Combined effect of dopamine and MPP+ on membrane permeability in mitochondria and cell viability in PC12 cells
Chung Soo Lee1, Eun Hyang Song, Se Young Park
1Department of Pharmacology, College of Medicine, Chung-Ang University, 156-756, Seoul, South Korea. leecs@cau.ac.kr
Abstract:
The present study examined the combined effect of dopamine and 1-methyl-4-phenylpyridinium (MPP(+)) on the membrane permeability in isolated brain mitochondria and on cell viability in PC12 cells. MPP(+) increased effect of dopamine against the swelling, membrane potential, and Ca(2+) transport in isolated mitochondria, which was not inhibited by the addition of antioxidant enzymes (SOD and catalase). Dopamine or MPP(+) caused the decrease in transmembrane potential, increase in reactive oxygen species, depletion of GSH, and cell death in PC12 cells. Antioxidant enzymes reduced each effect of dopamine and MPP(+) against PC12 cells. Co-addition of dopamine and MPP(+) caused the decrease in the transmembrane potential and increase in the formation of reactive oxygen species in PC12 cells, in which they showed an additive effect. Dopamine plus MPP(+)-induced the depletion of GSH and cell death in PC12 cells were not decreased by the addition of antioxidant enzymes, rutin, diethylstilbestrol, and ascorbate. Melanin caused a cell viability loss in PC12 cells. The N-acetylcysteine, N-phenylthiourea, and 5-hydroxyindole decreased the cell death and the formation of dopamine quinone and melanin induced by co-addition of dopamine and MPP(+), whereas deprenyl and chlorgyline did not show an inhibitory effect. The results suggest that co-addition of dopamine and MPP(+) shows an enhancing effect on the change in mitochondrial membrane permeability and cell death, which may be accomplished by toxic quinone and melanin derived from the MPP(+)-stimulated dopamine oxidation.
Insights
The combined effect of dopamine and MPP(+) enhances mitochondrial damage and cell death in PC12 cells, primarily through toxic quinone and melanin formation.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Dopamine is a key neurotransmitter implicated in neurodegenerative diseases.
- 1-methyl-4-phenylpyridinium (MPP(+)) is a neurotoxin used to model Parkinson's disease.
- The combined toxicity of dopamine and MPP(+) on cellular mechanisms is not fully understood.
Purpose of the Study:
- To investigate the synergistic effects of dopamine and MPP(+) on mitochondrial function and PC12 cell viability.
- To elucidate the mechanisms underlying MPP(+)-enhanced dopamine toxicity.
- To identify potential protective agents against combined dopamine and MPP(+) neurotoxicity.
Main Methods:
- Isolated brain mitochondria and PC12 cells were used as experimental models.
- Assays included mitochondrial swelling, membrane potential, Ca(2+) transport, reactive oxygen species (ROS) production, glutathione (GSH) levels, and cell viability.
- Effects of antioxidant enzymes, specific inhibitors, and melanin were evaluated.
Main Results:
- MPP(+) potentiated dopamine-induced mitochondrial dysfunction (swelling, membrane potential loss, altered Ca(2+) transport).
- Combined dopamine and MPP(+) treatment led to increased ROS, GSH depletion, and cell death in PC12 cells, with an additive effect on ROS and cell death.
- Melanin formation was observed, contributing to cell viability loss; N-acetylcysteine and related compounds offered protection against toxic intermediates.
Conclusions:
- Co-administration of dopamine and MPP(+) exhibits an enhanced toxicity profile, impacting mitochondrial integrity and cell survival.
- MPP(+)-stimulated dopamine oxidation generates toxic quinone and melanin species, mediating the observed cellular damage.
- Targeting dopamine oxidation products may offer a therapeutic strategy against combined neurotoxicity.
