Pinocembrin suppresses oxidized low-density lipoprotein-triggered NLRP3 inflammasome/GSDMD-mediated endothelial cell pyroptosis through an Nrf2-dependent signaling pathway

Pinocembrin (Pin) has been confirmed to exert anti-inflammatory and antiatherosclerotic effects. Here we have explored whether and how Pin would protect vascular endothelial cells against pyroptosis elicited by the exposure to oxidized low density lipoprotein (oxLDL). Our results showed that Pin preconditioning dose-dependently suppressed oxLDL-stimulated HUVEC injury and pyroptosis, which were manifested by improved cell viability, lower lactate dehydrogenase (LDH) levels and DNA damage as well as decreased expression of pyroptosis-related markers, such as NOD-like receptor pyrin domain-containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (ASC), pro-Caspase-1, cleaved Caspase-1, N-terminus of Gasdermin D-N (GSDMD-N), pro-interleukins-1 beta (pro-IL-1 beta), IL-1 beta and inflammatory cytokines (IL-18 and IL-1 beta). All of the effects were similar to those of MCC950 (an NLRP3 inhibitor). As expected, Pin distinctly activated the Nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidative signaling pathway assessed through increased expressions of Nrf2, heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1). Furthermore, after transfection with small interfering RNA of Nrf2, the inhibitory effects of Pin on oxLDL-triggered NLRP3 inflammasome/GSDMD-mediated pyroptosis and oxidative stress in HUVECs were weakened. Additionally, Pin up-regulated Nrf2/HO-1 axis and down-regulated NLRP3 inflammasome/GSDMD-mediated pyroptosis signals in Apoe(-/-) mice fed with high fat diet. These results contribute to the understanding of the anti-pyroptosis mechanisms of Pin and provide a reference for future research on the anti-atherosclerotic effect of Pin.