Effects Of Lanthanum Exposure On Autophagy And Apoptosis In Hippocampal Nerve Cells Of Offspring Rats And The Interaction Study

Objective:Rare earth elements?REEs?are kinds of chemical substance represented by lanthanum,which are widely used in many fields due to their unique physical and chemical properties.At the same time,rare earth elements also enter the organism through environmental media and food chains and accumulate in the body.The residue of rare earth elements in the environment and their impact on human health have become a public concern.The epidemiological survey found that the IQ level of children in the rare earth mining area was significantly lower than that in the control areas.Animal experiments have also confirmed that rare earth elements can cause neurobehavioral changes,learning and memory disorders,and central nervous system developmental defects.Because of its active chemical properties,Lanthanum has become a representative of the study of rare earth elements.Therefore,clarifying the neurotoxic mechanism of lanthanum is of great theoretical and practical significance for finding effective molecular intervention targets and protecting children's health.Methods:80 healthy SPF adult Wistar rats?half male and half female?weighing240±10g were provided by experimental animal center of China Medical University?license number:SYXK?liao?2013-0001?.The feeding environment of experimental animals:indoor temperature was 22±1?,relative humidity was 45?55%,day and night time was 12h,animals eat and drink freely.Female animals were randomly divided into control group lanthanum?drink distilled water?,low dose LaCl₃ group?drink distilled water containing 0.25%LaCl₃ solution?,middle dose of LaCl₃ group?drink distilled water containing 0.5%LaCl₃ solution?and high dose of LaCl₃ group?drink distilled water containing 1.0%LaCl₃ solution?after adapted to the surrounding environment for 1 week.Each group has 10 female animals,then mated with 10 male animals.The next morning sperm was found in the vaginal,which was regarded as pregnancy successfully and recorded the zero day of pregnancy,and start to exposure to LaCl₃.Each group of rats was exposure to La by sucking milk from birth to weaning.After weaning,rats were permitted free to access to food and drinking water for 1 month.The Morris water maze test was used to test the spatial learning and memory abilities.The ultra-structural changes in the cytoplasm,mitochondria and endoplasmic reticulum of the hippocampal neurons and the formation and quantity of autophagosomes were observed by transmission electron microscopy.Flow cytometry was used to detect the apoptotic rate and necrosis rate of nerve cells.Real-time PCR was used to determine the Bcl-2,the Bcl-x L,caspase-3,caspase-6,Bad,Bnip3,Bid,Noxa,Puma,Cytc mRNA transcription situation.Expression levels of bcl-2,bcl-xl,caspase-3,caspase-6,Bad,Bnip3,Bid,Noxa Puma,Beclin1 C-terminal fragment,cytoplasmic and mitochondrial Cytc proteins were determined by Western blot.Results:1.Effects of lanthanum on learning and memory of offspring rats.In the space-positioning navigation test,with the increase of the exposure dose of lanthanum,the escape latency and swimming distance of the offspring rats gradually increased.Compared with the control group,the path of finding the underwater platform was messy and purposeless and the swimming distance also increased.In the space exploration experiment,as the exposure dose of lanthanum increased,the number of crossed the platform and the time spent in the target quadrant gradually decreased;compared with the control group,the rats search platform without aim,even rarely entered the target quadrant.2.The effect of lanthanum exposure on the morphology of hippocampal neurons in the rat brain.In the lanthanum group,autophagosomes with bilayer membrane structure were found,and the mitochondria were also abnormally swollen and the endoplasmic reticulum expanded.3.The effect of lanthanum exposure on the apoptosis rate of hippocampal neurons in the rat brain.Compared with the control group,the apoptotic rate of hippocampal neurons in the brain increased gradually with the increase of the dose of lanthanum,and there was significant statistically difference between the groups.4.La exposure can up-regulate the expression of Bad,Bnip3,Bid,Noxa,Puma and Caspase3/6,Beclin1 C-terminal fragment,and cytoplasmic Cytc.Conclusion:1.Exposure to lanthanum can significantly reduce the spatial learning and memory ability of experimental animals.2.Exposure to lanthanum promotes phosphorylation of Bcl-2 and Beclin 1,up-regulates the expression of Bad,Bnip3,Bid,Noxa,Puma and Caspase 3/6,which promotes the depolymerization of Beclin1/Bcl-2 and Beclin 1/Bcl-x L dimers.Therefore,this can activate autophagy in nerve cells abnormally,and the number of pro-apoptotic proteins is significantly increased,resulting in a significant increase in the apoptotic rate of nerve cells.