Cytokine-induced autophagy promotes long-term VCAM-1 but not ICAM-1 expression by degrading late-phase I\u03baB\u03b1

Ling-Yun Chu,Ying-Chang Hsueh,Hsiao-Ling Cheng,Kenneth K. Wu

doi:10.1038/s41598-017-12641-8

Abstract

Pro-inflammatory cytokines are known to induce endothelial cell autophagy, but the role of autophagy in regulating the expression of pro-inflammatory molecules has not been characterized. We hypothesized that autophagy facilitates expression of endothelial adhesion molecules. TNFα and IL-1β induced autophagy markers in human umbilical vein endothelial cells and inhibition of autophagy by 3-methyladenine (3-MA) blocked adhesion of Jurkat lymphocytes. Interestingly, 3-MA suppressed VCAM-1 but not ICAM-1 expression at 24 hours but not 6 hours. 3-MA suppressed VCAM-1 transcription and decreased nuclear NF-κB p65 level at 6 hours but not at 2 hours. Cytokines induced a biphasic degradation of IκBα and 3-MA selectively blocked the late-phase IκBα degradation. Our results suggest that cytokine-induced autophagy contributes to late-phase IκBα degradation, facilitates NF-κB nuclear translocation and VCAM-1 transcription for long-term VCAM-1 expression. With a cytokines array assay, we found that 3-MA also inhibited IP-10 expression. These findings provide new information about the role of endothelial autophagy in persistent expression of VCAM-1 and IP-10 which enhance lymphocyte recruitment and adhesion to endothelium.

Highlights

Pro-inflammatory mediators such as tumor necrosis factor α (TNFα) disrupt endothelial barrier function and induce expression of endothelial surface adhesion molecules leading to vascular and tissue inflammation and damage[1,2]
To determine whether cytokine-induced autophagy plays a role in regulating endothelial cell interaction with lymphocytes, we examined adhesion of Jurkat cells to cytokine-activated human umbilical vein endothelial cells (HUVECs)
IL-1β and TNFα increased Jurkat cells adhesion to HUVECs, which was significantly inhibited by 3-MA. These results suggest that cytokines induce autophagy via an mTOR-independent manner and cytokine-induced autophagy facilitates lymphocytes adhesion to activated endothelial cells

Summary

Introduction

Pro-inflammatory mediators such as tumor necrosis factor α (TNFα) disrupt endothelial barrier function and induce expression of endothelial surface adhesion molecules leading to vascular and tissue inflammation and damage[1,2]. We propose that TNFα- and IL-1β-induced autophagy is involved in late-phase IκBα degradation and thereby maintains long-term adhesion molecules expression in endothelial cells stimulated by pro-inflammatory cytokines. To test this hypothesis, we investigated TNFα- and IL-1β-induced autophagy in human umbilical vein endothelial cells (HUVECs) and determined its impact on IκB degradation, VCAM-1/ ICAM-1 expression, cytokines release, and lymphocyte adhesion. Our results indicate that cytokine-induced autophagy mediates the late-phase IκBα degradation, thereby maintaining long-term VCAM-1 and IP-10 expression and facilitating lymphocyte adhesion to endothelial cells

Methods

Results

Conclusion