Calcium influx through the TRPV1 channel of endothelial cells (ECs) correlates with a stronger adhesion between monocytes and ECs

Purpose: Atherosclerosis is thought to be initiated by the transendothelial migration of monocytes. In the early stage of this process, the adhesion of monocytes to endothelial cells is supported by an increase in the intracellular concentration of calcium ion ([Ca2+]i) in endothelial cells. However, the main source of Ca2+ has been unclear. In this study, the changes in ionic transmittance and [Ca2+]i due to the adhesion of monocytes were continuously measured by an electrophysiological technique and fluorescent imaging. Especially, we focused on transient receptor potential vanilloid channel 1 (TRPV1) as a Ca2+ channel that could influence the adhesion of monocytes. Material and methods: Whole-cell current was continuously recorded in human umbilical vein endothelial cells (HUVECs) by a patch electrode. Results: The adhesion of monocytes (THP-1) induced a transient inward current in HUVECs, as well as an elevation of [Ca2+]i. This inward element was abolished by the application of 100nM SB366,791, a selective antagonist of TRPV1 channel. Furthermore, SB366,791 significantly decreased the number of THP-1 cells that adhered to HUVECs (control: 231 +/- 38, SB366,791: 96 +/- 16 cells/mm2). Conclusion: These results suggest that an inward calcium current via the TRPV1 channels of endothelial cells correlates with a stronger adhesion between monocytes and endothelial cells.