粒酶的组成部分）和/或 TRF1/TRF2（庇护所核心成分）维持，对于染色体稳定性和细胞存活至关重要。叶酸是一组必需的 B9 维生素，参与 DNA 合成和甲基化。本研究旨在评估叶酸（FA）和 5-甲基四氢叶酸（5-MeTHF）对体外端粒酶阴性 BJ 和端粒酶阳性 A375 细胞 TL、染色体稳定性和细胞存活的影响。BJ 和 A375 细胞在含 FA 或 5-MeTHF（22.6 或 2260 nM）的改良培养基中培养 28 天。通过 RT-qPCR 测定 TL 和 mRNA 表达。通过 CBMN-Cyt 测定法测量染色体不稳定性（CIN）和细胞死亡。结果表明，FA 和 5-MeTHF 缺乏的 BJ 细胞观察到异常的 TL 延长。FA 缺乏条件下 A375 细胞的 TL 没有明显改变，但 5-MeTHF 缺乏条件下显著延长。在 BJ 和 A375 细胞中，FA 和 5-MeTHF 缺乏导致 TRF1、TRF2 和 hTERT 表达减少，CIN 和细胞死亡增加；而高浓度的 5-MeTHF 诱导 TL 延长，CIN 增加，TRF1 和 TRF2 表达增加，hTERT 表达减少，与 FA 相比。这些发现表明，叶酸缺乏在端粒酶阴性和阳性细胞中均诱导 TL 不稳定，FA 比 5-MeTHF 更有效地维持 TL 和染色体稳定性。
