Activator Protein-1 Mediates Shear Stress–Induced Prostaglandin D Synthase Gene Expression in Vascular Endothelial Cells

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Abstract
Objective— We attempted to determine the molecular mechanism of fluid shear stress–induced lipocalin-type prostaglandin D synthase ( l- PGDS) expression in vascular endothelial cells. Methods and Results— We examined the promoter region of the l -PGDS gene by loading laminar shear stress (20 dyne/cm 2 ), using a parallel-plate flow chamber, on endothelial cells transfected with luciferase reporter vectors containing the 5′-flanking regions of the human l -PGDS gene. A deletion mutant analysis revealed that a shear stress–responsive element resided in the region between −2607 and −2523 bp. A mutation introduced into the putative binding site for activator protein-1 (AP-1) within this region eliminated the response to shear stress. In an electrophoretic mobility shift assay, shear stress stimulated nuclear protein binding to the AP-1 binding site, which was supershifted by antibodies to c-Fos and c-Jun. Shear stress elevated the c-Jun phosphorylation level in a time-dependent manner, similar to that of l -PGDS gene expression. SP600125, a c-Jun N-terminal kinase inhibitor, decreased the c-Jun phosphorylation, DNA binding of AP-1, and l -PGDS expression induced by shear stress. Additionally, an mRNA chase experiment using actinomycin D demonstrated that shear stress did not stabilize l -PGDS mRNA. Conclusions— Shear stress induces l -PGDS expression by transcriptional activation through the AP-1 binding site.

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