Silica nanoparticles induce autophagosome accumulation via activation of the EIF2AK3 and ATF6 UPR pathways in hepatocytes

InP/ZnS Quantum Dots Cause Inflammatory Response in Macrophages Through Endoplasmic Reticulum Stress and Oxidative stress

Purpose

Quantum dots (QDs) are widely used semiconductor nanomaterials. Indium phosphide/zinc sulfide (InP/ZnS) QDs are becoming potential alternatives to toxic heavy metal-containing QDs. However, the potential toxicity and, in particular, the immunotoxicity of InP/ZnS QDs are unknown. This study aimed to investigate the impacts of InP/ZnS QDs on inflammatory responses both in vivo and in vitro.

Methods

Mice and mouse bone marrow-derived macrophages (BMMs) were exposed to polyethylene glycol (PEG) coated InP/ZnS QDs. The infiltration of neutrophils and the release of interleukin-6 (IL-6) were measured using a hematology analyzer and an enzyme-linked immunosorbent assay (ELISA) for the in vivo test. Cytotoxicity, IL-6 secretion, oxidative stress and endoplasmic reticulum (ER) stress were studied in the BMMs, and then, inhibitors of oxidative stress and ER stress were used to explore the mechanism of the InP/ZnS QDs.

Results

We found that 20 mg/kg PEG-InP/ZnS QDs increased the number of neutrophils and the levels of IL-6 in both peritoneal lavage fluids and blood, which indicated acute phase inflammation in the mice. PEG-InP/ZnS QDs also activated the BMMs and increased the production of IL-6. In addition, PEG-InP/ZnS QDs triggered oxidative stress and the ER stress-related PERK-ATF4 pathway in the BMMs. Moreover, the inflammatory response caused by the PEG-InP/ZnS QDs could be attenuated in the macrophages by blocking the oxidative stress or the ER stress with inhibitors.

Conclusion

InP/ZnS QDs can activate macrophages and induce acute phase inflammation both in vivo and in vitro, which may be regulated by oxidative stress and ER stress. Our present work is expected to help clarify the biosafety of InP/ZnS QDs and promote their safe application in biomedical and engineering fields.

Silica nanoparticles induce spermatocyte cell autophagy through microRNA-494 targeting AKT in GC-2spd cells

Researches had shown that silica nanoparticles (SiNPs) could reduce the quantity and quality of sperms. However, chronic effects of SiNPs have not been well addressed. In this study, mice spermatocyte cells (GC-2spd cells) were continuously exposed to SiNPs (5 μg/mL) for 30 passages and then the changes of microRNA (miRNA) profile and mRNA profile were detected. The function of miRNAs was verified by inhibitors to explore the regulation role of miRNAs in reproductive toxicity induced by SiNPs. The results showed that SiNPs induced cytotoxicity, and activated autophagy in GC-2spd cells. SiNPs led to a total of 1604 mRNAs (697 up-regulated and 907 down-regulated) and 15 miRNAs (6 up-regulated such as miRNA-138 and miRNA-494 and 9 down-regulated) with different expression in GC-2spd cells. The combined miRNA profile and mRNA profile showed that 415 mRNAs with different expression in 5 μg/mL SiNPs group were regulated by miRNA. Furthermore, our study demonstrated that SiNPs decreased the expressions of AKT mRNAs. Moreover, SiNPs had an activation effect on the AMPK/TSC/mTOR pathway. However, inhibitor of miRNA-494 could attenuate the expression levels of AMPK, TSC, LC3Ⅱ and alleviate the decreased of AKT, mTOR, p-mTOR induced by SiNPs. The above results suggested that the low-dose SiNPs exposure could promote autophagy by miRNA-494 targeting AKT, thereby activating AMPK/TSC/mTOR pathway in GC-2spd cells. MiRNA-494 is an important regulator of autophagy by targeting AKT, which provides new evidence for the male reproductive toxicity mechanism of SiNPs.

Endoplasmic Reticulum Stress Cooperates in Silica Nanoparticles-Induced Macrophage Apoptosis via Activation of CHOP-Mediated Apoptotic Signaling Pathway

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.

Silica nanoparticles induce caspase-dependent apoptosis through reactive oxygen species-activated endoplasmic reticulum stress pathway in neuronal cells

Human exposure to silica nanoparticles (SiNPs) has been widely applied as vehicles for drug delivery and cellular manipulations in nanoneuromedicine. SiNPs may cause adverse effects in the brain, but potential mechanisms underlying SiNPs-induced neurotoxicity are remained unclear. Here, we examined cytotoxic effects and the cellular mechanisms of SiNPs-induced neuronal cell death. In this study, the results showed that SiNPs significantly decreased cell viability and induced apoptosis in Neuro-2a cells as evidenced by the increase caspase-3 activity and the activation of caspase cascades and poly (ADP-ribose) polymerase (PARP). In addition, endoplasmic reticulum (ER) stress was triggered as indicated by several key molecules including glucose-regulated protein (GRP)78 and 94, C/EBP homologous protein (CHOP), activation transcription factor (ATF)-4, and caspase-12. Pretreatment of Neuro-2a cells with specific pharmacological inhibitor of ER stress (4-phenylbutyric acid (4-PBA)) effectively alleviated the SiNPs-induced ER stress and apoptotic related signals. Furthermore, 2',7'-Dichlorofluorescein fluorescence as an indicator of reactive oxygen species (ROS) formation after exposure of Neuro-2a cells to SiNPs significantly increased ROS levels. Antioxidant N-acetylcyseine (NAC) effectively reversed SiNPs-induced cellular responses. Taken together, these results suggest that SiNPs exposure exerts its neurotoxicity in cultured neuronal cells by inducing apoptosis via a ROS generation-activated downstream ER stress signaling pathway.

Fine particulate matters induce apoptosis via the ATM/P53/CDK2 and mitochondria apoptosis pathway triggered by oxidative stress in rat and GC-2spd cell

Fine particulate matters (PM_2.5) have been associated with male reproductive toxicity because it can penetrate into the lung's gas-exchange region, and spread to the whole body via circulatory system. Previous studies have shown that PM_2.5 could induce DNA damage and apoptosis by reactive oxygen species (ROS). The aim of the present study is to determine the exact mechanism and role of apoptosis induced by PM_2.5 in spermatocyte cells. Male Sprague-Dawley (SD) rats were treated with normal saline (control group) or PM_2.5 with the doses of 1.8, 5.4 and 16.2 mg/kg bw. via intratracheal instillation every 3 days for 30 days. Mouse spermatocyte-derived cells (GC-2spd cells) were treated with various concentrations (0, 50, 100, 200 μg/mL) of PM_2.5 for 24 h. The results showed that exposure to PM_2.5 resulted in injury of testicular tissue and impaired mitochondria integrity in GC-2spd cells. Moreover, PM_2.5 induced DNA damage and apoptosis in GC-2spad cells via ROS generation, and the ATM/P53/CDK2 and mitochondria apoptosis pathway autophagy signal pathway were activated. N-Acetyl-L-cysteine (NAC), a well-known antioxidant, ameliorated DNA damage, and inhibited apoptosis. These findings demonstrated PM_2.5 might induce apoptosis via the mitochondrial apoptosis pathway through causing DNA damage resulting from oxidative stress, and finally caused spermatogenesis disorder.

Induction of mTOR-dependent autophagy by WS2 nanosheets from both inside and outside of human cells

The applications of two-dimensional transition metal dichalcogenides (2D TMDCs) pose an increased risk to both the environment and human health. Due to the large surface area of 2D nanosheets, they often form multi-layered nanoclusters of various thicknesses in aqueous solution. In this work, we address the safety issue of 2D TMDCs with focus on the cellular effects of the thickness of WS2 nanosheets. At a very low and non-lethal concentration (4 cm2 mL-1 or 25 μg mL-1), 4-layered WS2 nanosheets (WS2-4) were primarily bound to the cell surface with less internalization, while 30-layered WS2 nanosheets (WS2-30) were mostly internalized by human bronchial epithelial cells. Although the cellular interactions at this low concentration caused no alterations in the cell cycle, apoptosis, necrosis and cytotoxicity, cell autophagy was induced in both cases through mTOR-dependent pathways by perturbing a number of signaling molecules, such as amyloid precursor protein (APP) and cysteine-X-cysteine chemokine receptor 4 (CXCR-4). The finding of activation of cell autophagy from both outside and inside of cells reveals a novel feature of biological perturbations by 2D nanosheets. This finding will help in the formulation of general guidelines for the safe application of 2D nanomaterials.

Targeting autophagy using metallic nanoparticles: a promising strategy for cancer treatment

Despite the extensive genetic and phenotypic variations present in the different tumors, they frequently share common metabolic alterations, such as autophagy. Autophagy is a self-degradative process in response to stresses by which damaged macromolecules and organelles are targeted by autophagic vesicles to lysosomes and then eliminated. It is known that autophagy dysfunctions can promote tumorigenesis and cancer development, but, interestingly, its overstimulation by cytotoxic drugs may also induce cell death and chemosensitivity. For this reason, the possibility to modulate autophagy may represent a valid therapeutic approach to treat different types of cancers and a variety of clinical trials, using autophagy modulators, are currently employed. On the other hand, recent progress in nanotechnology offers plenty of tools to fight cancer with innovative and efficient therapeutic agents by overcoming obstacles usually encountered with traditional drugs. Interestingly, nanomaterials can modulate autophagy and have been exploited as therapeutic agents against cancer. In this article, we summarize the most recent advances in the application of metallic nanostructures as potent modulators of autophagy process through multiple mechanisms, stressing their therapeutic implications in cancer diseases. For this reason, we believe that autophagy modulation with nanoparticle-based strategies would acquire clinical relevance in the near future, as a complementary therapy for the treatment of cancers and other diseases.

Exploiting Nanomaterial-mediated Autophagy for Cancer Therapy

Autophagy is a conserved process that is critical for sequestering and degrading proteins, damaged or aged organelles, and for maintaining cellular homeostasis under stress conditions. Despite its dichotomous role in health and diseases, autophagy usually promotes growth and progression of advanced cancers. In this context, clinical trials using chloroquine and hydroxychloroquine as autophagy inhibitors have suggested that autophagy inhibition is a promising approach for treating advanced malignancies and/or overcoming drug resistance of small molecule therapeutics (i.e., chemotherapy and molecularly targeted therapy). Efficient delivery of autophagy inhibitors may further enhance the therapeutic effect, reduce systemic toxicity, and prevent drug resistance. As such, nanocarriers-based drug delivery systems have several distinct advantages over free autophagy inhibitors that include increased circulation of the drugs, reduced off-target systemic toxicity, increased drug delivery efficiency, and increased solubility and stability of the encapsulated drugs. With their versatile drug encapsulation and surface-functionalization capabilities, nanocarriers can be engineered to deliver autophagy inhibitors to tumor sites in a context-specific and/or tissue-specific manner. This review focuses on the role of nanomaterials utilizing autophagy inhibitors for cancer therapy, with a focus on their applications in different cancer types.

Effects of Ultrasonic Dispersion Energy on the Preparation of Amorphous SiO₂ Nanomaterials for In Vitro Toxicity Testing

Synthetic amorphous silica (SAS) constitute a large group of industrial nanomaterials (NM). Based on their different production processes, SAS can be distinguished as precipitated, fumed, gel and colloidal. The biological activity of SAS, e.g., cytotoxicity or inflammatory potential in the lungs is low but has been shown to depend on the particle size, at least for colloidal silica. Therefore, the preparation of suspensions from highly aggregated or agglomerated SAS powder materials is critical. Here we analyzed the influence of ultrasonic dispersion energy on the biologic activity of SAS using NR8383 alveolar macrophage (AM) assay. Fully characterized SAS (7 precipitated, 3 fumed, 3 gel, and 1 colloidal) were dispersed in H₂O by stirring and filtering through a 5 µm filter. Aqueous suspensions were sonicated with low or high ultrasonic dispersion (USD) energy of 18 or 270 kJ/mL, respectively. A dose range of 11.25–90 µg/mL was administered to the AM under protein-free conditions to detect particle-cell interactions without the attenuating effect of proteins that typically occur in vivo. The release of lactate dehydrogenase (LDH), glucuronidase (GLU), and tumor necrosis factor α (TNF) were measured after 16 h. Hydrogen peroxide (H₂O₂) production was assayed after 90 min. The overall pattern of the in vitro response to SAS (12/14) was clearly dose-dependent, except for two SAS which showed very low bioactivity. High USD energy gradually decreased the particle size of precipitated, fumed, and gel SAS whereas the low adverse effect concentrations (LOECs) remained unchanged. Nevertheless, the comparison of dose-response curves revealed slight, but uniform shifts in EC₅₀ values (LDH, and partially GLU) for precipitated SAS (6/7), gel SAS (2/3), and fumed SAS (3/3). Release of TNF changed inconsistently with higher ultrasonic dispersion (USD) energy whereas the induction of H₂O₂ was diminished in all cases. Electron microscopy and energy dispersive X-ray analysis showed an uptake of SAS into endosomes, lysosomes, endoplasmic reticulum, and different types of phagosomes. The possible effects of different uptake routes are discussed. The study shows that the effect of increased USD energy on the in vitro bioactivity of SAS is surprisingly small. As the in vitro response of AM to different SAS is highly uniform, the production process per se is of minor relevance for toxicity.

Endoplasmic reticulum stress mediates inflammatory response triggered by ultra-small superparamagnetic iron oxide nanoparticles in hepatocytes

Ultra-small superparamagnetic iron oxide nanoparticles (USPIO-NPs) are widely used as clinical magnetic resonance imaging contrast agents for hepatic diseases diagnosis. USPIO-NPs often damage the hepatocytes and affect the function of liver but its mechanism of action remains unclear. In the present study, USPIO-NPs caused higher cytotoxicity and lactate dehydrogenase (LDH) leakage in hepatic L02 cells than SPIO-NPs. Subsequently, USPIO-NPs affected more genes' expression than SPIO-NPs analyzed through microarray and bioinformatics analysis. The affected genes were involved in several biological processes, including calcium ion homeostasis, inflammatory response-related leukocyte chemotaxis, and migration. In addition, the level of endoplasmic reticulum (ER) calcium ion was increased by USPIO-NPs. USPIO-NPs also upregulated the genes related to acute-phase inflammation, including IL1B, IL6, IL18, TNFSF12, TNFRSF12, SAA1, SAA2, JAK1, STAT5B, and CXCL14. Furthermore, interleukin-6 (IL-6) secretion was elevated by USPIO-NPs as detected using ELISA. On the other hand, USPIO-NPs changed the morphology of ER and triggered the ER stress and unfolded protein response PERK/ATF4 pathway. Furthermore, blocking ER stress with inhibitor or ATF4 small interfering RNA counteracted IL-6-related acute-phase inflammation and cytotoxicity caused by USPIO-NPs. Taken together, we found that the USPIO-NPs could trigger stronger IL-6-related acute-phase inflammation than SPIO-NPs in hepatocytes. We demonstrated, for the first time, that IL-6-related acute-phase inflammation caused by NPs was regulated by PERK/ATF4 signaling. The PERK/ATF4 pathway explored in this study could be a candidate for diagnostic and therapeutic target against NPs-induced liver injury and cytotoxicity, which would be helpful for USPIO-NPs medical application.