Low-dose Cu exposure enhanced α-synuclein accumulation associates with mitochondrial impairments in mice model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that mainly affects the elder population, and its etiology is enigmatic. Both environmental risks and genetics may influence the development of PD. Excess copper causes neurotoxicity and accelerates the progression of neurodegenerative diseases. However, the underlying mechanisms of copper-induced neurotoxicity remain controversial. In this study, A53T transgenic α-synuclein (A53T) mice and their matching wild-type (WT) mice were treated with a low dose of copper (0.13 ppm copper chlorinated drinking water, equivalent to the copper exposure of human daily copper intake dose) for 4 months, and copper poisoning was performed on human A53T mutant SHSY5Y cells overexpressed with α-synuclein (dose of 1/4 IC50), to test the effects of copper exposure on the body. The results of the open field test showed that the moto function of Cu-treated mice was impaired. Proteomics revealed changes in neurodevelopment, transport function, and mitochondrial membrane-related function in Cu-treated WT mice, which were associated with reduced expression of mitochondrial complex (NDUFA10, ATP5A), dopamine neurons (TH), and dopamine transporter (DAT). Mitochondrial function, nervous system development, synaptic function, and immune response were altered in Cu-treated A53T mice. These changes were associated with increased mitochondrial splitting protein (Drp1), decreased mitochondrial fusion protein (OPA1, Mfn1), abnormalities in mitochondrial autophagy protein (LC3BII/I, P62), decreased dopamine neuron (TH) expression, increased α-synuclein expression, inflammatory factors (IL-6, IL-1β, and TNF-α) release and microglia (Iba1) activation. In addition, we found that Cu2+ (30 μM) induced excessive ROS production and reduced mitochondrial ATP production in human A53T mutant α-synuclein overexpressing SHSY5Y cells by in vitro experiments. In conclusion, low-dose copper treatment altered critical proteins involved in mitochondrial, neurodevelopmental, and inflammatory responses and affected mitochondria's ROS and ATP production levels.