Reproductive Toxicity And Multigenerational Transmission Effects Of Diesel Particulate Matter Based On Caenorhabditis Elegans

Diesel particulate matter(DPM)is a dominant contaminant of atmospheric environmental pollution.Owing to high energy efficiency,high heat rate,and low cost,diesel engines have been widely used in many feilds,including heavy truck work,engineering machinery,and ships.DPM is a major contaminant component of fine particulate matter(PM2 5)and has been proved to induce harmful effects to human beings,including lung cancer,allergies,and chronic bronchitis.There have been reported on sperm quality of mice after DPM treatment.However,little attention has been paid to the transgenerational effects of DPM because of the limitations of experimental animals.In this study,the model organism C.elegans was used to explore the developmental and reproductive toxicity of DPM on the parental generation(FO).Single exposure in the parental generation and continuous exposure for five generations was performed to clarify the transgenerational toxic effects of DPM.The main findings of the study are as follows:1.The physicochemical properties of DPM:Scanning electron microscopy(SEM)revealed that the surface of the DPM showed a loose and porous morphology,which easily adsorbed heavy metals.Using physicochemical analysis and characterization techniques such as inductively coupled plasma mass spectrometry(ICP-MS),energy dispersive X-ray spectroscopy,and the transmission electron microscopy,it was found that the surface of DPM contains various heavy metal components.The dynamic light scattering instrument(DLS)analysis revealed that the DPM aqueous solution has good dispensability and can keep this state for a long time.2.DPM exposure induced developmental and reproductive toxicity of parental nematodes:N2 was exposed to different concentrations of DPM solution to evaluate impact on the body length,life span,germ line cell apoptosis and brood size.The results showed that body length,life span,number of brood size and oocytes decreased,and the number of apoptosis of gonad cells increased with the increase of DPM concentration.At the same dose,reproductive endpoint of nematodes is more sensitive than developmental endpoints.3.Using different C.elegans mutant strains,we found:(1)After the DNA cored apoptosis signaling strains were exposed to DPM,it was found that the ced-9(n1950)mutant strain had a significantly higher germline apoptosis level than N2,and the germline apoptosis of ced-3(n717)and ced-4(n1162)were almost completely disappeared.(2)After the DNA-damage-responsive gene-deficient strains were exposed to DPM,it was found that the number of germline apoptotic cells in egl-1(n487),hus-1(op241)and cep-1(w40)did not change significantly compared with the control group.The DNA-damage response genes play a key role in DPM-induced apoptosis in C.elegans gonad cells.(3)After the MAPK kinase core family ERK,JNK and p38 signaling pathway-deficient strains were exposed to DPM,it was found that the number of germline apoptotic cells exposure group decreased to the level of the control group,indicating that the ERK signaling transduction pathway is required for DPM-induced nematode germ cell apoptosis.The JNK signaling pathway and the p38 signaling pathway is essential for DPM-induced apoptosis of germline cells.4.Maternal and multigenerational exposure toxicity:(1)In the case where only the parental FO generation was exposed to the DPM,the number of brood size in the F2 generation decreased significantly compared with the corresponding exposure concentration group,but recovered to the FO generation spawning level in the F3-F5 generation.After exposure to DPM,the abnormal F1 germ cells might be transferred from the FO generation,and they show abnormal gonad development on the F1 generation.In spite of normal ovulation and fertilization,the F1 generation might produce a weaker F2 generation which could be related to low reproduction rate.Meanwhile,the F2 germ cell from the F1 generation was maintained under normal conditions.The F2 generation could produce a normal F3 generation,and they can recover the reproduction rate as normal states.(2)In the case of continuous exposure to DPM in F0-F5 generation,the number of germ line cell apoptosis in F1-F5 generation was significantly higher than that in unexposed group,but there was no significant difference between each generation;the number of brood size decreased gradually,showing a significant effect.In summary,the diesel particulate matter contained a variety of heavy metal oxides,polycyclic aromatic hydrocarbons and nitro-polycyclic aromatic hydrocarbons,and the composition is complicated.It has a good dispersibility in Milli-Q water and could be fully mixed and suspended in the exposure solutions.The DNA cored apoptotic pathway-deficient,DNA-damage-responsive gene-deficient and MAPK signaling pathway are essential for DPM-induced apoptosis of germline cells.These results provided a new data reference to the reproductive toxicity of atmospheric fine particulate matter.Furthermore,DPM can affect the brood size and quality of F2 individuals by damaging F1 generation germ cells,and this result provides new evidence for multi-generation toxicity studies of atmospheric fine particles.