title: Ox-PAPC activation of PMET system increases expression of heme oxygenase-1 in human aortic endothelial cell.
abstract: Oxidized-1-palmitoyl-2-arachidonyl-sn-glycerol-3-phosphocholine (Ox-PAPC) has been demonstrated to accumulate in atherosclerotic lesions and regulates expression of more than 1,000 genes in human aortic endothelial cell (HAEC). Among the most highly induced is heme oxygenase-1 (HO-1), a cell-protective antioxidant enzyme, which is sensitively induced by oxidative stress. To identify the pathway by which Ox-PAPC induces HO-1, we focused on the plasma membrane electron transport (PMET) complex, which contains ecto-NADH oxidase 1 (eNOX1) and NADPH:quinone oxidoreductase 1 (NQO1) and affects cellular redox status by regulating levels of NAD(P)H. We demonstrated that Ox-PAPC and its active components stimulated electron transfer through the PMET complex in HAECs from inside to outside [as determined by extracellular 2-(4-iodophenyl)-3-(44-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1) reduction] and from outside to inside of the cell (as determined by intracellular NBT reduction). Chemical inhibitors of PMET system and siRNAs to PMET components (NQO1 and eNOX1) significantly decreased HO-1 induction by Ox-PAPC. We present evidence that Ox-PAPC activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in HAEC plays an important role in the induction of HO-1 and PMET inhibitors blocked Nrf2 activation by Ox-PAPC. We hypothesized that PMET activation by Ox-PAPC causes intracellular NAD(P)H depletion, which leads to the increased oxidative stress and HO-1 induction. Supporting this hypothesis, cotreatment of cells with exogenous NAD(P)H and Ox-PAPC significantly decreased oxidative stress and HO-1 induction by Ox-PAPC. Taken together, we demonstrated that the PMET system in HAEC plays an important role in the regulation of cellular redox status and HO-1 expression by Ox-PAPC.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of California-Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Sangderk
authors.initials: S
authors.lastname: Lee
authors.forename: Rongsong
authors.initials: R
authors.lastname: Li
authors.forename: Brandon
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authors.lastname: Kim
authors.forename: Roland
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authors.lastname: Palvolgyi
authors.forename: Tiffany
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authors.lastname: Ho
authors.forename: Qian-Zhou
authors.initials: QZ
authors.lastname: Yang
authors.forename: Jason
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authors.lastname: Xu
authors.forename: Wan Lam
authors.initials: WL
authors.lastname: Szeto
authors.forename: Henry
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authors.lastname: Honda
authors.forename: Judith A
authors.initials: JA
authors.lastname: Berliner