Chronic exposure to manganese decreases striatal dopamine turnover in human alpha-synuclein transgenic mice

Neuroscience. 2011 Apr 28;180:280-92. doi: 10.1016/j.neuroscience.2011.02.017. Epub 2011 Feb 16.

Abstract

Interaction of genetic and environmental factors is likely involved in Parkinson's disease (PD). Mutations and multiplications of alpha-synuclein (α-syn) cause familial PD, and chronic manganese (Mn) exposure can produce an encephalopathy with signs of parkinsonism. We exposed male transgenic C57BL/6J mice expressing human α-syn or the A53T/A30P doubly mutated human α-syn under the tyrosine hydroxylase promoter and non-transgenic littermates to MnCl₂-enriched (1%) or control food, starting at the age of 4 months. Locomotor activity was increased by Mn without significant effect of the transgenes. Mice were sacrificed at the age of 7 or 20 months. Striatal Mn was significantly increased about three-fold in those exposed to MnCl₂. The number of tyrosine hydroxylase positive substantia nigra compacta neurons was significantly reduced in 20 months old mice (-10%), but Mn or transgenes were ineffective (three-way ANOVA with the factors gene, Mn and age). In 7 months old mice, striatal homovanillic acid (HVA)/dopamine (DA) ratios and aspartate levels were significantly increased in control mice with human α-syn as compared to non-transgenic controls (+17 and +11%, respectively); after Mn exposure both parameters were significantly reduced (-16 and -13%, respectively) in human α-syn mice, but unchanged in non-transgenic animals and mice with mutated α-syn (two-way ANOVA with factors gene and Mn). None of the parameters were changed in the 20 months old mice. Single HVA/DA ratios and single aspartate levels significantly correlated across all treatment groups suggesting a causal relationship between the rate of striatal DA metabolism and aspartate release. In conclusion, under our experimental conditions, Mn and human α-syn, wild-type and doubly mutated, did not interact to induce PD-like neurodegenerative changes. However, Mn significantly and selectively interacted with human wild-type α-syn on indices of striatal DA neurotransmission, the neurotransmitter most relevant to PD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Chlorides / toxicity*
  • Chromatography, High Pressure Liquid
  • Corpus Striatum / drug effects
  • Corpus Striatum / metabolism*
  • Corpus Striatum / pathology
  • Dopamine / metabolism*
  • Humans
  • Immunohistochemistry
  • Manganese Compounds
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Motor Activity
  • Nerve Degeneration / genetics
  • Nerve Degeneration / metabolism
  • Nerve Degeneration / pathology
  • Parkinsonian Disorders / genetics
  • Parkinsonian Disorders / metabolism
  • Parkinsonian Disorders / pathology
  • Synaptic Transmission / drug effects
  • alpha-Synuclein / genetics*
  • alpha-Synuclein / metabolism

Substances

  • Chlorides
  • Manganese Compounds
  • alpha-Synuclein
  • manganese chloride
  • Dopamine