Thrombin and activated protein C inhibit the expression of secretory group IIA phospholipase A(2) in the TNF-alpha-activated endothelial cells by EPCR and PAR-1 dependent mechanisms.

Abstract

INTRODUCTION:

Thrombin and tumor necrosis factor (TNF)-alpha up-regulate the expression of proinflammatory molecules in human umbilical vein endothelial cells (HUVECs). However, activated protein C (APC) down-regulates the expression of the same molecules. The expression level of secretory group IIA phospholipase A(2) (sPLA(2)-IIA) is known to be elevated in inflammatory disorders including in sepsis. Here, we investigated the effects of APC and thrombin on the expression of sPLA(2)-IIA and extracellular signal-regulated kinase (ERK) in HUVECs.

MATERIALS AND METHODS:

The expression level of sPLA(2)-IIA was quantitatively measured by an enzyme-linked-immunosorbent-assay following stimulation of HUVECs with either thrombin or TNF-alpha in the absence and presence of the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor LY294002 and the cholesterol-depleting drug methyl-beta-cyclodextrin (MbetaCD).

RESULTS AND CONCLUSIONS:

Thrombin had no effect on the expression of sPLA(2)-IIA in HUVECs, however, TNF-alpha potently induced its expression. The prior treatment of cells with APC inhibited expression of sPLA(2)-IIA through the EPCR-dependent cleavage of PAR-1. Further studies revealed that if HUVECs were pretreated with the zymogen protein C to occupy EPCR, thrombin also inhibited the TNF-alpha-mediated expression of sPLA(2)-IIA through the cleavage of PAR-1. The EPCR-dependent cleavage of PAR-1 by both APC and thrombin increased the phosphorylation of ERK 1/2. Pretreatment of cells with either LY294002 or MbetaCD abolished the inhibitory activity of both APC and thrombin against sPLA(2)-IIA expression, suggesting that the protein C occupancy of EPCR confers a PI3-kinase dependent protective activity for thrombin such that its cleavage of the lipid-raft localized PAR-1 inhibits the TNF-alpha-mediated expression of sPLA(2)-IIA in HUVECs.

• Authors: Jong-Sup Bae, Alireza R Rezaie
• Journal: Thrombosis research (Thromb Res) Vol. 125 Issue 1 Pg. e9-e15 (Jan 2010) ISSN: 1879-2472 [Electronic] United States
• PMID: 19683795 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2009 Elsevier Ltd. All rights reserved.

Chemical References

• Antigens, CD
• Endothelial Protein C Receptor
• PROCR protein, human
• Protein C
• Receptor, PAR-1
• Receptors, Cell Surface
• Tumor Necrosis Factor-alpha
• Group II Phospholipases A2
• Thrombin

Topics

• Antigens, CD (metabolism)
• Cells, Cultured
• Endothelial Cells (drug effects, metabolism)
• Endothelial Protein C Receptor
• Endothelium, Vascular (metabolism)
• Enzyme Activation
• Group II Phospholipases A2 (antagonists & inhibitors)
• Humans
• Protein C (metabolism, pharmacology)
• Receptor, PAR-1 (metabolism)
• Receptors, Cell Surface (metabolism)
• Thrombin (metabolism, pharmacology)
• Tumor Necrosis Factor-alpha (pharmacology)
• Umbilical Veins (metabolism)