Volume 1 Supplement 1
Pathogenesis of organ damage during sepsis. In vitro influence of lipopolysaccharides and cytokines on the microtubular system
© Current Science Ltd 1997
Published: 1 March 1997
Lipopolysaccharides (endotoxins) from Gram-negative bacteria and septic mediators like interleukins or TNF-α are known to be involved in the pathogenesis of septic shock and multi-organ failure. Whether this is due to tissue hypoxia by alterations of the microcirculatory blood flow or by direct cytotoxic effects is controversial.
Microtubules are long, non-branching hollow-cylindric proteinaceous organelles found in almost all eukaryotic cells. Their wall consists of protofilaments (mostly 13), composed of longitudinally associated ab-tubulin dimers. Microtubules are involved in the maintenance of cell shape, translocation of cytoplasmic organelles, and secretory and signal transfer processes.
In the present work, we have studied the effect of different lipopolysaccharides (Klebsiella pneumoniae, E coli, Pseudomonas aeruginosa and Salmonella minnesota) and cytokines (IL-1β, IL-6, IL-10 and TNF-α) on polymerization of microtubulc protein and on structure of preformed microtubules in vitro. There was a time-, pH- and concentration-dependent inhibition of microtubule formation with respect to lipopolysaccharides, but not to cytokines. The strongest effects were observed with lipopolysaccharides from Pseudomonas aeruginosa (at pH 7.0, 37°C, 50 μg/ml LPS, 20 min, about 55% inhibition; n = 3) and Salmonella minnesota (at pH 7.0, 37°C, 50 μg/ml, 20 min, about 62% inhibition, n = 3). Incubation with lipopolysaccharides leads to a marked breakdown of preformed microtubules. Electron microscopy showed that incubation of preformed microtubules with LPS leads to disrupted microtubule structures, too. The inhibiting influence of LPS on polymerization of microtubule protein could be compensated by addition of purified MAP-2 and tau. By electrophoretic analysis it was shown that LPS prevents MAP-1, MAP-2 and tau from interaction with tubulin.
The results indicate that the microtubule cytoskeleton and above all microtubule associated proteins could be a major target of direct cellular effects of lipopolysaccharides, but not of cytokines.
Supported by Deutsche Forschungsgemeinschaft Re 653/5-1 and Thuringian Ministry of Science, Research and Culture F 3.1-908/7-143.