Regulation of human 12/15-lipoxygenase by Stat6-dependent transcription.

Human 12/15-lipoxygenase is a lipid-peroxidating enzyme implicated in the pathophysiology of atherosclerosis and airway inflammation. Interleukin (IL)-4 specifically induces 12/15-lipoxygenase messenger RNA, protein, and enzymatic activity in primary cultures of human monocytes and airway epithelial cells. The induction of the human 12/15-lipoxygenase by IL-4 suggests that the signal transducer and activator of transcription (Stat)-6 protein is critical for its expression. Several putative Stat6 response elements are located in the proximal 1.8 kb of 12/15-lipoxygenase 5'-flanking region. In this study we use BEAS-2B human airway epithelial cells as a model to demonstrate the dependence of 12/15-lipoxygenase expression on the IL-4/Stat6 signal transduction pathway. Transient transfections of human 12/15-lipoxygenase promoter/luciferase reporter genes indicate that this induction occurs through direct transcriptional mechanisms mediated by a specific Stat6 response element located 952 base pairs upstream of the translational start codon. Using this Stat6 response element as a probe, electrophoretic mobility shift assays show an IL-4-dependent binding activity in nuclear extracts. Supershift assays confirm that Stat6 participates in this binding complex. These data indicate that the human 12/15-lipoxygenase gene is induced in airway epithelial cells through Stat6-dependent transcriptional mechanisms mediated by a specific Stat6 response element in the 5'-flanking region.