Published online before print June 5, 2008, doi: 10.1161/CIRCRESAHA.108.176883
© 2008 American Heart Association, Inc.
UltraRapid Communication |
Nrf2 Regulates Antioxidant Gene Expression Evoked by Oxidized Phospholipids in Endothelial Cells and Murine Arteries In Vivo
From the Department of Biotechnology and Molecular Medicine (H.-K.J., E.K., M.I., A.M.K., H.H., S.E.H., S.J., S.T., S.Y.-H., A.-L.L.) and Department of Neurobiology (G.G., J.K.), A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Finland; Institute of Biomedicine, Medical Biochemistry (H.M.), Faculty of Medicine, University of Kuopio, Finland; Center for Tsukuba Advanced Research Alliance and Japan Science and Technology Agency–Exploratory Research for Advanced Technology Environmental Response Project (M.Y.), University of Tsukuba, Japan; Department of Medical Biochemistry (M.Y.), Tohoku University Graduate School of Medicine, Sendai, Japan; Department of Vascular Biology and Thrombosis Research (O.O., T.A., V.N.B.), Medical University of Vienna, Austria; and Gene Therapy Unit (S.Y.-H.), Kuopio University Hospital, Kuopio, Finland.
Correspondence to Anna-Liisa Levonen, MD, PhD, Department of Biotechnology and Molecular Medicine, A. I. Virtanen Institute, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland. E-mail Anna-Liisa.Levonen{at}uku.fi
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Besides their well-characterized proinflammatory and proatherogenic effects, oxidized phospholipids, such as oxPAPC (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphocholine) have been shown to have beneficial responses in vascular cells via induction of antioxidant enzymes such as heme oxygenase-1. We therefore hypothesized that oxPAPC could evoke a general cytoprotective response via activation of antioxidative transcription factor Nrf2. Here, we show that oxPAPC increases nuclear accumulation of Nrf2. Using the small interfering RNA approach, we demonstrate that Nrf2 is critical in mediating the induction of glutamate-cysteine ligase modifier subunit (GCLM) and NAD(P)H quinone oxidoreductase-1 (NQO1) by oxPAPC in human endothelial cells, whereas the contribution to the induction of heme oxygenase-1 was less significant. The induction of GCLM and NQO1 was attenuated by reduction of electrophilic groups with sodium borohydrate, as well as treatment with thiol antioxidant N-acetylcysteine, suggesting that the thiol reactivity of oxPAPC is largely mediating its effect on Nrf2-responsive genes. Moreover, we show that oxidized phospholipid having a highly electrophilic isoprostane ring in its sn-2 position is a potent inducer of Nrf2 target genes. Finally, we demonstrate that the oxPAPC-inducible expression of heme oxygenase-1, GCLM, and NQO1 is lower in Nrf2-null than wild-type mouse carotid arteries in vivo. We suggest that the activation of Nrf2 by oxidized phospholipids provides a mechanism by which their deleterious effects are limited in the vasculature.
Key Words: antioxidant response element • electrophile response element • Nrf2 • oxidized phospholipids
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Oxidative modification of low-density lipoprotein (LDL) has been implicated to play a role in the atherogenic process. Oxidized phospholipids (oxPLs) present in minimally modified LDL, such as oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphocholine (oxPAPC), contribute to the chronic inflammation characteristic of atherosclerosis via, eg, upregulation of adhesion molecules and inflammatory cytokines and chemokines, thus promoting the recruitment of inflammatory cells to the vessel wall.1,2 Moreover, oxPLs derived from PAPC, as well as from 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC), serve as ligands for the scavenger receptor CD36, thereby enhancing macrophage cholesterol accumulation and foam cell formation.3,4
Despite the well-characterized proinflammatory and proatherogenic effects of oxPAPC in vascular cells, it has also been shown to have antiinflammatory actions. In endothelial cells, oxPAPC induces heme oxygenase (HO)-1,5–7 an antiatherogenic protein.8 OxPAPC also increases the amount of glutathione, an important thiol antioxidant, in endothelial cells.9 Interestingly, both modifier and catalytic subunits of glutamate-cysteine ligase (GCLM and GCLC, respectively), the rate-limiting enzyme of glutathione synthesis, have recently been shown to be upregulated by oxPAPC in a microarray analysis of human aortic endothelial cells.10 A common feature of GCLM, GCLC, and HO-1 is that all of these genes have a well-characterized antioxidant response element (ARE), also called electrophile response element, sequence in their 5' flanking sequences.11 The ARE sequence is a regulatory element found in the promoters of a number of antioxidant and phase II detoxification enzymes, and it binds the transcription factor Nrf2, which has recently been reported to mediate the induction of OKL38 gene by oxPAPC.12
The mechanism of Nrf2-dependent signaling bears similarities with other environmental defense systems, ie, nuclear factor 
B–mediated inflammatory and hypoxia inducible factor–mediated hypoxic responses.13 Under basal conditions, Nrf2-dependent transcription is repressed by its negative regulator Keap1, which functions as an adaptor for Cul3-based E3 ligase to facilitate proteasomal degradation of Nrf2. When cells are exposed to oxidative stress or electrophiles, Nrf2 accumulates in the nucleus and drives the expression of its target genes. Although it is evident that Keap1 is a critical negative regulator of Nrf2 signaling and a direct target for Nrf2-activating electrophiles,14–16 there are a number of complementary signaling pathways, such as those mediated by protein kinases,17 contributing to the activation.
Based on previous findings, we hypothesized that oxPLs can trigger a stress response via Nrf2 in endothelial cells. The aim of our study was therefore to assess the role of Nrf2 in mediating the induction of GCLM, HO-1, and NAD(P)H quinone oxidoreductase-1, another Nrf2-dependent gene important for endothelial antioxidant protection.18,19 Moreover, the molecular characteristics of Nrf2-activating oxPLs was examined. Finally, using topical application of oxPAPC to the carotid arteries of either wild-type (WT) or Nrf2–/– animals, we studied the role of Nrf2 in mediating the induction of antioxidant genes in vivo.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Details on phospholipids and other reagents, cell culture, cloning of the plasmids, transfection of cells with plasmids or small interfering (si)RNA, real-time quantitative PCR analysis, Western blotting and densitometric quantification, chromatin immunoprecipitation (ChIP), luciferase reporter assay, surgical application of oxPAPC to mouse carotid arteries, immunohistochemistry, and statistical analyses are provided in the expanded Materials and Methods section in the online data supplement, available at http://circres.ahajournals.org. All animal procedures were approved by the Experimental Animal Committee of the University of Kuopio.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
OxPAPC Activates Nrf2 and Induces HO-1, GCLM, and NQO1
On activation, Nrf2 protein accumulates in the nucleus, which subsequently drives the expression of Nrf2 target genes. We therefore first examined the effect of oxPAPC on nuclear and cytoplasmic content of Nrf2 protein, as well as the expression of HO-1, GCLM, and NQO1, well-characterized Nrf2 target genes. OxPAPC at the concentration of 50 µg/mL increased Nrf2 protein assessed by Western blots in nuclear fractions (Figure 1A). Treatment of human umbilical vein cells (HUVECs) with 0 to 75 µg/mL oxPAPC increased HO-1, GCLM, and NQO1 mRNA and protein concentration dependently (Figure 1B). The fold induction of HO-1 mRNA was notably higher than the other genes, largely because of very low basal expression. The induction of HO-1 by oxPAPC was rapid and preceded the induction of both GCLM and NQO1 (Figure 1C).
|
Knockdown of Nrf2 Expression by siRNA Inhibits the Induction of HO-1, GCLM, and NQO1 by OxPAPC
To assess as to whether the induction of HO-1, GCLM, and NQO1 is Nrf2-dependent, a specific siRNA against Nrf2 was used. Transfection with Nrf2 siRNA caused a significant inhibition of both Nrf2 mRNA and protein expression in comparison with nonspecific control siRNA (Figure 2A and 2B). Densitometric assessment of nuclear Nrf2 protein content relative to LaminB1 revealed 
90% reduction of Nrf2 protein in cells transfected with Nrf2-siRNA and treated with oxPAPC for 4 hours, in comparison with control siRNA-transfected, oxPAPC-treated cells (Figure 2B). Both basal and the oxPAPC-inducible mRNA expression of GCLM and NQO1 was markedly downregulated by Nrf2 siRNA. However, although the expression of HO-1 mRNA was significantly inhibited by Nrf2 siRNA, the reduction was only 30%, suggesting that other, redundant pathways in large part mediate the induction by oxPAPC. This notion was further supported by the densitometric analysis of the Western blot data, which shows that oxPAPC-induced expression of GCLM and NQO1 protein expression normalized to β-actin was significantly attenuated by Nrf2-siRNA, whereas HO-1 expression showed a trend toward lower expression, yet did not reach statistical significance (Figure 2C).
|
OxPAPC Increases the ARE-Driven Gene Expression and Induces Binding of Nrf2 to the ARE Elements of NQO1 and HO-1 Promoter Regions
Nrf2 exerts its effects through binding to the ARE element of the target gene promoter regions. To study whether oxPAPC activates ARE-driven transcription, the luciferase reporter vector containing the ARE element from the human NQO1 promoter was used. A concentration of 50 µg/mL oxPAPC increased ARE-driven transcription assessed by increased luciferase activity, whereas in the construct in which the consensus ARE element was mutated, both basal and inducible activity was attenuated (Figure 3A). On exposure to oxPAPC, there was minor residual activation of the empty pGL3-basic vector and the vector having the NQO1 core ARE mutated. The vector backbone of pGL3-luciferase expression vector has several putative consensus binding sites for transcription factors, which may be responsive to oxPAPC. For example, it contains a concensus activator protein-1 site, which may impact the activity of the construct, because activator protein-1 has been shown to be activated by oxPAPC.20 However, the residual activity was very low and the direct binding of Nrf2 to the NQO1 promoter on exposure to oxPAPC was verified by ChIP assay (Figure 3B). Treatment of HUVECs with oxPAPC also increased the binding of Nrf2 to the distal enhancer region of HO-1 gene containing multiple AREs (Figure 3B). These results demonstrate that oxPAPC activates ARE and increases the binding of Nrf2 to both NQO1 and HO-1 ARE elements.
|
Characterization of the Lipid Species Inducing Antioxidant Enzymes
As shown in Figure 2, the induction of GCLM and NQO1 by oxPAPC was critically dependent on Nrf2, indicating that the expression of these genes could be used as a readout for the Nrf2-activating effects of different classes of oxPLs. To study the effect of polar head groups in sn-3 position on Nrf2 activation, cells were stimulated by oxPLs containing identical sn-1 and sn-2 residues (palmitoyl and arachidonoyl, respectively) but different polar head groups (for a structure of PAPC, see Figure I in the online data supplement). Replacement of oxPAPC with oxidized phosphatidylglycerol, phosphatidic acid, phosphatidylethanolamine, or phosphatidylserine yielded similar upregulation of GCLM and NQO1 mRNA (Figure 4A), suggesting that the polar head group in sn-3 residue does not play an important role in activity. Next, the significance of the sn-2 residue was examined. We found that the presence of oxidized sn-2 residue was an absolute prerequisite for activation of GCLM and NQO1 genes because neither unoxidized phospholipids nor 1-palmitoyl-2-hydroxy-sn-3-glycero-phosphocholine (lysoPC), in which only a hydroxyl group in sn-2 position is present, were active (Figure 4A and 4B).
|
Oxidation of PAPC yields phospholipids containing oxidatively fragmented sn-2 residues such as 1-palmitoyl-2-(5-oxovaleroyl)-sn-3-glycero-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-3-glycero-phosphocholine (PGPC) (supplemental Figure I).2 We next examined the effect of these on the mRNA expression of GCLM and NQO1. Exposure of HUVECs to POVPC or PGPC did not increase the expression of either gene, indicating that these are not the species responsible for Nrf2 activation (Figure 4C). Because POVPC contains 
-terminal aldehyde group, these results also show that the presence of an electrophilic group alone is not sufficient for the activity. OxPAPC-containing esterified epoxy isoprostanes (1-palmitoyl-2-5,6-epoxy isoprostane E2-sn-3-glycero-phosphocholine [PEIPC or isoprostane-PC]) (supplemental Figure I) were previously characterized as biologically active molecules.21,22 We found that HPLC fraction enriched in isoprostane-PC strongly upregulated GCLM and NQO1 genes (Figure 4D). To test whether the isoprostane ring structure is an absolute determinant of the activity, we tested the effect of oxidized palmitoyl-linoleoyl-phosphatidylcholine (oxPLPC). Linoleic acid in the sn-2 position contains only 2 double bonds and therefore cannot form prostanoids.23 Nevertheless, oxPLPC stimulated the expression of GCLM and NQO1 genes almost as efficiently as oxPAPC (Figure 4E). In addition, GCLM was upregulated by PAPC-hydroperoxide (PAPC-OOH) (Figure 4F). The effect was blunted by the reduction of hydroperoxide to hydroxide (PAPC-OH) by triphenylphosphine (Figure 4F and supplemental Figure II). In summary, we found relaxed specificity with respect to the polar head groups, demonstrated critical importance of oxidized sn-2 residue, and characterized hydroperoxide- and isoprostane-containing oxPLs as molecular species capable of inducing GCLM and NQO1 genes.
To test the role of electrophilic groups present in oxPAPC, these were reduced by sodium borohydride (NaBH4).22 Treatment with NaBH4 reduces aldehyde, keto, epoxy, and peroxyl groups into respective hydroxyl groups.22 The positive ion electrospray ionization/mass spectrometry analysis of oxPAPC before and after NaBH4 showed that signals at m/z 594.5 and m/z 828.6, (corresponding to POVPC and isoprostane-PC, respectively) were diminished and new signals at m/z 596.4 and m/z 832.6 were detected, indicating the reduction of one functional group in POVPC and 2 in isoprostane-PC (supplemental Figure III).2,22 Treatment of oxPAPC with NaBH4 partially suppressed its ability to induce GCLM and NQO1 in HUVECs (Figure 5A). Moreover, coincubation with nucleophilic thiol antioxidants N-acetylcysteine (NAC) and glutathione reduced the induction of these genes as well as HO-1 (Figure 5B and supplemental Figure IV). We also examined the effect of NAC on the induction of Nrf2 target genes by PAPCOOH and isoprostane-PC. Incubation with NAC inhibited the induction of HO-1, GCLM, and NQO1 by both species (Figure 5C and 5D). Moreover, treatment with NaBH4 almost completely abolished the effect of isoprostane-PC on the expression of these genes (Figure 5D). To conclude, these data indicate that the electrophilic character of oxPAPC and its active components are largely mediating the effect on Nrf2-responsive genes, but additional mechanisms may be required for maximal induction of these genes by oxPLs.
|
OxPAPC Induces HO-1, GCLM, and NQO1 Through an Nrf2-Dependent Mechanism in Murine Arteries In Vivo
Finally, we wanted to examine the role of Nrf2 in mediating the expression of HO-1, GCLM, and NQO1 in vivo. To this end, oxPAPC in pluronic gel was applied to the adventitial side of surgically exposed carotid arteries of either WT C57BL/6 controls or Nrf2-KO mice as in.24 The concentration used corresponds to concentrations of isoprostane-PC and other bioactive phospholipids that are lower than those found in the aortas of rabbits fed the atherogenic diet.24,25 Mouse carotid arteries consist of only 4 to 5 cell layers, allowing penetration of oxPAPC through the vessel wall. We first studied the mRNA expression of HO-1, GCLM, and NQO1 in mouse carotid arteries using quantitative real-time PCR. After 6 hours of treatment with oxPAPC, all 3 genes were significantly upregulated in WT mouse carotid arteries in comparison with controls treated with pluronic gel only (Figure 6A). The induction was completely abolished in the arteries of Nrf2-KO animals (Figure 6A). In addition, the basal expression of NQO1 was also significantly lower in Nrf2-KO mice compared with WT controls.
|
We next examined the HO-1 and NQO1 protein expression in mouse carotid arteries in WT and Nrf2-KO mice using immunohistochemistry. Immunohistochemical analysis of mouse carotid arteries exposed to oxPAPC for 24 hours showed increased HO-1 expression in oxPAPC-treated arteries in WT but not in Nrf2-KO arteries (Figure 6B). HO-1–positive cells were localized mainly in the adventitia of the vessels (Figure 6B). The expression NQO1 protein was more uniformly increased throughout the vessel wall in oxPAPC-treated WT carotid arteries, with increased positive staining in the adventitial and medial layers and especially in the endothelial layer (Figure 6C). In the Nrf2-KO mouse arteries, exposure to oxPAPC did not increase NQO1 positive staining (Figure 6C).
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
There are a number of reports showing in vitro that Nrf2 could have antiinflammatory effects in vascular cells. In cultured endothelial cells, Nrf2 is activated by shear stress, a potent antiinflammatory force.18,19 Overexpression of Nrf2 downregulates the tumor necrosis factor-
–induced transcriptional increase in vascular cell adhesion molecule-1 expression and inhibits monocyte adhesion to the endothelium.18,26 Furthermore, Nrf2 has been shown to mediate adaptive augmentation of antioxidant defenses of vascular cells on exposure to a variety of lipid oxidation products such as oxidized LDL, a lipid-derived aldehyde 4-hydroxynonenal, or cyclopentenone prostaglandins and isoprostanes.9,15,27,28 Herein, we expand these previous studies to show that also oxPAPC can evoke a concerted Nrf2-mediated response. Moreover, we show in vivo using WT and Nrf2-null mice that oxPAPC upregulates the expression of HO-1, GCLM, and NQO1 mRNA and HO-1 and NQO1 protein in mouse carotid arteries in WT but not in Nrf2-KO mice, demonstrating the role of Nrf2 in regulating these genes also in intact vessels. Inasmuch as we have recently shown in rabbit balloon injury model that adenoviral Nrf2 gene transfer can attenuate injury-induced vascular inflammation, as well as inhibit the accumulation of oxidized LDL in the vessel wall,29 it is conceivable that the Nrf2 response provides a mechanism by which the deleterious effects of oxPAPC are limited.
In the present study, the induction of HO-1 in vivo in mouse carotid vessels appeared to be critically dependent on Nrf2, whereas in human endothelial cells, suppression of Nrf2 expression by siRNA had a markedly smaller impact on HO-1 expression than on the other target genes GCLM and NQO1. Although both genes have been shown to contain the 2 enhancer regions in their promoters with multiple ARE binding sites, this does not unequivocally mean that the regulation of mouse and human genes is identical. Although our ChIP results clearly indicate that Nrf2 binding is increased in distal enhancer region in the HO-1 gene on oxPAPC exposure, it is evident that other, redundant pathways are involved in HO-1 induction. For example, in previous studies, cAMP-responsive element-binding protein,6 was shown to be involved in the induction of HO-1 by oxPAPC in human endothelial cells. Also a number of other transcriptional regulators and signaling pathways, such as nuclear factor B and PPRE (peroxisome proliferator-activated receptor response element), contribute to the regulation of HO-1,7,8 highlighting the complexity of HO-1 regulation in different cell types and by different stimuli. It is also noteworthy that in our study, the induction of HO-1 in vivo is markedly lower than the up to 100-fold induction achieved in vitro, making it likely that in the latter case redundant pathways contributing to the activation are needed for a sufficient response.
At present, the cellular receptor mediating the effect of oxPAPC on Nrf2 activation remains unclear. It also remains an open question whether the Nrf2 activating capacity of oxPLs can be modified by phospholipases, eg, by phospholipase A2 catalyzing the cleavage at the sn-2 position, shown to reduce the proinflammatory activity of oxPAPC.25 It is possible that intact electrophilic oxPLs could directly bind to intracellular Keap1, because phospholipids can be taken up by the cell by transbilayer movement,30,31 or by receptor-mediated mechanisms.32 Keap1 has highly reactive cysteine residues, which can be modified by direct alkylation by electrophiles, including 15-deoxy-
12,14-prostaglandin J2.15,19 Interestingly, oxPAPC is known to contain esterified cyclopentenone isoprostanes.22 Also, it has recently been demonstrated that oxidized phospholipids can have intracellular targets33 and that they can covalently bind to intracellular signaling proteins, such as H-Ras.34 However, oxPAPC may also have targets at the cell surface which could evoke the Nrf2 response. Several cell surface receptors have been proposed to be receptors for oxPLs, including PAF-receptor,35 lysophospholipid receptors such as G2A,36 Toll-like receptor 4,37 and prostaglandin E2 receptor subtype 2.38 However, the structure–function relationship found in our experiments does not support the involvement of any of these in Nrf2 activation.
It has been proposed that exposure to oxPAPC leads to activation of NAD(P)H oxidase and production of reactive oxygen species in endothelial cells, mediating downstream effects on gene expression.12,39 Regarding the role of NAD(P)H oxidase in Nrf2 activation, there are a few reports showing a connection.40–42 Unfortunately, these reports use diphenyleneiodonium to inhibit NAD(P)H oxidase. This compound is not a specific NAD(P)H oxidase inhibitor but inhibits flavoenzymes in general, some of which (eg, NQO1, glutathione reductase) are antioxidant enzymes and Nrf2 target genes. Therefore the effects of diphenyleneiodonium are difficult to interpret. We have done experiments in which we look at the effect of NAD(P)H inhibitor apocynin, as well as siRNA specific to Nox4, the major component of endothelial NADPH oxidase,43 which has also been reported to be responsive to oxPAPC.39 Neither apocynin nor Nox4 siRNA had any impact on Nrf2 target gene expression (results not shown). These results support the notion that secondary ROS production by NAD(P)H oxidase is not necessary for Nrf2 activation.
In summary, our study has identified molecular mechanisms by which oxPLs induce antioxidant genes and shows the critical dependence on Nrf2 in the induction of HO-1, GCLM, and NQO1 expression by oxPAPC in vivo. We postulate that the activation of Nrf2 by oxPLs provides a mechanism by which their proatherogenic effects are limited in the vessel wall.
|
Acknowledgments |
|---|
Sources of Funding
This study was supported by the grants from the Academy of Finland, the Sigrid Juselius Foundation, the Finnish Foundation for Cardiovascular Research, the European Vascular Genomics Network (EVGN grant LSHM-CT-2003-503254), Fonds zur Förderung wissenschaftlicher Forschung (P18232-B11, P20801-B11), and Österreichischer Forschungsförderungsgesellschaft (project 815445).
Disclosures
None.
|
Footnotes |
|---|
*Both authors contributed equally to this work.
Original received July 10, 2007; resubmission received April 7, 2008; revised resubmission received May 23, 2008; accepted May 28, 2008.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1. Berliner JA, Watson AD. A role for oxidized phospholipids in atherosclerosis. N Engl J Med. 2005; 353: 9–11.
2. Watson AD, Leitinger N, Navab M, Faull KF, Horkko S, Witztum JL, Palinski W, Schwenke D, Salomon RG, Sha W, Subbanagounder G, Fogelman AM, Berliner JA. Structural identification by mass spectrometry of oxidized phospholipids in minimally oxidized low density lipoprotein that induce monocyte/endothelial interactions and evidence for their presence in vivo. J Biol Chem. 1997; 272: 13597–13607.
3. Podrez EA, Poliakov E, Shen Z, Zhang R, Deng Y, Sun M, Finton PJ, Shan L, Gugiu B, Fox PL, Hoff HF, Salomon RG, Hazen SL. Identification of a novel family of oxidized phospholipids that serve as ligands for the macrophage scavenger receptor CD36. J Biol Chem. 2002; 277: 38503–38516.
4. Podrez EA, Poliakov E, Shen Z, Zhang R, Deng Y, Sun M, Finton PJ, Shan L, Febbraio M, Hajjar DP, Silverstein RL, Hoff HF, Salomon RG, Hazen SL. A novel family of atherogenic oxidized phospholipids promotes macrophage foam cell formation via the scavenger receptor CD36 and is enriched in atherosclerotic lesions. J Biol Chem. 2002; 277: 38517–38523.
5. Ishikawa K, Navab M, Leitinger N, Fogelman AM, Lusis AJ. Induction of heme oxygenase-1 inhibits the monocyte transmigration induced by mildly oxidized LDL. J Clin Invest. 1997; 100: 1209–1216.[Medline] [Order article via Infotrieve]
6. Kronke G, Bochkov VN, Huber J, Gruber F, Bluml S, Furnkranz A, Kadl A, Binder BR, Leitinger N. Oxidized phospholipids induce expression of human heme oxygenase-1 involving activation of cAMP-responsive element-binding protein. J Biol Chem. 2003; 278: 51006–51014.
7. Kronke G, Kadl A, Ikonomu E, Bluml S, Furnkranz A, Sarembock IJ, Bochkov VN, Exner M, Binder BR, Leitinger N. Expression of heme oxygenase-1 in human vascular cells is regulated by peroxisome proliferator-activated receptors. Arterioscler Thromb Vasc Biol. 2007; 27: 1276–1282.
8. Stocker R, Perrella MA. Heme oxygenase-1: a novel drug target for atherosclerotic diseases? Circulation. 2006; 114: 2178–2189.
9. Moellering DR, Levonen AL, Go YM, Patel RP, Dickinson DA, Forman HJ, Darley-Usmar VM. Induction of glutathione synthesis by oxidized low-density lipoprotein and 1-palmitoyl-2-arachidonyl phosphatidylcholine: protection against quinone-mediated oxidative stress. Biochem J. 2002; 362: 51–59.[CrossRef][Medline] [Order article via Infotrieve]
10. Gargalovic PS, Imura M, Zhang B, Gharavi NM, Clark MJ, Pagnon J, Yang WP, He A, Truong A, Patel S, Nelson SF, Horvath S, Berliner JA, Kirchgessner TG, Lusis AJ. Identification of inflammatory gene modules based on variations of human endothelial cell responses to oxidized lipids. Proc Natl Acad Sci U S A. 2006; 103: 12741–12746.
11. Motohashi H, Yamamoto M. Nrf2-Keap1 defines a physiologically important stress response mechanism. Trends Mol Med. 2004; 10: 549–557.[CrossRef][Medline] [Order article via Infotrieve]
12. Li R, Chen W, Yanes R, Lee S, Berliner JA. OKL38 is an oxidative stress response gene stimulated by oxidized phospholipids. J Lipid Res. 2007; 48: 709–715.
13. Tong KI, Kobayashi A, Katsuoka F, Yamamoto M. Two-site substrate recognition model for the Keap1-Nrf2 system: a hinge and latch mechanism. Biol Chem. 2006; 387: 1311–1320.[CrossRef][Medline] [Order article via Infotrieve]
14. Kobayashi A, Kang MI, Watai Y, Tong KI, Shibata T, Uchida K, Yamamoto M. Oxidative and electrophilic stresses activate Nrf2 through inhibition of ubiquitination activity of Keap1. Mol Cell Biol. 2006; 26: 221–229.
15. Levonen AL, Landar A, Ramachandran A, Ceaser EK, Dickinson DA, Zanoni G, Morrow JD, Darley-Usmar VM. Cellular mechanisms of redox cell signalling: role of cysteine modification in controlling antioxidant defences in response to electrophilic lipid oxidation products. Biochem J. 2004; 378: 373–382.[CrossRef][Medline] [Order article via Infotrieve]
16. Wakabayashi N, Dinkova-Kostova AT, Holtzclaw WD, Kang MI, Kobayashi A, Yamamoto M, Kensler TW, Talalay P. Protection against electrophile and oxidant stress by induction of the phase 2 response: fate of cysteines of the Keap1 sensor modified by inducers. Proc Natl Acad Sci U S A. 2004; 101: 2040–2045.
17. Chen C, Kong AN. Dietary chemopreventive compounds and ARE/EpRE signaling. Free Radic Biol Med. 2004; 36: 1505–1516.[CrossRef][Medline] [Order article via Infotrieve]
18. Chen XL, Varner SE, Rao AS, Grey JY, Thomas S, Cook CK, Wasserman MA, Medford RM, Jaiswal AK, Kunsch C. Laminar flow induction of antioxidant response element-mediated genes in endothelial cells. A novel anti-inflammatory mechanism. J Biol Chem. 2003; 278: 703–711.
19. Hosoya T, Maruyama A, Kang MI, Kawatani Y, Shibata T, Uchida K, Warabi E, Noguchi N, Itoh K, Yamamoto M. Differential responses of the Nrf2-Keap1 system to laminar and oscillatory shear stresses in endothelial cells. J Biol Chem. 2005; 280: 27244–27250.
20. Yeh M, Leitinger N, de MR, Onai N, Matsushima K, Vora DK, Berliner JA, Reddy ST. Increased transcription of IL-8 in endothelial cells is differentially regulated by TNF-alpha and oxidized phospholipids. Arterioscler Thromb Vasc Biol. 2001; 21: 1585–1591.
21. Gargalovic PS, Gharavi NM, Clark MJ, Pagnon J, Yang WP, He A, Truong A, Baruch-Oren T, Berliner JA, Kirchgessner TG, Lusis AJ. The unfolded protein response is an important regulator of inflammatory genes in endothelial cells. Arterioscler Thromb Vasc Biol. 2006; 26: 2490–2496.
22. Watson AD, Subbanagounder G, Welsbie DS, Faull KF, Navab M, Jung ME, Fogelman AM, Berliner JA. Structural identification of a novel pro-inflammatory epoxyisoprostane phospholipid in mildly oxidized low density lipoprotein. J Biol Chem. 1999; 274: 24787–24798.
23. Niki E, Yoshida Y, Saito Y, Noguchi N. Lipid peroxidation: mechanisms, inhibition, and biological effects. Biochem Biophys Res Commun. 2005; 338: 668–676.[CrossRef][Medline] [Order article via Infotrieve]
24. Furnkranz A, Schober A, Bochkov VN, Bashtrykov P, Kronke G, Kadl A, Binder BR, Weber C, Leitinger N. Oxidized phospholipids trigger atherogenic inflammation in murine arteries. Arterioscler Thromb Vasc Biol. 2005; 25: 633–638.
25. Subbanagounder G, Leitinger N, Schwenke DC, Wong JW, Lee H, Rizza C, Watson AD, Faull KF, Fogelman AM, Berliner JA. Determinants of bioactivity of oxidized phospholipids. Specific oxidized fatty acyl groups at the sn-2 position. Arterioscler Thromb Vasc Biol. 2000; 20: 2248–2254.
26. Chen XL, Dodd G, Thomas S, Zhang X, Wasserman MA, Rovin BH, Kunsch C. Activation of the Nrf2/ARE pathway protects endothelial cells from oxidant injury and inhibits inflammatory gene expression. Am J Physiol Heart Circ Physiol. 2006; 290: H1862–H1870.
27. Bea F, Hudson FN, Chait A, Kavanagh TJ, Rosenfeld ME. Induction of glutathione synthesis in macrophages by oxidized low-density lipoproteins is mediated by consensus antioxidant response elements. Circ Res. 2003; 92: 386–393.
28. Levonen AL, Dickinson DA, Moellering DR, Mulcahy RT, Forman HJ, Darley-Usmar VM. Biphasic effects of 15-deoxy-delta(12,14)-prostaglandin J(2) on glutathione induction and apoptosis in human endothelial cells. Arterioscler Thromb Vasc Biol. 2001; 21: 1846–1851.
29. Levonen AL, Inkala M, Heikura T, Jauhiainen S, Jyrkkänen HK, Kansanen E, Määttä K, Romppanen E, Turunen P, Rutanen J, Ylä-Herttuala S. Nrf2 gene transfer induces antioxidant enzymes and suppresses smooth muscle cell growth in vitro and reduces oxidative stress in rabbit aorta in vivo. Arterioscler Thromb Vasc Biol. 2007; 27: 741–747.
30. Pagano RE, Longmuir KJ. Phosphorylation, transbilayer movement, and facilitated intracellular transport of diacylglycerol are involved in the uptake of a fluorescent analog of phosphatidic acid by cultured fibroblasts. J Biol Chem. 1985; 260: 1909–1916.
31. Tokumura A, Tsutsumi T, Tsukatani H. Transbilayer movement and metabolic fate of ether-linked phosphatidic acid (1-O-octadecyl-2-acetyl-sn-glycerol 3-phosphate) in guinea pig peritoneal polymorphonuclear leukocytes. J Biol Chem. 1992; 267: 7275–7283.
32. Davies SS, Pontsler AV, Marathe GK, Harrison KA, Murphy RC, Hinshaw JC, Prestwich GD, Hilaire AS, Prescott SM, Zimmerman GA, McIntyre TM. Oxidized alkyl phospholipids are specific, high affinity peroxisome proliferator-activated receptor gamma ligands and agonists. J Biol Chem. 2001; 276: 16015–16023.
33. Gugiu BG, Mouillesseaux K, Duong V, Herzog T, Hekimian A, Koroniak L, Vondriska TM, Watson AD. Protein targets of oxidized phospholipids in endothelial cells. J Lipid Res. 2008; 49: 510–520.
34. Gugiu BG, Hekimian A, Koroniak L, Warburton S, Vondriska TM, Li R, Berliner JA, Jung ME, Watson AD. Covalent modification of endothelial cell proteins by oxidized phospholipids may regulate inflammation. Arterioscler Thromb Vasc Biol. 2008; 28: e122.
35. Leitinger N, Watson AD, Faull KF, Fogelman AM, Berliner JA. Monocyte binding to endothelial cells induced by oxidized phospholipids present in minimally oxidized low density lipoprotein is inhibited by a platelet activating factor receptor antagonist. Adv Exp Med Biol. 1997; 433: 379–382.[Medline] [Order article via Infotrieve]
36. Siess W, Zangl KJ, Essler M, Bauer M, Brandl R, Corrinth C, Bittman R, Tigyi G, Aepfelbacher M. Lysophosphatidic acid mediates the rapid activation of platelets and endothelial cells by mildly oxidized low density lipoprotein and accumulates in human atherosclerotic lesions. Proc Natl Acad Sci U S A. 1999; 96: 6931–6936.
37. Walton KA, Hsieh X, Gharavi N, Wang S, Wang G, Yeh M, Cole AL, Berliner JA. Receptors involved in the oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine-mediated synthesis of interleukin-8. A role for Toll-like receptor 4 and a glycosylphosphatidylinositol-anchored protein. J Biol Chem. 2003; 278: 29661–29666.
38. Li R, Mouillesseaux KP, Montoya D, Cruz D, Gharavi N, Dun M, Koroniak L, Berliner JA. Identification of prostaglandin E2 receptor subtype 2 as a receptor activated by OxPAPC. Circ Res. 2006; 98: 642–650.
39. Rouhanizadeh M, Hwang J, Clempus RE, Marcu L, Lassegue B, Sevanian A, Hsiai TK. Oxidized-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine induces vascular endothelial superoxide production: implication of NADPH oxidase. Free Radic Biol Med. 2005; 39: 1512–1522.[CrossRef][Medline] [Order article via Infotrieve]
40. Papaiahgari S, Kleeberger SR, Cho HY, Kalvakolanu DV, Reddy SP. NADPH oxidase and ERK signaling regulates hyperoxia-induced Nrf2-ARE transcriptional response in pulmonary epithelial cells. J Biol Chem. 2004; 279: 42302–42312.
41. Sekhar KR, Crooks PA, Sonar VN, Friedman DB, Chan JY, Meredith MJ, Starnes JH, Kelton KR, Summar SR, Sasi S, Freeman ML. NADPH oxidase activity is essential for Keap1/Nrf2-mediated induction of GCLC in response to 2-indol-3-yl-methylenequinuclidin-3-ols. Cancer Res. 2003; 63: 5636–5645.
42. Warabi E, Takabe W, Minami T, Inoue K, Itoh K, Yamamoto M, Ishii T, Kodama T, Noguchi N. Shear stress stabilizes NF-E2-related factor 2 and induces antioxidant genes in endothelial cells: role of reactive oxygen/nitrogen species. Free Radic Biol Med. 2007; 42: 260–269.[CrossRef][Medline] [Order article via Infotrieve]
43. Ago T, Kitazono T, Ooboshi H, Iyama T, Han YH, Takada J, Wakisaka M, Ibayashi S, Utsumi H, Iida M. Nox4 as the major catalytic component of an endothelial NAD(P)H oxidase. Circulation. 2004; 109: 227–233.
This article has been cited by other articles:
 |
|
 |
|
  E. H. Heiss, D. Schachner, E. R. Werner, and V. M. Dirsch Active NF-E2-related Factor (Nrf2) Contributes to Keep Endothelial NO Synthase (eNOS) in the Coupled State: ROLE OF REACTIVE OXYGEN SPECIES (ROS), eNOS, AND HEME OXYGENASE (HO-1) LEVELS J. Biol. Chem., November 13, 2009; 284(46): 31579 - 31586. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Zakkar, K. Van der Heiden, L. A. Luong, H. Chaudhury, S. Cuhlmann, S. S. Hamdulay, R. Krams, I. Edirisinghe, I. Rahman, H. Carlsen, et al. Activation of Nrf2 in Endothelial Cells Protects Arteries From Exhibiting a Proinflammatory State Arterioscler Thromb Vasc Biol, November 1, 2009; 29(11): 1851 - 1857. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. von Schlieffen, O. V. Oskolkova, G. Schabbauer, F. Gruber, S. Bluml, M. Genest, A. Kadl, C. Marsik, S. Knapp, J. Chow, et al. Multi-Hit Inhibition of Circulating and Cell-Associated Components of the Toll-Like Receptor 4 Pathway by Oxidized Phospholipids Arterioscler Thromb Vasc Biol, March 1, 2009; 29(3): 356 - 362. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Lee, R. Li, B. Kim, R. Palvolgyi, T. Ho, Q.-Z. Yang, J. Xu, W. L. Szeto, H. Honda, and J. A. Berliner Ox-PAPC activation of PMET system increases expression of heme oxygenase-1 in human aortic endothelial cell J. Lipid Res., February 1, 2009; 50(2): 265 - 274. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||