Study On The Hematopoietic Toxicity In Mice Induced By A Combined Exposure Of Formaldehyde And PM_2.5and Its Molecular Mechanism

Data from WHO has indicated that air pollution could put seven million of people to death each year in 2015,resulting in huge social burden.PM2.5 and formaldehyde,respectively,are the main outdoor and indoor pollutants in China,currently,the combined exposure to PM2.5 and indoor formaldehyde has become a common situation,leading to the most prominent health effects.Among all potential hazards,human myeloid leukemia is probably one of the most serious health problems according to the related research.Both two pollutants have been reported to potentially induce hematopoietic toxicity,however,the molecular mechanism remains unclear.This study aimed at the exploration of the effect as well as the underlying mechanism of hematopoietic toxicity induced by PM2.5 and/or formaldehyde.A dual-pathway mechanism mediated by NF-κB,an important transcription factor is proposed for the first time in our study,i.e.,on the one hand,NF-κB can independently activate the ’immune imbalance’ pathway(a promotion of the release of IL-4 and IL-17A by NF-κB,leading to an imbalance of both Thl/Th2 and Treg/Th17,resulting in an inflammation in the bone marrow and finally inducing the hematopoietic toxicity);On the other hand NF-κB can suppress the DNA-repair related mTOR pathway(leading to an irreversible DNA damage of both bone marrow and spleen,the two hematogenic organs available for humans,thus resulting in the hematopoietic toxicity).Based on this mechanism hypothesis,in order to demonstrate solid evidence for the mechanism,systematic studies of hematopoietic toxicity induced by the combined exposure from both in vitro and in vivo were conducted at three levels,which are blood,hematopoietic organs(bone marrow,spleen),and myeloid progenitor,respectively.Male BALB/c mice were used as experimental subjects,mice were divided randomly into eleven experimental groups:(1)fresh air inhalation group(Ctrl);(2)100 mg/kg·d VE group(VE);(3)20 μg/kg·d PM2.5 group(20 PM2.5);(4)160 μg/kg·d PM2.5 group(160 PM2.5);(5)0.5 mg/m3 FA group(0.5 FA);(6)20 μg/kg·d PM2.5 combined with 0.5 mg/m3 FA group(20 PM2 5+0.5 FA);(7)160 μg/kg·d PM2.5 combined with 0.5 mg/m3 FA group(160 PM2.5+0.5 FA);(8)3 mg/m3 FA group(3 FA);(9)20 pg/kg·d PM2.5 combined with 3 mg/m3 FA group(20 PM2.5+3 FA);(10)160 μg/kg·d PM2.5 combined with 3 mg/m3 FA group(160 PM2.5+3 FA);(11)160 μg/kg·d PM2.5 combined with 3 mg/m3 FA and 100 mg/kg·d VE group(160 PM2.5+3 FA+100 VE).Mice were exposed to FA via inhalation,8 hours/day,5 consecutive days/week,and lasted for two weeks.Mice were exposed to PM2.5 by airway instillation,3 times/week,and also lasted for two weeks.After FA and PM2.5 exposure,to detect the biomarkers associated with hematopoietic toxicity.Then complete blood counts and myeloid progenitor(BFU-E,CFU-GM)were measured;The changes of pathology in hematopoietic organ bone marrow and compensatory hematopoietic organ were measured;Colony stimulating factor:GM-CSF,EPO,oxidative stress biomarkers:ROS,GSH,DNA damage biomarkers:DPC,8-OH-dQ,y-H2AX,immune factors:IFN-γ,IL-4,IL-10,IL-17A,DNA damage repair related signal molecule:mTOR,S6K1,FANCD2,ATM and CHk2 were also measured.The results showed that PM2.5 and formaldehyde exposure induced significant reduction of blood cells,BFU-E and CFU-GM,GM-CSF and EPO;Pathological changes occurred in bone marrow and spleen tissues;The levels of ROS and GSH significantly changed;The levels of DPC,8-OH-dG and y-H2AX also significantly increased;The expression of IFN-γand IL-10 significantly decreased,IL-4 and IL-17A significantly increased;The expression of mTOR,S6K1,FANCD2,ATM and CHk2 significantly decreased.While these effects could be blocked by the concurrent administration of Vitamin E.This study has demonstrated that similar effects of hematopoietic toxicity were found in the FA-only exposure group and PM2.5-only exposure group,but the combined exposure to FA and PM2.5 was proved to result in more obvious effect in several indices mentioned above.Reducing the expression level of hematopoietic growth factors,increasing oxidative stress and DNA damages,inhibiting DNA damage repair,activating the ’ immune imbalance’ pathway were proposed the underlying mechanisms of hematopoietic toxicity induced by FA and PM2.5.