Proinflammatory cytokines driving cardiotoxicity in COVID-19.

AIMS: Cardiac involvement is common in patients hospitalized with COVID-19 and correlates with an adverse disease trajectory. While cardiac injury has been attributed to direct viral cytotoxicity, serum-induced cardiotoxicity secondary to serological hyperinflammation constitutes a potentially amenable mechanism that remains largely unexplored. METHODS AND RESULTS: To investigate serological drivers of cardiotoxicity in COVID-19 we have established a robust bioassay that assessed the effects of serum from COVID-19 confirmed patients on human embryonic stem cell (hESC)-derived cardiomyocytes. We demonstrate that serum from COVID-19 positive patients significantly reduced cardiomyocyte viability independent of viral transduction, an effect that was also seen in non-COVID-19 acute respiratory distress syndrome (ARDS). Serum from patients with greater disease severity led to worse cardiomyocyte viability and this significantly correlated with levels of key inflammatory cytokines, including IL-6, TNF-α, IL1-ß, IL-10, CRP, and neutrophil to lymphocyte ratio with a specific reduction of CD4+ and CD8+ cells. Combinatorial blockade of IL-6 and TNF-α partly rescued the phenotype and preserved cardiomyocyte viability and function. Bulk RNA sequencing of serum-treated cardiomyocytes elucidated specific pathways involved in the COVID-19 response impacting cardiomyocyte viability, structure, and function. The observed effects of serum-induced cytotoxicity were cell-type selective as serum exposure did not adversely affect microvascular endothelial cell viability but resulted in endothelial activation and a procoagulant state. CONCLUSION: These results provide direct evidence that inflammatory cytokines are at least in part responsible for the cardiovascular damage seen in COVID-19 and characterise the downstream activated pathways in human cardiomyocytes. The serum signature of patients with severe disease indicates possible targets for therapeutic intervention.

Therapeutic potential of IL6R blockade for the treatment of sepsis and sepsis-related death: A Mendelian randomisation study.

BACKGROUND: Sepsis is characterised by dysregulated, life-threatening immune responses, which are thought to be driven by cytokines such as interleukin 6 (IL-6). Genetic variants in IL6R known to down-regulate IL-6 signalling are associated with improved Coronavirus Disease 2019 (COVID-19) outcomes, a finding later confirmed in randomised trials of IL-6 receptor antagonists (IL6RAs). We hypothesised that blockade of IL6R could also improve outcomes in sepsis. METHODS AND FINDINGS: We performed a Mendelian randomisation (MR) analysis using single nucleotide polymorphisms (SNPs) in and near IL6R to evaluate the likely causal effects of IL6R blockade on sepsis (primary outcome), sepsis severity, other infections, and COVID-19 (secondary outcomes). We weighted SNPs by their effect on CRP and combined results across them in inverse variance weighted meta-analysis, proxying the effect of IL6RA. Our outcomes were measured in UK Biobank, FinnGen, the COVID-19 Host Genetics Initiative (HGI), and the GenOSept and GainS consortium. We performed several sensitivity analyses to test assumptions of our methods, including utilising variants around CRP and gp130 in a similar analysis. In the UK Biobank cohort (N = 486,484, including 11,643 with sepsis), IL6R blockade was associated with a decreased risk of our primary outcome, sepsis (odds ratio (OR) = 0.80; 95% confidence interval (CI) 0.66 to 0.96, per unit of natural log-transformed CRP decrease). The size of this effect increased with severity, with larger effects on 28-day sepsis mortality (OR = 0.74; 95% CI 0.47 to 1.15); critical care admission with sepsis (OR = 0.48, 95% CI 0.30 to 0.78) and critical care death with sepsis (OR = 0.37, 95% CI 0.14 to 0.98). Similar associations were seen with severe respiratory infection: OR for pneumonia in critical care 0.69 (95% CI 0.49 to 0.97) and for sepsis survival in critical care (OR = 0.22; 95% CI 0.04 to 1.31) in the GainS and GenOSept consortium, although this result had a large degree of imprecision. We also confirm the previously reported protective effect of IL6R blockade on severe COVID-19 (OR = 0.69, 95% CI 0.57 to 0.84) in the COVID-19 HGI, which was of similar magnitude to that seen in sepsis. Sensitivity analyses did not alter our primary results. These results are subject to the limitations and assumptions of MR, which in this case reflects interpretation of these SNP effects as causally acting through blockade of IL6R, and reflect lifetime exposure to IL6R blockade, rather than the effect of therapeutic IL6R blockade. CONCLUSIONS: IL6R blockade is causally associated with reduced incidence of sepsis. Similar but imprecisely estimated results supported a causal effect also on sepsis related mortality and critical care admission with sepsis. These effects are comparable in size to the effect seen in severe COVID-19, where IL-6 receptor antagonists were shown to improve survival. These data suggest that a randomised trial of IL-6 receptor antagonists in sepsis should be considered.

A randomised trial of anti-GM-CSF otilimab in severe COVID-19 pneumonia (OSCAR).

BACKGROUND: Granulocyte-macrophage colony-stimulating factor (GM-CSF) and dysregulated myeloid cell responses are implicated in the pathophysiology and severity of COVID-19. METHODS: In this randomised, sequential, multicentre, placebo-controlled, double-blind study, adults aged 18-79 years (Part 1) or ≥70 years (Part 2) with severe COVID-19, respiratory failure and systemic inflammation (elevated C-reactive protein/ferritin) received a single intravenous infusion of otilimab 90 mg (human anti-GM-CSF monoclonal antibody) plus standard care (NCT04376684). The primary outcome was the proportion of patients alive and free of respiratory failure at Day 28. RESULTS: In Part 1 (n=806 randomised 1:1 otilimab:placebo), 71% of otilimab-treated patients were alive and free of respiratory failure at Day 28 versus 67% who received placebo; the model-adjusted difference of 5.3% was not statistically significant (95% CI -0.8-11.4%, p=0.09). A nominally significant model-adjusted difference of 19.1% (95% CI 5.2-33.1%, p=0.009) was observed in the predefined 70-79 years subgroup, but this was not confirmed in Part 2 (n=350 randomised) where the model-adjusted difference was 0.9% (95% CI -9.3-11.2%, p=0.86). Compared with placebo, otilimab resulted in lower serum concentrations of key inflammatory markers, including the putative pharmacodynamic biomarker CC chemokine ligand 17, indicative of GM-CSF pathway blockade. Adverse events were comparable between groups and consistent with severe COVID-19. CONCLUSIONS: There was no significant difference in the proportion of patients alive and free of respiratory failure at Day 28. However, despite the lack of clinical benefit, a reduction in inflammatory markers was observed with otilimab, in addition to an acceptable safety profile.

A web-based survey assessing perceived changes in diet, physical activity and sleeping behaviours in adults with type 1 and type 2 diabetes during the COVID-19 pandemic in the UK.

Background: The COVID-19 pandemic may have contributed to poorer self-management (ie, diet, physical activity and sleep) of diabetes mellitus (DM), which might predispose individuals to more severe COVID-19 outcomes. Objective: The first objective was to capture perceived changes in diet, physical activity and sleeping during the COVID-19 pandemic in adults with type 1 (T1DM) and type 2 diabetes mellitus (T2DM) in the UK. A second objective was to explore differences between individuals with DM compared with 'no' or 'other' health conditions. Methods: Participants aged >18 years were selected by convenience. Individuals subscribed to the Diabetes.co.uk community were sent a web-based survey including questions about demographics and health, followed by 5-point Likert-type scale questions relating to lifestyle-related behaviours during the COVID-19 pandemic. Individuals were grouped by diagnosis of DM, 'other' or 'no' health condition and responses were compared. Results: 4764 individuals responded, with 2434 (51.3%) being female and 1550 (32.6%) aged 55-64 years. T2DM (2974; 62.7%), hypertension (2147; 45.2%) and T1DM (1299; 27.4%) were most frequently reported. Compared with T1DM, 'no' or 'other' health conditions, respondents with T2DM reported making a less conscious effort to get outside and exercise daily (p<0.001) and spending no time outdoors (p=0.001). Weight loss was more frequently reported in respondents with T2DM (p=0.005). More individuals with T2DM reported consuming convenience foods (p=0.012) and sugary foods (p=0.021), yet eating more fresh foods (p=0.001) and drinking less alcohol than normal (p<0.001). More individuals with T1DM and T2DM reported worse sleep quality (p=0.004). Conclusions: Our study highlighted important differences in lifestyle by individuals with T1DM, T2DM, other and no health conditions in relation to the COVID-19 pandemic. Establishing surveillance systems and conducting repeated assessments are required to analyse how the situation shifted over time and whether adverse collateral effects of the pandemic were sustained in those with chronic health conditions.

Lesson of the month: novel method to quantify neutrophil uptake in early lung cancer using SPECT-CT.

Neutrophils play an important role in the lung tumour microenvironment. We hypothesised that radiolabelled neutrophils coupled to single-photon emission CT (SPECT) may non-invasively quantify neutrophil uptake in tumours from patients with non-small cell lung cancer. We demonstrated increased uptake of radiolabelled neutrophils from the blood into tumours compared with non-specific uptake using radiolabelled transferrin. Moreover, indium-111-neutrophil activity in the tumour biopsies also correlated with myeloperoxidase (MPO)-positive neutrophils. Our data support the utility of imaging with In-111-labelled neutrophils and SPECT-CT to quantify neutrophil uptake in lung cancer.

Therapeutic blockade of granulocyte macrophage colony-stimulating factor in COVID-19-associated hyperinflammation: challenges and opportunities.

The COVID-19 pandemic is a global public health crisis, with considerable mortality and morbidity exerting pressure on health-care resources, including critical care. An excessive host inflammatory response in a subgroup of patients with severe COVID-19 might contribute to the development of acute respiratory distress syndrome (ARDS) and multiorgan failure. Timely therapeutic intervention with immunomodulation in patients with hyperinflammation could prevent disease progression to ARDS and obviate the need for invasive ventilation. Granulocyte macrophage colony-stimulating factor (GM-CSF) is an immunoregulatory cytokine with a pivotal role in initiation and perpetuation of inflammatory diseases. GM-CSF could link T-cell-driven acute pulmonary inflammation with an autocrine, self-amplifying cytokine loop leading to monocyte and macrophage activation. This axis has been targeted in cytokine storm syndromes and chronic inflammatory disorders. Here, we consider the scientific rationale for therapeutic targeting of GM-CSF in COVID-19-associated hyperinflammation. Since GM-CSF also has a key role in homoeostasis and host defence, we discuss potential risks associated with inhibition of GM-CSF in the context of viral infection and the challenges of doing clinical trials in this setting, highlighting in particular the need for a patient risk-stratification algorithm.

A nebulised antitumour necrosis factor receptor-1 domain antibody in patients at risk of postoperative lung injury: A randomised, placebo-controlled pilot study.

BACKGROUND: Tumour necrosis factor receptor 1 (TNFR1) signalling mediates the cell death and inflammatory effects of TNF-α. OBJECTIVE: The current clinical trial investigated the effects of a nebulised TNFR1 antagonist (GSK2862277) on signs of lung injury in patients undergoing oesophagectomy. DESIGN: Randomised double-blind (sponsor unblind), placebo-controlled, parallel group study. SETTING: Eight secondary care centres, the United Kingdom between April 2015 and June 2017. PATIENTS: Thirty-three patients undergoing elective transthoracic oesophagectomy. INTERVENTIONS: Patients randomly received a single nebulised dose (26 mg) of GSK2862277 (n = 17) or placebo (n = 16), given 1 to 5 h before surgery; 14 and 16, respectively competed the study. MAIN OUTCOME MEASUREMENTS: Physiological and biochemical markers of lung injury, pharmacokinetic and safety endpoints were measured. The primary endpoint was the change from baseline in pulmonary vascular permeability index (PVPI) at completion of surgery, measured using single-indicator transpulmonary thermodilution. Adjusted point estimates and 95% credible intervals (analogous to conventional confidence intervals) were constructed for each treatment using Bayesian statistical models. RESULTS: The mean change (with 95% credible intervals) from baseline in PVPI on completion of surgery was 0.00 (-0.23, 0.39) in the placebo and 0.00 (-0.24, 0.37) in the GSK2862277 treatment groups. There were no significant treatment-related differences in PaO2/FiO2 or Sequential Organ Failure Assessment score. Levels of free soluble TNFR1, Macrophage Inflammatory Protein-1 alpha and total protein were significantly reduced in the bronchoalveolar lavage fluid of patients treated with GSK2862277 (posterior probability of decrease with GSK2862277 vs. placebo:≥0.977; equivalent to P < 0.05). The frequency of adverse events and serious adverse events were distributed evenly across the two treatment arms. CONCLUSION: Pre-operative treatment with a single 26 mg inhaled dose of GSK2862277 did not result in significantly lower postoperative alveolar capillary leak or extra vascular lung water. Unexpectedly small increases in transpulmonary thermodilution-measured PVPI and extra vascular lung water index at completion of surgery suggest less postoperative lung injury than historically reported, which may have also compromised a clear assessment of efficacy in this trial. GSK2862277 was well tolerated, resulted in expected lung exposure and reduced biomarkers of lung permeability and inflammation. TRIAL REGISTRATION: clinicaltrials.gov: NCT02221037.

Effect of the CXCR4 antagonist plerixafor on endogenous neutrophil dynamics in the bone marrow, lung and spleen.

Treatment with the CXCR4 antagonist, plerixafor (AMD3100), has been proposed for clinical use in patients with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome and in pulmonary fibrosis. However, there is controversy with respect to the impact of plerixafor on neutrophil dynamics in the lung, which may affect its safety profile. In this study, we investigated the kinetics of endogenous neutrophils by direct imaging, using confocal intravital microscopy in mouse bone marrow, spleen, and lungs. Neutrophils are observed increasing their velocity and exiting the bone marrow following plerixafor administration, with a concomitant increase in neutrophil numbers in the blood and spleen, while the marginated pool of neutrophils in the lung microvasculature remained unchanged in terms of numbers and cell velocity. Use of autologous radiolabeled neutrophils and SPECT/CT imaging in healthy volunteers showed that plerixafor did not affect GM-CSF-primed neutrophil entrapment or release in the lungs. Taken together, these data suggest that plerixafor causes neutrophil mobilization from the bone marrow but does not impact on lung marginated neutrophil dynamics and thus is unlikely to compromise respiratory host defense both in humans and mice.

The mechanics of myeloid cells.

The effects of cell size, shape and deformability on cellular function have long been a topic of interest. Recently, mechanical phenotyping technologies capable of analysing large numbers of cells in real time have become available. This has important implications for biology and medicine, especially haemato-oncology and immunology, as immune cell mechanical phenotyping, immunologic function, and malignant cell transformation are closely linked and potentially exploitable to develop new diagnostics and therapeutics. In this review, we introduce the technologies used to analyse cellular mechanical properties and review emerging findings following the advent of high throughput deformability cytometry. We largely focus on cells from the myeloid lineage, which are derived from the bone marrow and include macrophages, granulocytes and erythrocytes. We highlight advances in mechanical phenotyping of cells in suspension that are revealing novel signatures of human blood diseases and providing new insights into pathogenesis of these diseases. The contributions of mechanical phenotyping of cells in suspension to our understanding of drug mechanisms, identification of novel therapeutics and monitoring of treatment efficacy particularly in instances of haematologic diseases are reviewed, and we suggest emerging topics of study to explore as high throughput deformability cytometers become prevalent in laboratories across the globe.

The Neutrophil Life Cycle.

Neutrophils are recognized as an essential part of the innate immune response, but an active debate still exists regarding the life cycle of these cells. Neutrophils first differentiate in the bone marrow through progenitor intermediaries before entering the blood, in a process that gauges the extramedullary pool size. Once believed to be directly eliminated in the marrow, liver, and spleen, neutrophils, after circulating for less than 1 day, are now known to redistribute into multiple tissues with poorly understood kinetics. In this review, we provide an update on the dynamic distribution of neutrophils across tissues in health and disease, and emphasize differences between humans and model organisms. We further highlight issues to be addressed to exploit the unique features of neutrophils in the clinic.

The Coagulation and Immune Systems Are Directly Linked through the Activation of Interleukin-1α by Thrombin.

Ancient organisms have a combined coagulation and immune system, and although links between inflammation and hemostasis exist in mammals, they are indirect and slower to act. Here we investigated direct links between mammalian immune and coagulation systems by examining cytokine proproteins for potential thrombin protease consensus sites. We found that interleukin (IL)-1α is directly activated by thrombin. Thrombin cleaved pro-IL-1α at a site perfectly conserved across disparate species, indicating functional importance. Surface pro-IL-1α on macrophages and activated platelets was cleaved and activated by thrombin, while tissue factor, a potent thrombin activator, colocalized with pro-IL-1α in the epidermis. Mice bearing a mutation in the IL-1α thrombin cleavage site (R114Q) exhibited defects in efficient wound healing and rapid thrombopoiesis after acute platelet loss. Thrombin-cleaved IL-1α was detected in humans during sepsis, pointing to the relevance of this pathway for normal physiology and the pathogenesis of inflammatory and thrombotic diseases.

Major surgery and the immune system: from pathophysiology to treatment.

PURPOSE OF REVIEW: The purpose of this review is to provide an overview of the immune response to major surgery, and the ways in which it may be modulated to improve postoperative outcomes. RECENT FINDINGS: Data from patients who have undergone a variety of tissue injuries (surgery, burns, sepsis, trauma) have shown the presence of a conserved 'genomic storm' that alters the leukocyte transcriptome, with upregulation of the innate immune response and concomitant downregulation of the adaptive immune response. The innate and adaptive immune systems are often regarded largely distinct. However, more recent evidence suggests there are critical connections between the two arms of the immune response, whereby innate immune cells are able to suppress the adaptive response. SUMMARY: The immune system is critical to the host response to tissue injury occurring due to surgery. However, the physiological processes required to resolve the surgical insult can also contribute to sequelae such as cognitive decline, pneumonia and acute kidney injury. Our understanding of the immune pathogenesis underlying these complications is improving, leading to interest in the development of immunomodulatory therapies, which aim to permit host defence whilst ameliorating postoperative complications.

Definitions and pathophysiology of vasoplegic shock.

Vasoplegia is the syndrome of pathological low systemic vascular resistance, the dominant clinical feature of which is reduced blood pressure in the presence of a normal or raised cardiac output. The vasoplegic syndrome is encountered in many clinical scenarios, including septic shock, post-cardiac bypass and after surgery, burns and trauma, but despite this, uniform clinical definitions are lacking, which renders translational research in this area challenging. We discuss the role of vasoplegia in these contexts and the criteria that are used to describe it are discussed. Intrinsic processes which may drive vasoplegia, such as nitric oxide, prostanoids, endothelin-1, hydrogen sulphide and reactive oxygen species production, are reviewed and potential for therapeutic intervention explored. Extrinsic drivers, including those mediated by glucocorticoid, catecholamine and vasopressin responsiveness of the blood vessels, are also discussed. The optimum balance between maintaining adequate systemic vascular resistance against the potentially deleterious effects of treatment with catecholamines is as yet unclear, but development of novel vasoactive agents may facilitate greater understanding of the role of the differing pathways in the development of vasoplegia. In turn, this may provide insights into the best way to care for patients with this common, multifactorial condition.

Novel anti-tumour necrosis factor receptor-1 (TNFR1) domain antibody prevents pulmonary inflammation in experimental acute lung injury.

BACKGROUND: Tumour necrosis factor alpha (TNF-α) is a pleiotropic cytokine with both injurious and protective functions, which are thought to diverge at the level of its two cell surface receptors, TNFR1 and TNFR2. In the setting of acute injury, selective inhibition of TNFR1 is predicted to attenuate the cell death and inflammation associated with TNF-α, while sparing or potentiating the protective effects of TNFR2 signalling. We developed a potent and selective antagonist of TNFR1 (GSK1995057) using a novel domain antibody (dAb) therapeutic and assessed its efficacy in vitro, in vivo and in a clinical trial involving healthy human subjects. METHODS: We investigated the in vitro effects of GSK1995057 on human pulmonary microvascular endothelial cells (HMVEC-L) and then assessed the effects of pretreatment with nebulised GSK1995057 in a non-human primate model of acute lung injury. We then tested translation to humans by investigating the effects of a single nebulised dose of GSK1995057 in healthy humans (n=37) in a randomised controlled clinical trial in which subjects were subsequently exposed to inhaled endotoxin. RESULTS: Selective inhibition of TNFR1 signalling potently inhibited cytokine and neutrophil adhesion molecule expression in activated HMVEC-L monolayers in vitro (P<0.01 and P<0.001, respectively), and also significantly attenuated inflammation and signs of lung injury in non-human primates (P<0.01 in all cases). In a randomised, placebo-controlled trial of nebulised GSK1995057 in 37 healthy humans challenged with a low dose of inhaled endotoxin, treatment with GSK1995057 attenuated pulmonary neutrophilia, inflammatory cytokine release (P<0.01 in all cases) and signs of endothelial injury (P<0.05) in bronchoalveolar lavage and serum samples. CONCLUSION: These data support the potential for pulmonary delivery of a selective TNFR1 dAb as a novel therapeutic approach for the prevention of acute respiratory distress syndrome. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov NCT01587807.

Hypoxia upregulates neutrophil degranulation and potential for tissue injury.

BACKGROUND: The inflamed bronchial mucosal surface is a profoundly hypoxic environment. Neutrophilic airway inflammation and neutrophil-derived proteases have been linked to disease progression in conditions such as COPD and cystic fibrosis, but the effects of hypoxia on potentially harmful neutrophil functional responses such as degranulation are unknown. METHODS AND RESULTS: Following exposure to hypoxia (0.8% oxygen, 3 kPa for 4 h), neutrophils stimulated with inflammatory agonists (granulocyte-macrophage colony stimulating factor or platelet-activating factor and formylated peptide) displayed a markedly augmented (twofold to sixfold) release of azurophilic (neutrophil elastase, myeloperoxidase), specific (lactoferrin) and gelatinase (matrix metalloproteinase-9) granule contents. Neutrophil supernatants derived under hypoxic but not normoxic conditions induced extensive airway epithelial cell detachment and death, which was prevented by coincubation with the antiprotease α-1 antitrypsin; both normoxic and hypoxic supernatants impaired ciliary function. Surprisingly, the hypoxic upregulation of neutrophil degranulation was not dependent on hypoxia-inducible factor (HIF), nor was it fully reversed by inhibition of phospholipase C signalling. Hypoxia augmented the resting and cytokine-stimulated phosphorylation of AKT, and inhibition of phosphoinositide 3-kinase (PI3K)γ (but not other PI3K isoforms) prevented the hypoxic upregulation of neutrophil elastase release. CONCLUSION: Hypoxia augments neutrophil degranulation and confers enhanced potential for damage to respiratory airway epithelial cells in a HIF-independent but PI3Kγ-dependent fashion.

Genome-wide transcription profiling in neutrophils in acute respiratory distress syndrome.

BACKGROUND: Acute respiratory distress syndrome (ARDS) is characterised by diffuse neutrophil-mediated alveolar inflammation. Recently, we demonstrated that blood polymorphonuclear leucocytes (PMNs) in ARDS are basally activated, and exhibit aberrant oxidative burst and survival responses. The molecular mechanisms governing ARDS PMN function and longevity are incompletely understood. We aimed to use genome-wide transcriptional profiling of ARDS blood PMNs to explore underlying disease mechanisms and identify therapeutic targets aimed at manipulating PMN function and longevity. METHODS: GeneChip Affymetrix oligonucleotide arrays were used to assess global transcriptional profiles in highly pure PMNs from ventilated patients fulfilling the Berlin ARDS definition (n=10), in freshly isolated PMNs from age-matched and sex-matched healthy volunteers (n=10), and in healthy volunteer PMNs exposed in vitro to recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) (1 ng/mL for 6 h). Ingenuity Pathway Analysis software was used to map probes identified as important onto specific pathways. FINDINGS: Transcriptomic analysis showed that 1319 genes were altered in ARDS PMNs relative to healthy volunteer PMNs. Compared with well established reference databases, the gene expression profile in ARDS PMNs showed near-complete correlation to datasets derived from patients with sepsis and burns. Transcripts enriched in ARDS PMNs were differentially expressed in known functional network pathways associated with cancer, cellular compromise, apoptotic mechanisms, and chemotaxis. Of the observed gene changes, only 292 (22%) were seen in healthy volunteer PMNs after exposure to rhGM-CSF, of which 216 showed the same directional change as ARDS PMNs. INTERPRETATION: Existing genome-wide studies in ARDS use total blood leucocytes; our study is the first, to our knowledge, to use unbiased global genomic profiling of highly pure ARDS blood PMNs in parallel with age-matched and gender-matched healthy volunteer PMNs treated with rhGM-CSF. Collectively our results show that ARDS PMNs display important de-novo transcriptional activity. The global transcriptomic changes were consistent with the observed aberrant ARDS PMN survival and functional phenotype that we have previously reported, and show near-complete correlation to existing sepsis and burns datasets, but only limited transcriptomic overlap with healthy volunteer PMNs treated with rhGM-CSF. FUNDING: National Institute for Health Research, GlaxoSmithKline.

Pulmonary retention of primed neutrophils: a novel protective host response, which is impaired in the acute respiratory distress syndrome.

RATIONALE: Acute respiratory distress syndrome (ARDS) affects over 200000 people annually in the USA. Despite causing severe, and often refractory, hypoxaemia, the high mortality and long-term morbidity of ARDS results mainly from extra-pulmonary organ failure; however the mechanism for this organ crosstalk has not been determined. METHODS: Using autologous radiolabelled neutrophils we investigated the pulmonary transit of primed and unprimed neutrophils in humans. Flow cytometry of whole blood samples was used to assess transpulmonary neutrophil priming gradients in patients with ARDS, sepsis and perioperative controls. MAIN RESULTS: Unprimed neutrophils passed through the lungs with a transit time of 14.2 s, only 2.3 s slower than erythrocytes, and with <5% first-pass retention. Over 97% of neutrophils primed ex vivo with granulocyte macrophage colony-stimulating factor were retained on first pass, with 48% still remaining in the lungs at 40 min. Neutrophils exposed to platelet-activating factor were initially retained but subsequently released such that only 14% remained in the lungs at 40 min. Significant transpulmonary gradients of neutrophil CD62L cell surface expression were observed in ARDS compared with perioperative controls and patients with sepsis. CONCLUSIONS: We demonstrated minimal delay and retention of unprimed neutrophils transiting the healthy human pulmonary vasculature, but marked retention of primed neutrophils; these latter cells then 'deprime' and are re-released into the systemic circulation. Further, we show that this physiological depriming mechanism may fail in patients with ARDS, resulting in increased numbers of primed neutrophils within the systemic circulation. This identifies a potential mechanism for the remote organ damage observed in patients with ARDS.

Quantification of neutrophil migration into the lungs of patients with chronic obstructive pulmonary disease.

OBJECTIVE: To quantify neutrophil migration into the lungs of patients with chronic pulmonary obstructive disease (COPD). METHODS: Neutrophil loss via airways was assessed by dedicated whole-body counting 45 min, 24 h and 2, 4, 7 and 10 days after injection of very small activities of (111)In-labelled neutrophils in 12 healthy nonsmokers, 5 healthy smokers, 16 patients with COPD (of whom 7 were ex-smokers) and 10 patients with bronchiectasis. Lung accumulation of (99m)Tc-labelled neutrophils was assessed by sequential SPECT and Patlak analysis in six COPD patients and three healthy nonsmoking subjects. RESULTS: Whole body (111)In counts, expressed as percentages of 24 h counts, decreased in all subjects. Losses at 7 days (mean ± SD) were similar in healthy nonsmoking subjects (5.5 ± 1.5%), smoking subjects (6.5 ± 4.4%) and ex-smoking COPD patients (5.8 ± 1.5%). In contrast, currently smoking COPD patients showed higher losses (8.0 ± 3.0%) than healthy nonsmokers (p = 0.03). Two bronchiectatic patients lost 25% and 26%, indicating active disease; mean loss in the remaining eight was 6.9 ± 2.5%. The rate of accumulation of (99m)Tc-neutrophils in the lungs, determined by sequential SPECT, was increased in COPD patients (0.030-0.073 min(-1)) compared with healthy nonsmokers (0-0.002 min(-1); p = 0.02). CONCLUSION: In patients with COPD, sequential SPECT showed increased lung accumulation of (99m)Tc-labelled neutrophils, while whole-body counting demonstrated subsequent higher losses of (111)In-labelled neutrophils in patients who continued to smoke. Sequential SPECT as a means of quantifying neutrophil migration deserves further evaluation.

Granulocyte/macrophage colony-stimulating factor causes a paradoxical increase in the BH3-only pro-apoptotic protein Bim in human neutrophils.

Neutrophil apoptosis is essential for the resolution of inflammation but is delayed by several inflammatory mediators. In such terminally differentiated cells it has been uncertain whether these agents can inhibit apoptosis through transcriptional regulation of anti-death (Bcl-X(L), Mcl-1, Bcl2A1) or BH3-only (Bim, Bid, Puma) Bcl2-family proteins. We report that granulocyte/macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-α prevent the normal time-dependent loss of Mcl-1 and Bcl2A1 in neutrophils, and we demonstrate that they cause an NF-κB-dependent increase in Bcl-X(L) transcription/translation. We show that GM-CSF and TNF-α increase and/or maintain mRNA levels for the pro-apoptotic BH3-only protein Bid and that GM-CSF has a similar NF-κB-dependent effect on Bim transcription and BimEL expression. The in-vivo relevance of these findings was indicated by demonstrating that GM-CSF is the dominant neutrophil survival factor in lung lavage from patients with ventilator-associated pneumonia, confirming an increase in lung neutrophil Bim mRNA. Finally GM-CSF caused mitochondrial location of Bim and a switch in phenotype to a cell that displays accelerated caspase-9-dependent apoptosis. This study demonstrates the capacity of neutrophil survival agents to induce a paradoxical increase in the pro-apoptotic proteins Bid and Bim and suggests that this may function to facilitate rapid apoptosis at the termination of the inflammatory cycle.

Measuring whole-body neutrophil redistribution using a dedicated whole-body counter and ultra-low doses of 111Indium.

BACKGROUND: There is increasing interest in the 'homing' of neutrophils to bone marrow. The aim of this study was to measure the whole-body redistribution of (111) In using a whole-body counter following the administration of ultra-small activities of (111) In-labelled neutrophils. METHODS: The detectors of a dedicated whole-body counter were fitted with lead collimators. Whole-body (111) In distribution was recorded at 45 min, 24 h, and 2, 4, 7 and 10 days after administration of (111) In-labelled neutrophils (0·29-0·74 MBq) in eight healthy non-smokers, five healthy smokers, eight patients with inactive bronchiectasis, three with asthma and nine with chronic obstructive pulmonary disease (COPD). RESULTS: Intravascular 45-min (111) In-labelled neutrophil recovery was not significantly different between groups, ranging from 33 (SD 8%) in healthy smokers to 45 (14%) in healthy non-smokers (P > 0·05). Peaks were identified on the whole body count profile corresponding to the chest, upper abdomen (liver/spleen) and pelvis (bone marrow). (111) In distribution changed between 45 min and 24 h and then remained stable thereafter. Peak chest counts increased ∼ 1·5-fold between 45 min and 24 h, whereas upper abdominal peak counts decreased by ∼ 25% with no significant inter-group differences. The increment in pelvic counts (∼ 2·7-fold) was similar between groups, except COPD patients, in whom it was 2·04 (0·35; P < 0·02 vs. healthy participants). CONCLUSIONS: Assuming neutrophils are distributed only between blood, liver, spleen and bone marrow, the data suggest that marrow pools 25% and destroys 67% of circulating neutrophils, rising in COPD to 40% and 80%, respectively, possibly as a result of the effects on marrow of chronic hypoxaemia.