[Effect of airborne particulate matter exposure on pregnancy and fetal development in female mice]

To investigate subacute exposure of airborne particulate matter (PM) on pregnancy and fetal development in female mice.

Forty female and forty male ICR adult mice were caged separately by 1:1 to get access to pregnancy. The pregnant mice were randomized into control group (A), small (B), middle (C), large (D) or overdose (E) PM challenge groups (n = 8-11), and were administered with 30 µl of phosphate buffered solution (A) or resuspended standard PM SRM 1649a at 0.09 (B), 0.52 (C), 1.85 (D) or 69.2 (E) µg/µl, once per trid from d 0 till d 19 of pregnancy via instillation onto the base of the tongue. Fetal mice were harvested by cesarean section at the time when spontaneous delivery occurred. Body weight of the pregnant mice, gestational days, intrauterine survival and growth, hepatic and pneumonic histopathological changes of the fetal mice were investigated. Lung/body and liver/body weight ratios were calculated. Expressions of mRNA and protein of CYP1A1 in the fetal lung and CYP1A2 in the fetal liver were assayed.

(1) All of the pregnant mice survived pregnancy throughout the entire experiment. Body weight of the pregnant mice was not significantly different among all the groups at gestational d 1 and 7 (P > 0.05), but significantly lower in group E [(41.8 ± 5.8) and (48.9 ± 8.9) g] than in group A [(45.9 ± 1.8) and (56.2 ± 4.9) g] at gestational d 14 and 18 (P < 0.05). The gestational days were significantly decreased in group E [(19.3 ± 1.3) d] when compared with group A [(20.5 ± 0.7) d; P < 0.05] and were not significantly different among groups A, B, C and D (P > 0.05). Lung/body and liver/body weight ratios of the fetal mice were significantly increased in group E [(1.21 ± 0.18) and (4.68 ± 0.21)%] as compared with groups A, B, C and D (P < 0.05). (2) Mortality rates of the fetuses were significantly higher in group E (23.0%) than in groups A (0.8%), B (0.9%), C (1.7%) and D (3.7%) (P < 0.05), but were not significantly different among groups A, B, C and D (P > 0.05) despite of an increasing tendency. (3) Pathological changes in the liver and lung of the fetuses were conspicuous in group E. The fetal liver injury was histopathologically evidenced by deranged tissue structure, degenerated parenchyma of hepatic cells, and mildly stained cytoplasm. Adipose degeneration was represented by clear-boundary intracytoplasmic vacuoles in most of the liver cells, and cell pyknosis with heavily stained cytoplasm was observed in some of the liver cells. Inflammatory cell infiltration and focal necrosis were occasionally found in the hepatic tissue. The fetal lung exhibited bronchiole with narrow lumina, vascular engorgement in the submucosal layer, interstitial and alveolar edema, thickened alveolar septum, granulocyte and lymphocyte infiltrations within the pulmonary alveoli and around the bronchioles. The above pathological changes were lesser in groups C and D, and were not or least found in groups A and B. (4) Protein expressions of CYP1A1 in the fetal lung and CYP1A2 in the fetal liver were significantly increased in group E (1.20 ± 0.40 and 2.55 ± 0.89) when compared with group A (0.77 ± 0.36 and 2.08 ± 0.31) (P < 0.05). mRNA expressions of CYP1A1 in the fetal lung were significantly increased in groups C (0.36 ± 0.12), D (0.41 ± 0.08) and E (0.43 ± 0.11) compared with group A (0.21 ± 0.10), and significantly increased in groups D and E compared with group B (0.28 ± 0.10, P < 0.05). mRNA expressions of CYP1A2 in the fetal liver were significantly increased in groups C (0.37 ± 0.13), D (0.36 ± 0.14) and E (0.43 ± 0.16) compared with group A (0.21 ± 0.03), and significantly increased in group E compared with group B (0.24 ± 0.11, P < 0.05).

PM elicited embryotoxigenicity and resulted in adverse pregnancy outcomes in mice by intrauterine exposure of overdose PM. The expressions of cancer-related genes CYP1A1 and CYP1A2 were up-regulated in organs after the middle- and large-dose subacute exposure of PM, which may have a potential role on the future development.