Am. J. Respir. Crit. Care Med., Vol 150, No. 2, Aug 1994, 455-461.
The role of cytoskeletal proteins in neutrophil emigration during pneumonia in rabbits
GA Mueller, WM Quinlan, NA Doyle and CM Doerschuk
Herman B. Wells Center for Pediatric Research, Department of Pediatrics, Indiana University, Indianapolis.
The cytoskeletal proteins, actin and tubulin, are critical in modulating
many aspects of the structural, mechanical, and biochemical properties of
cells. This study determined if rearrangements of microtubules or
filamentous actin were necessary for neutrophil margination within the
pulmonary microvasculature or emigration into the alveolar spaces in
response to Streptococcus pneumoniae. Microtubule assembly was inhibited
using colchicine, and F-actin depolymerization was inhabited using
phalloidin. Anesthetized rabbits received an intrabronchial instillation of
S. pneumoniae either after intravenous pretreatment with colchicine (1
mg/kg every 2 h) or combined with TRITC-phalloidin (2 microM in
instillate). Four hours later, the lungs were fixed and removed. The
results show that the intravenous injection of colchicine caused a rapid
decrease in circulating neutrophil counts, most likely caused by
sequestration within the pulmonary microvasculature, that gradually
recovered. In the pneumonic region, colchicine inhibited neutrophil
emigration by 74 +/- 5%, but it did not prevent the stimulus-induced
increase in margination. Phalloidin inhibited neutrophil emigration by 83
+/- 4%. These studies suggested that microtubule reassembly occurs during
neutrophil transit through the normal pulmonary microvasculature and that
it is required for migration but not sequestration during pneumonia.
Rearrangement of actin filaments in lung cells but not neutrophils are
required for neutrophil emigration induced by S. pneumoniae.
