Effect of zymosan-activated plasma on the deformability of rabbit polymorphonuclear leukocytes

Abstract

Intravascular infusion of inflammatory mediators causes a sudden neutropenia due to the sequestration of polymorphonuclear leukocytes (PMN) within the microvasculature of the lung and other organs. This sequestration could be due to a decrease in the ability of PMN to deform and pass through the narrow capillary bed. The purpose of this study was to determine if the complement fragments present in zymosan-activated plasma (ZAP) caused a rapid stiffening of PMN. The PMN deformability was determined by measuring the pressure required to pass PMN through a polycarbonate filter containing 5-micron pores at a constant flow rate as well as the extraction of PMN compared with red blood cells and 125I-labeled albumin by the filter. The role of the cytoskeleton in PMN deformation was examined in studies where F-actin formation was inhibited using cytochalasin B or microtubule assembly was inhibited using colchicine. The results showed that treatment with ZAP induced a rapid decrease in PMN deformability. Inhibiting the formation of F-actin made the unstimulated PMN more deformable and reduced the stiffening induced by ZAP. In contrast, inhibition of microtubule reassembly did not alter either normal deformability or the ZAP-induced decrease in deformability. In vivo, colchicine increased normal PMN margination but did not inhibit the rapid sequestration of PMN induced by infusion of ZAP. These studies indicate that ZAP induces a rapid decrease in PMN deformability that is mediated through the cytoskeleton. They suggest that this decrease is due to the polymerization of F-actin.

Unique Structural Features That Influence Neutrophil Emigration Into the Lung

“…A number of investigations have provided evidence that activation of neutrophils further contributes to the failure of transit through the alveolar capillary bed (63,91,92,106,115,187,194,199,278,290), and changes in mechanical properties after activation may be of major importance. Binding of mediators such as chemotactic factors (e.g., the complement fragment C5a) to neutrophil receptors induces a transient resistance of the cells to deformation (27,35,60,62,69,115,289). Because neutrophils must deform to pass through the capillary bed, leukocyte activation by inflammatory mediators could effect further concentration of neutrophils at the alveolar walls (51,52,102,115,180,289).…”

“…Binding of mediators such as chemotactic factors (e.g., the complement fragment C5a) to neutrophil receptors induces a transient resistance of the cells to deformation (27,35,60,62,69,115,289). Because neutrophils must deform to pass through the capillary bed, leukocyte activation by inflammatory mediators could effect further concentration of neutrophils at the alveolar walls (51,52,102,115,180,289). The role of mechanical factors in the initial sequestration of neutrophils in the alveolar capillaries is supported by evidence that neither L-selectin nor ␤ 2 -integrins are required (51,64,132).…”

Effect of mechanical deformation on structure and function of polymorphonuclear leukocytes

“…Although erythrocytes [red blood cells (RBC)] have similar maximum dimensions to PMN, their greater deformability allows them to negotiate these restrictions more quickly (14). This results in pulmonary capillary transit times that are 60-100 times longer for PMN than for RBC, and this concentrates PMN with respect to RBC in pulmonary capillaries (14,15).Stimuli such as peptide chemoattractants, endotoxin, and smoking are known to decrease PMN deformability and further increase the concentration of PMN in pulmonary capillaries (6,18,27,30). Several in vitro filtration studies have measured the biophysical properties of PMN, particularly their size and deformability, and have shown that these factors determine the magnitude of PMN sequestration in the pulmonary microvessels (6, 18, 27, 30).…”

“…Stimuli such as peptide chemoattractants, endotoxin, and smoking are known to decrease PMN deformability and further increase the concentration of PMN in pulmonary capillaries (6,18,27,30). Several in vitro filtration studies have measured the biophysical properties of PMN, particularly their size and deformability, and have shown that these factors determine the magnitude of PMN sequestration in the pulmonary microvessels (6, 18, 27, 30).…”

L-selectin is required for fMLP- but not C5a-induced margination of neutrophils in pulmonary circulation

“…Although reduced neutrophil deformability on activation can cause sequestration (6,25,51), some components of this sequestration depend on adhesion molecules such as ␤ 2 integrins (6, 10), L-selectin (13,16), and ␣ 4 integrins (5).…”