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

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.

Outcomes Associated With Early RBC Transfusion in Pediatric Severe Sepsis: A Propensity-Adjusted Multicenter Cohort Study

BACKGROUND

Little is known about the epidemiology of and outcomes related to red blood cell (RBC) transfusion in septic children across multiple centers. We performed propensity-adjusted secondary analyses of the Biomarker Phenotyping of Pediatric Sepsis and Multiple Organ Failure (PHENOMS) study to test the hypothesis that early RBC transfusion is associated with fewer organ failure-free days in pediatric severe sepsis.

METHODS

Four hundred one children were enrolled in the parent study. Children were excluded from these analyses if they received extracorporeal membrane oxygenation (n = 22) or died (n = 1) before sepsis day 2. Propensity-adjusted analyses compared children who received RBC transfusion on or before sepsis day 2 (early RBC transfusion) with those who did not. Logistic regression was used to model the propensity to receive early RBC transfusion. A weighted cohort was constructed using stabilized inverse probability of treatment weights. Variables in the weighted cohort with absolute standardized differences >0.15 were added to final multivariable models.

RESULTS

Fifty percent of children received at least one RBC transfusion. The majority (68%) of first transfusions were on or before sepsis day 2. Early RBC transfusion was not independently associated with organ failure-free (-0.34 [95%CI: -2, 1.3] days) or PICU-free days (-0.63 [-2.3, 1.1]), but was associated with the secondary outcome of higher mortality (aOR 2.9 [1.1, 7.9]).

CONCLUSIONS

RBC transfusion is common in pediatric severe sepsis and may be associated with adverse outcomes. Future studies are needed to clarify these associations, to understand patient-specific transfusion risks, and to develop more precise transfusion strategies.

The Lipid Composition of Platelets and the Impact of Storage: An Overview

Lipids and bioactive lipid mediators are essential for platelet function. The lipid profile of platelets is highly dynamic due to free exchange of lipids with the plasma, release of extracellular vesicles, and both enzymatic and nonenzymatic lipid conversion. The lipidome of platelets changes in response to activation to accommodate the functional requirements of platelets, particularly for maintenance of hemostasis. Furthermore, when stored at room temperature as a component for transfusion, the lipid profile of platelets is altered. Although there is a growing interest in alternate storage conditions, such as refrigeration and cryopreservation, few contemporary studies have examined the impact of these storage modes on the lipid profile. However, evidence exists that bioactive lipid mediators produced over the storage of blood products may have functional implications once these products are transfused. As such, there is a need to determine the changes occurring to the lipid profile of these products over storage. This review outlines the role of lipids in platelets and discusses the current state of lipidomics for studying platelet components for transfusion in an effort to highlight the necessity for additional transfusion-focused investigations.

Contrasting effects of stored allogeneic red blood cells and their supernatants on permeability and inflammatory responses in human pulmonary endothelial cells

Transfusion of red blood cells (RBCs) is a common life-saving clinical practice in severely anemic or hemorrhagic patients; however, it may result in serious pathological complications such as transfusion-related acute lung injury. The factors mediating the deleterious effects of RBC transfusion remain unclear. In this study, we tested the effects of washed long-term (RBC-O; >28 days) versus short-term (RBC-F; <14 days) stored RBCs and their supernatants on lung endothelial (EC) permeability under control and inflammatory conditions. RBCs enhanced basal EC barrier function as evidenced by an increase in transendothelial electrical resistance and decrease in permeability for macromolecules. RBCs also attenuated EC hyperpermeability and suppressed secretion of EC adhesion molecule ICAM-1 and proinflammatory cytokine IL-8 in response to LPS or TNF-α. In both settings, RBC-F had slightly higher barrier protective effects as compared with RBC-O. In contrast, supernatants from both RBC-F and RBC-O disrupted the EC barrier. The early phase of EC permeability response caused by RBC supernatants was partially suppressed by antioxidant N-acetyl cysteine and inhibitor of Src kinase family PP2, while addition of heme blocker and inhibition of NOD-like receptor family pyrin domain containing protein 3 (NLRP3), stress MAP kinases, receptor for advanced glycation end-products (RAGE), or Toll-like receptor-4 (TLR4) signaling were without effect. Morphological analysis revealed that RBC supernatants increased LPS- and TNF-α-induced breakdown of intercellular junctions and formation of paracellular gaps. RBC supernatants augmented LPS- and TNF-α-induced EC inflammation reflected by increased production of IL-6, IL-8, and soluble ICAM-1. These findings demonstrate the deleterious effects of RBC supernatants on EC function, which may have a major impact in pathological consequences associated with RBC transfusion.

Risk factors, management and prevention of transfusion-related acute lung injury: a comprehensive update

Introduction: Despite mitigation strategies that include the exclusion of females from plasma donation or the exclusion of females with a history of pregnancy or known anti-leukocyte antibody, transfusion-related acute lung injury (TRALI) remains a leading cause of transfusion-related morbidity and mortality. Areas covered: The definition of TRALI is discussed and re-aligned with the new Berlin Diagnostic Criteria for the acute respiratory distress syndrome (ARDS). The risk factors associated with TRALI are summarized as are the mitigation strategies to further reduce TRALI. The emerging basic research studies that may translate to clinical therapeutics for the prevention or treatment of TRALI are discussed. Expert opinion: At risk patients, including the genetic factors that may predispose patients to TRALI are summarized and discussed. The re-definition of TRALI employing the Berlin Criteria for ARDS will allow for increased recognition and improved research into pathophysiology and mitigation to reduce this fatal complication of hemotherapy.

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.

From omics technologies to personalized transfusion medicine

INTRODUCTION

Blood transfusion is the single most frequent in-hospital medical procedure, a life-saving intervention for millions of recipients worldwide every year. Storage in the blood bank is an enabling strategy for this critical procedure, as it logistically solves the issue of making ~110 million units available for transfusion every year. Unfortunately, storage in the blood bank promotes a series of biochemical and morphological changes to the red blood cell that compromise the integrity and functionality of the erythrocyte in vitro and in animal models, and could negatively impact transfusion outcomes in the recipient. Areas covered: While commenting on the clinical relevance of the storage lesion is beyond the scope of this manuscript, here we will review recent advancements in our understanding of the storage lesion as gleaned through omics technologies. We will focus on how the omics-scale appreciation of the biological variability at the donor and recipient level is impacting our understanding of red blood cell storage biology. Expert commentary: Omics technologies are paving the way for personalized transfusion medicine, a discipline that promises to revolutionize a critical field in medical practice. The era of recipient-tailored additives, processing, and storage strategies may not be too far distant in the future.

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.

Red blood cell storage lesion: causes and potential clinical consequences

Red blood cells (RBCs) are a specialised organ that enabled the evolution of multicellular organisms by supplying a sufficient quantity of oxygen to cells that cannot obtain oxygen directly from ambient air via diffusion, thereby fueling oxidative phosphorylation for highly efficient energy production. RBCs have evolved to optimally serve this purpose by packing high concentrations of haemoglobin in their cytosol and shedding nuclei and other organelles. During their circulatory lifetimes in humans of approximately 120 days, RBCs are poised to transport oxygen by metabolic/redox enzymes until they accumulate damage and are promptly removed by the reticuloendothelial system. These elaborate evolutionary adaptions, however, are no longer effective when RBCs are removed from the circulation and stored hypothermically in blood banks, where they develop storage-induced damages ("storage lesions") that accumulate over the shelf life of stored RBCs. This review attempts to provide a comprehensive view of the literature on the subject of RBC storage lesions and their purported clinical consequences by incorporating the recent exponential growth in available data obtained from "omics" technologies in addition to that published in more traditional literature. To summarise this vast amount of information, the subject is organised in figures with four panels: i) root causes; ii) RBC storage lesions; iii) physiological effects; and iv) reported outcomes. The driving forces for the development of the storage lesions can be roughly classified into two root causes: i) metabolite accumulation/depletion, the target of various interventions (additive solutions) developed since the inception of blood banking; and ii) oxidative damages, which have been reported for decades but not addressed systemically until recently. Downstream physiological consequences of these storage lesions, derived mainly by in vitro studies, are described, and further potential links to clinical consequences are discussed. Interventions to postpone the onset and mitigate the extent of the storage lesion development are briefly reviewed. In addition, we briefly discuss the results from recent randomised controlled trials on the age of stored blood and clinical outcomes of transfusion.