Temporal dependence of neuronal alpha-synuclein oligomerization and nuclear translocation induced by paraquat

[Background] Paraquat (PQ), one of the environmental poisons associated with sporadic Parkinson's disease (PD), can cause abnormal aggregation of alpha-synuclein (α-syn), but the research on its conformational changes and subcellular localization is limited. [Objective] To investigate the effect of PQ on α-syn conformation and subcellular localization in dopaminergic neurons. [Methods] Forty-eight SPF C57BL/6 male mice were selected and randomly divided into a control group and a model group. The model group was intraperitoneally injected with PQ (15 mg·kg−1), and the control group was intraperitoneally injected with 0.9% normal saline, twice a week for eight weeks to construct a PD-like mouse model. The changes of neurobehavior (by open field test and pole climbing test) were observed to evaluate motor ability of mice. Immunohistochemical staining (IHC) was used to detect the expression levels of tyrosine hydroxylase (TH) and α-syn in the midbrain. Western blotting (WB) was used to measure the protein expression levels of TH and α-syn in midbrain. Human neuroblastoma SH-SY5Y cells were used as dopaminergic neuron in vitro models. After the cells were treated with PQ (100 μmol·L−1) for 0, 12, 24, 36 and 48 h, the expressions of α-syn in whole cell, cytoplasm, and nucleus were detected by WB; the expression level of extracellular α-syn was detected by enzyme-linked immunosorbent assay (ELISA); the change of α-syn location was observed by immunofluorescence assay (IFA). [Results] The neurobehavioral tests' results showed that compared with the control group, the residence time in peripheral area of mice in the PQ model group increased with the increase of exposure time (P