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Microtubule antagonists activate programmed cell death (apoptosis) in cultured rat hepatocytes
K Tsukidate1, K Yamamoto, J W Snyder
1Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107-6799.
Abstract:
We investigated the mechanism of lethal injury following the disruption of microtubules in cultured hepatocytes treated with vinblastine (VBL) or colchicine (COL). These agents kill hepatocytes by a process readily distinguished from two well-known pathways that lead to a loss of viability, namely, oxidative stress and inhibition of mitochondrial electron transport. Cell killing with VBL and COL was accompanied by fragmentation of DNA. Both the loss of viability and the fragmentation of DNA were prevented by the inhibition of protein synthesis within 6 hours following exposure to VBL or COL. Cell death and the fragmentation of DNA were also prevented when Ca2+ was removed from the culture medium. By contrast, the inhibition of protein kinase C prevented cell killing by VBL or COL, but did not alter the extent of DNA fragmentation. The requirements here for protein synthesis, extracellular Ca2+, and protein kinase C activity define a model of apoptosis, or programmed cell death, that seems to involve mechanisms that can be dissociated from the fragmentation of DNA.
Insights
Vinblastine and colchicine induce hepatocyte death via a novel programmed cell death pathway. This process requires protein synthesis and extracellular calcium but is independent of DNA fragmentation.
Area of Science:
- Cell Biology
- Toxicology
- Biochemistry
Background:
- Hepatocyte viability can be compromised by various cellular insults.
- Known cell death pathways include oxidative stress and mitochondrial dysfunction.
- Microtubule disruption agents like vinblastine (VBL) and colchicine (COL) induce cell death in hepatocytes.
Purpose of the Study:
- To elucidate the mechanism of lethal injury induced by microtubule disruption in cultured hepatocytes.
- To differentiate the VBL/COL-induced cell death pathway from oxidative stress and mitochondrial inhibition.
- To identify key molecular requirements for VBL/COL-mediated hepatocyte death.
Main Methods:
- Cultured hepatocytes were treated with vinblastine (VBL) or colchicine (COL).
- Assessed cell viability, DNA fragmentation, protein synthesis inhibition, extracellular calcium levels, and protein kinase C activity.
- Investigated the effects of inhibiting protein synthesis, removing extracellular Ca2+, and inhibiting protein kinase C on cell death and DNA fragmentation.
Main Results:
- VBL and COL induced hepatocyte death accompanied by DNA fragmentation.
- Both cell death and DNA fragmentation were prevented by inhibiting protein synthesis within 6 hours or by removing extracellular Ca2+.
- Inhibiting protein kinase C prevented cell killing but not DNA fragmentation, suggesting a dissociation between these events.
Conclusions:
- Microtubule-disrupting agents trigger a distinct cell death pathway in hepatocytes.
- This pathway, characterized by requirements for protein synthesis and extracellular Ca2+, aligns with a model of apoptosis.
- The findings suggest that DNA fragmentation can be dissociated from the core mechanisms of VBL/COL-induced programmed cell death.