Renal ischemia-reperfusion injury and adenosine 2A receptor-mediated tissue protection: The role of CD4⁺ T cells and IFN-γ

A_2A adenosine receptor (A_2AR)-expressing bone marrow (BM)-derived cells contribute to the renal protective effect of A_2A agonists in renal ischemia-reperfusion injury (IRI). We performed IRI in mice lacking T and B cells to determine whether A_2AR expressed in CD4 ⁺ cells mediate protection from IRI. Rag-1 knockout (KO) mice were protected in comparison to wild-type (WT) mice when subjected to IRI. ATL146e, a selective A_2A agonist, did not confer additional protection. IFN-γ is an important eariy signal in IRI and is thought to contribute to reperfusion injury. Because IFN-γ is produced by kidney cells and T cells we performed IRI in BM chimeras in which the BM of WT mice was reconstituted with BM from IFN-γ KO mice (IFN-γ KO→WT chimera). We observed marked reduction in IRI in comparison to WT→WT chimeras providing additional indirect support for the role of T cells. To confirm the role of CD4⁺ A_2AR in mediating protection from IRI, Rag-1 KO mice were subjected to ischemia-reperfusion. The protection observed in Rag-1 KO mice was reversed in Rag-1 KO mice that were adoptively transferred WT CD4 ⁺ cells (WT CD4⁺→Rag-1 KO) or A_2A KO CD4⁺ cells (A_2A KO CD4⁺→Rag-1 KO). ATL146e reduced injury an WT CD4⁺→Rag-1 KO mice but not in A _2A KO CD4⁺→Rag-1 KO mice. Rag-1 KO mice reconstituted with CD4⁺ cells derived from IFN-γ KO mice (IFN-γ CD4⁺-→Rag-1 KO) were protected from IRI; ATL146e conferred no additional protection. These studies demonstrate that CD4⁺ IFN-γ contributes to IRI and that A_2A agonists mediate protection from IRI through action on CD4⁺ cells.