Extremely Low-Frequency Electromagnetic Fields Cause G1 Phase Arrest through the Activation of the ATM-Chk2-p21 Pathway

In daily life, humans are exposed to the extremely low-frequency electromagnetic fields (ELF-EMFs) generated by electric appliances, and public concern is increasing regarding the biological effects of such exposure. Numerous studies have yielded inconsistent results regarding the biological effects of ELF-EMF exposure. Here we show that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, inhibiting cell proliferation. To present well-founded results, we comprehensively evaluated the biological effects of ELF-EMFs at the transcriptional, protein, and cellular levels. Human HaCaT cells from an immortalized epidermal keratinocyte cell line were exposed to a 1.5 mT, 60 Hz ELF-EMF for 144 h. The ELF-EMF could cause G1 arrest and decrease colony formation. Protein expression experiments revealed that ELF-EMFs induced the activation of the ATM/Chk2 signaling cascades. In addition, the p21 protein, a regulator of cell cycle progression at G1 and G2/M, exhibited a higher level of expression in exposed HaCaT cells compared with the expression of sham-exposed cells. The ELF-EMF-induced G1 arrest was diminished when the CHK2 gene expression (which encodes checkpoint kinase 2; Chk2) was suppressed by specific small interfering RNA (siRNA). These findings indicate that ELF-EMFs activate the ATM-Chk2-p21 pathway in HaCaT cells, resulting in cell cycle arrest at the G1 phase. Based on the precise control of the ELF-EMF exposure and rigorous sham-exposure experiments, all transcriptional, protein, and cellular level experiments consistently supported the conclusion. This is the first study to confirm that a specific pathway is triggered by ELF-EMF exposure.

日常生活中，人类会暴露于电器产生的极低频电磁场（extremely low-frequency electromagnetic fields，ELF-EMFs）中，公众对此类暴露的生物学效应的关注度与日俱增。针对ELF-EMF暴露的生物学效应，现有多项研究得出了不一致的结论。本研究证实，ELF-EMFs可在HaCaT细胞中激活ATM-Chk2-p21通路，从而抑制细胞增殖。为确保研究结果具备坚实的科学依据，本研究从转录水平、蛋白水平及细胞层面全面评估了ELF-EMFs的生物学效应。本研究选用永生化表皮角质形成细胞系HaCaT细胞，将其暴露于1.5 mT、60 Hz的ELF-EMFs环境中144小时。实验结果显示，ELF-EMFs可诱导细胞发生G1期阻滞，并降低细胞集落形成能力。蛋白表达实验结果显示，ELF-EMFs可激活ATM/Chk2信号级联反应。此外，作为G1期与G2/M期细胞周期进程调控因子的p21蛋白，在ELF-EMF暴露组的HaCaT细胞中的表达水平显著高于假照射组。当通过特异性小干扰RNA（small interfering RNA，siRNA）抑制编码检验点激酶2（Chk2）的CHK2基因表达后，ELF-EMF诱导的G1期阻滞现象显著减弱。上述研究结果表明，ELF-EMFs可在HaCaT细胞中激活ATM-Chk2-p21通路，最终导致细胞周期阻滞于G1期。得益于ELF-EMF暴露条件的精准控制与严谨的假照射对照实验，所有转录水平、蛋白水平及细胞层面的实验结果均一致支持上述结论。本研究是首个证实ELF-EMF暴露可触发特定信号通路的相关研究。