Postnatal Subacute Benzo(a)Pyrene Exposure Caused Neurobehavioral Impairment And Metabolomics Changes Of Cerebellum In The Early Adulthood Period Of Sprague-dawley Rats

PART 1 THE EFFECT OF SUBACUTE EXPOSURE OF BENZO(A)PYRENE ON NEUROBEHAVIORALAND CEREBELLUM NERVE STRUCTURE IN ADULT RATSObjective: To observe the effects of postnatal subacute exposure to BaP on the nervous behavior and cerebellum nervous structure in the early period of adult rats by establishing the model of postnatal subacute exposed to BaPMethods:Thirty-four healthy male neonatal Sprague-Dawley(SD)rats aged postnatal day(PND)4 and their maternal rats were purchased from the animal center of Chongqing Medical University(Chongqing,China).All animals were kept in the standard laboratory conditions.Each neonatal rat was marked in an individual number on the feet or body by a nontoxic ink.All neonatal rats were randomly divided into control group and BaP-treated group(2mg/kg).The BaP-treated group of rat were administered via oral gavage BaP each day with a dose of 2mg/kg,the control group rats received the same dose of corn oil.After 7 weeks,the open field test was used to evaluate the autonomic behavior,explore behavior and the anxiety behavior.The ultrastructural change of cerebellar neurons observed under electron microscope.Results: The rats in the BaP-treated group had significantly higher total distance locomotor activity compared with the control group rats(Fig.1A,t=6.039,P<0.000),but the difference in the time of the locomotor activity was not statistically significant(Fig.1B,t=0.077,P=0.940).Moreover,the number of central activities(Fig.1C,t=2.263,P=0.040)and rearing activities performed by the BaP-treated group was significantly increased(Fig.1D,t=2.426,P=0.029).Moreover,the BaP treated-group showed ultrastructural features of typical cellular swelling.The characterization of cellular swelling in the BaP-treated group was local swelling which was recognized by a pale and watery cytoplasm under electron microscopic analysis,and swollen organelles,including mitochondria deformation and endoplasmic reticulum expansion(Fig.2F),which were obvious in the cell body and the neuropil.Conclusion: subacute postnatal BaP oral exposure may have subsequent effects on the development of rat cerebellum.PART 2 THE EFFECT OF POSTNATAL EXPOSURE TO BaP ON CEREBELLAR METABOLISM IN THE EARLY PERIOD OF ADULTHHOOD RATSObjective: to measure the metabolism of the cerebellum after BaP exposure by GC-MS,and discussion the influence of metabolism in the rat cerebellum through analyzing the data of metabolomics.Methods: the cerebellar tissue was measure by GC-MS.The data was normalized using an internal standard and weight of the brain tissue.Principal component analysis(PCA)was used to observe the distribution of metabolic substances in all samples,and partial least-squares discriminate analysis(PLS-DA)was used to distinguish the differences between the control group and the BaP-treated group by SIMCA-P 11.5.Significantly changed compounds were selected based on their variable of importance in the project(VIP)value.The Student's t-test was use to test the significant difference in the metabolites between the two group.VIP>1 and P<0.05 were used to screen meaningful metabolites.Metabolic pathway analysis was performed by the website of Metaboanalyst,followed by network analysis performed by software Metscape to select the main affected pathway.Results : The GC-MS metabolomics profiling of the cerebellum samples produced a total of 120 compounds across the two groups,Based on the PLS-DA(VIP>1)and t-test(P <0.05),20 differential metabolites were identified in the cerebellum between the control group and BaP-treated group.20 metabolites are mainly related to energy metabolism,methionine metabolism and glutathione metabolism.Conclusion: BaP exposure can lead to metabolic disorders in cerebellum through influencing cerebellar energy metabolism?methionine metabolism and glutathione mentalism.