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GRT-X, which targets both the mitochondrial translocator protein (TSPO) and the Kv7.2/3 (KCNQ2/3) potassium channels, has been shown to efficiently promote recovery from cervical spine injury. In the present work, we investigate the role of GRT-X and its two targets in the axonal growth of dorsal root ganglion (DRG) neurons. Neurite outgrowth was quantified in DRG explant cultures prepared from wild-type C57BL6/J and TSPO-KO mice. TSPO was pharmacologically targeted with the agonist XBD173 and the Kv7 channels with the activator ICA-27243 and the inhibitor XE991. GRT-X efficiently stimulated DRG axonal growth at 4 and 8 days after its single administration. XBD173 also promoted axonal elongation, but only after 8 days and its repeated administration. In contrast, both ICA27243 and XE991 tended to decrease axonal elongation. In dissociated DRG neuron/Schwann cell co-cultures, GRT-X upregulated the expression of genes associated with axonal growth and myelination. In the TSPO-KO DRG cultures, the stimulatory effect of GRT-X on axonal growth was completely lost. However, GRT-X and XBD173 activated neuronal and Schwann cell gene expression after TSPO knockout, indicating the presence of additional targets warranting further investigation. These findings uncover a key role of the dual mode of action of GRT-X in the axonal elongation of DRG neurons. [ABSTRACT FROM AUTHOR]

There is an increasing accumulation of data on the exceptional importance of mitochondria in the occurrence and treatment of cancer, and in all lines of evidence for such participation, there are both energetic and non-bioenergetic functional features of mitochondria. This analytical review examines three specific features of adaptive mitochondrial changes in several malignant tumors. The first feature is characteristic of solid tumors, whose cells are forced to rebuild their energetics due to the absence of oxygen, namely, to activate the fumarate reductase pathway instead of the traditional succinate oxidase pathway that exists in aerobic conditions. For such a restructuring, the presence of a low-potential quinone is necessary, which cannot ensure the conventional conversion of succinate into fumarate but rather enables the reverse reaction, that is, the conversion of fumarate into succinate. In this scenario, complex I becomes the only generator of energy in mitochondria. The second feature is the increased proliferation in aggressive tumors of the so-called mitochondrial (peripheral) benzodiazepine receptor, also called translocator protein (TSPO) residing in the outer mitochondrial membrane, the function of which in oncogenic transformation stays mysterious. The third feature of tumor cells is the enhanced retention of certain molecules, in particular mitochondrially directed cations similar to rhodamine 123, which allows for the selective accumulation of anticancer drugs in mitochondria. These three features of mitochondria can be targets for the development of an anti-cancer strategy. [ABSTRACT FROM AUTHOR]

GRT-X, which targets both the mitochondrial translocator protein (TSPO) and the Kv7.2/3 (KCNQ2/3) potassium channels, has been shown to efficiently promote recovery from cervical spine injury. In the present work, we investigate the role of GRT-X and its two targets in the axonal growth of dorsal root ganglion (DRG) neurons. Neurite outgrowth was quantified in DRG explant cultures prepared from wild-type C57BL6/J and TSPO-KO mice. TSPO was pharmacologically targeted with the agonist XBD173 and the Kv7 channels with the activator ICA-27243 and the inhibitor XE991. GRT-X efficiently stimulated DRG axonal growth at 4 and 8 days after its single administration. XBD173 also promoted axonal elongation, but only after 8 days and its repeated administration. In contrast, both ICA27243 and XE991 tended to decrease axonal elongation. In dissociated DRG neuron/Schwann cell co-cultures, GRT-X upregulated the expression of genes associated with axonal growth and myelination. In the TSPO-KO DRG cultures, the stimulatory effect of GRT-X on axonal growth was completely lost. However, GRT-X and XBD173 activated neuronal and Schwann cell gene expression after TSPO knockout, indicating the presence of additional targets warranting further investigation. These findings uncover a key role of the dual mode of action of GRT-X in the axonal elongation of DRG neurons.

Parkinson's disease is the second most common neurodegenerative disorder, affecting 2–3% of the population of patients >65 years. Although the standard diagnosis of PD is clinical, neuroimaging plays a key role in the evaluation of patients who present symptoms related to neurodegenerative disorders. MRI, DAT-SPECT, and PET with [18F]-FDG are routinely used in the diagnosis and focus on the investigation of morphological changes, nigrostriatal degeneration or shifts in glucose metabolism in patients with parkinsonian syndromes. The aim of this study is to review the current PET radiotracers targeting TSPO, a transmembrane protein that is overexpressed by microglia in another pathophysiological process associated with neurodegenerative disorders known as neuroinflammation. To the best of our knowledge, neuroinflammation is present not only in PD but in many other neurodegenerative disorders, including AD, DLB, and MSA, as well as atypical parkinsonian syndromes. Therefore, in this study, specific patterns of microglial activation in PD and the differences in distribution volumes of these radiotracers in patients with PD as compared to other neurodegenerative disorders are reviewed. [ABSTRACT FROM AUTHOR]

The 18 kDa translocator protein (TSPO/PBR) is a multifunctional evolutionary highly conserved outer mitochondrial membrane protein. Decades of research has reported an obligatory role of TSPO/PBR in both mitochondrial cholesterol transport and, thus, steroid production. However, the strict dependency of steroidogenesis on TSPO/PBR has remained controversial. The aim of this study was to provide insight into the steroid profile in complete C57BL/6-Tspotm1GuWu(GuwiyangWurra)-knockout male mice (TSPO-KO) under basal conditions. The steroidome in the brain, adrenal glands, testes and plasma was measured by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). We found that steroids present in wild-type (WT) mice were also detected in TSPO-KO mice, including pregnenolone (PREG), progestogens, mineralo-glucocorticosteroids and androgens. The concentrations of PREG and most metabolites were similar between genotypes, except a significant decrease in the levels of the 5α-reduced metabolites of progesterone (PROG) in adrenal glands and plasma and of the 5α-reduced metabolites of corticosterone (B) in plasma in TSPO-KO compared to WT animals, suggesting other regulatory functions for the TSPO/PBR. The expression levels of the voltage-dependent anion-selective channel (VDAC-1), CYP11A1 and 5α-reductase were not significantly different between both groups. Thus, the complete deletion of the tspo gene in male mice does not impair de novo steroidogenesis in vivo. [ABSTRACT FROM AUTHOR]

Abstract Background The translocator protein (TSPO) has been identified as a positron emission tomography (PET)-visible biomarker of inflammation and promising immunotherapeutic target for the treatment of Alzheimer’s disease (AD). While TSPO ligands have been shown to reduce the accumulation of the toxic Alzheimer’s beta-amyloid peptide, their effect on tau pathology has not yet been investigated. To address this, we analyzed the effects of TSPO ligand, Ro5-4864, on the progression of neuropathology in rTg4510 tau transgenic mice (TauTg). Methods Brain atrophy, tau accumulation, and neuroinflammation were assessed longitudinally using volumetric magnetic resonance imaging, tau-PET, and TSPO-PET, respectively. In vivo neuroimaging results were confirmed by immunohistochemistry for markers of neuronal survival (NeuN), tauopathy (AT8), and inflammation (TSPO, ionized calcium-binding adaptor molecule 1 or IBA-1, and complement component 1q or C1q) in brain sections from scanned mice. Results TSPO ligand treatment attenuated brain atrophy and hippocampal neuronal loss in the absence of any detected effect on tau depositions. Atrophy and neuronal loss were strongly associated with in vivo inflammatory signals measured by TSPO-PET, IBA-1, and levels of C1q, a regulator of the complement cascade. In vitro studies confirmed that the TSPO ligand Ro5-4864 reduces C1q expression in a microglial cell line in response to inflammation, reduction of which has been shown in previous studies to protect synapses and neurons in models of tauopathy. Conclusions These findings support a protective role for TSPO ligands in tauopathy, reducing neuroinflammation, neurodegeneration, and brain atrophy.

Parkinson’s disease is the second most common neurodegenerative disorder, affecting 2–3% of the population of patients >65 years. Although the standard diagnosis of PD is clinical, neuroimaging plays a key role in the evaluation of patients who present symptoms related to neurodegenerative disorders. MRI, DAT-SPECT, and PET with [18F]-FDG are routinely used in the diagnosis and focus on the investigation of morphological changes, nigrostriatal degeneration or shifts in glucose metabolism in patients with parkinsonian syndromes. The aim of this study is to review the current PET radiotracers targeting TSPO, a transmembrane protein that is overexpressed by microglia in another pathophysiological process associated with neurodegenerative disorders known as neuroinflammation. To the best of our knowledge, neuroinflammation is present not only in PD but in many other neurodegenerative disorders, including AD, DLB, and MSA, as well as atypical parkinsonian syndromes. Therefore, in this study, specific patterns of microglial activation in PD and the differences in distribution volumes of these radiotracers in patients with PD as compared to other neurodegenerative disorders are reviewed.

Background: Anaesthesia and perioperative management contribute to long-term outcomes of patients with cancer, including pancreatic ductal adenocarcinoma. We assessed the antitumour, anti-inflammatory, and analgesic effects of midazolam on LSL-KrasG12D/+;Trp53flox/flox;Pdx-1cre/+ transgenic mice with pancreatic ductal adenocarcinoma.Methods: Six-week-old transgenic mice were administered midazolam 30 mg kg-1 day-1 p.o. (n=13); midazolam 30 mg kg-1 day-1 with 1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide (PK11195) 3 mg kg-1 day-1 i.p., a peripheral benzodiazepine receptor antagonist (n=10); or vehicle (water; n=14) until the humane endpoint. Cancer-associated pain was evaluated using hunching score and mouse grimace scale. Tumour stage and immuno-inflammatory status were determined histopathologically. Anti-proliferative and apoptotic potentials of midazolam were investigated using mouse pancreatic ductal adenocarcinoma cell lines.Results: Midazolam significantly inhibited tumour size and proliferative index of Ki-67 and cyclins in pancreatic ductal adenocarcinoma, which was blocked by administration of PK11195. Local myeloperoxidase+ tumour-associated neutrophils, arginase-1+ M2-like tumour-associated macrophages, and CD11b+Ly-6G+ polymorphonuclear myeloid-derived suppressor cells were reduced by midazolam, which was antagonised by administration of PK11195. Hunching and mouse grimace scale were improved by midazolam, whereas the scores increased with midazolam+PK11195 treatment. Plasma pro-inflammatory cytokines, such as interleukin-6 and CC chemokine ligand (CCL)2, CCL3, and CCL5, were reduced by midazolam, whereas these cytokines increased with PK11195. Midazolam inhibited pancreatic ductal adenocarcinoma proliferation through downregulation of cyclins and cyclin-dependent kinases and induced apoptosis in vitro.Conclusions: These results suggest that midazolam inhibits pancreatic ductal adenocarcinoma proliferation and local infiltration of tumour-associated neutrophils, tumour-associated macrophages, and polymorphonuclear myeloid-derived suppressor cells, thereby inhibiting pancreatic ductal adenocarcinoma progression. [ABSTRACT FROM AUTHOR]

To investigate the histopathological effects of a peripheral benzodiazepine receptor agonist (Ro5-4864) on epidural fibrosis (EF) in an experimental study model (post-laminectomy) in rats. A total of 32 albino Wistar rats were randomly divided into four equal groups (n = 8). In Group 1, no treatment was applied after laminectomy (control group). In Group 2, hemostasis was achieved after Laminectomy, and the surgical procedure was terminated by placing a 2-mm absorbable gelatin sponge dipped in saline into the epidural space. In Group 3, low-dose (4 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. In Group 4, high-dose (8 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. A histopathological examination was performed to evaluate arachnoidal invasion and EF. Our data revealed the EF was significantly reduced in rats treated with high-dose Ro5-4864 (Group 4) compared to the control and saline-soaked Spongostan groups (p = 0.000 and p = 0.006, respectively). There was no significant difference between the groups treated with high- and low-dose Ro5-4864. Arachnoidal invasion was not seen in any of the rats in the high-dose R05-4864 group. However, the arachnoidal invasion results did not significantly differ between the study groups (p = 0.052 = 0.05). Our study showed that Ro5-4864 could be effective in reducing EF in rats after. [ABSTRACT FROM AUTHOR]

The 18 kDa translocator protein (TSPO/PBR) is a multifunctional evolutionary highly conserved outer mitochondrial membrane protein. Decades of research has reported an obligatory role of TSPO/PBR in both mitochondrial cholesterol transport and, thus, steroid production. However, the strict dependency of steroidogenesis on TSPO/PBR has remained controversial. The aim of this study was to provide insight into the steroid profile in complete C57BL/6-Tspotm1GuWu(GuwiyangWurra)-knockout male mice (TSPO-KO) under basal conditions. The steroidome in the brain, adrenal glands, testes and plasma was measured by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). We found that steroids present in wild-type (WT) mice were also detected in TSPO-KO mice, including pregnenolone (PREG), progestogens, mineralo-glucocorticosteroids and androgens. The concentrations of PREG and most metabolites were similar between genotypes, except a significant decrease in the levels of the 5α-reduced metabolites of progesterone (PROG) in adrenal glands and plasma and of the 5α-reduced metabolites of corticosterone (B) in plasma in TSPO-KO compared to WT animals, suggesting other regulatory functions for the TSPO/PBR. The expression levels of the voltage-dependent anion-selective channel (VDAC-1), CYP11A1 and 5α-reductase were not significantly different between both groups. Thus, the complete deletion of the tspo gene in male mice does not impair de novo steroidogenesis in vivo.

Background: The translocator protein (TSPO) has been identified as a positron emission tomography (PET)-visible biomarker of inflammation and promising immunotherapeutic target for the treatment of Alzheimer's disease (AD). While TSPO ligands have been shown to reduce the accumulation of the toxic Alzheimer's beta-amyloid peptide, their effect on tau pathology has not yet been investigated. To address this, we analyzed the effects of TSPO ligand, Ro5-4864, on the progression of neuropathology in rTg4510 tau transgenic mice (TauTg).Methods: Brain atrophy, tau accumulation, and neuroinflammation were assessed longitudinally using volumetric magnetic resonance imaging, tau-PET, and TSPO-PET, respectively. In vivo neuroimaging results were confirmed by immunohistochemistry for markers of neuronal survival (NeuN), tauopathy (AT8), and inflammation (TSPO, ionized calcium-binding adaptor molecule 1 or IBA-1, and complement component 1q or C1q) in brain sections from scanned mice.Results: TSPO ligand treatment attenuated brain atrophy and hippocampal neuronal loss in the absence of any detected effect on tau depositions. Atrophy and neuronal loss were strongly associated with in vivo inflammatory signals measured by TSPO-PET, IBA-1, and levels of C1q, a regulator of the complement cascade. In vitro studies confirmed that the TSPO ligand Ro5-4864 reduces C1q expression in a microglial cell line in response to inflammation, reduction of which has been shown in previous studies to protect synapses and neurons in models of tauopathy.Conclusions: These findings support a protective role for TSPO ligands in tauopathy, reducing neuroinflammation, neurodegeneration, and brain atrophy. [ABSTRACT FROM AUTHOR]

Abstract Background Inflammation is associated with major depressive disorder (MDD). Translocator protein 18 kDa (TSPO), a putative biomarker of neuroinflammation, is quantified using positron emission tomography (PET) and 11C-PBR28, a TSPO tracer. We sought to (1) investigate TSPO binding in MDD subjects currently experiencing a major depressive episode, (2) investigate the effects of antidepressants on TSPO binding, and (3) determine the relationship of peripheral and central inflammatory markers to cerebral TSPO binding. Twenty-eight depressed MDD subjects (unmedicated (n = 12) or medicated (n = 16)) and 20 healthy controls (HC) underwent PET imaging using 11C-PBR28. Total distribution volume (V T, proportional to Bmax/Kd) was measured and corrected with the free fraction in plasma (fp). The subgenual prefrontal cortex (sgPFC) and anterior cingulate cortex (ACC) were the primary regions of interest. Peripheral blood samples and cerebrospinal fluid were analyzed to investigate the relationship between TSPO binding and peripheral and central inflammatory markers, including interleukins and neurotrophic factors previously linked to depression. Results TSPO binding was higher in MDD versus HC in the sgPFC (Cohen’s d = 0.64, p = .038, 95% CI 0.04–1.24) and ACC (d = 0.60, p = .049, 95% CI 0.001–1.21), though these comparisons missed the corrected threshold for statistical significance (α = .025). Exploratory analyses demonstrated that unmedicated MDD subjects had the highest level of TSPO binding, followed by medicated MDD subjects, who did not differ from HC. TSPO binding correlated with interleukin-5 in cerebrospinal fluid but with no other central inflammatory markers. Conclusions This study found a trend towards increased TSPO binding in the brains of MDD subjects, and post hoc analysis extended these findings by demonstrating that this abnormality is significant in unmedicated (but not medicated) MDD subjects.

Despite improvements in cancer treatments resulting in higher survival rates, the proliferation and metastasis of tumors still raise new questions in cancer therapy. Therefore, new drugs and strategies are still needed. Midazolam (MDZ) is a common sedative drug acting through the γ-aminobutyric acid receptor in the central nervous system and also binds to the peripheral benzodiazepine receptor (PBR) in peripheral tissues. Previous studies have shown that MDZ inhibits cancer cell proliferation but increases cancer cell apoptosis through different mechanisms. In this study, we investigated the possible anticancer mechanisms of MDZ on different cancer cell types. MDZ inhibited transforming growth factor β (TGF-β)-induced cancer cell proliferation of both A549 and MCF-7 cells. MDZ also inhibited TGF-β-induced cell migration, invasion, epithelial-mesenchymal-transition, and Smad phosphorylation in both cancer cell lines. Inhibition of PBR by PK11195 rescued the MDZ-inhibited cell proliferation, suggesting that MDZ worked through PBR to inhibit TGF-β pathway. Furthermore, MDZ inhibited proliferation, migration, invasion and levels of mesenchymal proteins in MDA-MD-231 triple-negative breast cancer cells. Together, MDZ inhibits cancer cell proliferation both in epithelial and mesenchymal types and EMT, indicating an important role for MDZ as a candidate to treat lung and breast cancers.

The 18 kDa translocator protein (TSPO) is a widely used target for microglial PET imaging radioligands, but its expression in post‐mortem normal and diseased human brain is not well described. We aimed at characterizing the TSPO expression in human control (CTRL) and Alzheimer's disease (AD) brains. Specifically, we sought to: (1) define the cell type(s) expressing TSPO; (2) compare tspo mRNA and TSPO levels between AD and CTRL brains; (3) correlate TSPO levels with quantitative neuropathological measures of reactive glia and AD neuropathological changes; and (4) investigate the effects of the TSPO rs6971 SNP on tspo mRNA and TSPO levels, glial responses and AD neuropathological changes. We performed quantitative immunohistochemistry and Western blot in post‐mortem brain samples from CTRL and AD subjects, as well as analysis of publicly available mouse and human brain RNA‐Seq datasets. We found that: (1) TSPO is expressed not just in microglia, but also in astrocytes, endothelial cells and vascular smooth muscle cells; (2) there is substantial overlap of tspo mRNA and TSPO levels between AD and CTRL subjects and in TSPO levels between temporal neocortex and white matter in both groups; (3) TSPO cortical burden does not correlate with the burden of activated microglia or reactive astrocytes, Aβ plaques or neurofibrillary tangles, or the cortical thickness; (4) the TSPO rs6971 SNP does not significantly impact tspo mRNA or TSPO levels, the magnitude of glial responses, the cortical thickness, or the burden of AD neuropathological changes. These results could inform ongoing efforts toward the development of reactive glia‐specific PET radioligands. [ABSTRACT FROM AUTHOR]

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Abstract: Midazolam, a benzodiazepine derivative, is widely used for sedation and surgery. However, previous studies have demonstrated that Midazolam is associated with increased risks of congenital malformations, such as dwarfism, when used during early pregnancy. Recent studies have also demonstrated that Midazolam suppresses osteogenesis of mesenchymal stem cells (MSCs). Given that hypertrophic chondrocytes can differentiate into osteoblast and osteocytes and contribute to endochondral bone formation, the effect of Midazolam on chondrogenesis remains unclear. In this study, we applied a human MSC line, the KP cell, to serve as an in vitro model to study the effect of Midazolam on chondrogenesis. We first successfully established an in vitro chondrogenic model in a micromass culture or a 2D high‐density culture performed with TGF‐β‐driven chondrogenic induction medium. Treatment of the Midazolam dose‐dependently inhibited chondrogenesis, examined using Alcian blue‐stained glycosaminoglycans and the expression of chondrogenic markers, such as SOX9 and type II collagen. Inhibition of Midazolam by peripheral benzodiazepine receptor (PBR) antagonist PK11195 or small interfering RNA rescued the inhibitory effects of Midazolam on chondrogenesis. In addition, Midazolam suppressed transforming growth factor‐β‐induced Smad3 phosphorylation, and this inhibitory effect could be rescued using PBR antagonist PK11195. This study provides a possible explanation for Midazolam‐induced congenital malformations of the musculoskeletal system through PBR. [ABSTRACT FROM AUTHOR]

Since the discovery of antitumor activity of cisplatin in the late 60’s, the development of metal-based drugs has had an enormous burst with the aim of to increase the anti-cancer activity, lower side effects and promote specific accumulation to the target cells or organs. Indeed, a new discipline, called medicinal inorganic chemistry, has born where metal ions play a fundamental role. This review provides a comprehensive overview of various metal complexes targeting the Translocator Protein (TSPO), an 18 kDa high affinity cholesterol- and drug-binding protein found mostly in the outer mitochondrial membrane and formerly known as peripheral-type benzodiazepine receptor. TSPO distribution in healthy tissues varies considerably; in contrast, aberrant expression of TSPO has been noted in several pathological specimens including neurodegenerative diseases and cancers. These findings suggest that TSPO-targeted therapy and imaging may have utility in the treatment and visualization of diseases expressing high density of TSPO. In this review, potential applications in cancer diagnosis and therapy will be discussed. [ABSTRACT FROM AUTHOR]

HIV encephalitis (HIVE) is characterized by neurodegeneration mediated by toxins derived from infected and activated brain macrophages. Since the peripheral benzodiazepine receptor (PBR) is abundant on brain macrophages, we hypothesized that [3H]DAA1106, a new PBR ligand, can label infected and activated brain macrophages in HIVE. Using cell culture and postmortem brain tissues from HIVE and a macaque model of HIVE, we show that [3H]DAA1106 binds with high affinity to activated and infected macrophages in regions of synaptic damage. Further, binding affinity reflected by lower KD (dissociation constant) values and the Bmax (total number of binding sites) to KD ratios reflective of ligand-binding potential was significantly higher with [3H]DAA1106 compared to the extensively characterized PBR ligand [3H](R)-PK11195. These data suggest that DAA1106 binds with high affinity to activated and infected brain macrophages and possesses binding characteristics beneficial for in vivo use in the detection and clinical monitoring of HIVE using positron emission tomography.

The effects of neuroactive steroids have been highly assessed for their significance on inflammation resolution induced by cytotoxic agents. Steroids are derived from cholesterol, and this regulatory pathway may be a target for possible protective strategies. For example, the increased expression of peripheral benzodiazepine receptor (PBR) stimulates steroids production, and the action of specific ligands on PBR favors the reduction of glial activity and act as a protective mechanism. The augmented expression of PBR and steroidogenic acute regulatory protein (StAR) after injury is associated with local production of steroids by glial cells. For instance, cholesterol is captured by StAR in the outer mitochondrial membrane that transfers it to PBR, which uses it as substrate for the enzyme P450scc in the inner mitochondrial membrane. Some ligands, such as 4'-Chlorodiazepam (Ro5-4864) and isoquinoline carboxamide (PK 11195), act as agonists of the PBR receptor. Previous studies indicate that Ro5-4864 reduces neuronal loss, thus implying the regulation of mitochondrial transition after a traumatic brain injury. In this work, we assess the effects of PBR ligands directly involved in neuronal cell survival and proliferation after injury, thereby activating potential downstream targets as novel therapeutic approaches.

Background Methamphetamine (METH) is a neurotoxin and psychostimulant drug with potent effects on the central nervous system. With chronic METH administration, an inflammatory glial response is observed as a result of METH-induced neurotoxicity. One inflammatory marker is the peripheral benzodiazepine receptor (PBR). Objective The purpose of the present study was to determine whether PBR expression is changed in METH dependence and whether the changes relate to cognitive deficits. Methods Reverse transcriptase-polymerase chain reaction was used to investigate PBR gene expression in blood samples taken from 14 male subjects with METH dependence and 14 controls. Results The results showed a significant increase in PBR gene expression in METH dependence, suggestive of a systemic inflammatory response. The increase remained elevated for more than 1 year following abstinence from METH use, but eventually returned to normal. Subjects with elevated PBR also exhibited a deficit in one domain of the Wisconsin Card Sorting Test. Conclusion The results suggest that systemic inflammatory effects can be associated with chronic METH abuse, and this may relate to the cognitive deficits seen in METH dependence. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

During the past decade, translocator protein 18 kDa (TSPO), previously named peripheral benzodiazepine receptor, has gained a great deal of attention based on its use as a clinical biomarker of neuroinflammation with therapeutic potential. However, there is a paucity of knowledge on the function(s) of TSPO in glial cells. Here, we identify a novel function of TSPO in microglia that is not associated with steroidogenesis. We propose that a TSPO interaction with NADPH oxidase (NOX2) links the generation of reactive oxygen species (ROS) to the induction of an antioxidant response to maintain redox homeostasis. This line of investigation may provide a greater understanding of TSPO glial cell biology, and the knowledge gained may prove beneficial in devising therapeutic strategies. [ABSTRACT FROM AUTHOR]

The 3D structure of the 18-kDa transmembrane (TM) protein TSPO (translocator protein)/PBR (peripheral benzodiazepine receptor), which contains a binding site for benzodiazepines, is important to better understand its function and regulation by endogenous and synthetic ligands. We have recently determined the structure of mammalian TSPO/PBR in complex with the diagnostic ligand PK11195 [1-(2-chlorophenyl)- N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide; Jaremko et al. (2014) Science 343, 1363-1366], providing for the first time atomic-level insight into the conformation of this protein, which is up-regulated in various pathological conditions including Alzheimer's disease and Parkinson's disease. Here, we review the studies which have probed the structural properties of mammalian TSPO/PBR as well as the homologues bacterial tryptophan-rich sensory proteins (TspOs) over the years and provide detailed insight into the 3D structure of mouse TSPO (mTSPO)/PBR in complex with PK11195. [ABSTRACT FROM AUTHOR]

Translocator protein 18 kDa ( TSPO) expression at the mitochondrial membrane of glial cells is related to glial activation. TSPO radioligands such as [18F] DPA-714 are useful for the non-invasive study of neuroimmune processes using positron emission tomography ( PET). Anesthetic agents were shown to impact mitochondrial function and may influence [18F] DPA-714 binding parameters and PET kinetics. [18F] DPA-714 PET imaging was performed in Papio anubis baboons anesthetized using either intravenous propofol ( n = 3) or inhaled isoflurane ( n = 3). Brain kinetics and metabolite-corrected input function were measured to estimate [18F] DPA-714 brain distribution ( VT). Displacement experiments were performed using PK11195 (1.5 mg/kg). In vitro [18F] DPA-714 binding experiments were performed using baboon brain tissue in the absence and presence of tested anesthetics. Brain radioactivity peaked higher in isoflurane-anesthetized animals compared with propofol ( SUVmax = 2.7 ± 0.5 vs. 1.3 ± 0.2, respectively) but was not different after 30 min. Brain VT was not different under propofol and isoflurane. Displacement resulted in a 35.8 ± 8.4% decrease of brain radioactivity under propofol but not under isoflurane (0.1 ± 7.0%). In vitro, the presence of propofol increased TSPO density and dramatically reduced its affinity for [18F] DPA-714 compared with control. This in vitro effect was not significant with isoflurane. Exposure to propofol and isoflurane differentially influences TSPO interaction with its specific radioligand [18F] DPA-714 with subsequent impact on its tissue kinetics and specific binding estimated in vivo using PET. Therefore, the choice of anesthetics and their potential influence on PET data should be considered for the design of imaging studies using TSPO radioligands, especially in a translational research context. [ABSTRACT FROM AUTHOR]

Research spanning nearly four decades has assigned to the translocator protein (18 kDa) (TSPO) a critical role, among others, in the mitochondrial import of cholesterol, the subsequent steps of (neuro)steroid production, and systemic endocrine regulation, with implications for the pathophysiology of immune, inflammatory, neurodegenerative, and psychiatric as well as neoplastic diseases. Recent knockout studies in mice unexpectedly report normal or latent phenotypes, raising doubts about the protein's role in steroidogenesis and other previously postulated functions and challenging the validity of earlier data on the selectivity of TSPO-binding drugs. Here we provide a synthesis of the current debate from a structural and molecular biology perspective, discuss the limits of inference in loss-of-function (gene knockout) studies, and suggest new functions of TSPO. [ABSTRACT FROM AUTHOR]

The sigma-2 receptor is a steroid-binding membrane-associated receptor which has been implicated in cell survival. Sigma-2 has recently been shown to bind amyloid-β (Aβ) oligomers in Alzheimer's disease (AD) brain. Furthermore, blocking this interaction was shown to prevent or reverse the effects of Aβ to cause cognitive impairment in mouse models and synaptic loss in neuronal cultures. In the present work, the density of sigma-2 receptors was measured in a double transgenic mouse model of amyloid-β deposition (APP/PS1). Comparisons were made between males and females and between transgenic and wt animals. Sigma-2 receptor density was assessed by quantitative autoradiography performed on coronal brain slices using [ 3 H] N -[4-(3,4-dihydro-6,7-dimethoxyisoquinolin-2(1H)-yl)butyl]-2-methoxy-5-methyl-benzamide ([ 3 H]RHM-1), which has a 300-fold selectivity for the sigma-2 receptor over the sigma-1 receptor. The translocator protein of 18 kDa (TSPO) is expressed on activated microglia and is a marker for neuroinflammation. TSPO has been found to be upregulated in neurodegenerative disorders, including AD. Therefore, in parallel with the sigma-2 autoradiography experiments, we measured TSPO expression using the selective radioligand, [ 3 H]PBR28. We also quantified Aβ plaque burden in the same animals using a monoclonal antibody raised against aggregated Aβ. Sigma-2 receptor density was significantly decreased in piriform and motor cortices as well as striata of 16-month old female, but not male, APP/PS1 mice as compared to their wt counterparts. [ 3 H]PBR28 binding and immunostaining for Aβ plaques were significantly increased in piriform and motor cortices of both male and female transgenic mice. In striatum however, significant increases were observed only in females. [ABSTRACT FROM AUTHOR]

The mitochondrial 18kDa Translocation Protein (TSPO) was first identified in 1977 by its capability to bind benzodiazepines in peripheral tissues. It is more commonly known after its previous name - peripheral benzodiazepine receptor (PBR) as opposed to the central benzodiazepine receptor (CBR), from which it differs by location, structure and function. It is ubiquitous with highest expression in steroid-producing tissues, like adrenal cortex, ovaries, testicles, and placenta. The role of TSPO is crucial for living; its inactivation results in early embryonic-lethal phenotype in mice. TSPO has been implicated in various functions of cell, including steroidogenesis, cellular respiration, reactive oxygen species production, heme biosynthesis, immunomodulation, apoptosis, and cellular proliferation. TSPO has been shown to interact with other cellular proteins: 32 kDa voltage-dependent anion channel (VDAC), 30 kDa adenine nucleotide translocase (ANT), cyclophilin D, hexokinase, creatinine kinase, diazepam binding inhibitor (DBI), phosphate carrier and Bcl-2 family. They are - involved in the formation and regulation of mitochondrial permeability transition pore (mPTP) at the junction of the inner and outer mitochondrial membranes. While the function and characteristics of the mPTP are known, its well defined, but its structure remains speculative. Changes in TSPO expression are associated with multiple disorders, including cancer, ischaemia-reperfusion injury, neurological diseases and psychiatric disorders, atheromatosis, and others. - TSPO is able to bind cholesterol, porphyrins and other ligands with different affinity. The current knowledge of TSPO implicates its potential use as a diagnostic marker and therapeutic target in different diseases and their therapies. [ABSTRACT FROM AUTHOR]

Aim: TSPO is a neuroinflammatory biomarker and emerging therapeutic target in psychiatric disorders. We evaluated whether TSPO polymorphisms contribute to interindividual variability in schizophrenia, antipsychotic efficacy and antipsychotic-induced weight gain. Patients & methods: We analyzed TSPO polymorphisms in 670 schizophrenia cases and 775 healthy controls. Gene-gene interactions between TSPO and other mitochondrial membrane protein-encoding genes ( VDAC1 and ANT1) were explored. Positive findings were evaluated in two independent samples (Munich, n = 300; RUPP, n = 119). Results:  TSPO rs6971 was independently associated with antipsychotic-induced weight gain in the discovery (puncor = 0.04) and RUPP samples (p = 3.00 × 10-3), and interacted with ANT1 rs10024068 in the discovery (p = 1.15 × 10-3) and RUPP samples (p = 2.76 × 10-4). Conclusion: Our findings highlight TSPO as a candidate for future investigations of antipsychotic-induced weight gain, and support the involvement of mitochondrial membrane components in this serious treatment side effect. Original submitted 20 August 2014; Revision submitted 3 November 2014 [ABSTRACT FROM AUTHOR]

The level of the translocator protein (TSPO) increases dramatically in microglial cells when the cells are activated in response to neuronal injury and insult. The radiotracer [18F]GE-180 binds selectively and with high affinity to TSPO and can therefore be used to measure neuroinflammation in a variety of disease states. An optimized, automated synthesis of [18F]GE-180 has been developed for the GE FASTlab™ synthesizer. The entire process takes place on the single-use cassette. The radiolabelling is performed by nucleophilic fluorination of the S- enantiomer mesylate precursor. The crude product is purified post-radiolabelling using two solid-phase extraction cartridges integrated on the cassette. Experimental design and multivariate data analysis were used to assess the robustness, and critical steps were optimized with respect to efficacy and quality. The average radiochemical yield is 48% (RSD 6%, non-decay corrected), and the synthesis time including purification is approximately 43 min. The radiochemical purity is ≥95% for radioactive concentration ≤1100 MBq/mL. The total amount of precursor-related chemical impurities is 1-2 µg/mL. The use of solid-phase extraction purification results in a robust GMP compliant process with a product of high chemical and radiochemical purity and consistent performance across positron emission tomography (PET) centers. [ABSTRACT FROM AUTHOR]

Abstract: Background: Acute lung injury (ALI) is a syndrome of inflammation and increased permeability of the blood–gas barrier. It is associated with high morbidity and mortality. Despite intensive research, treatments remain limited. The aim of the present study was to investigate the protective efficacy of a specific peripheral benzodiazepine receptor ligand, Ro5-4864, in experimental models of ALI in rats. Methods: ALI was generated by four different methods: (1) intravenous (tail vein) injection of Escherichia coli (0111:B4) lipopolysaccaride (LPS), (2) cecal ligation and puncture (CLP), (3) mesenteric ischemia/reperfusion, and (4) intraperitoneal injection of α-naphthylthiourea (ANTU). Ro5-4864 was administered to rats intraperitoneally 30 min before ANTU and LPS administration or intravenously 15 min before reperfusion and CLP. The levels of pulmonary edema (lung weight/body weight ratio) and pleural effusion were measured, and the severity of ALI was scored (0–3). Results: Ro5-4864 showed a dose-dependent and significant prophylactic effect on the ANTU-induced lung weight/body weight and pleural effusion/body weight ratios and histopathologic scores. Ro5-4864 also showed significant prophylactic effects against the LPS-induced lung weight/body weight ratio and histopathologic scores. Ro5-4864 significantly decreased the intra-alveolar edema and perialveolar hemorrhage scores in the CLP group. However, we found no prophylactic effect of Ro5-4864 on mesenteric ischemia/reperfusion-induced ALI at the dose used (2 mg/kg intraperitoneally). Conclusions: These results have demonstrated, for the first time, a protective effect of Ro5-4864 on experimental ALI induced by ANTU, LPS, and CLP. Ro5-4864 might be a useful therapeutic agent for lung diseases, including ALI, in intensive care patients. [Copyright &y& Elsevier]

Purpose: In recent years there has been an increase in the development of radioligands targeting the 18-kDa translocator protein (TSPO). TSPO expression is well documented in activated microglia and serves as a biomarker for imaging neuroinflammation. In addition, TSPO has also been reported to be overexpressed in a number of cancer cell lines and human tumours including glioma. Here we investigated the use of [F]DPA-714, a new TSPO positron emission tomography (PET) radioligand to image glioma in vivo. Methods: We studied the uptake of [F]DPA-714 in three different rat strains implanted with 9L rat glioma cells: Fischer (F), Wistar (W) and Sprague Dawley (SD) rats. Dynamic [F]DPA-714 PET imaging, kinetic modelling of PET data and in vivo displacement studies using unlabelled DPA-714 and PK11195 were performed. Validation of TSPO expression in 9L glioma cell lines and intracranial 9L gliomas were investigated using Western blotting and immunohistochemistry of brain tissue sections. Results: All rats showed significant [F]DPA-714 PET accumulation at the site of 9L tumour implantation compared to the contralateral brain hemisphere with a difference in uptake among the three strains (F > W > SD). The radiotracer showed high specificity for TSPO as demonstrated by the significant reduction of [F]DPA-714 binding in the tumour after administration of unlabelled DPA-714 or PK11195. TSPO expression was confirmed by Western blotting in 9L cells in vitro and by immunohistochemistry ex vivo. Conclusion: The TSPO radioligand [F]DPA-714 can be used for PET imaging of intracranial 9L glioma in different rat strains. This preclinical study demonstrates the feasibility of employing [F]DPA-714 as an alternative radiotracer to image human glioma. [ABSTRACT FROM AUTHOR]

Abstract: Background: Post-stroke microglial activation (MA) may have both neurotoxic and pro-repair effects, particularly in the salvaged penumbra. Mapping MA in vivo is therefore an important goal. 11C-PK11195, a ligand for the 18kDa translocator protein, is the reference radioligand for MA imaging, but a correlation between the regional distributions of in vivo tracer binding and post mortem MA after stroke, as assessed with PET and immunohistochemistry, respectively, has not been demonstrated so far. Here we performed 11C-PK11195 microPET in a rat model previously shown to induce extensive cortical MA, and determined the correlation between 11C-PK11195 and immunostaining with the CD11 antibody OX42, so as to verify the presence of activated microglia, in a template of PET-resolution size regions-of-interest (ROIs) spanning the whole affected hemisphere. Methods: Adult spontaneously hypertensive rats underwent 45min distal middle cerebral artery occlusion and 11C-PK11195 PET at Days 2 and 14 after stroke according to a longitudinal design. Following perfusion-fixation at Day 14, brains were removed and coronally cut for OX42 staining. 11C-PK11195 binding potential (BPND) parametric maps were generated, and in each rat both BPND and OX42 (intensity×extent score) were obtained in the same set of 44 ROIs extracted from a cytoarchitectonic atlas to cover the whole hemisphere. Correlations were computed across the 44 ROIs both within and across subjects. Results: Significant BPND increases were observed in both the infarct and surrounding areas in all rats at day 14; less strong but still significant increases were present at day 2. There were highly significant (all p<0.001) positive correlations, both within- and across-subjects, between day 14 BPND values and OX42 scores. Conclusions: The correlation between Day 14 11C-PK11195 and OX42 across the affected hemisphere from the same brain regions and animals further supports the validity of 11C-PK11195 as an in vivo imaging marker of MA following stroke. The finding of statistically significant increases in 11C-PK11195 as early as 48h after stroke is novel. These results have implications for mapping MA after stroke, with potential therapeutic applications. [Copyright &y& Elsevier]

Background: We studied the distribution and expression of translocator protein in the human brain using 11C-[R]- PK-11195 positron emission tomography (PK11195 PET) and evaluated age-related changes. Methods: A dynamic PK11195 PET scan was performed in 15 normal healthy adults (mean age: 29 ±8.5 years (range: 20 to 49); 7 males) and 10 children (mean age: 8.8 ±5.2 years (range: 1.2 to 17); 5 males), who were studied for potential neuroinflammation but showed no focally increased PK11195 binding. The PET images were evaluated by calculating standard uptake values and regional binding potential, based on a simplified reference region model, as well as with a voxel-wise analysis using statistical parametric mapping. Results: PK11195 uptake in the brain is relatively low, compared with the subcortical structures, and symmetrical. The overall pattern of PK11195 distribution in the brain does not change with age. PK11195 uptake was lowest in the frontal-parietal-temporal cortex and highest in the pituitary gland, midbrain, thalamus, basal ganglia, occipital cortex, hippocampus and cerebellum, in descending order. White matter showed negligible PK11195 uptake. Overall, brain PK11195 uptake increased with age, with midbrain and thalamus showing relatively higher increases with age compared with other brain regions. Conclusions: The brain shows low PK11195 uptake, which is lower in the cortex and cerebellum compared with subcortical structures, suggesting a low level of translocator protein expression. There is no hemispheric asymmetry in PK11195 uptake and the overall pattern of PK11195 distribution in the brain does not change with age. However, brain PK11195 uptake increases with age, with the thalamus and midbrain showing relatively higher increases compared with other brain regions. This increase in uptake suggests an age-related increase in translocator protein expression or the number of cells expressing these receptors or both. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to assess the feasibility and sensitivity of the high-affinity translocator protein (TSPO) ligand [I]-CLINDE in imaging TSPO changes in vivo and characterise and compare astroglial and TSPO changes in the cuprizone model of demyelination and remyelination in C57BL/6 mice. Methods: C57BL/6 mice were fed with cuprizone for 4 weeks to induce demyelination followed by 2-4 weeks of standard diet (remyelination). Groups of mice were followed by in vivo single photon emission computed tomography (SPECT)/CT imaging using [I]-CLINDE and uptake correlated with biodistribution, autoradiography, immunohistochemistry, immunofluorescence and real-time polymerase chain reaction (RT-PCR). Results: The uptake of [I]-CLINDE in the brain as measured by SPECT imaging over the course of treatment reflects the extent of the physiological response, with significant increases observed during demyelination followed by a decrease in uptake during remyelination. This was confirmed by autoradiography and biodistribution studies. A positive correlation between TSPO expression and astrogliosis was found and both activated astrocytes and microglial cells expressed TSPO. [I]-CLINDE uptake reflects astrogliosis in brain structures such as corpus callosum, caudate putamen, medium septum and olfactory tubercle as confirmed by both in vitro and in vivo results. Conclusion: The dynamics in the cuprizone-induced astroglial and TSPO changes, observed by SPECT imaging, were confirmed by immunofluorescence, RT-PCR and autoradiography. The highly specific TSPO radioiodinated ligand CLINDE can be used as an in vivo marker for early detection and monitoring of a variety of neuropathological conditions using noninvasive brain imaging techniques. [ABSTRACT FROM AUTHOR]

Purpose: Neuroinflammation is involved in neurological disorders through the activation of microglial cells. Imaging of neuroinflammation with radioligands for the translocator protein (18 kDa) (TSPO) could prove to be an attractive biomarker for disease diagnosis and therapeutic evaluation. The indoleacetamide-derived 7-chloro- N, N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4 H-pyridazino[4,5- b]indole-1-acetamide, SSR180575, is a selective high-affinity TSPO ligand in human and rodents with neuroprotective effects. Methods: Here we report the radiolabelling of SSR180575 with C and in vitro and in vivo imaging in an acute model of neuroinflammation in rats. Results: The image contrast and the binding of [C]SSR180575 are higher than that obtained with the isoquinoline-based TSPO radioligand, [C]PK11195. Competition studies demonstrate that [C]SSR180575 has high specific binding for the TSPO. Conclusion: [C]SSR180575 is the first PET radioligand for the TSPO based on an indoleacetamide scaffold designed for imaging neuroinflammation in animal models and in the clinic. [ABSTRACT FROM AUTHOR]

The neuropathology of schizophrenia remains elusive. One indication of this elusiveness is that the literature, in contrast to that on the neuropathology of almost any other disease, deals predominantly with measures of normal structures rather than with the demonstration and characterization of pathological structures. An important exception to this trend has been the continued search, over four decades, for reactive glia. In this article, we review histological and radiological evidence for and against astrocytosis and microgliosis specifically associated with schizophrenia. The studies are generally limited by small samples, flawed designs, and potentially biased methods of counting cells. Interpretation of these studies is further complicated by the frequent presence of glial reactions in older individuals without psychiatric disease. Nonetheless, some of the positive findings in the literature cannot easily be dismissed. A sufficiently large autopsy study, weighted toward younger subjects, could provide a definitive answer, which if positive could be a major step toward finding an underlying pathological process. [Copyright &y& Elsevier]

Abstract: Degenerative joint diseases are related to the excessive degradation of collagen and proteoglycans in cartilage. One of the potent inflammatory mediators of cartilage metabolism is interleukin-1 (IL-1) that has been implicated in the pathogenesis of degenerative joint diseases. Peripheral benzodiazepine receptor ligands have anti-inflammatory activity in rheumatoid arthritis. The present study shows that 4′-chlorodiazepam (Ro-54864), an agonist of peripheral benzodiazepine receptors, counteract inhibition of collagen and DNA biosynthesis, induced by IL-1. Pk-1195, an antagonist of peripheral benzodiazepine receptors did not restore inhibitory effects of IL-1. The mechanism of collagen biosynthesis and cell division regulation involves insulin-like growth factor-I receptor signaling. We found that IL-1 inhibited expression of IGF-IR, while Ro-54864 stimulated the expression of this receptor. Increase in the expression of this receptor was accompanied by increase in mTOR expression and AKT phosphorylation while it had no effect on Ras–Raf–mitogen activated protein kinase (MAPK) pathway. Although IL-1 caused activation of apoptosis in chondrocytes, an addition of Ro-54864 to the cells inhibited the process as detected by annexin V cell staining followed by flow cytometry. The mechanism of this process may be related to protective effect of signal induced by IGF-I receptor. The data suggest that the mechanism of the protective effects of Ro-54864 on IL-1-induced effects in chondrocytes undergoes through mTOR and AKT signaling. It suggest that peripheral benzodiazepine receptor agonist may be considered as a potential pharmacotherapeutical agents in the treatment of inflammatory diseases. [ABSTRACT FROM AUTHOR]

Abstract: TLN-4601 is a farnesylated dibenzodiazepinone isolated from Micromonospora sp. with an antiproliferative effect on several human cancer cell lines. Although the mechanism of action of TLN-4601 is unknown, our earlier work indicated that TLN-4601 binds the PBR (peripheral benzodiazepine receptor; more recently known as the translocator protein or TSPO), an 18kDa protein associated with the mitochondrial permeability transition (mPT) pore. While the exact function of the PBR remains a matter of debate, it has been implicated in heme and steroid synthesis, cellular growth and differentiation, oxygen consumption and apoptosis. Using the Jurkat immortalized T-lymphocyte cell line, documented to have negligible PBR expression, and Jurkat cells stably transfected with a human PBR cDNA, the present study demonstrates that TLN-4601 induces apoptosis independently of PBR expression. As PBRs are overexpressed in brain tumors compared to normal brain, we examined if TLN-4601 would preferentially accumulate in tumors using an intra-cerebral tumor model. Our results demonstrate the ability of TLN-4601 to effectively bind the PBR in vivo as determined by competitive binding assay and receptor occupancy. Analysis of TLN-4601 tissue and plasma indicated that TLN-4601 preferentially accumulates in the tumor. Indeed, drug levels were 200-fold higher in the tumor compared to the normal brain. TLN-4601 accumulation in the tumor (176μg/g) was also significant compared to liver (24.8μg/g; 7-fold) and plasma (16.2μg/mL; 11-fold). Taken together our data indicate that while PBR binding does not mediate cell growth inhibition and apoptosis, PBR binding may allow for the specific accumulation of TLN-4601 in PBR positive tumors. [ABSTRACT FROM AUTHOR]

Abstract: Translocator protein (TSPO) is an 18kDa high affinity cholesterol- and drug-binding protein found primarily in the outer mitochondrial membrane. Although TSPO is found in many tissue types, it is expressed at the highest levels under normal conditions in tissues that synthesize steroids. TSPO has been associated with cholesterol import into mitochondria, a key function in steroidogenesis, and directly or indirectly with multiple other cellular functions including apoptosis, cell proliferation, differentiation, anion transport, porphyrin transport, heme synthesis, and regulation of mitochondrial function. Aberrant expression of TSPO has been linked to multiple diseases, including cancer, brain injury, neurodegeneration, and ischemia-reperfusion injury. There has been an effort during the last decade to understand the mechanisms regulating tissue- and disease-specific TSPO expression and to identify pharmacological means to control its expression. This review focuses on the current knowledge regarding the chemicals, hormones, and molecular mechanisms regulating Tspo gene expression under physiological conditions in a tissue- and disease-specific manner. The results described here provide evidence that the PKCɛ-ERK1/2-AP-1/STAT3 signal transduction pathway is the primary regulator of Tspo gene expression in normal and pathological tissues expressing high levels of TSPO. [ABSTRACT FROM AUTHOR]

Inflammatory/immunological process and glial contribution are suggested in the pathophysiology of schizophrenia. We investigated peripheral benzodiazepine receptors in brains of patients with chronic schizophrenia, which were reported to be located on mitochondria of glial cells, using [11C]DAA1106 with positron emission tomography. Fourteen patients and 14 age- and sex-matched normal controls participated in this study. PET data were analysed by two-tissue compartment model with metabolite-corrected plasma input. Clinical symptoms were assessed using the Positive and Negative Syndrome Scale. There was no significant difference between [11C]DAA1106 binding of the cortical regions of normal controls and patients with schizophrenia, whereas the patients showed a positive correlation between cortical [11C]DAA1106 binding and positive symptom scores. There was also a positive correlation between [11C]DAA1106 binding and duration of illness. Although the correlations need to be interpreted very cautiously, involvement of glial reaction process in the pathophysiology of positive symptoms or progressive change of schizophrenia might be suggested. [ABSTRACT FROM AUTHOR]

Purpose: To quantitatively evaluate the utility of a translocator protein (TSPO)-targeted near-infrared (NIR) probe (NIR-conPK11195) for in vivo molecular imaging of TSPO in breast cancer.Procedures: NIR-conPK11195 uptake and TSPO-specificity were validated in TSPO-expressing human breast adenocarcinoma cells (MDA-MB-231). In vivo NIR-conPK11195 biodistribution and accumulation were quantitatively evaluated in athymic nude mice bearing MDA-MB-231 xenografts.Results: Fluorescence micrographs illustrated intracellular labeling of MDA-MB-231 cells by NIR-conPK11195. Quantitative uptake and competition assays demonstrated dose-dependent (p < 0.001) and TSPO-specific (p < 0.001) NIR-conPK11195 uptake. In vivo, NIR-conPK11195 preferentially labeled MDA-MB-231 tumors with an 11-fold (p < 0.001) and 7-fold (p < 0.001) contrast enhancement over normal tissue and unconjugated NIR dye, respectively.Conclusions: NIR-conPK11195 appears to be a promising TSPO-targeted molecular imaging agent for visualization and quantification of breast cancer cells in vivo. This research represents the first study to demonstrate the feasibility of TSPO imaging as an alternative breast cancer imaging approach. [ABSTRACT FROM AUTHOR]

Abstract: Macrophage presence within atherosclerotic plaque is a feature of instability and a risk factor for plaque rupture and clinical events. Activated macrophages express high levels of the translocator protein/peripheral benzodiazepine receptor (TSPO/PBR). In this study, we investigated the potential for quantifying plaque inflammation by targeting this receptor. TSPO expression and distribution in the plaque were quantified using radioligand binding assays and autoradiography. We show that cultured human macrophages expressed 20 times more TSPO than cultured human vascular smooth muscle cells (VSMCs), the other abundant cell type in plaque. The TSPO ligands [3H](R)-1-(2-chlorophenyl)-N-methyl-(1-methylpropyl)-3-isoquinoline carboxamide ([3H](R)-PK11195) and [3H]N-(2,5-dimethoxybenzyl)-N-(5-fluoro-2-phenoxyphenyl)acetamide ([3H]-DAA1106) bound to the same sites in human carotid atherosclerotic plaques in vitro, and demonstrated significant correlation with macrophage-rich regions. In conclusion, our data indicate that radioisotope-labelled DAA1106 has the potential to quantify the macrophage content of atherosclerotic plaque. [Copyright &y& Elsevier]