Amorphous silica nanoparticles cause abnormal cytokinesis and multinucleation through dysfunction of the centralspindlin complex and microfilaments

Abstract

Abstract Background: With the large-scale production and application of amorphous silica nanoparticles (aSiNPs), it’s the adverse health effects that are more worthy of our attention. Our previous research has demonstrated for the first time that aSiNPs induced cytokinesis failure, which resulted in abnormally high incidences of multinucleation in vitro, but the underlying mechanisms remain unknown. Therefore, the purpose of this study was firstly to explore whether aSiNPs induced multinucleation in vivo, and secondly to investigate the underlying mechanism of how aSiNPs caused abnormal cytokinesis and multinucleation.Methods: Male ICR mice with intratracheal instillation of aSiNPs were used as an experimental model in vivo. Human hepatic cell line (L-02) was introduced for further mechanism study. Results: In vivo, histopathological results showed that the rate of multinucleation was significantly increased in liver and lung tissue after aSiNPs treatment. In vitro, immunofluorescence results manifested that aSiNPs directly caused microfilaments agglomeration. Following mechanistic studies indicated that aSiNPs not only induced excessive ROS and down-regulation of the PI3k 110β/Aurora B pathway, but also inhibited the expression of centralspindlin subunits MKLP1 and CYK4 as well as downstream cytokines regulation related proteins Ect2, Cep55, CHMP2A and RhoA. Meanwhile, the particles caused abnormal co-localization of the key mitotic regulatory kinase Aurora B and the centralspindlin complex, which resulted in incomplete cytokinesis. To further clarify the role of PI3K inhibition and excessive ROS in cytokinesis failure induced by aSiNPs, PI3K activator IGF and ROS inhibitors NAC were selected. In the aSiNPs treated group, IGF increased the phosphorylation level of Aurora B and improved the relative ratio of the centralspindlin cluster; and NAC reduced the ratio of multinucleation, alleviated the PI3k 110β/Aurora B pathway inhibition, and then increased the expression of MKLP1, CYK4 and cytokinesis-related proteins, whilst it simultaneously directly restored the clustering of the centralspindlin.Conclusion: This study demonstrated that aSiNPs led to multinucleation formation both in vivo and in vitro. aSiNPs exposure caused microfilaments agglomeration and inhibited the PI3k 110β / Aurora B pathway through excessive ROS, which then hindered the centralspindlin cluster as well as restrained the expression of centralspindlin subunits and cytokinesis-related proteins, which ultimately created cytokinesis failure and the formation of multinucleation.