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Modeling Neuronal Death and Degeneration in Mouse Primary Cerebellar Granule Neurons
Published on: November 6, 2017
Trimethyltin initially activates the caspase 8/caspase 3 pathway for damaging the primary cultured cortical neurons
Nobuyuki Kuramoto1, Keiichi Seko, Chie Sugiyama
1Department of Pharmacology, Setsunan University Faculty of Pharmaceutical Sciences, Hirakata, Osaka, Japan.
Abstract:
The organotin trimethyltin (TMT) is well known to cause neuronal damage in the central nervous system. To elucidate the mechanisms underlying the toxicity of TMT toward neurons, we prepared primary cultures of neurons from the neocortex of mouse embryos. A continuous exposure to TMT produced a decrease in cell viability as well as an increase in the number of cells with nuclear condensation/shrinkage at the exposure time window up to 24 hr. In addition to the events at the early time window, lactate dehydrogenase released was significantly elevated at the later exposure time from 36 to 48 hr. With a 3-hr exposure to TMT, a significant increase was observed in the activity of caspase 8, but not in that of caspase 9. TMT exposure produced no elevation in the level of cytochrome c released from mitochondria until 12 hr of exposure, with a significant facilitation of cytochrome c release at the exposure times of 16 and 24 hr. After the activation of caspase 8 by TMT exposure, caspase 3 activation and nuclear translocation of caspase-activated DNase were caused by exposure for 6 hr or longer. However, nuclear DNase II was elevated at the later time window of exposure. A caspase inhibitor completely prevented TMT from damaging the cells in any time window. Taken together, our data are the first demonstration that TMT toxicity is initially caused by activation of the caspase 8/caspase 3 pathway for nuclear translocation of DNases in cortical neurons in primary culture.
Insights
Trimethyltin (TMT) causes neuronal damage via the caspase 8/caspase 3 pathway. This pathway leads to DNase activation and nuclear translocation, ultimately damaging cortical neurons.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Organotin compounds, specifically trimethyltin (TMT), are known neurotoxicants.
- Understanding the precise mechanisms of TMT-induced neuronal damage is crucial for developing protective strategies.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying trimethyltin (TMT) toxicity in primary cortical neurons.
- To identify the specific apoptotic pathways activated by TMT exposure.
Main Methods:
- Primary neuronal cultures were established from mouse embryonic neocortex.
- Cells were exposed to TMT continuously, with assessments of viability, nuclear morphology, and enzyme activities at various time points.
- Caspase activity, cytochrome c release, and DNase levels were measured.
- The effect of a caspase inhibitor on TMT-induced damage was evaluated.
Main Results:
- TMT exposure decreased neuronal viability and induced nuclear condensation within 24 hours.
- Lactate dehydrogenase release increased significantly between 36 and 48 hours of exposure.
- TMT activated caspase 8 within 3 hours, followed by caspase 3 activation and caspase-activated DNase nuclear translocation by 6 hours.
- Cytochrome c release was elevated after 16-24 hours, while nuclear DNase II increased later.
- A caspase inhibitor completely blocked TMT-induced neuronal damage.
Conclusions:
- TMT neurotoxicity in primary cortical neurons is initiated by the activation of the caspase 8/caspase 3 pathway.
- This pathway mediates the nuclear translocation of DNases, leading to cell death.
- The findings provide the first demonstration of this specific mechanism in TMT-induced neuronal injury.
