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Developmental changes in antioxidant enzymes and oxidative damage in kidneys, liver and brain of bcl-2 knockout mice
1Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Israel. ayala@post.tau.ac.il
Abstract:
While programmed cell death is induced by a variety of internal and external stimuli, including reactive oxygen species, the anti-apoptotic protein Bcl-2 is involved in opposing cell death and affects the antioxidant status of cells. Since the exact mechanism of its action is uncertain, in this study we examined the role of Bcl-2 using a loss of function model, Bcl-2 knockout mice. The consequence of Bcl-2 knockout was assessed in kidneys, liver and brain, using protein carbonyls and cellular levels of antioxidant enzymes as markers of oxidative stress. Kidney extracts from 8 days-old Bcl-2-knockout mice had 59% higher content of protein carbonyls relative to the wild type, but similar levels of oxidized proteins at the age of 30 days. By marked contrast, in liver and brain, levels of protein carbonyls were similar at 8 days but by 30 days the liver of knockout animals (and brains, as we have shown previously) show 36% higher protein carbonyls. Measures of glutathione reductase (GRX), glutathione transferase (GST) and catalase revealed significantly higher levels in kidneys of 8 days old Bcl-2-knockout mice compared to wild type. By 30 days activities of glutathione-related enzymes and catalase increased and abolished the differences between the knockout and wild type. At 8 days, in liver there were no significant differences in activities of all enzymes between the mice, however by 30 days, the specific activity of GRX was significantly higher in Bcl-2-knockout mice, relative to controls. From day 8 to day 30 there was an increase in liver catalase activity that resulted in significantly higher levels in Bcl-2-knockout animals. Catalase activity in brains of Bcl-2-knockout, 8 days old mice was significantly higher compared to the wild type, and significantly lowers at 30 days. Taken together our findings indicate that Bcl-2 knockout results in significant perturbations of oxidative metabolism and antioxidant status of in kidney, liver and brain. Such changes are tissue specific with respect to age, magnitude and type of enzyme affected.
Insights
Bcl-2 knockout mice show altered oxidative stress markers and antioxidant enzyme activity in kidneys, liver, and brain. These changes are tissue-specific and age-dependent, revealing Bcl-2's role in regulating cellular antioxidant status.
Area of Science:
- Cell Biology
- Biochemistry
- Physiology
Background:
- Programmed cell death is influenced by various stimuli, including reactive oxygen species.
- The anti-apoptotic protein Bcl-2 opposes cell death and impacts cellular antioxidant status.
- The precise mechanism of Bcl-2's action on oxidative stress remains unclear.
Purpose of the Study:
- To investigate the role of Bcl-2 in regulating oxidative stress and antioxidant defense mechanisms.
- To analyze the consequences of Bcl-2 deficiency in a loss-of-function model (Bcl-2 knockout mice).
- To assess tissue-specific and age-dependent effects of Bcl-2 knockout on oxidative stress markers and antioxidant enzyme activity.
Main Methods:
- Utilized Bcl-2 knockout mice as a loss-of-function model.
- Assessed protein carbonyl levels as a marker of protein oxidation (oxidative stress).
- Measured the cellular levels and activities of key antioxidant enzymes, including glutathione reductase (GRX), glutathione transferase (GST), and catalase.
Main Results:
- Kidneys of 8-day-old Bcl-2 knockout mice exhibited significantly higher protein carbonyls (59%) compared to wild-type mice.
- By 30 days of age, liver and brain tissues of knockout mice showed increased protein carbonyl levels (36% in liver).
- Antioxidant enzyme activities (GRX, GST, catalase) were elevated in the kidneys of young knockout mice, normalizing by 30 days.
- Liver and brain antioxidant enzyme activities showed distinct age-dependent changes in knockout mice, with some enzymes significantly upregulated at 30 days.
Conclusions:
- Bcl-2 knockout leads to significant perturbations in oxidative metabolism and antioxidant status across kidney, liver, and brain tissues.
- The observed changes in oxidative stress markers and antioxidant enzyme activities are highly specific to the tissue type and the age of the animals.
- These findings highlight the critical role of Bcl-2 in maintaining cellular redox homeostasis and protecting against oxidative damage in a tissue- and age-dependent manner.