Loss of 12-Lipoxygenase Improves the Post-Transfusion Function of Stored Platelets

Objective Platelets for transfusion are stored for 5-7 days. During storage, platelets undergo numerous detrimental functional changes. Previous studies have shown that HETE levels in the storage bag negatively correlate with platelet performance in vivo suggesting that the dysregulation of bioactive lipid mediators may contribute to the storage lesion. In the current study, we sought to understand how genetic deletion and pharmacologic inhibition of 12-lipoxygenase (12-LOX) affects platelets during storage and after transfusion. Approach and Results Platelets from12-LOX+/+ (wild-type [WT]) and 12-LOX-/- mice were stored for 24 and 48 hours and profiled using LC-MS/MS-MRM. Polyunsaturated fatty acids increased significantly in stored platelets from 12-LOX-/- mice, while oxylipin concentrations were significantly higher in WT platelets. Baseline αIIbβ 3 integrin activation was significantly lower before and after 24 hours of storage in 12-LOX-/- platelets than in WT platelets. Surprisingly, after transfusion to thrombocytopenic mice, we observed significantly more baseline αIIbβ3 integrin activation in 12-LOX-/- platelets than in WT platelets. Stored platelets from 12-LOX-/- mice occluded vessels significantly faster than stored WT platelets in thrombocytopenic recipients challenged with a FeCl 3-induced carotid artery injury. In hemostasis models, significantly more stored 12-LOX-/- than WT platelets accumulated at the site of venous injury leading to reduced blood loss. Inhibition of cyclooxygenase-1 (COX-1) with acetylsalicylic acid abrogated both increased integrin activation and thromboxane generation in stored 12-LOX-/- platelets, highlighting a critical role of this pathway for improved post-transfusion function. Consistent with our mouse studies, human platelets stored with the 12-LOX inhibitor, VLX-1005, showed increased integrin activation compared to vehicle-treated platelets upon transfusion in NOD/SCID mice. Conclusion Deleting 12-LOX improves the post-transfusion function of stored murine and human platelets by increasing thromboxane generation through a COX-1-dependent mechanism. Future studies should determine the feasibility and safety of 12-LOX-inhibited platelets transfused to humans.