Modulation of K+ currents in monocytes by VCAM-1 and E-selectin on activated human endothelium

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Abstract
Resting membrane potential (RMP) and whole cell currents were recorded in human THP-1 monocytes adherent to polystyrene, unstimulated human umbilical vein endothelial cells (HUVECs), lipopolysaccharide (LPS)-treated HUVECs, immobilized E-selectin, or vascular cell adhesion molecule 1 (VCAM-1) using the patch-clamp technique. RMP after 5 h on polystyrene was −24.3 ± 1.7 mV ( n = 42) with delayed rectifier K+( I dr) and Cl− currents ( I Cl) present in >75% of the cells. Inwardly rectifying K+ currents ( I ir) were present in only 14% of THP-1 cells. Adherence to unstimulated HUVECs or E-selectin for 5 h had no effect on I ir or I Cl but decreased I dr. Five hours after adherence to LPS-treated HUVECs, outward currents were unchanged, but I ir was present in 81% of THP-1 cells. A twofold increase in I ir and a hyperpolarization (−41.3 ± 3.7 mV, n = 16) were abolished by pretreatment of THP-1 cells with cycloheximide, a protein synthesis inhibitor, or herbimycin A, a tyrosine kinase inhibitor, or by pretreatment of the LPS-treated HUVECs with anti-VCAM-1. Only a brief (15-min) interaction between THP-1 cells and LPS-treated HUVECs was required to induce I irexpression 5 h later. THP-1 cells adherent to VCAM-1 exhibited similar conductances to cells adherent to LPS-treated HUVECs. Thus engagement of specific integrins results in selective modulation of different K+ conductances.

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