4-Hydroxynonenal induces apoptosis, NF-κB-activation and formation of 8-isoprostane in vascular smooth muscle cells

Oxidation of lipids is considered a key feature of atherogenesis. Lipid peroxidation products such as oxidized LDL or the bioactive aldehyde 4-hydroxynonenal (HNE) exert mitogenic effects on vascular smooth muscle cells (VSMC). These effects appear to be concentration-dependent since in addition to our previous reports on growth promotion at lower concentrations we here indicate induction of apoptosis in VSMC by 4-hydroxynonenal (HNE) at higher concentrations (100 mu mol/L). In a line with HNE's previously documented effects on key mitogenic signaling elements, we also report on activation by this aldehyde of the redox-sensitive transcription factor NF-kappaB, a key regulator of apoptosis: HNE (1.0 mu mol/L) induced DNA-binding of NF-KB in VSMC. The effect was inhibited by antioxidants, N-acetylcysteine and pyrrolidine dithio-carbamate. HNE caused phosphorylation but not degradation of the inhibitory subunit I kappaB-alpha. HNE itself acts as an oxidant as was investigated with measurements of 8-isoprostane which ranks among the most valuable available biomarkers of lipid peroxidation: HNE (1.0 mu mol/L) increased 8-isoprostane levels in VSMC by 4.5-fold (p < 0.05). Compared to the controls, plasma samples from apoE(null) mice exhibited elevated levels of 8-isoprostane (40 pg/mL, 3.2-fold increase) and the combined aldehydes HNE and malonaldehyde (1.5 <mu>mol/L, 2.5-fold increase), (p < 0.05, resp). In addition, immunohistochemistry indicated the presence of HNE-protein adducts in atheroscerlotic lesions of apoE(null) mice. Thus HNE is present in atherosclerotic tissue at concentrations that are bioactive in vitro. The data further indicate the involvement of the lipid peroxidation product HNE in atherogenesis.