Protective Action of Prostamide E2 from Homocysteine‐induced NLRP3Inflammasome Activation and Podocyte Injury

Abstract

Recent studies have demonstrated that homocysteine (Hcys)-induced podocyte damage and subsequent podocyte injury and glomerular sclerosis are attributed to the activation of NLRP3 inflammasomes. Given the possible immunosuppressive effect of endogenous cannabinoids, the present study was designed to test whether prostamide E2 (PE2), COX-2 metabolite of anandamide (AEA) diminishes Hcys-induced NLRP3 inflammasome activation and podocyte injury. By confocal microscopy, Hcys treatment of podocytes was found to induce NLRP3 inflammasome formation as demonstrated by the increase in colocalization between three major inflammasome proteins-NLRP3, ASC and caspase-1. Accompanying these effects, elevated Hcys resulted in increased caspase-1 activity and IL-1β production in podocytes. This increase in Hcys-induced NLRP3 inflammasome formation and activation was substantially inhibited by PE2 pretreatment with a maximum inhibition >60% of the Hcys-induced caspase-1 activity and IL-1β production. Anandamide only had such inhibitory effect on inflammasome activation at a concentration 10 times higher than PE2, which was blockable by cox-2 inhibitor. Furthermore, PE2 was found to preserve podocyte morphology by maintaining the distinct arrangement of F-actin fibers normally lost in response to Hcys. It also prevented podocyte dysfunction by restoring Hcys-induced suppression of VEGF production and secretion and by inhibition of Hcys-induced decreases in podocin and increases in desmin. Together, these results provide evidence that PE2 may exert its anti-inflammatory action by suppression of Hcys-induced NLRP3 inflammasome activation and prevention of podocyte injury and dysfunction.