title: Nanosize titanium dioxide stimulates reactive oxygen species in brain microglia and damages neurons in vitro.
abstract: BACKGROUND
  Titanium dioxide is a widely used nanomaterial whose photo-reactivity suggests that it could damage biological targets (e.g., brain) through oxidative stress (OS).
  
  
  OBJECTIVE
  Brain cultures of immortalized mouse microglia (BV2), rat dopaminergic (DA) neurons (N27), and primary cultures of embryonic rat striatum, were exposed to Degussa P25, a commercially available TiO(2) nanomaterial. Physical properties of P25 were measured under conditions that paralleled biological measures.
  
  
  RESULTS
  P25 rapidly aggregated in physiological buffer (800-1,900 nm; 25 degrees C) and exposure media (approximately 330 nm; 37 degrees C), and maintained a negative zeta potential in both buffer (-12.2 +/- 1.6 mV) and media (-9.1 +/- 1.2 mV). BV2 microglia exposed to P25 (2.5-120 ppm) responded with an immediate and prolonged release of reactive oxygen species (ROS). Hoechst nuclear stain was reduced after 24-hr (>or=100 ppm) and 48-hr (>or=2.5 ppm) exposure. Microarray analysis on P25-exposed BV2 microglia indicated up-regulation of inflammatory, apoptotic, and cell cycling pathways and down-regulation of energy metabolism. P25 (2.5-120 ppm) stimulated increases of intracellular ATP and caspase 3/7 activity in isolated N27 neurons (24-48 hr) but did not produce cytotoxicity after 72-hr exposure. Primary cultures of rat striatum exposed to P25 (5 ppm) showed a reduction of immunohistochemically stained neurons and microscopic evidence of neuronal apoptosis after 6-hr exposure. These findings indicate that P25 stimulates ROS in BV2 microglia and is nontoxic to isolated N27 neurons. However, P25 rapidly damages neurons at low concentrations in complex brain cultures, plausibly though microglial generated ROS.
authors.affiliation: Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, North Carolina, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Long
authors.forename: Julianne
authors.initials: J
authors.lastname: Tajuba
authors.forename: Preethi
authors.initials: P
authors.lastname: Sama
authors.forename: Navid
authors.initials: N
authors.lastname: Saleh
authors.forename: Carol
authors.initials: C
authors.lastname: Swartz
authors.forename: Joel
authors.initials: J
authors.lastname: Parker
authors.forename: Susan
authors.initials: S
authors.lastname: Hester
authors.forename: Gregory V
authors.initials: GV
authors.lastname: Lowry
authors.forename: Bellina
authors.initials: B
authors.lastname: Veronesi
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D004298:Dopamine / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017072:Neostriatum / Q000166:cytology / Q000196:embryology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D011506:Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism* / Q000494:pharmacology; D014025:Titanium / Q000633:toxicity*
chemical_list: D011506:Proteins; D017382:Reactive Oxygen Species; C009495:titanium dioxide; D014025:Titanium; D004298:Dopamine