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Evolution of Nrf2 Gene Expression in HIT-T15 β-Cells During Chronic Oxidative Stress and Glucose Toxicity
Tsehay Abebe1, Lindsey Bogachus1, Adithya Krishna Vegaraju1
1Department of Internal Medicine, University of Washington, Seattle, USA.
Context:
Chronic exposure of pancreatic islets to elevated glucose levels causes progressive declines in beta cell Pdx-1 and insulin gene expression, and glucose-induced insulin secretion. This has been shown to be associated with excessive islet reactive oxygen species and consequent damage to beta cell function, a process termed glucose toxicity. In short-term rodent in vivo studies, Nrf2 (Kelch-like ECH-associated protein 1:nuclear factor erythroid-derived-2 related factor complex) has been shown to play a central role in defending beta cells from oxidative damage via activation of antioxidant gene expression.
Objective:
The current studies were primarily designed to examine the behavior of Nrf2 gene expression during longer term exposure of beta cells to glucose toxicity.
Methods And Results:
We provide evidence that gene expression of Nrf2 in HIT-T15 cells, an insulin-secreting beta-cell line, undergoes a biphasic response characterized by an initial decrease followed by increased expression during prolonged culturing of these cells in a physiologic (0.8 mM) but not a supraphysiologic (16.0 mM) glucose concentration. This was associated with a slight rise in HO-1 gene expression. Pdx-1 and insulin mRNA levels also decreased but then stabilized in late passages of cells that had been cultured in low glucose concentrations.
Conclusion:
These complex events support the concept that Nrf2 gene expression plays an important regulatory role in defending beta cells during prolonged exposure to oxidative stress.
Insights
Nuclear factor erythroid-derived-2 related factor (Nrf2) gene expression shows a biphasic response in beta cells under prolonged glucose toxicity, indicating a regulatory role in defending against oxidative stress.
Area of Science:
- Cell Biology
- Endocrinology
- Molecular Biology
Background:
- Chronic high glucose levels impair pancreatic beta cell function, a process known as glucose toxicity.
- This impairment is linked to increased reactive oxygen species and damage to beta cells.
- Nuclear factor erythroid-derived-2 related factor (Nrf2) protects beta cells from oxidative damage by activating antioxidant genes.
Purpose of the Study:
- To investigate the behavior of Nrf2 gene expression during prolonged exposure of beta cells to glucose toxicity.
- To understand the role of Nrf2 in beta cell defense mechanisms under sustained oxidative stress.
Main Methods:
- HIT-T15 cells, a beta-cell line, were cultured for extended periods.
- Cells were exposed to either physiologic (0.8 mM) or supraphysiologic (16.0 mM) glucose concentrations.
- Gene expression levels of Nrf2, HO-1, Pdx-1, and insulin were analyzed.
Main Results:
- Nrf2 gene expression in HIT-T15 cells exhibited a biphasic response to prolonged culturing in physiologic glucose: an initial decrease followed by an increase.
- This pattern was not observed in cells cultured in supraphysiologic glucose.
- HO-1 gene expression showed a slight increase, while Pdx-1 and insulin mRNA levels decreased and then stabilized in late passages under low glucose conditions.
Conclusions:
- Nrf2 gene expression plays a significant regulatory role in protecting beta cells during extended periods of oxidative stress.
- The biphasic response of Nrf2 suggests a complex adaptive mechanism in beta cells facing chronic glucose toxicity.
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