Abstract 2066: Relationship Between Stat3 And Endoplasmic Reticulum Stress Induces Lipopolysaccharide-induced Endothelial To Mesenchymal Transition In Vascular Endothelial Cell

Abstract

Background: Endothelial to mesenchymal transition (EndMT) is a process that involves the loss of endothelial cell (EC) phenotype and induced plaque instability during the progression of atherosclerosis. Primarily, EC injury, caused by an accelerated inflammatory signaling pathway, plays a crucial role in activating EC dysfunction by inducing endoplasmic reticulum (ER) stress and disrupting EC junctions. In the present study, we investigated the molecular mechanisms between EndMT and ER stress on STAT3-mdeiated inflammation under LPS-treated human umbilical vein EC (HUVEC). Methods: To explore the EndMT progression under chronic inflammation, LPS-treated HUVEC were used. Western blot, siRNA transfection, and immunofluorescence assay were employed to evaluate signaling pathways and target proteins. The phenotypic switching of ECs on the endothelium of the mouse aorta after challenging 10 mg/kg LPS was assessed by en face staining. Results: Deactivation of STAT3 by stattic pretreatment abolished not only LPS-mediated STAT3 phosphorylation, but also VCAM-1 and ICAM-1. In addition, STAT3 inhibition surprisingly reversed LPS-induced mesenchymal markers, including SM22α and vimentin, and the suppression of endothelial marker VE-cadherin. Mechanistically, stattic treatment suppressed LPS-induced EndMT progression by inhibiting protein expression and nuclear translocation of Smad2/3. Furthermore, LPS-induced chronic inflammation disrupted EC homeostasis by PERK or IRE-1α/CHOP-mediated ER stress, whereas stattic abolished LPS-mediated PERK and CHOP expression. Interestingly, depletion of CHOP by siRNA transfection significantly abolished LPS-mediated EndMT progression (p<0.001. Figure 1). Notably, the absence of CHOP significantly suppressed phosphorylation of STAT3 and its nuclear expression as well. Consistent to in vitro data, STAT3 inhibition by stattic injection significantly suppressed LPS-mediated STAT3 activation as well as CHOP expression in the mouse endothelium. Conclusion: Collectively, the STAT3-CHOP axis may contribute to the loss of EC function and induce mesenchymal differentiation by aggravating chronic inflammation and EndMT.