Switching on microglia with electro-conductive multi walled carbon nanotubes

We explored the mechanisms underlying microglia cell-carbon nanotube interactions in order to investigate whether electrical properties of Carbon-Nanotubes (CNTs) could affect microglia brain cells function and phenotype. We analyzed the effects induced by highly electro-conductive Multi-Walled-Carbon-Nanotubes (alpha-MWCNTs), on microglia cells from rat brain cortex and compared the results with those obtained with as prepared not conductive MWCNTs (MWCNTs) and redox-active Double-Walled-Carbon-Nanotubes (DWCNTs). Cell viability and CNT capacity to stimulate the release of nitric oxide (NO), pro-inflammatory (IL-1 beta, TNF-alpha) and anti-inflammatory (IL-10, TGF-beta 1) cytokines and neurotrophic factors (mNGF) were assessed. Electro-conductive MWCNTs, besides not being cytotoxic, were shown to stimulate, at 24 h cell exposure, classical M1 microglia activation phenotype, increasing significantly the release of the main pro-inflammatory cytokines. Conversely, after 48 h cell exposure, they induced the transition from classical M1 to alternative M2 microglia phenotype, supported by anti-inflammatory cytokines and neuroprotective factor mNGF release. The analysis of cell morphology change, by tubulin and CD-206 thorn labelling showed that M2 phenotype was much more expressed at 48 h in cells exposed to a-MWCNTs than in untreated cells. Our data suggest that the intrinsic electrical properties of CNTs could be exploited to modulate microglia phenotype and function stimulating microglia anti-inflammatory potential. (c) 2017 Elsevier Ltd. All rights reserved.