Disturbed blood flow acutely induces activation and apoptosis of the human vascular endothelium

Abstract

There is strong and consistent evidence from in vitro studies that disturbed blood flow produces a proatherogenic vascular endothelial phenotype. However, data from human studies are lacking. To address this, a 220 mm Hg occlusion cuff was placed on the distal forearm of 10 young, healthy men to induce a localized region of disturbed blood flow in the proximal vasculature for 20 minutes. We hypothesized that disturbed blood flow would induce endothelial activation and apoptosis as indicated by increases in local concentrations of CD62E(+) and CD31(+)/CD42b(-) endothelial microparticles, respectively. Distal cuff occlusion induced reductions in mean blood flow, mean shear, and antegrade shear, and increases in retrograde flow, retrograde shear, and oscillatory shear stress, confirming that our protocol produced a disturbed blood flow stimulus in the experimental arm. Relative to baseline (0 minutes), CD62E(+) endothelial microparticles increased by ≈3-fold at 10 minutes and ≈4-fold at 20 minutes in the experimental arm (P<0.05). CD31(+)/CD42b(-) endothelial microparticles were elevated by ≈9-fold at the 20 minutes time point (P<0.05). There were no changes in the concentrations of either endothelial microparticle population throughout the experiment in the contralateral arm, exposed to normal resting blood flow (no cuffs). These findings indicate that disturbed blood flow acutely induces endothelial activation and apoptosis in humans, as reflected by release of microparticles from activated (CD62E(+)) and apoptotic (CD31(+)/CD42b(-)) endothelial cells. These data provide the first in vivo experimental evidence of disturbed blood flow-induced endothelial injury in humans.

Figure 1. Experimental set-up (A) and design (B)

Refer to methods for details.

Figure 2. Effect of disturbed flow on local concentrations of CD62E⁺ (A) and CD31⁺/CD42b⁻ (B) endothelial microparticles (EMPs)

*Significantly different from within-arm baseline (0 min) value (P < 0.05). †Significantly different from contralateral arm (exposed to normal resting blood flow, i.e. no cuffs) at the same time point (P < 0.05).

Figure 3. Characterization of the disturbed flow stimulus induced by the experimental protocol

(A) Mean blood flow, (B) Antegrade, mean, and retrograde shear rates, (C) Oscillatory shear index, (D) Representative Doppler brachial artery blood velocity traces from the experimental arm. *Significantly different from baseline (0 min) value (P < 0.05).