Aberrant Cytokinesis and Cell Fusion Result in Multinucleation in HepG2 Cells Exposed to Silica Nanoparticles

The multinucleation effect of silica nanoparticles (SiNPs) had been determined in our previous studies, but the relative mechanisms of multinucleation and how the multinucleated cells are generated were still not clear. This extensional study was conducted to investigate the mechanisms underlying the formation of multinucleated cells after SiNPs exposure. We first investigated cellular multinucleation, then performed time-lapse confocal imaging to certify whether the multinucleated cells resulted from cell fusion or abnormal cell division. Our results confirmed for the first time that there are three patterns contributing to the SiNPs-induced multinucleation in HepG2 cells: cell fusion, karyokinesis without cytokinesis, and cytokinesis followed by fusion. The chromosomal passenger complex (CPC) deficiency and cell cycle arrest in G1/S and G2/M checkpoints may be responsible for the cell aberrant cytokinesis. The activated MAPK/ERK1/2 signaling and decreased mitosis related proteins might be the underlying mechanism of cell cycle arrest and thus multinucleation. In summary, we confirmed the hypothesis that aberrant cytokinesis and cell fusion resulted in multinucleation in HepG2 cells after SiNPs exposure. Since cell fusion and multinucleation were involved in genetic instability and tumor development, this study suggests the potential ability of SiNPs to induce cellular genetic instability. These findings raise concerns with regard to human health hazards and environmental risks with SiNPs exposure.本团队前期研究已证实二氧化硅纳米颗粒（silica nanoparticles, SiNPs）可诱发多核效应，但多核形成的相关机制以及多核细胞的具体生成途径仍未明确。本延伸性研究旨在探究二氧化硅纳米颗粒暴露后多核细胞形成的潜在机制。本研究首先对细胞多核现象进行了考察，随后通过延时共聚焦成像验证多核细胞是否由细胞融合或异常细胞分裂所产生。本研究首次证实，在HepG2细胞中，二氧化硅纳米颗粒诱导的多核效应存在三种形成模式：细胞融合、核分裂而胞质不分裂，以及胞质分裂后发生融合。染色体乘客复合体（chromosomal passenger complex, CPC）缺失，以及细胞周期在G1/S和G2/M检验点发生阻滞，可能是导致细胞胞质分裂异常的原因。激活的丝裂原活化蛋白激酶/细胞外调节蛋白激酶1/2（MAPK/ERK1/2）信号通路，以及有丝分裂相关蛋白表达下调，可能是细胞周期阻滞进而引发多核效应的潜在机制。综上，本研究证实了此前的假说：二氧化硅纳米颗粒暴露后，HepG2细胞的多核效应由胞质分裂异常与细胞融合共同介导。鉴于细胞融合与多核现象与遗传不稳定性及肿瘤发生密切相关，本研究提示二氧化硅纳米颗粒可能具备诱发细胞遗传不稳定性的潜力。上述研究结果引发了人们对二氧化硅纳米颗粒暴露所带来的人体健康危害与环境风险的担忧。