Abstract：Objective To establish a mouse model for short-term exposure to ambient PM and to investigate the impact on the Cytochrome P450 1A1（CYP1A1）and O6-methylguanine-DNA methyltransferase（MGMT）mRNA expression. Methods Twenty 6-week-old BALB/c mice were randomly assigned to one of two groups,each consisting of 5 male and 5 female animals. These mice were then housed in situ concurrently for 2 weeks in our lab located in urban area of Hangzhou. The first group was kept inside an individual ventilated caging（IVC）system equipped with a high-efficiency particulate-air（HEPA）filter,whereas the second was housed inside a IVC with HEPA filter removed. Then it's allowed flow-through of ambient air freely via a pipeline outside. Mice inside the HEPA filtration chamber were therefore protected from exposure to all airborne particulate. The other was in fact exposed to ambient air directly. After the exposure,the bronchoalveolar lavage（BAL）fiuid was collected for each animal and the differentials and percentages of BAL cells were determined. Paraffin sections of lungs of the mice were made and were examined for any inflammation changes. CYP1A1 and MGMT mRNA levels in the lungs were then detected by RT-qPCR. Results The mean concentration of PM2.5 was（99.7±51.6）μg/m3 in the exposure group. Weight increases were similar between the two groups（P>0.05）. The number of total cells and macrophages in BALF from exposure mice was significantly greater than control.A mild inflammation was observed from light photomicrographs of the lung after PM exposure. CYP1A1 and MGMT mRNA levels were significantly up-regulated in the lung from the exposure group. Conclusion A mouse model for short-term exposure to ambient PM was established. CYP1A1 and MGMT may mediate the toxic effect of PM exposure.
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