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Early induction of calpains in rotenone-mediated neuronal apoptosis
Minghui Jessica Chen1, Yann Wan Yap, Meng Shyan Choy
1Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, 8 Medical Drive, Singapore 117597, Republic of Singapore.
Abstract:
Rotenone is an inhibitor of mitochondrial complex I that produces a model of Parkinson's disease (PD), where neurons undergo apoptosis by caspase-dependent and/or caspase-independent pathways. Inhibition of calpains has recently been shown to attenuate neuronal apoptosis. This study aims to establish for the first time, the time-point of calpain activation with respect to the caspase activation and the possibility of cell cycle re-entry in rotenone-mediated cell death. Immunoblot results revealed calpain activation occurred at 5, 10h prior to caspase-3 activation (at 15 h), suggesting calpain activation was an earlier cellular event compared to caspase activation in the rotenone-mediated apoptosis. In addition, an upregulation of phospho-p53 was observed at 21 h. However, no expression or upregulation of cell cycle regulatory proteins including cdc25a, cyclin-D1 and cyclin-D3 were observed, strongly suggesting that cell cycle re-entry did not occur. These findings provide new insights into the differential patterns of calpain and caspase activation that result from rotenone poisoning and which may be relevant to the therapeutic management of PD.
Insights
Calpain activation precedes caspase activation in rotenone-induced Parkinson
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Rotenone models Parkinson's disease (PD) by inducing neuronal apoptosis via caspase pathways.
- Calpain inhibition can reduce neuronal apoptosis.
- The temporal relationship between calpain activation, caspase activation, and cell cycle re-entry in rotenone toxicity is unknown.
Purpose of the Study:
- To determine the timing of calpain activation relative to caspase activation in rotenone-induced cell death.
- To investigate whether cell cycle re-entry occurs during rotenone-mediated neuronal apoptosis.
Main Methods:
- Utilized immunoblotting to detect protein activation and expression.
- Analyzed time points of calpain, caspase-3, phospho-p53, and cell cycle regulatory proteins (cdc25a, cyclin-D1, cyclin-D3) following rotenone exposure.
Main Results:
- Calpain activation was observed 5-10 hours before caspase-3 activation (at 15 hours).
- Upregulation of phospho-p53 was detected at 21 hours.
- No expression or upregulation of cell cycle proteins (cdc25a, cyclin-D1, cyclin-D3) was observed, indicating no cell cycle re-entry.
Conclusions:
- Calpain activation is an early event preceding caspase activation in rotenone-induced apoptosis.
- Rotenone-mediated neuronal death does not involve cell cycle re-entry.
- These findings offer insights into PD pathogenesis and potential therapeutic strategies targeting calpain and caspase pathways.
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