Division of Biochemical Toxicity, FDA/National Center for Toxicological Research, Jefferson, AR, USA.
Nanotechology Core, FDA/National Center for Toxicological Research, Jefferson, AR, USA.
Nanotoxicology. 2020 May;14(4):534-553. doi: 10.1080/17435390.2020.1723730. Epub 2020 Feb 7.
Nanoscale titanium dioxide (TiO) is manufactured in wide scale, with a range of applications in consumer products. Significant toxicity of TiO nanoparticles has, however, been recognized, suggesting considerable risk to human health. To evaluate fully their toxicity, assessment of the epigenetic action of these nanoparticles is critical. However, only few studies are available examining capability of nanoparticles to alter epigenetic integrity. In the present study, the effect of TiO nanoparticles exposure on DNA methylation, a major epigenetic mechanism, was investigated in cellular model systems. A panel of cells relevant to portals of human exposure (Caco-2 (colorectal), HepG2 (liver), NL20 (lung), and A-431 (skin)) was exposed to TiO nanoparticles to assess effects on global methylation, gene-specific methylation, and expression levels of DNA methyltransferases, MBD2, and UHRF1. Global methylation was determined by enzyme-linked immunosorbent assay-based immunochemical analysis. Degree of promoter methylation across a defined panel of genes was evaluated using EpiTect Methyl II Signature PCR System Array technology. Expression of , , , , and was quantified by qRT-PCR. Decrease in global DNA methylation in cell lines Caco-2, HepG2, and A-431 exposed to TiO nanoparticles was shown. Across four cell lines, eight genes (, , , , , , , and ) were identified in which promotors were methylated after exposure. Altered expression of these genes is associated with disease etiology. The results also revealed aberrant expression of epigenetic regulatory genes involved in DNA methylation (DNMT1, DNMT3a, DNMT3b, MBD2, and UHRF1) in TiO exposed cells, which was cell type dependent. Findings from this study clearly demonstrate the impact of TiO nanoparticles exposure on DNA methylation in multiple cell types, supporting potential involvement of this epigenetic mechanism in the toxicity of TiO nanoparticles. Hence for complete assessment of potential risk from nanoparticle exposure, epigenetic studies are critical.
纳米二氧化钛（TiO）被广泛制造，广泛应用于消费品。然而，纳米 TiO 颗粒的毒性已得到广泛认可，这表明它们对人类健康存在相当大的风险。为了充分评估其毒性，评估这些纳米颗粒的表观遗传作用至关重要。然而，目前只有少数研究探讨了纳米颗粒改变表观遗传完整性的能力。在本研究中，研究了 TiO 纳米颗粒暴露对细胞模型系统中主要表观遗传机制 DNA 甲基化的影响。一组与人类暴露门户相关的细胞（Caco-2（结肠）、HepG2（肝）、NL20（肺）和 A-431（皮肤））被暴露于 TiO 纳米颗粒，以评估其对全局甲基化、基因特异性甲基化以及 DNA 甲基转移酶、MBD2 和 UHRF1 的表达水平的影响。通过基于酶联免疫吸附试验的免疫化学分析确定全局甲基化。使用 EpiTect Methyl II Signature PCR 系统阵列技术评估定义基因面板上的启动子甲基化程度。通过 qRT-PCR 定量表达 、 、 、 、 和 。暴露于 TiO 纳米颗粒的 Caco-2、HepG2 和 A-431 细胞系中观察到全局 DNA 甲基化减少。在四种细胞系中，有 8 个基因（ 、 、 、 、 、 、和 ）的启动子在暴露后被甲基化。这些基因的表达改变与疾病病因学有关。研究结果还揭示了参与 DNA 甲基化的表观遗传调节基因（DNMT1、DNMT3a、DNMT3b、MBD2 和 UHRF1）在 TiO 暴露细胞中的异常表达，这与细胞类型有关。本研究的结果清楚地表明 TiO 纳米颗粒暴露对多种细胞类型中 DNA 甲基化的影响，支持这种表观遗传机制在 TiO 纳米颗粒毒性中的潜在作用。因此，为了全面评估纳米颗粒暴露的潜在风险，需要进行表观遗传研究。
