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Effect of BCL-2 down-regulation on cellular life span
Tsutomu Kumazaki1, Masao Sasaki, Masahiko Nishiyama
1Department of Biochemistry and Biophysics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan. kumazaki@hiroshima-u.ac.jp
Abstract:
Reactive oxygen species (ROS) are toxic for cells. BCL-2 is known as the anti-death protein and acts as an antioxidant. When the BCL-2 level of normal fibroblasts was suppressed by antisense bcl-2 oligodeoxynucleotide or antisense bcl-2 RNA expression, the life span of the culture was shortened by about 11 population doublings (approx. 15% of the total life span) in comparison to the control culture. Since about twice as many cell deaths were observed in the antisense culture than in the vector culture, the life span shortening was probably caused by ROS-induced death. Acceleration of telomere shortening was not evident in the antisense culture. Other BCL-2 family proteins showed no significant change in expression. Cell death was suppressed by N-acetyl-L-cysteine, an antioxidant, suggesting that ROS were the major cause of cell death. In conclusion, reduction of BCL-2 makes cells more sensitive to death induced by ROS and leads to shortening of the culture's life span.
Insights
Reducing the anti-death protein BCL-2 increases cell sensitivity to toxic reactive oxygen species (ROS). This leads to increased cell death and a shortened cellular lifespan in normal fibroblasts.
Area of Science:
- Cell Biology
- Biochemistry
- Aging Research
Background:
- Reactive oxygen species (ROS) are cytotoxic byproducts of cellular metabolism.
- BCL-2 is a key anti-apoptotic protein with known antioxidant properties.
- Cellular senescence limits the replicative lifespan of normal cells.
Purpose of the Study:
- To investigate the role of BCL-2 in cellular lifespan regulation.
- To determine if BCL-2 deficiency sensitizes cells to ROS-induced death.
- To elucidate the contribution of ROS to lifespan shortening upon BCL-2 suppression.
Main Methods:
- Suppression of BCL-2 expression in normal fibroblasts using antisense oligodeoxynucleotides and RNA.
- Quantification of cell population doublings and cell death rates.
- Assessment of telomere shortening and expression of other BCL-2 family proteins.
- Treatment with the antioxidant N-acetyl-L-cysteine to evaluate ROS involvement.
Main Results:
- BCL-2 suppression shortened fibroblast culture lifespan by approximately 15%.
- Cell death rates doubled in BCL-2 suppressed cultures compared to controls.
- Antioxidant treatment with N-acetyl-L-cysteine rescued cells from death, confirming ROS as the cause.
- No acceleration of telomere shortening or significant changes in other BCL-2 family proteins were observed.
Conclusions:
- Reduced BCL-2 levels increase cellular susceptibility to ROS-induced apoptosis.
- ROS-mediated cell death is a significant factor in the shortened lifespan of BCL-2 deficient fibroblasts.
- BCL-2 plays a critical role in protecting cells against oxidative stress and maintaining cellular longevity.