Deficiency of CD73/ecto-5′-nucleotidase in mice enhances acute graft-versus-host disease

Abstract

Extracellular ATP and adenosine have immunoregulatory roles during inflammation. Elevated extracellular ATP is known to exacerbate GVHD, and the pharmacologic activation of the adenosine A 2A receptor is protective. However, the role of endogenous adenosine is unknown. We used gene-targeted mice and a pharmacologic inhibitor to test the role of adenosine generated by CD73/ecto-5-nucleotidase in GVHD. In allogeneic transplants, both donor and recipient CD73 were protective, with recipient CD73 playing the dominant role. CD73 deficiency led to enhanced T-cell expansion and IFN-␥ and IL-6 production, and the migratory capacity of Cd73 ؊/؊ T cells in vitro was increased. However, the number of regulatory T cells and expression of costimulatory molecules on antigen-presenting cells were unchanged. A 2A receptor deficiency led to increased numbers of allogeneic T cells, suggesting that signaling through the A 2A receptor via CD73-generated adenosine is a significant part of the mechanism by which CD73 limits the severity of GVHD. IntroductionPatients with hematologic malignancies that are refractory to conventional chemotherapy have a chance of cure by allogeneic hematopoietic stem cell transplantation (allo-HCT). 1 However, the success of this treatment is limited by GVHD. 2 We have recently shown that extracellular ATP, which is released from dying or stressed cells and serves as an endogenous danger signal to evoke systemic inflammatory responses, enhances GVHD by activation of the purinergic receptor P2X 7 R. 3,4 The abundance of extracellular ATP is regulated by ecto-nucleotidases, such as CD39, which dephosphorylates ATP to ADP and AMP. Extracellular AMP is dephosphorylated to adenosine via the action of CD73, a glycosyl phosphatidylinositol-anchored glycoprotein with ecto-5Ј-nucleotidase enzyme activity. 5-7 CD73 is expressed on many cell types, including subsets of T lymphocytes, endothelial cells, and epithelial cells. 7,8 It is also present as a secreted form lacking a glycosyl phosphatidylinositol anchor. 9 CD73-generated adenosine can activate any of 4 G-protein-coupled 7-transmembrane-spanning adenosine receptors (ARs; A 1 , A 2A , A 2B and A 3 ) and can act as either a pro-or anti-inflammatory mediator depending on the physiologic setting and the type of AR engaged. [10][11][12] In most circumstances, A 1 and A 3 receptor triggering is proinflammatory, whereas activation of A 2A and A 2B receptors is antiinflammatory or tolerogenic. 13,14 The importance of CD73 in producing adenosine for AR signaling has been revealed through studies with CD73-deficient mice. For example, CD73-generated adenosine reduces inflammation and fibrosis in lungs of bleomycin-treated mice 15 and is tolerogenic for cardiac and airway allografts. 16,17 CD73-dependent A 2B AR signaling protects mice during renal ischemia, 18 inhibits systemic vascular leakage during hypoxia, 19,20 and is also required for cardioprotection as a result of ischemic preconditioning. 21 Extracellular adenosine inhibits platelet activation and leukocyte...

CD73-Deficient Mice Are Resistant to Carcinogenesis

“…In particular, CD73 expression on Foxp3 þ T regulatory cells is important for their suppression of antitumor immunity (15). Notably, host CD73 has been shown to protect against acute graft versus host disease and to inhibit graft versus leukaemia effect (17). Taken together, these studies suggest that CD73 may be a valid therapeutic target to enhance antitumor immunity.…”

Siglec-G–CD24 axis controls the severity of graft-versus-host disease in mice

“…However, recent experimental studies suggests a role for DAMPs such as ATP, heparan sulfate (HS), and uric acid, in enhancing allogeneic T-cell responses and in exacerbating GVHD. 15,17,32 Clinically, the data also suggests that response to DAMPs such as HMGB-1, 35 heat shock protein 70 (HSP70), 36,37 and HSP90 38 may be associated with GVHD severity in humans. In line with this notion, several pattern recognition receptors that are known to activate innate immunity in response to DAMP-mediated stimulation of APCs have been shown to exacerbate GVHD.…”

“…Host tissue damage after conditioning is known to lead to the release of not only proinflammatory cytokines, but also DAMPs and PAMPs. 6,15,27,[32][33][34] Both DAMPs and PAMPs can activate APCs and enhance T-cell responses. 7 The role of PAMPs in exacerbating GVHD may be model/context dependent.…”

Altered homeostatic regulation of innate and adaptive immunity in lower gastrointestinal tract GVHD pathogenesis

“…Activated Tcons proliferate and trigger release of alarmins, such as IL-33 and its soluble receptor ST2, from non-HP APCs, such as stromal cells and endothelium; these activated Tcons also express the integrin receptor α 4 β 7 , which directs their migration back to intestinal tissue after entering the villus capillaries. the absence of CD73 on either donor T cells or host APCs exacerbated GVHD (54)(55)(56). UA, a purine metabolite released from damaged cells, is an endogenous DAMP that stimulates DCs and activates CD8 + T cell cytotoxic functions (45,57).…”