Peripheral blood monocyte-derived chemokine blockade prevents murine transfusion-related acute lung injury (TRALI)

Transfusion-Related Acute Lung Injury: from Mechanistic Insights to Therapeutic Strategies

Transfusion-related acute lung injury (TRALI) is a potentially lethal complication of blood transfusions, characterized by the rapid onset of pulmonary edema and hypoxemia within six hours post-transfusion. As one of the primary causes of transfusion-related mortality, TRALI carries a significant mortality rate of 6-12%. However, effective treatment strategies for TRALI are currently lacking, underscoring the urgent need for a comprehensive and in-depth understanding of its pathogenesis. This comprehensive review provides an updated and detailed analysis of the current landscape of TRALI, including its clinical presentation, pathogenetic hypotheses, animal models, cellular mechanisms, signaling pathways, and potential therapeutic targets. By highlighting the critical roles of these pathways and therapies, this review offers valuable insights to inform the development of preventative and therapeutic strategies and to guide future research efforts aimed at addressing this life-threatening condition.

Key features of the underlying pathophysiology of Transfusion-related acute lung injury

INTRODUCTION

Transfusion-related acute lung injury (TRALI) remains a leading cause of blood transfusion associated mortality, particularly in the intensive care unit. TRALI is underrecognized, underreported and lacks specific biomarkers and clinical therapies.

AREAS COVERED

In this review, the focus will be on the key pathophysiological features of TRALI. This will include the latest insights into the critical importance of complement (in contrast to Fcγ-receptors; FcγRs) as a driver of TRALI, and the role of recipient immune cells such as neutrophils and macrophages, and also the contribution of the pulmonary endothelium.

EXPERT OPINION

Increased efforts are needed to stimulate active reporting of TRALI cases. More research into the immuno-cellular pathophysiology of TRALI is required, including the role of the pulmonary endothelium. Heterogeneity in the underlying clinical condition and the different transfusion triggers should be taken into consideration. This will aid in the search for novel biomarkers and therapeutic modalities. At the moment, the most promising potential therapeutic strategies appear to be administration of interleukin (IL)-10, inhibition of complement activation and blockade of Osteopontin (OPN). Follow-up investigations are, however, highly warranted which should pave the way for multicenter international clinical trials, in order to battle the mortality due to TRALI.

Blocking CCL3-mediated neutrophil recruitment into the brain alleviates immunopathology following severe enterovirus 71 infection

Inflammatory cells infiltration in the cerebrospinal fluid is a hallmark of severe enterovirus 71 (EV71) infection, but which type of immune cells are critical for severe EV71 infection remains unclear. Here, we observe that both neutrophils and macrophages are increased in the brains of patients and mice with severe EV71 infection, and the depletion of neutrophils but not macrophages results in a marked enhancement of survival of EV71-infected mice. Furthermore, CCR1/3 may play an important role in CCL3 facilitating the accumulation of neutrophils in the brains of patients. Inhibition of CCL3 by anti-CCL3 antibodies or selected miRNAs significantly reduces the neutrophils infiltration in brains and the mortality of EV71-infected mice. Collectively, CCL3-mediated neutrophils recruitment into the brain contributes to the severe immunopathology of EV71 infection, which provides a potential diagnostic and therapeutic target for EV71 infection.

IgG hexamers initiate acute lung injury

Antibodies can initiate lung injury in a variety of disease states such as autoimmunity, transfusion reactions, or after organ transplantation, but the key factors determining in vivo pathogenicity of injury-inducing antibodies are unclear. A previously overlooked step in complement activation by IgG antibodies has been elucidated involving interactions between IgG Fc domains that enable assembly of IgG hexamers, which can optimally activate the complement cascade. Here, we tested the in vivo relevance of IgG hexamers in a complement-dependent alloantibody model of acute lung injury. We used three approaches to block alloantibody hexamerization (antibody carbamylation, the K439E Fc mutation, or treatment with domain B from Staphylococcal protein A), all of which reduced acute lung injury. Conversely, Fc mutations promoting spontaneous hexamerization made a harmful alloantibody into a more potent inducer of acute lung injury and rendered an innocuous alloantibody pathogenic. Treatment with a recombinant Fc hexamer 'decoy' therapeutic protected mice from lung injury, including in a model with transgenic human FCGR2A expression that exacerbated pathology. These results indicate a direct in vivo role of IgG hexamerization in initiating acute lung injury and the potential for therapeutics that inhibit or mimic hexamerization to treat antibody-mediated diseases.

Update on transfusion-related acute lung injury: an overview of its pathogenesis and management

Transfusion-related acute lung injury (TRALI) is a severe adverse event and a leading cause of transfusion-associated death. Its poor associated prognosis is due, in large part, to the current dearth of effective therapeutic strategies. Hence, an urgent need exists for effective management strategies for the prevention and treatment of associated lung edema. Recently, various preclinical and clinical studies have advanced the current knowledge regarding TRALI pathogenesis. In fact, the application of this knowledge to patient management has successfully decreased TRALI-associated morbidity. This article reviews the most relevant data and recent progress related to TRALI pathogenesis. Based on the existing two-hit theory, a novel three-step pathogenesis model composed of a priming step, pulmonary reaction, and effector phase is postulated to explain the process of TRALI. TRALI pathogenesis stage-specific management strategies based on clinical studies and preclinical models are summarized with an explication of their models of prevention and experimental drugs. The primary aim of this review is to provide useful insights regarding the underlying pathogenesis of TRALI to inform the development of preventive or therapeutic alternatives.

Mechanism and intervention of murine transfusion-related acute lung injury caused by anti-CD36 antibodies

Anti-CD36 Abs have been suggested to induce transfusion-related acute lung injury (TRALI) upon blood transfusion, particularly in Asian populations. However, little is known about the pathological mechanism of anti-CD36 Ab-mediated TRALI, and potential therapies have not yet been identified. Here, we developed a murine model of anti-CD36 Ab-mediated TRALI to address these questions. Administration of mouse mAb against CD36 (mAb GZ1) or human anti-CD36 IgG, but not GZ1 F(ab')2 fragments, induced severe TRALI in Cd36+/+ male mice. Predepletion of recipient monocytes or complement, but not neutrophils or platelets, prevented the development of murine TRALI. Moreover, plasma C5a levels after TRALI induction by anti-CD36 Abs increased more than 3-fold, implying a critical role of complement C5 activation in the mechanism of Fc-dependent anti-CD36-mediated TRALI. Administration of GZ1 F(ab')2, antioxidant (N-acetyl cysteine, NAC), or C5 blocker (mAb BB5.1) before TRALI induction completely protected mice from anti-CD36-mediated TRALI. Although no significant amelioration in TRALI was observed when mice were injected with GZ1 F(ab')2 after TRALI induction, significant improvement was achieved when mice were treated postinduction with NAC or anti-C5. Importantly, anti-C5 treatment completely rescued mice from TRALI, suggesting the potential role of existing anti-C5 drugs in the treatment of patients with TRALI caused by anti-CD36.

Exploring the pathophysiological mechanism of interstitial edema focusing on the role of macrophages and their interaction with the glycocalyx

OBJECTIVES

Glycocalyx lines the vascular intraluminal space that regulates fluid movement between the intra- and extra-vascular compartments. The depletion of glycocalyx (GCX) is associated with leukocyte accumulation, possibly causing the endothelial cells to become hyperpermeable in various organs, including oral tissues. Whether neutrophils or macrophages are responsible for developing interstitial edema remains controversial. We explored the pathophysiological mechanism of interstitial edema by examining the role of reactive neutrophils and macrophages and their interactions with GCX.

METHODS

An anti-MHC class I antibody was administered intravenously to male BALB/c mice to induce pulmonary edema. Pulmonary edema was evaluated by measuring the lung wet-to-dry weight ratio. Changes in the GCX were evaluated by electron microscopy and measurements of the serum level of soluble syndecan-1. Heparin sulfate was administered to examine its protective effect on the GCX. The macrophages were depleted using clodronate to examine their role in developing edema.

RESULTS

The GCX degradation induced by the anti-MHC class I antibody was accompanied by increased serum syndecan-1 and heparan sulfate levels. Macrophage depletion inhibited the development of pulmonary edema, and the administration of supplemental heparin suppressed the edema.

CONCLUSIONS

We demonstrated that the degradation of the GCX induced by the anti-MHC class I antibody was suppressed by macrophage depletion. These results suggest that macrophages may play a key role in interstitial edema. Heparin inhibited both the degradation of the GCX and interstitial edema. This study's results may be extrapolated to develop an interventional strategy for inhibiting interstitial edema in various organs.

Platelet transfusion in adults: An update

Many patients worldwide receive platelet components (PCs) through the transfusion of diverse types of blood components. PC transfusions are essential for the treatment of central thrombocytopenia of diverse causes, and such treatment is beneficial in patients at risk of severe bleeding. PC transfusions account for almost 10% of all the blood components supplied by blood services, but they are associated with about 3.25 times as many severe reactions (attributable to transfusion) than red blood cell transfusions after stringent in-process leukoreduction to less than 10⁶ residual cells per blood component. PCs are not homogeneous, due to the considerable differences between donors. Furthermore, the modes of PC collection and preparation, the safety precautions taken to limit either the most common (allergic-type reactions and febrile non-hemolytic reactions) or the most severe (bacterial contamination, pulmonary lesions) adverse reactions, and storage and conservation methods can all result in so-called PC "storage lesions". Some storage lesions affect PC quality, with implications for patient outcome. Good transfusion practices should result in higher levels of platelet recovery and efficacy, and lower complication rates. These practices include a matching of tissue ABH antigens whenever possible, and of platelet HLA (and, to a lesser extent, HPA) antigens in immunization situations. This review provides an overview of all the available information relating to platelet transfusion, from donor and donation to bedside transfusion, and considers the impact of the measures applied to increase transfusion efficacy while improving safety and preventing transfusion inefficacy and refractoriness. It also considers alternatives to platelet component (PC) transfusion.

Immunotherapy strategies and prospects for acute lung injury: Focus on immune cells and cytokines

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a disastrous condition, which can be caused by a wide range of diseases, such as pneumonia, sepsis, traumas, and the most recent, COVID-19. Even though we have gained an improved understanding of acute lung injury/acute respiratory distress syndrome pathogenesis and treatment mechanism, there is still no effective treatment for acute lung injury/acute respiratory distress syndrome, which is partly responsible for the unacceptable mortality rate. In the pathogenesis of acute lung injury, the inflammatory storm is the main pathological feature. More and more evidences show that immune cells and cytokines secreted by immune cells play an irreplaceable role in the pathogenesis of acute lung injury. Therefore, here we mainly reviewed the role of various immune cells in acute lung injury from the perspective of immunotherapy, and elaborated the crosstalk of immune cells and cytokines, aiming to provide novel ideas and targets for the treatment of acute lung injury.

Platelets as Key Factors in Inflammation: Focus on CD40L/CD40

Platelets are anucleate cytoplasmic fragments derived from the fragmentation of medullary megakaryocytes. Activated platelets adhere to the damaged endothelium by means of glycoproteins on their surface, forming the platelet plug. Activated platelets can also secrete the contents of their granules, notably the growth factors contained in the α-granules, which are involved in platelet aggregation and maintain endothelial activation, but also contribute to vascular repair and angiogenesis. Platelets also have a major inflammatory and immune function in antibacterial defence, essentially through their Toll-like Receptors (TLRs) and Sialic acid-binding immunoglobulin-type lectin (SIGLEC). Platelet activation also contributes to the extensive release of anti- or pro-inflammatory mediators such as IL-1β, RANTES (Regulated on Activation, Normal T Expressed and Secreted) or CD154, also known as the CD40-ligand. Platelets are involved in the direct activation of immune cells, polynuclear neutrophils (PNNs) and dendritic cells via the CD40L/CD40 complex. As a general rule, all of the studies presented in this review show that platelets are capable of covering most of the stages of inflammation, primarily through the CD40L/CD40 interaction, thus confirming their own role in this pathophysiological condition.

Platelet FcγRIIA-induced serotonin release exacerbates the severity of transfusion-related acute lung injury in mice

Transfusion-related acute lung injury (TRALI) remains a major cause of transfusion-related fatalities. The mechanism of human antibody-mediated TRALI, especially the involvement of the Fcγ receptors, is not clearly established. Contrary to mice, human platelets are unique in their expression of the FcγRIIA/CD32A receptor, suggesting that our understanding of the pathogenesis of antibody-mediated TRALI is partial, as the current murine models incompletely recapitulate the human immunology. We evaluated the role of FcγRIIA/CD32A in TRALI using a humanized mouse model expressing the FcγRIIA/CD32A receptor. When challenged with a recombinant chimeric human immunoglobulin G1/mouse anti-major histocompatibility complex class I monoclonal antibody, these mice exhibited exacerbated alveolar edema and higher mortality compared with wild-type (WT) mice. Unlike in WT mice, monocytes/macrophages in CD32A+ mice were accessory for TRALI initiation, indicating the decisive contribution of another cell type. Platelet activation was dramatically increased in CD32A+ animals, resulting in their increased consumption and massive release of their granule contents. Platelet depletion prevented the exacerbation of TRALI in CD32A+ mice but did not affect TRALI in WT animals. By blocking platelet serotonin uptake with fluoxetine, we showed that the severity of TRALI in CD32A+ mice resulted from the serotonin released by the activated platelets. Furthermore, inhibition of 5-hydroxytryptamine 2A serotonin receptor with sarpogrelate, before or after the induction of TRALI, abolished the aggravation of lung edema in CD32A+ mice. Our findings show that platelet FcγRIIA/CD32A activation exacerbates antibody-mediated TRALI and provide a rationale for designing prophylactic and therapeutic strategies targeting the serotonin pathway to attenuate TRALI in patients.

Inflammasome activation promotes venous thrombosis through pyroptosis

Crosstalk between coagulation and innate immunity contributes to the progression of many diseases, including infection and cardiovascular disease. Venous thromboembolism (VTE), including pulmonary embolism and deep vein thrombosis (DVT), is among the most common causes of cardiovascular death. Here, we show that inflammasome activation and subsequent pyroptosis play an important role in the development of venous thrombosis. Using a flow restriction-induced mouse venous thrombosis model in the inferior vena cava (IVC), we show that deficiency of caspase-1, but not caspase-11, protected against flow restriction-induced thrombosis. Interleukin-1β expression increased in the IVC following ligation, indicating that inflammasome is activated during injury. Deficiency of gasdermin D (GSDMD), an essential mediator of pyroptosis, protected against restriction-induced venous thrombosis. After induction of venous thrombosis, fibrin was deposited in the veins of wild-type mice, as detected using immunoblotting with a monoclonal antibody that specifically recognizes mouse fibrin, but not in the caspase-1-deficient or GSDMD-deficient mice. Depletion of macrophages by gadolinium chloride or deficiency of tissue factor also protected against venous thrombosis. Our data reveal that tissue factor released from pyroptotic monocytes and macrophages following inflammasome activation triggers thrombosis.

Update on the pathophysiology of transfusion-related acute lung injury

PURPOSE OF REVIEW

The aim of this study was to discuss recent advances regarding the pathogenesis of transfusion-related acute lung injury (TRALI), which highlight the pathogenic role of macrophages.

RECENT FINDINGS

TRALI remains a leading cause of transfusion-related fatalities, despite the success of the mitigation strategy, and therapeutic approaches are unavailable. Neutrophils (PMNs) are recognized pathogenic cells in TRALI. Macrophages have previously also been suggested to be pathogenic in mice via binding of C5a to their C5a-receptor, producing reactive oxygen species (ROS), which damages the pulmonary endothelium. Recent work has further highlighted the role of macrophages in the TRALI-pathogenesis. It has been shown that the protein osteopontin (OPN) released by macrophages is critical for pulmonary PMN recruitment in mice suffering from TRALI and that targeting OPN prevents the occurrence of TRALI. Another recent study demonstrated the importance of M1-polarized alveolar macrophages in murine TRALI induction by showing that α1-antitrypsin (AAT) overexpression prevented TRALI in mice through decreasing the polarization of alveolar macrophages towards the M1 phenotype.

SUMMARY

Apart from PMNs, macrophages also appear to be important in the pathogenesis of TRALI. Targeting the pathogenic functions of macrophages may be a promising therapeutic strategy to explore in TRALI.

Biological and structural characterization of murine TRALI antibody reveals increased Fc-mediated complement activation

Transfusion-related acute lung injury (TRALI) remains a leading cause of transfusion-related deaths. In most cases, anti-leukocyte antibodies in the transfusion product trigger TRALI, but not all anti-leukocyte antibodies cause TRALI. It has been shown that the anti-major histocompatibility complex (MHC) class I antibody 34-1-2S (anti-H-2Kd) causes TRALI in BALB/c mice (MHC class I haplotype H-2Kd), whereas SF1.1.10 (anti-H-2Kd) does not. In C57BL/6 mice (MHC class I haplotype H-2Kb), TRALI only occurs when anti-MHC class I antibody AF6-88.5.5.3 (anti-H-2Kb) is administered together with a high dose of 34-1-2S. It remains unknown which specific antibody characteristics are responsible for eliciting TRALI. We therefore investigated several biological and structural features of 34-1-2S compared with other anti-MHC class I antibodies, which on their own do not cause TRALI: SF1.1.10 and AF6-88.5.5.3. No substantial differences were observed between the TRALI-causing 34-1-2S and the TRALI-resistant SF1.1.10 regarding binding affinity to H-2Kd. Regarding binding affinity to H-2Kb, only AF6-88.5.5.3 potently bound to H-2Kb, whereas 34-1-2S exhibited weak but significant cross-reactivity. Furthermore, the binding affinity to FcγRs as well as the Fc glycan composition seemed to be similar for all antibodies. Similar Fc glycosylation profiles were also observed for human TRALI-causing donor anti-HLA antibodies compared with human anti-HLA antibodies from control donors. 34-1-2S, however, displayed superior complement activation capacity, which was fully Fc dependent and not significantly dependent on Fc glycosylation. We conclude that TRALI induction is not correlated with Fab- and Fc-binding affinities for antigen and FcγRs, respectively, nor with the composition of Fc glycans; but increased Fc-mediated complement activation is correlated with TRALI induction.

The Immune System in Transfusion-Related Acute Lung Injury Prevention and Therapy: Update and Perspective

As an initiator of respiratory distress, transfusion-related acute lung injury (TRALI) is regarded as one of the rare complications associated with transfusion medicine. However, to date, the pathogenesis of TRALI is still unclear, and specific therapies are unavailable. Understanding the mechanisms of TRALI may promote the design of preventive and therapeutic strategies. The immune system plays vital roles in reproduction, development and homeostasis. Sterile tissue damage, such as physical trauma, ischemia, or reperfusion injury, induces an inflammatory reaction that results in wound healing and regenerative mechanisms. In other words, in addition to protecting against pathogens, the immune response may be strongly associated with TRALI prevention and treatment through a variety of immunomodulatory strategies to inhibit excessive immune system activation. Immunotherapy based on immune cells or immunological targets may eradicate complications. For example, IL-10 therapy is a promising therapeutic strategy to explore further. This review will focus on ultramodern advances in our understanding of the potential role of the immune system in TRALI prevention and treatment.

Frequency and timing of all-cause deaths in visits involving suspected transfusion reactions, and the significance of cardiopulmonary disturbances

BACKGROUND/OBJECTIVES

Transfusion reactions (TRs) may cause or contribute to death. Cardiopulmonary TRs are distressing, and collectively account for most transfusion fatalities, though the degree to which they alter survival more broadly is unclear. Deaths (and their timing) after TRs may provide further insights.

MATERIALS/METHODS

Adult (tri-hospital network) haemovigilance data (2013-2016) recorded referrals with conclusions ranging from unrelated to transfusion (UTR) to entities such as: septic TRs, serologic/haemolytic reactions, transfusion-associated circulatory overload (TACO), transfusion-associated dyspnoea (TAD), transfusion-related acute lung injury (TRALI), allergic transfusion reaction (ATR), and others. For (in- or out-patient) visits involving suspected TRs (VISTRs), all-cause mortalities (% [95% confidence interval]) and associated time-to-death (TTD) (median days, [interquartile range]) were compared. Diagnoses were defined inclusively (possible-to-definite) or strictly (probable-to-definite).

RESULTS

Of 1144 events, rank order VISTR mortality following (possible-to-definite) TRs, and associated TTDs, were led by: DHTR 33% [6-19], 1 death at 123d; TRALI 32% [15-54], 6 deaths: 3d [2-20]; BaCon 21% [14-31], 17 deaths: 10d [3-28]; TACO 18% [12-26], 23 deaths: 16d [6-28]; TAD 17% [11-26]: 18 deaths, 6d [3-12]. Higher-certainty TRs ranked similarly (DHTR 50% [9-91]; BaCon 29% [12-55], 4 deaths: 12d [3-22]; and TACO 25% [16-38], 15 deaths: 21d [6-28]). VISTR mortality after TACO or TRALI significantly exceeded ATR (3·3% [2·4-5·8], P < 0·00001) but was not different from UTR events (P = 0·3).

CONCLUSIONS

Only half of cardiopulmonary TRs constituted high certainty diagnoses. Nevertheless, cardiopulmonary TRs and suspected BaCon marked higher VISTR mortality with shorter TTDs. Short (<1 week) TTDs in TAD, BaCon or TRALI imply either contributing roles in death, treatment refractoriness and/or applicable TR susceptibilities in the dying.

Complement activation on endothelium initiates antibody-mediated acute lung injury

Antibodies targeting human leukocyte antigen (HLA)/major histocompatibility complex (MHC) proteins limit successful transplantation and transfusion, and their presence in blood products can cause lethal transfusion-related acute lung injury (TRALI). It is unclear which cell types are bound by these anti-leukocyte antibodies to initiate an immunologic cascade resulting in lung injury. We therefore conditionally removed MHC class I (MHC I) from likely cellular targets in antibody-mediated lung injury. Only the removal of endothelial MHC I reduced lung injury and mortality, related mechanistically to absent endothelial complement fixation and lung platelet retention. Restoration of endothelial MHC I rendered MHC I-deficient mice susceptible to lung injury. Neutrophil responses, including neutrophil extracellular trap (NET) release, were intact in endothelial MHC I-deficient mice, whereas complement depletion reduced both lung injury and NETs. Human pulmonary endothelial cells showed high HLA class I expression, and posttransfusion complement activation was increased in clinical TRALI. These results indicate that the critical source of antigen for anti-leukocyte antibodies is in fact the endothelium, which reframes our understanding of TRALI as a rapid-onset vasculitis. Inhibition of complement activation may have multiple beneficial effects of reducing endothelial injury, platelet retention, and NET release in conditions where antibodies trigger these pathogenic responses.

M1-polarized alveolar macrophages are crucial in a mouse model of transfusion-related acute lung injury

BACKGROUND

The pathogenesis of transfusion-related acute lung injury (TRALI) progress is incompletely understood, and specific therapies for TRALI are lacking. Alveolar macrophages (AMs) are critical for initiation and resolution of lung inflammation. However, the role of AMs in the pathogenesis of TRALI-associated lung failure is poorly understood.

STUDY DESIGN AND METHODS

Mouse model for in vivo imaging of interleukin (IL)-6 activation in AMs was established by intratracheal instillation of a lentiviral vector carrying the luciferase reporter gene. The TRALI mouse model was produced by intraperitoneal lipopolysaccharide plus intravenous major histocompatibility complex Class I monoclonal antibody treatment. We focused on the changes in AMs in the lung during TRALI and examined whether targeting AMs is an effective strategy to alleviate this condition.

MEASUREMENTS AND MAIN RESULTS

We confirmed that TRALI progress is accompanied by IL-6 activation in AMs. Further study showed that AMs undergo M1 activation during TRALI progress. AM depletion protected mice from TRALI, and transfusion of M1-polarized AMs into 34-1-2 s-treated mice elevated acute lung injury, indicating that the severity of TRALI was able to be ameliorated by targeting AM polarization. Next, we showed that α₁ -antitrypsin (AAT) expression improved lung injury by modulating the production of IL-6 in AMs and decreased polarization of AMs toward the M1 phenotype.

CONCLUSIONS

M1-polarized AMs are crucial in a mouse model of TRALI, and AAT may serve as a future treatment for TRALI by regulating the polarization of AMs.

Targeting Transfusion-Related Acute Lung Injury: The Journey From Basic Science to Novel Therapies

OBJECTIVES

Transfusion-related acute lung injury is characterized by the onset of respiratory distress and acute lung injury following blood transfusion, but its pathogenesis remains poorly understood. Generally, a two-hit model is presumed to underlie transfusion-related acute lung injury with the first hit being risk factors present in the transfused patient (such as inflammation), whereas the second hit is conveyed by factors in the transfused donor blood (such as antileukocyte antibodies). At least 80% of transfusion-related acute lung injury cases are related to the presence of donor antibodies such as antihuman leukocyte or antihuman neutrophil antibodies. The remaining cases may be related to nonantibody-mediated factors such as biolipids or components related to storage and ageing of the transfused blood cells. At present, transfusion-related acute lung injury is the leading cause of transfusion-related fatalities and no specific therapy is clinically available. In this article, we critically appraise and discuss recent preclinical (bench) insights related to transfusion-related acute lung injury pathogenesis and their therapeutic potential for future use at the patients' bedside in order to combat this devastating and possibly fatal complication of transfusion.

DATA SOURCES

We searched the PubMed database (until August 22, 2017).

STUDY SELECTION

Using terms: "Transfusion-related acute lung injury," "TRALI," "TRALI and therapy," "TRALI pathogenesis."

DATA EXTRACTION

English-written articles focusing on transfusion-related acute lung injury pathogenesis, with potential therapeutic implications, were extracted.

DATA SYNTHESIS

We have identified potential therapeutic approaches based on the literature.

CONCLUSIONS

We propose that the most promising therapeutic strategies to explore are interleukin-10 therapy, down-modulating C-reactive protein levels, targeting reactive oxygen species, or blocking the interleukin-8 receptors; all focused on the transfused recipient. In the long-run, it may perhaps also be advantageous to explore other strategies aimed at the transfused recipient or aimed toward the blood product, but these will require more validation and confirmation first.

Transfusion-related Acute Lung Injury in the Perioperative Patient

Transfusion-related acute lung injury is a leading cause of death associated with the use of blood products. Transfusion-related acute lung injury is a diagnosis of exclusion which can be difficult to identify during surgery amid the various physiologic and pathophysiologic changes associated with the perioperative period. As anesthesiologists supervise delivery of a large portion of inpatient prescribed blood products, and since the incidence of transfusion-related acute lung injury in the perioperative patient is higher than in nonsurgical patients, anesthesiologists need to consider transfusion-related acute lung injury in the perioperative setting, identify at-risk patients, recognize early signs of transfusion-related acute lung injury, and have established strategies for its prevention and treatment.

Evidence of CD40L/CD40 pathway involvement in experimental transfusion-related acute lung injury

Platelet transfusions can cause adverse reactions in their recipients, including transfusion-related acute lung injury (TRALI). The pathophysiology of TRALI depends on a number of signaling pathways and the inflammatory role played by blood platelets remains controversial. Platelets are important in inflammation, particularly via the immunomodulator complex CD40/CD40L. We studied the specific function of the CD40/CD40L interaction in regulating an experimental TRALI Two-hit model. A mouse model of immune TRALI was triggered by injection of LPS and an anti-MHC I antibody, and the effect of injection of a neutralizing anti-CD40L antibody before induction of TRALI investigated. The characteristics of TRALI were decreased body temperature, pulmonary lesions, and immune cell infiltration into the alveolar space. Pulmonary infiltration was evaluated by blood counts of specific immune cells and their detection in lung sections. Inhibition of the CD40/CD40L immunomodulator interaction significantly reduced communication between immune and/or endothelial cells and the development of pulmonary edema. Hence, our results indicate that targeting of the CD40/CD40L interaction could be an important method to prevent TRALI. While considering that our work concerned a mouse model, we postulate that improvement of the conditions under which platelet concentrates are prepared/stored would assist in alleviating the risk of TRALI.

Blood transfusion associated lung injury

Transfusions of blood and blood products are live-saving, but complications may be fatal. Transfusion related lung injury (TRALI) is rare and pathophysiology not yet entirely understood. Diagnosis is difficult due to the usually life-threatening circumstances associated with transfusions and underlying diseases. In this mini-review article, we introduce two cases of TRALI to discuss the problems and controversies associated with different definitions, epidemiology, pathophysiology, blood products, diagnosis, and treatment. Future directions in the field are highlighted.

Osteopontin mediates murine transfusion-related acute lung injury via stimulation of pulmonary neutrophil accumulation

Transfusion-related acute lung injury (TRALI) is one of the leading causes of transfusion-related fatalities and is characterized by the onset of acute respiratory distress within 6 hours upon blood transfusion. Specific therapies are unavailable. Preexisting inflammation is a risk factor for TRALI and neutrophils (polymorphonuclear neutrophils [PMNs]) are considered to be the major pathogenic cells. Osteopontin (OPN) is a multifunctional protein expressed at sites of inflammation and, for example, is involved in pulmonary disorders, can regulate cellular migration, and can function as a PMN chemoattractant. We investigated whether OPN is involved in TRALI induction by promoting PMN recruitment to the lungs. Using a previously established murine TRALI model, we found that in contrast to wild-type (WT) mice, OPN knockout (KO) mice were resistant to antibody-mediated PMN-dependent TRALI induction. Administration of purified OPN to the OPN KO mice, however, restored the TRALI response and pulmonary PMN accumulation. Alternatively, blockade of OPN in WT mice using an anti-OPN antibody prevented the onset of TRALI induction. Using pulmonary immunohistochemistry, OPN could be specifically detected in the lungs of mice that suffered from TRALI. The OPN-mediated TRALI response seemed dependent on macrophages, likely the cellular source of OPN and OPN polymerization, and independent from the OPN receptor CD44, interleukin 6 (IL-6), and other PMN chemoattractants including macrophage inflammatory protein-2 (MIP-2). These data indicate that OPN is critically required for induction of antibody-mediated murine TRALI through localization to the lungs and stimulation of pulmonary PMN recruitment. This suggests that anti-OPN antibody therapy may be a potential therapeutic strategy to explore in TRALI patients.

Microarray profiling of lung long non-coding RNAs and mRNAs in lipopolysaccharide-induced acute lung injury mouse model

Long non-coding RNAs (lncRNAs) are involved in various biological processes as well as many respiratory diseases, while the role of lncRNAs in acute lung injury (ALI) remains unclear. The present study aimed to profile the expression of lung lncRNAs and mRNAs in lipopolysaccharide (LPS)-induced ALI mouse model. C57BL/6 mice were exposed to LPS or phosphate-buffered saline for 24 h, and lncRNAs and mRNAs were profiled by Arraystar mouse LncRNA Array V3.0. Bioinformatics analysis gene ontology including (GO) and pathway analysis and cell study in vitro was used to investigate potential mechanisms. Based on the microarray results, 2632 lncRNAs and 2352 mRNAs were differentially expressed between ALI and control mice. The microarray results were confirmed by the quantitative real-time PCR (qRT-PCR) results of ten randomized selected lncRNAs. GO analysis showed that the altered mRNAs were mainly related to the processes of immune system, immune response and defense response. Pathway analysis suggests that tumor necrosis factor (TNF) signaling pathway, NOD-like receptor pathway, and cytokine-cytokine receptor interaction may be involved in ALI. LncRNA-mRNA co-expression network analysis indicated that one individual lncRNA may interact with several mRNAs, and one individual mRNA may also interact with several lncRNAs. Small interfering RNA (siRNA) for ENSMUST00000170214.1, - ENSMUST00000016031.13 significantly inhibited LPS-induced TNF-α and interleukin (IL)-1β production in murine RAW264.7 macrophages. Our results found significant changes of lncRNAs and mRNAs in the lungs of LPS-induced ALI mouse model, and intervention targeting lncRNAs may attenuate LPS-induced inflammation, which may help to elucidate the role of lncRNAs in the pathogenesis and treatment of ALI.

Gastrointestinal microbiota contributes to the development of murine transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a syndrome of respiratory distress upon blood transfusion and is the leading cause of transfusion-related fatalities. Whether the gut microbiota plays any role in the development of TRALI is currently unknown. We observed that untreated barrier-free (BF) mice suffered from severe antibody-mediated acute lung injury, whereas the more sterile housed specific pathogen-free (SPF) mice and gut flora-depleted BF mice were both protected from lung injury. The prevention of TRALI in the SPF mice and gut flora-depleted BF mice was associated with decreased plasma macrophage inflammatory protein-2 levels as well as decreased pulmonary neutrophil accumulation. DNA sequencing of amplicons of the 16S ribosomal RNA gene revealed a varying gastrointestinal bacterial composition between BF and SPF mice. BF fecal matter transferred into SPF mice significantly restored TRALI susceptibility in SPF mice. These data reveal a link between the gut flora composition and the development of antibody-mediated TRALI in mice. Assessment of gut microbial composition may help in TRALI risk assessment before transfusion.

The ATP-gated P2X1 ion channel contributes to the severity of antibody-mediated Transfusion-Related Acute Lung Injury in mice

The biological responses that control the development of Transfusion-Related Acute Lung Injury (TRALI), a serious post-transfusion respiratory syndrome, still need to be clarified. Since extracellular nucleotides and their P2 receptors participate in inflammatory processes as well as in cellular responses to stress, we investigated the role of the ATP-gated P2X₁ cation channel in antibody-mediated TRALI. The effects of NF449, a selective P2X1 receptor (P2RX1) antagonist, were analyzed in a mouse two-hit model of TRALI. Mice were primed with lipopolysaccharide (LPS) and 24 h later challenged by administrating an anti-MHC I antibody. The selective P2RX1 antagonist NF449 was administrated before the administration of LPS and/or the anti-MHC I antibody. When given before antibody administration, NF449 improved survival while maximal protection was achieved when NF449 was also administrated before the sensitization step. Under this later condition, protein contents in bronchoalveolar lavages were dramatically reduced. Cell depletion experiments indicated that monocytes/macrophages, but not neutrophils, contribute to this effect. In addition, the reduced lung periarteriolar interstitial edemas in NF449-treated mice suggested that P2RX1 from arteriolar smooth muscle cells could represent a target of NF449. Accordingly, inhibition of TRPC6, another cation channel expressed by smooth muscle cells, also reduced TRALI-associated pulmonary interstitial and alveolar edemas. These data strongly suggest that cation channels like P2RX1 or TRPC6 participate to TRALI pathological responses.

Transfusion-associated circulatory overload and transfusion-related acute lung injury

Transfusion-associated circulatory overload (TACO) and transfusion-related acute lung injury (TRALI) are syndromes of acute respiratory distress that occur within 6 hours of blood transfusion. TACO and TRALI are the leading causes of transfusion-related fatalities, and specific therapies are unavailable. Diagnostically, it remains very challenging to distinguish TACO and TRALI from underlying causes of lung injury and/or fluid overload as well as from each other. TACO is characterized by pulmonary hydrostatic (cardiogenic) edema, whereas TRALI presents as pulmonary permeability edema (noncardiogenic). The pathophysiology of both syndromes is complex and incompletely understood. A 2-hit model is generally assumed to underlie TACO and TRALI disease pathology, where the first hit represents the clinical condition of the patient and the second hit is conveyed by the transfusion product. In TACO, cardiac or renal impairment and positive fluid balance appear first hits, whereas suboptimal fluid management or other components in the transfused product may enable the second hit. Remarkably, other factors beyond volume play a role in TACO. In TRALI, the first hit can, for example, be represented by inflammation, whereas the second hit is assumed to be caused by antileukocyte antibodies or biological response modifiers (eg, lipids). In this review, we provide an up-to-date overview of TACO and TRALI regarding clinical definitions, diagnostic strategies, pathophysiological mechanisms, and potential therapies. More research is required to better understand TACO and TRALI pathophysiology, and more biomarker studies are warranted. Collectively, this may result in improved diagnostics and development of therapeutic approaches for these life-threatening transfusion reactions.

TACO and TRALI: biology, risk factors, and prevention strategies

Transfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are the leading causes of transfusion-related morbidity and mortality. These adverse events are characterized by acute pulmonary edema within 6 hours of a blood transfusion and have historically been difficult to study due to underrecognition and nonspecific diagnostic criteria. However, in the past decade, in vivo models and clinical studies utilizing active surveillance have advanced our understanding of their epidemiology and pathogenesis. With the adoption of mitigation strategies and patient blood management, the incidence of TRALI and TACO has decreased. Continued research to prevent and treat these severe cardiopulmonary events is focused on both the blood component and the transfusion recipient.

Gadolinium chloride attenuates acetic acid-evoked colitis in mice by reducing neutrophil infiltration and pro-oxidative enzyme activity

This study investigated the potential of gadolinium chloride (GdCl₃), an inhibitor of kupffer cells on the myeloperoxidase (MPO) function, both in vivo on colon inflammation model and in vitro on thioglycollate-elicited peritoneal neutrophils. Colon inflammation was induced in mice (n = 7) by 4% acetic acid (AA) enema. GdCl₃ (10 mg/kg) treatment was given 24 h before AA challenge. Clinical changes during the protocol were scored. Colons were segmented into distal and proximal parts for histological and biochemical assessment. Furthermore, myeloperoxidase (MPO) enzymes were extracted and analyzed by western blot. Short-term GdCl₃ treatment inhibited dose-dependently superoxide anion (O₂^·-), alkaline phosphatase (ALP), and MPO release and promoted neutrophil apoptosis. In vivo, low-dose GdCl₃ improved colitis scores and inhibited acute phagocyte recruitment and colon damage within the mucosa as revealed by the decrease in MPO, nitric oxide (NO), and malondialdehyde (MDA) levels. At the same time, GdCl₃ restored catalase (CAT), superoxide dismutase (SOD) activities, and reduced glutathione (GSH) levels, thus reversing the MDA/GSH ratio in both distal and proximal colons. Compared to proximal, distal colon was more altered and displayed higher pathological manifestations. Lastly, the induction of apoptosis and regulation of the major nitrosative and oxidative functions of neutrophils by GdCl₃ suggests its consideration as a beneficial tool in attenuating colon inflammation.

The Pathogenic Involvement of Neutrophils in Acute Respiratory Distress Syndrome and Transfusion-Related Acute Lung Injury

The acute respiratory distress syndrome (ARDS) is a serious and common complication of multiple medical and surgical interventions, with sepsis, pneumonia, and aspiration of gastric contents being common risk factors. ARDS develops within 1 week of a known clinical insult or presents with new/worsening respiratory symptoms if the clinical insult is unknown. Approximately 40% of the ARDS cases have a fatal outcome. Transfusion-related acute lung injury (TRALI), on the other hand, is characterized by the occurrence of respiratory distress and acute lung injury, which presents within 6 h after administration of a blood transfusion. In contrast to ARDS, acute lung injury in TRALI is not attributable to another risk factor for acute lung injury. 'Possible TRALI', however, may have a clear temporal relationship to an alternative risk factor for acute lung injury. Risk factors for TRALI include chronic alcohol abuse and systemic inflammation. TRALI is the leading cause of transfusion-related fatalities. There are no specific therapies available for ARDS or TRALI as both have a complex and incompletely understood pathogenesis. Neutrophils (polymorphonuclear leukocytes; PMNs) have been suggested to be key effector cells in the pathogenesis of both syndromes. In the present paper, we summarize the literature with regard to PMN involvement in the pathogenesis of both ARDS and TRALI based on both human data as well as on animal models. The evidence generally supports a strong role for PMNs in both ARDS and TRALI. More research is required to shed light on the pathogenesis of these respiratory syndromes and to more thoroughly establish the nature of the PMN involvement, especially considering the heterogeneous etiologies of ARDS.

Donor pulmonary intravascular nonclassical monocytes recruit recipient neutrophils and mediate primary lung allograft dysfunction

Primary graft dysfunction is the predominant driver of mortality and graft loss after lung transplantation. Recruitment of neutrophils as a result of ischemia-reperfusion injury is thought to cause primary graft dysfunction; however, the mechanisms that regulate neutrophil influx into the injured lung are incompletely understood. We found that donor-derived intravascular nonclassical monocytes (NCMs) are retained in human and murine donor lungs used in transplantation and can be visualized at sites of endothelial injury after reperfusion. When NCMs in the donor lungs were depleted, either pharmacologically or genetically, neutrophil influx and lung graft injury were attenuated in both allogeneic and syngeneic models. Similar protection was observed when the patrolling function of donor NCMs was impaired by deletion of the fractalkine receptor CX3CR1. Unbiased transcriptomic profiling revealed up-regulation of MyD88 pathway genes and a key neutrophil chemoattractant, CXCL2, in donor-derived NCMs after reperfusion. Reconstitution of NCM-depleted donor lungs with wild-type but not MyD88-deficient NCMs rescued neutrophil migration. Donor NCMs, through MyD88 signaling, were responsible for CXCL2 production in the allograft and neutralization of CXCL2 attenuated neutrophil influx. These findings suggest that therapies to deplete or inhibit NCMs in donor lung might ameliorate primary graft dysfunction with minimal toxicity to the recipient.

Mirasol pathogen reduction technology treatment of human whole blood does not induce acute lung injury in mice

In resource-limited settings and in the military theater, fresh human whole blood is commonly transfused, but infectious risks are a concern. Sophisticated molecular testing for potential infectious agents in the whole blood is often unavailable. To address this unmet need, pathogen reduction technology (PRT) has been developed, and it is an effective approach to inactivate a broad range of pathogens found in human blood. However, studies are needed to determine if it is harmful to blood cells and whether these cells could damage the transfused recipient, including the development of acute lung injury/acute respiratory distress syndrome. In this study, we used a commercial PRT system to treat human whole blood that was then transfused into immunodeficient mice, and the development of acute lung injury was determined. In a model of transfusion-related acute lung injury (TRALI), BALB/c SCID mice developed more robust lung injury when challenged with a MHC Class I monoclonal antibody compared to BALB/c wild-type and NOD/SCID mice. Transfusion of control versus Mirasol PRT-treated whole blood (25% blood volume exchange) into BALB/c SCID mice did not produce lung injury at storage day 1. However, mild lung injury at storage days 14 and 21 was observed without significant differences in lung injury measurements between Mirasol PRT-treated and control groups. The mild storage-dependent acute lung injury correlated with trends for increased levels of cell-free hemoglobin that accumulated in both the control and Mirasol PRT-treated groups. Neutrophil extracellular traps were elevated in the plasma of BALB/c SCID mice in the monoclonal antibody TRALI model, but were not different in mice that received exchange transfusions. In conclusion, exchange transfusion of human whole blood into immunodeficient mice produces mild lung injury that is storage-dependent and not related to pathogen reduction treatment.

Prostaglandin-endoperoxide synthase-2 deletion affects the natural trafficking of Annexin A2 in monocytes and favours venous thrombosis in mice

Deep-vein thrombosis (DVT) is a common condition that often leads to pulmonary thromboembolism (VTE) and death. The role of prostaglandin-endoperoxide synthase (PTGS)2 in arterial thrombosis has been well established, whereas its impact in venous thrombosis remains unclear. Here, we showed that PTGS2 deletion predisposes to venous thrombosis as suggested by greater clot firmness and clot elasticity, by higher plasma levels of functional fibrinogen, factor VIII and PAI-1 activity, and proved by bigger thrombi detected after inferior vena cava ligation (IVCL) compared to WT mice. PTGS2^-/- thrombi have greater fibrin content, higher number of F4/80⁺, TF⁺ and ANXA2⁺ cells, and lower S100A10⁺ cells. Remarkably, monocyte depletion reduced thrombus size in mutant mice, suggesting an important role of PTGS2^-/- monocytes in this experimental setting. Interestingly, PTGS2 deletion reduced membrane ANXA2, and total S100A10, promoted assembly of ANXA2/p50NF-kB complex and its nuclear accumulation, and induced TF in peritoneal macrophages, whereas ANXA2 silencing decreased dramatically TF. Finally, Carbaprostacyclin treatment prevented venous thrombus formation induced by IVCL in mutant mice, reduced the ANXA2 binding to p50NF-kB subunit and its nuclear trafficking, and decreased TF in PTGS2^-/- macrophages. PTGS2 deletion, changing the natural distribution of ANXA2 in monocytes/macrophages, increases TF expression and activity predisposing to venous thrombosis. Interestingly, Carbaprostacyclin treatment, inhibiting nuclear ANXA2 trafficking, controls monocyte TF activity and prevents DVT occurrence. Our data are of help in elucidating the mechanisms by which PTGS2 inhibition increases DVT risk, and suggest a new role for ANXA2 in venous thrombosis.

Intravascular donor monocytes play a central role in lung transplant ischaemia-reperfusion injury

Rationale

Primary graft dysfunction in lung transplant recipients derives from the initial, largely leukocyte-dependent, ischaemia-reperfusion injury. Intravascular lung-marginated monocytes have been shown to play key roles in experimental acute lung injury, but their contribution to lung ischaemia-reperfusion injury post transplantation is unknown.

Objective

To define the role of donor intravascular monocytes in lung transplant-related acute lung injury and primary graft dysfunction.

Methods

Isolated perfused C57BL/6 murine lungs were subjected to warm ischaemia (2 hours) and reperfusion (2 hours) under normoxic conditions. Monocyte retention, activation phenotype and the effects of their depletion by intravenous clodronate-liposome treatment on lung inflammation and injury were determined. In human donor lung transplant samples, the presence and activation phenotype of monocytic cells (low side scatter, 27E10+, CD14+, HLA-DR+, CCR2+) were evaluated by flow cytometry and compared with post-implantation lung function.

Results

In mouse lungs following ischaemia-reperfusion, substantial numbers of lung-marginated monocytes remained within the pulmonary microvasculature, with reduced L-selectin and increased CD86 expression indicating their activation. Monocyte depletion resulted in reductions in lung wet:dry ratios, bronchoalveolar lavage fluid protein, and perfusate levels of RAGE, MIP-2 and KC, while monocyte repletion resulted in a partial restoration of the injury. In human lungs, correlations were observed between pre-implantation donor monocyte numbers/their CD86 and TREM-1 expression and post-implantation lung dysfunction at 48 and 72 hours.

Conclusions

These results indicate that lung-marginated intravascular monocytes are retained as a ‘passenger’ leukocyte population during lung transplantation, and play a key role in the development of transplant-associated ischaemia-reperfusion injury.

Duration of red blood cell storage and inflammatory marker generation

Red blood cell (RBC) transfusion is a life-saving treatment for several pathologies. RBCs for transfusion are stored refrigerated in a preservative solution, which extends their shelf-life for up to 42 days. During storage, the RBCs endure abundant physicochemical changes, named RBC storage lesions, which affect the overall quality standard, the functional integrity and in vivo survival of the transfused RBCs. Some of the changes occurring in the early stages of the storage period (for approximately two weeks) are reversible but become irreversible later on as the storage is extended. In this review, we aim to decipher the duration of RBC storage and inflammatory marker generation. This phenomenon is included as one of the causes of transfusion-related immunomodulation (TRIM), an emerging concept developed to potentially elucidate numerous clinical observations that suggest that RBC transfusion is associated with increased inflammatory events or effects with clinical consequence.

T regulatory cells and dendritic cells protect against transfusion-related acute lung injury via IL-10

Transfusion-related acute lung injury (TRALI) is the leading cause of transfusion-related fatalities and is characterized by acute respiratory distress following blood transfusion. Donor antibodies are frequently involved; however, the pathogenesis and protective mechanisms in the recipient are poorly understood, and specific therapies are lacking. Using newly developed murine TRALI models based on injection of anti-major histocompatibility complex class I antibodies, we found CD4⁺CD25⁺FoxP3⁺ T regulatory cells (Tregs) and CD11c⁺ dendritic cells (DCs) to be critical effectors that protect against TRALI. Treg or DC depletion in vivo resulted in aggravated antibody-mediated acute lung injury within 90 minutes with 60% mortality upon DC depletion. In addition, resistance to antibody-mediated TRALI was associated with increased interleukin-10 (IL-10) levels, and IL-10 levels were found to be decreased in mice suffering from TRALI. Importantly, IL-10 injection completely prevented and rescued the development of TRALI in mice and may prove to be a promising new therapeutic approach for alleviating lung injury in this serious complication of transfusion.

MicroRNA-7 Deficiency Ameliorates the Pathologies of Acute Lung Injury through Elevating KLF4

Recent evidence showed that microRNA-7 (miR-7) played an important role in the pathologies of lung-related diseases. However, the potential role of miR-7 in acute lung injury (ALI) still remains poorly understood. Here, we assessed the effect of miR-7 deficiency on the pathology of ALI. We, first, found that the expression of miR-7 was upregulated in lung tissue in murine LPS-induced ALI model. Notably, we generated miR-7 knock down mice by using miRNA-Sponge technique and found that miR-7 deficiency could ameliorate the pathologies of lung as evidenced by accelerated body weight recovery, reduced level of bronchoalveolar lavage (BAL) proinflammatory cytokines and decreased number of BAL cells in ALI mice. Moreover, the proportion and number of various immune cells in BAL, including innate immune cell F4/80⁺ macrophages, γδT cells, NK1.1⁺ T cells, and CD11c⁺DCs, as well as adaptive immune cell CD4⁺ T cells and CD8⁺ T cells, also significantly changed, respectively. Mechanistic evidence showed that KLF4, a target molecule of miR-7, was upregulated in lung tissues in ALI model, accompanied by altered transduction of NF-κB, AKT, and ERK pathway. These data provided a previously unknown role of miR-7 in pathology of ALI, which could ultimately aid the understanding of development of ALI and the development of new therapeutic strategies against clinical inflammatory lung diseases.

Ilex kaushue and Its Bioactive Component 3,5-Dicaffeoylquinic Acid Protected Mice from Lipopolysaccharide-Induced Acute Lung Injury

Acute lung injury (ALI) is a severe respiratory disease with high mortality rates worldwide. Recent reports suggest that human neutrophil elastase (HNE) plays a key role in the inflammatory response that is characteristic of ALI, which indicates that the development of HNE inhibitors could be an efficient treatment strategy. In the current study, an enzyme-based screening assay was used to identify effective HNE inhibitors from a number of traditional Chinese medicines (TCMs). Among them, a water extract of Ilex kaushue (IKWE) effectively inhibited HNE activity (IC₅₀, 11.37 ± 1.59 μg/mL). Using bioactivity-guided fractionation, one new compound and 23 known compounds were identified. Compound 6 (identified as 3,5-dicaffeoylquinic acid; 3,5-DCQA) exerted the most potent and selective inhibitory effect on HNE activity (IC₅₀, 1.86 ± 0.06 μM). In a cell-based assay, 3,5-DCQA not only directly reduced superoxide generation and elastase activity but also attenuated the Src family kinase (SRKs)/Vav signaling pathway in N-formyl-L-Met-L-Leu-L-Phe (fMLF)-stimulated human neutrophils. In an animal disease model, both 3,5-DCQA and standardized IKWE protected against lipopolysaccharide-induced ALI in mice, which provides support for their potential as candidates in the development of new therapeutic agents for neutrophilic inflammatory diseases.

Leucocyte cytokines dominate platelet cytokines overtime in non-leucoreduced platelet components

BACKGROUND

Leucoreduction of blood components, including platelet components, is strongly encouraged but not yet universal, especially outside high income countries. As both leucocytes and platelets secrete copious amounts of pro-inflammatory cytokines/chemokines under various conditions and during storage, we investigated the potential of the respective secretory programmes of these cells in order to evaluate their subsequent pathophysiological effects.

MATERIAL AND METHODS

A total of 158 individual non-leucoreduced platelet components were obtained from Tunisian donors and tested for characteristic biological response modifiers (BRM) of leukocytes (IL-1β, IL-8), platelets (sCD62P, sCD40L) and both cell types (TNF-α, RANTES) in the presence or absence of thrombin stimulation and after different periods of storage (up to 5 days). BRM levels were determined using enzyme-linked immunosorbent assays and Luminex technology. Platelet-leucocyte aggregate formation during storage was analysed using flow cytometry.

RESULTS

Leucocyte- and platelet-associated BRM had clearly distinct profiles both at the onset (day 0) and termination (day 5) of the observation period but altered during the intermediate period so that their respective importance was inverted; in fact, the profiles were merged and indistinguishable on days 2-3. The leucocyte-derived BRM largely dominated over platelet-derived ones and further altered the BRM platelet secretion programme.

DISCUSSION

This study contributes substantial, new information on leucocyte/platelet interactions and their likely role in transfusion when leucodepletion cannot be performed or is only partially achieved.

C-reactive protein enhances murine antibody-mediated transfusion-related acute lung injury

Transfusion-related acute lung injury (TRALI) is a syndrome of respiratory distress triggered by blood transfusions and is the leading cause of transfusion-related mortality. TRALI has primarily been attributed to passive infusion of HLA and/or human neutrophil antigen antibodies present in transfused blood products, and predisposing factors such as inflammation are known to be important for TRALI initiation. Because the acute-phase protein C-reactive protein (CRP) is highly upregulated during infections and inflammation and can also enhance antibody-mediated responses such as in vitro phagocytosis, respiratory burst, and in vivo thrombocytopenia, we investigated whether CRP affects murine antibody-mediated TRALI induced by the anti-major histocompatibility complex antibody 34-1-2s. We found that BALB/c mice injected with 34-1-2s or CRP alone were resistant to TRALI, however mice injected with 34-1-2s together with CRP had significantly enhanced lung damage and pulmonary edema. Mechanistically, 34-1-2s injection with CRP resulted in a significant synergistic increase in plasma levels of the neutrophil chemoattractant macrophage inflammatory protein-2 (MIP-2) and pulmonary neutrophil accumulation. Importantly, murine MIP-2 is the functional homolog of human interleukin-8, a known risk factor for human TRALI. These results suggest that elevated in vivo CRP levels, like those observed during infections, may significantly predispose recipients to antibody-mediated TRALI reactions and support the notion that modulating CRP levels is an effective therapeutic strategy to reduce TRALI severity.

High salt primes a specific activation state of macrophages, M(Na)

High salt is positively associated with the risk of many diseases. However, little is known about the mechanisms. Here we showed that high salt increased proinflammatory molecules, while decreased anti-inflammatory and proendocytic molecules in both human and mouse macrophages. High salt also potentiated lipopolysaccharide-induced macrophage activation and suppressed interleukin 4-induced macrophage activation. High salt induced the proinflammatory aspects by activating p38/cFos and/or Erk1/2/cFos pathways, while inhibited the anti-inflammatory and proendocytic aspects by Erk1/2/signal transducer and activator of transcription 6 pathway. Consistent with the in vitro results, high-salt diet increased proinflammatory gene expression of mouse alveolar macrophages. In mouse models of acute lung injury, high-salt diet aggravated lipopolysaccharide-induced pulmonary macrophage activation and inflammation in lungs. These results identify a novel macrophage activation state, M(Na), and high salt as a potential environmental risk factor for lung inflammation through the induction of M(Na).