Abstract
While silica nanoparticles (SiNPs) have wide applications, they inevitably increase atmospheric particulate matter and human exposure to this nanomaterial. Numerous studies have focused on how to disclose SiNP toxicity and on understanding its toxic mechanisms. However, there are few studies in the literature reporting the interaction between endoplasmic reticulum (ER) stress and SiNP exposure, and the corresponding detailed mechanisms have not been clearly determined. In this study, CCK-8 and flow cytometry assays demonstrated that SiNPs gradually decreased cell viability and increased cell apoptosis in RAW 264.7 macrophage cells in dose- and time-dependent manners. Western blot analysis showed that SiNPs significantly activated ER stress by upregulating GRP78, CHOP, and ERO1α expression. Meanwhile, western blot analysis also showed that SiNPs activated the mitochondrial-mediated apoptotic signaling pathway by upregulating BAD and Caspase-3, and downregulating the BCL-2/BAX ratio. Moreover, 4-phenylbutyrate (4-PBA), an ER stress inhibitor, significantly decreased GRP78, CHOP, and ERO1α expression, and inhibited cell apoptosis in RAW 264.7 macrophage cells. Furthermore, overexpression of CHOP significantly enhanced cell apoptosis, while knockdown of CHOP significantly protected RAW 264.7 macrophage cells from apoptosis induced by SiNPs. We found that the CHOP-ERO1α-caspase-dependent apoptotic signaling pathway was activated by upregulating the downstream target protein ERO1α and caspase-dependent mitochondrial-mediated apoptotic signaling pathway by upregulating Caspase-3 and downregulating the ratio of BCL-2/BAX. In summary, ER stress participated in cell apoptosis induced by SiNPs and CHOP regulated SiNP-induced cell apoptosis, at least partly, via activation of the CHOP-ERO1α-caspase apoptotic signaling pathway in RAW 264.7 macrophage cells.
Highlights
Following the rapid development of nanotechnology, the potential harmful health effects of nanomaterial have aroused the public’s widespread attention during the past decades [1,2]
silica nanoparticles (SiNPs) used in this study were near-spherical, porous, and unmodified
The diameter of SiNPs determined by transmission electron microscope (TEM) was 5–15 nm (Figure 1A), which was consistent with the size provided by the manufacturer
Summary
Following the rapid development of nanotechnology, the potential harmful health effects of nanomaterial have aroused the public’s widespread attention during the past decades [1,2]. Due to the unique physicochemical properties of nanoparticles (NPs), they can reach various tissues and organs in the whole body, and penetrate the body’s protective barriers, such as the blood brain barrier, to increase the risk of toxicity to humans and animals. Among these NPs, silica nanoparticles (SiNPs) are a popular inorganic material for engineered nanoparticles. SiNPs are currently on the priority lists for toxicological evaluation by the Organization for Economic Cooperation and Development (OECD) [10]. It is a prerequisite for the application of SiNPs to fully disclose its toxicity and deeply understand its toxic mechanisms
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