(748) Peroxisome proliferator-activated receptor delta loss reduces alloreactive CD4 T cell proliferation and lessens graft-versus-host-disease severity

Introduction/Rationale: Our lab previously demonstrated that murine alloreactive T cells increase fatty acid oxidation (FAO) during graft-versus-host disease (GVHD), and more recently, we observed higher levels of peroxisome proliferator-activated receptor delta (PPARδ) in donor T cells after transplantation. Therefore, we hypothesize that PPARδ-driven FAO in T cells plays a role in GVHD development.

Methods: We first conducted in vitro assays on wild-type (WT) T cells using a PPARδ-specific agonist. Then, we created a T cell conditional PPARδ knockout (KO) mouse strain to supply donor T cells for our GVHD model.

Results: We found that GW501516-treated T cells stimulated by MLR had increased transcript levels of FAO genes: a 2-fold increase in acetyl-CoA acyltransferase 2 (Acaa2), a 4-fold increase in perilipin-2 (Plin2) in CD8 T cells as well as a 6-fold (Acaa2) and an 8-fold (Plin2) increase in CD4 T cells (multiple t-test, p=0.01). PPARδ agonism of MLR-stimulated T cells also increased FAO in CD8 and CD4 T cells in radiolabeled palmitate oxidation assays (unpaired t-test, p=0.01).
In our GVHD model, deleting PPARδ in donor T cells improved survival (median: WT=20; KO=33) compared to WT donor T cell recipients (one-way ANOVA, p=0.01). Notably, on Day 7 after transplantation, we saw a significant decrease in proliferating donor CD4 T cells, but not CD8 T cells, from PPARδ KO donors. We also noted reduced proliferation of CD4 PPARδ KO T cells on Day 5 post-transplant and during in vitro stimulation assays (Walsh t-test, p=0.01). In the context of a CD4-only GVHD model, survival in PPARδ KO recipients was even more improved compared to WT recipients (median: WT=51; KO=undef). Flow cytometry and histology analysis on Day 21 post-transplant showed lower donor lymphocyte frequencies and fewer total donor CD4+ T cells in the liver and small intestines of PPARδ KO recipients.

Conclusion: These data overall indicate that the loss of PPARδ impairs the ability of donor T cells to infiltrate target organs during GVHD progression.