Cationic nanoparticles induce caspase 3-, 7- and 9-mediated cytotoxicity in a human astrocytoma cell line

Abstract

On a daily basis we are exposed to cationic nanoparticulates in many different ways. They are known to distribute to many organs of the body, and while some evidence suggests that these nanoparticles are toxic to cells, the mechanism of their toxicity is not clear. Here we apply a combination of biochemical and imaging techniques to study the mechanism by which amine-modified polystyrene nanoparticles induce cell death in a human brain astrocytoma cell line. Flow cytometry analysis of cells exposed to cationic nanoparticles revealed an increase in cell membrane permeability of the dyes YoPro-1 and propidium iodide, indicating onset of an apoptotic followed by a secondary necrotic response. Activation of caspases 3/7 and 9 and cleavage of poly(ADP-ribose) polymerase (PARP)-1 was also detected, providing clear molecular evidence of the apoptotic pathway induced by the nanoparticles. Transmission electron microscopy also revealed that these nanoparticles induce morphological changes in lysosomes and mitochondria, consistent with our observation of a rapid increase in the formation of reactive oxygen species in these cells. Together these results suggest that amine-modified polystyrene nanoparticles can mediate cell death through an apoptotic mechanism mediated by damage to the mitochondria.

Keywords::

• Amine-modified nanoparticles
• apoptosis
• caspases 3/7 and 9 activation
• 1321N1 human astrocytoma cells

Acknowledgements

We wish to thank Dr Alfonso Blanco and the Flow Cytometry Core Facility from the UCD Conway Institute, Dr David Cottell of the Electron Microscopy Core Facility, and Dr Bas Boots of the School of Biology and Environmental Science for help with statistical analyses.

Declaration of interest: MGB was supported by the Portuguese Fundação para a Ciência e Tecnologia (SFRH/BD/15892/2005). This work was conducted with the framework of the INSPIRE Programme funded by the Higher Education Authority Programme for Research at Third Level Institutes, cycle 4 (FW), and is based upon works supported by the Science Foundation Ireland (SFI) under grant number SFI/SRC/B1155. Additional funding from EPA (2008-EH-MS-h, FF), EUFP6 (SIGHT and NanoInteract) is gratefully acknowledged. The JCS lab is supported by a Principal Investigator grant (09/IN.1/B2604) from SFI. The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.