Journal of Leukocyte Biology 47:13-24 (1990) Lipopolysaccharide Modulates Chemotactic

To study the effect of endotoxin (LPS) on the basal and chemotactic peptide, formyl-methionyl-leucyl.phenylalanine (fMLP)-induced alterations in neutrophil cytoskeleton, we purified (>98%) LPS-free neutrophils (LPS- < 10 pg/mI LPS), compared their cy-toskeletal organization to that of circulating neutrophils, and examined the effect of LPS exposure on the basal and fMLP-induced change in the cytoskeleton as reflected by F-actin content and distribution. Shape, F-actin content and distribution were monitored by FACS analysis and fluorescence microscopy of NBDphallicidin-stained cells. The F-actin content of basal and fMLP-activated, purified LPS cells is similar to that of circulating neutrophils (defined as cells drawn in LPS buffers at 37#{176}Cand analyzed after <10 seconds of ex vivo manipulation). LPS cells are round with a diffuse F-actin dis-tribution. Exposure of LPS cells to LPS causes cell polarization and F-actin redistribu-tion without net gain in F-actin content. Peptide activation of the LPS cell causes actin polymerization, which is preceded by a brief lag time. Exposure of LPS cells to LPS (LPS) enhances fMLP-induced actin polymerization by: 1) increasing the maximal extent of polymerization; 2) shortening the lag time preceding polymerization and increasing th