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Inhibition of protein kinase C protects against paraoxon-mediated neuronal cell death
Feng Tian1, Xuan Wu, Hongan Pan
1Department of Neurology and Program in Neuroscience, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Abstract:
Paraoxon, the active metabolite of parathion, is an acetylcholinesterases (AChE) inhibitor that kills cultured cerebellar granule cell neurons via an apoptotic mechanism. Protein kinase C is an enzyme with diverse functions but its role in paraoxon-induced cell death is unknown. We show that a neurotoxic concentration of paraoxon increases PKC phosphorylation. We tested whether PKC is involved in paraoxon-induced neuronal cell death by using the PKC activator, phorbol 12-myristate 13-acetate (TPA). TPA increases PKC activity and enhances the neurotoxic effect of paraoxon by 28%. In sharp contrast, addition of the PKC inhibitor Ro-31-8220 protects more than 30% neurons that would otherwise die from paraoxon-induced neuronal cell death in either a pretreatment or post-treatment paradigm and markedly reduces phospho-PKC pan levels. We also show that the pretreatment of Ro-31-8220 blocks paraoxon-induced caspase-3 activity completely. These results suggest that activation of protein kinase C is required for paraoxon neurotoxicity.
Insights
Paraoxon, an acetylcholinesterase inhibitor, causes neuron death. Protein kinase C (PKC) activation is essential for this neurotoxicity, as inhibiting PKC protects neurons from paraoxon-induced apoptosis.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Paraoxon, the active metabolite of parathion, is a known acetylcholinesterase (AChE) inhibitor.
- Paraoxon induces apoptosis in cultured cerebellar granule cell neurons.
- The role of Protein Kinase C (PKC) in paraoxon-induced neurotoxicity remains uncharacterized.
Purpose of the Study:
- To investigate the involvement of Protein Kinase C (PKC) in paraoxon-induced neuronal cell death.
- To determine if modulating PKC activity affects paraoxon neurotoxicity.
Main Methods:
- Treatment of cultured cerebellar granule cell neurons with paraoxon.
- Utilizing a PKC activator, phorbol 12-myristate 13-acetate (TPA), to enhance PKC activity.
- Employing a PKC inhibitor, Ro-31-8220, to block PKC activity.
- Assessing neuronal viability and apoptosis markers, including caspase-3 activity and phospho-PKC levels.
Main Results:
- Paraoxon exposure increased PKC phosphorylation.
- The PKC activator TPA enhanced paraoxon's neurotoxic effects by 28%.
- The PKC inhibitor Ro-31-8220 protected over 30% of neurons from paraoxon-induced death and reduced phospho-PKC levels.
- Ro-31-8220 pretreatment completely inhibited paraoxon-induced caspase-3 activity.
Conclusions:
- Activation of Protein Kinase C (PKC) is a critical requirement for paraoxon-induced neurotoxicity.
- Targeting PKC may offer a therapeutic strategy against paraoxon poisoning.
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