Erzurum S C, Downey G P, Doherty D E, Schwab B, Elson E L, Worthen G S
Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
J Immunol. 1992 Jul 1;149(1):154-62.
Intravascular LPS rapidly induces neutrophil sequestration in pulmonary capillaries by mechanisms that, although currently unknown, must take into account the size difference between the neutrophil and capillary diameter. To determine whether LPS alters neutrophil stiffness, and hence the ability of neutrophils to traverse capillaries, neutrophil passage through pulmonary capillaries was modeled by passage through filters with 6.5-microns pores. LPS increased retention in the pores in a concentration-dependent fashion that required the presence of heat-inactivated platelet-poor plasma, and was evident as early as 10 min after stimulation. The effect of LPS on the structural properties of the neutrophil was then studied. LPS induced f-actin reorganization in neutrophils in the presence of plasma. Disruption of actin organization and assembly with cytochalasin D completely inhibited early LPS-induced retention and attenuated retention at later timepoints, indicating that LPS-stimulated retention depends on filament organization. LPS-induced actin assembly and retention were abrogated by an antibody directed against CD14, a putative LPS receptor. CD18-dependent adherence of neutrophils contributed significantly to retention only at later timepoints with no significant contribution to retention at 20 min as determined by inhibition of adherence with the mAb 60.3. Morphometric assessment of neutrophil accumulation in the lungs of rabbits given 1 microgram LPS showed a marked increase in apparent neutrophil number, which was unaltered by antibodies to CD18, suggesting that mechanisms other than adhesion may account for accumulation in vivo. Direct measurements showed that neutrophil stiffness increased with exposure to LPS in a fashion similar to LPS-induced retention and actin organization. Pretreatment of neutrophils with cytochalasin D attenuated the increased stiffness. These data suggest that reorganization of filamentous-actin induced by LPS leads to cell stiffening and retention in capillary-sized pores. Although the organization of f-actin continues to be important in retention at later time points, adherence of cells also contributes significantly to cell retention. The changes in mechanical properties of the neutrophil may be important in the sequestration of neutrophils in pulmonary capillaries noted in endotoxemia.
血管内脂多糖（LPS）通过目前尚不清楚的机制迅速诱导中性粒细胞在肺毛细血管中滞留，这些机制必须考虑到中性粒细胞与毛细血管直径之间的大小差异。为了确定LPS是否会改变中性粒细胞的硬度，从而影响中性粒细胞穿越毛细血管的能力，通过使中性粒细胞通过孔径为6.5微米的滤器来模拟其在肺毛细血管中的通过情况。LPS以浓度依赖的方式增加了在孔中的滞留，这需要热灭活的少血小板血浆的存在，并且早在刺激后10分钟就很明显。然后研究了LPS对中性粒细胞结构特性的影响。LPS在有血浆存在的情况下诱导中性粒细胞中的丝状肌动蛋白（f-肌动蛋白）重组。用细胞松弛素D破坏肌动蛋白的组织和组装完全抑制了LPS早期诱导的滞留，并在后期减弱了滞留，表明LPS刺激的滞留依赖于细丝组织。针对假定的LPS受体CD14的抗体消除了LPS诱导的肌动蛋白组装和滞留。中性粒细胞的CD18依赖性黏附仅在后期对滞留有显著贡献，通过用单克隆抗体60.3抑制黏附来确定，在20分钟时对滞留没有显著贡献。对给予1微克LPS的兔子肺部中性粒细胞聚集的形态计量学评估显示，明显的中性粒细胞数量显著增加，这不受抗CD18抗体的影响，表明除黏附之外的机制可能解释体内的聚集。直接测量表明，中性粒细胞的硬度随着暴露于LPS而增加，其方式类似于LPS诱导的滞留和肌动蛋白组织。用细胞松弛素D预处理中性粒细胞可减弱硬度的增加。这些数据表明，LPS诱导的丝状肌动蛋白重组导致细胞变硬并滞留在毛细血管大小的孔中。尽管f-肌动蛋白的组织在后期滞留中仍然很重要，但细胞黏附也对细胞滞留有显著贡献。中性粒细胞机械性能的变化在内毒素血症中所观察到的中性粒细胞在肺毛细血管中的滞留中可能很重要。
