Functionally charged polystyrene particles activate immortalized mouse microglia (BV2): cellular and genomic response

Abstract

The effect of particle surface charge on the biological activation of immortalized mouse microglia (BV2) was examined. Same size (∼850–950 nm) spherical polystyrene microparticles (SPM) with net negative (carboxyl, COOH-) or positive (dimethyl amino, CH₃)₂-N- zeta potentials were exposed to BV2 microglia (5–20 µl/ml). Both stimulated an oxidative burst, increased Caspase 3/7 activity and caused inflammatory cytokine release. Ultrastructure indicated that SPM particles were phagocytosed as single particles but formed large intra-cellular 4–6 µm agglomerates. Microarray analysis indicated that negatively charged SPM-COOH- affected approximately 146 genes while the positively charged SPM-(CH₃)₂-N- affected approximately 2580 genes. Only 30 genes were significantly affected in common. Of the 48 genes associated with oxidative stress pathways, 33 genes were coordinately down-regulated by SPM-(CH₃)₂-N- and up-regulated by SPM-COOH- exposure. Together, these data indicate that functionally charged, inert submicron-size particles differentially activate BV2 microglia along oxidative stress and inflammatory pathways.

• Submicron-size particles
• particle toxicity
• surface charge
• zeta potential
• microglia
• oxidative stress
• BV2

Acknowledgements

The authors wish to thank Dr John Hong, National Institute of Environmental Health Sciences, RTP, NC for the BV2 microglia cell line.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This document has been reviewed by the National Health and Environmental Effects Research Laboratory and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute the endorsement of recommendation for use.