Christian Hofstetter

Protective Properties of Inhaled IL-22 in a Model of Ventilator-Induced Lung Injury

High-pressure ventilation induces barotrauma and pulmonary inflammation, thus leading to ventilator-induced lung injury (VILI). IL-22 has both immunoregulatory and tissue-protective properties. Functional IL-22 receptor expression is restricted to nonleukocytic cells, such as alveolar epithelial cells. When applied via inhalation, IL-22 reaches the pulmonary system directly and in high concentrations, and may protect alveolar epithelial cells against cellular stress and biotrauma associated with VILI. In A549 lung epithelial cells, IL-22 was able to induce rapid signal transducer and activator of transcription (STAT)-3 phosphorylation/activation, and hereon mediated stable suppressor of cytokine signaling (SOCS) 3 expression detectable even 24 hours after onset of stimulation. In a rat model of VILI, the prophylactic inhalation of IL-22 before induction of VILI (peak airway pressure = 45 cm H(2)O) protected the lung against pulmonary disintegration and edema. IL-22 reduced VILI-associated biotrauma (i.e., pulmonary concentrations of macrophage inflammatory protein-2, IL-6, and matrix metalloproteinase 9) and mediated pulmonary STAT3/SOCS3 activation. In addition, despite a short observation period of 4 hours, inhaled IL-22 resulted in an improved survival of the rats. These data support the hypothesis that IL-22, likely via activation of STAT3 and downstream genes (e.g., SOCS3), is able to protect against cell stretch and pulmonary baro-/biotrauma by enhancing epithelial cell resistibility.

Anti‐inflammatory effects of sevoflurane and mild hypothermia in endotoxemic rats

Background:  Volatile anesthetics and hypothermia attenuate the inflammatory response. We aimed to compare the anti‐inflammatory effects of sevoflurane and mild hypothermia during experimental endotoxemia in the rat.

The beta-adrenoceptor antagonist propranolol counteracts anti-inflammatory effects of isoflurane in rat endotoxemia

Background:  Recent studies suggest that volatile anaesthetics have anti‐inflammatory and preconditioning properties and that beta‐adrenoceptors are involved in the signalling pathways for these effects. Concurrently, the blockade of beta‐adrenoceptors has been shown to augment the release of inflammatory mediators in response to pro‐inflammatory stimuli. We therefore aimed to investigate whether the beta‐adrenoceptor antagonist propranolol might modulate the anti‐inflammatory effects of isoflurane on the systemic and pulmonary release of pro‐inflammatory cytokines in endotoxemic rats.

Cecal Ligation and Incision: An Acute Onset Model of Severe Sepsis in Rats

BACKGROUND Sepsis is a leading cause of death among critically ill patients. Up to now, severe sepsis with acute onset in animals has been induced mainly through injection of single bacteria species or endotoxin and not through a surgical procedure, which might adequately mirror the situation in septic patients. We therefore aimed to establish a surgical model of severe sepsis in rodents fulfilling international sepsis criteria. MATERIALS AND METHODS Twenty-eight anesthetized/ventilated Sprague Dawley rats underwent laparotomy and cecal mobilization. The cecum was either replaced into the abdomen (SHAM, n = 14) or the cecum and the mesenteric blood vessels were ligated, and the cecum was opened through a 1.5 cm blade incision (cecal ligation and incision, CLI, n = 14). RESULTS Within 390 min, mortality was 0% (SHAM) and 50% (CLI), respectively. Compared with SHAM, CLI resulted in a 43% reduction of mean arterial blood pressure and in severe metabolic acidosis as measured by arterial base excess and pH. CLI led to a 15-fold increase in mononuclear cell population and to a 5-fold accumulation of nitrite in peritoneal lavage. Abdominal swabs from the Douglas cavity in CLI-animals showed gram-positive and gram-negative bacterial growth on agar compared with sterile swabs from SHAM-animals. In CLI-animals, plasma IL-1beta level was increased to 435 pg/mL (SHAM: 10 pg/mL) and plasma IL-6 level to 19718 pg/mL (SHAM: 832 pg/mL). CONCLUSIONS CLI causes bacterial peritonitis with subsequent systemic inflammation and organ dysfunction. Thus, CLI mimics clinical sepsis and provides a surgical short term model of severe sepsis in rodents.

Isoflurane Inhalation after Induction of Endotoxemia in Rats Attenuates the Systemic Cytokine Response

Background/Aims: Volatile anesthetics are frequently utilized in clinical routine. Isoflurane has been shown to attenuate the response to inflammatory stimuli such as lipopolysaccharide (LPS) when administered before induction of endotoxemia. We aimed therefore to evaluate the effect of isoflurane after administration of LPS on the cytokine release as a therapeutic option. Materials and Methods:21 male Sprague-Dawley rats were randomly assigned to the following groups: animals that received LPS (5 mg/kg, i.v.) without further intervention (LPS group), animals that received continuous inhalation of 1 minimum alveolar concentration (MAC) isoflurane 15 min after administration of LPS (Iso group) and no specific intervention (sham group). Four hours following LPS injection, plasma levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6 and IL-10 were determined. Furthermore, nitrite release from cultured alveolar macrophages was analyzed. Results: Inhalation of isoflurane after induction of endotoxemia attenuated the release of TNF-α (–52%, p < 0.05) and IL-1β (–39%, p < 0.05) as compared to the LPS group, while IL-6 and IL-10 levels were not significantly altered. Nitrite release was significantly increased in the Iso group as compared to the LPS group (+115%, p < 0.05). Conclusion: Inhalation of 1 MAC isoflurane after induction of endotoxemia in rats attenuates the systemic release of proinflammatory cytokines and concurrently enhances the production of nitrite in cultured alveolar macrophages.

Inhaled levosimendan reduces mortality and release of proinflammatory mediators in a rat model of experimental ventilator-induced lung injury.

Objectives:Mechanical ventilation during critical care can cause structural and functional disturbances in the lung with subsequent release of proinflammatory mediators, termed ventilator-induced lung injury (VILI). VILI progressively provokes decreased efficiency of gas exchange with subsequent hypoxic pulmonary vasoconstriction leading to cardiopulmonary alterations, such as pulmonary hypertension and right heart failure. We therefore aimed to evaluate whether inhalation therapy with levosimendan, a calcium-sensitizer with pulmonary vasodilating properties, could attenuate VILI and improve short-term survival in a rat experimental model. Design:Experimental animal model. Setting:University hospital. Subjects:Forty male Sprague-Dawley rats. Interventions:Rats were randomly treated as follows (n = 8, each group): 1) inhalation of the solvent only before induction of VILI, no further intervention; 2) inhalation of 240 &mgr;g of levosimendan before VILI induction; 3) inhalation of 24 &mgr;g of levosimendan before VILI induction; 4) intravenous administration of 24 &mgr;g/kg levosimendan before VILI induction; 5) control group with surgical preparation only. All groups were observed for 4 hrs. Measurements and Main Results:After 4 hrs following induction of VILI, levels of interleukin-1&bgr; and macrophage inflammatory protein-2 in plasma and bronchoalveolar lavage fluid were analyzed by enzyme-linked immunosorbent assay. Nitric oxide release from alveolar macrophages was measured by Griess assay. Content of matrix metalloproteinase-2 and matrix metalloproteinase-9 in bronchoalveolar lavage fluid was analyzed by gelatin zymography. Inhalation of 240 &mgr;g of levosimendan significantly improved survival after 4 hrs and mean arterial blood pressure compared with VILI only. Additionally, inhalation of 240 &mgr;g and infusion of 24 &mgr;g/kg levosimendan significantly reduced the release of interleukin-1&bgr;, the nitric oxide release from alveolar macrophages, macrophage inflammatory protein-2 in plasma, and the macrophage inflammatory protein-2 and matrix metalloproteinase-9 content in bronchoalveolar lavage fluid compared with VILI only. Conclusions:Our study demonstrates that prophylactic inhalation of 240 &mgr;g of levosimendan improves survival and reduces release of inflammatory mediators in our experimental model of VILI. This might affect the clinical prophylaxis and treatment of VILI.

Dexamethasone suppresses interleukin-22 associated with bacterial infection in vitro and in vivo

Interleukin (IL)‐22 production triggered by innate immune mechanisms has been identified as key to efficient intestinal anti‐bacterial host defence and preservation of homeostasis. We hypothesized that glucocorticoid therapy may impair IL‐22 expression, which should promote intestinal epithelial damage with the potential of subsequent bacterial translocation. High‐dose corticosteroid therapy in Crohns disease has been associated with an increased rate of abscess formation and ultimately with a higher risk of developing postoperative infectious complications, including abdominal sepsis. Thus, we sought to investigate effects of the prototypic glucocorticoid dexamethasone on IL‐22 production in the context of bacterial infection. Enhanced IL‐22 plasma levels were detectable in rat sepsis. Moreover, heat‐inactivated Staphylococcus epidermidis, used as a prototypic activator of innate immunity, induced robust production of IL‐22 by human peripheral blood mononuclear cells (PBMC). Here, we report for the first time that dexamethasone mediates remarkable suppression of IL‐22 as detected in S. epidermidis‐activated PBMC and rat sepsis, respectively. The data presented herein suggest that insufficient IL‐22 function may contribute to impaired intestinal host defence in the context of corticosteroid therapy.

Efficacy of inhaled prostanoids in experimental pulmonary hypertension.

OBJECTIVES To evaluate the effects of inhaled prostacyclin (PGI2) and inhaled as well as intravenous prostaglandin E1 (PGE1) on thromboxane A2 mimetic-induced pulmonary vasoconstriction. Active pulmonary vasoconstriction was to be distinguished from passive resistance to blood flow. DESIGN Prospective, randomized, crossover study. SETTING Experimental animal laboratory. SUBJECTS Eight anesthetized and paralyzed sheep. INTERVENTIONS The stable thromboxane A2 mimetic, U46619, was infused in increasing dosage to obtain a stable pulmonary hypertension of approximately 30 mm Hg. Subsequently, PGE1 aerosol (0.6, 6, 58, 259 ng/kg/min), intravenous PGE, (0.5 microg/kg/min), or PGI2 aerosol (27 ng/kg/min) were administered in randomized order. MEASUREMENTS AND MAIN RESULTS Active pulmonary vasoconstriction was assessed by determining the pulmonary pressure-flow relationship (PPFR). For measurement of pulmonary artery flow, an ultrasound flow probe was placed around the pulmonary artery after a sternotomy. Pulmonary arterial pressure was measured with a pulmonary artery flotation catheter. Flow was varied by partial occlusion of the inferior vena cava or incremental opening of an arterio-venous fistula between the large neck vessels. The primary end points were the slope of the resulting linear pressure-flow relationship, and pulmonary vascular resistance (PVR). Infusion of U46619 increased the slope of the PPFR (2.9+/-0.7 vs. 4.2+/-1.2 mm Hg/L/min [median+/-semi-interquartile range]; p < or = .05), and PVR (221+/-20 vs. 424+/-57 dyne x sec/cm5) (p < .05). Neither dose of PGE1 aerosol induced changes of the slope of PPFR or PVR. In contrast, intravenous administration of the same drug reduced the slope of the PPFR (4.0+/-1.0 vs. 3.1+/-0.4) (p < .05) but left PVR unchanged. Inhalation of PGI2 reduced both the slope of the PPFR, slightly but significantly, and PVR (424+/-98 vs. 323+/-26 dyne x sec/cm5) (p < .05). CONCLUSIONS This study is the first to show reduction of active pulmonary vasoconstriction by PGI2 aerosol. Neither inhalation nor intravenous administration of PGE1 reduced PVR but the latter reduced the slope of PPFR. We conclude that PGE1 has potential for pulmonary vasodilation, but that it is ineffective as an aerosol, even in high doses, in sheep. PVR may fail to reflect drug-induced pulmonary vasodilation.

Inhaled IL-10 reduces biotrauma and mortality in a model of ventilator-induced lung injury

BACKGROUND High-pressure ventilation induces barotrauma and pulmonary inflammation, thus leading to ventilator-induced lung injury (VILI). By limiting the pulmonal inflammation cascade the anti-inflammatory cytokine interleukin (IL)-10 may have protective effects. Via inhalation, IL-10 reaches the pulmonary system directly and in high concentrations. METHODS Thirty six male, anesthetized and mechanically ventilated Sprague-Dawley rats were randomly assigned to the following groups (n=9, each): SHAM: pressure controlled ventilation with p(max)=20cmH(2)O, PEEP=4; VILI: ventilator settings were changed for 20min to p(max)=45cmH(2)O, PEEP=0; IL-10(high): inhalation of 10microg/kg IL-10 prior to induction of VILI; and IL-10(low): inhalation of 1microg/kg IL-10 prior to induction of VILI. All groups were ventilated and observed for 4h. RESULTS High-pressure ventilation increased the concentrations of macrophage inflammatory protein (MIP)-2 and IL-1beta in bronchoalveolar lavage fluid (BALF) and plasma. This effect was reduced by the inhalation of IL-10 (10microg/kg). Additionally, IL-10 increased the animal survival time (78% vs. 22% 4-h mortality rate) and reduced NO-release from ex vivo cultured alveolar macrophages. Moreover, VILI-induced pulmonary heat shock protein-70 expression was reduced by IL-10 aerosol in a dose-dependent manner. Similarly, the activation of matrix metalloproteinase (MMP)-9 in BALF was reduced dose-dependently by IL-10. IL-10-treated animals showed a lower macroscopic lung injury score and less impairment of lung integrity and gas exchange. CONCLUSIONS Prophylactic inhalation of IL-10 improved survival and reduced lung injury in experimental VILI. Results indicate that this effect may be mediated by the inhibition of stress-induced inflammation and pulmonary biotrauma.

AEROSOL DELIVERY DURING MECHANICAL VENTILATION TO THE RAT

□ The authors have adjusted a jet nebulizer to a mechanical ventilator (Servo Ventilator, Siemens) to deliver an aerosol to rats. They aimed to clarify whether a modified jet nebulizer generating particles with a mass median aerodynamic diameter of 2 µm would be effective and safe in intubated ventilated rats. Fluorescent microspheres (diameter: 1.0 µm) were aerosolized to verify qualitatively and quantitatively intrapulmonary deposition. Particle deposition fraction was 3.8% (1.3%) of the delivered dose (median [interquartile range]). There was no evidence for any adverse event as assessed from heart rate, mean arterial pressure, PaO2 and PaCO2 before, during, and after nebulization. No pulmonary tissue trauma was detected histologically.