title: Native LDL induces proliferation of human vascular smooth muscle cells via redox-mediated activation of ERK 1/2 mitogen-activated protein kinases.
abstract: This study investigated mechanisms underlying native low-density lipoprotein (LDL)-stimulated proliferation of human vascular smooth muscle cells (VSMC). Experiments were performed to determine whether native LDL affects reactive oxygen species (ROS) formation and activity of extracellular signal-regulated kinase 1/2 (ERK1/2), and whether redox-sensitive pathways contribute to LDL-induced cell proliferation. Native LDL (100 microg/mL, 24 hours) increased cell proliferation (to 303 to 388% of control, P<0.0001) as determined by [methyl-(3)H] thymidine incorporation. This effect was completely blocked either by the antioxidants N-acetylcysteine, Tiron, or nordihydroguaiaretic acid; the flavin-inhibitor diphenylene iodonium; or superoxide dismutase (all P<0.0001), and partly blocked by ERK-inhibitor PD98059 or meclofenamate (P<0.01). Exposure of VSMC to native LDL for 20 minutes stimulated ROS formation, measured by dichlorodihydrofluorescein oxidation, and increased ERK1/2 activity by 3.1-fold (P<0.001). The latter effect was sensitive to MEK1/2 inhibitor PD98059 and Tiron (P<0.001), and in part to N-acetylcysteine or diphenylene iodonium (P<0.05). These results demonstrate that native LDL induces acute formation of ROS and subsequent activation of redox-sensitive ERK 1/2 mitogen-activated protein kinases, pathways that appear to be important for mitogenic signaling of native LDL in human vascular smooth muscle cells.
authors.affiliation: Department of Internal Medicine, University Hospital, Zürich, Switzerland.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Locher
authors.forename: Ralf P
authors.initials: RP
authors.lastname: Brandes
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Vetter
authors.forename: Matthias
authors.initials: M
authors.lastname: Barton
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004586:Electrophoresis; D004789:Enzyme Activation; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D008077:Lipoproteins, LDL; D017382:Reactive Oxygen Species; D007770:L-Lactate Dehydrogenase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases