MAPK phosphorylates cMyc and activates MNK, which phosphorylates CREB. By altering transcription factors, MAPK leads to altered transcription of genes important for the cell cycle. Thus, the MAPK pathway

is important in the cellular stress response and modulates a variety of inflammatory responses [15], apoptosis and plays a role in cancer development. Based on our previous demonstration that by SiO2-NPs induced expression of BiP and splicing of XBP-1 mRNA as two markers of ER stress [12], here we aimed to deepen our understanding on ER stress and associated UPR induction and its consequences as well as on oxidative stress and MAPK signaling. By focusing on these important cellular signaling pathways, here we demonstrate that SiO2-NPs up-regulates selleck screening library PP2Ac, induces two pathways of ER stress reaction, activates NFκB, and induces the expression of TNF-α, IFN-α and some of its downstream genes, and thus establish an anti-viral response in human hepatoma cells. We demonstrate that up-regulation of ER stress and associated UPR and interference with IFN and MAPK signaling are important modes of action of SiO2-NPs. SiO2-NP preparation: Fumed SiO2-NPs were purchased from Sigma–Aldrich, Buchs, Switzerland. NPs were weighted, mixed with nano pure water to obtain a stock solution of 1 mg/ml and stirred for

1 h and sonicated in a water bath for 5 minutes. NP suspensions were subsequently Nivolumab price diluted with nano pure water and finally a Oxymatrine 1:2 dilution with

the cell culture medium (without FBS) was done to achieve the final assay concentrations. Before adding the NP dilutions to the cells, the dilutions were mixed again to distribute the NPs as homogenously as possible. Nanoparticle tracking analysis (NTA): SiO2-NPs at a concentration of 1 mg/ml were dispersed in cell culture medium, stirred for 1 h and sonicated in a water bath for 5 minutes. Afterwards the particle size distribution was determined by NanoSight LM10 (NanoSight Ltd., U.K.) followed by evaluation using the Nanoparticle Tracking Analysis (NTA) software. Huh7 cells: The human hepatoma cell line Huh7 was kindly provided by Markus Heim, University Hospital Basel, Switzerland. Cells were grown in DMEM with GlutaMAX™ (LuBioScience, Lucerne, Switzerland) supplemented with 10% FBS in a humidified incubator with 5% CO2 at 37 °C. Cells were usually split every 4 days and sub-cultured at split ratios of about 1:6. RNA isolation, reverse transcription, and quantitative (q)PCR: Total RNA was isolated from Huh7 cells using Trizol reagent according to the manufacturer’s instructions. RNA was reverse transcribed by Moloney murine leukemia virus reverse transcriptase (Promega Biosciences, Inc., Wallisellen, Switzerland) in the presence of random hexamers (Roche) and deoxynucleoside triphosphate. The reaction mixture was incubated for 5 min at 70 °C and then for 1 h at 37 °C. The reaction was stopped by heating at 95 °C for 5 min.