Involvement of NF‐κB/ERK and Sp1/p38 MAPK pathways in HNE‐induced 5‐lipoxygenase expression in murine macrophages

Abstract

5‐LO is suggested as a modulator of atherosclerotic plaque instability, and co‐exist with 4‐hydroxynonenal (HNE) in macrophages in atherosclerotic lesions. To determine the potential role for HNE on the regulation of 5‐LO expression, the promoter activity of 5‐LO was evaluated in HNE‐stimulated macrophages. A genomic sequence of promoter 2.0 kb upstream of the transcription initiation site of mouse genomic DNA was amplified by PCR, and then the constructs containing a series of sequentially deleted fragments was fused to pGL3 vector. Luciferase assay showed that promoter region 50–213 bp upstream of transcription start site was responsible for HNE‐enhanced transcriptional activity of 5‐LO. The importance of NF‐κB and Sp1 in HNE‐induced 5‐LO expression was demonstrated by siRNA knockdown of NF‐κB and Sp1 as well as by a site‐directed mutagenesis. Among the MAPK pathways, HNE‐enhanced NF‐κB and Sp1 activities were attenuated by an ERK inhibitor, and a p38 MAPK inhibitor, respectively. Moreover, the HNE‐enhanced phosphorylation of ERK and p38 MAPK was significantly attenuated by an EGF receptor antagonist, but not by PDGF receptor antagonist. Collectively, these data suggest that 5‐lipoxygenase expression by HNE is regulated via EGF receptor‐mediated activation of NF‐κB/ERK and Sp1/p38 MAPK pathways.