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Lana D, Magni G, Landucci E, Wenk GL, Pellegrini-Giampietro DE, Giovannini MG. Phenomic Microglia Diversity as a Druggable Target in the Hippocampus in Neurodegenerative Diseases. Int J Mol Sci 2023; 24:13668. [PMID: 37761971 PMCID: PMC10531074 DOI: 10.3390/ijms241813668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/31/2023] [Accepted: 09/02/2023] [Indexed: 09/29/2023] Open
Abstract
Phenomics, the complexity of microglia phenotypes and their related functions compels the continuous study of microglia in disease animal models to find druggable targets for neurodegenerative disorders. Activation of microglia was long considered detrimental for neuron survival, but more recently it has become apparent that the real scenario of microglia morphofunctional diversity is far more complex. In this review, we discuss the recent literature on the alterations in microglia phenomics in the hippocampus of animal models of normal brain aging, acute neuroinflammation, ischemia, and neurodegenerative disorders, such as AD. Microglia undergo phenomic changes consisting of transcriptional, functional, and morphological changes that transform them into cells with different properties and functions. The classical subdivision of microglia into M1 and M2, two different, all-or-nothing states is too simplistic, and does not correspond to the variety of phenotypes recently discovered in the brain. We will discuss the phenomic modifications of microglia focusing not only on the differences in microglia reactivity in the diverse models of neurodegenerative disorders, but also among different areas of the brain. For instance, in contiguous and highly interconnected regions of the rat hippocampus, microglia show a differential, finely regulated, and region-specific reactivity, demonstrating that microglia responses are not uniform, but vary significantly from area to area in response to insults. It is of great interest to verify whether the differences in microglia reactivity may explain the differential susceptibility of different brain areas to insults, and particularly the higher sensitivity of CA1 pyramidal neurons to inflammatory stimuli. Understanding the spatiotemporal heterogeneity of microglia phenomics in health and disease is of paramount importance to find new druggable targets for the development of novel microglia-targeted therapies in different CNS disorders. This will allow interventions in three different ways: (i) by suppressing the pro-inflammatory properties of microglia to limit the deleterious effect of their activation; (ii) by modulating microglia phenotypic change to favor anti-inflammatory properties; (iii) by influencing microglia priming early in the disease process.
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Affiliation(s)
- Daniele Lana
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Giada Magni
- Institute of Applied Physics “Nello Carrara”, National Research Council (IFAC-CNR), Via Madonna del Piano 10, 50019 Florence, Italy;
| | - Elisa Landucci
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Gary L. Wenk
- Department of Psychology, The Ohio State University, Columbus, OH 43210, USA;
| | - Domenico Edoardo Pellegrini-Giampietro
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
| | - Maria Grazia Giovannini
- Department of Health Sciences, Section of Clinical Pharmacology and Oncology, University of Florence, Viale Pieraccini 6, 50139 Florence, Italy; (E.L.); (D.E.P.-G.); (M.G.G.)
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Wang Z, Song Y, Bai S, Xiang W, Zhou X, Han L, Zhu D, Guan Y. Imaging of microglia in post-stroke inflammation. Nucl Med Biol 2023; 118-119:108336. [PMID: 37028196 DOI: 10.1016/j.nucmedbio.2023.108336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Revised: 03/21/2023] [Accepted: 03/21/2023] [Indexed: 04/03/2023]
Abstract
Microglia constantly survey the central nervous system microenvironment and maintain brain homeostasis. Microglia activation, polarization and inflammatory response are of great importance in the pathophysiology of ischemic stroke. For exploring biochemical processes in vivo, positron emission tomography (PET) is a superior imaging tool. Translocator protein 18 kDa (TSPO), is a validated neuroinflammatory biomarker which is widely used to evaluate various central nervous system (CNS) pathologies in both preclinical and clinical studies. TSPO level can be elevated due to peripheral inflammatory cells infiltration and glial cells activation. Therefore, a clear understanding of the dynamic changes between microglia and TSPO is critical for interpreting PET studies and understanding the pathophysiology after ischemic stroke. Our review discusses alternative biological targets that have attracted considerable interest for the imaging of microglia activation in recent years, and the potential value of imaging of microglia in the assessment of stroke therapies.
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Schaechter JD, Hightower BG, Kim M, Loggia ML. A pilot [ 11C]PBR28 PET/MRI study of neuroinflammation and neurodegeneration in chronic stroke patients. Brain Behav Immun Health 2021; 17:100336. [PMID: 34589819 DOI: 10.1016/j.bbih.2021.100336] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 08/18/2021] [Accepted: 08/21/2021] [Indexed: 11/24/2022] Open
Abstract
Neuroinflammation occurs in response to acute ischemic stroke, and has been speculated to underlie secondary poststroke pathologies, such as depression, that often develop over time poststroke. However, no study has examined whether neuroinflammation is present in chronic stroke patients (e.g., ≥ 1 year poststroke). This study tested whether neuroinflammation is present in chronic stroke patients, and is associated with neurodegeneration, using [11C]PBR28 PET and diffusion MRI. Eight patients with middle cerebral artery (MCA) ischemic stroke incurred 1–3 years prior and 16 healthy controls underwent [11C]PBR28 PET to measure glial activation and diffusion MRI to measure microstructural integrity by mean diffusivity (MD) and fractional anisotropy (FA) using an integrated PET/MRI scanner. Group differences in [11C]PBR28 binding, MD and FA were analyzed voxelwise across the whole brain excluding the infarct zone defined as voxels containing the infarct in any patient. Compared to controls, patients showed elevations in [11C]PBR28 binding in several brain regions outside the infarct zone, including regions with presumed direct neuroanatomical connections to the infarct (e.g., ipsilesional internal capsule and thalamus) and those without known direct connections (e.g., contralesional thalamus and cingulate gyrus). Patients also showed widespread elevations in MD, with a subset of these regions having reduced FA. In patients, MD was more elevated in regions with co-localized elevations in [11C]PBR28 binding than in contralateral regions without elevations in [11C]PBR28 binding. This pilot study supports the presence of extensive glial activation along with widespread loss in microstructural integrity in non-infarcted tissue in a cohort of patients with chronic MCA stroke. The loss in microstructural integrity was greater in regions with co-localized glial activation. It is possible that stroke risk factors (e.g., hypertension) contributed to these tissue changes in patients. Chronic neuroinflammation speculated to underlie secondary poststroke pathologies such as depression. Measured neuroinflammation in chronic stroke patients using [11C]PBR28 PET. First study showing extensive neuroinflammation in non-infarcted tissue in chronic stroke patients.
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Hughes JL, Beech JS, Jones PS, Wang D, Menon DK, Aigbirhio FI, Fryer TD, Baron JC. Early-stage 11C-Flumazenil PET predicts day-14 selective neuronal loss in a rodent model of transient focal cerebral ischemia. J Cereb Blood Flow Metab 2020; 40:1997-2009. [PMID: 31637947 PMCID: PMC7786851 DOI: 10.1177/0271678x19883040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Predicting tissue outcome early after stroke is an important goal. MRI >3 h accurately predicts infarction but is insensitive to selective neuronal loss (SNL). Previous studies suggest that chronic-stage 11C-flumazenil PET (FMZ-PET) is a validated marker of SNL in rats, while early-stage FMZ-PET may predict infarction. Whether early FMZ-PET also predicts SNL is unknown. Following 45-min distal MCA occlusion, adult rats underwent FMZ-PET at 1 h and 48 h post-reperfusion to map distribution volume (VT), which reflects GABA-A receptor binding. NeuN immunohistochemistry was performed at Day 14. In each rat, VT and %NeuN loss were determined in 44 ROIs spanning the hemisphere. NeuN revealed isolated SNL and cortical infarction in five and one rats, respectively. In the SNL subgroup, VT-1 h was mildly reduced and only weakly predicted SNL, while VT-48 h was significantly increased and predicted SNL both individually (p < 0.01, Kendall) and across the group (p < 0.001), i.e. the higher the VT, the stronger the SNL. Similar correlations were found in the rat with infarction. Our findings suggest GABA-A receptors are still present on injured neurons at the 48 h timepoint, and the increased 48 h VT observed here is consistent with earlier rat studies showing early GABA-A receptor upregulation. That FMZ binding at 48 h was predictive of SNL may have clinical implications.
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Affiliation(s)
- Jessica L Hughes
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - John S Beech
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, UK
| | - P Simon Jones
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Dechao Wang
- Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - David K Menon
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Cambridge, UK
| | - Franklin I Aigbirhio
- Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Tim D Fryer
- Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Jean-Claude Baron
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,Inserm U1266, Paris Descartes University, Sainte-Anne Hospital, Paris, France
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Emmrich JV, Ejaz S, Williamson DJ, Hong YT, Sitnikov S, Fryer TD, Aigbirhio FI, Wulff H, Baron JC. Assessing the Effects of Cytoprotectants on Selective Neuronal Loss, Sensorimotor Deficit and Microglial Activation after Temporary Middle Cerebral Occlusion. Brain Sci 2019; 9:E287. [PMID: 31652564 DOI: 10.3390/brainsci9100287] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/18/2019] [Accepted: 10/20/2019] [Indexed: 01/21/2023] Open
Abstract
Although early reperfusion after stroke salvages the still-viable ischemic tissue, peri-infarct selective neuronal loss (SNL) can cause sensorimotor deficits (SMD). We designed a longitudinal protocol to assess the effects of cytoprotectants on SMD, microglial activation (MA) and SNL, and specifically tested whether the KCa3.1-blocker TRAM-34 would prevent SNL. Spontaneously hypertensive rats underwent 15 min middle-cerebral artery occlusion and were randomized into control or treatment group, which received TRAM-34 intraperitoneally for 4 weeks starting 12 h after reperfusion. SMD was assessed longitudinally using the sticky-label test. MA was quantified at day 14 using in vivo [11C]-PK111195 positron emission tomography (PET), and again across the same regions-of-interest template by immunofluorescence together with SNL at day 28. SMD recovered significantly faster in the treated group (p = 0.004). On PET, MA was present in 5/6 rats in each group, with no significant between-group difference. On immunofluorescence, both SNL and MA were present in 5/6 control rats and 4/6 TRAM-34 rats, with a non-significantly lower degree of MA but a significantly (p = 0.009) lower degree of SNL in the treated group. These findings document the utility of our longitudinal protocol and suggest that TRAM-34 reduces SNL and hastens behavioural recovery without marked MA blocking at the assessed time-points.
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Kanno I, Seki C, Takuwa H, Jin ZH, Boturyn D, Dumy P, Furukawa T, Saga T, Ito H, Masamoto K. Positron emission tomography of cerebral angiogenesis and TSPO expression in a mouse model of chronic hypoxia. J Cereb Blood Flow Metab 2018; 38:687-696. [PMID: 28128020 PMCID: PMC5888851 DOI: 10.1177/0271678x16689800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The present study aimed to examine whether positron emission tomography (PET) could evaluate cerebral angiogenesis. Mice were housed in a hypoxic chamber with 8-9% oxygen for 4, 7, and 14 days, and the angiogenic responses were evaluated with a radiotracer, 64Cu-cyclam-RAFT-c(-RGDfK-)4, which targeted αVβ3 integrin and was imaged with PET. The PET imaging results showed little uptake during all of the hypoxic periods. Immunofluorescence staining of the β3 integrin, CD61, revealed weak expression, while the microvessel density assessed by CD31 staining increased with the hypoxic duration. These observations suggest that the increased vascular density originated from other types of vascular remodeling, unlike angiogenic sprouting. We then searched for any signs of vascular remodeling that could be detected using PET. PET imaging of 11C-PK11195, a marker of the 18-kDa translocator protein (TSPO), revealed a transient increase at day 4 of hypoxia. Because the immunofluorescence of glial markers showed unchanged staining over the early phase of hypoxia, the observed upregulation of TSPO expression probably originated from non-glial cells (e.g. vascular cells). In conclusion, a transient increase in TSPO probe uptake was detected with PET at only the early phase of hypoxia, which indicates an early sign of vascular remodeling induced by hypoxia.
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Affiliation(s)
- Iwao Kanno
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Chie Seki
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Hiroyuki Takuwa
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Zhao-Hui Jin
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Didier Boturyn
- 2 Département de Chimie Moléculaire, Université Grenoble Alpes, Grenoble, France
| | - Pascal Dumy
- 3 Institut des Biomolécules Max Mousseron, École Nationale Supérieure de Chimie de Montpellier, Montpellier, France
| | - Takako Furukawa
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Tsuneo Saga
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Hiroshi Ito
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
| | - Kazuto Masamoto
- 1 Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan.,4 Brain Science Inspired Life Support Research Center, University of Electro-Communications, Tokyo, Japan
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Xiang B, Xiao C, Shen T, Li X. Anti-inflammatory effects of anisalcohol on lipopolysaccharide-stimulated BV2 microglia via selective modulation of microglia polarization and down-regulation of NF-κB p65 and JNK activation. Mol Immunol 2018; 95:39-46. [DOI: 10.1016/j.molimm.2018.01.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 01/18/2018] [Accepted: 01/22/2018] [Indexed: 01/05/2023]
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Zhong YH, Dhawan J, Kovoor JA, Sullivan J, Zhang WX, Choi D, Biegon A. Aromatase and neuroinflammation in rat focal brain ischemia. J Steroid Biochem Mol Biol 2017; 174:225-233. [PMID: 28964927 DOI: 10.1016/j.jsbmb.2017.09.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 09/24/2017] [Accepted: 09/25/2017] [Indexed: 12/22/2022]
Abstract
Accumulating evidence suggests that expression of aromatase, the enzyme responsible for the conversion of androgens to estrogens, is transiently upregulated in rat stroke models. It was further suggested that increased aromatase expression is linked to neuroinflammation and that it is neuroprotective in females. Our goal was to investigate aromatase upregulation in male rats subjected to experimental stroke in relationship to neuroinflammation, infarct and response to treatment with different putative neuroprotective agents. Intact male rats were subjected to transient (90min) middle cerebral artery occlusion (MCAO) and administered selfotel (N-methyl-d-aspartic acid (NMDA) receptor competitive antagonist), TPEN (a zinc chelator), a combination of the two drugs or vehicle, injected immediately after reperfusion. Animals were killed 14days after MCAO and consecutive brain sections used to measure aromatase expression, cerebral infarct volume and neuroinflammation. Quantitative immunohistochemistry (IHC) demonstrated increased brain aromatase expression in the peri-infarct area relative to contralesional area, which was partially abrogated by neuroprotective agents. There was no correlation between aromatase expression in the peri-infarct zone and infarct volume, which was reduced by neuroprotective agents. Microglial activation, measured by quantitative autoradiography, was positively correlated with infarct and inversely correlated with aromatase expression in the peri-infarct zone. Our findings indicate that focal ischemia upregulates brain aromatase in the male rat brain at 14days post surgery, which is within the time frame documented in females. However, the lack of negative correlation between aromatase expression and infarct volume and lack of positive correlation between microgliosis and aromatase do not support a major role for aromatase as a mediator of neuroprotection or a causal relationship between microglial activation and increased aromatase expression in male focal ischemia.
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Affiliation(s)
- Yu H Zhong
- Department of Neurology, the First Affiliated Hospital of Sun Yat-Sen University, No. 58, Zhongshan Road II, Guangzhou, Guangdong Province 510080, PR China; Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
| | - Jasbeer Dhawan
- Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
| | - Joel A Kovoor
- Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
| | - John Sullivan
- Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
| | - Wei X Zhang
- Department of Neurology, the First Affiliated Hospital of Sun Yat-Sen University, No. 58, Zhongshan Road II, Guangzhou, Guangdong Province 510080, PR China.
| | - Dennis Choi
- Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
| | - Anat Biegon
- Department of Neurology, Stony Brook University, 100 Nicolls Road, Stony Brook, NY 11794-2565, USA.
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Fryer TD, Ejaz S, Jensen-Kondering U, Williamson DJ, Sitnikov S, Sawiak SJ, Aigbirhio FI, Hong YT, Baron JC. Effects of hyperoxia on 18F-fluoro-misonidazole brain uptake and tissue oxygen tension following middle cerebral artery occlusion in rodents: Pilot studies. PLoS One 2017; 12:e0187087. [PMID: 29091934 DOI: 10.1371/journal.pone.0187087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 10/15/2017] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Mapping brain hypoxia is a major goal for stroke diagnosis, pathophysiology and treatment monitoring. 18F-fluoro-misonidazole (FMISO) positron emission tomography (PET) is the gold standard hypoxia imaging method. Normobaric hyperoxia (NBO) is a promising therapy in acute stroke. In this pilot study, we tested the straightforward hypothesis that NBO would markedly reduce FMISO uptake in ischemic brain in Wistar and spontaneously hypertensive rats (SHRs), two rat strains with distinct vulnerability to brain ischemia, mimicking clinical heterogeneity. METHODS Thirteen adult male rats were randomized to distal middle cerebral artery occlusion under either 30% O2 or 100% O2. FMISO was administered intravenously and PET data acquired dynamically for 3hrs, after which magnetic resonance imaging (MRI) and tetrazolium chloride (TTC) staining were carried out to map the ischemic lesion. Both FMISO tissue uptake at 2-3hrs and FMISO kinetic rate constants, determined based on previously published kinetic modelling, were obtained for the hypoxic area. In a separate group (n = 9), tissue oxygen partial pressure (PtO2) was measured in the ischemic tissue during both control and NBO conditions. RESULTS As expected, the FMISO PET, MRI and TTC lesion volumes were much larger in SHRs than Wistar rats in both the control and NBO conditions. NBO did not appear to substantially reduce FMISO lesion size, nor affect the FMISO kinetic rate constants in either strain. Likewise, MRI and TTC lesion volumes were unaffected. The parallel study showed the expected increases in ischemic cortex PtO2 under NBO, although these were small in some SHRs with very low baseline PtO2. CONCLUSIONS Despite small samples, the apparent lack of marked effects of NBO on FMISO uptake suggests that in permanent ischemia the cellular mechanisms underlying FMISO trapping in hypoxic cells may be disjointed from PtO2. Better understanding of FMISO trapping processes will be important for future applications of FMISO imaging.
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Abstract
PURPOSE OF REVIEW This article provides an overview of the recent literature regarding the application of in-vivo brain imaging techniques to animal models of ischemic stroke. RECENT FINDINGS Major breakthroughs concerned the effects of sensory stimulation on neuronal function, local hemodynamics, and tissue outcome in the hyperacute phase of stroke; the novel application to stroke of hybrid scanners allowing simultaneous PET and magnetic resonance; the refinements of magnetic resonance-based oxygen imaging, allowing to map the ischemic penumbra in a completely noninvasive way; the implementation of new PET ligands to selectively map poststroke neuronal death and neuroinflammation; and the use of novel mesoscale imaging techniques to demonstrate the major role of interhemispheric connectivity in poststroke plasticity and functional recovery. SUMMARY The array of techniques to map in vivo the key pathophysiological brain processes involved in stroke is currently enlarging at an amazing pace. This is paralleled by ever-increasing sophistication in postprocessing tools. The combination of techniques allowing simultaneous access to several variables is particularly powerful as it affords unprecedented insights into the intimate processes underlying the tissue and neuronal changes that follow a stroke. These major leaps forward will hopefully lead to therapeutic breakthroughs aiming at improving functional outcome after stroke.
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Ejaz S, Emmrich JV, Sitnikov SL, Hong YT, Sawiak SJ, Fryer TD, Aigbirhio FI, Williamson DJ, Baron JC. Normobaric hyperoxia markedly reduces brain damage and sensorimotor deficits following brief focal ischaemia. Brain 2016; 139:751-64. [PMID: 26767570 DOI: 10.1093/brain/awv391] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 11/16/2015] [Indexed: 01/02/2023] Open
Abstract
'True' transient ischaemic attacks are characterized not only clinically, but also radiologically by a lack of corresponding changes on magnetic resonance imaging. During a transient ischaemic attack it is assumed that the affected tissue is penumbral but rescued by early spontaneous reperfusion. There is, however, evidence from rodent studies that even brief focal ischaemia not resulting in tissue infarction can cause extensive selective neuronal loss associated with long-lasting sensorimotor impairment but normal magnetic resonance imaging. Selective neuronal loss might therefore contribute to the increasingly recognized cognitive impairment occurring in patients with transient ischaemic attacks. It is therefore relevant to consider treatments to reduce brain damage occurring with transient ischaemic attacks. As penumbral neurons are threatened by markedly constrained oxygen delivery, improving the latter by increasing arterial O2 content would seem logical. Despite only small increases in arterial O2 content, normobaric oxygen therapy experimentally induces significant increases in penumbral O2 pressure and by such may maintain the penumbra alive until reperfusion. Nevertheless, the effects of normobaric oxygen therapy on infarct volume in rodent models have been conflicting, although duration of occlusion appeared an important factor. Likewise, in the single randomized trial published to date, early-administered normobaric oxygen therapy had no significant effect on clinical outcome despite reduced diffusion-weighted imaging lesion growth during therapy. Here we tested the hypothesis that normobaric oxygen therapy prevents both selective neuronal loss and sensorimotor deficits in a rodent model mimicking true transient ischaemic attack. Normobaric oxygen therapy was applied from the onset and until completion of 15 min distal middle cerebral artery occlusion in spontaneously hypertensive rats, a strain representative of the transient ischaemic attack-prone population. Whereas normoxic controls showed normal magnetic resonance imaging but extensive cortical selective neuronal loss associated with microglial activation (present both at Day 14 in vivo and at Day 28 post-mortem) and marked and long-lasting sensorimotor deficits, normobaric oxygen therapy completely prevented sensorimotor deficit (P < 0.02) and near-completely Day 28 selective neuronal loss (P < 0.005). Microglial activation was substantially reduced at Day 14 and completely prevented at Day 28 (P = 0.002). Our findings document that normobaric oxygen therapy administered during ischaemia nearly completely prevents the neuronal death, microglial inflammation and sensorimotor impairment that characterize this rodent true transient ischaemic attack model. Taken together with the available literature, normobaric oxygen therapy appears a promising therapy for short-lasting ischaemia, and is attractive clinically as it could be started at home in at-risk patients or in the ambulance in subjects suspected of transient ischaemic attack/early stroke. It may also be a straightforward adjunct to reperfusion therapies, and help prevent subtle brain damage potentially contributing to long-term cognitive and sensorimotor impairment in at-risk populations.
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Affiliation(s)
- Sohail Ejaz
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Julius V Emmrich
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK 2 Department of Neurology, Charité - Universitätsmedizin Berlin, Germany
| | - Sergey L Sitnikov
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Young T Hong
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Stephen J Sawiak
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Tim D Fryer
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Franklin I Aigbirhio
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - David J Williamson
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Jean-Claude Baron
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK 4 INSERM U894, Hôpital Sainte-Anne, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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Martín A, Szczupak B, Gómez-Vallejo V, Domercq M, Cano A, Padro D, Muñoz C, Higuchi M, Matute C, Llop J. In vivo PET imaging of the α4β2 nicotinic acetylcholine receptor as a marker for brain inflammation after cerebral ischemia. J Neurosci 2015; 35:5998-6009. [PMID: 25878273 DOI: 10.1523/JNEUROSCI.3670-14.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
PET imaging of nicotinic acetylcholine receptors (nAChRs) could become an effective tool for the diagnosis and therapy evaluation of neurologic diseases. Despite this, the role of nAChRs α4β2 receptors after brain diseases such as cerebral ischemia and its involvement in inflammatory reaction is still largely unknown. To investigate this, we performed in parallel in vivo magnetic resonance imaging (MRI) and positron emission tomography (PET) with 2[(18)F]-fluoro-A85380 and [(11)C]PK11195 at 1, 3, 7, 14, 21, and 28 d after middle cerebral artery occlusion (MCAO) in rats. In the ischemic territory, PET with 2[(18)F]-fluoro-A85380 and [(11)C]PK11195 showed a progressive binding increase from days 3-7, followed by a progressive decrease from days 14-28 after cerebral ischemia onset. Ex vivo immunohistochemistry for the nicotinic α4β2 receptor and the mitochondrial translocator protein (18 kDa) (TSPO) confirmed the PET findings and demonstrated the overexpression of α4β2 receptors in both microglia/macrophages and astrocytes from days 7-28 after experimental ischemic stroke. Likewise, the role played by α4β2 receptors on neuroinflammation was supported by the increase of [(11)C]PK11195 binding in ischemic rats treated with the α4β2 antagonist dihydro-β-erythroidine hydrobromide (DHBE) at day 7 after MCAO. Finally, both functional and behavioral testing showed major impaired outcome at day 1 after ischemia onset, followed by a recovery of the sensorimotor function and dexterity from days 21-28 after experimental stroke. Together, these results suggest that the nicotinic α4β2 receptor could have a key role in the inflammatory reaction underlying cerebral ischemia in rats.
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Ejaz S, Williamson DJ, Jensen-Kondering U, Ahmed T, Sawiak SJ, Baron JC. What is the Optimal Duration of Middle-Cerebral Artery Occlusion Consistently Resulting in Isolated Cortical Selective Neuronal Loss in the Spontaneously Hypertensive Rat? Front Neurol 2015; 6:64. [PMID: 25859239 PMCID: PMC4374627 DOI: 10.3389/fneur.2015.00064] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Accepted: 03/11/2015] [Indexed: 12/03/2022] Open
Abstract
Introduction and objectives: Selective neuronal loss (SNL) in the reperfused penumbra may impact clinical recovery and is thus important to investigate. Brief proximal middle cerebral artery occlusion (MCAo) results in predominantly striatal SNL, yet cortical damage is more relevant given its behavioral implications and that thrombolytic therapy mainly rescues the cortex. Distal temporary MCAo (tMCAo) does target the cortex, but the optimal occlusion duration that results in isolated SNL has not been determined. In the present study, we assessed different distal tMCAo durations looking for consistently pure SNL. Methods: Microclip distal tMCAo (md-tMCAo) was performed in ~6-month old male spontaneously hypertensive rats (SHRs). We previously reported that 45 min md-tMCAo in SHRs results in pan-necrosis in the majority of subjects. Accordingly, three shorter MCAo durations were investigated here in decremental succession, namely 30, 22, and 15 min (n = 3, 3, and 7 subjects, respectively). Recanalization was confirmed by MR angiography just prior to brain collection at 28 days and T2-weighted MRI was obtained for characterization of ischemic lesions. NeuN, OX42, and GFAP immunohistochemistry appraised changes in neurons, microglia, and astrocytes, respectively. Ischemic lesions were categorized into three main types: (1) pan-necrosis; (2) partial infarction; and (3) SNL. Results: Pan-necrosis or partial infarction was present in all 30 min and 22 min subjects, but not in the 15 min group (p < 0.001), in which isolated cortical SNL was consistently present. MRI revealed characteristic hyperintense abnormalities in all rats with pan-necrosis or partial infarction, but no change in any 15 min subject. Conclusion: We found that 15 min distal MCAo consistently resulted in pure cortical SNL, whereas durations equal or longer than 22 min consistently resulted in infarcts. This model may be of use to study the pathophysiology of cortical SNL and its prevention by appropriate interventions.
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Affiliation(s)
- Sohail Ejaz
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge , Cambridge , UK
| | - David J Williamson
- Department of Clinical Neurosciences, Wolfson Brain Imaging Centre, Addenbrooke's Hospital, University of Cambridge , Cambridge , UK
| | - Ulf Jensen-Kondering
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge , Cambridge , UK
| | - Tahir Ahmed
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge , Cambridge , UK
| | - Steve J Sawiak
- Department of Clinical Neurosciences, Wolfson Brain Imaging Centre, Addenbrooke's Hospital, University of Cambridge , Cambridge , UK
| | - Jean-Claude Baron
- Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge , Cambridge , UK ; INSERM U 894, Université Paris Descartes , Paris , France
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Emmrich JV, Ejaz S, Neher JJ, Williamson DJ, Baron JC. Regional distribution of selective neuronal loss and microglial activation across the MCA territory after transient focal ischemia: quantitative versus semiquantitative systematic immunohistochemical assessment. J Cereb Blood Flow Metab 2015; 35:20-7. [PMID: 25352044 PMCID: PMC4294404 DOI: 10.1038/jcbfm.2014.181] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 09/10/2014] [Accepted: 09/30/2014] [Indexed: 11/09/2022]
Abstract
Histopathologic assessment in transient middle cerebral artery occlusion (MCAo) rodent models generally lacks comprehensiveness and exposes to interobserver bias. Here we compared a novel quantitative assessment of regional infarction, selective neuronal loss (SNL) and microglial activation (MA) across the MCA territory to a previously published semiquantitative visual protocol. NeuN and OX42 immunohistochemistry was applied after either 15 or 45 minutes distal MCAo to maximize SNL and infarction, respectively. Survival times varied from 28 to 60 days to cover potential biases such as delayed tissue shrinkage. Damage was assessed using a template of 44 cytoarchitectonic regions of interest (ROIs) mapped onto a subset of digitized coronal sections spanning the MCA territory. For each ROI were obtained a semiquantitative visually determined index of histopathologic changes (method 1), and lpsilateral/contralesional ratios of remaining neurons and activated microglia cell counts (method 2). There was excellent agreement between the two methods for 28-day survival for both MCAo durations, whereas method 2 more sensitively detected subtle SNL and MA at 45 days and 60 days after 15-minute MCAo. Thus the visual method is accurate for usual degrees of ischemic damage, but absolute cell quantification is superior to detect subtle changes and should therefore be preferred in brief MCAo models, although requires optimal staining quality.
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Affiliation(s)
- Julius V Emmrich
- 1] Department of Clinical Neurosciences, Stroke Research Group, University of Cambridge, Cambridge, UK [2] Department of Neurology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Sohail Ejaz
- Department of Clinical Neurosciences, Stroke Research Group, University of Cambridge, Cambridge, UK
| | - Jonas J Neher
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - David J Williamson
- 1] Department of Clinical Neurosciences, Stroke Research Group, University of Cambridge, Cambridge, UK [2] Department of Clinical Neurosciences, Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, UK
| | - Jean-Claude Baron
- 1] Department of Clinical Neurosciences, Stroke Research Group, University of Cambridge, Cambridge, UK [2] INSERM U894, Hôpital Sainte-Anne, Université Paris Descartes/Sorbonne Paris Cité, Paris, France
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Boutin H, Murray K, Pradillo J, Maroy R, Smigova A, Gerhard A, Jones PA, Trigg W. 18F-GE-180: a novel TSPO radiotracer compared to 11C-R-PK11195 in a preclinical model of stroke. Eur J Nucl Med Mol Imaging 2015; 42:503-11. [PMID: 25351507 DOI: 10.1007/s00259-014-2939-8] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 10/08/2014] [Indexed: 12/14/2022]
Abstract
PURPOSE Neuroinflammation plays a critical role in various neuropathological conditions, and hence there is renewed interest in the translocator protein (TSPO) as a biomarker of microglial activation and macrophage infiltration in the brain. This is reflected in the large amount of research conducted seeking to replace the prototypical PET radiotracer (11)C-R-PK11195 with a TSPO ligand with higher performance. Here we report the in vivo preclinical investigation of the novel TSPO tracer (18)F-GE-180 in a rat model of stroke. METHODS Focal cerebral ischaemia was induced in Wistar rats by 60-min occlusion of the middle cerebral artery (MCAO). Brain damage was assessed 24 h after MCAO by T2 MRI. Rats were scanned with (11)C-R-PK11195 and (18)F-GE-180 5 or 6 days after MCAO. Specificity of binding was confirmed by injection of unlabelled R-PK11195 or GE-180 20 min after injection of (18)F-GE-180. In vivo data were confirmed by ex vivo immunohistochemistry for microglial (CD11b) and astrocytic biomarkers (GFAP). RESULTS (18)F-GE-180 uptake was 24 % higher in the core of the ischaemic lesion and 18 % lower in the contralateral healthy tissue than that of (11)C-R-PK11195 uptake (1.5 ± 0.2-fold higher signal to noise ratio). We confirmed this finding using the simplified reference tissue model (BPND = 3.5 ± 0.4 and 2.4 ± 0.5 for (18)F-GE-180 and (11)C-R-PK11195, respectively, with R 1 = 1). Injection of unlabelled R-PK11195 or GE-180 20 min after injection of (18)F-GE-180 significantly displaced (18)F-GE-180 (69 ± 5 % and 63 ± 4 %, respectively). Specificity of the binding was also confirmed by in vitro autoradiography, and the location and presence of activated microglia and infiltrated macrophages were confirmed by immunohistochemistry. CONCLUSION The in vivo binding characteristics of (18)F-GE-180 demonstrate a better signal to noise ratio than (11)C-R-PK11195 due to both a better signal in the lesion and lower nonspecific binding in healthy tissue. These results provide evidence that (18)F-GE-180 is a strong candidate to replace (11)C-R-PK11195.
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Heiss WD. PET imaging in ischemic cerebrovascular disease: current status and future directions. Neurosci Bull 2014; 30:713-32. [PMID: 25138055 DOI: 10.1007/s12264-014-1463-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/10/2014] [Indexed: 01/08/2023] Open
Abstract
Cerebrovascular diseases are caused by interruption or significant impairment of the blood supply to the brain, which leads to a cascade of metabolic and molecular alterations resulting in functional disturbance and morphological damage. These pathophysiological changes can be assessed by positron emission tomography (PET), which permits the regional measurement of physiological parameters and imaging of the distribution of molecular markers. PET has broadened our understanding of the flow and metabolic thresholds critical for the maintenance of brain function and morphology: in this application, PET has been essential in the transfer of the concept of the penumbra (tissue with perfusion below the functional threshold but above the threshold for the preservation of morphology) to clinical stroke and thereby has had great impact on developing treatment strategies. Radioligands for receptors can be used as early markers of irreversible neuronal damage and thereby can predict the size of the final infarcts; this is also important for decisions concerning invasive therapy in large ("malignant") infarctions. With PET investigations, the reserve capacity of blood supply to the brain can be tested in obstructive arteriosclerosis of the supplying arteries, and this again is essential for planning interventions. The effect of a stroke on the surrounding and contralateral primarily unaffected tissue can be investigated, and these results help to understand the symptoms caused by disturbances in functional networks. Chronic cerebrovascular disease causes vascular cognitive disorders, including vascular dementia. PET permits the detection of the metabolic disturbances responsible for cognitive impairment and dementia, and can differentiate vascular dementia from degenerative diseases. It may also help to understand the importance of neuroinflammation after stroke and its interaction with amyloid deposition in the development of dementia. Although the clinical application of PET investigations is limited, this technology had and still has a great impact on research into cerebrovascular diseases.
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Baron JC, Yamauchi H, Fujioka M, Endres M. Selective neuronal loss in ischemic stroke and cerebrovascular disease. J Cereb Blood Flow Metab 2014; 34:2-18. [PMID: 24192635 DOI: 10.1038/jcbfm.2013.188] [Citation(s) in RCA: 159] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 10/15/2013] [Accepted: 10/17/2013] [Indexed: 01/23/2023]
Abstract
As a sequel of brain ischemia, selective neuronal loss (SNL)-as opposed to pannecrosis (i.e. infarction)-is attracting growing interest, particularly because it is now detectable in vivo. In acute stroke, SNL may affect the salvaged penumbra and hamper functional recovery following reperfusion. Rodent occlusion models can generate SNL predominantly in the striatum or cortex, showing that it can affect behavior for weeks despite normal magnetic resonance imaging. In humans, SNL in the salvaged penumbra has been documented in vivo mainly using positron emission tomography and (11)C-flumazenil, a neuronal tracer validated against immunohistochemistry in rodent stroke models. Cortical SNL has also been documented using this approach in chronic carotid disease in association with misery perfusion and behavioral deficits, suggesting that it can result from chronic or unstable hemodynamic compromise. Given these consequences, SNL may constitute a novel therapeutic target. Selective neuronal loss may also develop at sites remote from infarcts, representing secondary 'exofocal' phenomena akin to degeneration, potentially related to poststroke behavioral or mood impairments again amenable to therapy. Further work should aim to better characterize the time course, behavioral consequences-including the impact on neurological recovery and contribution to vascular cognitive impairment-association with possible causal processes such as microglial activation, and preventability of SNL.
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Cumming P. PET Neuroimaging: The White Elephant Packs His Trunk? Neuroimage 2014; 84:1094-100. [DOI: 10.1016/j.neuroimage.2013.08.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 08/07/2013] [Accepted: 08/11/2013] [Indexed: 01/30/2023] Open
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Abstract
Sepsis-associated encephalopathy (SAE) refers to a clinical spectrum of acute neurological dysfunction that arises in the context of sepsis. Although the pathophysiology of SAE is incompletely understood, it is thought to involve endothelial activation, blood-brain barrier leakage, inflammatory cell migration, and neuronal loss with neurotransmitter imbalance. SAE is associated with a high risk of mortality. Imaging studies using MRI and CT have demonstrated changes in the brains of patients with SAE that are also seen in disorders such as stroke. Next-generation imaging techniques such as magnetic resonance spectroscopy, diffusion tensor imaging and PET, as well as experimental imaging modalities, provide options for early identification of patients with SAE, and could aid in identification of pathophysiological processes that represent possible therapeutic targets. In this Review, we explore the recent literature on imaging in SAE, relating the findings of these studies to pathological data and experimental studies to obtain insights into the pathophysiology of sepsis-associated neurological dysfunction. Furthermore, we suggest how novel imaging technologies can be used for early-stage proof-of-concept and proof-of-mechanism translational studies, which may help to improve diagnosis in SAE.
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Affiliation(s)
- Daniel J Stubbs
- Division of Anaesthesia, Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK
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Tobinick E. Author's reply to Page: "Selective TNF inhibition for chronic stroke and traumatic brain injury: an observational study involving 629 consecutive patients treated with perispinal etanercept". CNS Drugs 2013; 27:399-402. [PMID: 23580177 DOI: 10.1007/s40263-013-0058-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Imamoto N, Momosaki S, Fujita M, Omachi S, Yamato H, Kimura M, Kanegawa N, Shinohara S, Abe K. [11C]PK11195 PET imaging of spinal glial activation after nerve injury in rats. Neuroimage 2013; 79:121-8. [PMID: 23611861 DOI: 10.1016/j.neuroimage.2013.04.039] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 03/01/2013] [Accepted: 04/15/2013] [Indexed: 01/13/2023] Open
Abstract
The role of glial activation has been implicated in the development and persistence of neuropathic pain after nerve injury by recent studies. PK11195 binding to the translocator protein 18kDa (TSPO) has been shown to be enhanced in activated microglia. This study was designed to assess PK11195 imaging in spinal microglia during activation after nerve injury. The development of neuropathic pain was induced by partial sciatic nerve ligation (PSL). PSL rats on days 7 and 14 after nerve injury were subjected to imaging with a small-animal positron emission tomography/computed tomography (PET/CT) scanner using [(11)C]PK11195 to detect spinal microglial activation by means of noninvasive in vivo imaging. Spinal [(3)H]PK11195 autoradiography was performed to confirm the results of [(11)C]PK11195 PET in PSL rats. Quantitative RT-PCR of CD11b and GFAP mRNA, and the immunohistochemistry of Iba1 and GFAP were investigated to detect activated microglia and astrocytes. Mechanical allodynia was observed in the ipsilateral paw of PSL rats from day 3 after nerve injury and stably persisted from days 7 to 14. PET/CT fusion images clearly showed large amounts of accumulation of [(11)C]PK11195 in the lumbar spinal cord on days 7 and 14 after nerve injury. [(11)C]PK11195 enhanced images were restricted to the L3-L6 area of the spinal cord. The standardized uptake value (SUV) of [(11)C]PK11195 was significantly increased in the lumbar spinal cord compared to that of the thoracic region. Increased specific binding of [(11)C]PK11195 to TSPO in the spinal cord of PSL rats was confirmed by competition studies using unlabeled (R, S)-PK11195. Increased [(3)H]PK11195 binding was also observed in the ipsilateral dorsal horn of the L3-L6 spinal cord on days 7 and 14 after nerve injury. CD11b mRNA and Iba1 immunoreactive cells increased significantly on days 7 and 14 after nerve injury by PSL. However, changes in GFAP mRNA and immunoreactivity were slight in the ipsilateral side of PSL rats. In the present study, we showed that glial activation could be quantitatively imaged in the spinal cord of neuropathic pain rats using [(11)C]PK11195 PET, suggesting that high resolution PET using TSPO-specific radioligands might be useful for imaging to assess the role of glial activation, including neuroinflammatory processes, in neuropathic pain patients.
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Affiliation(s)
- Natsumi Imamoto
- Department of Innovative Drug Discovery Technologies, Innovative Drug Discovery Research Laboratories, Shionogi & Co, Ltd, Osaka, Japan.
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Williamson DJ, Ejaz S, Sitnikov S, Fryer TD, Sawiak SJ, Burke P, Baron JC, Aigbirhio FI. A comparison of four PET tracers for brain hypoxia mapping in a rodent model of stroke. Nucl Med Biol 2013; 40:338-44. [PMID: 23294900 DOI: 10.1016/j.nucmedbio.2012.11.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 10/31/2012] [Accepted: 11/23/2012] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Severe brain hypoxia in the territory of the occluded artery is a key feature of ischemic stroke. This region can be imaged using positron emission tomography (PET) and the standard hypoxia radiotracer (18)F-fluoromisonidazole ((18)F-FMISO). However, the utility of (18)F-FMISO is limited by its slow accumulation in the lesion. Therefore, this study investigated three hypoxia-sensitive radiotracers, namely the nitroimidazole (18)F-fluoroazomycin arabinoside ((18)F-FAZA) and two (64)Cu bis(thiosemicarbazone) complexes ((64)Cu-ATSM and (64)Cu-ATSE), expected to have improved pharmacokinetic profiles relative to (18)F-FMISO, in a rodent model of ischemic stroke. METHODS In anaesthetised Wistar rats, the distal middle cerebral artery was permanently occluded by electrocoagulation, the radiotracers administered intravenously and animals PET scanned for up to 3hours, followed by T2-weighted magnetic resonance imaging to map the infarct. RESULTS As expected, late and prominent (18)F-FMISO retention was observed despite lower tracer delivery into the affected region. Time-activity curves revealed that both (64)Cu-ATSM and (64)Cu-ATSE showed rapid entry and efflux from the brain, but did not show significant accumulation in the lesion. (18)F-FAZA showed limited brain penetration, and accumulation in the lesion was inconsistent, low and as slow as (18)F-FMISO. CONCLUSIONS This study suggests further development of these radiotracers as hypoxia markers for ischemic stroke may not be warranted.
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Ejaz S, Williamson DJ, Ahmed T, Sitnikov S, Hong YT, Sawiak SJ, Fryer TD, Aigbirhio FI, Baron JC. Characterizing infarction and selective neuronal loss following temporary focal cerebral ischemia in the rat: a multi-modality imaging study. Neurobiol Dis 2012; 51:120-32. [PMID: 23146994 DOI: 10.1016/j.nbd.2012.11.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 10/05/2012] [Accepted: 11/01/2012] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Current models dictate that, depending on occurrence of early reperfusion, the ischemic penumbra either undergoes or escapes infarction (i.e., "pan-necrosis"). However, tissue outcome following temporary middle-cerebral artery occlusion (tMCAo) in rodents can also include selective neuronal loss (SNL), which even if subtle may impede functional recovery. In order to explore the pathophysiology of ischemic stroke, determine potential therapeutic targets and monitor effects of therapy, in vivo imaging surrogates of these varied histopathological outcomes applicable in the clinical setting would be useful. Although hyperintense signal on T(2)-weighted MRI in the chronic post-stroke stage is considered a reliable surrogate of tissue infarction, SNL is not associated with T(2)W abnormal signal. In the clinical setting, the neuron-specific PET ligand (11)C-flumazenil (FMZ) has been used to identify both pan-necrosis and peri-infarct SNL, but this inference has not been histopathological confirmed so far. Here we investigated the late tissue sequelae of tMCAo in the rodent using in vivo T(2)W MRI and FMZ-PET against post mortem immunohistochemistry as gold standard. METHODS Adult spontaneously hypertensive rats (SHRs) underwent 45 min distal-clip middle-cerebral artery occlusion and, 28 days later, FMZ-PET and T(2)W-MRI, immediately followed by immunohistochemistry for neuronal loss (NeuN), activated microglia and astrocytosis. Based on standard histopathological definitions, ischemic lesions were classified into pan-necrosis, partial infarction or SNL. NeuN changes and FMZ binding across the whole hemisphere were quantified in the same set of 44 regions-of-interest according to previously validated protocols; linear regressions between these two measures were carried out both within and across subjects. RESULTS Both cortical pan-necrosis/partial infarction and SNL were present in all rats except one, where SNL was isolated and extensive. Infarction/partial infarction, but not SNL, was associated with T(2)W hyperintense signals and cortical atrophy. In contrast, FMZ binding was decreased in all types of lesions including SNL, in proportion with NeuN staining intensity both within (p<0.05 to <0.001) and across (p<0.001) subjects, including the subject that showed pure SNL (p=0.01). CONCLUSION This novel study revealed three main facts: i) long-term histopathological cortical changes following 45 min tMCAo in SHRs included all three of SNL, partial infarction and frank infarction; ii) T2W MRI showed conspicuous high signal lesions for complete or partial infarction, but no changes for SNL; and iii) FMZ-PET was sensitive to all three types of tMCAo-induced histopathological changes, including isolated SNL, suggesting it is a valid surrogate for the histological sequelae of focal cerebral ischemia. In addition, the finding of almost universal completed cortical infarction at 28 days differed from our previous findings at 14-day survival using the same model and rat strain, where SNL was the almost exclusive outcome, possibly representing delayed infarct maturation. Prospective studies are needed to investigate this interesting possibility.
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Affiliation(s)
- Sohail Ejaz
- Stroke Research Group, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK
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Palomero-Gallagher N, Schleicher A, Bidmon HJ, Pannek HW, Hans V, Gorji A, Speckmann EJ, Zilles K. Multireceptor analysis in human neocortex reveals complex alterations of receptor ligand binding in focal epilepsies. Epilepsia 2012; 53:1987-97. [DOI: 10.1111/j.1528-1167.2012.03634.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Gulyás B, Tóth M, Schain M, Airaksinen A, Vas Á, Kostulas K, Lindström P, Hillert J, Halldin C. Evolution of microglial activation in ischaemic core and peri-infarct regions after stroke: A PET study with the TSPO molecular imaging biomarker [ C]vinpocetine. J Neurol Sci 2012; 320:110-7. [DOI: 10.1016/j.jns.2012.06.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 05/03/2012] [Accepted: 06/23/2012] [Indexed: 01/17/2023]
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Virdee K, Cumming P, Caprioli D, Jupp B, Rominger A, Aigbirhio FI, Fryer TD, Riss PJ, Dalley JW. Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders. Neurosci Biobehav Rev 2012; 36:1188-216. [PMID: 22342372 DOI: 10.1016/j.neubiorev.2012.01.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/26/2012] [Accepted: 01/31/2012] [Indexed: 01/08/2023]
Abstract
Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.
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Affiliation(s)
- Kanwar Virdee
- Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, CB2 3EB, UK
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