title: Hypoxia lowers SLC30A8/ZnT8 expression and free cytosolic Zn2+ in pancreatic beta cells.
abstract: OBJECTIVE
  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 Zn(2+) levels. We have therefore explored the role of ZnT8 and cytosolic Zn(2+) 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 Zn(2+) 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 Zn(2+), genetic ablation of Slc30a8 from mouse islets lowered cytosolic Zn(2+) 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
  The response of pancreatic beta cells to hypoxia is characterised by decreased SLC30A8 expression and lowered cytosolic Zn(2+) 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.
authors.affiliation: Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, W12 ONN, UK.
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Gerber
authors.forename: Elisa A
authors.initials: EA
authors.lastname: Bellomo
authors.forename: David J
authors.initials: DJ
authors.lastname: Hodson
authors.forename: Gargi
authors.initials: G
authors.lastname: Meur
authors.forename: Antonia
authors.initials: A
authors.lastname: Solomou
authors.forename: Ryan K
authors.initials: RK
authors.lastname: Mitchell
authors.forename: Michael
authors.initials: M
authors.lastname: Hollinshead
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chimienti
authors.forename: Domenico
authors.initials: D
authors.lastname: Bosco
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Hughes
authors.forename: Paul R V
authors.initials: PR
authors.lastname: Johnson
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rutter
mesh_terms: D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D051379:Mice; D051381:Rats; D015032:Zinc / Q000378:metabolism*; D000075703:Zinc Transporter 8
chemical_list: D027682:Cation Transport Proteins; C492522:SLC30A8 protein, human; D000075703:Zinc Transporter 8; D008668:Metallothionein; D015032:Zinc