Effects Of An Autophagy/lysosomal Pathway On The Death Of Dopaminergic Cells

Aim: To study the role of an autophagy/lysosomal pathway in 6-OHDA-induced death of dopaminergic cells in PD models.Methods: In this study, we established two PD models in vivo and in vitro. Rats model were produced with stereotaxic administration of 6-OHDA into unilateral substantia nigra par compact (SNpc). SH-SY5Y cells were administrated with 6-OHDA. Autophagosomes in SNpc were observed with transmission electronmicro-scopy (TEM). Autophagosomes in SH-SY5Y cells were observed by MDC staining. Proteins related to apoptosis and autophagy were determined with immuno-fluorescence (IF) and Western blot. Effects of autophagy/lysosome inhibitors on 6-OHDA-induced cathepsin L and NF-κB activation were also detected. TUNEL assay was applied to detect apoptosis.Results: TEM revealed that the formation of autophagosomes in the ipsilateral SNpc after injection of 6-OHDA. MDC staining also showed that autophagosomes appeared in SH-SY5Y cell induced by 6-OHDA. Immunofluorescence demonstrated that expression of lamp-1, cathepsin B, L and LC3 increased after 6-OHDA treatment. Pretreatment with inhibitors can potentiated the cytotoxicitiy of 6-OHDA in the earlier stage, while it attenuated 6-OHDA-induced death in the later period. Nuclear-location of Cathepsin L and NF-κB p65was induced by 6-OHDA. Pretreatment with inhibitors downregulated 6-OHDA-induced activation of LC3, cathepsin L and NF-κB, also reduced the number of TUNEL-positive cells.Conclusions: The increase of autophagosomes and the activation of lysosomes may be involved in the toxicity induced by 6-OHDA. Autophagy/lysosome pathway may have a crosstalk with apoptosis mediated by NF-κB. Autophagy can be protective in the earlier stage of 6-OHDA administration, while promote the death of dopaminergic cells in the later period by activating autophagy/lysosome-mediated death pathways.