Role of endothelial nitric oxide synthase in the regulation of SREBP activation by oxidized phospholipids.
Oxidized-1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine (Ox-PAPC), found in atherosclerotic lesions and other sites of chronic inflammation, activates endothelial cells (EC) to synthesize chemotactic factors, such as interleukin (IL)-8. Previously, we demonstrated that the sustained induction of IL-8 transcription by Ox-PAPC was mediated through the activation of sterol regulatory element-binding protein (SREBP). We now present evidence for the role of endothelial nitric oxide synthase (eNOS) in the activation of SREBP by Ox-PAPC. Ox-PAPC treatment of EC induced a dose- and time-dependent activation of eNOS, as measured by phosphorylation of serine 1177, dephosphorylation of threonine 495, and the conversion of L-arginine to L-citrulline. Activation of eNOS by Ox-PAPC was regulated through a phosphatidylinositol-3-kinase/Akt-mediated mechanism. These studies also demonstrated that pretreatment of EC with NOS inhibitor, Nomega-nitro-L-arginine-methyl ester (L-NAME), significantly inhibited Ox-PAPC-induced IL-8 synthesis. Because SREBP activation had been previously shown to regulate IL-8 transcription by Ox-PAPC, we examined the effects of L-NAME on Ox-PAPC-induced SREBP activation. Our data demonstrated that Ox-PAPC-induced SREBP activation and expression of SREBP target genes were significantly reduced by pretreatment with L-NAME. Interestingly, treatment of EC with NO donor, S-nitroso-N-acetylpenicillamine, did not activate SREBP, suggesting that NO alone was not sufficient for SREBP activation. Rather, our findings indicated that superoxide (O2*-), in combination with NO, regulated SREBP activation by Ox-PAPC. We found that Ox-PAPC treatment generated O2*- through an eNOS-mediated mechanism and that mercaptoethylguanidine, a peroxynitrite scavenger, reduced SREBP activation by Ox-PAPC. Taken together, these findings propose a novel role for eNOS in the activation of SREBP and SREBP-mediated inflammatory processes.
Division of Cardiology, Department of Medicine, University of California, Los Angeles, USA. ngharavi@ucla.edu
Nima M
NM
Gharavi
Nancy A
NA
Baker
Kevin P
KP
Mouillesseaux
Winnie
W
Yeung
Henry M
HM
Honda
Xavier
X
Hsieh
Michael
M
Yeh
Eric J
EJ
Smart
Judith A
JA
Berliner
D000818:Animals; D050197:Atherosclerosis / Q000209:etiology; D000081247:CSK Tyrosine-Protein Kinase; D002417:Cattle; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D052250:Nitric Oxide Synthase Type III / Q000502:physiology*; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010742:Phospholipid Ethers / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D051779:Sterol Regulatory Element Binding Proteins / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D019061:src-Family Kinases
D000081247:CSK Tyrosine-Protein Kinase; D017868:Cyclic AMP-Dependent Protein Kinases; D016209:Interleukin-8; D019331:NG-Nitroarginine Methyl Ester; D052250:Nitric Oxide Synthase Type III; D010713:Phosphatidylcholines; D019869:Phosphatidylinositol 3-Kinases; D010742:Phospholipid Ethers; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051779:Sterol Regulatory Element Binding Proteins; D013481:Superoxides; D019061:src-Family Kinases; C400184:1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine; C468114:1-palmitoyl-2-arachidonyl-3-phosphorylcholine; C000631346:CSK protein, human