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Sensitivity of human pancreatic islets to peroxynitrite-induced cell dysfunction and death
C A Delaney1, B Tyrberg, L Bouwens
1Department of Medical Cell Biology, Uppsala University, Sweden. Carol Delaney@medcellbiol.uu.se
Abstract:
Nitric oxide and peroxynitrite (generated by the reaction of nitric oxide with the superoxide anion) may both be mediators of beta-cell damage in early insulin-dependent diabetes mellitus. We observed that acute exposure of primary cultured human pancreatic islets to peroxynitrite results in a significant decrease in glucose oxidation and islet retrieval. DNA strand breaks in single human and rat islet cells are detectable after acute peroxynitrite exposure, followed by a decrease in islet cell survival after 1 h and 24 h. Cell death appeared to occur via a toxic cell death mechanism (necrosis) rather than apoptosis, as suggested by vital staining and ultrastructural evidence of early membrane and organelle degradation, mitochondrial swelling and loss of matrix. This study demonstrates for the first time that cultured human pancreatic islets are susceptible to the noxious effects of peroxynitrite.
Insights
Peroxynitrite, a reactive nitrogen species, causes significant damage to human pancreatic islet cells. This finding highlights its potential role in beta-cell dysfunction and insulin-dependent diabetes mellitus.
Area of Science:
- Biochemistry
- Cell Biology
- Endocrinology
Background:
- Nitric oxide (NO) and peroxynitrite are implicated as mediators of beta-cell damage in type 1 diabetes.
- Understanding the specific effects of peroxynitrite on human pancreatic islets is crucial for diabetes research.
Purpose of the Study:
- To investigate the susceptibility of primary cultured human pancreatic islets to peroxynitrite exposure.
- To characterize the cellular mechanisms of peroxynitrite-induced islet cell damage.
Main Methods:
- Primary human and rat pancreatic islets were acutely exposed to peroxynitrite.
- Glucose oxidation, islet retrieval, DNA strand breaks, and cell survival were assessed.
- Cell death mechanisms (necrosis vs. apoptosis) were evaluated using vital staining and ultrastructural analysis.
Main Results:
- Peroxynitrite exposure significantly reduced glucose oxidation and islet retrieval in human islets.
- DNA strand breaks were detected in islet cells following peroxynitrite exposure.
- Cell death occurred via necrosis, characterized by membrane degradation and mitochondrial damage, rather than apoptosis.
Conclusions:
- Cultured human pancreatic islets are susceptible to the damaging effects of peroxynitrite.
- Peroxynitrite-induced beta-cell damage may contribute to the pathogenesis of early insulin-dependent diabetes mellitus.
- Necrosis is the primary mode of cell death induced by peroxynitrite in pancreatic islets.