title: Oxidized low-density lipoproteins potentiate the mitogenic effect of 5-hydroxytryptamine on vascular smooth muscle cells.
abstract: Considerable attention has been focused on both highly oxidized low-density lipoprotein (ox-LDL) and mildly oxidized LDL (mox-LDL) as important risk factors for cardiovascular disease. Further, 5-hydroxytryptamine (5-HT) appears to play a crucial role in the development of atherosclerotic plaque. We assessed the interaction of oxidatively modified LDL and its major oxidative components, ie, hydrogen peroxide (H2O2), lysophosphatidylcholine (LPC), and 4-hydroxy-2-nonenal (HNE) with 5-HT on DNA synthesis in vascular smooth muscle cells (VSMCs). Growth-arrested rabbit VSMCs were incubated in serum-free medium with native LDL, mox-LDL, ox-LDL (all 50 ng/mL), H2O2 (0.5 microM), LPC (1 microM), or HNE (0.1 microM) for 24 hours followed by 5-HT (5 microM) for another 24 hours. DNA synthesis in VSMCs was measured by [3H]thymidine incorporation. Significant effects on [3H]thymidine incorporation were observed in VSMCs incubated with mox-LDL (129%), ox-LDL (129%), H2O2 (119%), LPC (115%), HNE (127%), or 5-HT (183%) in contrast with native LDL (113%). The mitogenic effect of 5-HT was potentiated by mox-LDL, ox-LDL, H2O2, LPC, or HNE (183 to 365%, 274%, 304%, 339%, or 273%, respectively) but not by native LDL (240%). The mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059 (10 microM) significantly inhibited the mitogenic effect of 5-HT but did not influence the effects of mox-LDL, ox-LDL, H2O2, LPC, or HNE. The intracellular antioxidant N-acetylcysteine (400 microM) significantly inhibited the mitogenic effects of mox-LDL, ox-LDL, H2O2, LPC, and HNE but not that of 5-HT. Our results suggest that mox-LDL, ox-LDL, and their major components H2O2, LPC, and HNE act synergistically with 5-HT in inducing VSMC DNA synthesis via MAPK and redox-sensitive pathways, contributing to the development of atherosclerotic plaque.
authors.affiliation: Third Department of Internal Medicine, Showa University School of Medicine, Tokyo, Japan.
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: D000818:Animals; D001161:Arteriosclerosis / Q000209:etiology; D002455:Cell Division / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008297:Male; D008934:Mitogens / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology*; D015398:Signal Transduction
chemical_list: D005419:Flavonoids; D008077:Lipoproteins, LDL; D008934:Mitogens; C099252:oxidized low density lipoprotein; D012701:Serotonin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one