Koen van der Sluijs

Effects on Coagulation and Fibrinolysis Induced by Influenza in Mice With a Reduced Capacity to Generate Activated Protein C and a Deficiency in Plasminogen Activator Inhibitor Type 1

Influenza infections increase the risk of diseases associated with a prothrombotic state, such as venous thrombosis and atherothrombotic diseases. However, it is unclear whether influenza leads to a prothrombotic state in vivo. To determine whether influenza activates coagulation, we measured coagulation and fibrinolysis in influenza-infected C57BL/6 mice. We found that influenza increased thrombin generation, fibrin deposition, and fibrinolysis. In addition, we used various anti- and prothrombotic models to study pathways involved in the influenza-induced prothrombotic state. A reduced capacity to generate activated protein C in TMpro/pro mice increased thrombin generation and fibrinolysis, whereas treatment with heparin decreased thrombin generation in influenza-infected C57Bl/6 mice. Thrombin generation was not changed in hyperfibrinolytic mice, deficient in plasminogen activator inhibitor type-1 (PAI-1−/−); however, increased fibrin degradation was seen. Treatment with tranexamic acid reduced fibrinolysis, but thrombin generation was unchanged. We conclude that influenza infection generates thrombin, increased by reduced levels of protein C and decreased by heparin. The fibrinolytic system appears not to be important for thrombin generation. These findings suggest that influenza leads to a prothrombotic state by coagulation activation. Heparin treatment reduces the influenza induced prothrombotic state.

A short course of infusion of a hydrogen sulfide-donor attenuates endotoxemia induced organ injury via stimulation of anti-inflammatory pathways, with no additional protection from prolonged infusion.

Organ failure is associated with increased mortality and morbidity in patients with systemic inflammatory response syndrome. Previously, we showed that a short course of infusion of a hydrogen sulfide (H(2)S) donor reduced metabolism with concurrent reduction of lung injury. Here, we hypothesize that prolonged H(2)S infusion is more protective than a short course in endotoxemia with organ failure. Also, as H(2)S has both pro- and anti-inflammatory effects, we explored the effect of H(2)S on interleukin production. Endotoxemia was induced by an intravenous bolus injection of LPS (7.5mg/kg) in mechanically ventilated rats. H(2)S donor NaHS (2mg/kg) or vehicle (saline) was infused and organ injury was determined after either 4 or 8h. A short course of H(2)S infusion was associated with reduction of lung and kidney injury. Prolonged infusion did not enhance protection. Systemically, infusion of H(2)S increased both the pro-inflammatory response during endotoxemia, as demonstrated by increased TNF-α levels, as well as the anti-inflammatory response, as demonstrated by increased IL-10 levels. In LPS-stimulated whole blood of healthy volunteers, co-incubation with H(2)S had solely anti-inflammatory effects, resulting in decreased TNF-α levels and increased IL-10 levels. Co-incubation with a neutralizing IL-10 antibody partly abrogated the decrease in TNF-α levels. In conclusion, a short course of H(2)S infusion reduced organ injury during endotoxemia, at least in part via upregulation of IL-10.

Traumatic Brain Injury in Rats Induces Lung Injury and Systemic Immune Suppression

Traumatic brain injury (TBI) is frequently complicated by acute lung injury, which is predictive for poor outcome. However, it is unclear whether lung injury develops independently or as a result of mechanical ventilation after TBI. Further, TBI is strongly associated with the development of pneumonia, suggesting a specific vulnerability for the development of nosocomial infections in the lung after TBI. In this study, we evaluated whether indeed pulmonary injury and immune suppression develop spontaneously in an animal model of mild TBI (mTBI). TBI was induced in male PVG rats by closed-head trauma using a weight-drop device. Subsequently, we evaluated the effects of this on the lungs as well as on the excitability of the systemic immune system. Finally, we performed an experiment in which TBI was followed by induction of pneumonitis and evaluated whether TBI affects the severity of subsequent pneumonitis induced by intratracheal instillation of heat-killed Staphylococcus aureus. mTBI resulted in significant lung injury, as evidenced by pulmonary edema, protein leakage to the alveolar compartment, and increased concentrations of interleukin-1 and -6 in broncho alveolar lavage fluid (all p<0.05 vs. sham-treated animals). Further, after TBI, the release of tumor necrosis factor alpha was decreased when whole blood was stimulated ex vivo (p<0.05 TBI vs. sham), indicating systemic immune suppression. When TBI was followed by pneumonitis, the severity of subsequent pneumonitis was not different in rats previously subjected to TBI or sham treatment (p>0.05), suggesting that systemic immune suppression is not translated toward the pulmonary compartment in this specific model. We here show that during mild experimental TBI, acute pulmonary injury, as well as a decrease in the excitability of the systemic immune system, can be observed.

Intravenous S-ketamine does not inhibit alveolar fluid clearance in a septic rat model.

We previously demonstrated that intratracheally administered S-ketamine inhibits alveolar fluid clearance (AFC), whereas an intravenous (IV) bolus injection had no effect. The aim of the present study was to characterize whether continuous IV infusion of S-ketamine, yielding clinically relevant plasma concentrations, inhibits AFC and whether its effect is enhanced in acute lung injury (ALI) which might favor the appearance of IV S-ketamine at the alveolar surface. AFC was measured in fluid-instilled rat lungs. S-ketamine was administered IV over 6 h (loading dose: 20 mg/kg, followed by 20 mg/kg/h), or intratracheally by addition to the instillate (75 µg/ml). ALI was induced by IV lipopolysaccharide (LPS; 7 mg/kg). Interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant (CINC)-3 were measured by ELISA in plasma and bronchoalveolar lavage fluid. Isolated rat alveolar type-II cells were exposed to S-ketamine (75 µg/ml) and/or LPS (1 mg/ml) for 6 h, and transepithelial ion transport was measured as short circuit current (ISC). AFC was 27±5% (mean±SD) over 60 min in control rats and was unaffected by IV S-ketamine. Tracheal S-ketamine reduced AFC to 18±9%. In LPS-treated rats, AFC decreased to 16±6%. This effect was not enhanced by IV S-ketamine. LPS increased IL-6 and CINC-3 in plasma and bronchoalveolar lavage fluid. In alveolar type-II cells, S-ketamine reduced ISC by 37% via a decrease in amiloride-inhibitable sodium transport. Continuous administration of IV S-ketamine does not affect rat AFC even in endotoxin-induced ALI. Tracheal application with direct exposure of alveolar epithelial cells to S-ketamine decreases AFC by inhibition of amiloride-inhibitable sodium transport.

Antiviral effect of eosinophils in respiratory tract infection with influenza virus in mice

Rationale Previous studies in an acute house dust mite murine model of allergic asthma have shown that allergic mice have an improved antiviral response to infection with influenza (A/PR/8/34) compared to non-allergic mice as reflected by lower viral titres in the lung and decreased weight loss. These findings demonstrate that allergic mice are able to clear the infection faster. Interestingly, we observed a synergistically enhanced eosinophilic response in bronchoalveolar lavage (BAL) of these mice in response to the viral infection.