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Effect of apoptosis-related compounds on Ca2+ transport system in isolated rat liver nuclei
1Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka City, Japan.
Abstract:
The effect of various inhibitors of DNA topoisomerase II, which has been shown to induce apoptotic cell death, on Ca2+ transport in isolated rat liver nuclei was investigated. Ca2+ uptake and release were determined with a Ca2+ electrode. The presence of aurintricarboxylic acid (ATA; 10(-6) to 10(-4) M), etoposide (10(-4) M), genistein (10(-5) and 10(-4) M) or amsacrine (10(-4) M) in the reaction mixture caused a significant increase in Ca2+ release from the nuclei. Also, these compounds (10(-4) M) significantly inhibited Ca2+ uptake by the nuclei. However, the presence of ATA (10(-5) and 10(-4) M) in the enzyme reaction mixture did not significantly inhibit Ca2+-ATPase activity, which is involved in the nuclear Ca2+ uptake, in the liver nuclei, while etoposide (10(-4) M), genistein (10(-4) M) and amsacrine (10(-4) M) appreciably decreased the enzyme activity. Meanwhile, addition of Ca2+ clearly activated DNA fragmentation in the liver nuclei. The Ca2+ activated DNA fragmentation was significantly prevented by the presence of etoposide, genistein and amsacrine with the concentrations of 10(-5) and 10(-4) M in the reaction mixture, although ATA (10(-5) and 10(-4) M) had no effect. The present study demonstrates that some apoptosis inducible compounds used can influence on Ca2+ transport system in isolated rat liver nuclei, suggesting a decrease of nuclear Ca2+ level involved in nuclear functions.
Insights
Certain DNA topoisomerase II inhibitors that induce apoptosis also disrupt calcium (Ca2+) transport in rat liver nuclei. These compounds increase Ca2+ release and inhibit Ca2+ uptake, affecting nuclear Ca2+ levels and DNA fragmentation.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Pharmacology
Background:
- DNA topoisomerase II inhibitors are known to induce apoptosis.
- Nuclear calcium (Ca2+) plays a critical role in regulating cellular processes, including DNA fragmentation.
Purpose of the Study:
- To investigate the impact of apoptosis-inducing DNA topoisomerase II inhibitors on Ca2+ transport in isolated rat liver nuclei.
- To explore the relationship between these inhibitors, nuclear Ca2+ homeostasis, and DNA fragmentation.
Main Methods:
- Isolated rat liver nuclei were used to study Ca2+ uptake and release.
- A Ca2+ electrode was employed to quantify Ca2+ transport.
- Ca2+-ATPase activity and Ca2+-activated DNA fragmentation were assessed in the presence of various inhibitors.
Main Results:
- Aurintricarboxylic acid (ATA), etoposide, genistein, and amsacrine significantly increased Ca2+ release and inhibited Ca2+ uptake by liver nuclei.
- Etoposide, genistein, and amsacrine inhibited Ca2+-ATPase activity, a key enzyme in nuclear Ca2+ uptake.
- While Ca2+ addition activated DNA fragmentation, etoposide, genistein, and amsacrine significantly prevented this process.
Conclusions:
- Apoptosis-inducing DNA topoisomerase II inhibitors can significantly alter Ca2+ transport mechanisms within rat liver nuclei.
- These alterations in nuclear Ca2+ transport may contribute to the apoptotic effects observed.
- The findings suggest a potential role for modulating nuclear Ca2+ levels in the mechanism of action of these compounds.