Daphnetin prevents acute graft-versus-host disease by suppressing donor T cell expansion and function

Acute graft-versus-host disease (aGVHD), which is primarily driven by donor alloreactive T cells, is a major cause of morbidity and mortality following allogeneic hematopoietic cell transplantation (allo-HCT). Daphnetin (DAPH) shows potent immunosuppressive activity by inhibiting T cell proliferation and function. However, its efficacy in preventing aGVHD remains unexplored. This study aimed to investigate the prophylactic effects of DAPH against aGVHD in murine allo-HCT models and to characterize the underlying mechanisms.

Multiple murine allo-HCT models were established to evaluate the effects of DAPH on aGVHD progression, the graft-versus-leukemia (GVL) effect, and donor immune/hematopoietic cell recovery. Flow cytometry was employed to determine cell proliferation, immune cell alterations, apoptosis profiles, and serum cytokine levels. RNA sequencing and quantitative proteomics analyses were conducted to explore the underlying molecular mechanisms.

DAPH significantly mitigated murine aGVHD following allo-HCT, showing efficacy comparable to that of cyclophosphamide. Notably, DAPH administration did not compromise the GVL effect while transiently delaying the recovery of donor hematopoietic cells. Mechanistically, DAPH inhibited the expansion of multiple donor immune cells, preferentially suppressing the proliferation and functioning of donor conventional T cells. The potential molecular mechanisms underlying the prophylactic efficacy of DAPH against aGVHD after allo-HCT included suppression of the T cell receptor and Janus kinase 3 (JAK3)/signal transducer and activator of transcription 3 (STAT3) signaling pathways.

These findings indicate that DAPH effectively mitigates aGVHD while maintaining the GVL effect and showing minimal influence on donor immune/hematopoietic cell reconstitution. Thus, DAPH is a promising candidate for aGVHD prophylaxis.