Puerarin inhibits hyperglycemia-induced inter-endothelial junction through suppressing endothelial Nlrp3 inflammasome activation via ROS-dependent oxidative pathway

Abstract

Background: Recent studies indicate that vascular complications are closely related to diabetes mellitus; in particular, inflammatory-mediated endothelial dysfunction plays a crucial role in diabetes-induced cardiovascular diseases. Therefore, exploring effective methods to suppress endothelial dysfunction via inhibition of inflammatory responses is imperative. Puerarin (Pu), a flavonoid common in Pueraria, has been widely and successfully used to treat cardiovascular diseases in China for many years. However, information on its protective properties in hyperglycemia-induced vascular complications is insufficient. Hypothesis/Purpose: In this study, we investigate the protective effects of puerarin against high glucose-induced endothelial dysfunction and the underlying mechanism of the flavonoid.

Methods: we investigated the protective effects of Pu against hyperglycemia-induced inter-endothelial junction by permeability and transendothelial electrical resistance (TEER) assay. In addition, changes in the Nlrp3 inflammasome activation via reactive oxygen species (ROS)-dependent oxidative pathway were investigated using western blot, immunofluorescence microscopy analyses and flow cytometry. ROS scavenger and Nlrp3 gene silencing were used to determine the roles of the ROS-Nlrp3 pathway involved in the molecular mechanism of Pu.

Results: Our findings demonstrate that puerarin inhibits high glucose-induced Nlrp3 inflammasome formation and activation, as shown by fluorescence confocal microscopy and Western blot. Puerarin decreases Nlrp3 protein, which is a critical factor necessary to form an inflammasome complex. We demonstrate that puerarin exerts anti-oxidation and ROS scavenged effects, similar to apocynin (APO). Interestingly, thioredoxin-interacting protein (TXNIP) protein and TXNIP binding to Nlrp3 markedly decreased with puerarin treatment. Together with these changes, puerarin could decrease high mobility group box 1 (HMGB1) release from mouse vascular endothelial cell (mMVECs). We also demonstrate the decreased expression of the tight junction proteins ZO-1/ZO-2, which are related to endothelial permeability after stimulation by high glucose in endothelial cells. Puerarin could recover the gap junction protein and decrease monolayer cell permeability in endothelial cells. In conclusion, we reveal a new protection mechanism of puerarin that inhibits Nlrp3 inflammasome activation and decreases subsequent caspase-1 activation, triggering the release of HMGB1 by reducing ROS generation.

Conclusions: Our findings indicate that puerarin exhibits immense potential and specific therapeutic value in hyperglycemia-related cardiovascular disease and the development of innovative drugs.

Keywords: APO; Endothelium; HMGB1; Hyperglycemia; Nlrp3 inflammasome; Pu; ROS; TEER; TXNIP; Tight junction proteins; apocynin; high mobility group box 1; mMVECs; mouse vascular endothelial cell; puerarin; reactive oxygen species; thioredoxin-interacting protein; transendothelial electrical resistance.