Qiuling Li

Combined toxicity of silica nanoparticles and methylmercury on cardiovascular system in zebrafish (Danio rerio) embryos

This study was to investigate the combined toxicity of silica nanoparticles (SiNPs) and methylmercury (MeHg) on cardiovascular system in zebrafish (Danio rerio) embryos. Ultraviolet absorption analysis showed that the co-exposure system had high absorption and stability. The dosages used in this study were based on the NOAEL level. Zebrafish embryos exposed to the co-exposure of SiNPs and MeHg did not show any cardiovascular malformation or atrioventricular block, but had an inhibition effect on bradycardia. Using o-Dianisidine for erythrocyte staining, the cardiac output of zebrafish embryos was decreased gradually in SiNPs, MeHg, co-exposure groups, respectively. Co-exposure of SiNPs and MeHg enhanced the vascular endothelial damage in Tg(fli-1:EGFP) transgenic zebrafish line. Moreover, the co-exposure significantly activated the oxidative stress and inflammatory response in neutrophils-specific Tg(mpo:GFP) transgenic zebrafish line. This study suggested that the combined toxic effects of SiNPs and MeHg on cardiovascular system had more severe toxicity than the single exposure alone.

DNA Hypermethylation of CREB3L1 and Bcl-2 Associated with the Mitochondrial-Mediated Apoptosis via PI3K/Akt Pathway in Human BEAS-2B Cells Exposure to Silica Nanoparticles

The toxic effects of silica nanoparticles (SiNPs) are raising concerns due to its widely applications in biomedicine. However, current information about the epigenetic toxicity of SiNPs is insufficient. In this study, the epigenetic regulation of low-dose exposure to SiNPs was evaluated in human bronchial epithelial BEAS-2B cells over 30 passages. Cell viability was decreased in a dose- and passage-dependent manner. The apoptotic rate, the expression of caspase-9 and caspase-3, were significantly increased induced by SiNPs. HumanMethylation450 BeadChip analysis identified that the PI3K/Akt as the primary apoptosis-related pathway among the 25 significant altered processes. The differentially methylated sites of PI3K/Akt pathway involved 32 differential genes promoters, in which the CREB3L1 and Bcl-2 were significant hypermethylated. The methyltransferase inhibitor, 5-aza, further verified that the DNA hypermethylation status of CREB3L1 and Bcl-2 were associated with downregulation of their mRNA levels. In addition, mitochondrial-mediated apoptosis was triggered by SiNPs via the downregulation of PI3K/Akt/CREB/Bcl-2 signaling pathway. Our findings suggest that long-term low-dose exposure to SiNPs could lead to epigenetic alterations.

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.

Silica nanoparticles induced the pre-thrombotic state in rats via activation of coagulation factor XII and the JNK-NF-κB/AP-1 pathway

Silica nanoparticles (SiNPs) play a vital role in medical applications such as drug delivery and cancer therapy. SiNPs can translocate into the bloodstream through all the possible routes of entry. However, there have been scarce studies on the pre-thrombotic effect of SiNPs and the mechanism of the pre-thrombotic state in vivo. We specifically focused on the changes of platelet function and blood coagulation in Wistar rats after 7 consecutive days of intravenous injection of SiNPs (52 nm). The platelet aggregation assay, structural changes of platelet membrane glucoproteins, coagulation test, coagulant/anti-coagulant and fibrinolytic factors and the possible molecular mechanism of pre-thrombotic state formation were performed. Our results demonstrated a significant increase in platelet aggregation rate and platelet activation after SiNP exposure. The clotting time was significantly shortened while fibrinogen (FIB) contents were increased. There were sustained increases in coagulation factors and thrombin–antithrombin complex (TAT) expression induced by SiNPs. Antithrombin III (AT-III) of the SiNP-treated groups was significantly decreased while the concentrations of the tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (t-PA) and D-dimer were elevated. The phosphorylation of nuclear factor-κB/p65 (NF-κB/p65) and activator protein-1/c-Jun (AP-1/c-Jun) and the protein levels of JNK were increased after SiNP exposure. In summary, our results revealed that SiNPs induced the hypercoagulable and pre-thrombotic state in rats through the interaction between platelet activation, coagulation system hyperfunction, anti-coagulation and fibrinolytic resistance. Direct interactions between SiNPs and coagulation factor XII (F XII) and the JNK-NF-κB/AP-1 pathway might be involved in the regulation of pre-thrombotic state formation.