Increased binding of U937 monocytes to vascular endothelial cells treated with acidic pH.

<p>(A) U937 monocytic cells were adherent to acidic pH-treated HUVEC/GPR4 cells under a flow condition. Representative pictures are shown with the adhered U937 cells indicated by arrows. (B) HUVECs stably overexpressing GPR4 or control vector were grown to a monolayer, and were treated with EGM-2/HEM pH 8.4, 7.4 or 6.4 media for 5 h. U937 monocytes were adhered to the pH-treated HUVEC monolayer under a flow condition (0.5 dyne/cm²). Error bars indicate the mean ± SEM. ***, <i>P</i><0.001; compared with the pH 8.4 groups. The results represent the average of cell counts from 6 fields.