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Caspase-dependent and -independent events in apoptosis induced by hydrogen peroxide
Abstract:
To define the role of caspase-3 in H2O2-induced apoptosis, we introduced caspase-3 cDNA into MCF-7 breast carcinoma cells that otherwise lack caspase-3 expression. H2O2 treatment induced DNA fragmentation and nuclear condensation in the caspase-3-expressing cells, but not in the caspase-3-deficient cells. This indicated that caspase-3 is essential for nuclear events. However, H2O2 induced an externalization of membrane phosphatidylserine (PS) and cell death regardless of caspase-3 expression. These events were not suppressed by Ac-DEVD-CHO and Z-VAD-fmk, which inhibit DEVD-specific caspases and a broad spectrum of caspases, respectively. In Jurkat T cells, these inhibitors abolished H2O2-induced PS relocalization, but not cell death. Therefore, caspases appear to be dispensable for lethality by H2O2, but required for PS redistribution in a cell-type-specific manner.
Insights
Caspase-3 is essential for nuclear events in hydrogen peroxide (H2O2)-induced apoptosis. However, caspases are not required for cell death itself, showing cell-type-specific roles in apoptosis signaling.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Apoptosis, or programmed cell death, is a crucial biological process.
- Hydrogen peroxide (H2O2) is a reactive oxygen species that can induce apoptosis.
- Caspases are key proteases involved in apoptosis execution.
Purpose of the Study:
- To elucidate the specific role of caspase-3 in H2O2-induced apoptosis.
- To investigate whether caspase-3 is essential for all apoptotic events or specific pathways.
Main Methods:
- Introducing caspase-3 cDNA into MCF-7 breast carcinoma cells lacking endogenous caspase-3.
- Treating cells with H2O2 and assessing DNA fragmentation, nuclear condensation, and phosphatidylserine (PS) externalization.
- Utilizing caspase inhibitors (Ac-DEVD-CHO and Z-VAD-fmk) to block caspase activity.
Main Results:
- Caspase-3 expression was essential for H2O2-induced DNA fragmentation and nuclear condensation.
- H2O2-induced externalization of membrane phosphatidylserine (PS) and cell death occurred independently of caspase-3.
- Caspase inhibitors blocked H2O2-induced PS relocalization in Jurkat T cells but not overall cell death, indicating cell-type specificity.
Conclusions:
- Caspase-3 is indispensable for the nuclear morphological changes during H2O2-induced apoptosis.
- Caspases are not required for H2O2-induced cell lethality.
- The requirement for caspases in phosphatidylserine redistribution is cell-type specific in response to H2O2.