A20 overexpression inhibits low shear flow-induced CD14-positive monocyte recruitment to endothelial cells.

Objective: To determine if A20, a zinc finger protein that mediates the inflammatory response, affects monocyte-endothelial cell-cell interactions induced by low shear flow.

Methods: Primary cultured endothelial cells (EC) were transfected with an A20 expression vector, and the VCAM-1, ICAM-1 and IL-8 mRNA, and protein expression levels in A20-transfected EC lysates were checked by PCR array and ELISA, respectively. CD14-positive monocyte migration toward and adhesion to EC were measured using a parallel plate flow chamber.

Results: Low shear stress, defined as 0.2 Pa for 6 h, normally increases VCAM-1, ICAM-1 and IL-8 expression in EC and allows for binding of monocytes to EC. We found that overexpression of A20 in EC inhibits their normal expression of VCAM-1, ICAM-1 and IL-8 under low shear stress conditions. We also found that A20 inhibits IkappaBalpha degradation in EC following low shear stress exposure and that it attenuates the rolling and EC adhesive properties of shear-induced monocytes as compared with untransfected control EC. The results demonstrate that A20 overexpression in EC inhibits low shear flow-induced monocyte-EC interactions. These findings may be useful in the development of therapeutic agents aimed at treating chronic inflammatory diseases like atherosclerosis.