Early-Life Exposure to Traffic-Related Air Pollutants Induced Anxiety-like Behaviors in Rats via Neurotransmitters and Neurotrophic Factors

Recent epidemiological studies have reported significantly increasing hospital admission rates for mental disorders such as anxiety and depression, not only in adults but also in children and adolescents, indicating more research is needed for evaluation of the etiology and possible reduction and prevention of these disorders. The aim of the present study was to examine the associations between perinatal exposure to traffic-related air pollutants and anxiety-like behaviors and alterations in neurological and immunological markers in adulthood using a rat model. Sprague Dawley pregnant rats were exposed to clean air (control), diesel exhaust (DE) 101 ± 9 μg/m3 or diesel exhaust origin secondary organic aerosol (DE-SOA) 118 ± 23 μg/m3 from gestational day 14 to postnatal day 21. Anxiety-related behavioral tests including open field tests, elevated plus maze, light/dark transition tests and novelty-induced hypophagia were performed on 10-week-old rats. The hippocampal expression of neurotransmitters, neurotrophic factors, and inflammatory molecular markers was examined by real-time RT-PCR. Anxiety-like behaviors were observed in both male and female rat offspring exposed to DE or DE-SOA. Moreover, serotonin receptor (5HT1A), dopamine receptor (Drd2), brain-derived neurotrophic factor and vascular endothelial growth factor A mRNAs were significantly decreased, whereas interleukin-1β, cyclooxygenase-2, heme oxygenase-1 mRNAs and microglial activation were significantly increased in both male and female rats. These findings indicate that brain developmental period exposure to traffic-related air pollutants may induce anxiety-like behaviors via modulation of neurotransmitters, neurotrophic factors, and immunological molecular markers, triggering neuroinflammation and microglia activation in rats.