Copper·Dopamine Complex Induces Mitochondrial Autophagy Preceding Caspase-independent Apoptotic Cell Death

Abstract

Parkinsonism is one of the major neurological symptoms in Wilson disease, and young workers who worked in the copper smelting industry also developed Parkinsonism. We have reported the specific neurotoxic action of copper⅐dopamine complex in neurons with dopamine uptake. Copper⅐dopamine complex (100 M) induces cell death in RCSN-3 cells by disrupting the cellular redox state, as demonstrated by a 1.9-fold increase in oxidized glutathione levels and a 56% cell death inhibition in the presence of 500 M ascorbic acid; disruption of mitochondrial membrane potential with a spherical shape and well preserved morphology determined by transmission electron microscopy; inhibition (72%, p < 0.001) of phosphatidylserine externalization with 5 M cyclosporine A; lack of caspase-3 activation; formation of autophagic vacuoles containing mitochondria after 2 h; transfection of cells with green fluorescent protein-light chain 3 plasmid showing that 68% of cells presented autophagosome vacuoles; colocalization of positive staining for green fluorescent protein-light chain 3 and Rhod-2AM, a selective indicator of mitochondrial calcium; and DNA laddering after 12-h incubation. These results suggest that the copper⅐dopamine complex induces mitochondrial autophagy followed by caspase-3-independent apoptotic cell death. However, a different cell death mechanism was observed when 100 M copper⅐dopamine complex was incubated in the presence of 100 M dicoumarol, an inhibitor of NAD(P)H quinone:oxidoreductase (EC 1.6.99.2, also known as DT-diaphorase and NQ01), because a more extensive and rapid cell death was observed. In addition, cyclosporine A had no effect on phosphatidylserine externalization, significant portions of compact chromatin were observed within a vacuolated nuclear membrane, DNA laddering was less pronounced, the mitochondria morphology was more affected, and the number of cells with autophagic vacuoles was a near 4-fold less.

Overexpression of alpha-synuclein at non-toxic levels increases dopaminergic cell death induced by copper exposure via modulation of protein degradation pathways

“…Cu-dopamine complex induces mitochondrial autophagy (mitophagy) and apoptotic cell death (Paris et al, 2009). We observed that CuCl 2 induced a dose-dependent accumulation of the autophagosome markers GFP-LC3 puncta (Fig.…”

“…Cu-induced toxicity has been shown to be potentiated by dopamine (Paris et al, 2001, 2009). The human SK-N-SH neuroblastoma cell line used here has been reported to have low levels of tyrosine hydroxylase activity (Klongpanichapak et al, 2008; West et al, 1977).…”

Industrial toxicants and Parkinson's disease

“…A major target of oxidative damage appears to be the mitochondria (Rossi et al, 2004). Indeed, recent reports have suggested that mitochondria are preferentially damaged following exposure to copper (Paris et al, 2009). Alteration to mitochondria function has long been appreciated as a potential pathogenic cascade in PD, most notably, through the aberrant generation of oxidative species following damage (Schapira, 2008).…”

Molecular and Neurochemical Mechanisms Dopamine Oxidation To O-Quinones in Parkinson’s Disease Pathogenesis

“…The depletion of NADPH results in a decrease in reduced glutathione because NADPH is required for the enzymatic reduction of glutathione. Several reports demonstrate that the one-electron reduction of aminochrome is a neurotoxic reaction both in cell cultures and in vivo [27,28,32,33,54,[56][57][58][59][60][61][62][81][82][83][84][85][86].…”

“…Copper sulfate has been reported to catalyze dopamine oxidation, and high exposure to this metal in the mining industry has been associated with a Parkinsonism syndrome [26]. Copper(II) forms a complex with dopamine that is taken up specifically by dopamine transporters into dopaminergic neurons, where dopamine is oxidized to an aminochrome that induces mitochondrial autophagy preceding caspase-independent apoptotic cell death [27,28]. Interestingly, a study on Wilson's syndrome where 282 patients were evaluated for 3 decades revealed that Parkinsonism is the most common clinical symptom in this disease [29].…”