Primed stimulation of isolated perfused rabbit lung by endotoxin and platelet activating factor induces enhanced production of thromboxane and lung injury

Bradykinin release following trauma and hemorrhagic shock causes pulmonary alveolar leak in a rodent model

BACKGROUND

Hemorrhage accounts for 40% of the preventable death following severe injury. Activation of systemic coagulation produces bradykinin (BK), which may cause leak from the plasma to the extravascular space and to the tissues, which is part of the complex pathophysiology of trauma-induced end-organ injury. We hypothesize that BK, released during activation of coagulation in severe injury, induces pulmonary alveolar leak.

METHODS

Isolated neutrophils (PMNs) were pretreated with a specific BK receptor B2 antagonist HOE-140/icatibant and BK priming of the PMN oxidase was completed. Rats underwent tissue injury/hemorrhagic shock (TI/HS), TI/icatibant/HS, and controls (no injury). Evans blue dye was instilled, and the percentage leak from the plasma to the lung was calculated from the bronchoalveolar lavage fluid (BALF). CINC-1 and total protein were measured in the BALF, and myeloperoxidase was quantified in lung tissue.

RESULTS

The BK receptor B2 antagonist HOE140/icatibant inhibited (85.0 ± 5.3%) BK priming of the PMN oxidase ( p < 0.05). The TI/HS model caused activation of coagulation by increasing plasma thrombin-antithrombin complexes ( p < 0.05). Versus controls, the TI/HS rats had significant pulmonary alveolar leak: 1.46 ± 0.21% versus 0.36 ± 0.10% ( p = 0.001) and increased total protein and CINC-1 in the BALF ( p < 0.05). Icatibant given after the TI significantly inhibited lung leak and the increase in CINC-1 in the BALF from TI/icatibant/HS rats versus TI/HS ( p < 0.002 and p < 0.05) but not the total protein. There was no PMN sequestration in the lungs. Conclusions: This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

CONCLUSION

This mixed injury model caused systemic activation of hemostasis and pulmonary alveolar leak likely due to BK release.

LEVEL OF EVIDENCE

Original Article, Basic Science.

Succinate Activation of SUCNR1 Predisposes Severely Injured Patients to Neutrophil-mediated ARDS

OBJECTIVES

Identify the metabolites that are increased in the plasma of severely injured patients that developed ARDS versus severely injured patients that did not, and assay if these increased metabolites prime pulmonary sequestration of neutrophils (PMNs) and induce pulmonary sequestration in an animal model of ARDS. We hypothesize that metabolic derangement due to advanced shock in critically injured patients leads to the PMNs, which serves as the first event in the ARDS. Summary of Background Data: Intracellular metabolites accumulate in the plasma of severely injured patients.

METHODS

Untargeted metabolomics profiling of 67 critically injured patients was completed to establish a metabolic signature associated with ARDS development. Metabolites that significantly increased were assayed for PMN priming activity in vitro. The metabolites that primed PMNs were tested in a 2-event animal model of ARDS to identify a molecular link between circulating metabolites and clinical risk for ARDS.

RESULTS

After controlling for confounders, 4 metabolites significantly increased: creatine, dehydroascorbate, fumarate, and succinate in trauma patients who developed ARDS ( P < 0.05). Succinate alone primed the PMN oxidase in vitro at physiologically relevant levels. Intravenous succinate-induced PMN sequestration in the lung, a first event, and followed by intravenous lipopolysaccharide, a second event, resulted in ARDS in vivo requiring PMNs. SUCNR1 inhibition abrogated PMN priming, PMN sequestration, and ARDS. Conclusion: Significant increases in plasma succinate post-injury may serve as the first event in ARDS. Targeted inhibition of the SUCNR1 may decrease ARDS development from other disease states to prevent ARDS globally.

Supernatants and lipids from stored red blood cells activate pulmonary microvascular endothelium through the BLT2 receptor and protein kinase C activation

BACKGROUND

Although transfusion is a lifesaving intervention, it may be associated with significant morbidity in injured patients. We hypothesize that stored red blood cells (RBCs) induce proinflammatory activation of human pulmonary microvascular endothelial cells (HMVECs) resulting in neutrophil (PMN) adhesion and predisposition to acute lung injury (ALI).

STUDY DESIGN AND METHODS

Ten units of RBCs were collected; 50% (by weight) were leukoreduced (LR-RBCs) and the remainder was unmodified and stored in additive solution-5 (AS-5). An additional 10 units of RBCs were collected, leukoreduced, and stored in AS-3. HMVECs were incubated with [10%-40%]_FINAL of the supernatants on Day (D)1 to D42 of storage, lipid extracts, and purified lipids. Endothelial surface expression of intercellular adhesion molecule-1 (ICAM-1), interleukin (IL)-8 release, and PMN adhesion to HMVECs were measured. HMVEC signaling via the BLT2 receptor was evaluated. Supernatants and lipids were also employed as the first event in a two-event model of ALI.

RESULTS

The supernatants [10%-40%]_FINAL from D21 LR-RBCs and D42 RBCs and LR-RBCs and the lipids from D42 stored in AS-5 induced increased ICAM-1 surface expression on endothelium, IL-8 release, and PMN adhesion. In addition, the supernatants [20%-40%]_FINAL from D21 and D42 RBCs in AS-5 also increased endothelial surface expression of ICAM-1. D42 supernatants and lipids also caused coprecipitation of β-arrestin-1 with BLT2, protein kinase C (PKC)β_I , and PKCδ and served as the first event in a two-event rodent model of ALI.

CONCLUSION

Lipids that accumulate during RBC storage activate endothelium and predispose to ALI, which may explain some of the adverse events associated with the transfusion of critically injured patients.

α-Enolase Causes Proinflammatory Activation of Pulmonary Microvascular Endothelial Cells and Primes Neutrophils Through Plasmin Activation of Protease-Activated Receptor 2

Proinflammatory activation of vascular endothelium leading to increased surface expression of adhesion molecules and neutrophil (PMN) sequestration and subsequent activation is paramount in the development of acute lung injury and organ injury in injured patients. We hypothesize that α-enolase, which accumulates in injured patients, primes PMNs and causes proinflammatory activation of endothelial cells leading to PMN-mediated cytotoxicity.

METHODS

Proteomic analyses of field plasma samples from injured versus healthy patients were used for protein identification. Human pulmonary microvascular endothelial cells (HMVECs) were incubated with α-enolase or thrombin, and intercellular adhesion molecule-1 surface expression was measured by flow cytometry. A two-event in vitro model of PMN cytotoxicity HMVECs activated with α-enolase, thrombin, or buffer was used as targets for lysophosphatidylcholine-primed or buffer-treated PMNs. The PMN priming activity of α-enolase was completed, and lysates from both PMNs and HMVECs were immunoblotted for protease-activated receptor 1 (PAR-1) and PAR-2 and coprecipitation of α-enolase with PAR-2 and plasminogen/plasmin.

RESULTS

α-Enolase increased 10.8-fold in injured patients (P < 0.05). Thrombin and α-enolase significantly increased intercellular adhesion molecule-1 surface expression on HMVECs, which was inhibited by antiproteases, induced PMN adherence, and served as the first event in the two-event model of PMN cytotoxicity. α-Enolase coprecipitated with PAR-2 and plasminogen/plasmin on HMVECs and PMNs and induced PMN priming, which was inhibited by tranexamic acid, and enzymatic activity was not required.

CONCLUSIONS

α-Enolase increases after injury and may activate pulmonary endothelial cells and prime PMNs through plasmin activity and PAR-2 activation. Such proinflammatory endothelial activation may predispose to PMN-mediated organ injury.

Systemic capillary leak syndrome under general anesthesia: a case report

Systemic capillary leak syndrome (SCLS) is very rare and lethal disease and only 150 cases have been reported after the first publication of its report in 1960 by Clarkson. SCLS is characterized by hemoconcentation and hypoalbuminemia caused by reversible plasma extravasation. Its mechanism is unknown, but transient dysfunction of the endothelium is the most suspected cause and trigger of this event may cause immunologic disarrangement. After recovery of endothelial function, fluid injected during the shock period is redistributed and can cause severe pulmonary edema. SCLS should be considered in patients with acute and severe hypotension with hemoconcentration and hypoalbuminemia without obvious cardiac dysfunction. Especially we should take into account the possibility of SCLS if fluid replacement does not work or the shock state is aggravated despite aggressive fluid resuscitation and vasopressor administration. SCLS itself is a very rare disease; furthermore, SCLS that develops during well-controlled surgery is even more rare. So we report this case with review of the literature.

Novel swine model of transfusion-related acute lung injury

BACKGROUND

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of blood transfusion. Antibodies against human leukocyte antigens in donors' plasma are the major causes of TRALI. Several animal models of TRALI have been developed, and the mechanism underlying TRALI development has been extensively investigated using rodent models. Although sheep models of nonimmune TRALI have been developed, large-animal models of antibody-mediated TRALI are not yet available.

STUDY DESIGN AND METHODS

To develop a swine model of TRALI, male Clawn strain miniature pigs were used. A monoclonal antibody (MoAb) against swine leukocyte antigens (SLAs) Class I (4G8, 0.3 or 1.0 mg/kg body weight [BW]) and a control antibody (1.0 mg/kg BW) were injected into the peripheral vein after priming with or without 1 μg/kg BW lipopolysaccharide (LPS; n = 3 each). Lung injury was assessed using PaO2 /FiO2 (P/F) ratio and by chest X-ray imaging. Histopathologic analysis was also conducted.

RESULTS

Lung injury could be induced by injecting 4G8 at an amount of 1.0 mg/kg BW, after LPS. The P/F ratio 90 minutes after the administration of 4G8 significantly decreased (p < 0.05). Bilateral infiltration was shown in chest X-ray imaging. Lung injury was confirmed by histopathologic analysis.

CONCLUSION

Lung injury in pigs was successfully induced by anti-SLA MoAb. Priming with LPS is a prerequisite for inducing lung injury and the amount of the antibody is a critical condition.

Transfusion-related acute lung injury: advances in understanding the role of proinflammatory mediators in its genesis

Transfusion-related acute lung injury (TRALI) is the most common cause of serious morbidity and mortality due to hemotherapy. The pathogenesis is the result of two events: the first related to the recipient's clinical condition, predisposing to acute lung injury (ALI) through neutrophil or polymorphonuclear leukocyte sequestration, and the second being the infusion of antibodies or mediators that activate these adherent polymorphonuclear neutrophils, resulting in endothelial damage, capillary leak and ALI. TRALI is most prevalent in the critically ill, although many of these cases are termed ALI. Although mitigation strategies, such as the use of male-only plasma, have decreased the number of TRALI cases and deaths, TRALI still occurs. This review will detail the pathophysiology of TRALI, provide insight into newer areas of research and critically assess current practices to mitigate TRALI and improve transfusion safety.

Disparate roles of marrow- and parenchymal cell-derived TLR4 signaling in murine LPS-induced systemic inflammation

Systemic inflammatory response syndrome (SIRS) occurs in a range of infectious and non-infectious disease processes. Toll-like receptors (TLRs) initiate such responses. We have shown that parenchymal cell TLR4 activation drives LPS-induced systemic inflammation; SIRS does not develop in mice lacking TLR4 expression on parenchymal cells. The parenchymal cell types whose TLR4 activation directs this process have not been identified. Employing a bone marrow transplant model to compartmentalize TLR4 signaling, we characterized blood neutrophil and cytokine responses, NF-κB1 activation, and Tnf-α, Il6, and Ccl2 induction in several organs (spleen, aorta, liver, lung) near the time of LPS-induced symptom onset. Aorta, liver, and lung gene responses corresponded with both LPS-induced symptom onset patterns and plasma cytokine/chemokine levels. Parenchymal cells in aorta, liver, and lung bearing TLR4 responded to LPS with chemokine generation and were associated with increased plasma chemokine levels. We propose that parenchymal cells direct SIRS in response to LPS.

Towards prevention of acute lung injury: frequency and outcomes of emergency department patients at-risk - a multicenter cohort study

BACKGROUND

Few emergency department (ED) evaluations on acute lung injury (ALI) have been carried out; hence, we sought to describe a cohort of hospitalized ED patients at risk for ALI development.

METHODS

Patients presenting to the ED with at least one predisposing condition to ALI were included in this study, a subgroup analysis of a multicenter observational cohort study (USCIITG-LIPS 1). Patients who met ALI criteria within 6 h of initial ED assessment, received end-of-life care, or were readmitted during the study period were excluded. Primary outcome was frequency of ALI development; secondary outcomes were ICU and hospital mortality.

RESULTS

Twenty-two hospitals enrolled 4,361 patients who were followed from the ED to hospital discharge. ALI developed in 303 (7.0 %) patients at a median onset of 2 days (IQR 2-5). Of the predisposing conditions, frequency of ALI development was highest in patients who had aortic surgery (43 %) and lowest in patients with pancreatitis (2.8 %). Compared to patients who did not develop ALI, those who did had higher ICU (24 % vs. 3.0 %, p < 0.001) and hospital (28 % vs. 4.6 %, p < 0.001) mortality, and longer hospital length of stay (16 vs. 5 days, p < 0.001). Among the 22 study sites, frequency of ALI development varied from less than 1 % to more than 12 % after adjustment for APACHE II.

CONCLUSIONS

Seven percent of hospitalized ED patients with at least one predisposing condition developed ALI. The frequency of ALI development varied significantly according to predisposing conditions and across institutions. Further research is warranted to determine the factors contributing to ALI development.

A two-event in vitro model of acute chest syndrome: the role of secretory phospholipase A2 and neutrophils

BACKGROUND

Acute chest syndrome (ACS) in sickle cell disease is associated with elevation of secretory phospholipase A(2) (sPLA(2) ). We hypothesize that sPLA(2) cleaves membrane lipids from sickled red blood cells (RBCs) causing PMN-mediated endothelial cell injury (ECI) as the second event in a two-event model.

METHODS

Whole blood was collected from children when in steady state or daily during admissions for vaso-occlusive pain (VOC) or ACS. The plasma and RBCs were separated, sPLA(2) levels were measured, and the RBCs were incubated with sPLA(2) . Plasma and lipids, extracted from the plasma or the supernatant of sPLA(2) -treated RBCs, were assayed for PMN priming activity and used as the second event in a model of PMN-mediated ECI. Phosphatidylserine (PS) surface expression on RBCs was quantified by flow cytometry.

RESULTS

Increased sPLA(2) -IIa levels were associated with ACS. SPLA(2) -liberated lipids from VOC and the plasma, plasma lipids and sPLA(2) -liberated lipids from ACS primed PMNs and caused PMN-mediated ECI (P < 0.01). RBCs from VOC had increased in PS surface expression versus steady state.

CONCLUSIONS

ACS plasma and lipids and sPLA(2) -released lipids from RBCs during VOC or ACS induce PMN-mediated ECI. VOC elicited increases in PS surface expression providing a membrane substrate for sPLA(2) lysis of sickle RBCs.

Age of blood and recipient factors determine the severity of transfusion-related acute lung injury (TRALI)

Introduction

Critical care patients frequently receive blood transfusions. Some reports show an association between aged or stored blood and increased morbidity and mortality, including the development of transfusion-related acute lung injury (TRALI). However, the existence of conflicting data endorses the need for research to either reject this association, or to confirm it and elucidate the underlying mechanisms.

Methods

Twenty-eight sheep were randomised into two groups, receiving saline or lipopolysaccharide (LPS). Sheep were further randomised to also receive transfusion of pooled and heat-inactivated supernatant from fresh (Day 1) or stored (Day 42) non-leucoreduced human packed red blood cells (PRBC) or an infusion of saline. TRALI was defined by hypoxaemia during or within two hours of transfusion and histological evidence of pulmonary oedema. Regression modelling compared physiology between groups, and to a previous study, using stored platelet concentrates (PLT). Samples of the transfused blood products also underwent cytokine array and biochemical analyses, and their neutrophil priming ability was measured in vitro.

Results

TRALI did not develop in sheep that first received saline-infusion. In contrast, 80% of sheep that first received LPS-infusion developed TRALI following transfusion with "stored PRBC." The decreased mean arterial pressure and cardiac output as well as increased central venous pressure and body temperature were more severe for TRALI induced by "stored PRBC" than by "stored PLT." Storage-related accumulation of several factors was demonstrated in both "stored PRBC" and "stored PLT", and was associated with increased in vitro neutrophil priming. Concentrations of several factors were higher in the "stored PRBC" than in the "stored PLT," however, there was no difference to neutrophil priming in vitro.

Conclusions

In this in vivo ovine model, both recipient and blood product factors contributed to the development of TRALI. Sick (LPS infused) sheep rather than healthy (saline infused) sheep predominantly developed TRALI when transfused with supernatant from stored but not fresh PRBC. "Stored PRBC" induced a more severe injury than "stored PLT" and had a different storage lesion profile, suggesting that these outcomes may be associated with storage lesion factors unique to each blood product type. Therefore, the transfusion of fresh rather than stored PRBC may minimise the risk of TRALI.

Stimulation of Ly-6G on neutrophils in LPS-primed mice induces platelet-activating factor (PAF)-mediated anaphylaxis-like shock

Previously, two anti-Ly-6G mAb-RB6-8C5 and 1A8-have been used to deplete neutrophils in mice and to clarify their involvement in immune responses. During the course of experiments on neutrophil depletion, we noticed that i.v. injection of RB6-8C5 or 1A8 induced anaphylaxis-like shock in mice pretreated i.v. with LPS. Signs of shock, such as hypothermia, appeared within a few minutes, and the mice died of shock within 20 min of the antibody injection. In vivo experiments, including depletion of various cell types, indicated that neutrophils and macrophages (but not platelets, basophils, or mast cells) are involved in the shock. Experiments using various drugs and gene-targeted mice demonstrated that PAF is the central mediator of the shock. Optimal LPS priming required at least 1 h, and the priming was associated with neutrophil accumulation within pulmonary and hepatic blood vessels. Consistently, following 1A8 injection into LPS-pretreated mice, the mRNA for LysoPAFAT (a PAF biosynthetic enzyme) was markedly up-regulated in neutrophils accumulated in the lung but not in macrophages. These results suggest that (1) stimulation of Ly-6G on LPS-primed neutrophils induces PAF-mediated anaphylaxis-like shock in mice, (2) neutrophils are primed by LPS during and/or after their accumulation in lung and liver to rapidly induce LysoPAFAT, and (3) macrophages may play a pivotal role in the priming phase and/or in the challenge phase by unknown mechanisms. These findings may be related to adult respiratory distress syndrome, although the natural ligand for Ly-6G remains to be identified.

A novel in vivo ovine model of transfusion-related acute lung injury (TRALI)

BACKGROUND AND OBJECTIVES

Even with the introduction of specific risk-reduction strategies, transfusion-related acute lung injury (TRALI) continues to be a leading cause of transfusion-related morbidity and mortality. Existing small animal models have not yet investigated TRALI resulting from the infusion of heat-treated supernatant from whole blood platelet concentrates. In this study, our objective was the development of a novel in vivo two-event model of TRALI in sheep.

MATERIALS AND METHODS

Lipopolysaccharide (LPS; 15 μg/kg) as a first event, modelled clinical infection. Transfusion (estimated at 10% of total blood volume) of heat-treated pooled supernatant from date-of-expire human whole blood platelet concentrates (d5-PLT-S/N) was used as a second event. TRALI was defined by both hypoxaemia that developed either during the transfusion or within two hours of its completion and post-mortem histological evidence of pulmonary oedema.

RESULTS

LPS infusion did not cause lung injury itself, but did result in decreased circulating levels of lymphocytes and neutrophils with evidence of the latter becoming sequestered in the lungs. Sheep that received LPS (first event) followed by d5-PLT-S/N (second event) displayed decreased pulmonary compliance, decreased end tidal CO(2) and increased arterial partial pressure of CO(2) relative to control sheep, and 80% of these sheep developed TRALI.

CONCLUSIONS

This novel ovine two-event TRALI model presents a new tool for the investigation of TRALI pathogenesis. It represents the first description of an in vivo large animal model of TRALI and the first description of TRALI caused by transfusion with heat-treated pooled supernatant from human whole blood platelet concentrates.

Mirasol Pathogen Reduction Technology treatment does not affect acute lung injury in a two-event in vivo model caused by stored blood components

INTRODUCTION

Mirasol Pathogen Reduction Technology (PRT) treatment uses riboflavin and UV light to inactivate pathogens in blood components. Neutrophil [polymorphonuclear cells (PMN)] priming activity accumulates during routine storage of cellular blood components, and this activity has been implicated in transfusion-related acute lung injury (TRALI). We hypothesize that PRT-treatment of blood components affects the priming activity generated during storage of packed RBCs (PRBCs) or platelet concentrates (PCs), which can elicit ALI in vivo.

METHODS

Plasma, PRBCs and PCs were isolated from healthy donor's whole blood or by apheresis. Half of a collected unit was treated with PRT treatment and the remainder was left as an unmodified control. Supernatant was collected during storage of PCs and PRBCs and assayed for PMN priming activity and used as the second event in a two-event in vivo model of TRALI.

RESULTS

PRT treatment did not induce priming activity in plasma or affect the priming activity generated during storage of PCs or PRBCs as compared with the unmodified controls. The supernatants from stored, but not fresh, PCs and PRBCs did cause ALI as the second event in a two-event animal model of TRALI, which was unaffected by PRT treatment. We conclude that the PRT treatment does not induce priming activity in plasma nor does it affect the priming activity generated during storage of PCs or PRBCs or their ability to cause ALI as the second event in a two-event in vivo model of TRALI. Moreover, the amount of priming activity in TRIMA-isolated PCs was significantly less than SPECTRA-isolated PCs.

Transfusion-related acute lung injury (TRALI): current concepts and misconceptions

Transfusion-related acute lung injury (TRALI) is the most common cause of serious morbidity and mortality due to hemotherapy. Although the pathogenesis has been related to the infusion of donor antibodies into the recipient, antibody negative TRALI has been reported. Changes in transfusion practices, especially the use of male-only plasma, have decreased the number of antibody-mediated cases and deaths; however, TRALI still occurs. The neutrophil appears to be the effector cell in TRALI and the pathophysiology is centered on neutrophil-mediated endothelial cell cytotoxicity resulting in capillary leak and ALI. This review will detail the pathophysiology of TRALI including recent pre-clinical data, provide insight into newer areas of research, and critically assess current practices to decrease it prevalence and to make transfusion safer.

Animal models of transfusion-related acute lung injury

Currently, more than 50 years after its apparent early recognition in case reports, and more than 20 years after its name was coined to denote a distinct entity of pulmonary transfusion reactions, transfusion-related acute lung injury (TRALI) has emerged as a serious cause of transfusion-associated morbidity and the subject of an exponentially growing scientific literature. However, review articles, clinical case reports, and case series continue to dominate the published literature on the topic and experimental studies aimed at modeling and elucidating TRALI mechanisms are less frequent. This article reviews the current status of the known experimental models of TRALI, with particular emphasis on efforts to establish in vivo animal models of this important pulmonary transfusion reaction.

Plasma from stored packed red blood cells and MHC class I antibodies causes acute lung injury in a 2-event in vivo rat model

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion death. We hypothesize that TRALI requires 2 events: (1) the clinical condition of the patient and (2) the infusion of antibodies against MHC class I antigens or the plasma from stored blood. A 2-event rat model was developed with saline (NS) or endotoxin (LPS) as the first event and the infusion of plasma from packed red blood cells (PRBCs) or antibodies (OX18 and OX27) against MHC class I antigens as the second event. ALI was determined by Evans blue dye leak from the plasma to the bronchoalveolar lavage fluid (BALF), protein and CINC-1 concentrations in the BALF, and the lung histology. NS-treated rats did not evidence ALI with any second events, and LPS did not cause ALI. LPS-treated animals demonstrated ALI in response to plasma from stored PRBCs, both prestorage leukoreduced and unmodified, and to OX18 and OX27, all in a concentration-dependent fashion. ALI was neutrophil (PMN) dependent, and OX18/OX27 localized to the PMN surface in vivo and primed the oxidase of rat PMNs. We conclude that TRALI is the result of 2 events with the second events consisting of the plasma from stored blood and antibodies that prime PMNs.

Endothelial pathomechanisms in acute lung injury

Acute lung injury (ALI) and its most severe extreme the acute respiratory distress syndrome (ARDS) refer to increased-permeability pulmonary edema caused by a variety of pulmonary or systemic insults. ALI and in particular ARDS, are usually accompanied by refractory hypoxemia and the need for mechanical ventilation. In most cases, an exaggerated inflammatory and pro-thrombotic reaction to an initial stimulus, such as systemic infection, elicits disruption of the alveolo-capillary membrane and vascular fluid leak. The pulmonary endothelium is a major metabolic organ promoting adequate pulmonary and systemic vascular homeostasis, and a main target of circulating cells and humoral mediators under injury; pulmonary endothelium is therefore critically involved in the pathogenesis of ALI. In this review we will discuss mechanisms of pulmonary endothelial dysfunction and edema generation in the lung with special emphasis on the interplay between the endothelium, the immune and hemostatic systems, and highlight how these principles apply in the context of defined disorders and specific insults implicated in ALI pathogenesis.

Acute pulmonary capillary leak syndrome during elective surgery under general anesthesia

A 75-year-old previously healthy man presented for elective resection of rectal cancer under general anesthesia. Six days before the operation, he had a high-grade fever, and elevated leukocyte count and C-reactive protein concentration, but this was resolved by an intravenous antibiotic. His condition was well controlled before the operation. Soon after the operation started, severe hypoxemia emerged, with low arterial pressure. Fiberoptic bronchoscopy demonstrated a massive amount of plasma-like edema fluid; the total amount of suctioned fluid was approximately 800 ml at the end of the surgery. This acute pulmonary edema appeared to be due to increased permeability rather than pulmonary congestion as indicated by chest radiography, pulmonary artery occlusion pressure, echocardiogram, and the protein-rich edema fluid. Elevated concentrations of the proinflammatory cytokines, interleukin (IL)-6 and IL-8, in both plasma and the pulmonary edema fluid, suggested a possible role of systemic and pulmonary inflammation in the development of this acute pulmonary capillary leak. According to the "two-hit" hypothesis, the bacterial infection preceding the operation may have primed the immune cells, and the following surgical stress may have then triggered rapid progression of acute respiratory distress syndrome. We should keep in mind that, especially following sepsis, sudden massive pulmonary capillary leak can occur during elective surgery, even though the patient's condition is well controlled.

Role of platelet-activating factor in pneumolysin-induced acute lung injury

OBJECTIVE

Acute respiratory failure is a major complication of severe pneumococcal pneumonia, characterized by impairment of pulmonary microvascular barrier function and pulmonary hypertension. Both features can be evoked by pneumolysin (PLY), an important virulence factor of Streptococcus pneumoniae. We hypothesized that platelet-activating factor (PAF) and associated downstream signaling pathways play a role in the PLY-induced development of acute lung injury.

DESIGN

Controlled, ex vivo laboratory study.

SUBJECTS

Female Balb/C mice, 8-12 wks old.

INTERVENTIONS

Ventilated and blood-free-perfused lungs of wild-type and PAF receptor-deficient mice were challenged with recombinant PLY.

MEASUREMENTS AND MAIN RESULTS

Intravascular PLY, but not the pneumolysoid Pd-B (PLY with a Trp-Phe substitution at position 433), caused an impressive dose-dependent increase in pulmonary vascular resistance and increased PAF in lung homogenates, as detected by reversed-phase high-performance liquid chromatography coupled to tandem mass spectrometry. The pressor response was reduced in lungs of PAF receptor-deficient mice and after PAF receptor blockade by BN 50730. PLY and exogenous PAF increased thromboxane B2 in lung effluate, and thromboxane receptor inhibition by BM 13505 diminished the pressor response to PLY. Differential inhibition of intracellular signaling steps suggested significant contribution of phosphatidylcholine-specific phospholipase C and protein kinase C and of the Rho/Rho-kinase pathway to PLY-induced pulmonary vasoconstriction. Unrelated to the pulmonary arterial pressor response, microvascular leakage of PLY was diminished in lungs of PAF receptor-deficient mice as well.

CONCLUSIONS

PAF significantly contributed to PLY-induced acute injury in murine lungs. The PAF-mediated pressor response to PLY depends on thromboxane and on the downstream effectors phosphatidylcholine-specific phospholipase C, protein kinase C, and Rho-kinase.

Soluble CD40 ligand accumulates in stored blood components, primes neutrophils through CD40, and is a potential cofactor in the development of transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a form of posttransfusion acute pulmonary insufficiency that has been linked to the infusion of biologic response modifiers (BRMs), including antileukocyte antibodies and lipids. Soluble CD40 ligand (sCD40L) is a platelet-derived proinflammatory mediator that accumulates during platelet storage. We hypothesized that human polymorpho-nuclear leukocytes (PMNs) express CD40, CD40 ligation rapidly primes PMNs, and sCD40L induces PMN-mediated cytotoxicity of human pulmonary microvascular endothelial cells (HMVECs). Levels of sCD40L were measured in blood components and in platelet concentrates (PCs) implicated in TRALI or control PCs that did not elicit a transfusion reaction. All blood components contained higher levels of sCD40L than fresh plasma, with apheresis PCs evidencing the highest concentration of sCD40L followed by PCs from whole blood, whole blood, and packed red blood cells (PRBCs). PCs implicated in TRALI reactions contained significantly higher sCD40L levels than control PCs. PMNs express functional CD40 on the plasma membrane, and recombinant sCD40L (10 ng/mL-1 mug/mL) rapidly (5 minutes) primed the PMN oxidase. Soluble CD40L promoted PMN-mediated cytotoxicity of HMVECs as the second event in a 2-event in vitro model of TRALI. We concluded that sCD40L, which accumulates during blood component storage, has the capacity to activate adherent PMNs, causing endothelial damage and possibly TRALI in predisposed patients.

The two-event model of transfusion-related acute lung injury

The objective of this review is to present the two-event model of transfusion-related acute lung injury (TRALI), a life-threatening complication of transfusions that has been the most common cause of transfusion-related death over the past 2 yrs in the United States. The two-event model of TRALI, which is identical to the pathogenesis of the acute respiratory distress syndrome (ARDS), is reviewed and contrasted to antibody-mediated TRALI. Laboratory studies, both in vitro and in vivo, are discussed as well as human studies of TRALI. Methods to avoid patient exposure to blood components that may cause TRALI are also discussed.

Transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a life-threatening adverse event of transfusion, which has an increasing incidence in the United States and is the leading cause of transfusion-related death. TRALI and acute lung injury (ALI) share a common clinical definition except that TRALI is temporally- and mechanistically-related to transfusion of blood or blood components. A number of different models have been proposed to explain the pathogenesis. The first is an antibody-mediated event whereby transfusion of anti-HLA, class I or class II, or anti-granulocyte antibodies into patients whose leukocytes express the cognate antigens. The antibody:antigen interaction causes complement-mediated pulmonary sequestration and activation of neutrophils (PMNs) resulting in TRALI. The second is a two-event model: the first event is the clinical condition of the patient resulting in pulmonary endothelial activation and PMN sequestration, and the second event is the transfusion of a biologic response modifier (including anti-granulocyte antibodies, lipids, and CD40 ligand) that activates these adherent PMNs resulting in endothelial damage, capillary leak, and TRALI. These hypotheses are discussed with respect to animal models and human studies that provide the experimental and clinical relevance. The definition of TRALI, patient predisposition, treatment, prevention and reporting guidelines are also examined.

Transfusion-related acute lung injury

PURPOSE OF REVIEW

Transfusion-related acute lung injury is an uncommon complication of blood transfusion typically manifested by shortness of breath, fever, and hypotension. Transfusion-related acute lung injury is an important cause of transfusion-related morbidity and mortality.

RECENT FINDINGS

Much about the pathogenesis, treatment, and prevention of transfusion-related acute lung injury is poorly understood or is controversial. There is increasing recognition that transfusion-related acute lung injury is an important clinical syndrome, causing most transfusion-related deaths.

SUMMARY

In this report, what is known about transfusion-related acute lung injury is summarized with particular emphasis on recent studies. Some of the areas in which knowledge and/or consensus are currently lacking are identified.

San-Huang-Xie-Xin-Tang attenuates inflammatory responses in lipopolysaccharide-exposed rat lungs

In this study, the potential anti-inflammatory effect of San-Huang-Xie-Xin-Tang (SHXT) and its main component baicalin on LPS-induced lung injury were investigated and compared to the profile of dexamethasone (DEXA) in a pre-clinical animal model. Post-treatment with SHXT (75 mg/kg), baicalin (1.5 mg/kg) and DEXA (0.5 mg/kg), significantly inhibited LPS-induced hypotension, lung edema and acute survival rates. Western blotting analysis results indicated that all of them significantly inhibited LPS-induced iNOS, TGF-beta, p38MAPK, and ICAM-1 expressions in the lung tissues. Results from ELISA analysis showed that SHXT, baicalin and DEXA all decreased plasma levels of IL-1beta, TNF-alpha, and MCP-1 caused by LPS. Based on these findings, SHXT and baicalin decreased plasma concentrations of IL-1beta, TNF-alpha, MCP-1, and expressions of TGF-beta, ICAM-1, phosphorylated p38 MAPK, and iNOS, which were associated with lung injury and lethality. These evidences indicated that SHXT and baicalin showed strong anti-inflammatory activity, similar to that observed for DEXA, and therefore implicated that herbal SHXT might be therapeutically useful for the treatment of endotoxic lung injury.

Transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a life-threatening adverse effect of transfusion that is occurring at increasing incidence in the United States and that, in the past 2 reporting years, has been the leading cause of transfusion-related death. TRALI and acute lung injury (ALI) share a common clinical definition except that TRALI is temporally and mechanistically related to the transfusion of blood/blood components. In prospective studies, 2 patient groups, 1 requiring cardiac surgery and 1 with hematologic malignancies and undergoing induction chemotherapy, were predisposed. Two different etiologies have been proposed. The first is a single antibody-mediated event involving the transfusion of anti-HLA class I and class II or antigranulocyte antibodies into patients whose leukocytes express the cognate antigens. The second is a 2-event model: the first event is the clinical condition of the patient resulting in pulmonary endothelial activation and neutrophil sequestration, and the second event is the transfusion of a biologic response modifier (including lipids or antibodies) that activates these adherent polymorphonuclear leukocytes (PMNs), resulting in endothelial damage, capillary leak, and TRALI. These hypotheses are discussed, as are the animal models and human studies that provide the experimental and clinical relevance. Prevention, treatment, and a proposed definition of TRALI, especially in the context of ALI, are also examined.

Pulmonary injury from transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) can be a life-threatening complication of transfusion. In its severe form, it is clinically indistinguishable from acute respiratory distress syndrome. Symptoms typically begin within 4 hours of transfusion. TRALI has been reported after transfusion of all plasma-containing blood components. TRALI is associated with antibodies to white blood cells and biologically active lipids in trans-fused blood components.

Transfusion-related acute lung injury: a review

Transfusion-related acute lung injury (TRALI) is an underreported complication of transfusion therapy, and it is the third most common cause of transfusion-associated death. TRALI is defined as noncardiogenic pulmonary edema temporally related to transfusion therapy. The diagnosis of TRALI relies on excluding other diagnoses such as sepsis, volume overload, and cardiogenic pulmonary edema. Supportive diagnostic evidence includes identifying neutrophil or human leukocyte antigen (HLA) antibodies in the donor or recipient plasma. All plasma-containing blood products have been implicated in TRALI, with the majority of cases linked to whole blood, packed RBCs, platelets, and fresh-frozen plasma. The pathogenesis of TRALI may be explained by a "two-hit" hypothesis, with the first "hit" being a predisposing inflammatory condition commonly present in the operating room or ICU. The second hit may involve the passive transfer of neutrophil or HLA antibodies from the donor or the transfusion of biologically active lipids from older, cellular blood products. Treatment is supportive, with a prognosis substantially better than most causes of clinical acute lung injury.

Transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is an uncommon complication of allogeneic blood transfusion manifested typically by shortness of breath, fever, and hypotension. It has been estimated to occur in 0.04% to 0.16% per patient transfused. TRALI has been identified as an important cause of transfusion-related morbidity and mortality. Despite the increasing recognition that TRALI represents an important clinical syndrome, much about the pathogenesis, treatment, and prevention of TRALI is poorly understood or is controversial. In this report, what is known about TRALI is summarized and some of the areas in which knowledge and/or consensus are currently lacking are identified.

Plasma and lipids from stored platelets cause acute lung injury in an animal model

BACKGROUND

Transfusion of PLT concentrates may cause TRALI, a life-threatening reaction that has been linked to the infusion of anti-WBC immunoglobulins or older, stored PLTs that contain bioactive lipids. We hypothesize that lipids generated during storage of PLTs cause TRALI in a two-event animal model.

STUDY DESIGN AND METHODS

Plasma from both whole-blood PLTs (WB-PLTs) and apheresis PLTs (A-PLTs) was isolated on Day 0 (D.0) and Day 5 (D.5) of storage and heat-treated before use. Rats were pretreated with saline or 2 mg per kg endotoxin (LPS), anesthetized, and the lungs were ventilated, isolated, and perfused with saline or 5-percent PLT plasma. Pulmonary artery pressure, pulmonary edema, and leukotriene B4 levels (perfusate) were measured.

RESULTS

Plasma from D.5, but not D.0, of the identical WB-PLT and A-PLT units caused injury in lungs from LPS-pretreated rats (LPS/D.5) evidenced by increases in pulmonary edema and leukotriene B4 (p < 0.05). Lipid extracts and purified lipids from D.5 PLT plasma also elicited injury in lungs from LPS-pretreated rats (p < 0.05). Saline/D.5 plasma or lipids or LPS/D.0 did not cause pulmonary edema. Prestorage WBC reduction was ineffective in inhibiting TRALI.

CONCLUSION

PLT-induced TRALI may be the result of two events: 1) the clinical condition of the patient and 2) the infusion of lipids in stored PLTs.

Transfusion-related acute lung injury: epidemiology and a prospective analysis of etiologic factors

Transfusion-related acute lung injury (TRALI) is a life-threatening complication of hemotherapy. We report a series of 90 TRALI reactions in 81 patients secondary to transfusion with whole blood platelets (72 reactions), apheresis platelets (2), packed red cells (15), and plasma (1). The overall prevalence was 1 in 1120 cellular components. To examine the epidemiology of TRALI, we completed a nested case-control study of the first 46 patients with TRALI compared with 225 controls who had received transfusions. We then completed a prospective analysis of possible biologic response modifiers responsible for 51 of the TRALI cases, including human leukocyte antigen (HLA) class I, class II, and granulocyte antibodies in donors and neutrophil (PMN) priming activity in the plasma of the implicated units and recipients. Two groups were at risk: patients with hematologic malignancies (P <.0004) and patients with cardiac disease (P <.0006). TRALI was associated with older platelets (P =.014). In the prospective study, antileukocyte antibodies were found in only 3.6% of cases. The implicated blood components had greater PMN priming activity than controls (P <.05), and compared with pretransfusion samples, TRALI patients' plasma demonstrated increases in both interleukin 6 (IL-6) and lipid (neutral lipids and lysophosphatidylcholines) priming activity (P <.05). We conclude that TRALI may be more frequent than previously recognized and that patient susceptibility, product age, and increased levels of bioactive lipids in components may predispose patients to TRALI. TRALI, like the acute respiratory distress syndrome, may be a 2-event phenomenon with both recipient predisposition and factors in the stored units playing major roles.

A two-insult in vitro model of PMN-mediated pulmonary endothelial damage: requirements for adherence and chemokine release

Lysophosphatidylcholines (lyso-PCs), generated during blood storage, are etiologic in a two-insult, sepsis-based model of transfusion-related acute lung injury (TRALI). Individually, endotoxin (LPS) and lyso-PCs prime but do not activate neutrophils (PMNs). We hypothesized that priming of PMNs alters their reactivity such that a second priming agent causes PMN activation and endothelial cell damage. PMNs were primed or not with LPS and then treated with lyso-PCs, and oxidase activation and elastase release were measured. For coculture experiments, activation of human pulmonary microvascular endothelial cells (HMVECs) was assessed by ICAM-1 expression and chemokine release. HMVECs were stimulated or not with LPS, PMNs were added, cells were incubated with lyso-PCs, and the number of viable HMVECs was counted. Lyso-PCs activated LPS-primed PMNs. HMVEC activation resulted in increased ICAM-1 and release of ENA-78, GRO alpha, and IL-8. PMN-mediated HMVEC damage was dependent on LPS activation of HMVECs, chemokine release, PMN adhesion, and lyso-PC activation of the oxidase. In conclusion, sequential exposure of PMNs to priming agents activates the microbicidal arsenal, and PMN-mediated HMVEC damage was the result of two insults: HMVEC activation and PMN oxidase assembly.

Transcriptional control of the human thromboxane synthase gene in vivo and in vitro

Thromboxane A(2), a potent mediator of vasoconstriction and platelet aggregation, is synthesized from prostaglandin H(2) by thromboxane synthase (TXAS). We report here on promoter analyses of human TXAS using in vitro transcription and in vivo transfection methods. The 39-bp core promoter, containing both TATA and initiator elements, accurately initiates transcription in an orientation-dependent manner in a cell-free transcription system. Mutation of either TATA or initiator abolished transcriptional activity, but the upstream sequence had no effect on TXAS promoter activities in vitro, suggesting that the core promoter is sufficient for transcriptional activity from a naked DNA template. In contrast, mutation of both elements drastically decreased the promoter activity in vivo. Furthermore, TXAS proximal promoter containing the nucleotides -90 to -56 relative to the transcriptional start site was necessary for promoter transactivation in vivo. Transcriptional activities from 5'-deletion mutants indicated that the effects of the nucleotides -90/-56 were more pronounced in stably transfected cells (a 150-fold difference) than in the transiently transfected cells (an 8-fold difference), reflecting the effects of TXAS transcriptional activation from replicating and nonreplicating DNA templates. Partial micrococcal nuclease digestion indicated that the sequence -90/-56, where the NF-E2 site is located, is associated with alterations of nucleosomal structure at the regions of promoter and reporter gene but not the region further downstream. Mutagenesis and forced expression studies demonstrated a critical role of p45 NF-E2 in controlling TXAS expression under native chromatin conditions. Band shifting and chromatin immunoprecipitation assays indicated that p45 NF-E2 was bound to the TXAS promoter in vitro and in vivo. Indirect end labeling and ligation-mediated PCR analyses further demonstrated that the occupation of TXAS promoter NF-E2 site was associated with disruption of nucleosomal structure. Collectively, these results indicate that binding of NF-E2 is critical both for alteration of the nucleosomal structure and for activation of the TXAS promoter, whereas the TATA and initiator elements are essential for transcription.

Effects of a dual inhibitor of tumor necrosis factor-alpha and interleukin-1 on lipopolysaccharide-induced lung injury in rats: involvement of the p38 mitogen-activated protein kinase pathway

OBJECTIVE

Sepsis is a major cause of adult respiratory distress syndrome. In this study, we evaluated the effect of FR167653, which is a potent suppressant of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 production, on lipopolysaccharide (LPS)-induced lung injury and lethality in rats, and we examined the involvement of p38 mitogen-activated protein (MAP) kinase in the action of FR167653.

DESIGN

Prospective, randomized study.

SETTING

Animal research facility in a university.

SUBJECTS

Male Sprague-Dawley rats weighing 200-270 g.

INTERVENTIONS

All the animals were assigned to one of the following four groups: control group, FR-only group, LPS-only group, and LPS/FR group. Animals in the LPS-only and LPS/FR groups received 6 mg/kg of LPS intravenously. The animals in the FR-only and LPS/FR groups also received an infusion of FR167653 at 0.2 mg x kg(-1) x hr(-1), commencing 30 mins before the LPS (or vehicle) injection and continuing for 5.5 hrs.

MEASUREMENTS AND MAIN RESULTS

LPS significantly induced the accumulation of pulmonary neutrophils and lung edema, both of which were significantly attenuated by treatment with FR167653. FR167653 also significantly decreased the LPS-induced lethality. Histologically, tissue damage was milder in the LPS/FR group than in the LPS-only group. Serum concentrations of TNF-alpha and IL-1beta and plasma concentrations of thromboxane B2 were all suppressed in the LPS/FR group compared with the LPS-only group. Western blot analysis revealed that FR167653 inhibited the phosphorylation of p38 MAP kinase in lung tissues.

CONCLUSIONS

FR167653 administration decreased serum TNF-alpha and IL-1beta concentrations, which was associated with decreased lung injury and lethality. The mechanism responsible for the decreased TNF-alpha and IL-1 may be related to the inhibitory effect of FR167653 on p38 MAP kinase activation.

Effect of dopamine on platelet activating factor induced-pulmonary edema in isolated and perfused rabbit lungs

The effect of dopamine over pulmonary edema induced by PAF was studied. Thirty preparations of rabbit lungs were used: six control preparations (CP), six PAF preparations (PP) in which we injected a dose of 1 microg/kg of rabbit weight and eighteen dopamine preparations (DAP) divided in three groups of six pretreated with a dose of 1-5 (dopaminergic range), 10-20 (Beta range) and 20-30 ug/kg/min (Alpha range) of dopamine, respectively for 30 min, followed by an injection of PAF as in the PP. DAP at Beta and Alpha-adrenergic range decreased pulmonary artery pressure (Pap) as compared to CP, with values of 11.66 (CI 95%: 10.83-12.48), 11.66 (CI 95%: 9.87-13.44) versus 17.12 (CI 95%: 16.12-18.11) cm of water, respectively. DAP in Beta and Alpha-adrenergic range prevented Pap increment as compared to PP, with values of 17.16 (CI 95%: 16.37-17.94), 17.5 (CI 95%: 14.93-20.06) versus 84 cm of water (CI 95%: 71.41-96.58), respectively. Dopamine, at its three ranges inhibited the augmentation of the fluid filtration rate observed in PP with values of 1.01 (CI 95%: 0.77-1.24), 0.03 (CI 95%: 0.01-0.04) and 0.02 g/min (CI 95%: -0.0004-0.03) versus 2.13 g/min (CI 95%: 1.56-2.69), respectively. We concluded that dopamine has a vasodilator effect on Pap and exerts an inhibiting action over PAF effects in pulmonary circulation. Such effects seem to be mainly mediated by Beta-receptors, rather than by dopaminergic receptors.

Mechanisms of endotoxin-induced airway and pulmonary vascular hyperreactivity in mice

Endotoxin is thought to contribute to pulmonary hyperresponsiveness in byssinosis, asthma, and the acute respiratory distress syndrome (ARDS). The aim of this study was to elucidate the mechanism of this phenomenon in the isolated, blood-free perfused mouse lung. Perfusion with lipopolysaccharide (LPS) had no effect on pulmonary resistance or pulmonary artery pressure, but induced airway hyperreactivity (AHR) to methacholine (MCh) and pulmonary vascular hyperreactivity (VHR) to platelet-activating factor (PAF). Blockade of the thromboxane/endoperoxide (TP) receptor with SQ29.548 completely protected against LPS-induced AHR and VHR. Blockade of cyclooxygenase-2 (COX-2) abolished LPS-induced VHR but suppressed LPS-induced AHR only marginally. COX-2 messenger RNA was upregulated in LPS-treated lungs, and inhibition of transcription with actinomycin D or of protein biosynthesis with cycloheximide protected against LPS-induced VHR but not AHR. Pretreatment with the radical scavenger N-acetylcysteine partly protected against LPS-induced AHR. In addition, perfusion of mouse lungs with the isoprostane 8-epiprostaglandin F(2alpha) (8-epi-PGF(2alpha)), which may be formed as a consequence of oxidative stress in the lung, elicited AHR, which was completely blocked by SQ29.548. Enzyme immunoassay did not detect either 8-epi-PGF(2alpha )or thromboxane B(2) in perfusate samples. Our findings show that LPS induces AHR and VHR in mouse lungs via activation of the TP receptor. Although induction of VHR depends on COX-2 activity, AHR is largely mediated by a non-COX-derived TP agonist, which might be a product of radical-induced lipid peroxidation.

Effect of hydrocortisone on platelet activating factor induced lung edema in isolated rabbit lungs

The effect of hydrocortisone on platelet activating factor (PAF)-induced pulmonary edema is studied. Thirty four isolated and perfused rabbit lung preparations were used: eight control preparations, eight PAF preparations with two doses of PAF called low dose (LD = 0.5 microg/kg of rabbit weight) and high dose (HD = 1 microg/kg of rabbit weight). Eighteen preparations divided in three groups of six were pretreated with doses of 20, 200 and 2000 mg of hydrocortisone and later given the same doses of PAF as described above. Hydrocortisone significantly decreased (P < 0.05) the effect of PAF LD over the pulmonary arterial pressure (Ppa) in the 200 and 2000 mg groups (58 and 89% decrease, respectively) and it significantly decreased (P < 0.05) the effect of PAF HD over Ppa in all hydrocortisone pretreated groups (48, 70 and 96% decrease, respectively). Fluid filtration rate (FFR) increases mediated by PAF HD were significantly inhibited (P < 0.05) in the 200 and 2000 mg groups (64 and 96% decrease, respectively). We conclude that hydrocortisone inhibits the effect of PAF over the pulmonary circulation.

PAF-induced synthesis of tetraenoic and pentaenoic leukotrienes in the isolated rabbit lung

In an isolated rabbit lung model, we tested the hypothesis that platelet-activating factor (PAF)-induced leukotriene (LT) synthesis is critically dependent on the free precursor fatty acid supply and the possible substitution of arachidonic acid (AA) by eicosapentaenoic acid (EPA). To augment the intravascular polymorphonuclear neutrophils (PMNs) in the isolated lung, human PMNs were infused into the pulmonary artery. LTs and hydroxyeicosatetra(penta)enoic acids were quantified with HPLC techniques. Application of PAF (5 microM) or AA (10 microM) provoked the generation of limited quantities of 4-series LTs and 5-hydroxyeicosatetraenoic acid (total sum of 5-lipoxygenase products approximately 7 and approximately 27 pmol/ml in lungs both with and without infused PMNs, respectively). Combined administration amplified 5-lipoxygenase product formation, with a predominance of cysteinyl-LT synthesis in lungs both without (total sum approximately 67 pmol/ml) and, much more strikingly, with (total sum approximately 308 pmol/ml) an infusion of neutrophils. EPA (10 microM) elicited exclusive generation of 5-series LTs and 5-hydroxyeicosapentaenoic acid (total sum approximately 82 pmol/ml). Dual stimulation with PAF and EPA provoked amplification of EPA-derived 5-lipoxygenase product formation, again with predominance of cysteinyl-LTs in lungs without (total sum approximately 224 pmol/ml) and, in particular, with (total sum approximately 545 pmol/ml) preceding microvascular PMN entrapment. Combined application of PAF, AA, and EPA resulted in the synthesis of LTs derived from both fatty acids, with a predominance of 5-series products. We conclude that the PAF-evoked 5-lipoxygenase product formation in the neutrophil-harboring lung capillary bed is critically dependent on intravascular precursor fatty acid supply, with EPA representing the preferred substrate compared with AA. PMN-related transcellular eicosanoid synthesis is suggested to underlie the predominant generation of cysteinyl-LTs. The supply of n-3 versus n-6 precursor fatty acid may thus have a major impact on inflammatory mediator generation.

Partial liquid ventilation with perflubron attenuates in vivo oxidative damage to proteins and lipids

OBJECTIVE

To determine the impact of partial liquid ventilation on the degree of pulmonary damage by reactive oxygen species in a model of acute lung injury caused by systemic endotoxemia.

DESIGN

A prospective, controlled, in vivo, animal laboratory study.

SETTING

Animal research facility of a health sciences university.

SUBJECTS

Forty New Zealand White rabbits.

INTERVENTIONS

Mature rabbits were anesthetized and instrumented with a tracheostomy and vascular catheters. Animals were assigned to receive either partial liquid ventilation (n = 16) with perflubron (18 mL/kg via endotracheal tube) or conventional mechanical ventilation (n = 16). Both groups were ventilated using similar strategies, with an Fio2 of 1.0 and tidal volume as required to obtain a normal Paco2. Animals were then given 0.9 mg/kg Escherichia coli endotoxin intravenously over 30 mins. Eight uninjured instrumented and mechanically ventilated animals served as controls. Partial liquid ventilation or conventional ventilation was continued for 4 hrs before the animals were killed. Lung homogenates were analyzed for malondialdehyde (MDA) and 4-hydroxy-2(E)-nonenal (4-HNE) concentrations using a colorimetric assay. To assess protein oxidative damage, carbonyl groups in protein side chains were derivatized with 2,4-dinitrophenylhydrazine followed by Western blotting with a dinitrophenylated-specific primary antibody.

MEASUREMENTS AND MAIN RESULTS

MDA (713.42+/-662 vs. 1601.4+/-1156 nmol/g protein; p = .023) and MDA plus 4-HNE (1480.24+/-788 vs. 2675.2+/-1628 nmol/g protein; p = .038) concentrations were lower in animals treated with partial liquid ventilation compared with conventionally ventilated animals, respectively. Animals treated with partial liquid ventilation exhibited attenuation of dinitrophenylated-derivatized protein bands by Western blotting, indicating a reduction in protein oxidative damage. The presence of perfluorocarbon did not interfere with the MDA assay when assessed by independent analysis in vitro. Perflubron did not serve as a sink for peroxyl radicals produced in the aqueous phase during separate in vitro oxidation experiments.

CONCLUSIONS

Partial liquid ventilation attenuates oxidative damage to lipids and proteins during experimental acute lung injury. This finding is not caused by binding of lipid peroxidation products to perflubron or by the peroxyl radical scavenging properties of perflubron.

Platelet-activating factor (PAF) receptor and genetically engineered PAF receptor mutant mice

Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a biologically active phospholipid mediator. Although PAF was initially recognized for its potential to induce platelet aggregation and secretion, intense investigations have elucidated potent biological actions of PAF in a broad range of cell types and tissues, many of which also produce the molecule. PAF acts by binding to a unique G-protein-coupled seven transmembrane receptor. PAF receptor is linked to intracellular signal transduction pathways, including turnover of phosphatidylinositol, elevation in intracellular calcium concentration, and activation of kinases, resulting in versatile bioactions. On the basis of numerous pharmacological reports, PAF is thought to have many pathophysiological and physiological functions. Recently advanced molecular technics enable us not only to clone PAF receptor cDNAs and genes, but also generate PAF receptor mutant animals, i.e., PAF receptor-overexpressing mouse and PAF receptor-deficient mouse. These mutant mice gave us a novel and specific approach for identifying the pathophysiological and physiological functions of PAF. This review also describes the phenotypes of these mutant mice and discusses them by referring to previously reported pharmacological and genetical data.

Acute Systemic Reaction and Lung Alterations Induced by an Antiplatelet Integrin gpIIb/IIIa Antibody in Mice

Shock is frequently accompanied by thrombocytopenia. To investigate the pathogenic role of platelets in shock, we examined the in vivo effects of monoclonal antibodies (MoAbs) against mouse platelet membrane proteins. Injection of the platelet-specific MoAb MWReg30 to the fibrinogen receptor (gpIIb/IIIa) rendered mice severely hypothermic within minutes. Isotype-matched control antibodies, even if they also recognized platelet surface antigens, did not induce comparable signs. MWReg30 induced early signs of acute lung injury with increased cellularity in the lung interstitium and rapid engorgement of alveolar septal vessels. Despite this in vivo activity, MWReg30 inhibited rather than stimulated platelet aggregation in vitro. MWReg30-binding to platelets led to phosphorylation of gpIIIa, but did not induce morphological signs of platelet activation. The MWReg30-induced reaction was abolished after treatment with MoAbs 2.4G2 to FcγRII/III and was absent in FcγRIII-deficient mice, clearly demonstrating the requirement for FcγRIII on involved leukocytes. Simultaneous administration of tumor necrosis factor exacerbated, whereas a tolerizing regimen of tumor necrosis factor or bacterial lipopolysaccharide completely prevented the reaction. These data suggest that platelet surface-deposited MWReg30-immune complexes lead to an acute Fc-mediated reaction with pulmonary congestion and life-threatening potential that could serve as an in vivo model of acute lung injury.

Acute Systemic Reaction and Lung Alterations Induced by an Antiplatelet Integrin gpIIb/IIIa Antibody in Mice

Shock is frequently accompanied by thrombocytopenia. To investigate the pathogenic role of platelets in shock, we examined the in vivo effects of monoclonal antibodies (MoAbs) against mouse platelet membrane proteins. Injection of the platelet-specific MoAb MWReg30 to the fibrinogen receptor (gpIIb/IIIa) rendered mice severely hypothermic within minutes. Isotype-matched control antibodies, even if they also recognized platelet surface antigens, did not induce comparable signs. MWReg30 induced early signs of acute lung injury with increased cellularity in the lung interstitium and rapid engorgement of alveolar septal vessels. Despite this in vivo activity, MWReg30 inhibited rather than stimulated platelet aggregation in vitro. MWReg30-binding to platelets led to phosphorylation of gpIIIa, but did not induce morphological signs of platelet activation. The MWReg30-induced reaction was abolished after treatment with MoAbs 2.4G2 to FcγRII/III and was absent in FcγRIII-deficient mice, clearly demonstrating the requirement for FcγRIII on involved leukocytes. Simultaneous administration of tumor necrosis factor exacerbated, whereas a tolerizing regimen of tumor necrosis factor or bacterial lipopolysaccharide completely prevented the reaction. These data suggest that platelet surface-deposited MWReg30-immune complexes lead to an acute Fc-mediated reaction with pulmonary congestion and life-threatening potential that could serve as an in vivo model of acute lung injury.