Particulate matter increases beta-amyloid and activated glial cells in hippocampal tissues of transgenic Alzheimer's mouse: Involvement of PARP-1

Exposure to air pollutants, such as particulate matter (PM), has been implicated in neurodegenerative disorders including Alzheimer's disease (AD). However, direct effects of PM on production of beta-amyloid (A beta), a key pathogenic molecule in AD, and its underlying mechanism are still elusive. Given PM's potential to induce oxidative stress in other tissues, we hypothesized that poly(ADP-ribose) polymerase (PARP-1) might be involved in PM-induced neurotoxicity. To address this, we used an ex vivo model of AD, the organotypic hippocampal slice tissue culture from old (12-14 months-of-age) triple transgenic 3xTg-AD mice. First, we observed that fine PM (aerodynamic diameter < 4 mu m) can dose-dependently activate PARP-1 and decrease NAD(+) levels in Neuro2A cells. PARP-1 activation did occur under concentrations of PM which did not affect cell viability. Next, we observed that direct treatment of PM increased A beta levels and activated glial cells in the ex vivo hippocampal tissues of 3xTg-AD mice. PM-induced glial activation was most prominent in CA1 region of the hippocampal tissue. Notably, we found that pharmacological inhibition of PARP-1 reversed both PM-induced A beta increase and glial activation, arguing the possible involvement of PARP-1 in PM-induced AD pathogenesis. Our findings suggest that PARP-1 might be a potential molecular target, responsible for mediating negative effects of PM on the brain. Modulating PARP-1 activity could be a promising approach to prevent or alleviate PM-related environmental neurotoxicity which could initiate AD pathogenesis. (C) 2018 Elsevier Inc. All rights reserved.