Inhibition of AMP-activated protein kinase protects pancreatic beta-cells from cytokine-mediated apoptosis and CD8+ T-cell-induced cytotoxicity.
OBJECTIVE
Apoptotic destruction of insulin-producing pancreatic beta-cells is involved in the etiology of both type 1 and type 2 diabetes. AMP-activated protein kinase (AMPK) is a sensor of cellular energy charge whose sustained activation has recently been implicated in pancreatic beta-cell apoptosis and in islet cell death posttransplantation. Here, we examine the importance of beta-cell AMPK in cytokine-induced apoptosis and in the cytotoxic action of CD8(+) T-cells.


METHODS
Clonal MIN6 beta-cells or CD1 mouse pancreatic islets were infected with recombinant adenoviruses encoding enhanced green fluorescent protein (eGFP/null), constitutively active AMPK (AMPK-CA), or dominant-negative AMPK (AMPK-DN) and exposed or not to tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma. Apoptosis was detected by monitoring the cleavage of caspase-3 and DNA fragmentation. The cytotoxic effect of CD8(+) purified T-cells was examined against pancreatic islets from NOD mice infected with either null or the AMPK-DN-expressing adenoviruses.


RESULTS
Exposure to cytokines, or expression of AMPK-CA, induced apoptosis in clonal MIN6 beta-cells and CD1 mouse pancreatic islets. By contrast, overexpression of AMPK-DN protected against the proapoptotic effect of these agents, in part by preventing decreases in cellular ATP, and lowered the cytotoxic effect of CD8(+) T-cells toward NOD mouse islets.


CONCLUSIONS
Inhibition of AMPK activity enhances islet survival in the face of assault by either cytokines or T-cells. AMPK may therefore represent an interesting therapeutic target to suppress immune-mediated beta-cell destruction and may increase the efficacy of islet allografts in type 1 diabetes.
Riboulet-Chavey
Audrey
A
Professor and Head of Department of Cell Biology, Division of Medicine, Sir Alexander Fleming Building, Imperial College, London, Exhibition Road, London SW7 2AZ, UK.
Diraison
Frédérique
F
Siew
L Khai
LK
Wong
F Susan
FS
Rutter
Guy A
GA
D055372:AMP-Activated Protein Kinases; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016207:Cytokines / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000473:pathology / Q000502:physiology*; D008213:Lymphocyte Activation; D051379:Mice; D016688:Mice, Inbred NOD; D008822:Mice, Transgenic; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011948:Receptors, Antigen, T-Cell / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D016207:Cytokines; D009097:Multienzyme Complexes; D011948:Receptors, Antigen, T-Cell; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases