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Marques TR, Ashok AH, Pillinger T, Veronese M, Turkheimer FE, Dazzan P, Sommer IE, Howes OD. Neuroinflammation in schizophrenia: meta-analysis of in vivo microglial imaging studies. Psychol Med 2019; 49:2186-2196. [PMID: 30355368 PMCID: PMC6366560 DOI: 10.1017/s0033291718003057] [Citation(s) in RCA: 135] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/24/2018] [Accepted: 09/25/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND Converging lines of evidence implicate an important role for the immune system in schizophrenia. Microglia are the resident immune cells of the central nervous system and have many functions including neuroinflammation, axonal guidance and neurotrophic support. We aimed to provide a quantitative review of in vivo PET imaging studies of microglia activation in patients with schizophrenia compared with healthy controls. METHODS Demographic, clinical and imaging measures were extracted from each study and meta-analysis was conducted using a random-effects model (Hedge's g). The difference in 18-kDa translocator protein (TSPO) binding between patients with schizophrenia and healthy controls, as quantified by either binding potential (BP) or volume of distribution (VT), was used as the main outcome. Sub-analysis and sensitivity analysis were carried out to investigate the effects of genotype, ligand and illness stage. RESULTS In total, 12 studies comprising 190 patients with schizophrenia and 200 healthy controls met inclusion criteria. There was a significant elevation in tracer binding in schizophrenia patients relative to controls when BP was used as an outcome measure, (Hedge's g = 0.31; p = 0.03) but no significant differences when VT was used (Hedge's g = -0.22; p = 0.29). CONCLUSIONS In conclusion, there is evidence for moderate elevations in TSPO tracer binding in grey matter relative to other brain tissue in schizophrenia when using BP as an outcome measure, but no difference when VT is the outcome measure. We discuss the relevance of these findings as well as the methodological issues that may underlie the contrasting difference between these outcomes.
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Affiliation(s)
- Tiago Reis Marques
- Psychiatric Imaging Group, MRC Clinical Sciences Centre, Du Cane Road, London W12 0NN, UK
- Psychiatric Imaging Group, London Institute of Medical Sciences (LMS), Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
| | - Abhishekh H Ashok
- Psychiatric Imaging Group, MRC Clinical Sciences Centre, Du Cane Road, London W12 0NN, UK
- Psychiatric Imaging Group, London Institute of Medical Sciences (LMS), Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
| | - Toby Pillinger
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
| | - Mattia Veronese
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
| | - Federico E. Turkheimer
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
| | - Paola Dazzan
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
| | - Iris E.C. Sommer
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Oliver D Howes
- Psychiatric Imaging Group, MRC Clinical Sciences Centre, Du Cane Road, London W12 0NN, UK
- Psychiatric Imaging Group, London Institute of Medical Sciences (LMS), Faculty of Medicine, Imperial College London, Du Cane Road, London W12 0NN, UK
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, UK
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TSPO in diverse CNS pathologies and psychiatric disease: A critical review and a way forward. Pharmacol Ther 2018; 194:44-58. [PMID: 30189290 DOI: 10.1016/j.pharmthera.2018.09.003] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The use of Translocator Protein 18 kDa (TSPO) as a clinical neuroimaging biomarker of brain injury and neuroinflammation has increased exponentially in the last decade. There has been a furious pace in the development of new radiotracers for TSPO positron emission tomography (PET) imaging and its use has now been extensively described in many neurological and mental disorders. This fast pace of research and the ever-increasing number of new laboratories entering the field often times lack an appreciation of the historical perspective of the field and introduce dogmatic, but unproven facts, related to the underlying neurobiology of the TSPO response to brain injury and neuroinflammation. Paradoxically, while in neurodegenerative disorders and in all types of CNS pathologies brain TSPO levels increase, a new observation in psychiatric disorders such as schizophrenia is decreased brain levels of TSPO measured by PET. The neurobiological bases for this new finding is currently not known, but rigorous experimental design using multiple experimental approaches and careful interpretation of results is critically important to provide the methodological and/or biological underpinnings to this new observation. This review provides a perspective of the early history of validating TSPO as a biomarker of brain injury and neuroinflammation and a critical analysis of controversial topics in the literature related to the cellular sources of the TSPO response. The latter is important in order to provide the correct interpretation of PET studies in neurodegenerative and psychiatric disorders. Furthermore, this review proposes some yet to be explored explanations to new findings in psychiatric disorders and new approaches to quantitatively assess the glial sources of the TSPO response in order to move the field forward.
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Expression and purification of the mammalian translocator protein for structural studies. PLoS One 2018; 13:e0198832. [PMID: 29897975 PMCID: PMC5999236 DOI: 10.1371/journal.pone.0198832] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 05/26/2018] [Indexed: 11/19/2022] Open
Abstract
The translocator protein (TSPO) is an 18 kDa polytopic membrane protein of the outer mitochondrial membrane, abundantly present in the steroid-synthesising cells. TSPO has been linked to a number of disorders, and it is recognised as a promising drug target with a range of potential medical applications. Structural and biochemical characterisation of a mammalian TSPO requires expression and purification of the protein of high quality in sufficiently large quantities. Here we describe detailed procedures for heterologous expression and purification of mammalian TSPO in HEK293 cells. We demonstrate that the established procedures can be used for untagged TSPO as well as for C-terminally fused TSPO constructs. Our protocol can be routinely used to generate high-quality TSPO preparations for biochemical and structural studies.
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Barichello T, Simões LR, Collodel A, Giridharan VV, Dal-Pizzol F, Macedo D, Quevedo J. The translocator protein (18 kDa) and its role in neuropsychiatric disorders. Neurosci Biobehav Rev 2017; 83:183-199. [DOI: 10.1016/j.neubiorev.2017.10.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/20/2017] [Accepted: 10/10/2017] [Indexed: 02/08/2023]
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Marazziti D, Dell'Osso B, Baroni S, Masala I, Di Nasso E, Giannaccini G, Conti L. Decreased density of peripheral benzodiazepine receptors in psychiatric patients after a suicide attempt. Life Sci 2005; 77:3268-75. [PMID: 16014308 DOI: 10.1016/j.lfs.2005.04.031] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Accepted: 04/01/2005] [Indexed: 12/15/2022]
Abstract
To date, two main types of benzodiazepine (BDZ) receptors have been identified: one of these is the so-called central receptor which is found mainly in the cortex, limbic areas and cerebellum, and the other is known as the peripheral receptor, which is found in the kidneys, lungs, ovaries, testes, adrenal glands and blood cells, but is present also in the central nervous system (CNS), in particular in glial cells. Although for some time the peripheral BDZ receptor has been considered an acceptor site with no pharmacological activity, recent data have suggested that it may be involved in a variety of actions, such as the response to stress. The presence of these receptors in blood platelets, which are considered a reliable, peripheral mirror of the same structures located in the SNC, prompted us to evaluate them in a group of psychiatric patients after a suicide attempt, as compared with healthy control subjects, by means of the specific binding of 3H-PK 11195. Suicide, with no doubt, may be considered one of the most stressful situations occurring to humans. The results showed the presence of a significant decrease in the density of 3H-PK 11195 binding sites in the patients, as compared with healthy control subjects. This finding may represent a non-specific indicator of a condition of stress, since peripheral BDZ receptors are modulated by stress and hormones, or it may result more from an abnormal metabolism of steroid substances which could play a pivotal role in the development of vulnerability towards suicide.
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Affiliation(s)
- Donatella Marazziti
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, University of Pisa, via Roma, 67 I-56100 Pisa, Italy.
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Marazziti D, Dell'Osso B, Baroni S, Masala I, Nasso ED, Giannaccini G, Dell'Osso L. Changes in peripheral benzodiazepine receptors in patients with bipolar disorder. Neuropsychiatr Dis Treat 2005; 1:151-4. [PMID: 18568060 PMCID: PMC2413195 DOI: 10.2147/nedt.1.2.151.61046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Peripheral benzodiazepine (BDZ) receptors were investigated by means of the binding of the specific ligand (3)H-PK 11195 to platelet membranes in patients suffering from bipolar disorder and in healthy controls. The results showed that the density (Bmax) of peripheral BDZ receptors was significantly higher in patients than in control subjects, with no change in the dissociation constant. No correlation with demographic or clinical features was observed. These findings would suggest that alterations of peripheral BDZ receptors are present in patients suffering from bipolar disorder, but it is premature to conclude whether they may be related to the pathophysiology of the disorder, or are secondary to changes occurring in other systems, such as those regulating the stress response.
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Affiliation(s)
- Donatella Marazziti
- Dipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie University of Pisa Pisa, Italy.
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Niu N, Rice SR, Heston LL, Sobell JL. Multiple missense mutations in the diazepam binding inhibitor (DBI) gene identified in schizophrenia but lack of disease association. Am J Med Genet B Neuropsychiatr Genet 2004; 125B:10-9. [PMID: 14755437 DOI: 10.1002/ajmg.b.20102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The diazepam binding inhibitor (DBI), alternatively known as the acyl-CoA binding protein (ACBP), is involved in multiple biological actions. The polypeptide binds to the peripheral, or mitochondrial, benzodiazepine receptor and facilitates transport of cholesterol to the inner membrane to stimulate steroid synthesis. Through this action, DBI indirectly modulates gamma-aminobutyric acid (GABA)-mediated inhibitory neurotransmission. DBI can be postulated as a candidate gene for psychiatric phenotypes including anxiety, mood, and psychotic disorders. In an examination of the DBI gene among 112 individuals with schizophrenia, our laboratory has identified 18 novel single nucleotide polymorphisms (SNPs), including three missense changes in conserved amino acids, a coding region microdeletion, and multiple SNPs in the putative promoter region. Case-control association analyses were performed for the missense changes, but none was found to be significantly associated with disease.
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Affiliation(s)
- N Niu
- Division of Molecular Medicine, City of Hope National Medical Center, Duarte, California, USA
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Ritsner M, Modai I, Gibel A, Leschiner S, Silver H, Tsinovoy G, Weizman A, Gavish M. Decreased platelet peripheral-type benzodiazepine receptors in persistently violent schizophrenia patients. J Psychiatr Res 2003; 37:549-56. [PMID: 14563387 DOI: 10.1016/s0022-3956(03)00055-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Peripheral-type benzodiazepine receptors (PBR) have been shown to be sensitive to stressful conditions. This study aimed to explore a possible association of platelets PBR binding with aggressive behavior and homicidal history in schizophrenia patients. The authors compared [(3)H] PK 11195 binding to platelet membrane among 11 currently aggressive schizophrenia patients, 15 schizophrenia patients with homicidal history, 14 nonaggressive schizophrenia patients, and 15 healthy volunteers. Subjects were assessed for aggressive behavior, psychopathology, anxiety, anger, and emotional distress using standardized instruments. We found that currently aggressive patients had significantly lower (-30%) platelet PBR density (B(max)), and scored significantly higher on hostility, anxiety, state anger, and emotional distress compared to homicidal and nonaggressive schizophrenia patients and healthy controls. Predominance of positive or negative symptoms, homicidal or suicidal attempt history, emotional distress levels, and conventional or atypical antipsychotic therapy is not associated with the expression of platelet PBR binding sites. Significant negative correlations emerged between PBR density and scores for aggressive behavior, hostility and anxiety. Thus, decreased platelet PBR density in aggressive schizophrenia patients is associated with higher scores for overt aggression, hostility and anxiety, but independent of illness subtype, homicidal and suicidal attempt history, distress level and type of antipsychotic treatment.
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Affiliation(s)
- Michael Ritsner
- Sha'ar Menashe Mental Health Center, Mobile Post Hefer 38814, Israel.
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Lee KH, Williams LM, Breakspear M, Gordon E. Synchronous gamma activity: a review and contribution to an integrative neuroscience model of schizophrenia. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2003; 41:57-78. [PMID: 12505648 DOI: 10.1016/s0165-0173(02)00220-5] [Citation(s) in RCA: 368] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Synchronous high frequency (Gamma band) activity has been proposed as a candidate mechanism for the integration or 'binding' of distributed brain activities. Since the first descriptions of schizophrenia, attempts to characterize this disorder have focused on disturbances in such integrative processing. Here, we review both micro- and macroscopic neuroscience research into Gamma synchrony, and its application to understanding schizophrenia. The review encompasses evidence from both animal and human studies for the functional significance of Gamma activity, the association between Gamma dysfunction and information processing disturbances, and the relevance of specific Gamma dysfunctions to the integration and extension of previous disconnection models of schizophrenia. Attention is given to the relationship between Gamma activity and the heterogeneous symptoms of schizophrenia. Existing studies show that measures of Gamma activity have the potential to explain far more of the variance in schizophrenia performance than previous neurophysiological measures. It is concluded that measures of Gamma synchrony offer a valuable window into the core integrative disturbance in schizophrenia cognition.
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Affiliation(s)
- Kwang-Hyuk Lee
- Cognitive Neuroscience Unit, Department of Psychology, University of Sydney, and The Brain Dynamics Centre, Westmead Hospital, 2145, Sydney, NSW, Australia
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Daly RC, Schmidt PJ, Davis CL, Danaceau MA, Rubinow DR. Effects of gonadal steroids on peripheral benzodiazepine receptor density in women with PMS and controls. Psychoneuroendocrinology 2001; 26:539-49. [PMID: 11403976 DOI: 10.1016/s0306-4530(01)00005-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND GABA receptor-modifying neurosteroids may play a role in premenstrual syndrome (PMS). The peripheral benzodiazepine receptor (PBR) both regulates the formation of neurosteroids and is, in animals, regulated by ovarian steroids. Alterations in PBR density have been observed in association with several psychiatric disorders. METHODS We examined the effects of gonadal steroids on lymphocytic PBR density in nine women with prospectively confirmed PMS and nine controls. PBR densities were measured during three pharmacologically controlled conditions: gonadotropin releasing hormone agonist (Lupron)-induced hypogonadism, Lupron plus estradiol, and Lupron plus progesterone replacement. Blood samples were obtained after six weeks of Lupron alone and after 3-4 weeks of estradiol and progesterone replacement. RESULTS No significant hormone state-related changes in PBR density were observed (ANOVA-R: phase-F(2,32)=1.5, P=0.2). Despite mood symptom development in the subjects with PMS, PBR density did not differ in women with PMS compared to controls across hormonal states (ANOVA-R: F(1,16)=0.6, P=0.4). CONCLUSIONS PBR densities are not altered in women with PMS and are not changed significantly by selective gonadal steroid administration. Changes in PBR density would not appear to underlie the differential sensitivity to the mood destabilizing effects of ovarian steroids in PMS.
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Affiliation(s)
- R C Daly
- Behavioral Endocrinology Branch, National Institute of Mental Health, Bldg. 10, Room 3N238, 10 Center Dr MSC 1276, Bethesda, MD 20892-1276, USA.
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