Troglitazone and 15-deoxy-delta(12,14)-prostaglandin J2 inhibit shear-induced coupling factor 6 release in endothelial cells.

OBJECTIVE: We previously showed that mitochondrial coupling factor 6 (CF6), an endogenous inhibitor of prostacyclin synthesis and a vasoconstrictor, is present on the surface of human umbilical vein endothelial cells (HUVEC) and is released outside of the cells by shear stress. We investigated the intracellular signaling mechanism for shear-induced release of CF6 in HUVEC and the effects of troglitazone and 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2), both peroxisome proliferator-activated receptor (PPAR)-gamma ligands, on it.

METHODS AND RESULTS: The release and gene expression of CF6 in HUVEC were enhanced by shear stress at 25 dyn/cm2, measured by radioimmunoassay and real-time RT-PCR, respectively. The intracellular content of CF6 was decreased after exposure to shear stress at 25 dyn/cm2. Transfection experiments with deletional and mutational CF6 promoter constructs, and with dominant negative mutant IkappaB kinase alpha (K44M) demonstrated that shear-induced CF6 transcription was dependent on nuclear factor-kappa B (NF-kappaB) activation. Pretreatment with troglitazone or 15d-PGJ2 inhibited the shear-induced release and gene expression of CF6, whereas fenofibric acid, a PPAR-alpha ligand, had no influence on them. Western blot and immunostaining showed that troglitazone and 15d-PGJ2 inhibited the shear-induced, reactive oxygen species (ROS)-mediated activation of NF-kappaB at the level of IkappaB protein.

CONCLUSIONS: The shear-induced gene expression and release of CF6 in HUVEC are mediated by the ROS-related activation of NF-kappaB signaling pathway. Troglitazone and 15d-PGJ2 inhibit them at the IkappaB protein level.