Fisetin prevents oxidized low-density lipoproteins induced macrophage foam cell formation.

ABSTRACT Foam cell formation in an important event in atherosclerosis. Fisetin, a bioflavonoid, has long been identified to possess anti-inflammatory, anti-lipidemic and anti-cancerous properties, however its role as a lipid homeostasis regulator in macrophage specifically in presence of metabolic stressors such as oxLDL is not well understood. In this study we have investigated the role of fisetin in preventing oxLDL-induced macrophage FCF. U937-derived macrophages were stimulated with oxLDL with or without fisetin for varied time points and various parameters were assessed including cell viability by MTT assay, ROS by DCFDA assay, lipid accumulation by Oil Red O staining, and expression of NLRP3, Sterol regulatory element binding protein (SREBP)-1 and associated downstream proteins HMG CoA reductase (HMGCR) and fatty acid synthase (FAS) were assessed by RT-qPCR and immunoblotting. Functionality of FAS enzyme was determined using enzyme activity assay. Docking studies were performed to determine in-silico interaction between NLRP3 and fisetin. The results showed that fisetin, up to the dose of 10 µM did not alter cell viability but at the same dose could decrease the accumulation of lipids in macrophages and prevented FCF. Fisetin could also ameliorate and reduce oxLDL-induced upregulation of SREBP-1 and thereby expression of its downstream liposynthesis genes HMGCR and FAS and inhibited ROS-induced NLRP3 inflammasome activation. In conclusion, fisetin could inhibit foam cell formation by blocking oxLDL induced ROS formation and subsequent NLRP3 activation, thereby inhibiting SREBP-1 and its downstream genes including FAS and HMGCR.