At seeming safe concentrations, synergistic effects of PM2.5 and formaldehyde co-exposure induces Alzheimer-like changes in mouse brain

Abstract

Alzheimer’s disease (AD) is a serious, common, global disease, yet its etiology and pathogenesis are incompletely understood. Air pollution is a multi-pollutants co-exposure system, which may affect brain. The indoor environment is where exposure to both air particulate matter (<2.5 μm in diameter) (PM_2.5) and formaldehyde (FA) can occur simultaneously. Whether exposure to such a multi-pollutant (PM_2.5 plus FA) mixture contributes to the development of AD, and whether there is a difference between exposure to PM_2.5 or FA alone needs to be investigated. To determine the objective, C57BL/6J mice were exposed daily to PM_2.5 (0.193 mg/Kg/day), FA (0.155 mg/Kg/day) or multi-pullutants (0.193 mg/Kg/day PM_2.5 plus 0.155 mg/Kg/day FA) for one week. AD-like changes and upstream events were investigated after exposure. The results showed that exposure to PM_2.5 or FA alone in this study had little or no adverse effects on the mouse brain. However, some AD-like pathologies were detected after multi-pullutants co-exposure. This work suggested PM_2.5 plus FA co-exposure has more potential to induce AD-like pathologies than exposure alone. Oxidative stress and inflammation may be involved into the toxic mechanisms. Synergistic effects of co-exposure may induce the hygienic or safety standards of each pollutant not safe.