Manufactured nanomaterials (MNMs) selected from a library of over 120 different MNMs with varied compositions, sizes, and surface coatings were tested by four different laboratories for toxicity by high-throughput/-content (HT/C) techniques. The selected particles comprise 14 MNMs composed of CeO, Ag, TiO, ZnO and SiO with different coatings and surface characteristics at varying concentrations. The MNMs were tested in different mammalian cell lines at concentrations between 0.5 and 250 µg/mL to link physical-chemical properties to multiple adverse effects. The cell lines are derived from relevant organs such as liver, lung, colon and the immune system. Endpoints such as viable cell count, cell membrane permeability, apoptotic cell death, mitochondrial membrane potential, lysosomal acidification and steatosis have been studied. Soluble MNMs, Ag and ZnO, were toxic in all cell types. TiO and SiO MNMs also triggered toxicity in some, but not all, cell types and the cell type-specific effects were influenced by the specific coating and surface modification. CeO MNMs were nearly ineffective in our test systems. Differentiated liver cells appear to be most sensitive to MNMs, Whereas most of the investigated MNMs showed no acute toxicity, it became clear that some show adverse effects dependent on the assay and cell line. Hence, it is advised that future nanosafety studies utilise a multi-parametric approach such as HT/C screening to avoid missing signs of toxicity. Furthermore, some of the cell type-specific effects should be followed up in more detail and might also provide an incentive to address potential adverse effects in vivo in the relevant organ.

Several in vitro studies have suggested that silica nanoparticles (NPs) might induce adverse effects in gut cells. Here, we used the human colon cancer epithelial cell line HCT116 to study the potential cytotoxic effects of ingested silica NPs in the presence or absence of serum. Furthermore, we evaluated different physico-chemical parameters important for the assessment of nanoparticle safety, including primary particle size (12, 70, 200, and 500 nm) and surface modification (–NH2 and –COOH). Silica NPs triggered cytotoxicity, as evidenced by reduced metabolism and enhanced membrane leakage. Automated microscopy revealed that the silica NPs promoted apoptosis and necrosis proportional to the administered specific surface area dose. Cytotoxicity of silica NPs was suppressed by increasing amount of serum and surface modification. Furthermore, inhibition of caspases partially prevented silica NP-induced cytotoxicity. In order to investigate the role of specific cell death pathways in more detail, we used isogenic derivatives of HCT116 cells which lack the pro-apoptotic proteins p53 or BAX. In contrast to the anticancer drug cisplatin, silica NPs induced cell death independent of the p53–BAX axis. In conclusion, silica NPs initiated cell death in colon cancer cells dependent on the specific surface area and presence of serum. Further studies in vivo are warranted to address potential cytotoxic actions in the gut epithelium. The unintended toxicity of silica NPs as observed here could also be beneficial. As loss of p53 in colon cancer cells contributes to resistance against anticancer drugs, and thus to reoccurrence of colon cancer, targeted delivery of silica NPs could be envisioned to also deplete p53 deficient tumor cells.

High throughput imaging is used to assess hatching, lethality and malformations in zebrafish embryos and is suitable for hazard ranking of different nanomaterials.

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants, and many are potent carcinogens. Benzo[a]pyrene (B[a]P), one of the best-studied PAHs, is metabolized ultimately to the genotoxin anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE). BPDE triggers stress responses linked to gene expression, cell death and survival. So far, the underlying mechanisms that initiate these signal transduction cascades are unknown. Here we show that BPDE-induced DNA damage is recognized by DNA damage sensor proteins to induce activation of the stress-activated protein kinase (SAPK) p38. Surprisingly, the classical DNA damage response, which involves the kinases ATM and ATR, is not involved in p38-SAPK activation by BPDE. Moreover, the induction of p38-SAPK phosphorylation also occurs in the absence of DNA strand breaks. Instead, increased phosphorylation of p38-SAPK requires the nucleotide excision repair (NER) and DNA damage sensor proteins XPC and mHR23B. Interestingly, other genotoxins such as cisplatin (CDDP), hydrogen peroxide and ultraviolet radiation also enhance XPC-dependent p38-SAPK phosphorylation. In contrast, anti-benzo[c]phenanthrene-3,4-dihydrodiol-1,2-epoxide, the DNA adducts of which are not properly recognized by NER, does not trigger p38-SAPK activation. As a downstream consequence, expression and secretion of the pro-inflammatory cytokine interleukin-6 is induced by BPDE and CDDP in vitro and by CDDP in the murine lung, and depends on XPC. In conclusion, we describe a novel pathway in which DNA damage recognition by NER proteins specifically leads to activation of p38-SAPK to promote inflammatory gene expression.

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