Suppression of Angiotensin-Converting Enzyme Expression and Activity by Shear Stress

Abstract

Shear stress caused by the frictional forces of a fluid moving over a cell monolayer is an important regulator of gene expression. In this study, we investigated the effect of shear stress on angiotensin-converting enzyme (ACE) expression and promoter activity in vitro and on local vascular ACE activity in vivo. ACE activity measured in bovine pulmonary artery endothelial (BPAE) cells was reduced by 49.5% after exposure to a shear stress of 20 dyne/cm2 for 18 hours. Short-term shearing (2 hours) elevated ACE activity in BPAE cells, whereas long-term shearing produced a time-dependent reduction in ACE activity by 23.3%, 33.5%, and 48.9% at 8, 12, and 18 hours, respectively. Northern blot analysis revealed that shear stress (20 dyne/cm2 for 18 hours) significantly reduced ACE mRNA expression by 82%. To determine the mechanism of ACE activity and message reduction, the effect of shear on transcriptionally related events was determined in a rabbit aortic endothelial cell line (W3LUC) stably transfected with 1.3 kb of a rat ACE promoter/luciferase construct. Different shear stress magnitudes (5 to 20 dyne/cm2) caused suppression of luciferase activity by an average of 40.7%. ACE promoter activity was suppressed by 2 hours of shear stress (24.7%) and was further inhibited at time periods > 8 hours. In vivo elevations in shear stress were created by placing a stainless steel clip over a 12-mm region of the rat abdominal aorta. Restriction of vessel diameter increased blood flow velocity and caused reduction in vascular ACE activity by 40%. These studies suggest that elevations in the level of shear stress alter endothelial cell function by suppressing ACE gene and protein expression in vitro and in vivo.

The Aryl hydrocarbon receptor is activated by modified low-density lipoprotein

“…Human LDL (Intracel, Frederick, MD) was diluted to a 0.1 mg/ml concentration in DMEM. A 5-ml volume of DMEM/LDL was exposed to 18 dyne/cm 2 shear stress for 1 h by using a cone-plate viscometer provided by Andrew Greene (Medical College of Wisconsin), as described (16). A static, control solution of LDL was incubated in an identical setup without rotation of the cone.…”

Shear stress stimulates phosphorylation of eNOS at Ser635by a protein kinase A-dependent mechanism

“…A confluent monolayer of BAEC grown in a 100-mm dish was exposed to nonpulsatile, laminar shear stress in a shear medium (phenol red-free DMEM containing 0.5% FBS and 25 mM HEPES, pH 7.4) by rotating a Teflon cone (0.5°cone angle) as we described previously (21,43). Cells were exposed to an arterial level of shear stress (15 dyn/cm 2 ) (3,21).…”

Endothelial KLF2 Links Local Arterial Shear Stress Levels to the Expression of Vascular Tone-Regulating Genes

“…The lentiviral induction is shown to result in an increase of LKLF protein that was correctly targeted to the endothelial nucleus (Figure 7, A and B) and is similar to the LKLF increase and nuclear localization that is observed under prolonged shear stress ( Figure 7, C and D). Seven days after transduction of HUVECs with the mock or LKLF lentivirus, real-time RT-PCR was used to study the expression of the following known shear-regulated genes: endothelin-1, 12 adrenomedullin, 14 ACE, 13 and eNOS. 11 The results reveal consistent transcriptional regulation of these genes by prolonged expression of LKLF in the Figure 6.…”

“…10,11 Well-known examples are the shear-repressed endothelin, 12 angiotensin-converting enzyme (ACE), 13 and adrenomedullin, 14 and the shear-induced endothelial nitric oxide synthase (eNOS). 11 It was recently demonstrated that LKLF potently induces functional eNOS expression by directly binding its promoter.…”