Regulation of neutrophilic inflammation by hypoxic signalling pathways

Neutrophils are essential for effective innate immunity. Conversely, inappropriate or excessive neutrophil activation can result in damaging inflammation. This damage is implicated in the pathogenesis of a number of respiratory diseases including acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) which are also both frequently complicated by hypoxia. Cells sense and respond to hypoxia through the activity of the transcription factor HIF (hypoxia inducible factor) and its regulatory hydroxylases, the prolyl hydroxylase domain enzymes (PHDs) 1- 3. In the presence of oxygen, PHDs hydroxylate HIF, preventing the HIF mediated transcriptional response. Close links exist between the pathways which regulate hypoxic and inflammatory responses. Our group has previously found that in mouse models of infection, acute hypoxia leads to increased sickness and that this is driven by neutrophilic inflammation. I have used a murine model of Lipopolysaccharide (LPS) -induced acute lung injury, characterised by neutrophil influx, to investigate how exposure to hypoxia alters lung inflammation. Using high-resolution mass spectrometry, I have defined the proteome of the inflammatory lung neutrophil. I have shown that hypoxia results in a distinct proteomic signature in inflammatory neutrophils. Hypoxia drives lung neutrophilic inflammation through increased neutrophil degranulation and upregulation of inflammatory receptors. I have also identified key metabolic alterations in hypoxic neutrophils. The hypoxic lung represents a low glucose, high protein environment and neutrophils adapt to exploit this. I have shown that neutrophils can scavenge proteins from their extracellular environment, catabolise these proteins in the lysosome and utilise the breakdown products for metabolism. These processes are upregulated in hypoxic lung neutrophils which show increased lysosomal protein expression, increased protein uptake and increased glutaminolysis. Utilising heavy labelled protein extracts, I have traced breakdown products from scavenged proteins into central carbon metabolism, demonstrating that extracellular protein can fuel neutrophilic inflammation. Finally, I have investigated the role of the prolyl hydroxylase PHD1 in regulating neutrophilic inflammation. Using a neutrophil specific PHD1 knockout mouse line, I have identified a specific role for PHD1 in regulating neutrophil metabolism and survival. I have found that the micro-environment, particularly oxygen availability, determines the impact of PHD1 loss with consequences for inflammation resolution in vivo. In summary, hypoxia is a key regulator of neutrophil function and is associated with increased neutrophilic inflammation. Utilising a proteomic approach, I have identified the mechanisms which drive the hyperinflammatory phenotype including the ability of neutrophils to scavenge proteins from the environment to fuel inflammation. I have also shown that PHD1, a key component of the hypoxic signalling pathway, may regulate these functions. A more complete understanding of these mechanisms will help to identify therapeutic targets for treatment of neutrophilic inflammation in the lung

Inclusive research in education: contributions to method and debate

Education is not necessarily associated with inclusive research and the label of inclusive research is little used in our discipline. It is an umbrella term encompassing participatory, emancipatory and community/peer-led research. This is research in which those (such as learners and teachers) who tend to be the objects of other people’s research become agents in the conduct of research, ensuring that such research addresses issues that are important to them and includes their views and experiences (see Walmsley & Johnson, 2003 and Nind, 2014 for more on definitions). Conceptualising some research as inclusive is part of a concern with the democratization of the research process and with social justice - in and through - research; it represents an interest in the people outside of academia being active and credible producers of knowledge

Functional Redundancy of Class I Phosphoinositide 3-Kinase (PI3K) Isoforms in Signaling Growth Factor-Mediated Human Neutrophil Survival

We have investigated the contribution of individual phosphoinositide 3-kinase (PI3K) Class I isoforms to the regulation of neutrophil survival using (i) a panel of commercially available small molecule isoform-selective PI3K Class I inhibitors, (ii) novel inhibitors, which target single or multiple Class I isoforms (PI3Kα, PI3Kβ, PI3Kδ, and PI3Kγ), and (iii) transgenic mice lacking functional PI3K isoforms (p110δKOγKO or p110γKO). Our data suggest that there is considerable functional redundancy amongst Class I PI3Ks (both Class IA and Class IB) with regard to GM-CSF-mediated suppression of neutrophil apoptosis. Hence pharmacological inhibition of any 3 or more PI3K isoforms was required to block the GM-CSF survival response in human neutrophils, with inhibition of individual or any two isoforms having little or no effect. Likewise, isolated blood neutrophils derived from double knockout PI3K p110δKOγKO mice underwent normal time-dependent constitutive apoptosis and displayed identical GM-CSF mediated survival to wild type cells, but were sensitized to pharmacological inhibition of the remaining PI3K isoforms. Surprisingly, the pro-survival neutrophil phenotype observed in patients with an acute exacerbation of chronic obstructive pulmonary disease (COPD) was resilient to inactivation of the PI3K pathway

Mutations in succinate dehydrogenase B (SDHB) enhance neutrophil survival independent of HIF-1α expression.

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Roles of neutrophils in the regulation of the extent of human inflammation through delivery of IL-1 and clearance of chemokines

This study examined the establishment of neutrophilic inflammation in humans. We tested the hypotheses that neutrophil recruitment was associated with local CXCL8 production and that neutrophils themselves might contribute to the regulation of the size of the inflammatory response. Humans were challenged i.d. with endotoxin. Biopsies of these sites were examined for cytokine production and leukocyte recruitment by qPCR and IHC. Additional in vitro models of inflammation examined the ability of neutrophils to produce and sequester cytokines relevant to neutrophilic inflammation. i.d. challenge with 15 ng of a TLR4-selective endotoxin caused a local inflammatory response, in which 1% of the total biopsy area stained positive for neutrophils at 6 h, correlating with 100-fold up-regulation in local CXCL8 mRNA generation. Neutrophils themselves were the major source of the early cytokine IL-1β. In vitro, neutrophils mediated CXCL8 but not IL-1β clearance (>90% clearance of ≤2 nM CXCL8 over 24 h). CXCL8 clearance was at least partially receptor-dependent and modified by inflammatory context, preserved in models of viral infection but reduced in models of bacterial infection. In conclusion, in a human inflammatory model, neutrophils are rapidly recruited and may regulate the size and outcome of the inflammatory response through the uptake and release of cytokines and chemokines in patterns dependent on the underlying inflammatory stimulus

Galaxy And Mass Assembly: galaxy morphology in the green valley, prominent rings, and looser spiral arms

Galaxies broadly fall into two categories: star-forming (blue) galaxies and quiescent (red) galaxies. In between, one finds the less populated “green valley . Some of these galaxies are suspected to be in the process of ceasing their star-formation through a gradual exhaustion of gas supply or already dead and are experiencing a rejuvenation of star-formation through fuel injection. We use the Galaxy And Mass Assembly database and the Galaxy Zoo citizen science morphological estimates to compare the morphology of galaxies in the green valley against those in the red sequence and blue cloud. Our goal is to examine the structural differences within galaxies that fall in the green valley, and what brings them there. Previous results found disc features such as rings and lenses are more prominently represented in the green valley population. We revisit this with a similar sized data set of galaxies with morphology labels provided by the Galaxy Zoo for the GAMA fields based on new KiDS images. Our aim is to compare qualitatively the results from expert classification to that of citizen science. We observe that ring structures are indeed found more commonly in green valley galaxies compared to their red and blue counterparts. We suggest that ring structures are a consequence of disc galaxies in the green valley actively exhibiting characteristics of fading discs and evolving disc morphology of galaxies. We note that the progression from blue to red correlates with loosening spiral arm structure

IL4Rα signaling abrogates hypoxic neutrophil survival and limits acute lung injury responses <i>in vivo</i>

Rationale: Acute respiratory distress syndrome is defined by the presence of systemic hypoxia and consequent on disordered neutrophilic inflammation. Local mechanisms limiting the duration and magnitude of this neutrophilic response remain poorly understood.  Objectives: To test the hypothesis that during acute lung inflammation tissue production of proresolution type 2 cytokines (IL-4 and IL-13) dampens the proinflammatory effects of hypoxia through suppression of HIF-1a (hypoxia-inducible factor-1a)mediated neutrophil adaptation, resulting in resolution of lung injury.  Methods: Neutrophil activation of IL4Ra (IL-4 receptor a) signaling pathways was explored ex vivo in human acute respiratory distress syndrome patient samples, in vitro after the culture of human peripheral blood neutrophils with recombinant IL-4 under conditions of hypoxia, and in vivo through the study of IL4Ra-deficient neutrophils in competitive chimera models and wild-type mice treated with IL-4.  Measurements and Main Results: IL-4 was elevated in human BAL from patients with acute respiratory distress syndrome, and its receptor was identified on patient blood neutrophils. Treatment of human neutrophils with IL-4 suppressed HIF-1a-dependent hypoxic survival and limited proinflammatory transcriptional responses. Increased neutrophil apoptosis in hypoxia, also observed with IL-13, required active STAT signaling, and was dependent on expression of the oxygen-sensing prolyl hydroxylase PHD2. In vivo, IL-4Ra-deficient neutrophils had a survival advantage within a hypoxic inflamed niche; in contrast, inflamed lung treatment with IL-4 accelerated resolution through increased neutrophil apoptosis.  Conclusions: We describe an important interaction whereby IL4Ra-dependent type 2 cytokine signaling can directly inhibit hypoxic neutrophil survival in tissues and promote resolution of neutrophil-mediated acute lung injury

Hypoxia drives murine neutrophil protein scavenging to maintain central carbon metabolism

Limiting dysfunctional neutrophilic inflammation while preserving effective immunity requires a better understanding of the processes that dictate neutrophil function in the tissues. Quantitative mass-spectrometry identified how inflammatory murine neutrophils regulated expression of cell surface receptors, signal transduction networks, and metabolic machinery to shape neutrophil phenotypes in response to hypoxia. Through the tracing of labeled amino acids into metabolic enzymes, proinflammatory mediators, and granule proteins, we demonstrated that ongoing protein synthesis shapes the neutrophil proteome. To maintain energy supplies in the tissues, neutrophils consumed extracellular proteins to fuel central carbon metabolism. The physiological stresses of hypoxia and hypoglycemia, characteristic of inflamed tissues, promoted this extracellular protein scavenging with activation of the lysosomal compartment, further driving exploitation of the protein-rich inflammatory milieu. This study provides a comprehensive map of neutrophil proteomes, analysis of which has led to the identification of active catabolic and anabolic pathways that enable neutrophils to sustain synthetic and effector functions in the tissues