Pulmonary microvascular injury induced by Pseudomonas aeruginosa cytotoxin in isolated rabbit lungs

Abstract

The effects of Pseudomonas aeruginosa cytotoxin on the pulmonary microvasculature were studied in blood-free, perfused, isolated rabbit lungs. Cytotoxin was administered to the recirculating Krebs Henseleit albumin (1%) buffer during two consecutive 30-min-perfusion phases (phases 1 and 2) at a concentration of 13 ,ug/ml, followed by a third perfusion phase (phase 3) without toxin. After perfusion phases 2 and 3, the capillary filtration coefficient (Kf,c) and vascular compliance were determined gravimetrically from two-step microvascular pressure increments under zero-flow conditions. Cytotoxin caused a continuous release of K+ and lactate dehydrogenase, which started within the first 5 min and amounted to about 50% of the total lung cellular K+ and 5 to 7% of the total lactate dehydrogenase by the end of the experiment. The toxin caused the continuous generation of prostaglandin 12, which was detectable in the perfusates of all perfusion phases at maximum values five times above the control values and which was measured in the bronchoalveolar lavage fluid at the end of the experiment. Thromboxane generation in toxin-treated lungs did not significantly exceed that of control lungs or of lungs with mechanically induced edema. Cytotoxin caused a gradual increase in pulmonary vascular resistance, to maximum values 2.5 times above the control, starting within 1 min; the increase was partially reversible after washout of the toxin. After a lag period of 20 to 30 min, the lungs gained weight, amounting to a mean gain of 9.1 g at the end of the experiments. After perfusion phases 2 and 3, an almost fourfold increase in Kf1,, which was not reversible after washout of the toxin, was measured, whereas the values of vascular compliance were not altered. We conclude that pseudomonal cytotoxin may be an important factor in the pathogenesis of prolonged microvascular injury, encountered in states of P. aeruginosa sepsis or acute lung failure with secondarily acquired P. aeruginosa pneumonia.

Caspase-1 Activation Protects Lung Endothelial Barrier Function during Infection-Induced Stress

“…In our experimental model, the natural evolution of P. aeruginosa-induced pneumonia results in pulmonary epithelial and endothelial barrier disruption, interstitial and alveolar edema, and progression to acute lung injury (15,(21)(22)(23). Thus, we next examined the effects of caspase-1 inhibition on lung epithelial and endothelial barrier integrity, and lung function in response to P. aeruginosa infection.…”

Streptococcal Pyrogenic Exotoxin F (SpeF) Causes Permeabilization of Lung Blood Vessels

“…Induction of significant reactions in the rat lung model required approxi-mately 100 ng of purified SpeF in 1 ml of perfusion solution, a dose somewhat higher than those used for the induction of in vitro mitogenic activity by SpeF (16). Seeger and coworkers reported that several bacterial toxins including Escherichia coli hemolysin, Pseudomonas aeruginosa cytotoxin, and Staphylococcus aureus ␣-toxin induce lung vascular permeabilization in an isolated perfused rabbit lung model, very similar to the rat model used in this study; they showed that these toxins play important roles in the pathogenesis of ARDS caused by bacterial infections (1,21,24). SpeF may be a crucial factor for onset of ARDS during severe infection or TSLS caused by S. pyogenes.…”

“…There are a few possible mechanisms which would explain rat lung vascular permeabilization by SpeF. One is that mentioned by Seeger et al (1,21,24): SpeF would form pores on lung vascular endothelial cells and then causes sequential events which trigger arachidonic acid cascades and consequently causes lung vascular permeabilization. However, this is unlikely, because so far there is no evidence that SpeF has pore-forming ability.…”

Isolation and characterization of a transposon-induced cytotoxin-deficient mutant of Pseudomonas aeruginosa

“…It was first described by Scharmann (39) and originally called leukocidin because it had cytotoxic effects on leukocytes (40). It has since been shown to cause cytopathic effects in most types of eukaryotic cells by interacting with cell membranes (3,6,15,16,41,45). A survey of P. aeruginosa clinical isolates showed that all isolates produce cytotoxin (5), and its importance in pathogenesis is suggested by its cytotoxicity and the observation that patients with chronic P. aeruginosa infections have elevated levels of anticytotoxin antibodies (Sa).…”