title: The interaction of manganese nanoparticles with PC-12 cells induces dopamine depletion.
abstract: This investigation was designed to determine whether nano-sized manganese oxide (Mn-40 nm) particles would induce dopamine (DA) depletion in a cultured neuronal phenotype, PC-12 cells, similar to free ionic manganese (Mn(2+)). Cells were exposed to Mn-40 nm, Mn(2+) (acetate), or known cytotoxic silver nanoparticles (Ag-15 nm) for 24 h. Phase-contrast microscopy studies show that Mn-40 nm or Mn(2+) exposure did not greatly change morphology of PC-12 cells. However, Ag-15 nm and AgNO(3) produce cell shrinkage and irregular membrane borders compared to control cells. Further microscopic studies at higher resolution demonstrated that Mn-40 nm nanoparticles and agglomerates were effectively internalized by PC-12 cells. Mitochondrial reduction activity, a sensitive measure of particle and metal cytotoxicity, showed only moderate toxicity for Mn-40 nm compared to similar Ag-15 nm and Mn(2+) doses. Mn-40 nm and Mn(2+) dose dependently depleted DA and its metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), while Ag-15 nm only significantly reduced DA and DOPAC at concentrations of 50 mug/ml. Therefore, the DA depletion of Mn-40 nm was most similar to Mn(2+), which is known to induce concentration-dependent DA depletion. There was a significant increase (> 10-fold) in reactive oxygen species (ROS) with Mn-40 nm exposure, suggesting that increased ROS levels may participate in DA depletion. These results clearly demonstrate that nanoscale manganese can deplete DA, DOPAC, and HVA in a dose-dependent manner. Further study is required to evaluate the specific intracellular distribution of Mn-40 nm nanoparticles, metal dissolution rates in cells and cellular matrices, if DA depletion is induced in vivo, and the propensity of Mn nanoparticles to cross the blood-brain barrier or be selectively uptaken by nasal epithelium.
authors.affiliation: Applied Biotechnology Branch, Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45431, USA. saber.hussain@wpafb.af.mil
authors.forename: Saber M
authors.initials: SM
authors.lastname: Hussain
authors.forename: Amanda K
authors.initials: AK
authors.lastname: Javorina
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Schrand
authors.forename: Helen M
authors.initials: HM
authors.lastname: Duhart
authors.forename: Syed F
authors.initials: SF
authors.lastname: Ali
authors.forename: John J
authors.initials: JJ
authors.lastname: Schlager
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D006719:Homovanillic Acid / Q000378:metabolism; D017895:Manganese Compounds; D049329:Nanostructures / Q000633:toxicity*; D010087:Oxides / Q000633:toxicity*; D016716:PC12 Cells; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D012834:Silver / Q000633:toxicity
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D017382:Reactive Oxygen Species; D015102:3,4-Dihydroxyphenylacetic Acid; D012834:Silver; C027424:manganese oxide; D004298:Dopamine; D006719:Homovanillic Acid