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Inhibitors of mitochondrial energy production prevent DNA internucleosomal fragmentation in thymocytes
1Institute of Theoretical and Experimental Biophysics, Pushchino, Moscow Region, 142292, Russia.
Abstract:
Apoptosis or programmed cell death is a gene-controlled process of cell self-destruction. One of the earliest manifestations of apoptosis, which precedes morphological changes, is a decrease of mitochondrial membrane potential. Here we show that neither inhibitors of the mitochondrial respiratory chain (rotenone and antimycin) nor an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone), agents which decrease the mitochondrial membrane potential, induce DNA internucleosomal fragmentation, but all of them markedly prevent fragmentation induced either by glucocorticoids or the Ca2+ ionophore A23187. A similar effect was also observed in the presence of a mitochondrial ATPase inhibitor (oligomycin). The inhibition of DNA internucleosomal fragmentation can be explained by the ability of inhibitors to prevent the mitochondrial permeability transition--a key event in apoptosis induction.
Insights
Mitochondrial membrane potential decrease, a hallmark of apoptosis, does not induce DNA fragmentation. Inhibitors preventing mitochondrial permeability transition block apoptosis-related DNA fragmentation, revealing a key role for this transition in programmed cell death.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Apoptosis, or programmed cell death, is a fundamental biological process crucial for development and tissue homeostasis.
- A decrease in mitochondrial membrane potential is an early indicator of apoptosis, preceding visible cellular changes.
- The precise mechanisms linking mitochondrial dysfunction to DNA fragmentation in apoptosis are still under investigation.
Purpose of the Study:
- To investigate the role of mitochondrial membrane potential and permeability transition in the induction of DNA internucleosomal fragmentation during apoptosis.
- To determine whether agents that decrease mitochondrial membrane potential can induce DNA fragmentation independently.
- To elucidate the mechanism by which apoptosis-inducing agents trigger DNA fragmentation.
Main Methods:
- Utilized inhibitors of the mitochondrial respiratory chain (rotenone, antimycin) and an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone) to manipulate mitochondrial membrane potential.
- Assessed the induction of DNA internucleosomal fragmentation using glucocorticoids and the Ca2+ ionophore A23187 as apoptosis triggers.
- Examined the effect of a mitochondrial ATPase inhibitor (oligomycin) on DNA fragmentation.
Main Results:
- Inhibitors of the mitochondrial respiratory chain and oxidative phosphorylation uncouplers did not induce DNA internucleosomal fragmentation.
- These agents significantly prevented DNA fragmentation induced by glucocorticoids and A23187.
- Oligomycin also inhibited DNA fragmentation, suggesting a role for mitochondrial ATPase activity.
Conclusions:
- A decrease in mitochondrial membrane potential alone is insufficient to trigger DNA internucleosomal fragmentation.
- Inhibitors that prevent the mitochondrial permeability transition effectively block apoptosis-induced DNA fragmentation.
- The mitochondrial permeability transition is a critical event in the induction of DNA fragmentation during programmed cell death.