Elsevier

Neurobiology of Aging

Volume 91, July 2020, Pages 76-87
Neurobiology of Aging

Regular article
Alterations in the nigrostriatal system following conditional inactivation of α-synuclein in neurons of adult and aging mice

https://doi.org/10.1016/j.neurobiolaging.2020.02.026Get rights and content
Under a Creative Commons license
open access

Highlights

  • Efficient depletion of striatal α-synuclein after adult-onset inactivation of Snca.

  • Nigrostriatal system is not markedly affected by adult-onset depletion of α-synuclein.

  • Changes to striatal dopamine metabolism after α-synuclein depletion in aging animals.

  • Downregulation of ALDH1a1 as a possible cause of striatal dopamine metabolism changes.

Abstract

The etiology and pathogenesis of Parkinson’s disease (PD) are tightly linked to the gain-of-function of α-synuclein. However, gradual accumulation of α-synuclein aggregates in dopaminergic neurons of substantia nigra pars compacta (SNpc) leads to the depletion of the functional pool of soluble α-synuclein, and therefore, creates loss-of-function conditions, particularly in presynaptic terminals of these neurons. Studies of how this late-onset depletion of a protein involved in many important steps of neurotransmission contributes to PD progression and particularly, to worsening the nigrostriatal pathology at late stages of the disease are limited and obtained data, are controversial. Recently, we produced a mouse line for conditional knockout of the gene encoding α-synuclein, and here we used its tamoxifen-inducible pan-neuronal inactivation to study consequences of the adult-onset (from the age of 6 months) and late-onset (from the age of 12 months) α-synuclein depletion to the nigrostriatal system. No significant changes of animal balance/coordination, the number of dopaminergic neurons in the SNpc and the content of dopamine and its metabolites in the striatum were observed after adult-onset α-synuclein depletion, but in aging (18-month-old) late-onset depleted mice we found a significant reduction of major dopamine metabolites without changes to the content of dopamine itself. Our data suggest that this might be caused, at least partially, by reduced expression of aldehyde dehydrogenase ALDH1a1 and could lead to the accumulation of toxic intermediates of dopamine catabolism. By extrapolating our findings to a potential clinical situation, we suggest that therapeutic downregulation of α-synuclein expression in PD patients is a generally safe option as it should not cause adverse side effects on the functionality of their nigrostriatal system. However, if started in aged patients, this type of therapy might trigger slight functional changes of the nigrostriatal system with potentially unwanted additive effect to already existing pathology.

Keywords

Dopaminergic neurons
Substantia nigra
Conditional knockout
Dopamine turnover
Parkinson's disease

Cited by (0)