Lipopolysaccharide Induces the Antiapoptotic Molecules, A1 and A20, in Microvascular Endothelial Cells

Abstract

The effect of lipopolysaccharide (LPS) on endothelial cells is a key component of the inflammatory response seen in Gram-negative sepsis. LPS does not cause death of cultured human endothelial cells. However, when the expression of new proteins is inhibited by cycloheximide, microvascular endothelial cells in culture undergo apoptosis. This finding suggests that LPS induces apoptotic and antiapoptotic pathways, with the antiapoptotic response being dependent on the synthesis of new proteins. Concurrent activation of apoptotic and antiapoptotic pathways has previously been documented for tumor necrosis factor (TNF). In the case of TNF, the antiapoptotic signal has been attributed to at least two cytoprotective proteins: the Bcl-2 homologue, A1, and the zinc-finger protein, A20. In this study, we demonstrate that both these molecules are induced in microvascular endothelial cells by LPS. Enforced overexpression of either A1 or A20 inhibits LPS and cycloheximide-initiated apoptosis. Induction of A1 and A20 does not require synthesis of intermediary proteins, but is dependent on the presence of soluble CD14. In addition, we show that inhibition of signaling by the transcription factor, NF-κB, blocks accumulation of A1 and A20 mRNA. Taken together, our findings suggest that LPS directly induces expression of the cytoprotective proteins, A1 and A20, via a CD14-dependent pathway requiring activation of NF-κB. © 1998 by The American Society of Hematology.

Donor Heart Treatment With COMP-Ang1 Limits Ischemia-Reperfusion Injury and Rejection of Cardiac Allografts

“…Ang1 directly promotes endothelial anti‐apoptotic and anti‐inflammatory effects via the A20‐binding inhibitor of NF‐κB activation (ABIN)‐2 . A20 inhibits TNF‐α and LPS‐mediated EC apoptosis and reduces NF‐κB expression, and ABIN‐2 mediates these effects via Tie2 in an Ang1‐dependent fashion . Furthermore, we observed decreased mRNA expression and immunoreactivity of danger signals HAS1 and TLR4 and dendritic cell activation markers CD80 and CD83 in the COMP‐Ang1–treated allografts.…”

Caspase-3 is activated and rapidly released from human umbilical vein endothelial cells in response to lipopolysaccharide

“…Various methods were employed to measure endothelial injury in these studies. For example, Hu et al examined cell viability by MTT assay [30] and Bannerman et al examined caspase activities [24]. In the present study, we systematically evaluated endothelial injury with the MTS viability assay, LDH release (cytotoxicity) and caspase-3/7 activity both intracellularly and in culture supernatants in the presence and absence of a protein synthesis inhibitor, CHX.…”

“…ACCEPTED MANUSCRIPT [28][29], most studies using human endothelial cells showed that these cells require protein synthesis inhibitors such as CHX for the induction of apoptosis in response to LPS [24,30]. Various methods were employed to measure endothelial injury in these studies.…”

Heterogeneity in Endothelial Responsiveness to Cytokines, Molecular Causes, and Pharmacological Consequences

“…[61][62][63][64][65] Induced expression of FLICE-like inhibitory protein (FLIP) and the antiapoptotic proteins A1 and A20 have a role in protecting endothelial cells from LPS-induced apoptosis as well as in creating a suppressive effect on LPS-induced NFkB activation. 66,67 For an overview on the more detailed molecular interactions of these signaling pathways, the reader is referred to two excellent reviews. 61,65 The functional consequences of LPS-mediated endothelial cell activation are widespread and include engagement in leukocyte recruitment, expression of procoagulant activity, and endothelial sprouting.…”