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Pan-caspase inhibitor zVAD enhances cell death in RAW246.7 macrophages
1Department of Immunology, Scripps Research Institute, La Jolla, California 92037, USA.
Abstract:
Even though the pan-caspase inhibitor zVAD has been widely used as an anti-apoptotic agent, inefficient prevention or even enhancement of cell death has been reported in certain cells. To further investigate its effects on cell death, three different cell types were exposed to various apoptotic stimuli in the presence or absence of zVAD. In Jurkat cells, zVAD protected against cell death induced by tumor necrosis factor (TNF), sodium nitroprusside (SNP) and etoposide, whereas in L929 cells cell death was increased. In RAW246.7 macrophages, zVAD showed similar effects as in L929 cells. However, unlike L929 cells, in which the cell death by TNF is known to be necrosis, RAW246.7 cells manifested features of apoptosis such as chromatin condensation and nuclear fragmentation. Induction of cell death by zVAD in lipopolysaccharide (LPS)-activated RAW246.7 cells also showed the same features as those observed in SNP- and etoposide-treated cells. Initiation of an apoptotic process by zVAD not only disputes the sole role of caspases in apoptosis but also suggests an anti-apoptotic function of certain caspase(s). Death of LPS-activated macrophages may be controlled by an anti-apoptotic caspase.
Insights
The pan-caspase inhibitor zVAD, often used to block apoptosis, paradoxically enhanced cell death in certain cell types. This suggests caspases may have anti-apoptotic roles, challenging their sole function in programmed cell death.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Pan-caspase inhibitors like zVAD are widely used to study apoptosis.
- However, zVAD has shown paradoxical effects, including enhancing cell death in some contexts.
- The precise mechanisms and cell-type specific responses to zVAD remain incompletely understood.
Purpose of the Study:
- To investigate the differential effects of zVAD on cell death across various cell types.
- To explore the role of caspases in apoptosis and potential anti-apoptotic functions.
- To elucidate the mechanisms of zVAD-induced cell death in macrophages.
Main Methods:
- Exposure of Jurkat cells, L929 cells, and RAW246.7 macrophages to apoptotic stimuli (TNF, SNP, etoposide, LPS).
- Treatment with the pan-caspase inhibitor zVAD in the presence and absence of stimuli.
- Morphological analysis of cell death, including chromatin condensation and nuclear fragmentation.
Main Results:
- zVAD protected Jurkat cells against TNF-, SNP-, and etoposide-induced death.
- zVAD increased cell death in L929 cells and RAW246.7 macrophages.
- In LPS-activated RAW246.7 macrophages, zVAD induced apoptosis-like features, distinct from necrosis observed in L929 cells.
Conclusions:
- The findings challenge the exclusive pro-apoptotic role of caspases, suggesting potential anti-apoptotic functions for certain caspases.
- zVAD can initiate apoptotic processes, indicating a complex regulatory role of caspases in cell death.
- The death of LPS-activated macrophages may be regulated by an anti-apoptotic caspase, highlighting cell-type specific caspase functions.