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CD39 over-expression prevents autoimmune diabetes through adenosine 2 receptor (A2R) dependent mechanisms

Joanne Chia^1,2, Jennifer McRae¹, Stacey Fynch³, Holger Eltzschig⁴, Simon Robson⁵, Anthony d’Apice¹, Peter Cowan^1,2, Karen Dwyer^1,2

¹Immunology Research Centre, St. Vincent’s Hospital, Fitzroy; ²Department of Medicine, The University of Melbourne, Melbourne; ³Diabetes and Immunology Unit, St. Vincent’s Institute of Medical Research, Fitzroy, Australia; ⁴Department of Anesthesiology and Perioperative Medicine, University of Colorado Health Science Center, Denver, CO; ⁵Liver, Transplantation and Vascular Biology Centers, Beth Israel Deaconess Medical Center, Boston, MA, United States

Background: Type 1 diabetes results from autoimmune mediated destruction of islet cells. Although the transplantation of islet cells offers a potential cure, graft survival is compromised by a number of factors including recurrent autoimmune disease.

Aim: To examine the effect of CD39 over-expression on the development of autoimmune diabetes.

Methods: C57BL/6 male mice over-expressing CD39 (CD39tg), CD39 knock-out (KO), A2ARKO, A2BRKO and wild type (WT) were treated with multiple low dose streptozotocin (MLDS - 50mg/kg ip for 5 days). Some mice were treated with A2BR inhibitor (A2BRi; 0.5mg/kg ip bd). A blood glucose level (BGL) >20mM was deemed diabetic. Adoptive transfer experiments were performed to isolate the effect of CD39 over-expression.

Results: WT mice became diabetic 42 days following MLDS (BGL 21.2±2.4mM). The onset of diabetes was faster in CD39KO, A2ARKO (days 12 & 10 respectively), and A2BRKO mice (day 30). CD39tg mice remained normoglycemic throughout the 90 day follow-up period (BGL 8.1±0.2mM). The protective effect of CD39 over-expression was lost by crossing CD39tg with A2ARKO mice (BGL 21.2±1.2mM at day 30) or by treating the CD39tg with A2BRi (BGL 17.6±1.5mM at day 22). The over-expression of CD39 on tissues alone prevented diabetes (BGL 10.3±1.1mM at day 30).

Conclusion: The over-expression of CD39 mitigates MLDS induced autoimmune diabetes through A2A and A2BR mechanisms. CD39 over-expression on the tissues alone was sufficient to confer this protection. Modification of human islets to over-express CD39 may improve islet graft survival by inhibiting recurrent autoimmune disease.