Membrane Cholesterol Is a Biomechanical Regulator of Neutrophil Adhesion

Abstract

The purpose of this study was to evaluate the role of membrane cholesterol on human neutrophil and HL-60 biomechanics, capture, rolling, and arrest to P-selectin- or IL-1-activated endothelium. Methyl-beta-cyclodextrin (MbetaCD) removed up to 73% and 45% of membrane cholesterol from HL-60 cells and neutrophils, whereas MbetaCD/cholesterol complexes resulted in maximum enrichment of 65% and 40%, respectively, above control levels. Cells were perfused at a venous wall shear rate of 100 s(-1) over adherent P-selectin-coated 1-microm diameter beads, uncoated 10-mum diameter beads, P-selectin-coated surfaces, or activated endothelium. Elevated cholesterol enhanced capture efficiency to 1-microm beads and increased membrane tether growth rate by 1.5- to 2-fold, whereas cholesterol depletion greatly reduced tether formation. Elevated cholesterol levels increased tether lifetime by 17% in neutrophils and adhesion lifetime by 63% in HL-60 cells. Deformation of cholesterol-enriched neutrophils increased the contact time with 10-mum beads by 32% and the contact area by 7-fold. On both P-selectin surfaces and endothelial-cell monolayers, cholesterol-enriched neutrophils rolled more slowly, more stably, and were more likely to firmly arrest. Cholesterol depletion resulted in opposite effects. Increasing membrane cholesterol enhanced membrane tether formation and whole cell deformability, contributing to slower, more stable rolling on P-selectin and increased firm arrest on activated endothelium.