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Dopamine induces proteasome inhibition in neural PC12 cell line
J N Keller1, F F Huang, E R Dimayuga
1Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY 40536-0230, USA. jnkell0@pop.uky.edu
Abstract:
The autoxidation and enzymatic catabolism of dopamine results in the generation of reactive oxygen species (ROS), which may possibly contribute to oxidative stress in multiple neurodegenerative disorders. Recent studies indicate that proteasome inhibition occurs in numerous neurodegenerative conditions, possibly as the result of oxidative stress, although the effects of dopamine on proteasome activity have not been determined. In the present study we examined the effects of dopamine on proteasome activity in the neural PC12 cell line. Application of dopamine induced a dose- and time-dependent decrease in proteasome activity, which occurred prior to cell death. Application of an antioxidant (gluthathione monoethyl ester), monoamine oxidase inhibitors (deprenyl, clogyline, paragyline), or an inhibitor of dopamine uptake (nomifensine) attenuated dopamine toxicity and dopamine-induced proteasome impairment. Application of the proteasome inhibitor lactacystin increased the toxicity of dopamine and the levels of protein oxidation following administration of dopamine. Together, these data indicate that dopamine induces proteasome inhibition that is dependent, in part, on ROS and dopamine uptake, and suggest a possible role for proteasome inhibition in dopamine toxicity.
Insights
Dopamine exposure impairs proteasome activity in neural cells, contributing to toxicity. Antioxidants and dopamine uptake inhibitors protect against this effect, suggesting a role for proteasome inhibition in neurodegenerative conditions.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Dopamine metabolism generates reactive oxygen species (ROS), implicated in neurodegenerative disorders.
- Oxidative stress may cause proteasome inhibition in neurodegeneration, but dopamine's direct effect is unknown.
Purpose of the Study:
- To investigate the impact of dopamine on proteasome activity in the PC12 neural cell line.
- To determine if dopamine-induced proteasome inhibition contributes to its toxicity.
Main Methods:
- PC12 cells were treated with dopamine, and proteasome activity was measured.
- The effects of antioxidants, monoamine oxidase inhibitors, and dopamine uptake inhibitors were assessed.
- The impact of a proteasome inhibitor (lactacystin) on dopamine toxicity was evaluated.
Main Results:
- Dopamine caused a dose- and time-dependent decrease in proteasome activity before cell death.
- Antioxidants, monoamine oxidase inhibitors, and a dopamine uptake inhibitor reduced dopamine toxicity and proteasome impairment.
- Lactacystin exacerbated dopamine toxicity and protein oxidation.
Conclusions:
- Dopamine induces proteasome inhibition, partly mediated by ROS and dopamine uptake.
- Proteasome inhibition may play a significant role in dopamine-induced neurotoxicity.