RRC ID 6028
Author Tanemura M, Saga A, Kawamoto K, Machida T, Deguchi T, Nishida T, Sawa Y, Doki Y, Mori M, Ito T.
Title Rapamycin induces autophagy in islets: relevance in islet transplantation.
Journal Transplant. Proc.
Abstract Islet transplantation can provide insulin independence in patients with type 1 diabetes mellitus. However, islet allograft recipients exhibit a gradual decline in insulin independence, and only 10% do not require insulin at 5 years. This decline may reflect drug toxicity to islet beta cells. Rapamycin, a central immunosuppressant in islet transplantation, is a mammalian target of rampamycin inhibitor that induces autophagy. The relative contributions of autophagy in transplanted islets are poorly understood. Therefore, in the present study we sought to evaluate the effects of rapamycin on islet beta cells. Rapamycin treatment of islets resulted in accumulation of membrane-bound light chain 3 (LC3-II) protein, an early marker of autophagy. In addition, rapamycin treatment of isolated islets elicited not only reduction of viability but also downregulation of in vitro potency. To further examine the occurrence of autophagy in rapamycin-treated islets, we used GFP (green fluorescent protein)-LC3 transgenic mice that express a fluorescent autophagosome marker. The GFP-LC3 signals were markedly increased in rapamycin treated islets compared with control islets. In addition, to show improvement by blockade of autophagic signaling, islets were treated with rapamycin in the presence of 3-methyladenine, which inhibits autophagy. Thereafter, both islet viability and islet potency were dramatically improved. The number of GFP-LC3 dots clearly increased after 3-MA treatment. Thus, rapamycin treatment of islets induces autophagy in vitro. This phenomenon may contribute to the progressive graft dysfunction of transplanted islets. Therapeutically targeting this novel signaling may yield significant benefits for long-term islet survival.
Volume 41(1)
Pages 334-8
Published 2009-1
DOI 10.1016/j.transproceed.2008.10.032
PII S0041-1345(08)01457-7
PMID 19249550
MeSH Animals Autophagy / drug effects* Autophagy / physiology Genes, Reporter Glucose / pharmacology Immunoglobulin Light Chains / genetics Insulin / metabolism Insulin Secretion Islets of Langerhans / cytology* Islets of Langerhans / drug effects Islets of Langerhans / physiology* Islets of Langerhans Transplantation / physiology* Male Mice Mice, Transgenic Signal Transduction Sirolimus / pharmacology* Transfection
IF 0.959
Times Cited 21
Mice GFP-LC3#53