Induction of Rat Aortic Smooth Muscle Cell Growth by the Lipid Peroxidation Product 4-Hydroxy-2-Nonenal

Abstract

Background —Atherosclerotic lesion formation is a complex process, in part mediated by inflammatory and oxidative mechanisms including lipid peroxidation. To further characterize the potential role of lipid peroxidation products in atherogenesis, we studied the effects of 4-hydroxy-2-nonenal (HNE) on rat aortic smooth muscle cell growth. Methods and Results —HNE, at concentrations of 1.0 and 2.5 μmol/L, significantly stimulated rat aortic smooth muscle cell growth as determined by cell counts, [ 3 H]-thymidine uptake, and incorporation of bromo-deoxyuridine. To characterize the mechanism of HNE-induced mitogenesis, its effect on activation of intracellular growth signaling pathways was examined. Treatment with HNE resulted in activation of extracellular signal-regulated protein kinases ERK1 and ERK2, induction of c- fos and c- jun protein expression, and an increase in transcription factor AP-1 DNA binding activity. In addition, HNE induced expression of platelet-derived growth factor-AA (PDGF-AA) protein, and an anti–PDGF-AA antibody specifically inhibited HNE-mediated DNA synthesis, suggesting that growth factor induction may play a role in HNE-induced vascular smooth muscle cell growth. The role of redox-sensitive mechanisms in this process was further supported by the observation that HNE-induced DNA synthesis and AP-1 activation were inhibited by the antioxidants N -acetylcysteine and pyrrolidine dithiocarbamate. Conclusions —These data demonstrate that HNE, one of several important lipid peroxidation products, induces rat aortic smooth muscle cell growth through redox-sensitive mechanisms and growth factor expression. These observations are consistent with a role for lipid peroxidation products in vascular smooth muscle cell growth in atherogenesis.