The Impact of Laminar and Oscillatory Shear Stress on Cellular Adhesion Molecule Expression in HUVEC

Abstract

PURPOSE: To investigate the influence of acute laminar shear stress (LSS) on the expression of VCAM-1 and fractalkine on human umbilical vein endothelial cells (HUVEC) following prolonged exposure to oscillatory shear stress (OSS) in vitro. METHODS: Cultured EC were stimulated with TNF-α for 24 hr and immediately exposed to shear experiments using a parallel-plate flow chamber: (i) 24 hr of LSS or OSS, and (ii) 24 hr of OSS followed by 30 min of LSS. Cells were collected and incubated with primary antibodies for surface VCAM-1 and fractalkine. Samples were analyzed via standard fluorescence-activated cell sorting. RESULTS: Prolonged LSS and OSS significantly reduced the TNF-α-induced elevation in the % of gated cells expressing VCAM-1 (p<0.001) and fractalkine (p=0.001); however, the reduction in VCAM-1 caused by LSS was shown to be significantly greater than the reduction elicited by OSS (p=0.006). Interestingly, the mean fluorescent intensity (MFI) of TNF-α-induced VCAM-1 was significantly elevated by prolonged OSS (1.60±0.01 fold [p<0.001]). Whereas, prolonged LSS had no impact on the MFI of TNF-α induced VCAM-1 (p=0.931). Prolonged LSS and OSS elicited a significant elevation in the MFI of TNF-α induced fractalkine (p=0.017). Lastly, acute LSS following prolonged OSS had no effect on the % of gated or MFI of cells expressing VCAM-1 and fractalkine. CONCLUSIONS: Prolonged OSS may increase markers of vascular inflammation. However, an acute period of LSS, utilized as a model of physical activity, does not appear to alter the OSS-induced inflammatory state.