Am. J. Respir. Cell Mol. Biol., Vol 16, No. 2, Feb 1997, 119-126.
Changes in mononuclear phagocyte microtubules after endotoxin stimulation. I. Changes in microtubule stability
JN Allen, SA Moore, Z Liao and MD Wewers
Division of Pulmonary and Critical Care Medicine, Ohio State University, Columbus, USA.
Microtubules are in a dynamic equilibrium of polymerization and
depolymerization. In monocytes and macrophages, microtubules bind endotoxin
and partly regulate inflammatory events such as cytokine production. To
characterize the morphologic differences between alveolar macrophage and
blood monocyte microtubules after LPS stimulation, cells were examined by
immunofluorescent microscopy and laser confocal microscopy. Fresh monocytes
contained an average of 26 microtubules per cell which significantly
increased to 31 microtubules per cell following a 30-min exposure to LPS (P
< 0.001). Using a nocodazole-based assay of microtubule dynamic
instability, the half- life of fresh unstimulated human monocyte
microtubules was approximately 18 s and extended to 26 s following a 30-min
exposure to LPS. In vitro maturation of monocytes for 18 h increased
microtubule stability but not number. Compared to monocytes, alveolar
macrophage microtubules were longer, more numerous, and much more stable.
These results suggest that alveolar macrophage microtubules are more
numerous and stable than blood monocyte microtubules and that LPS causes an
increase in monocyte microtubule number and stability.
