Spatial regulation of inflammation by human aortic endothelial cells in a linear gradient of shear stress

Objective: Atherosclerosis is a focal disease that develops at sites of low and oscillatory shear stress in arteries. This study aimed to understand how endothelial cells sense a gradient of fluid shear stress and transduce signals that regulate membrane expression of cell adhesion molecules and monocyte recruitment. Methods: Human aortic endothelial cells were stimulated with TNF-alpha and simultaneously exposed to a linear gradient of shear stress that increased from 0 to 16 dyne/cm(2). Cell adhesion molecule expression and activation of NF kappa B were quantified by immunofluorescence microscopy with resolution at the level of a single endothelial cell. Monocyte recruitment was imaged using custom microfluidic flow chambers. Results: VCAM-1 and E-selectin upregulation was greatest between 2-4 dyne/cm(2) (6 and 4-fold, respectively) and above 8 dyne/cm(2) expression was suppressed below that of untreated endothelial cells. In contrast, ICAM-1 expression and NF kappa B nuclear translocation increased with shear stress up to a maximum at 9 dyne/cm(2). Monocyte recruitment was most efficient in regions where E-selectin and VCAM-1 expression was greatest. Conclusions: We found that the endothelium can sense a change in shear stress on the order of 0.25 dyne/cm(2) over a length of similar to 10 cells, regulating the level of protein transcription, cellular adhesion molecule expression, and leukocyte recruitment during inflammation.