title: Lysophosphatidylcholine is a major contributor to the synergistic effect of mildly oxidized low-density lipoprotein with endothelin-1 on vascular smooth muscle cell proliferation.
abstract: Endothelin-1 (ET-1) and oxidized low-density lipoprotein (ox-LDL) are associated with atherosclerosis and essential hypertension. We assessed the effect of mildly oxidized LDL (mox-LDL) and ox-LDL and their major oxidative components, i.e., reactive oxygen species (ROS), lysophosphatidylcholine (LPC), and 4-hydroxy-2-nonenal (HNE) and their interaction with ET-1 on vascular smooth muscle cell (VSMC) proliferation. Growth-arrested VSMCs isolated from the rabbit aorta were incubated with different concentrations of LDL, mox-LDL, ox-LDL, hydrogen peroxide (H(2)O(2)) (a donor of ROS), LPC, or HNE with or without ET-1. DNA synthesis in VSMCs was measured by [(3)H] thymidine incorporation. Mox-LDL, ox-LDL, H(2)O(2), LPC, HNE, or ET-1 stimulated DNA synthesis in a dose-dependent manner. Maximal effect was observed at 5 microg/ml for mox-LDL (162%) or ox-LDL (154%), 15 microM LPC (156%), 5 microM H2O2 (177%), 1 microM HNE (144%), and 0.1 microM ET-1 (195%). By contrast, LDL was without any significant effect. When added together, there was no synergistic effect of LDL, H2O2, or HNE with ET-1 on DNA synthesis. However, the effect of mox-LDL (0.1 microg/ml), ox-LDL (0.5 microg/ml), or LPC (10 microM) was potentiated by ET-1 (114%-338%, 133%-425%, 118%-333%, respectively). The mitogenic effect of mox-LDL, ox-LDL, or LPC and their interaction with ET-1 were inhibited by defatted albumin (10 microg/ml), antioxidant N-acetylcysteine (400 microM), the reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (1 microM). The ET(A/B) receptor antagonist TAK044 (1 microM) or the MAPK kinase inhibitor PD098059 (10 microM) inhibited the mitogenic effect of ET-1 and its interaction with mox-LDL, ox-LDL, or LPC. The synergistic interaction of mox-LDL, ox-LDL, or LPC with ET-1 was completely reversed by the combined use of N-acetylcysteine and TAK044. Our results suggest that mox-LDL, ox-LDL, and their major phospholipid component LPC act synergistically with ET-1 in inducing VSMC proliferation by way of the activation of redox-sensitive and MAPK pathways.
authors.affiliation: Department of Internal Medicine, Division of Cardiology, University of Texas-Houston Health Science Center, Houston, Texas 77030, USA.
authors.forename: Takuya
authors.initials: T
authors.lastname: Watanabe
authors.forename: Rajbabu
authors.initials: R
authors.lastname: Pakala
authors.forename: Takashi
authors.initials: T
authors.lastname: Katagiri
authors.forename: Claude R
authors.initials: CR
authors.lastname: Benedict
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000447:Aldehydes / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000378:metabolism; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006131:Growth Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000502:physiology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D009861:Onium Compounds / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011817:Rabbits; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000447:Aldehydes; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D005419:Flavonoids; D016166:Free Radical Scavengers; D006131:Growth Inhibitors; D008077:Lipoproteins, LDL; D008244:Lysophosphatidylcholines; D009861:Onium Compounds; D016877:Oxidants; D010456:Peptides, Cyclic; D017382:Reactive Oxygen Species; C099252:oxidized low density lipoprotein; C088196:TAK 044; C007517:diphenyleneiodonium; D004247:DNA; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D020929:Mitogen-Activated Protein Kinase Kinases; C027576:4-hydroxy-2-nonenal; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000111:Acetylcysteine