DUB activity of Endothelial A20 maintains and repairs endothelial barrier after inflammatory lung injury

Abstract

Vascular endothelial cadherin (VE‐cad) expression at endothelial adherens junctions (AJs) stabilizes endothelial barrier. Inflammatory mediators induced VE‐cad phosphorylation and ubiquitination promotes its degradation; which in turn destabilizes endothelial barrier to trigger vascular inflammatory responses. However, the intrinsic molecular mechanisms involved in maintaining the basal endothelial barrier stability and the repair of endothelial barrier after vascular injury are poorly understood. Here, we generated endothelial cell (EC)‐restricted Tnfaip3 (A20) knockout (A20ΔEC) mice and showed the pivotal role of the deubiquitinase (DUB) function of A20 in regulating the expression of VE‐cad at AJs. A20ΔEC mice failed to survive sub‐lethal dose of LPS challenge. Consistent with this observation, A20ΔEC mice displayed uncontrolled lung vascular leak and persistent PMN sequestration in lungs in response to LPS. In support of these findings, we observed markedly reduced VE‐cad expression in lungs of A20ΔEC mice. Liposome mediated in vivo delivery of WT‐A20 but not DUB‐inactive (C103A‐A20) mutant construct restored VE‐cad expression in lungs, suppressed LPS induced lung vascular leak and sequestration of PMNs in lungs of A20ΔEC mice. Further, A20 knockdown in human lung microvascular ECs resulted increased VE‐cad phosphorylation on Y685 and Y731, and loss VE‐cad expression at AJs. Forced expression of WT‐A20 but not DUB‐inactive mutant in ECs prevented VE‐cad ubiquitination and degradation. Since induced A20 expression promotes resolution of inflammation, we studied the mechanism of A20 induction in response to TLR4 activation in ECs. Here we observed that IRAK‐M‐mediated NF‐κB activation independent of TAK1 is essential for A20 expression in ECs. Importantly, silencing of IRAK‐M in mouse lung microvessels suppressed expression of A20 and VE‐cad and augmented LPS induced lung vascular inflammatory responses. These findings support that targeting endothelial‐A20 expression is a potential therapeutic strategy to restore endothelial barrier integrity in acute lung injury.Support or Funding InformationNational Institute of Health Grants R01 HL‐128539 and R01 GM‐117028This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.