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The toxic responses induced by okadaic acid involve processing of multiple caspase isoforms
G P Rossini1, N Sgarbi, C Malaguti
1Dipartimento di Scienze Biomediche, Sezione di Chimica Biologica, Università di Modena e Reggio Emilia, Via Campi 287, 41100 Modena, Italy. rossini.gianpaolo@unimo.it
Abstract:
The recognized role of caspases as executioners of apoptosis, led us to investigate their involvement in death responses induced by okadaic acid (OA) in HeLa S(3) and MCF-7 cells. A one-day treatment with OA induced accumulation of the 85kDa poly(ADP-ribose) polymerase (PARP) fragment in cell lysates but the response was prevented if cells were treated with OA in the presence of the caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK. The HeLa S(3) and MCF-7 cells were found to contain measurable levels of the intact caspase-2, -7, -8 and -9 zymogens, whereas caspase-3 was found only in HeLa cells. After one day of OA treatment, pro-caspase-2, -3, -7 and -9 isoforms were found processed in HeLa cells, whereas only pro-caspase-2 was processed in MCF-7 cells. Pro-caspase-8, in turn, was mostly unprocessed in both cell lines. The possible interference of caspase inhibitors on cell death was also evaluated, and we found that both Z-VAD-FMK and Z-DEVD-FMK could contribute different extents of protection of MCF-7 and HeLa cells from toxic effects caused by OA. We concluded that OA triggers multiple pathways of caspase processing, contributing to death responses triggered by OA in HeLa S(3) and MCF-7 cells.
Insights
Okadaic acid (OA) activates multiple caspase pathways, leading to cell death in HeLa and MCF-7 cells. Caspase inhibitors partially protected cells, indicating their role in OA-induced apoptosis.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Caspases are key executioners of apoptosis.
- Okadaic acid (OA) is a known inducer of cell death.
Purpose of the Study:
- Investigate caspase involvement in OA-induced cell death in HeLa S(3) and MCF-7 cells.
- Determine the specific caspases processed by OA treatment.
Main Methods:
- Treatment of HeLa S(3) and MCF-7 cells with OA.
- Analysis of poly(ADP-ribose) polymerase (PARP) cleavage.
- Assessment of caspase zymogen and processed fragment levels using Western blotting.
- Evaluation of caspase inhibitors (Z-VAD-FMK, Z-DEVD-FMK) on cell viability.
Main Results:
- OA treatment induced PARP cleavage, indicative of apoptosis, which was blocked by caspase inhibitors.
- HeLa cells processed caspases-2, -3, -7, and -9, while MCF-7 cells processed only caspase-2 after OA exposure.
- Caspase-8 remained largely unprocessed in both cell lines.
- Caspase inhibitors provided partial protection against OA-induced toxicity.
Conclusions:
- Okadaic acid triggers diverse caspase processing pathways contributing to cell death.
- Differential caspase activation occurs in HeLa and MCF-7 cells in response to OA.
- Caspase activity is critical for mediating OA-induced apoptosis in these cell lines.