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.
The effect of alpha 1-proteinase inhibitor (alpha 1Pi) administration on the acute lung injury and subsequent fibrosis induced by bleomycin (BLM) was examined in hamsters. Pulmonary lesions were quantitatively reduced in alpha 1Pi-administered BLM-treated (BLM-alpha 1Pi) animals compared with animals treated by BLM alone (BLM-control) at both 7 days (acute stage) and 30 days (fibrotic stage) after BLM treatment. Analysis of intraalveolar cells from bronchoalveolar lavage (BAL) fluid revealed that neutrophils and lymphocytes were significantly decreased in the BLM-alpha 1Pi animals at 7 days after BLM treatment and that 30 days after BLM treatment macrophages as well as neutrophils and lymphocytes were remarkably decreased in the BLM-alpha 1Pi animals. The elastase activity in supernatants of BAL fluid during 7 days following BLM treatment was detected, but there was no difference between the two groups. In vitro studies on neutrophil responsiveness to stimulation of BAL fluid at 3 days after BLM treatment revealed noticeable chemotaxis and generation of superoxide anion of isolated neutrophils, but alpha 1Pi did not show any inhibitory effects on neutrophil responsiveness. We suggest that alpha 1Pi administration ameliorates pulmonary fibrosis preceded by acute lung injury induced by BLM treatment in hamsters and that the inhibitory effects of alpha 1Pi on lung injury may not be brought about by altered elastase activity, chemotaxis, or superoxide generation in neutrophils. Alternative mechanisms are discussed.
We quantitated the holes in alveolar walls in 11 nonemphysematous lungs and in 11 lungs with mild emphysema, all of which were removed at surgery. We found that in the nonemphysematous lungs, 94.1% of the holes were smaller than 10 microns in diameter and only 0.2% were larger than 20 microns. In the lung parenchyma distant from emphysema, both the maximum diameter of the holes and the diameter of alveoli increased. In the parenchyma between emphysema, the areas of alveolar walls represented by holes also increased, as did the average hole area and number of holes per alveolus. We found that alveolar holes in the regions between emphysema correlated better with pulmonary function tests than did those in regions distant from emphysema. The maximum diameter of holes and the number of holes per alveolus correlated with functional residual capacity, residual volume, closing capacity expressed as a proportion of total lung capacity (CC/TLC), and static recoil pressure of the lung at TLC. Emphysema correlated with CC/TLC and with the transpulmonary pressure at 90% TLC. Bronchiolar lesions were not related to pulmonary function tests. Our data provide support for the hypothesis that the tissue surrounding emphysematous lesions contributes to loss of recoil.
The effects of intravenous injection of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on circulating neutrophil numbers, pulmonary vascular permeability, and morphologic changes in the lung were examined in rabbits. Intravenous injection of rhG-CSF caused a rapid, profound neutropenia due to neutrophil sequestration primarily within capillaries but also in larger microvessels of the lungs. Examination of neutrophil deformability using microfilters revealed that granulocyte colony-stimulating factor (G-CSF) treatment caused a rapid stiffening of neutrophils through the polymerization of F-actin but not microtubule assembly. The expression of CD11b, CD11c, and CD18 on human neutrophils after G-CSF treatment increased, but CD11a did not. Intravenous injection of rhG-CSF did not induce neutrophil emigration or albumin leakage into alveolar space, wet/dry lung weight ratios were unchanged, and no pathologic changes in lung histology were observed. These studies indicate that injection of rhG-CSF caused a rapid neutropenia and neutrophil sequestration in the lungs that is likely to be mediated through a G-CSF-induced decrease in neutrophil deformability, although neutrophil-endothelial cell adhesion may also play a role. However, this G-CSF-induced neutrophil sequestration did not induce a massive lung injury.
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