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A dopaminergic cell line variant resistant to the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
Abstract:
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is known to cause parkinsonism by killing dopaminergic neurons; the toxic substance is a metabolite, 1-methyl-4-phenylpyridinium ion (MPP+). PC12 cells, which are dopaminergic, are killed in culture by MPTP and MPP+ but at concentrations much higher than that required to kill affected neurons in vivo. However, at low concentrations (10-100 microM), MPP+ caused an increased production of lactate by PC12 cells. MPP+-treated PC12 cells exhibited decreased mitochondrial respiration. Mitochondria from the treated cells respired normally in the presence of added succinate but not beta-hydroxybutyrate, a finding indicating that MPP+ inhibits the oxidation of some substrates selectively. MPP+ was more effective in killing the cells when glycolysis was reduced with 2-deoxyglucose or by lowering the glucose content of the culture medium. Under these conditions, MPP+ inhibited ATP synthesis and depleted cellular stores of ATP. A PC12 variant that is even more resistant to MPTP and MPP+ than are wild-type cells has been isolated. The MPTP-resistant variant is also more resistant to the lethal effects of oligomycin, antimycin A, and rotenone. This variant exhibited altered lactate production and mitochondrial respiration. It is suggested that some brain neurons that accumulate MPP+ without being killed by it may also have an energy metabolism somewhat different from that of more sensitive neurons.
Insights
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes parkinsonism by damaging dopaminergic neurons via its metabolite MPP+. MPP+ disrupts cellular energy metabolism, impacting ATP synthesis and mitochondrial respiration in PC12 cells.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin that induces parkinsonism.
- Its active metabolite, 1-methyl-4-phenylpyridinium ion (MPP+), is responsible for dopaminergic neuron death.
- PC12 cells, a dopaminergic cell line, are used to study MPTP/MPP+ toxicity.
Purpose of the Study:
- To investigate the effects of MPP+ on PC12 cell metabolism and survival.
- To elucidate the mechanism by which MPP+ affects cellular energy production.
- To characterize MPTP/MPP+-resistant PC12 cell variants.
Main Methods:
- Treatment of PC12 cells with MPP+ at various concentrations.
- Measurement of lactate production, mitochondrial respiration, and ATP synthesis.
- Isolation and characterization of MPTP/MPP+-resistant PC12 cell variants.
- Assessment of mitochondrial substrate oxidation.
Main Results:
- MPP+ increased lactate production and decreased mitochondrial respiration in PC12 cells.
- MPP+ selectively inhibited the oxidation of beta-hydroxybutyrate, but not succinate.
- MPP+ toxicity was enhanced under conditions of reduced glycolysis, leading to ATP depletion.
- A resistant variant showed altered metabolic responses to MPP+ and other mitochondrial toxins.
Conclusions:
- MPP+ impairs cellular energy metabolism by inhibiting mitochondrial substrate oxidation and ATP synthesis.
- Disruption of energy metabolism is a key mechanism in MPP+-induced neurotoxicity.
- Cellular energy metabolism differences may contribute to neuronal resistance to MPP+ toxicity.
