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Intracellular targets for nitric oxide toxicity to pancreatic beta-cells
1Department of Medical Cell Biology, Uppsala University, Sweden.
Abstract:
The radical nitric oxide (NO) may be a mediator of pancreatic beta-cell damage in early insulin-dependent diabetes mellitus (IDDM). Under the stimulus of cytokines, invading macrophages and the beta-cell themselves may produce large amounts of NO, leading to beta-cell dysfunction and death. It still remains to be determined which are the intracellular targets for NO-induced damage. Available data from rat islets indicate that the radical inactivates the mitochondrial enzyme aconitase, impairing substrate oxidation and ATP production. Ionic channels and complexes I and II of the mitochondrial electron transport chain are two other possible targets for NO effects which may impair insulin secretion. NO also leads to nuclear DNA damage in both rat and human pancreatic beta-cells, as evaluated by the 'comet assay'. The effects of NO at the DNA level are complex, and involve formation of N-nitrosoamines, deamination of purines and pyrimidines, or damage induced by peroxynitrite. Besides inducing over DNA damage. NO may also inactivate DNA repair/replication enzymes. The outcome of NO-induced beta-cell DNA damage can be cell death by apoptosis or, in some cases, necrosis. Upon cell damage beta-cells trigger cell repair mechanisms. This seems also to be the case following NO exposure, and insulin-producing cells are able to regain their function following treatment with non-lethal concentrations of NO. A better understanding of the mechanisms involved in NO-induced beta-cell damage and repair may be instrumental in developing new strategies for IDDM prevention.
Insights
Nitric oxide (NO) causes pancreatic beta-cell damage in diabetes by affecting mitochondria and DNA. However, beta-cells can repair NO-induced damage, offering potential therapeutic targets for IDDM prevention.
Area of Science:
- Endocrinology
- Immunology
- Molecular Biology
Background:
- Pancreatic beta-cell damage is implicated in insulin-dependent diabetes mellitus (IDDM).
- Nitric oxide (NO), a radical molecule, is a potential mediator of this beta-cell damage.
- Cytokines stimulate macrophages and beta-cells to produce NO, leading to dysfunction and death.
Purpose of the Study:
- To investigate the intracellular targets of nitric oxide (NO)-induced damage in pancreatic beta-cells.
- To elucidate the mechanisms underlying NO-mediated beta-cell injury and potential repair pathways.
- To explore therapeutic strategies for IDDM prevention based on NO-induced damage mechanisms.
Main Methods:
- Assessment of mitochondrial enzyme aconitase activity in rat islets.
- Evaluation of ionic channel and mitochondrial electron transport chain complex function.
- Analysis of nuclear DNA damage using the comet assay in rat and human beta-cells.
- Investigation of NO's effects on DNA repair/replication enzymes.
Main Results:
- NO inactivates mitochondrial aconitase, impairing ATP production and substrate oxidation.
- NO affects ionic channels and mitochondrial complexes I and II, potentially inhibiting insulin secretion.
- NO induces nuclear DNA damage through various mechanisms, including N-nitrosoamine formation and purine/pyrimidine deamination.
- NO can inactivate DNA repair/replication enzymes, leading to apoptosis or necrosis.
- Beta-cells demonstrate repair mechanisms and can regain function after exposure to non-lethal NO concentrations.
Conclusions:
- Nitric oxide (NO) plays a significant role in pancreatic beta-cell damage in IDDM through mitochondrial and DNA injury.
- Understanding NO-induced damage and repair pathways is crucial for developing novel therapeutic strategies for IDDM.
- Beta-cell resilience and repair mechanisms offer potential targets for preventing or mitigating diabetes progression.