Regulation of endothelial cell nitric oxide synthase mrna
expression by shear stress.
Uematsu, Masaaki, Yuichi Ohara, Jorge P. Navas, Ken'ichi Nishida, T.
J. Murphy, R. Wayne Alexander, Robert M. Nerem, David G. Harrison.
Biomechanics Laboratory, School of Mechanical Engineering, Georgia
Institute of Technology, Atlanta, GA; the Cardiology Division,
Department of Internal Medicine, Emory University School of Medicine,
Atlanta, GA; and the Veterans Administration Hospital, Decatur,
GA
APStracts 2:0235C, 1995.
Shear stress enhances the expression of the calcium/calmodulin
-sensitive endothelial cell nitric oxide synthase (ecNOS) mRNA and
protein in bovine aortic endothelial cells (BAEC). The present
studies were performed to investigate mechanisms responsible for
regulation of ecNOS mRNA expression by shear stress and to determine
if this induction of ecNOS mRNA is accompanied by an enhanced nitric
oxide (NO) production. Shear stresses of 15 dynes/cm2 for 3 24 hours
resulted in a 2 3 fold increase of ecNOS mRNA content quantified by
Northern analysis in BAEC. Shear stresses (1.2 15 dynes/cm2) for 3
hours resulted in an induction of ecNOS mRNA in a dose-dependent
manner. In human aortic endothelial cells, shear stresses of 15
dynes/cm2 for 3 hours also resulted in ecNOS mRNA induction. In BAEC,
this induction in ecNOS mRNA was prevented by co-incubation with
actinomycin D (10 [mu]g/ml). The potassium channel antagonist
tetraethylammonium chloride (3 mM) prevented the increase in ecNOS
mRNA in response to shear stress. The ecNOS promotor contains
putative binding domains for AP-1 complexes, potentially responsive
to activation of protein kinase C (PKC). However, selective PKC
inhibitor calphostin C (100 nM) did not inhibit ecNOS induction by
shear stress. Finally, production of nitrogen oxides under both basal
conditions and in response to the calcium ionophore A23187 (1 [mu]M)
by BAEC exposed to shear stress was increased approximately two fold
compared to cells not exposed to shear stress. These data suggest
that ecNOS mRNA expression is regulated by potassium channel opening,
but not by activation of PKC, and that shear not only enhances ecNOS
mRNA expression but increases the capacity of endothelial cells to
release nitric oxide.
Received 29 November 1994; accepted in final form 22 May 1995.
APS Manuscript Number C697-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.