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Open Access 01-08-2014 | Article

Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn²⁺ in pancreatic beta cells

Authors: Philipp A. Gerber, Elisa A. Bellomo, David J. Hodson, Gargi Meur, Antonia Solomou, Ryan K. Mitchell, Michael Hollinshead, Fabrice Chimienti, Domenico Bosco, Stephen J. Hughes, Paul R. V. Johnson, Guy A. Rutter

Published in: Diabetologia | Issue 8/2014

Abstract

Aims/hypothesis

Hypoxic damage complicates islet isolation for transplantation and may contribute to beta cell failure in type 2 diabetes. Polymorphisms in the SLC30A8 gene, encoding the secretory granule zinc transporter 8 (ZnT8), influence type 2 diabetes risk, conceivably by modulating cytosolic Zn²⁺ levels. We have therefore explored the role of ZnT8 and cytosolic Zn²⁺ in the response to hypoxia of pancreatic islet cells.

Methods

Human, mouse or rat islets were isolated and exposed to varying O₂ tensions. Cytosolic free zinc was measured using the adenovirally expressed recombinant targeted zinc probe eCALWY4. Gene expression was measured using quantitative (q)RT-PCR, western (immuno-) blotting or immunocytochemistry. Beta cells were identified by insulin immunoreactivity.

Results

Deprivation of O₂ (1% vs 5% or 21%) for 24 h lowered free cytosolic Zn²⁺ concentrations by ~40% (p < 0.05) and ~30% (p < 0.05) in mouse and human islet cells, respectively. Hypoxia similarly decreased SLC30A8 mRNA expression in islets, and immunoreactivity in beta cells. Implicating lowered ZnT8 levels in the hypoxia-induced fall in cytosolic Zn²⁺, genetic ablation of Slc30a8 from mouse islets lowered cytosolic Zn²⁺ by ~40% (p < 0.05) and decreased the induction of metallothionein (Mt1, Mt2) genes. Cell survival in the face of hypoxia was enhanced in small islets of older (>12 weeks) Slc30a8 null mice vs controls, but not younger animals.

Conclusions/interpretation

The response of pancreatic beta cells to hypoxia is characterised by decreased SLC30A8 expression and lowered cytosolic Zn²⁺ concentrations. The dependence on ZnT8 of hypoxia-induced changes in cell survival may contribute to the actions of SLC30A8 variants on diabetes risk in humans.

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Title: Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells
Authors: Philipp A. Gerber
Elisa A. Bellomo
David J. Hodson
Gargi Meur
Antonia Solomou
Ryan K. Mitchell
Michael Hollinshead
Fabrice Chimienti
Domenico Bosco
Stephen J. Hughes
Paul R. V. Johnson
Guy A. Rutter
Publication date: 01-08-2014
Publisher: Springer Berlin Heidelberg
Published in: Diabetologia / Issue 8/2014
Print ISSN: 0012-186X
Electronic ISSN: 1432-0428
DOI: https://doi.org/10.1007/s00125-014-3266-0

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