Effects Of BDE 209 Exposure During Pregnancy And After Birth On Hematology In Mice

Objective: The polybrominated diphenyl ethers(PBDEs) are a group of widely used flame retardants including 209 congeners. Due to their environmental persistency and bioaccumulation in biological species, such as human breast milk, umbilical cord blood and fetal liver, some PBDE congeners have been classified as persistent organic pollutants(POPs). Compared to lower brominated PBDEs, BDE 209 has lower toxicity and is less expensive and therefore has been largely used in China, though banned in European countries and in the USA. The levels of BDE 209 in fetal livers increase with the time of gestation, predisposing the developing fetuses to potential adverse effects. The studies on PBDEs toxicity have been focusing on neurotoxicity, neurodevelopmental toxicity, immunotoxicity and endocrine toxicity. Few studies on hematopoietic system have been reported. The present study was to investigate the effects of long-term exposure to BDE 209 during pregnancy and breastfeeding and after birth on some of the endpoints in blood system in offspring mice. A preliminary study was also carried out to assess the blood burden of some PBDEs in children with acute leukemia, in comparison with the patient controls with no blood disorders.Method: 1. Animal study:(1) Establishing BDE 209 exposure mice models: The animal study was carried out at the Dalian Medical University Laboratory Animal Research Center(SPF). Briefly, 75 female Kunming mice were randomly assigned to control(vehicle), low dose(1.5 mg/kg·d) and high dose(225 mg/kg·d) groups. After exposure to BDE 209 for10 days through gavage, female mice were allowed to mate with healthy male mice until conception was confirmed. For each treatment group, 8 female mice with similar conception date(± 2 days) were selected for further treatment throughout the pregnancy and breastfeeding. After weaning, the offspring mice(F1 generation) were treated through gavage. The F2 offspring mice were made using the same protocol as the F1.(2) Throughout the observation period, the animals were closely monitored for overall conditions, including food and water consumption, body weight, hair and behaviors.(3) Laboratory examination on peripheral blood of the offspring mice, including white blood cell(WBC) system, red blood cell(RBC) system and platelet cell(PLC) system.(4) Histological examination on peripheral blood of the offspring mice.(5) Morphological examination of bone marrow cells in the offspring mice.(6) Bone marrow karyotyping in the offspring mice. 2. Human study(a case?control study): To evaluate the potential of PBDEs to contribute to the blood disorders, the body burden of some PBDE congeners were examined in children with acute lymphocytic leukemia through the questionnaire and measurement of PBDEs in peripheral blood using the gas phase mass spectrometry(GC?MS) method. The control patients were selected from children hospitalized for other diseases in the same Dalian regional hospital.Result: 1. Animal study:(1) The gender effect of BDE 209 on body weight of offspring was observed: in F1 offspring mice, only high dose BDE 209 exposure significantly decreased the body weight in female mice at postnatal day 30(PND 30)(P<0.05), while both BDE 209 doses led to decrease in body weight in male mice on the same PND 30(P<0.05 or P<0.01). In F2 offspring mice, high dose of BDE 209 resulted in significant decrease in body weight of female on PND 16, 60 and 90(P<0.01), and male mice responded only at PND 30(P<0.01); low dose BDE 209 led to a decrease in body weight in both genders at PND 30(P<0.01).(2) Peripheral blood examination. WBC system: BDE 209 did not lead to much change in F1 offspring mice, while a dose- and time-dependent effect and gender effect were observed in F2 mice. Specifically, high BDE 209 exposure led to a decrease in the total cell count in F2 male mice at PND 30(P<0.05), and low dose BDE 209 led to a decrease in the total cell count in F2 male mice at PND 60(P<0.05), in particular neutrophils(P<0.01). The high dose BDE209 led to an increase in the quantity of neutrophils in F2 female mice at PND 30(P<0.05) but a decrease at PND 60 and 90(P<0.05); the low dose BDE 209 only decreased the quantity of neutrophils in F2 female mice at PND 90(P<0.01). The quantities of lymphocytes was decreased by low dose BDE 209 in F2 male mice at PND 60 and 90(P<0.05 or P<0.01). High dose BDE 209 affected the quantity of monocytes only in F2 female mice PND 60(P<0.05). RBC system: the cell count, the level of hemoglobins and hematokrits significantly decreased in F1 male mice by both BDE 209 doses at PND30(P<0.05 or P<0.01); F1 female mice showed a decrease in hematokrit only at PND 30(P<0.05). BDE 209 exposure had greater influence on RBC system of F2 offspring mice and there was little gender difference. Overall, both experimental groups decreased significantly in the quantity of WBC, the level of hemoglobin and hematokrit(P<0.05 or P<0.01). PLC system: at PND 30, high dose BDE 209 led to a decrease in the cell count of PLC in both genders of F1 mice, and low dose BDE 209 led to changes only in female mice(P<0.05 or P<0.01). In F2 mice, BDE 209 has generally caused an increase in the cell count of PLC.(3) Peripheral blood histology: abnormalities in F1 mice at PND 30 and 60 by low dose BDE 209, and at PND 90 by high dose BDE 209 were detected, as shown by increased quantities of white cells. One case of abnormal hyperchromatic lymphocytes appeared in cluster was observed in low dose group at PND 90.(4) Bone marrow pathology: low dose BDE 209 led to changes in bone marrow in some F1 mice manifested as hyperplasia at PND 60 and 90, and no gender difference was found. One case of abnormal bone marrow hyperplasia was observed in F1 male mice by high dose treatment at PND 90 with huge bare nucleus cells appeared. The segmented cells in bone marrow smear were observed, taking up about 25-30% of the karyotes, in both male and female F2 mice at PND 120 by high dose BDE 209 exposure.(5) Bone marrow karyotyping: the examination on the quantity of chromosomes detected no changes.2. Epidemiological studies results: 31 child patients with acute lymphocytic leukemia and 3 control patients with no blood disorders were tested for four types of PBDEs burden in serum, including BDE 47, 99, 100 and 153. The significant increases in BDE 47,100 and 153 were observed for children with acute leukemia, compared with the controls.Conclusion: Long-term BDE 209 exposure may potentially cause blood disorders in offspring mice, possibly through interfering with cell proliferation and differentiation in bone marrow. The finding that the blood level of PBDEs in the serum of children with acute leukemia increased significantly compared with that of the control group, suggests that PBDEs may be one of the potential environmental factors underlying childhood leukemia.