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Parkinson's disease (PD) is mainly attributed to degeneration of dopamine neurons in the substantia nigra, but its etiopathogenesis also includes impaired protein clearance and axonal transport dysfunction, among others. The spread of α-synuclein (α-syn) aggregates from one neuron to another, in a prion-like manner, is hypothesized to contribute to PD progression. Axonal transport is likely to play a crucial role in this movement of α-syn aggregates between brain regions. At the same time, deficits in axonal transport are suggested to contribute to neuronal failure in PD. In this review, we discuss the apparent contradiction that axonal transport might be essential for disease progression, while dysfunction of axonal transport could simultaneously be a cornerstone of PD pathogenesis. We speculate around models that reconcile how axonal transport can play such a paradoxical role.

Mitochondrial and autophagic dysfunction as well as neuroinflammation are involved in the pathophysiology of Parkinson's disease (PD). We hypothesized that targeting the mitochondrial pyruvate carrier (MPC), a key controller of cellular metabolism that influences mTOR (mammalian target of rapamycin) activation, might attenuate neurodegeneration of nigral dopaminergic neurons in animal models of PD. To test this, we used MSDC-0160, a compound that specifically targets MPC, to reduce its activity. MSDC-0160 protected against 1-methyl-4-phenylpyridinium (MPP+) insult in murine and cultured human midbrain dopamine neurons and in an α-synuclein-based Caenorhabditis elegans model. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice, MSDC-0160 improved locomotor behavior, increased survival of nigral dopaminergic neurons, boosted striatal dopamine levels, and reduced neuroinflammation. Long-term targeting of MPC preserved motor function, rescued the nigrostriatal pathway, and reduced neuroinflammation in the slowly progressive Engrailed1 (En1+/-) genetic mouse model of PD. Targeting MPC in multiple models resulted in modulation of mitochondrial function and mTOR signaling, with normalization of autophagy and a reduction in glial cell activation. Our work demonstrates that changes in metabolic signaling resulting from targeting MPC were neuroprotective and anti-inflammatory in several PD models, suggesting that MPC may be a useful therapeutic target in PD.