[Show abstract][Hide abstract] ABSTRACT: IL-1 is a key cytokine known to drive chronic inflammation and to regulate many physiological, immunological and neuroimmunological responses via actions on diverse cell types of the body. To determine the mechanisms of IL-1 actions as part of the inflammatory response in vivo, we generated a conditional IL-1 receptor 1 (IL-1R1) mouse mutant using the Cre/LoxP system (IL-1R1(fl/fl) ). In the mutant generated, exon 5, which encodes part of the extracellular binding region of the receptor, is flanked by LoxP sites, thereby inactivating the two previously described functional IL-1R1 gene transcripts after Cre-mediated recombination. Using keratin 14-Cre driver mice, new IL-1R1 deficient (-/-) mice were subsequently generated, in which all signaling IL-1 receptor isoforms are deleted ubiquitously. Furthermore, using vav-iCre driver mice, we deleted IL-1 receptor isoforms in the haematopoietic system. In these mice, we show that both the IL-17 and IL-22 cytokine response is reduced, when mice are challenged by the helminth Trichuris muris. We are currently crossing IL-1R1(fl/fl) mice with different Cre-expressing mice in order to study mechanisms of acute and chronic inflammatory diseases. This article is protected by copyright. All rights reserved.
Full-text · Article · Dec 2015 · European Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Interleukin-1 receptor antagonist, a naturally-occurring antagonist to the pro-inflammatory cytokine Interleukin-1, is already in clinical use. In experimental models of stroke, Interleukin-1 receptor antagonist in cerebrospinal fluid has been associated with cerebral neuroprotection and in a phase I clinical trial in patients with subarachnoid haemorrhage it crosses the blood-cerebrospinal fluid barrier. The aims of the current work were to design a dose-ranging clinical study in patients and to analyse the plasma and cerebrospinal fluid data obtained using a population pharmacokinetic modelling approach. The study was designed using prior information: a published population pharmacokinetic model and associated parameter estimates. Simulations were carried out to identify combinations of intravenous bolus and 4 h infusion doses that could achieve a concentration of 100 ng/ml in cerebrospinal fluid within approximately 30 min. The most informative time points for plasma and cerebrospinal fluid were obtained prospectively; optimisation identified five sampling time points that were included in the 15 time points in the present study design. All plasma and cerebrospinal fluid concentration data from previous and current studies were combined for updated analysis. The result of the simulations showed that a dosage regimen of 500 mg intravenous bolus and 10 mg/kg/h could achieve the target concentration, however four other regimens that represent a stepwise increase in maximum concentration were also selected. Analysis of the updated data showed improvement in parameter accuracy and predictive performance of the model; the percentage relative standard errors for fixed and random-effects parameters were <15 and 35 % respectively. A dose-ranging study was successfully designed using modelling and simulation.
No preview · Article · Oct 2015 · Journal of Pharmacokinetics and Biopharmaceutics
[Show abstract][Hide abstract] ABSTRACT: Acute brain injury is one of the leading causes of mortality and disability worldwide. Despite this, treatments for acute brain injuries are limited and there remains a massive unmet clinical need. Inflammation has emerged as a major contributor to non-communicable diseases and there is now substantial and growing evidence that inflammation, driven by the cytokine interleukin-1 (IL-1), worsens acute brain injury. IL-1 is regulated by large multi-molecular complexes called inflammasomes. Here we discuss the latest research on the regulation of inflammasomes and IL-1 in the brain, pre-clinical efforts to establish the IL-1 system as a therapeutic target, and the promise of recent and future clinical studies of blocking IL-1 action for the treatment of brain injury. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
No preview · Article · Jun 2015 · Experimental physiology
[Show abstract][Hide abstract] ABSTRACT: Inflammation that contributes to acute cerebrovascular disease is driven by the proinflammatory cytokine interleukin-1 and is known to exacerbate resulting injury. The activity of interleukin-1 is regulated by multimolecular protein complexes called inflammasomes. There are multiple potential inflammasomes activated in diverse diseases, yet the nature of the inflammasomes involved in brain injury is currently unknown. Here, using a rodent model of stroke, we show that the NLRC4 (NLR family, CARD domain containing 4) and AIM2 (absent in melanoma 2) inflammasomes contribute to brain injury. We also show that acute ischemic brain injury is regulated by mechanisms that require ASC (apoptosis-associated speck-like protein containing a CARD), a common adaptor protein for several inflammasomes, and that the NLRP3 (NLR family, pyrin domain containing 3) inflammasome is not involved in this process. These discoveries identify the NLRC4 and AIM2 inflammasomes as potential therapeutic targets for stroke and provide new insights into how the inflammatory response is regulated after an acute injury to the brain.
Full-text · Article · Mar 2015 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract] ABSTRACT: The immune system is implicated in a wide range of disorders affecting the brain and is, therefore, an attractive target for therapy. Interleukin-1 (IL-1) is a potent regulator of the innate immune system important for host defence but is also associated with injury and disease in the brain. Here, we show that IL-1 is a key mediator driving an innate immune response to inflammatory challenge in the mouse brain but is dispensable in extracerebral tissues including the lung and peritoneum. We also demonstrate that IL-1α is an important ligand contributing to the CNS dependence on IL-1 and that IL-1 derived from the CNS compartment (most likely microglia) is the major source driving this effect. These data reveal previously unknown tissue-specific requirements for IL-1 in driving innate immunity and suggest that IL-1-mediated inflammation in the brain could be selectively targeted without compromising systemic innate immune responses that are important for resistance to infection. This property could be exploited to mitigate injury- and disease-associated inflammation in the brain without increasing susceptibility to systemic infection, an important complication in several neurological disorders.This article is protected by copyright. All rights reserved
Preview · Article · Feb 2015 · European Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Cerebral ischemia is one of the most common causes of disabilities in adults and leads to long-term motor and cognitive impairments with limited therapeutic possibilities. Treatment options have proven efficient in preclinical models of cerebral ischemia but have failed in the clinical setting. This limited translation may be due to the suitability of models used and outcomes measured as most studies have focused on the early period after injury with gross motor scales, which have limited correlation to the clinical situation. The aim of this study was to determine long-term functional outcomes after cerebral ischemia in rats, focusing on fine motor function, social and depressive behavior as clinically relevant measures. A secondary objective was to evaluate the effects of an anti-inflammatory treatment (interleukin-1 receptor antagonist (IL-1Ra)) on functional recovery and compensation. Infarct volume was correlated with long-term (25 days) impairments in fine motor skills, but not with emotional components of behavior. Motor impairments could not be detected using conventional neurological tests and only detailed analysis allowed differentiation between recovery and compensation. Acute systemic administration of IL-1Ra (at reperfusion) led to a faster and more complete recovery, but delayed (24h) IL-1Ra treatment had no effect. In summary functional assessment after brain injury requires detailed motor tests in order to address long-term impairments and compensation processes that are mediated by intact tissues. Functional deficits in skilled movement after brain injury represent ideal predictors of long-term outcomes and should become standard measures in the assessment of preclinical animal models.
Full-text · Article · May 2014 · Behavioural brain research
[Show abstract][Hide abstract] ABSTRACT: Objective:
Bacterial infection contributes to diverse noninfectious diseases and worsens outcome after stroke. Streptococcus pneumoniae, the most common infection in patients at risk of stroke, is a major cause of prolonged hospitalization and death of stroke patients, but how infection impacts clinical outcome is not known.
We induced sustained pulmonary infection by a human S. pneumoniae isolate in naive and comorbid rodents to investigate the effect of infection on vascular and inflammatory responses prior to and after cerebral ischemia.
S. pneumoniae infection triggered atherogenesis, led to systemic induction of interleukin (IL) 1, and profoundly exacerbated (50-90%) ischemic brain injury in rats and mice, a response that was more severe in combination with old age and atherosclerosis. Systemic blockade of IL-1 with IL-1 receptor antagonist (IL-1Ra) fully reversed infection-induced exacerbation of brain injury and functional impairment caused by cerebral ischemia. We show that infection-induced systemic inflammation mediates its effects via increasing platelet activation and microvascular coagulation in the brain after cerebral ischemia, as confirmed by reduced brain injury in response to blockade of platelet glycoprotein (GP) Ibα. IL-1 and platelet-mediated signals converge on microglia, as both IL-1Ra and GPIbα blockade reversed the production of IL-1α by microglia in response to cerebral ischemia in infected animals.
S. pneumoniae infection augments atherosclerosis and exacerbates ischemic brain injury via IL-1 and platelet-mediated systemic inflammation. These mechanisms may contribute to diverse cardio- and cerebrovascular pathologies in humans.
No preview · Article · May 2014 · Annals of Neurology
[Show abstract][Hide abstract] ABSTRACT: The cytokine interleukin-1 (IL-1) has two main pro-inflammatory forms, IL-1α and IL-1β, which are central to host responses
to infection and to damaging sterile inflammation. Processing of IL-1 precursor proteins to active cytokines commonly occurs
through activation of proteases, notably caspases and calpains. These proteases are instrumental in cell death, and inflammation
and cell death are closely associated, hence we sought to determine the impact of cell death pathways on IL-1 processing and
release. We discovered that apoptotic regulation of caspase-8 specifically induced the processing and release of IL-1β. Conversely,
necroptosis caused the processing and release of IL-1α, and this was independent of IL-1β processing and release. These data
suggest that the mechanism through which an IL-1-expressing cell dies dictates the nature of the inflammatory mechanism that
follows. These insights may allow modification of inflammation through the selective targeting of cell death mechanisms during
[Show abstract][Hide abstract] ABSTRACT: Interleukin-1 (IL-1) is a key mediator of ischaemic brain injury induced by stroke and subarachnoid haemorrhage (SAH). IL-1 receptor antagonist (IL-1Ra) limits brain injury in experimental stroke and reduces plasma inflammatory mediators associated with poor outcome in ischaemic stroke patients. Intravenous (IV) IL-1Ra crosses the blood-brain barrier (BBB) in patients with SAH, to achieve cerebrospinal fluid (CSF) concentrations that are neuroprotective in rats.
A small phase II, double-blind, randomised controlled study was carried out across two UK neurosurgical centres with the aim of recruiting 32 patients. Adult patients with aneurysmal SAH, requiring external ventricular drainage (EVD) within 72 hours of ictus, were eligible. Patients were randomised to receive IL-1Ra (500 mg bolus, then a 10 mg/kg/hr infusion for 24 hours) or placebo. Serial samples of CSF and plasma were taken and analysed for inflammatory mediators, with change in CSF IL-6 between 6 and 24 hours as the primary outcome measure.
Six patients received IL-1Ra and seven received placebo. Concentrations of IL-6 in CSF and plasma were reduced by one standard deviation in the IL-1Ra group compared to the placebo group, between 6 and 24 hours, as predicted by the power calculation. This did not reach statistical significance (P = 0.08 and P = 0.06, respectively), since recruitment did not reach the target figure of 32. No adverse or serious adverse events reported were attributable to IL-1Ra.
IL-1Ra appears safe in SAH patients. The concentration of IL-6 was lowered to the degree expected, in both CSF and plasma for patients treated with IL-1Ra.
Full-text · Article · Jan 2014 · Journal of Neuroinflammation
[Show abstract][Hide abstract] ABSTRACT: Acute-phase proteins (APPs) are key effectors of the immune response and are routinely used as biomarkers in cerebrovascular diseases, but their role during brain inflammation remains largely unknown. Elevated circulating levels of the acute-phase protein pentraxin-3 (PTX3) are associated with worse outcome in stroke patients. Here we show that PTX3 is expressed in neurons and glia in response to cerebral ischemia, and that the proinflammatory cytokine interleukin-1 (IL-1) is a key driver of PTX3 expression in the brain after experimental stroke. Gene deletion of PTX3 had no significant effects on acute ischemic brain injury. In contrast, the absence of PTX3 strongly compromised blood-brain barrier integrity and resolution of brain edema during recovery after ischemic injury. Compromised resolution of brain edema in PTX3-deficient mice was associated with impaired glial scar formation and alterations in scar-associated extracellular matrix production. Our results suggest that PTX3 expression induced by proinflammatory signals after ischemic brain injury is a critical effector of edema resolution and glial scar formation. This highlights the potential role for inflammatory molecules in brain recovery after injury and identifies APPs, in particular PTX3, as important targets in ischemic stroke and possibly other brain inflammatory disorders.Journal of Cerebral Blood Flow & Metabolism advance online publication, 18 December 2013; doi:10.1038/jcbfm.2013.224.
Full-text · Article · Dec 2013 · Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Ischemic stroke is confounded by conditions such as atherosclerosis, diabetes and infection, all of which alter peripheral inflammatory processes with concomitant impact on stroke outcome. The majority of the stroke patients are elderly, but the impact of interactions between aging and inflammation on stroke remains unknown. We thus investigated the influence of age on the outcome of stroke in animals predisposed to systemic chronic infection. Th1-polarized chronic systemic infection was induced in 18-22 month and 4-month-old C57BL/6j mice by administration of T. muris (gut parasite). One month after infection, mice underwent permanent middle cerebral artery occlusion and infarct size, brain gliosis and brain and plasma cytokine profiles were analyzed. Chronic infection increased the infarct size in aged but not in young mice at 24 hours. Aged, ischemic mice showed altered plasma and brain cytokine responses while the lesion size correlated with plasma pre-stroke levels of RANTES. Moreover, the old, infected mice exhibited significantly increased neutrophil recruitment and up-regulation of both plasma interleukin-17α and tumor necrosis factor α levels. Neither age nor infection status alone or in combination altered the ischemia-induced brain microgliosis. Our results show that chronic peripheral infection in aged animals renders the brain more vulnerable to ischemic insults, possibly by increasing the invasion of neutrophils and altering the inflammation status in the blood and brain. Understanding the interactions between age and infections is crucial for developing a better therapeutic regimen for ischemic stroke and when modeling it as a disease of the elderly. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Macrophage can adopt several phenotypes, process call polarization, which is crucial for shaping inflammatory responses to injury. It is not known if microglia, a resident brain macrophage population, polarizes in a similar way, and whether specific microglial phenotypes modulate cell death in response to brain injury. In this study, we show that both BV2-microglia and mouse bone marrow derived macrophages (BMDMs) were able to adopt different phenotypes after LPS (M1) or IL-4 (M2) treatment in vitro, but regulated cell death differently when added to mouse organotypic hippocampal brain slices. BMDMs induced cell death when added to control slices and exacerbated damage when combined with oxygen-glucose deprivation (OGD), independently of their phenotype. In contrast, vehicle- and M2-BV2-microglia were protective against OGD-induced death. Direct treatment of brain slices with IL-4 (without cell addition) was protective against OGD and induced an M2 phenotype in the slice. In vivo, intracerebral injection of LPS or IL-4 in mice induced microglial phenotypes similar to the phenotypes observed in brain slices and in cultured cells. After injury induced by middle cerebral artery occlusion, microglial cells did not adopt classical M1/M2 phenotypes, suggesting that another subtype of regulatory phenotype was induced. This study highlights functional differences between macrophages and microglia, in response to brain injury with fundamentally different outcomes, even if both populations were able to adopt M1 or M2 phenotypes. These data suggest that macrophages infiltrating the brain from the periphery after an injury may be cytotoxic, independently of their phenotype, while microglia may be protective.
[Show abstract][Hide abstract] ABSTRACT: Interleukin-1 (IL-1) is a key regulator of inflammation and ischaemic brain injury, but the contribution of central and peripheral sources of IL-1 to brain injury is not well understood. Here we show that haematopoietic-derived IL-1 is a key driver of ischaemic brain injury. Wild type (WT) mice transplanted with IL-1αβ-deficient bone marrow displayed a significant (40%) reduction in brain injury induced by focal cerebral ischaemia compared to WT mice transplanted with WT bone marrow. This was paralleled by improved neurological outcome and the almost complete absence of splenic, but not liver-derived IL-1α after stroke in WT mice lacking haematopoietic-derived IL-1. IL-1αβ KO mice transplanted with IL-1αβ-deficient bone marrow showed a 60% reduction in brain injury compared to WT mice receiving WT bone marrow. Transplantation of WT bone marrow to IL-1αβ KO mice resulted in a similar level of blood brain barrier injury to WT mice receiving IL-1αβ-deficient bone marrow. Cerebral oedema after brain injury was reduced in IL-1αβ KO recipients irrespective of donor-derived IL-1, but a lack of haematopoetic IL-1 has also been associated with smaller brain oedema independently of recipient status. Thus, both central and haematopoietic-derived IL-1 are important contributors to brain injury after cerebral ischaemia. Identification of the cellular sources of IL-1 in the periphery could allow targeted interventions at these sites.
Preview · Article · Mar 2013 · Disease Models and Mechanisms
[Show abstract][Hide abstract] ABSTRACT: Neuroinflammation is involved in several brain disorders and can be monitored through expression of the translocator protein 18 kDa (TSPO) on activated microglia. In recent years, several new PET radioligands for TSPO have been evaluated in disease models. [18F]DPA-714 is a TSPO radiotracer with great promise; however results vary between different experimental models of neuroinflammation. To further examine the potential of [18F]DPA-714, it was compared directly to [11C]PK11195 in experimental cerebral ischaemia in rats.
[Show abstract][Hide abstract] ABSTRACT: Comparison between [11C]PK11195 and [18F]DPA-714 R1 and binding potential (BPND) for the core of the infarct in rats scanned with both [11C]PK11195 and [18F]DPA-714 and with visible infarct (n = 7). * indicates significant differences between [11C]PK11195 and [18F]DPA-714 values, Wilcoxon test.
[Show abstract][Hide abstract] ABSTRACT: Representative [11C]PK11195 (left panel) and [18F]DPA-714 (right panel) PET summed images of 2 rats scanned with both tracers successively within 24 h, co-registered with the MRI template (A). (B) T2 MRI template with simplified brain atlas ROI overlaid on the right hemisphere and corresponding coronal level of the Paxinos and Watson rat brain atlas (C). Arrow heads in panel A indicates area of heterogeneous tracer uptake in the caudate-putamen (dashed line on the PET images).
[Show abstract][Hide abstract] ABSTRACT: Representative images of Claudin-5 and IgG immunohistochemistry (left panel) and [11C]PK11195 and [18F]DPA-74 PET images (right panel) co-registered with the MRI template of the same animal (rat #1) at similar coronal level. Dotted and dashed lines represent the edge of the infarct/BBB disruption as detected by IgG diffusion in the brain parenchyma and lack of Claudin-5 immunostaining (tigh-junction disruption), overlap is seen for most of the area, although partial restoration of the tight-junction can be seen in the striatum (double-dotted/dashed line) with the Claudin-5 immunostaining (left middle panel). The approximate corresponding infarct delineation is also indicated on the PET images in the right panel.
[Show abstract][Hide abstract] ABSTRACT: Acute brain injury results in peripheral inflammatory changes, although the impact of these processes on neuronal death and neuroinflammation is currently unclear. To facilitate the translation of experimental studies to clinical benefit, it is vital to characterize the mechanisms by which acute brain injury induces peripheral inflammatory changes, and how these are affected by surgical manipulation in experimental models. Here we show that in mice, even mild surgical manipulation of extracranial tissues induced marked granulocyte mobilization (300%) and systemic induction of cytokines. However, intracranial changes induced by craniotomy, or subsequent induction of focal cerebral ischemia were required to induce egress of CXCR2-positive granulocytes from the bone marrow. CXCR2 blockade resulted in reduced mobilization of granulocytes from the bone marrow, caused an unexpected increase in circulating granulocytes, but failed to affect brain injury induced by cerebral ischemia. We also demonstrate that isoflurane anaesthesia interferes with circulating leukocyte responses, which could contribute to the reported vascular and neuroprotective effects of isoflurane. In addition, no immunosuppression develops in the bone marrow after experimental stroke. Thus, experimental models of cerebral ischemia are compromised by surgery and anaesthesia in proportion to the severity of surgical intervention and overall tissue injury. Understanding the inherent confounding effects of surgical manipulation and development of new models of cerebral ischemia with minimal surgical intervention could facilitate better understanding of interactions between inflammation and brain injury.
Full-text · Article · Jan 2013 · Frontiers in Neuroscience
[Show abstract][Hide abstract] ABSTRACT: BackgroundCytokines and cytokine receptor concentrations increase in plasma and cerebrospinal fluid (CSF) of patients following subarachnoid haemorrhage (SAH). The relationship between plasma and CSF cytokines,
and factors affecting this, are not clear.MethodsTo help define the relationship, paired plasma and cerebrospinal fluid (CSF) samples were collected from patients subject to ventriculostomy. Concentrations of key inflammatory cytokines, interleukin (IL)-1ß, IL-1 receptor antagonist (IL-1Ra), IL-1 receptor 2, IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-α, and TNF receptors (TNF-R) 1 and 2 were determined by immunoassay of CSF and plasma from 21 patients, where samples were available at three or more time points.ResultsPlasma concentrations of IL-1ß, IL-1Ra, IL-10, TNF-α and TNF-R1 were similar to those in CSF. Plasma TNF-R2 and IL-1R2 concentrations were higher than in CSF. Concentrations of IL-8 and IL-6 in CSF were approximately10 to 1,000-fold higher than in plasma. There was a weak correlation between CSF and plasma IL-8 concentrations (r = 0.26), but no correlation for IL-6. Differences between the central and peripheral pattern of IL-6 were associated with episodes of ventriculostomy-related infection (VRI). A VRI was associated with CSF IL-6 >10,000 pg/mL (P = 0.0002), although peripheral infection was not significantly associated with plasma IL-6.ConclusionsThese data suggest that plasma cytokine concentrations cannot be used to identify relative changes in the CSF, but that measurement of CSF IL-6 could provide a useful marker of VRI.
Full-text · Article · Nov 2012 · Journal of Neuroinflammation