PPARα Agonist Stimulated Angiogenesis by Improving Endothelial Precursor Cell Function Via a NLRP3 Inflammasome Pathway

Abstract

Background: Impaired wound healing is a common complication of diabetes and is the leading cause of lower extremity amputation. Treatment with fenofibrate, a peroxisome proliferators–activated receptor α (PPARα) agonist, was associated with a lower risk of amputations, particularly minor amputations without known large-vessel diseases, probably through non-lipid mechanisms. The current study aimed to test our hypothesis that fenofibrate stimulates angiogenesis and restores endothelial precursor cell (EPC) function via inhibiting Nod-like receptor protein 3 (NLRP3) inflammasome in streptozotocin (STZ)-induced diabetic mice. Methods: Male C57BL/6 mice were randomly divided into three groups: control, STZ-induced diabetic mice and fenofibrate treated diabetic group. Wound closure was assessed by wound area and CD31 positive capillaries. Both the migration and tube formation capacities of EPCs were measured. Intracellular nitric oxide (NO) and superoxide (O₂^-) levels were determined. Activity of NLRP3 inflammasome in EPCs was assessed by measuring thioredoxin-interacting protein (TXNIP), NLRP3, and caspase-1 expression. Results: Compared with the untreated diabetic mice, wound closure and capillary densities were significantly increased in fenofibrate treated group. Fenofibrate treatment restored EPC function, increased NO production, and decreased O₂^- level in EPCs of diabetic mice. Furthermore, fenofibrate deregulated the activity of NLRP3 inflammasome by reducing TXNIP, NLRP3 and caspase-1 expression in EPCs of diabetic mice. In vitro, fenofibrate prevented high glucose induced EPC dysfunction, deregulated NLRP3 inflammasome activity. In addition, fenofibrate inhibited IL-1β expression caused by combination use of high glucose and lipopolysaccharide. Conclusion: Fenofibrate can accelerate wound healing in diabetic mice, which at least in part was mediated by improving the impaired EPC function via a NLRP3 inflammasome pathway, suggesting the significance of PPARα agonists in the treatment of diabetes.