Apoptosis in hypoxic human pancreatic islets correlates with HIF-1alpha expression.
To become insulin independent, patients with type 1 diabetes mellitus require transplantation of at least two donor pancreata because of massive beta-cell loss in the early post-transplantation period. Many studies describing the introduction of new immunosuppressive protocols have shown that this loss is due to not only immunological events but also nonimmunological factors. To test to what extent hypoxia may contribute to early graft loss, we analyzed the occurrence of apoptotic events and the expression of hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor consisting of an oxygen-dependent alpha subunit and a constitutive beta subunit. Histological analysis of human and rat islets revealed nuclear pyknosis as early as 6 h after hypoxic exposure (1% O2). Moreover, immunoreactivity to activated caspase-3 was observed in the core region of isolated human islets. Of note, both of these markers of apoptosis topographically overlap with HIF-1alpha immunoreactivity. HIF-1alpha mRNA was detected in islets from human and rat as well as in several murine beta-cell lines. When exposed to hypoxia, mouse insulinoma cells (MIN6) had an increased HIF-1alpha protein level, whereas its mRNA level did not alter. In conclusion, our data provide convincing evidence that reduced oxygenation is an important cause of beta-cell loss and suggest that HIF-1alpha protein level is an indicator for hypoxic regions undergoing apoptotic cell death. These observations suggest that gene expression under the control of HIF-1 represents a potential therapeutic tool for improving engraftment of transplanted islets.
Moritz
Wolfgang
W
Clinic for Visceral and Transplant Surgery, University Hospital Zürich, CH-8091 Zürich, Switzerland.
Meier
Franziska
F
Stroka
Deborah M
DM
Giuliani
Mauro
M
Kugelmeier
Patrick
P
Nett
Philipp C
PC
Lehmann
Roger
R
Candinas
Daniel
D
Gassmann
Max
M
Weber
Markus
M
D021581:Active Transport, Cell Nucleus; D000818:Animals; D017209:Apoptosis; D015687:Cell Hypoxia; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism*; D008954:Models, Biological; D051381:Rats; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D015854:Up-Regulation
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D014157:Transcription Factors