Nano-Sized Secondary Organic Aerosol of Diesel Engine Exhaust Origin Impairs Olfactory-Based Spatial Learning Performance in Preweaning Mice

• Main Authors: Tin-Tin Win-Shwe, Chaw Kyi-Tha-Thu, Yadanar Moe, Fumihiko Maekawa, Rie Yanagisawa, Akiko Furuyama, Shinji Tsukahara, Yuji Fujitani, Seishiro Hirano
• Format: Article
• Language: English
• Published: MDPI AG 2015-06-01
• Series: Nanomaterials
• Subjects: developmental neurotoxicity; diesel exhaust; secondary organic aerosol; olfactory-based learning; preweaning mice; hippocampus; nanotoxicity
• Online Access: http://www.mdpi.com/2079-4991/5/3/1147

The aims of our present study were to establish a novel olfactory-based spatial learning test and to examine the effects of exposure to nano-sized diesel exhaust-origin secondary organic aerosol (SOA), a model environmental pollutant, on the learning performance in preweaning mice. Pregnant BALB/c mice were exposed to clean air, diesel exhaust (DE), or DE-origin SOA (DE-SOA) from gestational day 14 to postnatal day (PND) 10 in exposure chambers. On PND 11, the preweaning mice were examined by the olfactory-based spatial learning test. After completion of the spatial learning test, the hippocampus from each mouse was removed and examined for the expressions of neurological and immunological markers using real-time RT-PCR. In the test phase of the study, the mice exposed to DE or DE-SOA took a longer time to reach the target as compared to the control mice. The expression levels of neurological markers such as the N-methyl-d-aspartate (NMDA) receptor subunits NR1 and NR2B, and of immunological markers such as TNF-α, COX2, and Iba1 were significantly increased in the hippocampi of the DE-SOA-exposed preweaning mice as compared to the control mice. Our results indicate that DE-SOA exposure in utero and in the neonatal period may affect the olfactory-based spatial learning behavior in preweaning mice by modulating the expressions of memory function–related pathway genes and inflammatory markers in the hippocampus.