Silica Nanoparticles Induced Epithelial-Mesenchymal Transition in BEAS-2B Cells via ER Stress and SIRT1/HSF1/HSPs Signaling Pathway.

The extensive utilization of amorphous silica nanoparticles (SiNPs) has raised concerns regarding the potential health risks. Previous studies have indicated that SiNPs could trigger both the activation of heat shock proteins (HSPs) and epithelial-mesenchymal transition (EMT) in BEAS-2B cells; however, the underlying mechanisms require further elucidation. This study aimed to investigate how SiNPs activate the heat shock response (HSR) in BEAS-2B cells, which subsequently triggers EMT. Firstly, we observed that SiNPs were internalized by BEAS-2B cells and localized in the endoplasmic reticulum (ER), inducing ER stress. The ER stress led to the activation of SIRT1 by phosphorylation, which enhanced the nuclear transcriptional activity of HSF1 via deacetylation. HSF1 was found to upregulate the levels of HSP70 and HSP27 proteins, which further affected EMT-related genes and, ultimately, induced EMT. Additionally, 4-phenylbutyric acid (4-PBA) inhibited ER stress, which attenuated the SIRT1/HSF1 signaling pathway. The knockdown of SIRT1 and HSF1 using siRNA effectively suppressed the EMT progression. In summary, these results suggested that SiNPs activated the SIRT1/HSF1/HSPs pathway through ER stress, thereby triggering EMT in BEAS-2B cells. The present study identified a novel mechanism of SiNP-induced EMT, which has provided valuable insights for future toxicity studies and risk assessments of SiNPs.