Endothelial cytoskeleton and lung capillary integrity -
ultrastructural changes in response to botulinum c2 toxin.
Ermert, L., H. R. Duncker, H. Br[umlaut]uckner, F. Grimminger, T.
Hansen, R. R[diaeresis]ossi, K. Aktories, and W. Seeger.
Department of Internal Medicine, Justus-Liebig-University, Giessen,
35385 Giessen, and the Institute of Anatomy and Cellbiology, Justus
-Liebig-University, Giessen, 35385 Giessen, and the Institute of
Pharmacology and Toxicology, University of the Saarland, 66421
Homburg, Germany
APStracts 3:0474A, 1996.
The role of the actin microfilament system in endothelial cells for
the structural integrity of the pulmonary gas exchange area was
probed by use of Clostridium botulinum C2 toxin. This agent causes
selective loss of non-muscle F-actin. Buffer-perfused rabbit lungs
were used, in which the vascular pressures varied within
physiological ranges. Group A (n=3) included control lungs, buffer
-perfused for 180 min. Group B lungs (n=3) were poisoned with low-dose
C2 toxin (0.3/0.6 ng/ml C2I/II in the buffer fluid; n=3), and
experiments were terminated after a total weight gain due to edema
accumulation of 7.5 g (122 +/- 16 min). Lungs of groups C and D were
exposed to high-dose C2 toxin (10/20 ng/ml C2I/II; n=3 each), and
perfusion was stopped after a total weight gain of 1 g (16 +/- 3 min;
C) and 7.5 g (38 +/- 6 min; D). Perfusion fixation for electron
-microscopic evaluation was performed immediately after cessation of
buffer circulation. Group A lungs did not gain weight and displayed
normal lung architecture. In low-dose C2 toxin-treated lungs (B),
extensive attenuations, undulations and protrusions of the
endothelial layer were noted, suggestive of "remodeling"
and "flowing" of the cell membranes. These were accompanied
by few disruptions of the endothelial layer, edema formation in the
vicinity of these lesions as well as vesiculation and bleb formation
of endothelial cells. Lungs that were exposed for short-term periods
to the high toxin doses (C, D) again displayed marked attenuations of
the endothelial layer, including both the thin and the thick side of
the septal capillary walls, in addition to large endothelial cell
disruptions, particularly in group D. These lesions did not include
interendothelial junctions, although they were often located adjacent
to them in any of the C2 toxin-treated lungs. Significant
ultrastructural changes of interstitial cells and epithelial type-I
cells were not seen, interestingly type-II epithelial cells displayed
fusion of lamellar bodies. Collectively, these data suggest that the
actin microfilament system is instrumental in supporting endothelial
cell membrane configuration and integrity and maintains the intimal
barrier function of the lung microvasculature.
Received 13 February 1996; accepted in final form 4 September
1996.
APS Manuscript Number A150-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996