Ralph C. Schimmer

Anesthetic-induced improvement of the inflammatory response to one-lung ventilation.

Background:Although one-lung ventilation (OLV) has become an established procedure during thoracic surgery, sparse data exist about inflammatory alterations in the deflated, reventilated lung. The aim of this study was to prospectively investigate the effect of OLV on the pulmonary inflammatory response and to assess possible immunomodulatory effects of the anesthetics propofol and sevoflurane. Methods:Fifty-four adults undergoing thoracic surgery with OLV were randomly assigned to receive either anesthesia with intravenously applied propofol or the volatile anesthetic sevoflurane. A bronchoalveolar lavage was performed before and after OLV on the lung side undergoing surgery. Inflammatory mediators (tumor necrosis factor &agr;, interleukin 1&bgr;, interleukin 6, interleukin 8, monocyte chemoattractant protein 1) and cells were analyzed in lavage fluid as the primary endpoint. The clinical outcome determined by postoperative adverse events was assessed as the secondary endpoint. Results:The increase of inflammatory mediators on OLV was significantly less pronounced in the sevoflurane group. No difference in neutrophil recruitment was found between the groups. A positive correlation between neutrophils and mediators was demonstrated in the propofol group, whereas this correlation was missing in the sevoflurane group. The number of composite adverse events was significantly lower in the sevoflurane group. Conclusions:This prospective, randomized clinical study suggests an immunomodulatory role for the volatile anesthetic sevoflurane in patients undergoing OLV for thoracic surgery with significant reduction of inflammatory mediators and a significantly better clinical outcome (defined by postoperative adverse events) during sevoflurane anesthesia.

Alveolar macrophages regulate neutrophil recruitment in endotoxin-induced lung injury

BackgroundAlveolar macrophages play an important role during the development of acute inflammatory lung injury. In the present study, in vivo alveolar macrophage depletion was performed by intratracheal application of dichloromethylene diphosphonate-liposomes in order to study the role of these effector cells in the early endotoxin-induced lung injury.MethodsLipopolysaccharide was applied intratracheally and the inflammatory reaction was assessed 4 hours later. Neutrophil accumulation and expression of inflammatory mediators were determined. To further analyze in vivo observations, in vitro experiments with alveolar epithelial cells and alveolar macrophages were performed.ResultsA 320% increase of polymorphonuclear leukocytes in bronchoalveolar lavage fluid was observed in macrophage-depleted compared to macrophage-competent lipopolysaccharide-animals. This neutrophil recruitment was also confirmed in the interstitial space. Monocyte chemoattractant protein-1 concentration in bronchoalveolar lavage fluid was significantly increased in the absence of alveolar macrophages. This phenomenon was underlined by in vitro experiments with alveolar epithelial cells and alveolar macrophages. Neutralizing monocyte chemoattractant protein-1 in the airways diminished neutrophil accumulation.ConclusionThese data suggest that alveolar macorphages play an important role in early endotoxin-induced lung injury. They prevent neutrophil influx by controlling monocyte chemoattractant protein-1 production through alveolar epithelial cells. Alveolar macrophages might therefore possess robust anti-inflammatory effects.

Sevoflurane ameliorates gas exchange and attenuates lung damage in experimental lipopolysaccharide-induced lung injury.

Background:Acute lung injury is a common complication in critically ill patients. Several studies suggest that volatile anesthetics have immunomodulating effects. The aim of the current study was to assess possible postconditioning with sevoflurane in an in vivo model of endotoxin-induced lung injury. Methods:Rats were anesthetized, tracheotomized, and mechanically ventilated. Lipopolysaccharide (saline as control) was administered intratracheally. Upon injury after 2 h of propofol anesthesia, general anesthesia was continued with either sevoflurane or propofol for 4 h. Arterial blood gases were measured every 2 h. After 6 h of injury, bronchoalveolar lavage was performed and lungs were collected. Total cell count, albumin content, concentrations of the cytokines cytokine-induced neutrophil chemoattractant-1 and monocyte chemoattractant protein-1, and phospholipids were analyzed in bronchoalveolar lavage fluid. Expression of messenger RNA for the two cytokines and for surfactant protein B was determined in lung tissue. Histopathologic examination of the lung was performed. Results:Significant improvement of the ratio of oxygen tension to inspired oxygen fraction was shown with sevoflurane (mean ± SD: 243 ± 94 mmHg [32.4 kPa]) compared with propofol (88 ± 19 mmHg [11.7 kPa]). Total cell count representing effector cell recruitment as well as albumin content as a measure of lung permeability were significantly decreased in the sevoflurane–lipopolysaccharide group compared with the propofol–lipopolysaccharide group in bronchoalveolar lavage fluid. Expression of the cytokines protein in bronchoalveolar lavage fluid as well as messenger RNA in lung tissue was significantly lower in the sevoflurane–lipopolysaccharide group compared with the propofol–lipopolysaccharide group. Conclusions:Postconditioning with sevoflurane attenuates lung damage and preserves lung function in an in vivo model of acute lung injury.

Role of chemokines and cytokines in a reactivation model of arthritis in rats induced by injection with streptococcal cell walls.

Intraarticular injection of streptococcal cell wall (SCW) antigen followed by intravenous challenge results in a T cell‐mediated monoarticular arthritis in female Lewis rats. Initial studies showed that this reactivation response to intravenous SCW antigen is dependent on the presence of interleukin‐1 (IL‐1) and tumor necrosis factor α (TNF‐α) and that the early phase of swelling is neutrophil‐dependent. Neutrophil depletion or passive immunization with antibodies to P‐selectin or macrophage inflammatory protein‐2 reduced the intensity of ankle edema and the influx of neutrophils. After the first few days, however, the arthritic response is mediated primarily by mononuclear cells. Joint tissues showed up‐regulation of mRNA for monocyte chemotactic protein‐1 (MCP‐1), which could be inhibited in part by anti‐IL‐4; treatment of rats with antibodies to IL‐4 or MCP‐1 significantly suppressed development of ankle edema and histopathological evidence of inflammation. Antibodies to interferon‐γ or IL‐10 had no effect. Treatment with anti‐MCP‐1 also suppressed influx of 111In‐labeled T cells into the ankle joint. These data suggest that the late, mononuclear‐dependent phase of SCW‐induced arthritis in female Lewis rats requires cytokines that up‐regulate MCP‐1, which in turn may facilitate recruitment and extravasation of mononuclear cells into the joint. J. Leukoc. Biol. 63: 359–363; 1998.

Ropivacaine decreases inflammation in experimental endotoxin-induced lung injury.

Background: Endotoxin causes acute lung injury, which can lead to acute respiratory distress syndrome. Because local anesthetics are known to attenuate inflammatory reactions, ropivacaine was tested for its possible antiinflammatory effect in lipopolysaccharide-induced lung injury in rat alveolar epithelial cells (AECs) and rat pulmonary artery endothelial cells (RPAECs) in vitro and in vivo. Methods: AECs and RPAECs were stimulated for 4 h with lipopolysaccharide or lipopolysaccharide and 1 μM ropivacaine. Messenger RNA (mRNA) for intercellular adhesion molecule 1 was assessed. Isolated neutrophils were incubated with stimulated target cells to quantify adhesion and neutrophil-induced cytotoxicity in AECs and RPAECs. In vivo, lipopolysaccharide was instilled intratracheally with or without 1 mM intratracheally or intravenously administered ropivacaine. Bronchoalveolar lavage was performed 5 h later to determine neutrophil and albumin content, as well as concentrations of inflammatory mediators. Results: In AECs and RPAECs, ropivacaine attenuated lipopolysaccharide-induced up-regulation of mRNA for intercellular adhesion molecule 1 by 41% and 24%, respectively (P < 0.05). In the presence of ropivacaine, increased neutrophil adhesion was down-regulated by 58% and 44% (P < 0.005), whereas cytotoxicity in AECs and RPAECs was diminished by 28% and 33%, respectively (P < 0.05). Enhanced neutrophil count in lipopolysaccharide lungs was reduced by 56% in the presence of intratracheally instilled ropivacaine (81% with intravenous ropivacaine; P < 0.005). Albumin was decreased by 46% with intratracheal ropivacaine (38% with intravenous ropivacaine; P < 0.05), and inflammatory mediators were decreased by 48-59% (69-81% with intravenous ropivacaine; P < 0.01). Conclusions: Ropivacaine intervention substantially attenuated the inflammatory response in acute lung injury and thus may carry an interesting potential for antiinflammatory treatment.

Hypoxia aggravates lipopolysaccharide-induced lung injury

The animal model of inflammatory response induced by intratracheal application of lipopolysaccharide includes many typical features of acute lung injury or the acute respiratory distress syndrome. A number of experimental investigations have been performed to characterize the nature of this injury more effectively. In inflammatory conditions, hypoxia occurs frequently before and in parallel with pulmonary and non‐pulmonary pathological events. This current study was designed to examine the in vivo effect of hypoxia as a potentially aggravating condition in endotoxin‐induced lung injury. Lipopolysaccharide, 150 µg, was instilled intratracheally into rat lungs, and thereafter animals were exposed to either normoxia or hypoxia (10% oxygen). Lungs were collected 2, 4, 6 and 8 h later. Inflammatory response and tissue damage were evaluated by quantitative analysis of inflammatory cells and mediators, surfactant protein and vascular permeability. A significantly enhanced neutrophil recruitment was seen in lipopolysaccharide‐animals exposed to hypoxia compared to lipopolysaccharide‐animals under normoxia. This increased neutrophil accumulation was triggered by inflammatory mediators such as tumour necrosis factor‐α and macrophage inflammatory protein‐1β, secreted by alveolar macrophages. Determination of vascular permeability and surfactant protein‐B showed enhanced concentrations in lipopolysaccharide‐lungs exposed to hypoxia, which was absent in animals previously alveolar macrophage‐depleted. This study demonstrates that hypoxia aggravates lipopolysaccharide injury and therefore represents a second hit injury. The additional hypoxia‐induced inflammatory reaction seems to be predominantly localized in the respiratory compartment, underlining the compartmentalized nature of the inflammatory response.

Pulmonary aspiration : New therapeutic approaches in the experimental model

Background:Acute lung injury caused by gastric aspiration is a frequent occurrence in unconscious patients. Acute respiratory distress syndrome in association with gastric aspiration carries a mortality of up to 30% and accounts for up to 20% of deaths associated with anesthesia. Although the clinical condition is well known, knowledge about the exact inflammatory mechanisms is still incomplete. This study was performed to define the role of alveolar macrophages in this inflammatory response. In addition, potentially modifying effects of intratracheally applied nuclear factor &kgr;B inhibitor pyrrolidine dithiocarbamate were investigated. Methods:Rat alveolar macrophages were depleted by intratracheal administration of clodronate liposomes, and lung injury was evaluated 6 h after instillation of 0.1N hydrochloric acid. In a second set of experiments, pyrrolidine dithiocarbamate was intratracheally instilled 3 h after hydrochloric acid application, and injury parameters were determined. Results:Depletion of alveolar macrophages resulted in decreased production of inflammatory mediators in acid aspiration (23–80% reduction of messenger RNA or protein of inflammatory mediators; P < 0.05) and consequently also in diminished neutrophil recruitment (36% fewer neutrophils; P < 0.01). Treatment with pyrrolidine dithiocarbamate was highly effective in decreasing neutrophil recruitment (66%; P < 0.01) and vascular permeability (80%; P < 0.001). Conclusions:These data suggest that alveolar macrophages play an essential role in the inflammatory response of acid-induced lung injury. For the first time, attenuation of acid-induced lung injury with an inhibitor, applied after the onset of injury, is shown.

Acid-induced lung injury: Role of nuclear factor-κB

BACKGROUND Aspiration of acidic gastric contents leads to acute lung injury and is still one of the most common clinical events associated with acute lung injury. This study was performed to assess acid-induced lung inflammation in vitro and in vivo with respect to the time pattern of activated transcription factor nuclear factor-kappaB (NF-kappaB) and proinflammatory molecules. METHODS L2 cells (alveolar epithelial cells) were exposed for various periods to a medium with a pH of 6. In the in vivo model, 1 ml/kg of 0.1 n acidic solution was instilled into the lungs of rats. NF-kappaB binding activity and expression pattern of inflammatory mediators were determined. Blocking studies were performed with the NF-kappaB inhibitor pyrrolidine dithiocarbamate. RESULTS In vitro NF-kappaB binding activity showed a biphasic expression pattern with a first peak at 1 h and a second one at 6-8 h. In acid-injured rat lungs, NF-kappaB binding activity was confirmed in a biphasic manner with a first increase at 0.5-2 h (608 +/- 93% and 500 +/- 15%, respectively, P < 0.05) and a second peak at 8 h (697 +/- 35% increase, P < 0.005). Whole lung mRNA for macrophage inflammatory protein-1beta and macrophage inflammatory protein-2 showed a similar expression pattern, which could explain the biphasic neutrophil recruitment. Intratracheal pyrrolidine dithiocarbamate attenuated lung injury as evidenced by a reduction of neutrophil accumulation and expression of inflammatory mediators. CONCLUSIONS These data suggest that NF-kappaB binding activity plays a key role in molecular and cellular events in acid-induced lung injury.

The Effect of Hydroxyethyl Starches (hes 130/0.42 and Hes 200/0.5) on Activated Renal Tubular Epithelial Cells

BACKGROUND: Acute renal failure is a frequent complication of sepsis. Hydroxyethyl starch (HES) is widely used in the treatment of such patients. However, the effect of HES on renal function during sepsis remains controversial. We established an in vitro model of tumor necrosis factor-&agr; (TNF-&agr;)-stimulated human proximal tubular epithelial (HK-2) cells to assess the possible effects of HES 130/0.42 and HES 200/0.5 on these activated cells. METHODS: HK-2 cells were stimulated with TNF-&agr; in the presence or absence of HES 130/0.42 or 200/0.5. After 4, 10, and 18 h of incubation, monocyte chemoattractant protein-1 (MCP-1), a key chemoattractant for neutrophils and macrophages, was measured. In addition, viability and cytotoxicity assays were performed. RESULTS: MCP-1 expression was doubled upon TNF-&agr; exposure. In the presence of 2% and 4% HES 200/0.5 in 98% (96%) medium over a stimulation time period of 10 h and 18 h, the MCP-1 concentration was decreased between 26% and 56% (P < 0.05). TNF-&agr; stimulation resulted in a significant decrease of viability by 53%–63%, whereas viability decreased by only 32%–40% in coincubation with HES 130/0.42 (P < 0.005) and remained even less affected by TNF-&agr; in the presence of HES 200/0.5 (P < 0.001). The TNF-&agr;–induced cell death rate was attenuated in the presence of HES 200/0.5 (P < 0.05). CONCLUSIONS: This in vitro study shows that both HES products modulate cell injury upon inflammatory stimulation. The effect was more pronounced in the HES 200/0.5 group than for HES 130/0.42, suggesting a possible biological difference between the HES types.

CHARACTERIZATION OF RAT LUNG ICAM-1

Abstract.Objective and Design: We expressed soluble rat ICAM-1, generated a polyclonal anti-ICAM-1 antibody, and studied ICAM-1 upregulation in lung inflammatory conditions. Bacterial and baculovirus expression systems were employed.¶Material: 250 g adult, male Long Evans rats were used. For in vitro studies, rat pulmonary artery endothelial cells (RPAEC), rat alveolar macrophages and aortic rings were stimulated (as described below) and evaluated for ICAM-1 expression.¶Treatment: RPAEC and macrophages were stimulated with lipopolysaccharide (LPS) and recombinant murine tumour necrosis factor α (TNFα). In vivo immunoglobulin G (IgG) immune complex-induced lung injury was employed.¶Methods: Enzyme-linked immunoassay (ELISA) Western and Northern blot analyses and immunohistochemical evaluations were performed. All experiments were done at least in duplicate. Data were analyzed by two-tailed Student’s t-test.¶Results: ICAM-1 expression of RPAEC was time- and dose-dependent, peaking at 6 h after LPS-stimulation. LPS and TNFα each enhanced ICAM-1 expression on alveolar macrophages (reaching a maximum at 2 h). In IgG immune complex-induced lung injury, ICAM-1 mRNA isolated from whole lung peaked at 4 h, while lung ICAM-1 protein peaked at 6 h.¶Conclusions: Quantitation of ICAM-1 expression in vitro and in vivo suggests that ICAM-1 plays a central role in two lung inflammatory models. Furthermore, lung ICAM-1 upregulation involves at least two cell types: vascular endothelial cells and alveolar macrophages.