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Nitric oxide donors decrease the function and survival of human pancreatic islets
D L Eizirik1, C A Delaney, M H Green
1Department of Medical Cell Biology, Uppsala University, Sweden. decio.eizirik@medcellbiol.uu.se
Abstract:
Nitric oxide (NO) has been proposed as a possible mediator of beta-cell damage in human IDDM. This hypothesis is based on in vitro studies with rodent pancreatic islets. In the present study we examined whether human beta-cells are affected by NO. In view of species differences in beta-cell sensitivity to damaging agents, rat islets were investigated in parallel. Isolated islets were exposed for 90 min to different concentrations of three chemically unrelated NO donors, SIN-1, GSNO or RBS. At the end of this incubation, human insulin release was mostly similar in control and NO-treated islets but, 48 h later, islet retrieval, islet DNA and insulin content, and glucose-induced insulin release were markedly lower in islets exposed to NO donors. Rat islets were already inhibited during the initial 90 min; 48 h later their loss in beta-cell function was similar to that in human islets. Nicotinamide or succinic acid monomethyl ester partially protected against SIN-1 induced islet cell loss, but not against the functional inhibition of human pancreatic islets. Exposure of human or rat islets to RBS was associated with significant DNA strand breakage, as judged by the comet assay (single cell gel electrophoresis) and by ultrastructural signs of cell damage. DNA damage was more severe in rat islet cells exposed to similar amounts of RBS. It is concluded that NO donors can damage human pancreatic islets, an effect paralleled by induction of nuclear DNA strand breaks.
Insights
Nitric oxide (NO) can damage human pancreatic beta-cells, leading to reduced insulin release and DNA damage. This finding, observed in vitro, suggests NO may play a role in diabetes pathogenesis.
Area of Science:
- Endocrinology
- Cell Biology
- Toxicology
Background:
- Nitric oxide (NO) is implicated as a potential mediator of beta-cell damage in human type 1 diabetes (T1D).
- Previous hypotheses were based on in vitro studies using rodent pancreatic islets, necessitating investigation into human beta-cell responses.
Purpose of the Study:
- To investigate the effects of nitric oxide (NO) on human pancreatic beta-cells in vitro.
- To compare the sensitivity of human and rat islets to NO-induced damage.
Main Methods:
- Isolated human and rat pancreatic islets were exposed to three different nitric oxide donors (SIN-1, GSNO, RBS) for 90 minutes.
- Insulin release, islet DNA content, and cell viability were assessed 48 hours post-exposure.
- DNA strand breaks were evaluated using the comet assay and ultrastructural analysis.
Main Results:
- Nitric oxide donors significantly reduced human islet retrieval, DNA content, and glucose-stimulated insulin release 48 hours after exposure.
- Rat islets showed immediate functional inhibition and similar functional loss after 48 hours compared to human islets.
- Exposure to nitric oxide donors induced significant DNA strand breaks in both human and rat islets, with more severe damage observed in rat islet cells.
Conclusions:
- Nitric oxide donors can induce damage and functional impairment in human pancreatic islets.
- The observed DNA strand breaks suggest a mechanism for nitric oxide-mediated beta-cell toxicity.
- Species differences exist in beta-cell sensitivity to NO, but human islets are demonstrably affected.