Survival Improvements Following Omega-3 Polyunsaturated Fatty Acid Dietary Enrichment, Acetylsalicylic Acid, and Aspirin-Triggered Lipoxin Administration in a Lethal Mouse Model of Acute Graft-Versus-Host Disease

Background:  Lipoxins (derived from arachidonic acid) and the resolvins and protectins (derived from ω3-polyunsaturated fatty acids (PUFAs)) are endogenously produced lipid mediators with potent anti-inflammatory and tissue healing properties.  Acetylsalicylic acid (ASA, aspirin) results in the synthesis of aspirin-triggered lipoxins, isomers for these lipid mediators with identical anti-inflammatory actions.  In part, these lipid mediators act through downregulation of Th1 cytokines known to be important in aGVHD pathogenesis.    The C56BL/6→(C57BL/6 x DBA/2)F₁-hybrid is a major histocompatibility mismatched mouse model of lethal aGVHD (similar to a non T-cell depleted HLA haploidentical BMT without GVHD prophylaxis) that allows isolation of the aGVHD effect.  We wanted to test whether these novel lipid mediators could attenuate aGVHD in this highly inflammatory allogeneic transplant mouse model.  

Methods: Mice were transplanted according to standard protocols.  Four diets were created, including a control diet containing 2% ω6-PUFAs; and three experimental diets, enriched for (1) 2% ω3-PUFAs (2) 2% ω6-PUFAs plus ASA (0.02 mg/g of feed) (3) 2% ω3-PUFAs plus ASA.  Mice were randomly fed one diet (n=10-12 per group) for 8-weeks before transplant and the same diet after transplant.  A separate experiment confirmed that feeding the different diets for 8-weeks before transplant resulted in differential tissue (liver) stores of ω6- and ω3-PUFAs.  A fifth group (n=10) was fed the control diet but injected with the aspirin-triggered lipoxin 15-epi-LxA4 IV on day 0 and IP on day 7 (200 mcg/kg/dose).  The primary outcome was days before the onset of aGVHD-associated morbidity (humane end point) post-transplant.

Results:  Control GVH mice met the humane end-point for euthanasia as result of aGVHD at a median of 14 days post-transplant (range: 9-16 days).  Kaplan-Meier survival curves showed modest but statistically significant improvements in survival for mice fed a diet enriched for ω3-PUFAs plus ASA (p=0.0117) and mice receiving the aspirin-triggered lipoxin (p=0.034) compared to the control group.  Survival improvements and the onset of lethal aGVHD were delayed by a matter of days for the mice receiving the interventions.

Conclusion:  We provide proof-of-principle that dietary ω3-PUFAs, aspirin, and aspirin-triggered lipoxins may offer novel ways to counteract aGVHD.   Our interventions approximate acceptable human dietary intake for ω3-PUFAs and taking a baby-aspirin once per day.   Further experiments using different aGVHD mouse models are planned.