MilliporeSigma
  • Impairment of Atg5-dependent autophagic flux promotes paraquat- and MPP⁺-induced apoptosis but not rotenone or 6-hydroxydopamine toxicity.

Impairment of Atg5-dependent autophagic flux promotes paraquat- and MPP⁺-induced apoptosis but not rotenone or 6-hydroxydopamine toxicity.

Toxicological sciences : an official journal of the Society of Toxicology (2013-09-03)
Aracely Garcia-Garcia, Annandurai Anandhan, Michaela Burns, Han Chen, You Zhou, Rodrigo Franco
ABSTRACT

Controversial reports on the role of autophagy as a survival or cell death mechanism in dopaminergic cell death induced by parkinsonian toxins exist. We investigated the alterations in autophagic flux and the role of autophagy protein 5 (Atg5)-dependent autophagy in dopaminergic cell death induced by parkinsonian toxins. Dopaminergic cell death induced by the mitochondrial complex I inhibitors 1-methyl-4-phenylpyridinium (MPP⁺) and rotenone, the pesticide paraquat, and the dopamine analog 6-hydroxydopamine (6-OHDA) was paralleled by increased autophagosome accumulation. However, when compared with basal autophagy levels using chloroquine, autophagosome accumulation was a result of impaired autophagic flux. Only 6-OHDA induced an increase in autophagosome formation. Overexpression of a dominant negative form of Atg5 increased paraquat- and MPP⁺-induced cell death. Stimulation of mammalian target of rapamycin (mTOR)-dependent signaling protected against cell death induced by paraquat, whereas MPP⁺-induced toxicity was enhanced by wortmannin, a phosphoinositide 3-kinase class III inhibitor, rapamycin, and trehalose, an mTOR-independent autophagy activator. Modulation of autophagy by either pharmacological or genetic approaches had no effect on rotenone or 6-OHDA toxicity. Cell death induced by parkinsonian neurotoxins was inhibited by the pan caspase inhibitor (Z-VAD), but only caspase-3 inhibition was able to decrease MPP⁺-induced cell death. Finally, inhibition of the lysosomal hydrolases, cathepsins, increased the toxicity by paraquat and MPP⁺, supporting a protective role of Atg5-dependent autophagy and lysosomes degradation pathways on dopaminegic cell death. These results demonstrate that in dopaminergic cells, Atg5-dependent autophagy acts as a protective mechanism during apoptotic cell death induced by paraquat and MPP⁺ but not during rotenone or 6-OHDA toxicity.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Methyl viologen dichloride hydrate, 98%
Sigma-Aldrich
Anti-LC3B antibody produced in rabbit, ~1 mg/mL, affinity isolated antibody, buffered aqueous solution
Roche
Cytotoxicity Detection Kit (LDH), suitable for protein quantification, suitable for cell analysis, detection, sufficient for ≤2,000 tests