Effects Of Maternal Exposure To Microplastics On The Neurobehavior Of Offspring Zebrafish And Its Mechanism

Microplastics(MPs)are plastic particles less than 5 mm in diameter.They are frequently detected in various foods.Polystyrene microplastics(PS-MPs)are one of the most common types of microplastics in the environment,which can induce the neurotoxicity of mice,zebrafish,nematodes and other animals.Because the developing nervous system is relatively weak,the early life stage of animals is sensitive for many pollutants.Previous studies have shown that PS-MPs are easy to accumulate in the ovaries of animals and may be transmitted to offspring through the eggs,suggesting that the maternal exposure of MPs has a potential threat to nervous system function of the offspring.However,studies on such toxic effects and mechanisms are extremely limited.In this study,zebrafish(Danio rerio)was used as the experimental animal to construct the maternal exposure model of MPs based on food sources.The fluorescence of PS-MPs,behavioral parameters,biomarkers of neurotransmitter system,apoptosis level of brain cells,expression level of dopaminergic system related genes,oxidative stress level and other related indicators were used to investigate the maternal transfer characteristics of PS-MPs and the effects on the neurobehavior of offspring zebrafish when maternal exposure to PS-MPs with the different doses(1%,10% of the diet)and different times(7,14,21 d).Besides,5 μM antioxidant N-acetylcysteine(NAC)was added to antagonize oxidative stress and to explore the role of oxidative stress in maternal PS-MPs induced neurobehavioral abnormalities in zebrafish.Through the research,the following results are obtained:1.Maternal transfer,accumulation,retention and tissue distribution of PS-MPs.PS-MPs(200 nm)can be transferred from the female parent to the offspring through eggs.The accumulation of PS-MPs increases with the increase of exposure time and dose,and stays in the offspring zebrafish for more than 5 days.Moreover,maternal PSMPs were mainly distributed in the yolk sac of offspring zebrafish.2.PS-MPs affect the growth and development of offspring zebrafish.PS-MPs can reduce the gonad index and spawning capacity of female parents,and lead to premature hatching and increased heart rate of offspring zebrafish.3.PS-MPs affect the neurobehavior of offspring zebrafish.(1)PS-MPs affect the movement distance,cumulative duration of moving and movement speed of offspring zebrafish under light-dark cycle stimulation.(2)PS-MPs can decrease the acetylcholinesterase activity and increase the dopamine content of offspring zebrafish,which interferes with the neurotransmitter system.(3)PS-MPs can increase the number of apoptotic bodies in the brain cells of offspring zebrafish and up-regulate the level of brain cells apoptosis.(4)PS-MPs can affect the expression levels of genes related to dopamine synthesis(th1,th2),receptor(drd1)and degradation(mao),and interfere with the normal function of dopaminergic system in offspring zebrafish.4.PS-MPs can induce oxidative stress in offspring zebrafish.PS-MPs can significantly increase the levels of reactive oxygen species and malondialdehyde in offspring zebrafish.5.5 μM NAC can significantly alleviate oxidative stress of offspring zebrafish.5 μM NAC can decrease the reactive oxygen species and malondialdehyde levels of offspring zebrafish in exposed group to normal level without affecting control group.6.NAC treatment can significantly alleviate the neurobehavioral abnormalities of offspring zebrafish induced by maternal PS-MPs exposure.After NAC treatment,(1)the movement distance,cumulative duration of moving and movement speed of offspring zebrafish tend to be normal;(2)the acetylcholinesterase activity and dopamine content of offspring zebrafish tend to be normal;(3)the apoptosis level of brain cells in the offspring zebrafish tend to be normal;(4)the relative expression levels of mao and drd1 tend to be normal.In conclusion,maternal exposure of PS-MPs based on food sources affects locomotor behavior,acetylcholinesterase activity,dopamine content,apoptosis level of brain cells,and expression of dopaminergic system-related genes of offspring zebrafish.Further studies showed that maternal exposure of PS-MPs induced apoptosis of offspring zebrafish brain cells,decreased acetylcholinesterase activity and increased dopamine content,interfered with locomotor behavior under light and dark cycles,and altered dopaminergic nervous system related gene expression through oxidative stress.This study provides new experimental evidence for potential risk and harm of maternal transfer of PS-MPs.It is of great significance to evaluate the intergenerational toxic effects of PS-MPs.