Zinc release from mitochondria contributes to MPP+-induced lysosomal disruption and neuronal death

Abstract Autophagy dysregulation and lysosomal dysfunction are critical in Parkinson’s disease. However, the cause and pathogenic signaling of the lysosomal functional deficiency is unknown. Here, we report on the role of zinc as a link between mitochondrial damage and lysosomal depletion. A mitochondrial toxin, 1-methyl-4 phenylpyridinium (MPP⁺), increased reactive oxygen species (ROS) and intracellular zinc ([Zn2+]i), causing lysosomal membrane permeabilization (LMP) and cell death. Supporting this, antioxidant or zinc chelator significantly reduced MPP⁺-induced LMP and neuronal death, whereas lysosomal protease inhibitors attenuated neuronal death but not ROS and [Zn2+]i. Whereas H₂O₂ toxicity was almost completely attenuated in Metallothionein-3 (MT-3) knock-out (KO) astrocytes, zinc overload- or MPP⁺-induced toxicity increased in MT-3 KO astrocyte cultures, suggesting that MT-3 modulates excessive zinc rather than providing a source of zinc after MPP⁺ treatment. Next, mitochondria-deficient Rho 0 cells were used to determine whether mitochondria are a source of zinc. No increase in ROS, [Zn2+]i, LMP, or MPP⁺ toxicity was observed in Rho 0 cells compared to wild-type cells, suggesting that increased ROS and [Zn2+]i by MPP⁺ originated from mitochondria. Taken together, we suggest that LMP is induced by the release of zinc after mitochondrial damage, eventually leading to neuronal death and lysosomal deficiency. Conduct of future studies will be needed to determine whether zinc is involved in MPP+-induced blocking of autophagic flux and accumulation of α-synuclein.