title: Metalloproteinase processing of HBEGF is a proximal event in the response of human aortic endothelial cells to oxidized phospholipids.
abstract: OBJECTIVE
  Atherosclerosis is a chronic inflammatory disease initiated by monocyte recruitment and retention in the vessel wall. An important mediator of monocyte endothelial interaction is the chemokine interleukin (IL)-8. The oxidation products of phospholipids, including oxidized 1-palmitoyl-2-arachidonyl-sn-glycerol-3-phosphocholine (Ox-PAPC), accumulate in atherosclerotic lesions and strongly induce IL-8 in human aortic endothelial cells (HAECs). The goal of this study was to identify the proximal events leading to induction of IL-8 by Ox-PAPC in vascular endothelial cells.
  
  
  RESULTS
  In a systems genetics analysis of HAECs isolated from 96 different human donors, we showed that heparin-binding EGF-like growth factor (HBEGF) transcript levels are strongly correlated to IL-8 induction by Ox-PAPC. The silencing and overexpression of HBEGF in HAECs confirmed the role of HBEGF in regulating IL-8 expression. HBEGF has been shown to be stored in an inactive form and activation is dependent on processing by a dysintegrin and metalloproteinases (ADAM) to a form that can activate the epidermal growth factor (EGF) receptor. Ox-PAPC was shown to rapidly induce HBEGF processing and EGF receptor activation in HAECs. Using siRNA we identified 3 ADAMs that regulate IL-8 induction and directly demonstrated that Ox-PAPC increases ADAM activity in the cells using a substrate cleavage assay. We provide evidence for one mechanism of Ox-PAPC activation of ADAM involving covalent binding of Ox-PAPC to cysteine on ADAM. Free thiol cysteine analogs showed inhibition of IL-8 induction by Ox-PAPC, and both a cysteine analog and a cell surface thiol blocker strongly inhibited ADAM activity induction by Ox-PAPC. Using microarray analyses, we determined that this ADAM pathway may regulate at least 30% of genes induced by Ox-PAPC in HAECs.
  
  
  CONCLUSIONS
  This study is the first report demonstrating a role for the ADAM-HBEGF-EGF receptor axis in Ox-PAPC induction of IL-8 in HAECs. These studies highlight a role for specific ADAMs as initiators of Ox-PAPC action and provide evidence for a role of covalent interaction of Ox-PAPC in activation of ADAMs.
authors.affiliation: Department of Pathology, University of California-Los Angeles, Los Angeles, CA, USA.
authors.forename: Sangderk
authors.initials: S
authors.lastname: Lee
authors.forename: James R
authors.initials: JR
authors.lastname: Springstead
authors.forename: Brian W
authors.initials: BW
authors.lastname: Parks
authors.forename: Casey E
authors.initials: CE
authors.lastname: Romanoski
authors.forename: Roland
authors.initials: R
authors.lastname: Palvolgyi
authors.forename: Tiffany
authors.initials: T
authors.lastname: Ho
authors.forename: Phuc
authors.initials: P
authors.lastname: Nguyen
authors.forename: Aldons J
authors.initials: AJ
authors.lastname: Lusis
authors.forename: Judith A
authors.initials: JA
authors.lastname: Berliner
mesh_terms: D001013:Aorta, Thoracic / Q000378:metabolism / Q000473:pathology; D050197:Atherosclerosis / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics*; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D016209:Interleukin-8 / Q000096:biosynthesis; D045726:Metalloproteases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010743:Phospholipids / Q000378:metabolism*; D040081:Protein Array Analysis; D011956:Receptors, Cell Surface; D015398:Signal Transduction
chemical_list: C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D016209:Interleukin-8; D010743:Phospholipids; D011956:Receptors, Cell Surface; D004247:DNA; D045726:Metalloproteases