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Brough, D.

Publications and source records attributed to Brough, D..

At least 19 recordsLinked to original sources

In vivo cellular localisation and nanoscale organisation of NLRP3 inflammasomes

The NLRP3 inflammasome is a critical regulator of inflammation, yet the localisation, organisation, and cellular sources of endogenous NLRP3 inflammasomes remain incompletely understood. Here, we generated NLRP3-mScarlet-I endogenous reporter mice enabling visualisation of NLRP3 at physiological levels in primary cells and in vivo. We show that activated NLRP3 associated with PI4P-positive membranes from multiple organelles, supporting a model where diverse membrane platforms act as a scaffold to nucleate inflammasome assembly. Super-resolution imaging revealed that NLRP3 and ASC occupy distinct nanoscale architectures within the inflammasome, with NLRP3 displaying marked structural heterogeneity and stimulus-dependent organisation. Unexpectedly, circulating monocytes and neutrophils, rather than tissue-resident populations, emerged as the dominant NLRP3-expressing cells in vivo which rapidly infiltrated tissues following systemic inflammation, highlighting an underappreciated cellular source of rapid inflammasome-driven responses. These findings reveal previously unrecognised insights into inflammasome organisation and localisation, establishing a powerful resource for investigating endogenous NLRP3 biology in health and disease.

immunology↗

Specific deletion of interleukin-1 beta in microglia improves acute outcome and modulates neurogenesis after ischemic stroke

Interleukin-1 (IL-1) signaling is a major driver of post-ischemic neuroinflammation, yet the cell- and isoform-specific roles of the two major IL-1 receptor type 1 agonists, IL-1 and IL-1{beta}, remain incompletely defined in the context of stroke. Microglia rapidly express IL-1 after cerebral ischemia, whereas IL-1{beta} expression is delayed and restricted to a small subset of microglia and infiltrating immune cells. Here, we investigated for the first time the specific contribution of microglial-derived IL-1{beta} to acute injury and post-stroke neurorepair after transient middle cerebral artery occlusion in male and female mice, through microglial-specific tamoxifen-inducible Cre-loxP-mediated recombination. Deletion of microglial IL-1{beta} improved acute neurological outcome, reduced neutrophil accumulation in the ischemic brain and dampened systemic inflammatory cytokines. These effects were most evident during the acute phase and in female in mice. In contrast, long-term functional recovery was largely unaffected. However, microglial IL-1{beta} deletion differentially regulated post-stroke neurogenesis, enhancing subventricular zone neurogenic responses and ectopic neuroblast migration while limiting hippocampal neurogenesis. Together, these findings identify microglial IL-1{beta} as a key amplifier of early inflammatory injury after stroke, exerting region-specific effects on neurogenic niches, and highlight distinct, non-redundant roles for microglial IL-1 isoforms in ischemic brain injury and repair.

neuroscience↗

Inflammatory responses following CRISPR modification of the nuclear localisation sequence in endogenous interleukin-1α

Interleukin (IL)-1 is a pro-inflammatory member of the IL-1 cytokine superfamily and is important for inflammatory responses to infection and injury. Unlike pro-IL-1{beta}, pro-IL-1 is mainly localised to the nucleus upon expression. This is mediated by a nuclear localisation sequence (NLS) responsible for its importin-dependent transport into the nucleus. This nuclear localisation and the presence of histone acetyl transferase (HAT)-binding domains within the pro-domain suggest a role of this cytokine in gene transcription regulation. In addition, nuclear trafficking of pro-IL-1 is proposed to regulate its secretion. To-date, studies on the nuclear role of pro-IL-1 have used overexpression systems. Here, we generated a mouse where the endogenous Il1a gene was edited with CRISPR to disrupt the NLS (mNLS). Using an in vitro approach with murine macrophages we found that this NLS mutation did not affect pro-IL-1 RNA expression levels in response to LPS but increased its protein expression levels. Moreover, we found that the transcriptional signature induced by LPS was not altered between WT and mNLS macrophages. Release of IL-1 in response to different stimuli such as ionomycin was not negatively impacted by disrupted nuclear localisation, although higher levels of IL-1 release were detected, potentially due to increased levels of pro-IL-1. Inflammatory responses in an in vivo model of peritonitis and an influenza infection model were comparable between WT and mNLS mice. Thus, we have established a mouse model in which pro-IL-1 nuclear localisation is disrupted, although future research is required to reveal the importance of this nuclear localisation for IL-1 function.

immunology↗

Lysosome positioning affects NLRP3 inflammasome activation

The NLRP3 inflammasome, an important multi-molecular protein complex driving inflammation, is activated by multiple cellular stresses, including a loss of organelle homeostasis. Studies indicate that lysosome disruption can play a role in NLRP3 inflammasome activation, but whether lysosome positioning impacts NLRP3 inflammasome activation is currently unknown. Using HeLa and macrophage cell models, the effect of repositioning lysosomes to either the cell periphery or the perinuclear region on inflammasome activation was studied. Lysosome positioning to the cell periphery increased NLRP3 inflammasome activation in response to nigericin. This effect correlated with a change in the subcellular localisation of the inflammasome complex and an increase in its size. As macrophages at sites of tissue inflammation are exposed to environments known to influence lysosome position, these data help us understand how subcellular organelle reorganisation can regulate inflammation in response to inflammatory stimuli.

immunology↗

Cell volume tunes macrophage innate inflammatory responses through promoting type I interferon signalling.

Macrophages are key effectors in co-ordinating inflammatory and immune responses to threats to the host. How macrophages decipher diverse danger signals to tailor inflammatory responses remains an unanswered question. Cell volume control is critical for normal cellular function. Disturbances in extracellular and intracellular homeostasis induce changes in cell volume, but the impact of disruptions in cell volume in controlling macrophage inflammatory responses is poorly understood. Here, we discover that macrophages use cell volume control as a bona fide danger sensing mechanism to promote and augment inflammatory responses. Using macrophages deficient in the volume regulated anion channel (VRAC), which lack cell volume control under hypo-osmotic conditions, we show that disruptions in cell volume are sensed by macrophages to drive a large transcriptomic response and induction of inflammation. Cell volume disruption, particularly loss of cell volume control, induces type I interferon signalling through a DNA- and STING-dependent mechanism, but independent of cGAS and 23cGAMP transport. Further, we found that cell volume changes synergise with diverse pathogen-mediated signalling to augment type I interferon responses and exacerbate the cytokine storm in a mouse model of hyperinflammation. Our findings highlight cell volume as an important regulator in shaping inflammatory responses, adding to our understanding of how macrophages sense complex danger signals and threats.

immunology↗

Cerebral ischaemic stroke results in altered mucosal IgA responses and host-commensal microbiota interactions.

Stroke is a devastating neurological event with a high risk of mortality, but also results in long-term sequalae in survivors that extend beyond the central nervous system. Notably, these include gastrointestinal dysfunction and alterations in the commensal microbiota in both patients and mouse models, which have been suggested to contribute to secondary infection and poor outcome following stroke. Strikingly changes in commensal microbial community composition occur rapidly in both humans and animal models following stroke and correlate with disease severity. Despite these observations the underpinning mechanisms that drive alterations in the microbiota post-stroke remain poorly understood. The gastrointestinal tract is home to a complex network of tissue-resident immune cells that act constitutively to maintain microbial community and prevent bacterial-driven inflammation. Here we demonstrate that mice subjected to ischaemic stroke exhibit alterations in the intestinal immune system, most notably in antibody secreting B cells and the production of Immunoglobulin A (IgA) - a major effector response against commensal microbes. Mice lacking secretory IgA binding to commensal bacteria exhibit a partial reversion of stroke-induced changes in microbiota composition. Notably we also report increases in B cell and IgA-producing plasma cell frequencies in the brain and meninges following stroke. Together these findings demonstrate stroke is associated with perturbations in antibody producing immune responses both in mucosal tissues and the CNS following stroke, which in part explain stroke-induced changes in the intestinal microbiota. A mechanistic understanding of the immunological basis of stroke-associated pathologies in the periphery may open new avenues to manage the secondary complications and long-term prognosis of patients suffering from neurological disease.

immunology↗

High-Dimensional Imaging of Vestibular Schwannoma Reveals Distinctive Immunological Networks Across Histomorphic Niches in NF2-related Schwannomatosis

NF2-related Schwannomatosis (NF2 SWN) is a rare tumour-predisposition syndrome characterised by the growth of multiple central and peripheral nervous system neoplasms. The drivers of NF2 SWN are pathogenic variants in the tumour suppressor gene NF2, encoding the protein Merlin, leading to development of bilateral vestibular schwannoma (VS) in >95% of patients. VS tumours are characterised by infiltration of myeloid cells and lymphocytes, highlighting the potential of immunotherapy for VS. However, the immunological landscape in VS and the spatial determinants within the tumour microenvironment that shape the trajectory of disease are presently unknown. In this study, to elucidate the complex immunological networks across VS, we performed imaging mass cytometry (IMC) on clinically annotated VS samples from NF2 SWN patients. We reveal the heterogeneity in neoplastic cell, myeloid cell and T cell populations that co-exist within VS, determining that the cellular composition of VS tumours is independent of NF2-SWN genetic severity. We show that distinct myeloid cell and Schwann cell populations exist within varied spatial contextures across characteristic Antoni A and B histomorphic niches. Interestingly, we show that T-cell populations associate with tumour-associated macrophages (TAMs) in Antoni A regions, seemingly limiting their ability to interact with tumorigenic Schwann cells. This spatial landscape is altered in Antoni B regions, where T-cell populations appear to interact with PD-L1+ Schwann cells. We also demonstrate that prior bevacizumab treatment (VEGF-A antagonist) preferentially reduces alternatively-activated TAMs, whilst enhancing CD44 expression, in bevacizumab-treated tumours. Together, we describe niche-dependent modes of T-cell regulation in NF2 SWN VS, indicating the potential for microenvironment-altering therapies for VS. TeaserImaging mass cytometry and spatial omic analyses illustrate spatially-distinct regions of T-cell regulation in vestibular schwannoma.

immunology↗

The NLRP3 inflammasome is essential for IL-18 production in a murine model of macrophage activation syndrome.

Hyperinflammatory disease is associated with an aberrant immune response resulting in cytokine storm. One such instance of hyperinflammatory disease is known as macrophage activation syndrome (MAS). The pathology of MAS can be characterised by significantly elevated serum levels of interleukin (IL)-18 and interferon (IFN)-{gamma}. Given the role for IL-18 in MAS, we sought to establish the role of inflammasomes in the disease process. Using a murine model of CpG-DNA induced MAS, we discovered that the expression of the NLRP3 inflammasome was increased and correlated with IL-18 production. Inhibition of the NLRP3 inflammasome, or downstream caspase-1, prevented MAS-mediated upregulation of plasma IL-18 but interestingly did not alleviate key features of hyperinflammatory disease including hyperferritinaemia and splenomegaly. Furthermore IL-1 receptor blockade with IL-1Ra did not prevent the development of CpG-induced MAS, despite being clinically effective in the treatment of MAS. These data demonstrate that in the development of MAS, the NLRP3 inflammasome was essential for the elevation in plasma IL-18, a key cytokine in clinical cases of MAS, but was not a driving factor in the pathogenesis of CpG-induced MAS.

immunology↗

Selective deletion of interleukin-1 alpha in microglia regulates neuronal activity and neurorepair processes after experimental ischemic stroke.

Inflammation is a key contributor to stroke pathogenesis and exacerbates brain damage leading to poor outcome. Interleukin-1 (IL-1) is an important regulator of post-stroke inflammation, and blocking its actions is beneficial in pre-clinical stroke models and safe in the clinical setting. However, the distinct roles of the two major IL-1 receptor type 1 agonists, IL-1 and IL-1{beta}, and the specific role of IL-1 in ischemic stroke remain largely unknown. Here we show that IL-1 and IL-1{beta} have different spatio-temporal expression profiles in the brain after experimental stroke, with early microglial IL-1 expression (4 h) and delayed IL-1{beta} expression in infiltrated neutrophils and a small microglial subset (24-72 h). We examined for the first time the specific role of microglial-derived IL-1 in experimental permanent and transient ischemic stroke through microglial-specific tamoxifen-inducible Cre-loxP-mediated recombination. Microglial IL-1 deletion did not influence acute brain damage, cerebral blood flow, IL-1{beta} expression, neutrophil infiltration, microglial nor endothelial activation after ischemic stroke. However, microglial IL-1 knock out (KO) mice showed reduced peri-infarct vessel density and reactive astrogliosis at 14 days post-stroke, alongside long-term impaired functional recovery. Our study identifies for the first time a critical role for microglial IL-1 on neurorepair and functional recovery after stroke, highlighting the importance of targeting specific IL-1 mechanisms in brain injury to develop more effective therapies.

neuroscience↗

Pyroptosis leads to loss of centrosomal integrity in macrophages

NLRP3 forms a multiprotein inflammasome complex to initiate the inflammatory response when macrophages sense infection or tissue damage, which leads to caspase-1 activation and maturation and release of the inflammatory cytokines interleukin-1{beta} (IL-1{beta}) and IL-18, and Gasdermin-D (GSDMD) mediated pyroptosis. NLRP3 inflammasome activity must be controlled as unregulated and chronic inflammation underlies inflammatory and autoimmune diseases. Several findings uncovered that NLRP3 inflammasome activity is under the regulation of centrosome localized proteins such as NEK7 and HDAC6, however, whether the centrosome composition or structure is altered during the inflammasome activation is not known. Our data show that levels of the centrosomal scaffold protein pericentrin (PCNT) are reduced upon NLRP3 inflammasome activation via different activators in human and murine macrophages. PCNT loss occurs in the presence of membrane stabilizer punicalagin, suggesting this is not a consequence of membrane rupture. We found that PCNT loss is dependent on NLRP3 and active caspases as MCC950 and pan caspase inhibitor ZVAD prevent its degradation. Moreover, caspase-1 and GSDMD are both required for this NLRP3-mediated PCNT loss because absence of caspase-1 or GSDMD triggers an alternative regulation of PCNT via its cleavage by caspase-3 in response to nigericin stimulation. PCNT degradation occurs in response to nigericin, but also other NLRP3 activators including lysomotropic agent L-Leucyl-L-Leucine methyl ester (LLOMe) and hypotonicity. Our work reveals that the NLRP3 inflammasome activation affects centrosome composition and structure which may deepen our understandings of how activated NLRP3 inflammasomes are involved in the pathogenesis of inflammatory diseases.

immunology↗

Brazilin is a Natural Product Inhibitor of the NLRP3 Inflammasome

Excessive or aberrant NLRP3 inflammasome activation has been implicated in the progression and initiation of many inflammatory conditions; however, currently no NLRP3 inflammasome inhibitors have been approved for therapeutic use in the clinic. Here we have identified that the natural product brazilin effectively inhibits both priming and activation of the NLRP3 inflammasome in cultured murine macrophages, a human iPSC microglial cell line and in a mouse model of acute peritoneal inflammation. Through computational modelling, we predict that brazilin can adopt a favourable binding pose within a site of the NLRP3 protein which is essential for its conformational activation. Our results not only encourage further evaluation of brazilin as a therapeutic agent for NLRP3-related inflammatory diseases, but also introduce this small-molecule as a promising scaffold structure for the development of derivative NLRP3 inhibitor compounds.

molecular biology↗

Hypoxia coordinates the spatial landscape of myeloid cells within glioblastoma to affect outcome

Myeloid cells are highly prevalent in glioblastoma (GBM), existing in a spectrum of phenotypic and activation states. We currently have limited knowledge of the tumour microenvironment (TME) determinants that influence the localisation and the functions of the diverse myeloid cell populations in GBM. Here we have utilised orthogonal imaging mass cytometry with single cell and spatial transcriptomics approaches to identify and map the various myeloid populations in the human GBM tumour microenvironment (TME). Our results show that different myeloid populations have distinct and reproducible compartmentalisation patterns in the GBM TME that is driven by tissue hypoxia, regional chemokine signalling, and varied homotypic and heterotypic cellular interactions. We subsequently identified specific tumour sub-regions in GBM, based upon composition of identified myeloid cell populations, that were linked to patient survival. Our results provide new insight into the spatial organisation of myeloid cell sub populations in GBM, and how this is predictive of clinical outcome. TeaserMulti-modal mapping reveals that the spatial organisation of myeloid cells in glioblastoma impacts disease outcome.

cancer biology↗

Proximity labelling and evolutionary evidence reveal insights into IL-1α nuclear networks and function

Interleukin (IL)-1 is a suggested dual-function cytokine that diverged from IL-1{beta} in mammals potentially by acquiring additional biological roles that relate to highly conserved regions in the pro-domain of IL-1, including a nuclear localisation sequence (NLS) and histone acetyl transferase (HAT)-binding domains. Why evolution modified pro-IL-1s subcellular location and protein interactome, and how this shaped IL-1s intracellular role, is unknown. TurboID proximity labelling with pro-IL-1 suggested a nuclear role for pro-IL-1 that involved interaction with HATs, including EP300. We also identified and validated inactivating mutations in the pro-IL-1 NLS of multiple mammalian species. However, HAT-binding domains were also conserved in species that had lost pro-IL-1 nuclear localisation. Together, these data suggest that HAT binding and nuclear localisation occurred together, and that while some species lost the NLS in their pro-IL-1, HAT binding was maintained. The NLS was lost from several distinct species at different evolutionary times, suggesting convergent evolution, and that the loss of the NLS confers some important biological outcome.

immunology↗

Stroke induces early recurrent vascular events by inflammasome-dependent atherosclerotic plaque rupture

The risk of early recurrent events after stroke remains high despite currently established secondary prevention strategies. Risk is particularly high in patients with atherosclerosis, with more than 10% of patients experiencing early recurrent events. However, despite the enormous medical burden of this clinical phenomenon, the underlying mechanisms leading to increased vascular risk and recurrent stroke are largely unknown. Here, using a novel mouse model of stroke-induced recurrent ischemia, we show that stroke leads to activation of the AIM2 inflammasome in vulnerable atherosclerotic plaques via an increase of circulating cell-free DNA from the ischemic tissue. Enhanced plaque inflammation post-stroke results in plaque destabilization and atherothrombosis, finally leading to arterio-arterial embolism and recurrent stroke within days after the index stroke. We confirm key steps of plaque destabilization also after experimental myocardial infarction and in carotid artery plaque samples from patients with acute stroke. Neutralization of cell-free DNA by DNase treatment or inhibition of inflammasome activation reduced the rate of stroke recurrence after experimental stroke. Our findings present an explanation for the high recurrence rate after incident ischemic events in atherosclerotic patients. The detailed mechanisms uncovered here provide so far clinically uncharted therapeutic targets for which we show high efficacy to prevent recurrent events. Targeting DNA-mediated inflammasome activation after remote tissue injury represents a promising avenue for further clinical development in the prevention of early recurrent events.

immunology↗

Trends in Subcutaneous Tumour Height and Impact on Measurement Accuracy

Tumour volume is typically calculated using only length and width measurements, using width as a proxy for height in a 1:1 ratio. When tracking tumour growth over time, important morphological information and measurement accuracy is lost by ignoring height, which we show is a unique variable. Lengths, widths, and heights of 9,522 subcutaneous tumours in mice were measured using 3D and thermal imaging. The average width:height ratio was found to be 1:3 proving that using width as a proxy for height overestimates tumour volume. Comparing volumes calculated with and without tumour height to the true volumes of excised tumours indeed showed that using the volume formula including height produced volumes 36X more accurate. Monitoring the width:height relationship (prominence) across tumour growth curves indicated that prominence varied, and that height could change independent of width. Twelve cell lines were investigated individually; the scale of tumour prominence was cell line-dependent with relatively less prominent tumours (MC38, BL2, LL/2) and more prominent tumours (RENCA, HCT116) detected. Prominence trends across the growth cycle were also dependent on cell line; prominence was correlated with tumour growth in some cell lines (4T1, CT26, LNCaP), but not others (MC38, TC-1, LL/2). When pooled, invasive cell lines produced tumours that were significantly less prominent at volumes >1200mm3 compared to non-invasive cell lines (P<0.001). Modelling was used to show the impact of the increased accuracy gained by including height in volume calculations on several efficacy study outcomes. Variations in accuracy contribute to experimental variation and irreproducibility of data, therefore we strongly advise researchers to measure height to improve accuracy in tumour studies.

cancer biology↗

Discovery of an AIM2 inflammasome inhibitor for the treatment of DNA-driven inflammatory disease.

Inflammation driven by DNA sensors is now understood to be central to disease pathogenesis. Here we describe new inhibitors of pathogenic DNA sensing, primarily of the inflammasome forming sensor AIM2. Molecular modelling and biochemistry has revealed potent inhibitors of AIM2 that work by binding competitively to the DNA binding site. Though less potent, these AIM2 inhibitors, 4-sulfonic calixarenes, also inhibit DNA sensors cGAS and TLR9 demonstrating a broad utility against pathogenic DNA-driven inflammatory responses. The 4-sulfonic calixarenes inhibited AIM2 dependent post-stroke T cell death, highlighting a proof of concept that the 4-sulfonic calixarenes could be effective at combatting post-stroke immunosuppression. By extension, we propose a broad utility against DNA driven inflammation in disease. Finally, we reveal that the ancient drug suramin, by virtue of its structural similarities, is an excellent inhibitor of DNA-dependent inflammation and propose that suramin could be rapidly repurposed to meet an ever increasing clinical need.

immunology↗

NLRP3 activation in response to disrupted endocytic traffic

Inflammation driven by the NLRP3 inflammasome is coordinated through multiple signaling pathways and with a poorly defined regulation by sub-cellular organelles. Here, we tested the hypothesis that NLRP3 senses disrupted endosome trafficking to trigger inflammasome formation and inflammatory cytokine secretion. NLRP3-activating stimuli disrupted endosome trafficking and triggered localization of NLRP3 to vesicles positive for endosome markers and the inositol lipid PtdIns4P. Chemical disruption of endosome trafficking sensitized macrophages to the NLRP3 activator imiquimod driving enhanced inflammasome activation and cytokine secretion. Together these data suggest that NLRP3 is capable of sensing disruptions in the trafficking of endosomal cargoes, and that this may explain in part the spatial activation of the NLRP3 inflammasome complex. These data highlight new mechanisms amenable for the therapeutic targeting of NLRP3. One-Sentence SummaryNLRP3 senses disruptions in endosome trafficking to trigger the formation of an inflammasome complex and initiate an inflammatory response.

immunology↗

Itaconate and fumarate derivatives exert a dual inhibitory effect on canonical NLRP3 activation in macrophages and microglia

The NLRP3 inflammasome is a multi-protein complex that regulates the protease caspase-1 and subsequent interleukin (IL)-1{beta} release from cells of the innate immune system, or microglia in the brain, in response to infection or injury. Derivatives of the metabolites itaconate and fumarate, dimethyl itaconate (DMI), 4-octyl itaconate (4OI) and dimethyl fumarate (DMF), limit both expression of IL-1{beta}, and IL-1{beta} release following NLRP3 inflammasome activation. However, the direct effects of these metabolite derivatives on NLRP3 inflammasome responses in macrophages and microglia require further investigation. Using murine bone marrow-derived macrophages, mixed glia and organotypic hippocampal slice cultures (OHSCs), we demonstrate that DMI and 4OI pre-treatment limited IL-1{beta}, IL-6 and tumor necrosis factor production in response to lipopolysaccharide (LPS) priming, as well as inhibiting subsequent NLRP3 inflammasome activation. DMI, 4OI, DMF and monomethyl fumarate (MMF), another fumarate derivative, also directly inhibited biochemical markers of NLRP3 activation in LPS-primed macrophages, mixed glia and OHSCs, including ASC speck formation, caspase-1 activation, gasdermin D cleavage and IL-1{beta} release. Finally, DMF, an approved treatment for multiple sclerosis, as well as DMI, 4OI and MMF, inhibited NLRP3 activation in macrophages in response to the phospholipid lysophosphatidylcholine, which is used to induce demyelination, suggesting a possible mechanism of action for DMF in multiple sclerosis through NLRP3 inhibition. Together, these findings reveal the importance of immunometabolic regulation for both the priming and activation steps of NLRP3 activation in macrophages and microglia. Furthermore, we highlight itaconate and fumarate derivatives as a potential therapeutic option in NLRP3-driven diseases, including in the brain. Summary statementWe show that itaconate and fumarate derivatives inhibit both the priming and activation steps of NLRP3 inflammasome responses in macrophages and microglia, revealing the importance of immunometabolic NLRP3 regulation.

immunology↗