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Simvastatin, ein HMG-CoA-Reduktase-Inhibitor, wird im klinischen Alltag zur Senkung des Cholesterin-Spiegels eingesetzt. Darüber hinaus berichteten aktuelle Studien über protektive Eigenschaften von Statinen unter inflammatorischen Bedingungen. In dieser Studie wurden die Effekte von Simvastatin auf die Leukozyten-vermittelte Schädigung nach Stimulation mit Staphylococcus aureus alpha-Toxin untersucht. Aortale Gefäßsegmente von Ratten, vorbehandelt mit NaCl oder Simvastatin (100 μg/kg) intraperitoneal appliziert, wurden isoliert. Die Gefäßsegmente wurden mit Staphylococcus aureus alpha-Toxin (0,1–1 μg/ml) aktiviert und die PMN-Adhäsion quantifiziert. Zusätzlich wurde in der Organbadanlage die PMN-induzierte Vasokontraktion und endotheliale Dysfunktion untersucht. Die Adhäsion von PMN an das vaskuläre Endothel wurde durch die Stimulation mit alpha-Toxin signifikant gesteigert. Die Vorbehandlung mit Simvastatin führte zu einer signifikant geringeren Adhäsion nach alpha-Toxin Stimulation (p<0,05). Im Organbad führte die Inkubation von PMN mit Gefäßringen zu keiner Vasokontraktion bzw. endothelialen Dysfunktion. Nach Stimulation der Gefäßringe im Organbad mit alpha-Toxin 0,5 μg/ml und anschließender Koinkubation mit PMN (106Zellen/ml) zeigte sich eine signifikante Vasokontraktion (119±8 mg, p<0,05). Dies führte gleichzeitig zur deutlichen Einschränkung der endothelialen Relaxation in diesen Gefäßringen nach Acetylcholingabe (21±4% Relaxation, p<0,01). Die endotheliale Dysfunktion konnte in Gefäßringen von mit Simvastatin vorbehandelten Tieren in einem geringeren Ausmaß beobachtet werden (75±5% Relaxation, p<0,05). Auch die PMN-vermittelte Vasokontraktion zeigte sich in den Gefäßringen von Simvastatin vorbehandelten Tieren ebenfalls in einem deutlich geringeren Ausmaß. Die Ergebnisse dieser Untersuchung zeigen, dass Simvastatin die durch alpha-Toxin induzierten PMN-Endothel-Interaktionen an der Gefäßwand signifikant reduziert. Dadurch kommt es zu einer geringeren vaskulären Schädigung welche bei Patienten mit Sepsis oder Endokarditis von Bedeutung sein könnte. Die Zukunft wird zeigen, ob Statine eine therapeutische Anwendung auch zur Reduktion vaskulärer Schädigungen durch bakterielle Toxine finden.

Polymorphonuclear leukocytes (PMN) are essential for resolution of infections with Listeria monocytogenes. The present study investigated the role of the listerial exotoxins listeriolysin (LLO) and phosphatidylinositol-specific phospholipase C (PlcA) in human neutrophil activation. Different Listeria strains, mutated in individual virulence genes, as well as purified LLO were used. Coincubation of human neutrophils with wild-type L. monocytogenes provoked PMN activation, occurring independently of phagocytosis events, with concomitant elastase secretion, leukotriene generation, platelet-activating factor (PAF) synthesis, respiratory burst, and enhanced phosphoinositide hydrolysis. Degranulation and leukotriene formation were noted to be solely dependent on LLO expression, as these features were absent when the LLO-defective mutant EGD- and the avirulent strain L. innocua were used. These effects were fully reproduced by a recombinant L. innocua strain expressing LLO (INN+) and by the purified LLO molecule. LLO secretion was also required for PAF synthesis. However, wild-type L. monocytogenes was more potent in eliciting PAF formation than mutants expressing LLO, suggesting the involvement of additional virulence factors. This was even more obvious for phosphoinositide hydrolysis and respiratory burst: these events were provoked not only by INN+ but also by the LLO-defective mutant EGD- and by a recombinant L. innocua strain producing listerial PlcA. We conclude that human neutrophils react to extracellularly provided listerial exotoxins by rapid cell activation. Listeriolysin is centrally involved in triggering degranulation and lipid mediator generation, and further virulence factors such as PlcA apparently contribute to trigger neutrophil phosphoinositide hydrolysis and respiratory burst. In this way, listerial exotoxins may influence the host defense against infections with L. monocytogenes.

Botulinum C2 toxin, a binary toxin that ADP-ribosylates nonmuscle G-actin, was used as a selective tool to evaluate the role of actin-dependent cytoskeletal rearrangement in ligand-evoked lipid mediator generation. Human neutrophils (PMN) were preincubated with varying concentrations of the toxin for 30 min. Lipoxygenase products of arachidonic acid were measured by chromatographic techniques in the presence of exogenous arachidonic acid to probe PMN 5-lipoxygenase activity. Formation of platelet-activating factor (PAF) was assayed by the bioincorporation of [3H]acetate. Stimulation was performed with the soluble chemotactic ligands formyl-methionyl-leucyl-phenylalanine (FMLP) and PAF, as well as opsonized zymosan. PMN pretreatment with C2 toxin in the range between 200/400 and 800/1600 ng/ml C2I/II caused a dose-dependent suppression of the basal F-actin content and of stimulus-induced actin assembly. Phosphoinositide hydrolysis (measured as liberated inositol phosphates) and PAF generation in response to FMLP and exogenous PAF were markedly increased at these toxin doses. Minor C2 toxin concentrations (range, approximately 25/50 to 200/400 ng/ml C2I/II) were sufficient to amplify stimulus-induced formation of leukotriene B4 and its omega-oxidation products, nonenzymatic hydrolysis products of leukotriene A4, and 5-hydroxyeicosatetraenoic acid (5-HETE). With increasing toxin doses, leukotriene generation declined and 5-HETE became the predominant metabolite. In contrast to the soluble ligands, the zymosan-effected generation of PAF and leukotrienes was dose-dependently inhibited by C2 toxin concentrations of greater than 200/400 ng/ml, paralleled by a loss of motile and phagocytotic functions in these cells. We conclude that selective inhibition of actin assembly amplifies PAF and 5-lipoxygenase product formation in response to soluble chemoattractants with distinct dose dependences. The augmentation of PAF generation may be linked to amplified second messenger levels at higher doses of C2 toxin, whereas the sensitivity of the 5-lipoxygenase metabolism to low concentrations may indicate toxin effect on a small, functionally specified, actin pool. The present data support an important role of cytoskeletal rearrangement in temporal and/or spatial limitation of chemoattractant-evoked PMN activation.