Suppression of sonic hedgehog pathway-based proliferation in glioblastoma cells by small-size silver nanoparticles in vitro.

Glioblastomas (GBs) are one of the most aggressive and invasive intracranial cancers. Recently, it has been postulated that, among other factors, the hedgehog (HH) pathway may be a key factor in this phenomenon. Moreover, it has been reported that small-size silver nanoparticles (AgNPs) are characterized by a high cytotoxic effect towards GBs. However, their effect on the sonic hedgehog (SHH) pathway has never been demonstrated in any cancer cells. Therefore, the aim of the present study was to evaluate the impact of the anti-proliferative properties of 5-nm AgNPs on the SHH pathway in the GB cell line (U-87MG) in vitro. The results showed a time- and dose-dependent decrease in the metabolic activity in the U-87MG cells treated with AgNPs, with IC50 reaching 30.41 and 21.16 µg/mL after 24 h and 48 h, respectively, followed by an increase in the intracellular reactive oxygen species (ROS) level. The co-treatment of the cells with AgNPs and Robotnikinin (SHH inhibitor) abolished and/or strengthened the effect of AgNPs, especially on the SHH mRNA levels and on the PCNA, PTCH1, Gli1, and SUFU protein levels. Interestingly, no changes in the level of ERK1/2, Akt, and SRC kinase protein expression were detected, suggesting a direct impact of AgNPs and/or ROS on the inhibition of the canonical SHH pathway. However, more studies are needed due to the increase in the mTOR protein expression after the treatment of the cells with AgNPs, as in the Robotnikinin treatment. In conclusion, small-size AgNPs are able to inhibit the proliferation of GB cells in vitro by suppressing the canonical SHH pathway.

Crosstalk between the aryl hydrocarbon receptor (AhR) and the peroxisome proliferator-activated receptor gamma (PPARγ) as a key factor in the metabolism of silver nanoparticles in neuroblastoma (SH-SY5Y) cells in vitro.

The potential usefulness of silver nanoparticles (AgNPs) in anticancer therapy has been postulated for many years. However, little is known to date about the exact impact of such NPs on intracellular detoxication pathways. Therefore, the aim of this study was to determine the impact of AgNPs on the AhR-PPARγ-CYP1A1 pathway in neuroblastoma (SH-SY5Y) cells. The obtained results showed a decrease in the metabolic activity of the SH-SY5Y cells at the 50 and 100 µg/mL concentrations with an increase in caspase-3 activity. An increase in the intercellular ROS production was observed at the 1 and 10 µg/mL concentrations. The co-treatment of the AgNP-treated cells with the AhR and PPARγ inhibitors abolished the effect of the tested AgNPs in the SH-SY5Y cells. In turn, the CYP1A1 activity assay showed a decrease in this parameter in the AgNP-treated cells. Moreover, the gene expression analysis demonstrated that AgNPs were able to increase the AhR and CYP1A1 mRNA expression and decrease the PPARγ gene expression after the 6-h treatment. In turn, an increase in the AhR and PPARγ protein expression was observed after 24 h. Summarizing, the study shows for the first time that AgNPs with a 5-nm diameter size are able to exert a cytotoxic effect on SH-SH5Y cells in a ROS-dependent manner affect the AhR-PPARγ-CYP1A1 pathway inter alia by inhibiting the activity of CYP1A1. This is important due to given present research approaches using such NPs as enhancer agents in the modern PPARγ inhibitor-based anticancer therapy.