Inflammatory cytokines in the BAL of patients with ARDS. Persistent elevation over time predicts poor outcome

Systemic inflammatory response secondary to abdominal compartment syndrome: stage for multiple organ failure

BACKGROUND

The abdominal compartment syndrome (ACS) has been implicated in the pathogenesis of postinjury multiple organ failure. The ACS is defined as intra-abdominal hypertension causing adverse physiologic response. This study was designed to determine the effects of IAH on the production of interleukin-1b (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor (TNF-alpha), and the effects on remote organ injury.

METHODS

IAH was induced in Sprague-Dawley rats which were divided into 5 groups, 10 animals each. Intra-abdominal pressure (IAP) was increased to 20 mm Hg for 60 and 90 minutes in two different groups. In a third group following IAP of 20 mm Hg the abdomen was decompressed for 30 minutes before samples were collected. The other animals were used as controls. Hemodynamic response was monitored throughout the procedure. Cytokine levels were assessed in the plasma. Remote organ injury was assessed by histopathology and myeloperoxidase activity.

RESULTS

IAH caused a significant decrease in MAP. After abdominal decompression MAP returned to baseline levels. A significant decrease in arterial pH was also noted. Increase in the levels of TNF-alpha and IL-6 was noted 30 minutes after abdominal decompression. Plasma concentration of IL-1b was elevated after 60 minutes of IAH. Abdominal decompression, however, did not cause a significant increase in the levels of this cytokine. Lung neutrophil accumulation was significantly elevated only after abdominal decompression. Histopathological findings showed intense pulmonary inflammatory infiltration including atelectasis and alveolar edema.

CONCLUSIONS

IAH provokes the release of pro-inflammatory cytokines which may serve as a second insult for the induction of MOF.

Critical role for CXCR2 and CXCR2 ligands during the pathogenesis of ventilator-induced lung injury

Mortality related to adult respiratory distress syndrome (ARDS) ranges from 35% to 65%. Lung-protective ventilator strategies can reduce mortality during ARDS. The protective strategies limit tidal volumes and peak pressures while maximizing positive end-expiratory pressure. The efficacy of this approach is due to a reduction of shear-stress of the lung and release of inflammatory mediators. Ventilator-induced lung injury (VILI) is characterized by inflammation. The specific mechanism(s) that recruit leukocytes during VILI have not been elucidated. Because the murine CXC chemokines KC/CXCL1 and MIP-2/CXCL2/3, via CXCR2, are potent neutrophil chemoattractants, we investigated their role in a murine model of VILI. We compared two ventilator strategies in C57BL/6 mice: high peak pressure and high stretch (high peak pressure/stretch) versus low peak pressure/stretch for 6 hours. Lung injury and neutrophil sequestration from the high-peak pressure/stretch group were greater than those from the low-peak pressure/stretch group. In addition, lung expression of KC/CXCL1 and MIP-2/CXCL2/3 paralleled lung injury and neutrophil sequestration. Moreover, in vivo inhibition of CXCR2/CXC chemokine ligand interactions led to a marked reduction in neutrophil sequestration and lung injury. These findings were confirmed using CXCR2(-/-) mice. Together these experiments support the notion that increased expression of KC/CXCL1 and MIP-2/CXCL2/3 and their interaction with CXCR2 are important in the pathogeneses of VILI.

ST2 protein induced by inflammatory stimuli can modulate acute lung inflammation

We have investigated gene and protein expression of ST2/ST2L in a murine alveolar macrophage (AM) cell line, MH-S, reacting to inflammatory stimuli in vitro and in the lung tissue of an acute lung injury model in vivo. We have also analyzed the effect of soluble ST2 protein on inflammatory response of MH-S cells. Lipopolysaccharide (LPS) and proinflammatory cytokines such as IL-1beta, IL-6, and TNF-alpha induced ST2 mRNA expression in MH-S cells. In an acute lung injury model, protein and mRNA expression levels of ST2 increased to the maximal level at 24-72h after the LPS challenge. Furthermore, pretreatment with ST2 protein significantly reduced the protein production and gene expression of IL-1alpha, IL-6, and TNF-alpha in LPS-stimulated MH-S cells in vitro. These results suggest that increases in endogenous ST2 protein in AM, which is induced by inflammatory stimuli, such as LPS and proinflammatory cytokines, may modulate acute lung inflammation.

Association between increased levels of IL-2 and IL-15 and outcome in patients with early acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome remains a serious, often fatal, condition, despite progress in modern critical care treatment. Cytokines play an important role in the pathogenesis of the syndrome, although their role in the evolution and outcome has not been clearly elucidated. We explored whether the measurement of serum and bronchoalveolar lavage IL-2 and IL-15 at the time of hospital admission can predict the outcome of this syndrome.

METHODS

Serum and bronchoalveolar lavage levels of IL-2 and IL-15 were measured in eight patients with ARDS (group A) and 26 patients on high risk for ARDS development who never developed ARDS (group B) from samples obtained at the time of admission.

RESULTS

Serum IL-2 (P > 0.05) and IL-15 (P < 0.05) levels were higher in group A than in group B. Serum levels of both cytokines were higher in patients who did not survive in both of the groups A and B compared to those who survived (P < 0.05, and P < 0.0001, respectively). The only significant change in BALF was the higher level of IL-15 in surviving group A patients (P < 0.05) when compared with the non survivors of the same group. For a serum cut-off level of 173 pg mL(-1) for IL-2 and 250 pg mL(-1) for IL-15, they exhibited a very high positive predictive value (PPV), negative predictive value (NPV), sensitivity and specificity for survival (100% in all). A positive correlation was found between serum levels of both cytokines and APACHE II score (IL-2, r = 0.61, and IL-15, r = 0.62, respectively, and P < 0.0001 for both).

CONCLUSION

Determination of serum IL-2 and IL-15 levels may be a valuable and simple aid to improve identification of patients with ARDS or at risk for ARDS who are at high risk of subsequent mortality.

The predictive role of serum and bronchoalveolar lavage cytokines and adhesion molecules for acute respiratory distress syndrome development and outcome

BACKGROUND

The predictive role of many cytokines and adhesion molecules has not been studied systematically in acute respiratory distress syndrome (ARDS).

METHODS

We measured prospectively tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-1, soluble vascular adhesion molecule-1 (VCAM-1) and soluble intercellular adhesion molecule-1 (ICAM-1) in serum and bronchoalveolar lavage fluid (BALF) within 2 hours following admission, in 65 patients. The patients were divided into: those fulfilling the criteria for ARDS (n = 23, group A), those who were pre-ARDS and who developed ARDS within 24 hours (n = 14, group B), and those on pre-ARDS but who never developed ARDS (n = 28, group C).

RESULTS

All the measured molecules were only found at higher levels in the serum of patients that died either with or without ARDS (P < 0.05 - P < 0.0001). Patients at risk exhibited a good negative predictive value (NPV) of the measured molecules for ARDS development both in their serum (89 to 95%) and BALF (86 to 92%) levels. In contrast to BALF, serum levels of IL-1 and adhesion molecules exhibited a good NPV (68 to 96%), sensitivity (60 to 88%) and survival specificity (74 to 96%) in all groups. All molecules in serum and BALF IL-1 were correlated with the APACHE II (P < 0.05 - P < 0.0001). Serum and BALF IL-1 as well as BALF TNF-alpha were negatively correlated to PaO2/FiO2 (all P < 0.05).

CONCLUSIONS

The studied molecules have good NPV for ARDS development both in serum and BALF. Serum rather than BALF levels seem to be related to outcome.

Tumor necrosis factor-alpha and angiostatin are mediators of endothelial cytotoxicity in bronchoalveolar lavages of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized by an extensive alveolar capillary leak, permitting contact between intra-alveolar factors and the endothelium. To investigate whether factors contained in the alveolar milieu induce cell death in human lung microvascular endothelial cells, we exposed these cells in vitro to bronchoalveolar lavage fluid (BALF) supernatants from control patients, patients at risk of developing ARDS, and patients with early- and late-phase ARDS. In contrast to BALF from control patients, a significant cytotoxicity was found in BALF from patients at risk of developing ARDS, with late-phase ARDS, and especially from patients with early-phase ARDS. Subsequently, we determined the levels of factors known to exert cytotoxicity in endothelial cells, i.e., tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and angiostatin. BALF from patients at risk of developing ARDS, with early-phase ARDS, and with late-phase ARDS, contained increased levels of TNF-alpha and angiostatin, but not of TGF-beta1, as compared with BALF from control patients. Whereas inhibition of TGF-beta1 had no effect in this setting, neutralization of TNF-alpha or angiostatin inhibited the cytotoxic activity on endothelial cells of part of the early-phase ARDS BALF. These results indicate that TNF-alpha and angiostatin may contribute to ARDS-related endothelial injury.

Aerosolized ceftazidime for prevention of ventilator-associated pneumonia and drug effects on the proinflammatory response in critically ill trauma patients

STUDY OBJECTIVES

To evaluate the safety and efficacy of aerosolized ceftazidime for prevention of ventilator-associated pneumonia (VAP) and to evaluate the effects of the drug on the proinflammatory response.

DESIGN

Prospective, randomized, double-blind, placebo-controlled clinical trial.

SETTING

University teaching hospital.

PATIENTS

Forty critically ill trauma patients at high risk for VAP Intervention. Within 48 hours of admission to the intensive care unit (ICU), patients were randomly assigned to receive aerosolized ceftazidime 250 mg every 12 hours or placebo (normal saline) for up to 7 days. Bronchoalveolar concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 were determined at baseline and the end of therapy (days 4-7).

MEASUREMENTS AND MAIN RESULTS

The frequency of VAP in patients receiving aerosolized ceftazidime was 73% lower than that in patients receiving placebo at ICU day 14 (15% vs 55%, p = 0.021), and 54% lower for the entire ICU stay (30% vs 65%, p = 0.022). No clinically significant changes in bacterial culture and sensitivity patterns were observed. No adverse events from aerosolized ceftazidime were reported. Pulmonary TNF-alpha, IL-beta, and IL-8 concentrations were attenuated in the ceftazidime group compared with those in the placebo group (p < 0.001, p = 0.02, and p = 0.003). The frequency of VAP was related directly to changes in TNF-alpha and IL-beta (p < 0.001, p = 0.02).

CONCLUSIONS

Aerosolized ceftazidime decreased the frequency of VAP in critically ill trauma patients, without adversely affecting ICU flora. Aerosolized ceftazidime also may attenuate the proinflammatory response in the lung.

Injurious ventilation induces widespread pulmonary epithelial expression of tumor necrosis factor-alpha and interleukin-6 messenger RNA

OBJECTIVE

We examined the hypothesis that injurious strategies of mechanical ventilation alter the expression and distribution within the lung of tumor necrosis factor-alpha and interleukin-6 that are both duration and ventilation strategy dependent.

SUBJECTS

Male Sprague Dawley rats.

INTERVENTIONS

Lungs from rats were preserved immediately after death or were randomized to ex vivo ventilation with either a) noninjurious ventilation; b) high end-inspiratory lung volume with positive end-expiratory pressure (PEEP); c) high end-inspiratory lung volume without PEEP; or d) intermediate lung distension without PEEP, for periods ranging from 30 mins to 3 hrs.

MEASUREMENT AND MAIN RESULTS

Changes in cytokines were assessed by in situ hybridization, immunocytochemistry, simultaneous in situ hybridization and immunocytochemistry, Northern analysis, and enzyme-linked immunosorbent assay. Whereas minimal expression of tumor necrosis factor-alpha and interleukin-6 mRNA was found in lungs subjected to noninjurious ventilation, the three injurious strategies resulted in a diffuse increase in expression of tumor necrosis factor-alpha and interleukin-6. The principal cells involved were the bronchial, bronchiolar, and alveolar epithelium. The changes in tumor necrosis factor-alpha mRNA and protein expression were dependent on both duration of ventilation and the ventilation strategy used.

CONCLUSIONS

The vast pulmonary epithelium is a major contributor to ventilation-induced changes in cytokine production and may play an important role in the pathogenesis of lung injury and systemic sequelae in ventilated subjects.

Respiratory reovirus 1/L induction of diffuse alveolar damage: pulmonary fibrosis is not modulated by corticosteroids in acute respiratory distress syndrome in mice

Acute respiratory distress syndrome (ARDS) is a clinical syndrome characterized by diffuse alveolar damage (DAD) secondary to an intense host inflammatory response of the lung to a pulmonary or extrapulmonary infectious or noninfectious insult. We have previously described a unique animal model in which CBA/J mice infected with reovirus 1/L develop ARDS. This model recapitulates the histopathological changes observed in human ARDS, which consist of the overlapping phases of exudation, including the formation of hyaline membranes, regeneration, and healing via repair with fibrosis. In this report, we show that the development of DAD in the acute phase of the disease and intraalveolar fibrosis in the late phase of the disease was not modulated by treatment with methylprednisolone (MPS). In the presence or absence of MPS, the majority of cells infiltrating the lungs after reovirus 1/L infection were polymorphonuclear leukocytes and macrophages. A number of key proinflammatory and anti-inflammatory cytokines/chemokines that are observed in the BAL fluid of ARDS patients were also found in the lungs of mice after reovirus 1/L infection and were not modulated by MPS. These include interferon-gamma, interleukin-10, and monocyte chemoattractant protein. The histopathology, cytokine/chemokine expression, and response to corticosteroids in reovirus 1/L-induced ARDS are similar to what is observed in human patients, making this a clinically relevant model.

Activity of pulmonary edema fluid interleukin-8 bound to alpha(2)-macroglobulin in patients with acute lung injury

The formation of alpha(2)-macroglobulin (alpha(2)-M)/interleukin-8 (IL-8) complexes may influence the biological activity of IL-8 and the quantitative assessment of IL-8 activity. Therefore, in this study, concentrations of free IL-8 and IL-8 complexes with alpha(2)-M were measured in pulmonary edema fluid samples from patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and compared with control patients with hydrostatic pulmonary edema. Patients with ALI/ARDS had significantly higher concentrations of alpha(2)-M (P < 0.01) as well as alpha(2)-M/IL-8 complexes (P < 0.05). Because a substantial amount of IL-8 is complexed to alpha(2)-M, standard assays of free IL-8 may significantly underestimate the concentration of biologically active IL-8 in the distal air spaces of patients with ALI/ARDS. Furthermore, IL-8 bound to alpha(2)-M retained its biological activity, and this fraction of IL-8 was protected from proteolytic degradation. Thus complex formation may modulate the acute inflammatory process in the lung.

Inosine exerts a broad range of antiinflammatory effects in a murine model of acute lung injury

OBJECTIVE

To investigate the effects of inosine on the acute lung inflammation induced by lipopolysaccharide (LPS) in vivo and on the activation and cytotoxicity elicited by proinflammatory cytokines on human lung epithelial (A549) cells in vitro.

SUMMARY BACKGROUND DATA

Inosine is an endogenous purine recently shown to exert immunomodulatory and antiinflammatory effects.

METHODS

Mice challenged with intratracheal LPS (50 microg) were treated after 1, 6, and 12 hours with inosine (200 mg/kg intraperitoneal) or vehicle. After 24 hours, bronchoalveolar lavage fluid was obtained to measure proinflammatory (tumor necrosis factor-alpha [TNF-alpha], interleukin [IL]-1beta, IL-6), and antiinflammatory (IL-10, IL-4) cytokines, chemokines (MIP-1alpha and MIP-2), myeloperoxidase activity and total cell counts, nitric oxide production, and proteins. Lung histology and immunohistochemical detection of 3-nitrotyrosine, a marker of nitrosative stress, were performed in inflated-fixed lungs. In vitro, cell viability and production of the chemokine IL-8 were evaluated in A549 cells stimulated with a mixture of cytokines in the presence or absence of inosine.

RESULTS

Inosine downregulated the LPS-induced expression of TNF-alpha, IL-1beta, IL-6 and MIP-2 and tended to reduce MIP-1alpha, whereas it enhanced the production of IL-4. Total leukocyte counts, myeloperoxidase, nitric oxide production, and proteins were all significantly decreased by inosine. The purine also improved lung morphology and suppressed 3-nitrotyrosine staining in the lungs after LPS. Inosine attenuated the cytotoxicity and the expression of IL-8 induced by proinflammatory cytokines in A549 cells.

CONCLUSIONS

Inosine largely suppressed LPS-induced lung inflammation in vivo and reduced the toxicity of cytokines in lung cells in vitro. These data support the proposal that inosine might represent a useful adjunct in the therapy of acute respiratory distress syndrome.

Improved arterial oxygenation with biologically variable or fractal ventilation using low tidal volumes in a porcine model of acute respiratory distress syndrome

We compared biologically variable ventilation (V (bv); n = 9) with control mode ventilation (V (c); n = 8) at low tidal volume (VT)--initial 6 ml/kg--in a porcine model of acute respiratory distress syndrome (ARDS). Hemodynamics, respiratory gases, airway pressures, and VT data were measured. Static P-V curves were generated at 5 h. Interleukin (IL)-8 and IL-10 were measured in serum and tracheal aspirate. By 5 h, higher Pa(O(2)) (173 +/- 30 mm Hg versus 119 +/- 23 mm Hg; mean +/- SD; p < 0.0001 group x time interaction [G x T]), lower shunt fraction (6 +/- 1% versus 9 +/- 3%; p = 0.0026, G x T) at lower peak airway pressure (21 +/- 2 versus 24 +/- 1 cm H(2)O; p = 0.0342; G x T) occurred with V (bv). IL-8 concentrations in tracheal aspirate and wet:dry weight ratios were inversely related; p = 0.011. With V (c), IL-8 concentrations were 3.75-fold greater at wet:dry weight ratio of 10. IL-10 concentrations did not differ between groups. In both groups, ventilation was on the linear portion of the P-V curve. With V (bv), VT variability demonstrated an inverse power law indicating fractal behavior. In this model of ARDS, V (bv) improved Pa(O(2)) at lower peak airway pressure and IL-8 levels compared with V (c).

Pulmonary surfactant and inflammation in septic adult mice: role of surfactant protein A

Surfactant alterations, alveolar cytokine changes, and the role of surfactant protein (SP)-A in septic mice were investigated. Sepsis was induced via cecal ligation and perforation (CLP). Septic and sham mice were euthanized at 0, 3, 6, 9, 12, 15, and 18 h after surgery. Mice deficient in SP-A and mice that overexpressed SP-A were euthanized 18 h after surgery. In wild-type, sham-operated mice, surfactant pool sizes were similar at all time points, whereas in the CLP groups there was a significant decrease in small-aggregate surfactant pool sizes beginning 6 h after CLP. Interleukin-6 concentrations in bronchoalveolar lavage fluid from septic animals increased from 6 to 18 h after surgery. Identical surfactant alterations and concentrations of cytokines were observed in septic mice that were SP-A deficient or that overexpressed SP-A. In conclusion, alterations of pulmonary surfactant and alveolar cytokines occur simultaneously, 6 h after a systemic insult. In addition, we did not detect a role for SP-A in regulating surfactant phospholipid pool sizes or pulmonary inflammation in septic mice.

Clinical review: a paradigm shift: the bidirectional effect of inflammation on bacterial growth. Clinical implications for patients with acute respiratory distress syndrome

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. We hypothesized that cytokines secreted by the host during acute respiratory distress syndrome may indeed favor the growth of bacteria and explain the association between exaggerated and protracted systemic inflammation and the frequent development of nosocomial infections. To test this hypothesis, we conducted in vitro studies evaluating the extracellular and intracellular growth response of three clinically relevant bacteria in response to graded concentrations of pro-inflammatory cytokines tumor necrosis factor-alpha, IL-1beta, and IL-6. In these studies, we identified a U-shaped response of bacterial growth to pro-inflammatory cytokines. When the bacteria were exposed in vitro to a lower concentration of cytokines, extracellular and intracellular bacterial growth was not promoted and human monocytic cells were efficient in killing the ingested bacteria. Conversely, when bacteria were exposed to higher concentrations of pro-inflammatory cytokines, intracellular and extracellular bacterial growth was enhanced in a dose-dependent manner. The bidirectional effects of proinflammatory cytokines on bacterial growth may help to explain the frequent occurrence of nosocomial infections in patients with unresolving acute respiratory distress syndrome.

Cytokine balance in the lungs of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) involves an intense inflammatory response in the lungs, with accumulation of both pro- and antiinflammatory cytokines in bronchoalveolar lavage fluid (BALF). Our goal was to determine how the balance between pro- and antiinflammatory mediators in the lungs changes before and after the onset of ARDS. We identified 23 patients at risk for ARDS and 46 with established ARDS and performed serial bronchoalveolar lavage (BAL). We used immunoassays to measure tumor necrosis factor alpha (TNF-alpha) and soluble TNF-alpha receptors I and II; interleukin 1 beta (IL-1 beta), IL-1 beta receptor antagonist, and soluble IL-1 receptor II; IL-6 and soluble IL-6 receptor; and IL-10. We used sensitive bioassays to measure net TNF-alpha, IL-1 beta, and IL-6 activity. Although individual cytokines increased before and after onset of ARDS, greater increases occurred in cognate receptors and/or antagonists, so that molar ratios of agonists/antagonists declined dramatically at the onset of ARDS. The molar ratios remained low for 7 d or longer, limiting the activity of soluble IL-1 beta and TNF-alpha in the lungs at the onset of ARDS. This significant antiinflammatory response early in ARDS may provide a key mechanism for limiting the net inflammatory response in the lungs.

Coagulation blockade prevents sepsis-induced respiratory and renal failure in baboons

Sepsis-induced tissue factor (TF) expression activates coagulation in the lung and leads to a procoagulant environment, which results in fibrin deposition and potentiates inflammation. We hypothesized that preventing initiation of coagulation at TF-Factor VIIa (FVIIa) complex would block fibrin deposition and control inflammation in sepsis, thereby limiting acute lung injury (ALI) and other organ damage in baboons. A model of ALI was used in which adult baboons were primed with killed Escherichia coli (1 x 10(9) CFU/kg), and bacteremic sepsis was induced 12 h later by infusion of live E. coli at 1 x 10(10) CFU/kg. Animals in the treatment group were given a competitive inhibitor of TF, site-inactivated FVIIa (FVIIai), intravenously at the time of the infusion of live bacteria and monitored physiologically for another 36 h. FVIIai dramatically protected gas exchange and lung compliance, prevented lung edema and pulmonary hypertension, and preserved renal function relative to vehicle (all p < 0.05). Treatment attenuated sepsis-induced fibrinogen depletion (p < 0.01) and decreased systemic proinflammatory cytokine responses, for example, interleukin 6 (p < 0.01). The protective effects of TF blockade in sepsis-induced ALI were confirmed by using tissue factor pathway inhibitor. The results show that TF-FVIIa complex contributes to organ injury in septic primates in part through selective stimulation of proinflammatory cytokine release and fibrin deposition.

Effects of methylprednisolone on intracellular bacterial growth

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. Patients presenting with acute respiratory distress syndrome (ARDS) and high levels of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), and IL-6, have increased risk for developing nosocomial infections attributable to organisms such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., compared to those patients with lower levels. Our previous in vitro studies have demonstrated that these bacterial strains exhibit enhanced growth extracellularly when supplemented with high concentrations of pure recombinant TNF-alpha, IL-1 beta, or IL-6. In addition, we have shown that the intracellular milieu of phagocytic cells that are exposed to supraoptimal concentrations of TNF-alpha, IL-1 beta, and IL-6 or lipopolysaccharide (LPS) favors survival and replication of ingested bacteria. Therefore, we hypothesized that under conditions of intense inflammation the host's micromilieu favors bacterial infections by exposing phagocytic cells to protracted high levels of inflammatory cytokines. Our clinical studies have shown that methylprednisolone is capable of reducing the levels of TNF-alpha, IL-1 beta, and IL-6 in ARDS patients. Hence, we designed a series of in vitro experiments to test whether human monocytic cells (U937 cells) that are activated with high concentrations of LPS, which upregulate the release of proinflammatory cytokines from these phagocytic cells, would effectively kill or restrict bacterial survival and replication after exposure to methylprednisolone. Fresh isolates of S. aureus, P. aeruginosa, and Acinetobacter were used in our studies. Our results indicate that, compared with the control, stimulation of U937 cells with 100-ng/ml, 1.0-microg/ml, 5.0-microg/ml, or 10.0-microg/ml concentrations of LPS enhanced the intracellular survival and replication of all three species of bacteria significantly (for all, P = 0.0001). Stimulation with < or =10.0 ng of LPS generally resulted in efficient killing of the ingested bacteria. Interestingly, when exposed to graded concentrations of methylprednisolone, U937 cells that had been stimulated with 10.0 microg of LPS were able to suppress bacterial replication efficiently in a concentration-dependent manner. Significant reduction in numbers of CFU was observed at > or =150 microg of methylprednisolone per ml (P values were 0.032, 0.008, and 0.009 for S. aureus, P. aeruginosa, and Acinetobacter, respectively). We have also shown that steady-state mRNA levels of TNF-alpha, IL-1 beta, and IL-6 in LPS-activated cells were reduced by treatment of such cells with methylprednisolone, in a concentration-dependent manner. The effective dose of methylprednisolone was 175 mg, a value that appeared to be independent of priming level of LPS and type of mRNA. We therefore postulate that a U-shaped relationship exists between the level of expression of TNF-alpha, IL-1 beta, and IL-6 within the phagocytic cells and their abilities to suppress active survival and replication of phagocytized bacteria.

Transcriptional mechanisms of acute lung injury

Acute lung injury occurs as a result of a cascade of cellular events initiated by either infectious or noninfectious inflammatory stimuli. An elevated level of proinflammatory mediators combined with a decreased expression of anti-inflammatory molecules is a critical component of lung inflammation. Expression of proinflammatory genes is regulated by transcriptional mechanisms. Nuclear factor-kappa B (NF-kappa B) is one critical transcription factor required for maximal expression of many cytokines involved in the pathogenesis of acute lung injury. Activation and regulation of NF-kappa B are tightly controlled by a complicated signaling cascade. In acute lung injury caused by infection of bacteria, Toll-like receptors play a central role in initiating the innate immune system and activating NF-kappa B. Anti-inflammatory cytokines such as interleukin-10 and interleukin-13 have been shown to suppress inflammatory processes through inhibiting NF-kappa B activation. NF-kappa B can interact with other transcription factors, and these interactions thereby lead to greater transcriptional selectivity. Modification of transcription is likely to be a logical therapeutic target for acute lung injury.

Involvement of tyrosine phosphatase PTP1D in the inhibition of interleukin-6-induced Stat3 signaling by alpha-thrombin

We previously demonstrated that exposure of CCL39 lung fibroblasts to alpha-thrombin inhibits interleukin-6 (IL-6)-induced tyrosine phosphorylation of Stat3 (signal transducers and activators of transcription 3) via activation of mitogen-activated protein (MAP) kinase kinase 1 [Bhat et al. (1998) Arch. Biochem. Biophys. 350, 307-314]. In this study, using CCL39/MRC-5 cells, we investigated if additional signaling intermediates are involved in alpha-thrombin's inhibitory effects on IL-6-induced Stat3 signaling. We also determined if alpha-thrombin inhibits oncostatin M (OSM)-induced Stat3/Stat1, and interferon-gamma (IFN-gamma)-induced Stat1 tyrosine phosphorylation. We demonstrate that, although both IL-6 and OSM belong to the same cytokine family, alpha-thrombin inhibited only the IL-6-induced Stat3 tyrosine phosphorylation. The tyrosine phosphatase PTP1D coprecipitated with Stat3 from alpha-thrombin + IL-6, but not from alpha-thrombin + OSM-treated cells. Pretreatment of cells with a phosphatase inhibitor reversed the inhibitory actions of alpha-thrombin, suggesting a role for PTP1D in alpha-thrombin-mediated inhibition of IL-6-induced Stat3 signaling. Interestingly, alpha-thrombin failed to inhibit OSM- and IFN-gamma-induced Stat1 tyrosine phosphorylation. Cytokine-specific inhibition of the Stat3 signaling involving MAP kinase kinase 1 and PTP1D by alpha-thrombin may play an important role in regulation of gene expression.

Early trauma polymorphonuclear neutrophil responses to chemokines are associated with development of sepsis, pneumonia, and organ failure

OBJECTIVES

The modulation of polymorphonuclear neutrophil (PMN) function by injury is unpredictable, and can predispose either to hyperimmune states (adult respiratory distress syndrome [ARDS], multiple organ failure) or to immune dysfunction, infection, and sepsis. Such outcomes have been related to excess production of the CXC chemokine interleukin (IL)-8, but PMN responses to IL-8 are mediated by both the relatively stable and IL-8 specific CXC receptor 1 (CXCR1) and the labile, promiscuous CXCR2. We hypothesized that progression to septic and multiple organ failure outcomes could be related to early differences in PMN CXC receptor status.

METHODS

PMNs were isolated 12 +/- 3 hours after injury from 15 major trauma patients (Injury Severity Score of 34 +/- 2, 11 men and 4 women, age 36 +/- 4 years) who survived at least 7 days. Volunteer normal PMNs (n = 6 donors) were studied for comparison. Cells were stimulated either with the CXCR2 specific agent growth-related oncogene-alpha, or with IL-8, which stimulates CXCR1 and CXRR2. Receptor response was assessed as the mobilization of cell calcium. The development of ARDS, sepsis, and pneumonia was assessed according to standardized criteria. Day 1 receptor activity in the clinical groups was then compared by analysis of variance with Tukey's or t tests as appropriate.

RESULTS

In patients that were otherwise comparable, CXCR2 responses were markedly diminished in the PMNs of patients who went on to sepsis and pneumonia, but were elevated in PMNs from the patients who went on to ARDS. CXCR1 responses were modestly lower in trauma patients than volunteers, but showed no significant variations among the various clinical outcome groups.

CONCLUSION

The activity of PMN CXCR2 receptors soon after injury may be reflected in the later clinical sequelae of PMN activity. High CXCR2 activity may correlate with PMN hyperfunction and outcomes such as ARDS, whereas the loss of CXCR2 function in inflammatory environments may impair PMN functions in a manner that predisposes to pneumonia or sepsis. Early responses of PMN CXC receptors to injury may influence the clinical course of trauma patients.

Vitronectin and fibronectin function as glucan binding proteins augmenting macrophage responses to Pneumocystis carinii

beta-glucans represent major structural components of fungal cell walls. We recently reported that Pneumocystis carinii beta-glucans stimulate alveolar macrophages to release proinflammatory cytokines. Macrophage activation by beta-glucan is augmented by serum, implying the presence of circulating factors that interact with beta-glucans and enhance their ability to stimulate macrophages. Using beta-glucan-enriched cell wall fractions from P. carinii and Saccharomyces cerevisiae, two prominent proteins were precipitated from serum and demonstrated to be vitronectin (VN) and fibronectin (FN) by immune analysis. Preincubation of beta-glucan with VN or FN enhanced macrophage activation in response to this cell wall component. Because VN and FN accumulate in the lungs during P. carinii pneumonia, we further investigated hepatic and pulmonary expression of VN and FN messenger RNA during infection. P. carinii pneumonia in rodents is associated with increased hepatic expression of VN and FN as well as increased local expression of FN in the lung. Because interleukin (IL)-6 represents the major regulator of VN and FN expression during inflammatory conditions, we measured macrophage IL-6 release in response to stimulation with P. carinii beta-glucan. Stimulation of macrophages with P. carinii beta-glucan induced significant release of IL-6. Elevated concentrations of IL-6 were noted in the blood of infected animals compared with uninfected control animals. These studies indicate that VN and FN bind to beta-glucan components of P. carinii and augment macrophage inflammatory responses. P. carinii cell wall beta-glucan stimulates secretion of IL-6 by macrophages, thereby enhancing hepatic synthesis of both VN and FN, and lung synthesis of FN during pneumonia.

Evaluation of basement membrane degradation during TNF-alpha-induced increase in epithelial permeability

We evaluated whether tumor necrosis factor (TNF)-alpha induces an increase in permeability of an alveolar epithelial monolayer via gelatinase secretion and basement membrane degradation. Gelatinase secretion and epithelial permeability to radiolabeled albumin under unstimulated and TNF-alpha-stimulated conditions of an A549 human epithelial cell line were evaluated in vitro. TNF-alpha induced both upregulation of a 92-kDa gelatinolytic activity (pro form in cell supernatant and activated form in extracellular matrix) and an increase in the epithelial permeability coefficient compared with the unstimulated condition (control: 1.34 +/- 0.04 x 10(-6) cm/s; 1 microg/ml TNF-alpha: 1.47 +/- 0.05 x 10(-6) cm/s, P < 0.05). The permeability increase in the TNF-alpha-stimulated condition involved both paracellular permeability, with gap formation visualized by actin cytoskeleton staining, and basement membrane permeability, with an increase in the basement membrane permeability coefficient (determined after cell removal; control: 2.58 +/- 0.07 x 10(-6) cm/s; 1 microg/ml TNF-alpha: 2.82 +/- 0.02.10(-6) x cm/s, P < 0.05). Because addition of gelatinase inhibitors [tissue inhibitor of metalloproteinase (TIMP)-1 or BB-3103] to cell supernatants failed to inhibit the permeability increase, the gelatinase-inhibitor balance in the cellular microenvironment was further evaluated by cell culture on a radiolabeled collagen matrix. In the unstimulated condition, spontaneous collagenolytic activity inhibited by addition to the matrix of 1 microg/ml TIMP-1 or 10(-6) M BB-3103 was found. TNF-alpha failed to increase this collagenolytic activity because it was associated with dose-dependent upregulation of TIMP-1 secretion by alveolar epithelial cells. In conclusion, induction by TNF-alpha of upregulation of both the 92-kDa gelatinase and its inhibitor TIMP-1 results in maintenance of the gelatinase-inhibitor balance, indicating that basement membrane degradation does not mediate the TNF-alpha-induced increase in alveolar epithelial monolayer permeability.

Vascular endothelial growth factor synthesis in the acute phase of experimental and clinical lung injury

Vascular endothelial growth factor (VEGF) is a potent angiogenic and endothelial survival factor, which is abundantly expressed in the normal lung. Conceivably, VEGF may be released by numerous cell types found around the airspaces, including alveolar type 2 cells, alveolar macrophages, and polymorphonuclear neutrophils. Using a bacteria-induced lung injury model in rats, VEGF expression in lung was investigated. Both VEGF protein and VEGF messenger ribonucleic acid (mRNA), 4 and 24 h after bacterial challenge (Pseudomonas aeruginosa), were decreased compared with sham rats. VEGF protein was also investigated in bronchoalveolar lavage (BAL) from patients studied within 7 days of acute respiratory distress syndrome (ARDS) onset and in patients without ARDS. VEGF protein levels in BAL were decreased in patients with ARDS versus those without (14.3 +/- 11.1 pg x mL(-1) versus 76.8 +/- 51.1 pg x mL(-1), p = 0.03). In aggregate, these findings show that the initial phase of acute lung injury is associated with a decrease in vascular endothelial growth factor in the lung. This downregulation may represent a protective mechanism aimed at limiting endothelial permeability, and may participate in the decrease in capillary number that is observed during early acute respiratory distress syndrome.

Correlation between serum IL-6 levels and death: usefulness in diagnosis of "traumatic shock"?

Interleukin-6 (IL-6) has been considered as an important mediator of inflammation. Clinically it is a well-known marker of the severity of injury following major trauma. In this study, the levels of IL-6 in body serum were applied to a traumatic death index. Of ninety victims 55 were men and 35 women, with a mean age of 53.4+/- 19 (S.D.) years. The cases were classified as traumatic deaths (38 cases), non-traumatic deaths other than natural causes of deaths (36 cases), and deaths due to natural causes (16 cases). All samples were collected within 2 days after death. The mean values of IL-6 levels of the traumatic, non-traumatic and disease groups were 8608.97, 2205.65, and 3266.64 pg/ml, respectively. Some cases in non-traumatic and disease cases were beyond 10 000 pg/ml, however, the mean value of the traumatic group was statistically higher than that of the other two groups. Even though several cases had high levels of IL-6 in spite of instantaneous death, the results showed that IL-6 levels are helpful in the diagnosis of traumatic shock.

Interleukin-6 production in lung tissue after transthoracic esophagectomy

BACKGROUND

The mechanisms of the reported high increase in interleukin-6 (IL-6) levels after esophagectomy are unclear. We investigated the influence of an intrathoracic procedure, esophagectomy, on IL-6 production in lung tissue.

STUDY DESIGN

Fourteen paired lung tissue samples were obtained from patients before and after they underwent transthoracic esophagectomy for esophageal cancer. IL-6 levels in the lung were measured with enzyme-linked immunosorbent assay, and IL-6 mRNA expression was determined with real-time quantitative reverse transcription-polymerase chain reaction. Immunohistochemical staining was used to localize IL-6, and circulating levels were also measured.

RESULTS

IL-6 protein and mRNA were significantly increased in lung tissue after this intrathoracic procedure (p < 0.05). Peak levels of plasma IL-6 after surgery were correlated with IL-6 levels in lung tissues obtained after the procedure (p < 0.05). Immunohistochemical staining revealed IL-6 production from alveolar and bronchial epithelial cells but not from alveolar macrophages.

CONCLUSIONS

Transthoracic esophagectomy causes an increase in IL-6 production from airway epithelial cells, secondary to increased expression of IL-6 mRNA. Local response of lung tissue may be one source of increased serum IL-6 after this procedure.

Anti-interleukin 8 autoantibody: interleukin 8 complexes in the acute respiratory distress syndrome. Relationship between the complexes and clinical disease activity

Increased levels of interleukin 8 (IL-8) are found in bronchoalveolar lavage (BAL) fluids from patients with the acute respiratory distress syndrome (ARDS). However, IL-8 is not an efficient predictor of the course of ARDS. Our prior studies demonstrated that IL-8 present in lung fluids from patients with ARDS is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 complexes). These data led us to hypothesize that the complexes might better predict the development of acute lung injury. Accordingly, we measured concentrations of free and complexed IL-8 in BAL fluids from 19 patients at risk and 45 with established ARDS on Days 1, 3, 7, 14, and 21 after the onset of ARDS. The concentrations of anti-IL-8:IL-8 complexes in patients with ARDS on Day 1 were significantly higher than in patients at risk (p < 0.05). There was a significant association between anti-IL-8:IL-8 complex concentrations and the onset of ARDS (p = 0.03). Similarly, anti-IL-8:IL-8 complex concentrations were significantly higher in patients on Day 1 of ARDS who later died (p < 0.05), and the association between high anti-IL-8: IL-8 complex concentrations and the probability of dying was significant (p = 0.03). The presence of anti-IL-8:IL-8 complexes in BAL fluids of patients with ARDS is an important prognostic indicator for the development and outcome of ARDS.

Nitric oxide and nitrotyrosine in the lungs of patients with acute respiratory distress syndrome

Nitric oxide (NO) end-products (nitrate and nitrite) are present in bronchoalveolar lavage (BAL) fluid of patients with inflammatory lung diseases. Reactive oxygen-nitrogen intermediates damage macromolecules by oxidation or nitration of critical residues in proteins. The goal of this study was to measure NO end-products (nitrate+ nitrite), in BAL fluid before and after the onset of acute respiratory distress syndrome (ARDS) and to determine if these products are associated with expression of inducible nitric oxide synthase enzyme (iNOS) in BAL cells and nitration of BAL proteins. We performed bronchoalveolar lavage (BAL) in patients at risk for ARDS (n = 19), or with ARDS (n = 41) on Days 1, 3, 7, 14, and 21 after onset, and measured total nitrite (after reducing nitrate to nitrite) and protein-associated nitrotyrosine concentration in each BAL fluid sample. Cytospin preparations of BAL cells were analyzed by immunocytochemistry for iNOS and nitrotyrosine. Nitrate+nitrite were detected in BAL fluid from patients at risk for ARDS, and for as long as 21 d after the onset of ARDS. Nitrotyrosine was detectable in all BAL fluid samples for as long as 14 d after the onset of ARDS (range, 38.8 to 278.5 pmol/mg of protein), but not in BAL of normal volunteers. Alveolar macrophages of patients with ARDS were positive for iNOS and nitrotyrosine, and remained positive for as long as 14 d after onset of ARDS. The BAL nitrate+nitrite did not predict the onset of ARDS, but the concentration was significantly higher on Days 3 and 7 of ARDS in patients who died. Thus, NO end products accumulate in the lungs before and after onset of ARDS; iNOS is expressed at high levels in AM during ARDS; and nitration of intracellular and extracellular proteins occurs in the lungs in ARDS. The data support the concept that NO-dependent pathways are important in the lungs of patients before and after the onset of ARDS.

Ventilator-induced lung injury is associated with neutrophil infiltration, macrophage activation, and TGF-beta 1 mRNA upregulation in rat lungs

Activated neutrophils contribute to the development of ventilator-induced lung injury (VILI) caused by high-pressure mechanical ventilation. However, exact cellular and molecular mechanisms have not been conclusively studied. Our investigation aimed to examine expression of adhesion molecules by both neutrophils and macrophages in lung lavage fluids of rats with VILI. Further, involvement of proinflammatory (tumor necrosis factor-alpha) and profibrogenetic (transforming growth factor-beta 1) mediators was analyzed at mRNA level in lung tissue. Wistar rats were ventilated by high pressure (45 cm H(2)O of peak inspiratory pressure, n = 23) or low pressure (7 cm H(2)O, n = 13) with 0 positive end-expiratory pressure. After 40 min of comparative ventilation, lung lavage was performed in 20 rats from the experimental group and 10 from the control for immunofluorescence analysis with anti-Mac-1 and anti-ICAM-1 monoclonal antibodies. The lung tissues from remaining rats were subjected to pathological and reverse transcription-polymerase chain reaction examinations. Although there was no significant change of PaO(2) in the low-pressure group, PaO(2) was decreased in the high-pressure group. The high-pressure group also had greater neutrophil infiltration into alveolar spaces, upregulation of CD54 and CD11b on alveolar macrophages, and more transforming growth factor-beta 1 mRNA in lung tissues. Tumor necrosis factor-alpha was not involved in the pathogenesis of the severe VILI observed. Histologic findings also demonstrated more infiltrating neutrophils, destructive change of the alveolar wall, and deposition of matrix in the high-pressure group. These results suggest that a series of proinflammatory reactions and profibrogenetic process may be involved in the course of VILI.

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.

Fibroproliferation occurs early in the acute respiratory distress syndrome and impacts on outcome

The fibroproliferative phase of acute respiratory distress syndrome (ARDS) has traditionally been regarded as a late event but recent studies that suggest increased lung collagen turnover within 24 h of diagnosis challenge this view. We hypothesized that fibroproliferation is initiated early in ARDS, characterized by the presence of fibroblast growth factor activity in the lung and would relate to clinical outcome. Patients fulfilling American/European Consensus Committee criteria for ARDS and control patients ventilated for non-ARDS respiratory failure underwent bronchoalveolar lavage (BAL) and serum sampling within 24 h of diagnosis and again at 7 d. The ability of BAL fluid (BALF) to stimulate human lung fibroblast proliferation in vitro was examined in relation to concentrations of N-terminal peptide for type III procollagen (N-PCP-III) in BALF/serum and clinical indices. At 24 h, ARDS lavage fluid demonstrated potent mitogenic activity with a median value equivalent to 70% (range 31-164) of the response to serum, and was significantly higher than control lavage (32% of serum response, range 11-42; p < 0.05). At 24 h, serum N-PCP-III concentrations were elevated in the ARDS group compared with control patients (2.8 U/ml; range 0.6-14.8 versus 1.1 U/ml; range 0.4-3.7, p < 0.0001) as were BALF N-PCP-III concentrations (2.9 U/ml; range 0. 6-11.4 versus 0.46 U/ ml; range 0.00-1.63, p < 0.01). In addition, BALF N-PCP-III concentrations at 24 h were significantly elevated in nonsurvivors of ARDS compared with survivors (p < 0.05). At 7 d, the mitogenic activity remained elevated in the ARDS group compared with control (p < 0.05) and was also significantly higher in ARDS nonsurvivors compared with survivors (67%; range 45-120 versus 31%; range 16-64, p < 0.05). These data are consistent with the hypothesis that fibroproliferation is an early response to lung injury and an important therapeutic target.

High oxygen concentration exacerbates cardiopulmonary bypass-induced lung injury

OBJECTIVE

To investigate the effect of ventilation with 100% oxygen on lung injury associated with surgery involving cardiopulmonary bypass (CPB).

DESIGN

A prospective randomized study.

SETTING

University hospital.

PARTICIPANTS

Thirty patients undergoing coronary artery bypass graft surgery with CPB.

INTERVENTIONS

Patients were randomized to receive 100% oxygen (Oxygen group) or 50% oxygen (Air group) throughout surgery. During CPB, patients' lungs in the Air group were flushed with air and in the Oxygen group with 100% oxygen.

MEASUREMENTS AND MAIN RESULTS

Lung injury was evaluated by arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio and cytokine levels (tumor necrosis factor-alpha and interleukin-8) in blood and bronchoalveolar lavage fluid measured before and after CPB. The lowest PaO2-FIO2 value was observed after 40 minutes following the completion of CPB in both groups. PaO2-FIO2 values 6 hours after CPB were not different from baseline in the Air group but remained lower (359+/-63 mmHg and 298+/-78 mmHg; p = 0.013) in the Oxygen group. Blood cytokine levels rose during surgery in both groups. Bronchoalveolar lavage levels of interleukin-8 did not change, whereas tumor necrosis factor-alpha increased only in the Oxygen group (p = 0.035).

CONCLUSIONS

A significant decrease of oxygenation was observed in the early post-CPB period in both groups of patients, with delay in recovery in patients treated with 100% oxygen. A larger increase of the proinflammatory cytokines was found in patients treated with 100% oxygen. High oxygen concentrations during surgery with CPB should be used only when specifically required.

Mechanisms of repair and remodeling following acute lung injury

At present, we largely lack the ability to correlate the clinical course of ARDS patients with potential factors involved in the biochemical and cellular basis of lung repair. This requires very large patient databases with measurement of many biochemical parameters. Important mechanistic determinants during the repair phase can be sought by correlation with late outcomes, but a large-scale cooperative effort among multiple centers with sharing of follow-up data and patient specimens is essential. We also lack detailed human histologic material from many phases of ARDS and, particularly, know little of the long-term morphologic impact of ARDS in survivors. Establishment of a national registry that follows ARDS survivors and that would seek their cooperation in advance in obtaining autopsy specimens when they die of other causes would be very valuable. Correlating the pathology with their pulmonary function during recovery would give important insights into the reasons for the different patterns of abnormal pulmonary functions. The factors that determine the success of repair are of critical importance in testing new ARDS treatment strategies. Would accelerating the resolution of alveolar edema alter the course of subsequent fibrosis and inflammation? Does surfactant replacement therapy--a costly proposition in adults with ARDS--lead to better long-term outcomes in survivors? How much should we worry about the use of high levels of oxygen for support of arterial partial pressure of oxygen? Is it better to accept hyperoxia to avoid pressure or volume trauma induced by mechanical ventilation with higher minute ventilations? These major management issues all may affect the success of the late repair and recovery process. Intervention trials need to examine the long-term physiologic and functional outcomes.

Acute respiratory distress syndrome. Potential pharmacologic interventions

Remarkable progress has been made in the past 10 years with regard to understanding the interplay of potent physiologic mediators in patients with acute lung injury. Because there are so many mediators and the interaction of these agents is complex, true insight into the process has been slow in coming. Clinical studies in ARDS, as well as sepsis, the leading cause of ARDS, have increased in number, size, and quality over this same period. Although none of these studies has produced an accepted new therapy for ARDS, each has laid the groundwork for more efficient and more elegant studies of the problem. The stage is now set for the real advances to be brought forward and put to rigorous, efficient clinical testing.

Liposome-encapsulated hemoglobin does not exacerbate endotoxin-induced lung injury

OBJECTIVE

To test the hypothesis that liposome encapsulated hemoglobin (LEH), an experimental oxygen-carrying fluid, exacerbates endotoxin-induced lung injury in the rat.

DESIGN

Prospective, randomized animal study.

SETTING

University animal laboratory.

METHODS

Anesthetized Sprague-Dawley rats (n = 8-13) were infused with LEH (10% of estimated total blood volume) or vehicle (0.9% NaCl). Thirty minutes later, Escherichia coli endotoxin (3.6 mg/kg, i.v.) or vehicle (0.9% NaCl) was administered, and skeletal muscle oxygen tension as well as lung injury were assessed at 2, 4, and 8 hrs. Oxygen tension was measured using a miniaturized thin film oxygen sensor placed in the rectus abdominis muscle, and lung injury was evaluated by determining lung weights, lung myeloperoxidase activity, lung tissue tumor necrosis factor-alpha level, and protein concentration in bronchoalveolar lavage fluid.

RESULTS

The intravenous bolus injection of E. coli endotoxin elevated lung water content (33% +/- 5%; p < .01 vs. sham controls), myeloperoxidase activity (56% +/- 6%; p < .01), and tumor necrosis factor-alpha production (1320 +/- 154 pg/g lung tissue; p < .05 vs. undetected levels in sham controls), as well as induced protein accumulation in bronchoalveolar lavage fluid (258% +/- 38%; p < .01) and skeletal muscle hypoxia (52 +/- 8 mm Hg; p < .05). Pretreatment with LEH, which when infused alone did not induce lung injury, had no effect on these responses.

CONCLUSION

In this specific model of endotoxin-induced lung injury, LEH does not exacerbate microvascular leakage and leukosequestration, the hallmarks of adult respiratory distress syndrome.

Neutrophils regulate their own apoptosis via preservation of CXC receptors

BACKGROUND

Dysregulated neutrophil (PMN) apoptosis is thought to contribute to an exaggerated inflammatory response in diseases such as acute respiratory distress syndrome (ARDS) and multiple organ dysfunction syndrome (MODS). The CXC chemokines, interleukin-8 (IL-8) and growth-related oncogene alpha (Gro-alpha), contribute to the inflammatory response and suppress PMN apoptosis. We hypothesized that PMN generation of CXC chemokines is an autocrine/paracrine mechanism for amplification of the PMN inflammatory response via suppression of apoptosis.

METHODS

Freshly isolated human PMNs from healthy donors were incubated with IL-8 or Gro-alpha (100 ng/ml) for 0-12 h, and apoptosis was analyzed at 24 h. De novo synthesis of IL-8 or Gro-alpha was measured using an ELISA. To determine if receptors were available to bind these newly synthesized ligands (125)I radiolabeled monoclonal antibodies specific for each receptor (CXCRI, CXCRII) were used to determine PMN receptor density. Comparison was by one-way ANOVA.

RESULTS

Significant suppression of apoptosis was seen at 24 h with only 4 h exposure to IL-8 or Gro-alpha (n = 5, P < 0.05). PMNs cultured with IL-8 for 4 h produced 31 +/- 4.3 ng/ml IL-8 by 24 h; PMNs cultured with Gro-alpha produced 19.7 +/- 4.0 ng/ml Gro-alpha (n = 6, P < 0. 05). Neither chemokine induced significant production of the other chemokine. The addition of either ligand promoted upregulation of CXCR1 (n = 4, P < 0.05) at 24 h. However, CXCR2 was downregulated by Gro-alpha and IL-8 to 71 +/- 7.5 and 79 +/- 6.3% of control, respectively (P < 0.05).

CONCLUSION

IL-8 and Gro-alpha, which suppress apoptosis, stimulate their own production after short-term incubation with PMNs. PMNs maintain the ability to respond to these chemokines through expression of the CXC receptors which suggests that PMNs are active participants in the suppression of apoptosis at inflammatory sites. CXCRI remains upregulated after prolonged stimulation and may be an important target for mediating neutrophil responses to IL-8.

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.

Association among filamentous actin content, CD11b expression, and membrane deformability in stimulated and unstimulated bovine neutrophils

OBJECTIVE

To investigate rheologic properties of bovine neutrophils that may result in adhesion molecule-independent sequestration of neutrophils in inflamed lungs of cattle.

ANIMALS

Healthy 2- to 4-week-old male Holstein calves.

PROCEDURES

Neutrophil deformability, filamentous actin (F-actin) content, and CD11b expression was determined for unstimulated bovine neutrophils and bovine neutrophils incubated with the inflammatory mediators tumor necrosis factor-alpha (TNF), platelet-activating factor (PAF), interleukin-8 (IL-8), zymosan-activated plasma (ZAP), Pasteurella haemolytica-derived lipopolysaccharide (LPS), and P haemolytica leukotoxin. Neutrophils were separated into 3 subpopulations on the basis of size. The Factin content and CD11 b expression were evaluated by use of flow cytometry. Leukocyte deformability was evaluated by filtration of dilute whole blood.

RESULTS

The subpopulation of the smallest-sized neutrophils (>90% of neutrophils) contained little F-actin. A subpopulation of slightly larger neutrophils had a profound increase in F-actin content and CD11 b expression. The subpopulation of the largest neutrophils had increased F-actin content and CD11b expression, compared with those for both subpopulations of smaller neutrophils. Incubation of neutrophils with PAF and ZAP but not TNF, IL-8, LPS, or leukotoxin, resulted in decreased neutrophil deformability and increased F-actin content. Incubation with PAF and TNF induced an increase in size of neutrophils.

CONCLUSIONS AND CLINICAL RELEVANCE

Size can be used to identify subpopulations of large and rigid neutrophils in blood samples from healthy calves. Platelet-activating factor and activated complement fragments are potent inducers of F-actin formation and neutrophil rigidity. Physical changes in neutrophils may impede their transit through lung microvasculature and result in leukocyte trapping independent of adhesion molecule interactions with endothelial cells.

Dose-response to inhaled aerosolized prostacyclin for hypoxemia due to ARDS

STUDY OBJECTIVES

This study was carried out to determine the efficacy of and dose-response relationships to inhaled aerosolized prostacyclin (IAP), when used as a selective pulmonary vasodilator (SPV) in patients with severe hypoxemia due to ARDS.

DESIGN

Unblinded, interventional, prospective clinical study.

SETTING

A general ICU in a university-affiliated, tertiary referral center.

PATIENTS

Nine adult patients with severe ARDS (lung injury score, > or = 2.5).

INTERVENTIONS

All patients received IAP over the dose range 0 to 50 ng/kg/min. The IAP was delivered via a jet nebulizer placed in the ventilator circuit. Dose increments were 10 ng/kg/min every 30 min.

MEASUREMENTS AND RESULTS

Cardiovascular parameters (cardiac index and mean pulmonary and systemic pressures), indexes of oxygenation (PaO(2)/fraction of inspired oxygen [FIO(2)] ratio and alveolar-arterial oxygen partial pressure difference [P(A-a)O(2)]) and shunt fraction were measured or calculated at each dose interval, as were platelet aggregation and systemic levels of prostacyclin metabolite (6-keto prostaglandin F1(alpha)). A generalized linear regression model was used to determine a dose effect of IAP on these parameters. The Wilcoxon rank sum test for related measures was used to compare the effects of various doses of IAP. IAP acted as an SPV, with a statistically significant dose-related improvement in PaO(2)/FIO(2) ratio (p = 0.003) and P(A-a)O(2) (p = 0.01). Systemic prostacyclin metabolite levels increased significantly in response to delivered IAP (p = 0.001). There was no significant dose effect on systemic or pulmonary arterial pressures, or on platelet function, as determined by platelet aggregation in response to challenge with adenosine diphosphate.

CONCLUSIONS

IAP is an efficacious SPV, with marked dose-related improvement in oxygenation and with no demonstrable effect on systemic arterial pressures over the dose range 0 to 50 ng/kg/min. Despite significant systemic levels of prostacyclin metabolite, there was no demonstrable platelet function defect.

Phospholipid synthesis by Staphylococcus aureus during (Sub)Lethal attack by mammalian 14-kilodalton group IIA phospholipase A2

Killing of gram-positive bacteria by mammalian group IIA phospholipases A2 (PLA2) requires the catalytic activity of the enzyme. However, nearly complete degradation of the phospholipids can occur with little effect on bacterial viability, suggesting that PLA2-treated bacteria can biosynthetically replace phospholipids that are lost due to PLA2 action. In the presence of albumin, phospholipid degradation products are quantitatively sequestered extracellularly. In the absence of albumin, the bacteria retain and substantially reutilize the phospholipid breakdown products and survive an otherwise lethal dose of PLA2. PLA2-treated bacteria also continue to incorporate sodium [2-(14)C]acetate into phospholipids, suggesting that the bacteria are attempting to repair the damaged membranes by de novo synthesis of phospholipids. To determine whether PLA2 action also triggers activation of bacterial lipolytic enzymes, the effects of nisin and PLA2 on the degradation of S. aureus lipids were compared. In contrast to nisin treatment, PLA2 treatment does not stimulate endogenous phospholipase activity in S. aureus. These findings show that S. aureus responds to PLA2 attack by continued phospholipid (re)synthesis by both de novo and salvage pathways. The fate of PLA2-treated S. aureus therefore appears to depend on the relative rates of phospholipid degradation and synthesis.

Evolution of leukotriene B4, peptide leukotrienes, and interleukin-8 plasma concentrations in patients at risk of acute respiratory distress syndrome and with acute respiratory distress syndrome: mortality prognostic study

OBJECTIVE

To compare the evolution of plasma concentrations of leukotriene (LT) B4, LTC4, LTD4, and interleukin (IL)-8 in patients with acute respiratory distress syndrome (ARDS) and in patients at risk of ARDS and to assess the value of these mediators in predicting mortality rate from ARDS.

DESIGN

A case-control study comparing ARDS patients and patients at risk of ARDS as well as survivors and nonsurvivors with ARDS.

SETTING

Hospital intensive care unit, laboratory, and department of hematology.

PATIENTS

Twenty-one patients with ARDS and 14 patients at risk of ARDS.

INTERVENTION

Arterial blood samples were collected on days 0, 1, and 5 after admission to the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

LTs were extracted, separated by high-pressure liquid chromatography and quantified by enzyme immunoassay. IL-8 was analyzed by ELISA. Plasma concentrations of LTB4 and LTC4 plus LTD4 were significantly higher in ARDS patients than in patients at risk of ARDS during the first 24 hrs. Concentrations of IL-8 were also higher in ARDS patients than in patients at risk throughout the study, although the differences between the two groups were only significant on day 5. Only the plasma concentration of LTB4 on day 1 was a marker of ARDS (72.2% sensitivity, 84.6% specificity). A logistic regression analysis showed that LTB4 and IL-8, on day 1, were markers of mortality rate in patients with ARDS (70.0% sensitivity, 87.5% specificity).

CONCLUSIONS

LTs are elevated during the early phases of ARDS, whereas IL-8 increases throughout the study. The evaluation of LTB4 and IL-8 may be useful prognostic indices in patients with early phase ARDS after admission to the intensive care unit.

Comparison of systemic cytokine levels in patients with acute respiratory distress syndrome, severe pneumonia, and controls

BACKGROUND

The inflammatory response has been widely investigated in patients with acute respiratory distress syndrome (ARDS) and pneumonia. Studies investigating the diagnostic values of serum cytokine levels have yielded conflicting results and only little information is available for the differential diagnosis between ARDS and pneumonia.

METHODS

Clinical and physiological data, serum concentrations of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, and quantitative cultures of lower respiratory tract specimens were obtained from 46 patients with ARDS and 20 with severe pneumonia within 24 hours of the onset of the disease and from 10 control subjects with no inflammatory lung disease. Cytokine concentrations were compared between groups and determinants in addition to the diagnosis were tested.

RESULTS

Serum TNF-alpha levels were significantly higher in ARDS patients (67 (57) pg/ml) than in patients with severe pneumonia (35 (20) pg/ml; p = 0.031) or controls (17 (8) pg/ml; p = 0.007). For IL-1beta and IL-6 the observed differences were not statistically significant between patients with ARDS (IL-1beta: 34 (65) pg/ml; IL-6: 712 (1058) pg/ml), those with severe pneumonia (IL-1beta: 3 (4) pg/ml, p = 0.071; IL-6: 834 (1165) pg/ml, p = 1.0), and controls (IL-1beta: 6 (11) pg/ml, p = 0.359; IL-6: 94 (110) pg/ml, p = 0.262). TNF-alpha (standardised coefficient beta = 0.410, p<0.001) and IL-1beta (standardised coefficient beta = 0.311, p = 0.006) were most strongly associated with the degree of lung injury, even when the diagnostic group was included in the statistical model.

CONCLUSIONS

Serum TNF-alpha levels were higher in patients with ARDS than in those with severe pneumonia or in control subjects. Multivariate results suggest that the levels of systemic TNF-alpha and IL-1beta reflect the severity of the lung injury rather than the diagnosis.

Imbalances between tumor necrosis factor-alpha and its soluble receptor forms, and interleukin-1beta and interleukin-1 receptor antagonist in BAL fluid of cavitary pulmonary tuberculosis

OBJECTIVES

We investigated the possibility that the large pulmonary cavity in tuberculosis (TB) lesions might result from imbalances between tumor necrosis factor-alpha (TNF-alpha) and soluble TNF-alpha receptor forms (sTNF-RI and sTNF-RII), and interleukin-beta (IL-1beta) and IL-1 receptor antagonist (IL-1RA) in sites of local inflammation.

PATIENTS AND METHODS

BAL was performed in 32 patients with active pulmonary TB, and the recovered BAL fluid (BALF) was examined for concentrations of TNF-alpha and its soluble receptor forms, IL-1beta, and IL-1RA. Patients were classified into two groups: group 1, patients with a large cavity (> or = 4 cm) on chest radiographs (n = 15); and group 2, patients with a small cavity (< 4 cm; n = 3) or no cavity (n = 14) on chest radiographs.

RESULTS

The concentrations of TNF-alpha, IL-1beta, and IL-1RA in BALF were significantly higher in group 1 patients than in group 2 patients before standardization. The difference was also statistically significant for TNF-alpha and IL-1beta after standardization with urea. Furthermore, group 1 patients had significantly higher ratios of TNF-alpha to sTNF-RI and sTNF-RII and IL-1beta to IL-1RA compared with group 2 patients.

CONCLUSIONS

These findings suggest that the relative abundance of TNF-alpha and IL-1beta associated with imbalances of secretion of soluble TNF-alpha receptor forms and IL-1RA may have caused tissue necrosis leading to cavity formation in patients with active pulmonary TB.

Plasma cytokines: what we are measuring

Immunoassays, in particular enzyme-linked immunosorbent assays, have become increasingly important tools for the measurement of plasma cytokines. However, many technical factors contribute to the complexity of their quantitation. The study of plasma cytokine levels is also of limited value, and complementary methods are now available to investigate and understand more precisely the involvement of cytokines in pathological processes.