CYCLIC STRAIN IS A WEAK INDUCER OF PROSTACYCLIN SYNTHASE EXPRESSION IN BOVINE AORTIC ENDOTHELIAL-CELLS

Recent studies indicate that hemodynamic forces such as cyclic strain and shear stress can increase prostacyclin (PGI(2)) secretion by endot helial cells (EC) but the effect of these forces on prostacyclin synth ase (PGIS) gene expression remains unclear and is the focus of this st udy. Bovine aortic EC were seeded onto type I collagen coated flexible membranes and grown to confluence. The membranes and attached EC were subjected to 10% average strain at 60 cpm (0.5 sec deformation altern ating with 0.5 sec relaxation) for up to 5 days. PGIS gene expression was determined by Northern blot analysis and protein level by Western blot analysis, The effect of cyclic strain on the PGIS promoter was de termined by the transfection of a 1-kb human PGIS gene promoter constr uct coupled to a luciferase reporter gene into EC, followed by determi nation of luciferase activity. PGIS gene expression increased 1.7-fold in EC subjected to cyclic strain for 24 hr. Likewise, EC transfected with a pGL3B-PGIS (-1070/-10) construct showed an approximate 1.3-fold elevation in luciferase activity in EC subjected to cyclic strain for 2, 4, 8, and 12 hr. The weak stimulation of PGIS gene expression by c yclic strain was reflected in an inability to detect alterations in PG IS protein levels in EC subjected to cyclic strain for as long as 5 da ys, These data suggest that strain-induced stimulation of PGIS gene ex pression plays only a minor role in the ability of cyclic strain to st imulate PGI(2) release in EC. These findings coupled with our earlier demonstration of a requisite addition of exogenous arachidonate in ord er to observe strain-induced PGI(2) release, implicates a mechanism th at more likely involves strain-induced stimulation of PGIS activity. ( C) 1997 Academic Press.