The purinergic receptor antagonist oxidized adenosine triphosphate suppresses immune-mediated corneal allograft rejection

Abstract

Adenosine triphosphate (ATP) is released into the extracellular environment during transplantation, and acts via purinergic receptors to amplify the alloimmune response. Here, using a well-established murine model of allogeneic corneal transplantation, we investigated the immunomodulatory mechanisms of the purinergic receptor antagonist oxidized ATP (oATP). Corneal transplantation was performed using C57BL/6 donors and BALB/c hosts. oATP or sterile saline was administered via intraperitoneal injection for 2 weeks postoperatively. Frequencies of CD45 + leukocytes, CD11b + MHCII + antigen presenting cells (APCs), CD4 + IFN-γ + effector Th1 cells and CD4 + Foxp3 + regulatory T cells (Tregs) were evaluated by flow cytometry. Slit-lamp microscopy was performed weekly for 8 weeks to evaluate graft opacity and determine transplant rejection. Treatment with oATP was shown to significantly reduce graft infiltration of CD45 + leukocytes, decrease APC maturation and suppress effector Th1 cell generation relative to saline-treated control. No difference in Treg frequencies or Foxp3 expression was observed between the oATP-treated and control groups. Finally, oATP treatment was shown to reduce graft opacity and increase graft survival. This report demonstrates that oATP limits the alloimmune response by regulating APC maturation and suppressing the generation of alloreactive Th1 immunity.

The NLRP3 inflammasome regulates corneal allograft rejection through enhanced phosphorylation of STAT3

“…17,[27][28][29][30]48,49 Consistent with these studies, we found that increased eATP also exacerbated corneal allograft rejection via the P2X7 receptor. Pharmacological blockade of ATP/P2X7 signaling not only reduced corneal allograft rejection, in line with results by Foulsham et al, 50 but also significantly blunted the NLRP3 inflammasome-mediated maturation and release of IL-1β. However, further studies are needed to explore the mechanism that regulates the release of ATP, which remains largely unknown in our pathological scenarios.…”

When rubber meets the road: how innate features of adaptive immune cells play critical roles in transplant alloimmunity

“…As ATP can be released during damage elicited by ischemia and reperfusion, the P2X4-ATP pathway likely contributes to the recruitment and activation of naı ¨ve T cells into the graft. Another study on this topic revealed that use of a purinergic receptor antagonist, oxidized ATP, results in diminished IFNg-secreting T H 1 CD4 þ T cells and prolonged graft survival in a murine corneal transplant model [2]. These data suggest that extracellular ATP plays an important role in the activation of alloreactive T cells, whether through decreased maturation of CD11b þ APCs as this group showed, or through T-cell intrinsic immunomodulatory mechanisms that have been reported by others [3,4].…”

Non‐immune and immune functions of interleukin‐36γ suppress epithelial repair at the ocular surface

“…In the current study, we show that epithelium‐derived IL36γ promotes the migration of immune cells to the injured tissue, as indicated by a significant 34% reduction in the frequencies of total CD45 + leukocytes in corneas treated with IL36RA. Previous studies have shown that corneal immune microenvironment is dependent not only on the frequencies, but also specific immune cell subsets 32,33 . Our detailed analysis of immune cell subsets demonstrates IL36RA treatment results in approximately 47% and 24% reduction in the frequencies of neutrophils and macrophages, respectively, at the ocular surface.…”

“…Previous studies have shown that corneal immune microenvironment is dependent not only on the frequencies, but also specific immune cell subsets. 32,33 Our detailed analysis of immune cell subsets demonstrates IL36RA treatment results in approximately 47% and 24% reduction in the frequencies of neutrophils and macrophages, respectively, at the ocular surface. Moreover, we show that IL36γ promotes the activation of immune cells at the ocular surfaces, as evidenced by the significant decrease in the expression of IL1β and TNFα following in vivo administration of IL36Ra to mouse corneas.…”