MODULATION OF K-1 AND E-SELECTIN ON ACTIVATED HUMAN ENDOTHELIUM( CURRENTS IN MONOCYTES BY VCAM)

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)-tr eated HUVECs, immobilized E-selectin, or vascular cell adhesion molecu le 1 (VCAM-1) using the patch-clamp technique. RMP after 5 h on polyst yrene was -24.3 +/- 1.7 mV (n = 42) with delayed rectifier K+ (I-dr) a nd Cl- currents (I-cl) present in >75% of the cells. Inwardly rectifyi ng K+ currents (I-ir) were present in only 14% of THP-1 cells. Adheren ce 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% o f 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 w ith cycloheximide, a protein synthesis inhibitor, or herbimycin A, a t yrosine kinase inhibitor, or by pretreatment of the LPS-treated HUVECs with anti-VCAM-1. Only a brief (15-min) interaction between THP-1 cel ls and LPS-treated HUVECs was required to induce I-ir expression 5 h l ater. THP-1 cells adherent to VCAM-1 exhibited similar conductances to cells adherent to LPS-treated HUVECs. Thus engagement of specific int egrins results in selective modulation of different K+ conductances.