Activation of the dual-leucine-zipper-bearing kinase and induction of beta-cell apoptosis by the immunosuppressive drug cyclosporin A.
Post-transplant diabetes is an untoward effect often observed under immunosuppressive therapy with cyclosporin A. Besides the development of peripheral insulin resistance and a decrease in insulin gene transcription, a beta-cell toxic effect has been described. However, its molecular mechanism remains unknown. In the present study, the effect of cyclosporin A and the dual leucine-zipper-bearing kinase (DLK) on beta-cell survival was investigated. Cyclosporin A decreased the viability of the insulin-producing pancreatic islet cell line HIT in a time- and concentration-dependent manner. Upon exposure to the immunosuppressant fragmentation of DNA, the activation of the effector caspase-3 and a decrease of full-length caspase-3 and Bcl(XL) were observed in HIT cells and in primary mature murine islets, respectively. Cyclosporin A and tacrolimus, both potent inhibitors of the calcium/calmodulin-dependent phosphatase calcineurin, stimulated the enzymatic activity of cellular DLK in an in vitro kinase assay. Immunocytochemistry revealed that the overexpression of DLK but not its kinase-dead mutant induced apoptosis and enhanced cyclosporin A-induced apoptosis to a higher extent than the drug alone. Moreover, in the presence of DLK, the effective concentration for cyclosporin A-caused apoptosis was similar to its known IC(50) value for the inhibition of calcineurin activity in beta cells. These data suggest that cyclosporin A through inhibition of calcineurin activates DLK, thereby leading to beta-cell apoptosis. This action may thus be a novel mechanism through which cyclosporin A precipitates post-transplant diabetes.
Molecular Pharmacology, University of Göttingen, Robert-Koch-Str. 40, 37099 Göttingen, Germany.
Silke
S
Plaumann
Roland
R
Blume
Svenja
S
Börchers
Hans Jürgen
HJ
Steinfelder
Willhart
W
Knepel
Elke
E
Oetjen
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D065095:Calcineurin Inhibitors; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology*; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005562:Formazans / Q000378:metabolism; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D050417:Insulin-Secreting Cells / Q000187:drug effects*; D007700:Kinetics; D020930:MAP Kinase Kinase Kinases / Q000032:analysis / Q000378:metabolism*; D051379:Mice; D013223:Statistics as Topic; D016559:Tacrolimus / Q000494:pharmacology; D013778:Tetrazolium Salts / Q000378:metabolism; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism
D065095:Calcineurin Inhibitors; D005562:Formazans; D007166:Immunosuppressive Agents; D013778:Tetrazolium Salts; D051020:bcl-X Protein; C079782:MTT formazan; D016572:Cyclosporine; D020930:MAP Kinase Kinase Kinases; C090757:mitogen-activated protein kinase kinase kinase 12; D053148:Caspase 3; D016559:Tacrolimus