Markers for predicting the development of acute respiratory distress syndrome

Physiological and Disease Models of Respiratory System Based on Organ-on-a-Chip Technology

The pathogenesis of respiratory diseases is complex, and its occurrence and development also involve a series of pathological processes. The present research methods are have difficulty simulating the natural developing state of the disease in the body, and the results cannot reflect the real growth state and function in vivo. The development of microfluidic chip technology provides a technical platform for better research on respiratory diseases. The size of its microchannel can be similar to the space for cell growth in vivo. In addition, organ-on-a-chip can achieve long-term co-cultivation of multiple cells and produce precisely controllable fluid shear force, periodically changing mechanical force, and perfusate with varying solute concentration gradient. To sum up, the chip can be used to analyze the specific pathophysiological changes of organs meticulously, and it is widely used in scientific research on respiratory diseases. The focus of this review is to describe and discuss current studies of artificial respiratory systems based on organ-on-a-chip technology and to summarize their applications in the real world.

Metabolomics based predictive biomarker model of ARDS: A systemic measure of clinical hypoxemia

Despite advancements in ventilator technologies, lung supportive and rescue therapies, the outcome and prognostication in acute respiratory distress syndrome (ARDS) remains incremental and ambiguous. Metabolomics is a potential insightful measure to the diagnostic approaches practiced in critical disease settings. In our study patients diagnosed with mild and moderate/severe ARDS clinically governed by hypoxemic P/F ratio between 100-300 but with indistinct molecular phenotype were discriminated employing nuclear magnetic resonance (NMR) based metabolomics of mini bronchoalveolar lavage fluid (mBALF). Resulting biomarker prototype comprising six metabolites was substantiated highlighting ARDS susceptibility/recovery. Both the groups (mild and moderate/severe ARDS) showed distinct biochemical profile based on 83.3% classification by discriminant function analysis and cross validated accuracy of 91% using partial least squares discriminant analysis as major classifier. The predictive performance of narrowed down six metabolites were found analogous with chemometrics. The proposed biomarker model consisting of six metabolites proline, lysine/arginine, taurine, threonine and glutamate were found characteristic of ARDS sub-stages with aberrant metabolism observed mainly in arginine, proline metabolism, lysine synthesis and so forth correlating to diseased metabotype. Thus NMR based metabolomics has provided new insight into ARDS sub-stages and conclusively a precise biomarker model proposed, reflecting underlying metabolic dysfunction aiding prior clinical decision making.

Acute treatment with bone marrow-derived mononuclear cells attenuates the organ injury/dysfunction induced by hemorrhagic shock in the rat

Recent evidence suggests that cell therapy such as the injection of bone marrow-derived mononuclear cells (BMMNCs) can exert protective effects in various conditions associated with ischemia-reperfusion injury. Here, we investigate the effects of BMMNCs on the organ injury/dysfunction induced by hemorrhagic shock (HS). Thirty-seven anesthetized male Wistar rats were subjected to hemorrhage by reducing mean arterial pressure to 35 ± 5 mmHg for 90 min, followed by resuscitation with 20 mL/kg Ringer's lactate administered over 10 min and 50% of the shed blood over 50 min. Rats were killed 4 h after the onset of resuscitation. Bone marrow-derived mononuclear cells were freshly isolated from rat tibias and femurs using Percoll density gradient centrifugation, and BMMNCs (1 × 10 cells per rat in 1 mL/kg phosphate-buffered saline, i.v.) were administered on resuscitation. Hemorrhagic shock resulted in significant organ injury/dysfunction (renal, hepatic, neuromuscular) and inflammation (hepatic, lung). In rats subjected to HS, administration of BMMNCs significantly attenuated (i) organ injury/dysfunction (renal, hepatic, neuromuscular) and inflammation (hepatic, lung), (ii) increased the phosphorylation of Akt and glycogen synthase kinase-3β, (iii) attenuated the activation of nuclear factor-κB, (iv) attenuated the increase in extracellular signal-regulated kinase 1/2 phosphorylation, and (v) attenuated the increase in expression of intercellular adhesion molecule-1. Our findings suggest that administration of BMMNCs protects against the induction of early organ injury/dysfunction caused by severe HS by a mechanism that may involve activation of Akt and the inhibition of glycogen synthase kinase-3β and nuclear factor-κB.

Preventing the acute respiratory distress syndrome

Laudable supportive advances have been made to improve the care of patients with the Acute Respiratory Distress Syndrome (ARDS) but no pharmacologic interventions are known to reduce the high mortality of this disorder once it is established. This commentary discusses some of the challenges that arise in preventing ARDS in at-risk individuals and the likely dependence of this approach on biomarker panels that can be done in real time.

Effect of ergothioneine on acute lung injury and inflammation in cytokine insufflated rats

OBJECTIVE

The Acute Respiratory Distress Syndrome (ARDS), the most severe form of Acute Lung Injury (ALI), is a highly-fatal, diffuse non-cardiogenic edematous lung disorder. The pathogenesis of ARDS is unknown but lung inflammation and lung oxidative stress are likely contributing factors. Since no specific pharmacologic intervention exists for ARDS, our objective was to determine the effect of treatment with ergothioneine-a safe agent with multiple anti-inflammatory and antioxidant properties on the development of lung injury and inflammation in rats insufflated with cytokines found in lung lavages of ARDS patients.

METHOD

Sprague-Dawley rats (3-10/group) were given 15 mg/kg or 150 mg/kg l-ergothioneine intravenously 1h before or 18 h after cytokine (IL-1 and IFNγ) insufflation. Lung injury (lavage LDH levels) and lung inflammation (lavage neutrophil numbers) were measured 24h after cytokine insufflation.

RESULTS

Ergothioneine pre- and post-treatment generally decreased lung injury and lung inflammation in cytokine insufflated rats.

CONCLUSION

Ergothioneine should be considered for additional testing as a potential therapy for treating and preventing ARDS.

Acute respiratory distress syndrome induced by a swine 2009 H1N1 variant in mice

Background

Acute respiratory distress syndrome (ARDS) induced by pandemic 2009 H1N1 influenza virus has been widely reported and was considered the main cause of death in critically ill patients with 2009 H1N1 infection. However, no animal model has been developed for ARDS caused by infection with 2009 H1N1 virus. Here, we present a mouse model of ARDS induced by 2009 H1N1 virus.

Methodology Principal Findings

Mice were inoculated with A/swine/Shandong/731/2009 (SD/09), which was a 2009 H1N1 influenza variant with a G222D mutation in the hemagglutinin. Clinical symptoms were recorded every day. Lung injury was assessed by lung water content and histopathological observation. Arterial blood gas, leukocyte count in the bronchial alveolar lavage fluid and blood, virus titers, and cytokine levels in the lung were measured at various times post-inoculation. Mice infected with SD/09 virus showed typical ARDS symptoms characterized by 60% lethality on days 8–10 post-inoculation, highly edematous lungs, inflammatory cellular infiltration, alveolar and interstitial edema, lung hemorrhage, progressive and severe hypoxemia, and elevated levels of proinflammatory cytokines and chemokines.

Conclusions/Significance

These results suggested that we successfully established an ARDS mouse model induced by a virulent 2009 H1N1 variant without previous adaptation, which may be of benefit for evaluating the pathogenesis or therapy of human ARDS caused by 2009 H1N1 virus.

A nonerythropoietic peptide that mimics the 3D structure of erythropoietin reduces organ injury/dysfunction and inflammation in experimental hemorrhagic shock

Recent studies have shown that erythropoietin, critical for the differentiation and survival of erythrocytes, has cytoprotective effects in a wide variety of tissues, including the kidney and lung. However, erythropoietin has been shown to have a serious side effect-an increase in thrombovascular effects. We investigated whether pyroglutamate helix B-surface peptide (pHBSP), a nonerythropoietic tissue-protective peptide mimicking the 3D structure of erythropoietin, protects against the organ injury/ dysfunction and inflammation in rats subjected to severe hemorrhagic shock (HS). Mean arterial blood pressure was reduced to 35 ± 5 mmHg for 90 min followed by resuscitation with 20 mL/kg Ringer Lactate for 10 min and 50% of the shed blood for 50 min. Rats were euthanized 4 h after the onset of resuscitation. pHBSP was administered 30 min or 60 min into resuscitation. HS resulted in significant organ injury/dysfunction (renal, hepatic, pancreas, neuromuscular, lung) and inflammation (lung). In rats subjected to HS, pHBSP significantly attenuated (i) organ injury/dysfunction (renal, hepatic, pancreas, neuromuscular, lung) and inflammation (lung), (ii) increased the phosphorylation of Akt, glycogen synthase kinase-3β and endothelial nitric oxide synthase, (iii) attenuated the activation of nuclear factor (NF)-κB and (iv) attenuated the increase in p38 and extracellular signal-regulated kinase (ERK)1/2 phosphorylation. pHBSP protects against multiple organ injury/dysfunction and inflammation caused by severe hemorrhagic shock by a mechanism that may involve activation of Akt and endothelial nitric oxide synthase, and inhibition of glycogen synthase kinase-3β and NF-κB.

Moderate oxygen augments lipopolysaccharide-induced lung injury in mice

Despite the associated morbidity and mortality, underlying mechanisms leading to the development of acute lung injury (ALI) remain incompletely understood. Frequently, ALI develops in the hospital, coinciding with institution of various therapies, including the use of supplemental oxygen. Although pathological evidence of hyperoxia-induced ALI in humans has yet to be proven, animal studies involving high oxygen concentration reproducibly induce ALI. The potentially injurious role of lower and presumably safer oxygen concentrations has not been well characterized in any species. We hypothesized that in the setting of a preexisting insult to the lung, the addition of moderate-range oxygen can augment lung injury. Our model of low-dose intratracheal LPS (IT LPS) followed by 60% oxygen caused a significant increase in ALI compared with LPS or oxygen alone with increased alveolar neutrophils, histological injury, and epithelial barrier permeability. In the LPS plus oxygen group, regulatory T cell number was reduced, and macrophage activation markers were increased, compared with LPS alone. Antibody-mediated depletion of neutrophils significantly abrogated the observed lung injury for all measured factors. The enhanced presence of alveolar neutrophils in the setting of LPS and oxygen is due, at least in part, to elevated chemokine gradients signaling neutrophils to the alveolar space. We believe these results strongly support an effect of lower concentrations of oxygen to augment the severity of a mild preexisting lung injury and warrants further investigation in both animals and humans.

Hyperpolarized 83Kr and 129Xe NMR Relaxation Measurements of Hydrated Surfaces: Implications for Materials Science and Pulmonary Diagnostics

In this proof of principle work, a technique is introduced to study hydrated surfaces using hyperpolarized (hp) 83Kr NMR spectroscopy. The longitudinal (T1) relaxation of hp-83Kr is shown to be extremely sensitive to the presence of adsorbed water on hydrophilic borosilicate and hydrophobic siliconized glass surfaces. The krypton surface relaxation is found to be largely independent of the total gas pressure applied to the studied materials, and the presented technique is therefore fairly robust. However, the relaxational properties of hp-83Kr can be "tuned" by adjusting the composition of the optical pumping gas mixture. This effect may be important for practical applications such as hp-83Kr MR imaging and can be achieved without sacrificing signal intensity. Complementary information to that of hp-83Kr surface relaxation data can be obtained from hp-129Xe relaxation measurements that are sensitive to the presence of paramagnetic surface sites. In contrast to the signal decay of hp-129Xe, the longitudinal relaxation of 83Kr is largely unaffected by paramagnetic impurities, and in some materials, 83Kr and 129Xe show comparable T1 times that are caused by two completely different relaxation mechanisms. Finally, the relaxation times of 83Kr in contact with bovine lung surfactant coated glass pores that are similar in size to mammalian alveoli are presented. The results suggest that in vivo MR studies may be feasible and could provide valuable information about changes in pulmonary surface chemistry.

Enhanced neutrophil migratory activity following major blunt trauma

BACKGROUND

Neutrophil migration into the lung is a critical, but poorly understood step in the pathogenesis of post-traumatic, acute respiratory distress syndrome (ARDS). We investigated changes in interleukin-8 (IL-8) mediated neutrophil migration and associated changes in receptor expression, of the IL-8 receptors CXCR1, the integrins CD11b/CD18 and platelet endothelial cell adhesion molecule-1 (PECAM-1) in patients sustaining major trauma.

METHODS

Eleven patients with major trauma, injury severity score (ISS), median 22 (range 18-41), were followed prospectively. Eleven normal volunteers were used as controls. Blood samples were obtained within 4+/-2 h of injury, at 24 h, day 3 and day 5. Neutrophils migration was assessed by an in vitro IL-8 assay and neutrophil surface receptor expression by FACS analysis.

RESULTS

IL-8 mediated neutrophil migration was significantly increased on admission following major trauma and remained elevated for 3 days (p<0.05). This was associated with up-regulation of CXCR1 (p<0.01) and down-regulation of PECAM-1 (p<0.05). CD11b and CD18 although initially unchanged, became down-regulated on day 3 (p<0.05).

CONCLUSIONS

These data show that major trauma primes circulating neutrophils for increased migration in response to IL-8. This response is sustained for 72 h and is associated with changes in neutrophil surface receptor expression.

Serum ferritin elevation and acute lung injury in rats subjected to hemorrhage: reduction by mepacrine treatment

Ferritin regulates iron levels and, for unknown reasons, serum ferritin concentrations are increased in patients at risk for and with acute lung injury (ALI) and multiple organ failure. Uncomplexed iron could exacerbate the toxicity of the increased oxidative stress that occurs in patients with ALI and multiple organ failure and thereby contribute to disease. In the present investigation, the authors found that serum and lung lavage ferritin concentrations increased in hemorrhaged rats that develop ALI as manifested by increased lung inflammation (increased lung lavage leukocyte counts and lung myeloperoxidase activities) and increased lung leak (increased lung lavage protein concentrations). Treatment with mepacrine, a phospholipase A2 inhibitor, attenuated the increases in serum and lung lavage ferritin concentrations, lung inflammation, and lung leak that occur in rats subjected to hemorrhage. The findings show that serum and lung ferritin levels increase and may play a role in the development of acute lung injury caused by hemorrhage.

Disturbed homeostasis of lung intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 during sepsis

Cecal ligation and puncture (CLP)-induced sepsis in mice was associated with perturbations in vascular adhesion molecules. In CLP mice, lung vascular binding of (125)I-monoclonal antibodies to intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 revealed sharp increases in binding of anti-ICAM-1 and significantly reduced binding of anti-VCAM-1. In whole lung homogenates, intense ICAM-1 up-regulation was found (both in mRNA and in protein levels) during sepsis, whereas very little increase in VCAM-1 could be measured although some increased mRNA was found. During CLP soluble VCAM-1 (sVCAM-1) and soluble ICAM-1 (sICAM-1) appeared in the serum. When mouse dermal microvascular endothelial cells (MDMECs) were incubated with serum from CLP mice, constitutive endothelial VCAM-1 fell in association with the appearance of sVCAM-1 in the supernatant fluids. Under the same conditions, ICAM-1 cell content increased in MDMECs. When MDMECs were evaluated for leukocyte adhesion, exposure to CLP serum caused increased adhesion of neutrophils and decreased adhesion of macrophages and T cells. The progressive build-up in lung myeloperoxidase after CLP was ICAM-1-dependent and independent of VLA-4 and VCAM-1. These data suggest that sepsis disturbs endothelial homeostasis, greatly favoring neutrophil adhesion in the lung microvasculature, thereby putting the lung at increased risk of injury.

Serum ferritin increases in hemorrhaged rats that develop acute lung injury: effect of an iron-deficient diet

For unknown reasons, serum ferritin levels increase in patients at risk for and with acute lung injury (ALI). To improve understanding of the relationship between serum ferritin alterations and the development of ALI, we investigated the effect of iron deficiency on the serum ferritin response of rats subjected to hemorrhage. We found that rats fed an iron-deficient diet for 6 weeks had decreased hemoglobin, hematocrit, liver total iron, liver total iron-binding capacity, and liver ferritin concentrations but the same serum ferritin concentrations as rats fed a control diet. Following hemorrhage, serum ferritin concentrations increased rapidly and progressively in rats fed a control diet. Along with increases in serum ferritin concentrations, control diet rats subjected to hemorrhage also had increased lung lavage leukocyte numbers, lung myeloperoxidase activities (lung inflammation), and lung lavage protein concentrations (lung leak) compared to control diet fed rats subjected to sham treatment. By comparison, the serum ferritin concentrations, lung inflammation, and lung leak of hemorrhaged rats fed an iron-deficient diet were decreased compared to hemorrhaged rats fed a control diet. These findings indicate that serum ferritin concentrations increase and acute lung injury develops following hemorrhage in rats fed a control, but not an iron-deficient, diet. A relatively brief exposure to an iron-deficient diet reduces hemorrhage-induced ALI.

Monitoring alveolar epithelial function in acute lung injury

OBJECTIVE

Identification of humoral markers of acute lung injury may lead to insights into pathologic mechanisms. In addition, specific markers may be useful for predicting development of acute respiratory distress syndrome (ARDS) or for assessing prognosis. Ultimately, studies of lung injury markers may help define interventions that prevent or moderate ARDS. The alveolar epithelium is important both for the integrity of the blood-gas barrier and for repair of the barrier after lung injury. This article reviews markers that derive from or relate to the alveolar epithelium and that might be used for monitoring alveolar epithelial function in acute lung injury. Surfactant apoproteins may be important markers of injury or for prognosis. Levels of surfactant apoprotein A (SP-A) fall 50-75% in patients with severe lung injury compared to normal patients. Serum levels of SP-A in patients dying of acute respiratory distress syndrome are double serum levels of survivors.

Mechanisms of surface-tension-induced epithelial cell damage in a model of pulmonary airway reopening

Airway collapse and reopening due to mechanical ventilation exerts mechanical stress on airway walls and injures surfactant-compromised lungs. The reopening of a collapsed airway was modeled experimentally and computationally by the progression of a semi-infinite bubble in a narrow fluid-occluded channel. The extent of injury caused by bubble progression to pulmonary epithelial cells lining the channel was evaluated. Counterintuitively, cell damage increased with decreasing opening velocity. The presence of pulmonary surfactant, Infasurf, completely abated the injury. These results support the hypotheses that mechanical stresses associated with airway reopening injure pulmonary epithelial cells and that pulmonary surfactant protects the epithelium from this injury. Computational simulations identified the magnitudes of components of the stress cycle associated with airway reopening (shear stress, pressure, shear stress gradient, or pressure gradient) that may be injurious to the epithelial cells. By comparing these magnitudes to the observed damage, we conclude that the steep pressure gradient near the bubble front was the most likely cause of the observed cellular damage.

Oxygen homeostasis, thiol equilibrium and redox regulation of signalling transcription factors in the alveolar epithelium

There is growing evidence linking the pathophysiology of lung disease to an imbalance state of reduction-oxidation (redox) equilibrium. The therapeutic potential of glutathione, an ubiquitous sulfhydryl thiol, and its immunopharmacological properties in the airway epithelium bears clinical consequences for the paediatric treatment of respiratory distress (RD). Dynamic variation in alveolar pO(2) and its effect on redox state may impose a direct role in modulating the pattern of gene expression in lung tissues and, accordingly, could be pivotal in determining cellular fate under these conditions. Hypoxia-inducible factor-1alpha (HIF-1alpha) and nuclear factor-kappaB (NF-kappaB) are redox-sensitive transcription factors of particular importance because their differential activation by reducing and oxidizing signals, respectively, regulate the expression/suppression of O(2)-responsive genes. The regulation of these transcription factors, therefore, which is redox sensitive, is consistent with their roles in coordinating adaptive homeostatic responses to oxidative stress. Functionally, the relationship between O(2), glutathione biosynthesis and transcription factor activity bears typical implications for the pattern of cellular survivorship and alveolarization on exposure to O(2)-linked stresses. In this review, I discuss (1) the HIF-1alpha/NF-kappaB responsiveness to dynamic changes in pO(2) characteristic of the transition period from placental to pulmonary-based respiration, (2) the capacity of the alveolar epithelium to engage in glutathione biosynthesis and redox shuttling, effectively forming a feedback mechanism governing gene expression, (3) the restitution of antioxidant/prooxidant equilibrium following oxidative challenge and its dependency on the adaptive coordination of responses between redox-associated signalling pathways controlling apoptosis and genetic regulatory factors and (4) a likely association between oxidative stress and the evolution of an inflammatory signal through the pleiotropic O(2)-sensitive cytokines.

Ferritin and desferrioxamine attenuate xanthine oxidase-dependent leak in isolated perfused rat lungs

Iron, through its participation in reactions that generate reactive oxygen species, may contribute to the oxidative lung injury observed in patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). A number of investigators have shown that the endogenous iron storage protein ferritin increases in the blood of patients with and at-risk for ALI and ARDS, but the significance of these increases are not known. In the present investigation, we measured lung tissue levels of thiobarbituric acid reactive substances (TBARS) and lung leak in isolated rat lungs perfused with xanthine oxidase (XO) and purine, an enzymatic system which generates reactive oxygen species. We found that adding ferritin (100 ng/mL) or desferrioxamine (DFO, 10 mM), an iron chelator, to the vascular perfusate solution decreased oxidant-induced leak in isolated rat lungs perfused with XO and purine. Addition of ferritin or DFO also decreased TBARS in isolated rat lungs perfused with XO and purine; neither ferritin nor DFO, however, decreased XO activity in vitro. Our results suggest that oxidative lung leak may be altered by the availability of reactive iron and that ferritin may contribute to protection against oxidative lung injury.

Increased neutrophil migratory activity after major trauma: a factor in the etiology of acute respiratory distress syndrome?

OBJECTIVE

Neutrophil infiltration of the lung is characteristic of early posttraumatic acute respiratory distress syndrome (ARDS). This study examines the ability of neutrophils isolated (over the first 24 hrs) from the peripheral blood of patients admitted after major trauma to migrate in response to interleukin-8. Interleukin-8 is elevated in the lung within 2 hrs of major trauma in patients who later develop ARDS, and thus it plays a central role in the recruitment of neutrophils to the lung and their subsequent activation. We hypothesized that enhanced interleukin-8-mediated neutrophil migratory activity in the early postinjury phase, before the development of ARDS, may be a crucial factor in the etiology of ARDS.

DESIGN

Prospective observational study.

SETTING

University Hospital Wales, the Royal Gwent Hospital, and East Glamorgan General Hospital. Laboratory work was conducted at the Institute of Nephrology.

PATIENTS

Adult blunt trauma victims with Injury Severity Score > or = 18.

MEASUREMENTS AND MAIN RESULTS

Neutrophils were isolated from citrated blood from 17 adult blunt major trauma patients at admission (0 hrs) and 8 and 24 hrs later. Identical samples were obtained from normal laboratory volunteers (n = 9). The neutrophil count in each specimen was measured, and the number of neutrophils migrating across porous tissue culture inserts in response to defined concentrations of interleukin-8 (0, 10, 30, and 100 ng/mL) was quantitated by peroxidase assay. Neutrophil counts in the whole blood specimens obtained from those later developing ARDS were elevated significantly at admission and declined rapidly throughout the next 24 hrs. Significantly greater numbers of trauma patients' neutrophils migrated to concentrations of interleukin-8 (30 and 100 ng/mL) at each time point when compared with normal volunteers (Mann-Whitney U test, p <.05). Neutrophils isolated from major trauma patients exhibited an enhanced migratory response to high concentrations of interleukin-8 throughout the first 24 hrs of admission, in contrast to the normal physiologic attenuation of migration seen in neutrophils isolated from normal laboratory volunteers.

CONCLUSIONS

These data indicate that major blunt trauma enhances the migratory capacity of circulating neutrophils. This is manifest within 2 hrs of admission and may be attributable to alteration in interleukin-8 receptor expression, affinity, or downstream signaling. In patients who later develop ARDS, initially elevated circulating neutrophil counts decrease rapidly, over the same time course. Early enhanced neutrophil migratory activity coupled with elevated pulmonary concentrations of interleukin-8 may be central to the establishment of the neutrophil infiltration that is characteristic of ARDS.

Altered neutrophil trafficking during sepsis

In sepsis, dysregulation of the inflammatory system is well known, as reflected in excessive inflammatory mediator production, complement activation, and appearance of defects in phagocytic cells. In the current study sepsis was induced in rats by cecal ligation/puncture. Early in sepsis the beta(1) and beta(2) integrin content on blood neutrophils increased in a nontranscriptional manner, and the increase in beta(2), but not beta(1), integrin content was C5a dependent. Similar changes could be induced in vitro on blood neutrophils following contact with phorbol ester or C5a. Direct injury of lungs of normal rats induced by deposition of IgG immune complexes (IgG-IC) caused 5-fold increases in the myeloperoxidase content that was beta(2), but not beta(1), dependent. In contrast, in cecal ligation/puncture lungs myeloperoxidase increased 10-fold after IgG immune complex deposition and was both beta(1) and beta(2) integrin dependent. These data suggest that sepsis causes enhanced neutrophil trafficking into the lung via mechanisms that are not engaged in the nonseptic state.

Regulatory potential of n-3 fatty acids in immunological and inflammatory processes

Over the last few years immunonutrition has gained increasing importance. Among other compounds lipids, especially n-3 polyunsaturated fatty acids, were shown to influence the immune response. The anti-inflammatory effects they exert can be induced by free fatty acids, triglyceride fatty acids, after incorporation into the membrane phopspholipid bilayer or following metabolism to eicosanoids. n-3 Fatty acids influence inflammatory cell activation processes from signal transduction to protein expression even involving effects at the genomic level. n-3 Fatty acid-mediated mechanisms decreased cytokine-induced adhesion molecule expression, thereby reducing inflammatory leucocyte-endothelium interactions and modified lipid mediator synthesis, thus influencing the transendothelial migration of leucocytes and leucocyte trafficking in general. Even the metabolic repertoire of specific immunocompetent cells such as cytokine release or proliferation is modified by n-3 fatty acids. Beyond this they regulate lipid homeostasis shifting the metabolic pathways towards energy supply thus optimizing the function of immune cells. Due to the regulatory impact on different processes of inflammatory and immune cell activation n-3 fatty acids provide positive effects on various states of immune deficiencies and diseases with a hyperinflammatory character, among which selected examples are presented.

Parenteral nutrition with n-3 lipids in sepsis

Dietary supplements of n-3 fatty acids have long been used to influence chronic inflammatory disorders. Recent studies with an immune-enhancing diet partly based on n-3 fatty acids report beneficial effects in patients with acute hyper-inflammatory diseases, such as the sepsis syndrome or adult respiratory distress syndrome (ARDS). The possible suppression of exaggerated leucocyte activity, the improvement of microcirculatory events, as well as the opportunity to administer intravenous lipids enriched in n-3 fatty acids signal the possibility of a combination of parenteral caloric support and pharmacological intervention. Using parenteral administration of fish oil-based lipids, a new rapid and highly effective anti-inflammatory agent may allow the option to alter the immune status in hyper-inflammatory diseases such as sepsis and ARDS.

Parathyroid hormone-related protein and lung injury after pulmonary thromboendarterectomy

Parathyroid hormone-related protein (PTHrP) is an autocrine growth and differentiation factor for alveolar type II epithelial cells. Type II cells secrete pulmonary surfactant and are pluripotent cells with a role in alveolar epithelial repair after lung injury. The goals of this study were to investigate whether the levels of PTHrP in bronchoalveolar lavage liquid (BAL) varied between patients who did and did not develop lung injury after pulmonary thromboendarterectomy (PTE). BAL was performed in 48 patients undergoing PTE for unresolved pulmonary emboli. Samples were obtained following induction of anesthesia, following separation from cardiopulmonary bypass, and 48 h postoperatively. PTHrP was measured by radioimmunoassay. Lung injury was diagnosed in 23 patients on the basis of hypoxemia (PaO(2)/FIO(2) < 300) and the presence of lung infiltrates in the absence of infection or atelectasis. Patients with lung injury had significantly lower preoperative BAL levels of PTHrP, 21 (21-30) pg/ml (median, interquartile gap), compared to patients without lung injury, 34 (21-41) pg/ml (P < 0.05). Preoperative BAL PTHrP levels < 32 pg/ml predicted lung injury with a positive predictive value of 60% and negative predictive value of 82%. The odds of developing lung injury for patients with preoperative PTHrP levels below this cutpoint were 6 times the odds for patients with higher levels.

Autoantibodies to lipids in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

OBJECTIVE

To investigate the presence of autoantibodies to lipids in the bronchoalveolar lavage (BAL) fluid from adult patients with acute respiratory distress syndrome (ARDS).

DESIGN

Analysis of immunoglobulin G (IgG) in BAL fluid by electrophoresis followed by immunoblotting and characterization of immunoglobulins as antilipid autoantibodies.

SETTING

Intensive care unit of a university hospital and two research university laboratories.

SUBJECTS

Twenty-seven mechanically ventilated patients in total, including nine patients with ARDS and two control groups.

INTERVENTIONS

Patients were ventilated with a mechanical ventilation mode. Six aliquots of 20-mL sterile normal saline at 37 degrees C were infused through the working channel of the bronchoscope.

MEASUREMENTS

Total protein, detection of IgG by electrophoresis followed by immunoblotting, and characterization of IgG by enzyme-linked immunosorbent assay using different lipids as target antigens.

MAIN RESULTS

Antiphospholipid autoantibodies are present in BAL fluid of ARDS patients. Among the phospholipids tested, phosphatidic acid and phosphatidylserine gave the most significant activity. The IgG fraction, purified from BAL fluids by affinity chromatography, gave the same pattern of binding as that of the BAL fluid.

CONCLUSION

The presence of antiphospholipid autoantibodies in BAL fluid suggests involvement of autoimmune mechanisms in the pathogenesis of ARDS.

Lung compartmentalization of inflammatory cells in sepsis

Lung injury commonly occurs in the setting of systemic inflammatory response syndrome occurring during bacterial sepsis. There has been little work quantifying different leukocytes within the different compartments of the lung and their association with overt lung injury in sepsis. We examined the pathogenesis of lung injury after cecal ligation and puncture (CLP), a clinically relevant model of sepsis. To assess the sequestration and migration of leukocytes, leukocyte differentials were obtained for the lung vascular compartment and the bronchoalveolar airspace. At 24 h post CLP, there were signs of edema in the lung, while at 48 h after CLP, there were clear indications of alveolar wall thickening with increased cellularity and diffuse alveolar hemorrhage. The number of lymphocytes in the pulmonary vascular compartment dropped by 50% and doubled in the (bronchoalveolar lavage) BAL, 24 h after CLP compared to sham controls suggesting that there was transendothelial migration of lymphocytes. At 48 h after CLP, lymphocyte numbers in the vasculature was similar to controls but BAL lymphocyte numbers were still raised. The number of pulmonary intravascular neutrophils were similar to controls at 24 h post CLP but were greatly elevated 48 h after CLP. The increase in neutrophils was partly due to a substantial increase in the percentage of immature band cells, indicating recruitment of neutrophils from the bone marrow. There were very few neutrophils in the BAL of sham controls and CLP rats. Perfusate monocyte/macrophages were significantly increased 48 h after CLP and a similar increase in macrophages was observed in the BAL. These results strongly suggest a role for lymphocytes and macrophages in the development of overt lung injury as the migration of these cells corresponds to that of the appearance of lung injury 48 h after CLP. Importantly our data also demonstrates the compartmentalization and migration of different inflammatory cell-types during the development of sepsis.

Interleukin-2 involvement in early acute respiratory distress syndrome: relationship with polymorphonuclear neutrophil apoptosis and patient survival

OBJECTIVE

To determine blood and lung alveolar concentrations of interleukin (IL)-2 in acute respiratory distress syndrome (ARDS) and their relationship with polymorphonuclear neutrophil (PMN) apoptosis and patient survival.

DESIGN

Prospective cohort study.

SETTING

Medical and surgical intensive care units (ICUs; Canada) and the intensive care department (Belgium).

PATIENTS

Nineteen consecutive patients with ARDS, 14 non-ARDS ICU patients, and 20 healthy volunteers.

INTERVENTIONS

Blood samples and bronchoalveolar lavages (BAL) obtained via venous puncture and by fiberoptic bronchoscopy in the first 72 hrs after the onset of ARDS.

MEASUREMENTS AND MAIN RESULTS

One early point concentration of IL-2 was measured in both blood and BAL fluids of the three groups. In vivo alveolar PMN apoptotic index in BAL fluids and the influence of BAL fluid exposure on normal blood PMN spontaneous apoptosis in vitro were evaluated. Blood IL-2 was significantly lower in patients with ARDS compared with non-ARDS ICU patients and controls. In contrast, IL-2 in BAL fluids of patients with ARDS was dramatically elevated compared with non-ARDS ICU patients and controls. ARDS survivors exhibited lower early IL-2 blood levels than nonsurvivors and generally had a higher IL-2 lung content Lung alveolar PMN apoptosis in vivo was lower in patients with ARDS in comparison with controls. This apoptotic index was correlated with corresponding IL-2 alveolar levels in patients with ARDS. Exposure of normal blood PMN to BAL fluids from patients with ARDS delayed apoptosis in vitro. Immunodepletions of IL-2, granulocyte-macrophage colony stimulating factor, and a combination of both cytokines from BAL fluids of ARDS patients significantly restored PMN apoptosis. The recovery of PMN apoptosis was more effective when IL-2 was depleted in BAL fluids from ARDS survivors compared with nonsurvivors.

CONCLUSIONS

Opposite and disproportional concentrations of IL-2 are observed in blood and lung fluids of patients with early ARDS. IL-2 significantly contributes (with granulocyte-macrophage colony stimulating factor) to the inhibition of PMN apoptosis in BAL fluids of patients with ARDS. Early low blood IL-2 and high IL-2-driven inhibition of PMN apoptosis are beneficial to survivors. Thus, IL-2 is a new candidate for monitoring in early ARDS and an interesting indicator of prognosis.

Acute lung injury and acute respiratory distress syndrome in sepsis and septic shock

Sepsis remains the leading cause of ARDS, and ARDS is still an often fatal condition. With our expanding knowledge of the pathobiologic mechanisms and the relationship between these two entities, early recognition, treatment, and prevention of sepsis may prevent or hasten recovery from ARDS. Understanding the biologic markers involved in the complex inflammatory response of sepsis and acute lung injury offers the possibility of future investigations to target treatment based on these mediators.

Consensus conference definitions for sepsis, septic shock, acute lung injury, and acute respiratory distress syndrome: time for a reevaluation

Definitions for sepsis, septic shock, acute lung injury (ALI), and acute respiratory distress syndrome (ARDS) were developed by consensus conferences with the goal of achieving standardization of terminology and improved homogeneity of patient populations in clinical studies. Although such definitions have been useful in epidemiologic investigations, the criteria specified by the consensus conferences are broad and insufficiently specific to address the problem of heterogeneous mechanisms leading to clinical syndromes. An important challenge is to progress from clinical syndromes, as presently defined, to more specific entities that are delineated by alterations in specific immunologic or biochemical pathways. Such mechanistic definitions will provide more homogeneous groups of patients who can be identified at early stages of their clinical course. This approach encourages focused investigation of pathways leading to organ system dysfunction and death and, also, provides an efficient framework for the development of new therapies useful in critically ill patients.

Lung injury and acute respiratory distress syndrome after cardiopulmonary bypass

Cardiopulmonary bypass is often followed by pulmonary dysfunction as assessed by measuring the alveolar-arterial oxygenation gradient, intrapulmonary shunt, degree of pulmonary edema, pulmonary compliance, and pulmonary vascular resistance. It is also regarded as a risk factor for development of acute respiratory distress syndrome. On the other hand, cardiopulmonary bypass is associated with a whole body inflammatory response, which involves activation of complement, leukocytes, and endothelial cells with secretion of cytokines, proteases, arachidonic acid metabolites, and oxygen free radicals. Leukocyte adhesion to microvascular endothelium, leukocyte extravasation, and tissue damage are the final steps. Although the inflammatory response to cardiopulmonary bypass often remains at subclinical levels, it can also lead to major organ dysfunction and multiple organ failure. This review article summarizes the recent literature on the molecular and cellular mechanisms involved in the phenomenon of pulmonary dysfunction after cardiopulmonary bypass. It also summarizes reports on the prevalence and mortality of acute respiratory distress syndrome after cardiac surgery.

Pro-inflammatory cytokines increase the permeability of paracetamol across a human endothelial-smooth muscle cell bilayer model

Human umbilical vein endothelial cells and smooth muscle cells, cultured on either side of fixed, porous supports, were used to study the effect of pro-inflammatory cytokines on the transvascular passage of the drug paracetamol. The cellular bilayer effectively retarded the passage of the drug from the "luminal" or endothelial side, to the "tissue" or smooth muscle side of the bilayer over a 30-min period. When the cells were incubated with either IL-1beta (100 ng/l) or TNF-alpha (10 microg/l) for 4 h prior to exposure to paracetamol, the permeability of the bilayer to the drug increased to that of the control inserts without cells. In contrast, the pro-inflammatory cytokines did not affect the electrical resistance of the bilayer, indicating continued tight junctional integrity, or the passage of [3H]-inulin, an indicator of paracellular transport, or the passage of fluorescein, an indicator of passive diffusion across the cells. Together these data indicate the suitability of this syngenetic human cell co-culture model for studying factors affecting the systemic disposition of drug molecules at the level of the vascular wall. The data also indicate that the transport of paracetamol across the blood vessel wall may be greatly enhanced at sites of tissue inflammation in the systemic circulation.

Initial serum ferritin levels in patients with multiple trauma and the subsequent development of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) represents a catastrophic form of inflammatory lung injury that occurs unpredictably in some, but not all, at-risk patients. In this study, we investigated serum ferritin as a marker for ARDS development in a homogenous group of patients at-risk because of multiple trauma. We hypothesized that since ferritin synthesis is increased by proinflammatory cytokines, which are increased and implicated in ARDS, that ferritin levels would increase and that ferritin increases would correlate with the degree of inflammation and therefore the development of ARDS. We studied 42 patients (25 male, 17 female) who as a consequence of multiple trauma became at-risk for developing ARDS. Using the European/American Consensus definition for ARDS, 16 (38%) patients subsequently developed ARDS (11 male and five female). We found that initial serum ferritin levels correlated with the subsequent development of both ARDS (progression to ARDS, median = 638 ng/ml; (range, 70 to 4,500) versus nonprogression to ARDS = 185 ng/ml; range, 12 to 2,850) (p = 0.02, r = -0.27) and multiple organ failure (p < 0.05, r = 0.39). Using our previously established cutoff points for serum ferritin, the positive predictive value was 62% for men and 75% for women. Initial serum ferritin levels also correlated with a measurement of the degree of initial trauma injury, i.e., the injury severity score (ISS) (p < 0.05, r = 0.37). However, there was no correlation between serum ferritin levels and other markers of clinical injury, namely, lowest PaO2/FIO2 ratio (p = 0.67), days requiring ventilation (p = 0.09), or mortality (p = 0.42). A significant association existed between serum ferritin levels and products of endothelial activation, i.e., sE-selectin (p < 0.04, r = 0.37) and sICAM-1 (p < 0.01, r = 0.21). In the future, with the development of novel anti-inflammatory therapies, early identification of specific high-risk patients would allow the institution of these therapies and thereby increase the chances of reducing ARDS morbidity and mortality.

Clinical use of lipids to control inflammatory disease

Selective dietary supplementation with lipids has long been used to influence the course of chronic inflammatory diseases. This review describes new aspects of the molecular mechanism of lipids to modulate leukocyte activity and highlights some recent clinical studies on therapeutic lipid administration. New promising advances in parenteral application of lipids as well as the impact on acute inflammatory disorders are discussed.