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Journal of Peking University (Health Sciences) ›› 2020, Vol. 52 ›› Issue (3): 438-443. doi: 10.19723/j.issn.1671-167X.2020.03.007

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Effect of benzo(a)pyrene on dopaminergic neurons and α-synuclein in brain and its mechanism involved

Yu-ze QI,Hui-hui QUAN,Wei-xing XU,Qing-ru LI,Hui ZHOU()   

  1. Department of Occupational and Environmental Health, Peking University School of Public Health, Beijing 100191, China
  • Received:2020-02-18 Online:2020-06-18 Published:2020-06-30
  • Contact: Hui ZHOU E-mail:zhouhui@bjmu.edu.cn
  • Supported by:
    National Natural Science Foundation of China(21577004);Natural Science Foundation of Beijing(7162104)

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Abstract:

Objective: To analyze the effect of benzopyrene on the decrease of dopaminergic neurons, and the increase and aggregation of α-synuclein, which are the pathological features of Parkinson’s disease, and to explore its possible mechanisms.Methods: Eight-month-old transgenic mice with human SNCA gene were randomly divided into a BaP-exposed group and a control group. BaP and solvent corn oil were injected intraperitoneally to BaP-exposed group and control group respectively, once a day for 60 days. The motor dysfunction of mice was tested by rotarod test. The effects of BaP on the decrease of dopaminergic neurons and increase and aggregation of α-synuclein were observed by immunohistochemistry and Western blot experiments respectively, and the expression of related mRNA was detected by quantitative real-time PCR (qRT-PCR). Twenty genes were tested in the study, mainly related to neurotransmitter transporter (2 genes), neurotransmitter receptor function (10 genes), cellular autophagy (5 genes), and α-synuclein aggregation and degradation (3 genes).Results: After BaP exposure, the movement time of the mice in the rotarod test was significantly reduced (P<0.05). The substantia nigra dopami-nergic neurons in the mice were significantly reduced, which was 62% of the control group (P<0.05), and the expression of α-synuclein in the midbrain increased, which was 1.36 times that of the control group (P<0.05). After BaP exposure, mRNA expressions of 14 genes in the midbrain of the mice were significantly down-regulated (P<0.05). Alpha-synuclein degradation and cell autophagy (5 genes), neuron transporters (2 genes), and neurotransmitter receptor functions (5 genes) were involved. The expression of one gene, Synphilin-1, was significantly up-regulated (P<0.01), which was related to α-synuclein aggregation.Conclusion: BaP exposure not only inhibited function of neurotransmitter receptor and dopamine transporter, but also interfered cell autophagy, thereby hindering the degradation of α-synuclein, which could lead to decrease of dopaminergic neurons in substantia nigra and increase and aggregation of α-synuclein in midbrain, as the significant pathology of Parkinson’s disease. Therefore, BaP exposure may increase the risk of Parkinson’s disease.

Key words: Benzo(a)pyrene, Dopaminergic neurons, Alpha-synuclein, Parkinson’s disease

CLC Number: 

  • R12

Table 1

Primer sequences of the target gene"

Genes Forward primer Reverse primer
Alphy-syn degradation and cell autophagy
Beclin1 ATGGAGGGGTCTAAGGCGTC TGGGCTGTGGTAAGTAATGGA
LC3-Ⅱ GACCGCTGTAAGGAGGTGC CTTGACCAACTCGCTCATGTTA
Hspa1a TGGTGCAGTCCGACATGAAG GCTGAGAGTCGTTGAAGTAGGC
Hsc70 TCTCGGCACCACCTACTCC CCCGATCAGACGTTTGGCA
Hsp90 CCAGCAAACAGGACCGAAC GCAATGGTGCCAAGGTTATTGAT
Neurotransmitter transporter
DAT GATGCACATAGCAGCAACTCT GCACACCACGCTCAAAATACTC
Vmat2 ATGCTGCTCACCGTCGTAG GGCAGTCTGGATTTCCGTAGT
Alphy-syn aggregate formation
Synphilin-1 CTTCCCTCTAATGCGCTGGTT CGTTGCGTTTCTTTTGATGTCA
Septin4 ACGGAATCGCAACAAACTGAC TCTTTCTCCCGGATTAGCTTCTC
GAK GGATGGAGCAAAACTTCGGAT TGGAAGACTGTGTAACGAGTGT
Neurotransmitter receptor
Htr1a GACAGGCGGCAACGATACT CCAAGGAGCCGATGAGATAGTT
Htr1d CACCCGCACCTGGAACTTT AGTGGAGGGATGGAGATACAAA
Htr5b CTGGTGAGCGAGTTGTCCG GCGTGATAGTCCAGTAGCGA
Adora2a TTCCACTCCGGTACAATGGC CGATGGCGAATGACAGCAC
Adra1b ACATTGGGGTGCGATACTCTC TTGGGCGCAGGTTCTTTCC
Drd1 GACATACGCCATTTCATCCTCC ATGCGCCGGATTTGCTTCT
Drd2 CAAGCGCCGAGTTACTGTCAT ATGGAGGAGTAGACCACGAAG
Gabra5 TTGGACGGACTCTTGGATGG TGTTCGCACCTGCGTGATT
Hrh3 CTCCGCACCCAGAACAACTT GCACGATGTTGAAGACTGAGG
Lepr GTCTTCGGGGATGTGAATGTC ACCTAAGGGTGGATCGGGTTT

Figure 1

Change of the drop time of rotarod test * P<0.05, compared with the control group."

Figure 2

Immunohistochemistry of dopaminergic neuron in the substantia nigra TH-IR, tyrosine hydroxylase immunoreactivity; SN, substantia nigra. * P<0.05, compared with the control group."

Figure 3

Changes in the expression of α-syn in the midbrain * P<0.05, compared with the control group."

Table 2

Effect of BaP exposure on gene expression"

Genes Multiple of change P value
Alphy-syn degradation and cell autophagy
Beclin1 0.34 0.026
LC3-Ⅱ 0.43 0.023
Hsc70 0.29 0.026
Hspa1a 0.22 0.023
Hsp90 0.33 0.030
Neurotransmitter transporter
DAT 0.24 0.018
Vmat2 0.12 0.032
Alphy-syn aggregate formation
Synphilin-1 3.52 0.016
Septin4 0.18 0.006
GAK 0.50 0.140
Neurotransmitter receptor
Htr1a 0.26 0.007
Htr5b 0.20 0.005
Gabra5 0.26 0.007
Hrh3 0.26 0.008
Lepr 0.31 0.030
Htr1d 0.45 0.140
Adora2a 0.80 0.757
Adra1b 0.40 0.107
Drd1 0.78 0.582
Drd2 0.53 0.155
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