Peripheral Benzodiazepine Receptor Ligand Research Articles

Mitochondria protective and anti-apoptotic effects of peripheral benzodiazepine receptor and its ligands on the treatment of asthma in vitro and vivo.

Asthma is a prevalent respiratory inflammatory disease. Abnormal apoptosis of bronchial epithelial cells is one of the major factors in the progression of asthma. Peripheral benzodiazepine receptors are highly expressed in bronchial epithelial cells, which act as a component of the mitochondrial permeability transition pore to regulate its opening and closing and apoptosis of bronchial epithelial cells. We aimed to investigate the mechanisms by which peripheral benzodiazepine receptor and its ligands, agonist 4'-Chlorodiazepam (Ro5-4864) and antagonist 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK 11,195), modulate the mitochondrial function and cell apoptosis in the treatment of asthma. In vitro study, Ro5-4864 and PK 11,195 were utilized to pretreat cells prior to the inflammatory injury induced by Lipopolysaccharide. The reactive oxygen species, the apoptosis of cell, the mitochondrial membrane potentials, the ultrastructures of the mitochondria and the expression levels of peripheral benzodiazepine receptors and apoptosis-related proteins and genes were detected. In vivo study, mice were administrated intraperitoneally with Ro5-4864 and PK 11,195 before sensitized and challenged by ovalbumin. Serum IgE and bronchoalveolar lavage fluid cytokines were detected, and lung tissues were underwent the histopathological examination. The ligands of peripheral benzodiazepine receptor counteracted the effects of the increase of reactive oxygen species, the elevated extent of apoptosis, the decrease of mitochondrial membrane potentials and the disruption of mitochondrial ultrastructures induced by Lipopolysaccharide. The ligands also promoted the expression of anti-apoptosis-related proteins and genes and inhibited the expression of pro-apoptosis-related proteins and genes. Besides, the ligands reduced the levels of serum IgE and bronchoalveolar lavage fluid cytokines in asthmatic mice and attenuated the histopathological damage of lungs. Peripheral benzodiazepine receptor serves as a potential therapeutic target for the treatment of asthma, with its ligands exerting mitochondrial protective and anti-apoptotic effects on bronchial epithelial cells.

Molecular Basis of Metabolism-Mediated Conversion of PK11195 from an Antagonist to an Agonist of the Constitutive Androstane Receptor.

The constitutive androstane receptor (CAR) plays an important role in xenobiotic metabolism, energy homeostasis, and cell proliferation. Antagonism of the CAR represents a key strategy for studying its function and may have potential clinical applications. However, specific human CAR (hCAR) antagonists are limited and conflicting data on the activity of these compounds have been reported. 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK11195), a typical peripheral benzodiazepine receptor ligand, has been established as a potent hCAR deactivator in immortalized cells; whether it inhibits hCAR activity under physiologically relevant conditions remains unclear. Here, we investigated the effects of PK11195 on hCAR in metabolically competent human primary hepatocytes (HPH) and HepaRG cells. We show that although PK11195 antagonizes hCAR in HepG2 cells, it induces the expression of CYP2B6 and CYP3A4, targets of hCAR and the pregnane X receptor (PXR), in HPH, HepaRG, and PXR-knockout HepaRG cells. Utilizing a HPH-HepG2 coculture model, we demonstrate that inclusion of HPH converts PK11195 from an antagonist to an agonist of hCAR, and such conversion was attenuated by potent CYP3A4 inhibitor ketoconazole. Metabolically, we show that the N-desmethyl metabolite is responsible for PK11195-mediated hCAR activation by facilitating hCAR interaction with coactivators and enhancing hCAR nuclear translocation in HPHs. Structure-activity analysis revealed that N-demethylation alters the interaction of PK11195 with the binding pocket of hCAR to favor activation. Together, these results indicate that removal of a methyl group switches PK11195 from a potent antagonist of hCAR to an agonist in HPH and highlights the importance of physiologically relevant metabolism when attempting to define the biologic action of small molecules.

Abstract 3248: Over-expression of 1-ACBP, B-ACBP and PBR genes in mast cells infiltrating oesophageal squamous cell tumors

Abstract Oesophageal cancer ranks as the sixth most common malignancy in the world, and recent evidence has shown that its incidence is increasing. ACBPs (Acyl-coA binding proteins) act as intracellular carrier-proteins for medium to long chain acyl-coA, mediating fatty acid transport to the mitochondrion for ß-oxidation. ACBPs are also believed to be putative ligands of PBR (peripheral benzodiazepine receptor), and bound to this receptor facilitate mitochondrial membrane permeabilization giving the notion that favours apoptosis. The main aim of the study was to establish the expression patterns of 1-ACBP, B-ACBP, and PBR in oesophageal cancer, and to link their roles with the disease. Probes specific to the genes encoding 1-ACBP, B-ACBP, and PBR were PCR amplified and cloned into pGEM-T easy vectors using gene specific primers. The cloned products were sequenced and screened against the GENBANK database (NCBI) to verify the identity and orientation of cloned products within the vector. Antisense and sense probes were then generated using T7 or SP6 RNA polymerase after digestion with either Pst1 or Apa1, respectively. In situ hybridization and quantitative real-time PCR methods were performed to determine localization and the expression levels of the three genes in oesophageal cancer. All three genes illustrated substantial up-regulation within the malignant tissue sections as compared to normal oesophageal sections, all three transcripts localized specifically to plasma cells and lymphocytes in diseased and normal tissue section. In the diseased tissue B-ACBP and 1-ACBP mRNA localized to endothelial cells of blood vessels in the submucosa. B-ACBP also localized to the nucleus of squamous epithelial cells. PBR localization was indicated in tumour islands of invasive tissue sections. Quantitative RT-PCR also indicated that the expression levels of PBR were higher as compared to the ACBP genes expression in tumours. These results show that 1-ACBP, B-ACBP and PBR play a role in the pathogenesis of oesophageal tumours and also suggest the interaction between these genes with the immune system and that was also confirmed using bioinformatics analysis. Citation Format: Zodwa Dlamini. Over-expression of 1-ACBP, B-ACBP and PBR genes in mast cells infiltrating oesophageal squamous cell tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3248.

PET imaging studies show enhanced expression of mGluR5 and inflammatory response during progressive degeneration in ALS mouse model expressing SOD1-G93A gene.

BackgroundAmyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative motor neuron disorder. Genetic studies have linked mutation of the gene SOD1 to ALS pathology as well as several other pathological processes including modulation of glutamatergic function and inflammatory processes. Since therapeutic approaches for ALS are focused on glutamatergic function, we investigated modulation of glutamate transport based on its receptor function as well as excitotoxicity-induced inflammatory response.MethodsIn vivo positron emission tomography (PET) imaging studies of metabotropic glutamate receptor subtype 5 (mGluR5) using [18F]FPEB ([18F]3-fluoro-5-(2-pyridylethynyl)benzonitrile) and inflammatory response using [11C]PBR28 (peripheral benzodiazepine receptor ligand 28) were done in an early and a late phase of neurodegeneration in four ALS mice expressing SOD1-G93A gene and four control base mice (C57/BL6). Accumulation of [18F]FPEB and [11C]PBR28 were quantitated in several brain areas and spinal cord to determine degeneration-induced modulation. The studies were completed with immunohistochemical analyses of mGluR5 and inflammatory response.ResultsThese studies showed enhanced binding potential of [18F]FPEB in several brain areas including striatum, hippocampus, and frontal cortex. In the whole brain, the binding potential increased 49 ± 9 % from base mice to ALS-type mice and further enhanced 23 ± 4 % during disease progression. Also, in the spinal cord 6–22 %, enhanced accumulation of [18F]FPEB was observed during progression of the disease. The accumulation of [11C]PBR28 increased by 110 ± 33 % in the whole brain during progression of the disease indicating significant inflammatory process. [11C]PBR28 accumulation enhanced 89–264 % in the spinal cord and 204 % in the lungs. The end point immunohistochemical analyses verified the enhanced mGluR5 expression and inflammation.ConclusionsThese results confirm the role of glutamate and inflammation in ALS-type pathology. These data also support the hypothesis that excessive glutamate may contribute to inflammation in the chronic neurodegenerative processes in ALS.

Standing & walking posture in children with bilateral spastic cerebral palsy: Are they related?

Regional depolarization of the mitochondrial network can alter cellular electrical excitability and increase the propensity for reentry, in part, through the opening of sarcolemmal KATP channels. Mitochondrial inner membrane potential (ΔΨm) instability or oscillation can be induced in myocytes by exposure to reactive oxygen species (ROS), laser excitation, or glutathione depletion, and is thought to be a major factor in arrhythmogenesis during ischemia–reperfusion. Nevertheless, the correlation between ΔΨm recovery kinetics and reperfusion-induced arrhythmias has been difficult to demonstrate experimentally. Here, we investigate the relationship between subcellular changes in ΔΨm, cellular glutathione redox potential, electrical excitability, and wave propagation during coverslip-induced ischemia–reperfusion (IR) in neonatal rat ventricular myocyte (NRVM) monolayers. Ischemia led to decreased action potential amplitude and duration followed by electrical inexcitability after ~ 15 min of ischemia. ΔΨm depolarization occurred in two phases during ischemia: in phase 1 (< 30 min ischemia), mitochondrial clusters within individual NRVMs depolarized, while phase 2 ΔΨm depolarization (30–60 min) was characterized by global functional collapse of the mitochondrial network across the whole ischemic region of the monolayer, typically involving a propagating metabolic wave. Oxidation of the glutathione (GSSG:GSH) redox potential occurred during ischemia, followed by recovery upon reperfusion (i.e., lifting the coverslip). ΔΨm recovered in the mitochondria of individual myocytes quite rapidly upon reperfusion (< 5 min), but was highly unstable, characterized by subcellular oscillations or flickering of clusters of mitochondria in NRVMs across the reperfused region. Electrical excitability also recovered in a heterogeneous manner, providing an arrhythmogenic substrate which led to formation of sustained reentry. Treatment with 4′-chlorodiazepam, a peripheral benzodiazepine receptor ligand, prevented ΔΨm oscillation, improved GSH recovery rate, and prevented reentry during reperfusion, indicating that stabilization of mitochondrial network dynamics is important for preventing post-ischemic arrhythmias. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".

Mitochondrial instability during regional ischemia–reperfusion underlies arrhythmias in monolayers of cardiomyocytes

Regional depolarization of the mitochondrial network can alter cellular electrical excitability and increase the propensity for reentry, in part, through the opening of sarcolemmal KATP channels. Mitochondrial inner membrane potential (ΔΨm) instability or oscillation can be induced in myocytes by exposure to reactive oxygen species (ROS), laser excitation, or glutathione depletion, and is thought to be a major factor in arrhythmogenesis during ischemia–reperfusion. Nevertheless, the correlation between ΔΨm recovery kinetics and reperfusion-induced arrhythmias has been difficult to demonstrate experimentally. Here, we investigate the relationship between subcellular changes in ΔΨm, cellular glutathione redox potential, electrical excitability, and wave propagation during coverslip-induced ischemia–reperfusion (IR) in neonatal rat ventricular myocyte (NRVM) monolayers. Ischemia led to decreased action potential amplitude and duration followed by electrical inexcitability after ~15min of ischemia. ΔΨm depolarization occurred in two phases during ischemia: in phase 1 (<30min ischemia), mitochondrial clusters within individual NRVMs depolarized, while phase 2 ΔΨm depolarization (30–60min) was characterized by global functional collapse of the mitochondrial network across the whole ischemic region of the monolayer, typically involving a propagating metabolic wave. Oxidation of the glutathione (GSSG:GSH) redox potential occurred during ischemia, followed by recovery upon reperfusion (i.e., lifting the coverslip). ΔΨm recovered in the mitochondria of individual myocytes quite rapidly upon reperfusion (<5min), but was highly unstable, characterized by subcellular oscillations or flickering of clusters of mitochondria in NRVMs across the reperfused region. Electrical excitability also recovered in a heterogeneous manner, providing an arrhythmogenic substrate which led to formation of sustained reentry. Treatment with 4′-chlorodiazepam, a peripheral benzodiazepine receptor ligand, prevented ΔΨm oscillation, improved GSH recovery rate, and prevented reentry during reperfusion, indicating that stabilization of mitochondrial network dynamics is important for preventing post-ischemic arrhythmias. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".

Protective Effects of Acetyl L-Carnitine on Inhalation Anesthetic-Induced Neuronal Damage in the Nonhuman Primate

The inhalation anesthetics nitrous oxide (N2O) and isoflurane (ISO) are commonly used for general anesthesia in human infants. Combined exposures to N2O and ISO are known to cause abnormal apoptotic cell death (neurotoxicity) in pediatric animal models. Acetyl-L-carnitine (ALC), an anti-oxidant dietary supplement, has been reported to minimize neuronal damage in some models of neurotoxicity. MicroPET/CT imaging is capable of detecting and localizing changes in cellular markers of brain damage associated with developmental exposures to general anesthetics. By monitoring changes in glial activation, thought to be a marker of neuroinflammation, it should be possible to determine the intensity, duration and location of neuronal damage associated with exposure to general anesthetics. Here we assessed the uptake of 18F-labeled fluoroethoxybenzyl-N-(4-phenoxypyridin-3-yl) acetamide (FEPPA), a ligand for peripheral benzodiazepine receptors on activated glial cells. On postnatal day (PND) 5, rhesus monkeys (4/group) were exposed to a mixture of 70% N2O, 29% oxygen plus 1% ISO, or ALC (100 mg/kg given i.p.) plus this mixture for 8 hours; control monkeys with and without ALC were exposed to room air only. [18F]-FEPPA was injected intravenously and microPET/CT images were obtained one day and one and three weeks after anesthetic exposure. One day after anesthetic exposure the uptake of FEPPA was significantly increased only in the temporal lobe and one week after exposure uptake was significantly increased in only the frontal lobe. No significant differences in uptake were seen in any area after 3 weeks. Co-administration of ALC effectively blocked the increase in FEPPA uptake in both the temporal and frontal lobes. These findings suggest that microPET/CT imaging of FEPPA uptake may be useful for monitoring the time-course and location of adverse neural events that are associated with developmental exposures to general anesthetics. In addition, ALC appears to be capable of protecting against at least some of the adverse effects associated with such exposures.

Evaluation of microglial activation in injured spinal cord by the peripheral benzodiazepine receptor ligand PK11195: A case report

Evaluation of microglial activation in injured spinal cord by the peripheral benzodiazepine receptor ligand PK11195: A case report

Effects of peripheral benzodiazepine receptor ligand Ro5-4864 in four animal models of acute lung injury

BackgroundAcute 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. MethodsALI 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). ResultsRo5-4864 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). ConclusionsThese 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.

Modulation of constitutive androstane receptor (CAR) and pregnane X receptor (PXR) by 6-arylpyrrolo[2,1-d][1,5]benzothiazepine derivatives, ligands of peripheral benzodiazepine receptor (PBR)

Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) regulate xenobiotic sensing and metabolism through interactions with multiple exogenous and endogenous chemicals. Compounds that activate CAR are often ligands of PXR; attention is therefore given to discovery of new, receptor-specific chemical entities that may be exploited for therapeutic and basic research purposes. Recently, ligands of the peripheral benzodiazepine receptor (PBR), PK11195 and FGIN-1-27, were shown to modulate both CAR and PXR. PBR is a mitochondrial transport protein responsible for multiple regulatory functions, including heme biosynthesis, a major component in cytochrome P450 (CYP) enzymes. To investigate possible new roles for PBR involvement in metabolic regulation, expression of the CAR and PXR target genes, CYP2B6 and CYP3A4, was measured in human hepatocytes following treatment with a targeted PBR ligand set. Luciferase reporter assays with transiently expressed wild-type CAR (CAR1), splice variant CAR3, or PXR in HuH-7 cells were used to further study activation of these receptors. Four structurally related PBR ligands (benzothiazepines) differentially modulate CAR1, CAR3 and PXR activity. Benzothiazepine NF49 is an agonist ligand of CAR3, a partial agonist of PXR, exhibits greater inverse agonist activity on CAR1 than does PK11195, and is a new tool for studying these closely related nuclear receptors.

Midazolam Suppresses Maturation of Murine Dendritic Cells and Priming of Lipopolysaccharide-induced T Helper 1-type Immune Response

Dendritic cells (DCs), as antigen-presenting cells, play a key role in the induction and regulation of adaptive immune response. Midazolam is reported to have immunomodulatory properties that affect immune cells. However, the effect of midazolam on DCs has not been characterized. We examined the immunomodulatory properties of midazolam on DC-mediated immune response. After allowing murine bone marrow-derived DCs induced by granulocyte macrophage colony stimulating factor to mature, we analyzed their expression of costimulatory molecules (CD80 and CD86), major histocompatibility complex class II molecules, and the secretion of interleukin-12 p40. In vitro, we evaluated the effect of midazolam on maturing DCs in mixed cell cultures containing DCs and T cells. In vivo, we investigated the contact-hypersensitivity response. Midazolam suppressed the expression of CD80, CD86, and major histocompatibility complex class II molecules from murine DCs. Treated with midazolam, DCs also secreted less interleukin-12 p40. In mixed cell cultures with CD3-positive T cells, midazolam-treated DCs showed less propensity to stimulate the proliferation of CD3-positive T cells and the secretion of interferon-γ from CD4-positive T cells. Midazolam-treated DCs impaired the induction of contact-hypersensitivity response. Treatment with ligands for peripheral benzodiazepine receptor inhibited the up-regulation of CD80 during DC maturation. Midazolam inhibits the functional maturation of murine DCs and interferes with DC induction of T helper 1 immunity in the whole mouse. In addition, it appears that the immunomodulatory effect of midazolam is mediated via the action of midazolam on the peripheral benzodiazepine receptor.

DDC-Induced Hepatic Protoporphyria and Changes in Serum and in Liver Lipids Content in Rat: Impact of Peripheral Benzodiazepine Receptor

ABSTRACTAdministration of DDC (3,5-diethoxycarbonil-1,4-dihydro-2,4,6-trimethylpyridine) (100 mg/kg, i.p.) to male rats produced significant increase in total porphyrins thus giving rise to the biochemical picture of porphyria(s). Porphyrins, accumulated in hepatic porphyria are putative endogenous ligands for peripheral benzodiazepine receptor. A role of peripheral benzodiazepine receptors in cholesterol transport and metabolism is suggested. Hepatic protoporphyria is associated with hepatomegaly, cholestasis and alterations in the microsomal cytochromes. We found that DDC administration in rat induced lipid disturbances and increased significantly total cholesterol in serum and in liver, as well as total phospholipids in liver. 27-Hydroxycholesterol content was significantly increased in serum and liver by DDC, while phenobarbital had no effect. We assume that the observed lipid disturbances are connected to the accumulation of porphyrins. These effects are probably modulated by porphyrin binding to peripheral benzodiazepine receptors.

Radiosynthesis of 7‐chloro‐N,N‐dimethyl‐5‐[11C]methyl‐4‐oxo‐3‐phenyl‐3,5‐dihydro‐4H‐pyridazino[4,5‐b]indole‐1‐acetamide, [11C]SSR180575, a novel radioligand for imaging the TSPO (peripheral benzodiazepine receptor) with PET

AbstractSSR180575 (7‐chloro‐N,N,5‐trimethyl‐4‐oxo‐3‐phenyl‐3,5‐dihydro‐4H‐pyridazino[4,5‐b]indole‐1‐acetamide) is the lead compound of an original pyridazinoindole series of potent and highly selective TSPO (peripheral benzodiazepine receptor) ligands. Isotopic labeling of SSR180575 with the short‐lived positron‐emitter carbon‐11 (T1/2: 20.38 min) at its 5‐methylpyridazino[4,5‐b]indole moiety as well as at its N,N‐dimethylacetamide function by methylation of the corresponding nor‐analogues was investigated. Best results in terms of radiochemical yields and purities were obtained for the preparation of [indole‐N‐methyl‐11C]SSR180575, where routine production batches of 4.5–5.0 GBq of radiochemically pure (&gt;99%) i.v. injectable solutions (specific radioactivities: 50–90 GBq/µmol) could be prepared within a total synthesis time of 25 min (HPLC purification included) starting from a 55 GBq [11C]CO2 cyclotron production batch (non‐decay‐corrected overall radiochemical yields: 8–9%). The process comprises (1) trapping at −10°C of [11C]methyl triflate in DMF (300 µl) containing 0.2–0.3 mg of the indole precursor for labeling and 4 mg of K2CO3 (excess); (2) heating at 120°C for 3 min; (3) dilution of the residue with 0.5 ml of the HPLC mobile phase and (4) purification using semi‐preparative reversed‐phase HPLC (Zorbax® SB‐C‐18). In vivo pharmacological properties of [indole‐N‐methyl‐11C]SSR180575 as a candidate for imaging neuroinflammation with positron emission tomography are currently evaluated. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A rapid solid-phase extraction method for measurement of non-metabolised peripheral benzodiazepine receptor ligands, [18F]PBR102 and [18F]PBR111, in rat and primate plasma

To develop a rapid and reliable method for estimating non-metabolised PBR ligands fluoroethoxy ([(18)F]PBR102)- and fluoropropoxy ([(18)F]PBR111)-substituted 2-(6-chloro-2-phenyl)imidazo[1,2-a]pyridine-3-yl)-N,N-diethylacetamides in plasma. Rats and baboons were imaged with PET up to 2 h postinjection of [(18)F]PBR102 and [(18)F]PBR111 under baseline conditions, after pre-blocking or displacement with PK11195. Arterial plasma samples were directly analysed by reverse-phase solid-phase extraction (RP-SPE) and RP-HPLC and by normal-phase TLC. SPE cartridges were successively washed with acetonitrile/water mixtures. SPE eluant radioactivity was measured in a γ-counter to determine the parent compound fraction and then analysed by HPLC and TLC for validation. In SPE, hydrophilic and lipophilic radiolabelled metabolites were eluted in water and 20% acetonitrile/water. All non-metabolised [(18)F]PBR102 and [(18)F]PBR111 were in SPE acetonitrile fraction as confirmed by HPLC and TLC analysis. Unchanged (%) [(18)F]PBR102 and [(18)F]PBR111 from SPE analysis in rat and baboon plasma agreed with those from HPLC and TLC analysis. In rats and baboons, the fraction of unchanged tracer followed a bi-exponential decrease, with half-lives of 7 to 10 min for the fast component and >80 min for the slow component for both tracers. Direct plasma SPE analysis of [(18)F]PBR102 and [(18)F]PBR111 can reliably estimate parent compound fraction. SPE was superior to HPLC for samples with low activity; it allows rapid and accurate metabolite analysis of a large number of plasma samples for improved estimation of metabolite-corrected input function during quantitative PET imaging studies.

4′-Chlorodiazepam — Agonist of peripheral benzodiazepine receptors as a protecting factor in IL-1 induced deregulation of collagen biosynthesis in cultured human chondrocytes

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.

Imaging of Vascular Inflammation With [11C]-PK11195 and Positron Emission Tomography/Computed Tomography Angiography

We sought to investigate whether positron emission tomography/computed tomography (CT) angiography using [11C]-PK11195, a selective ligand for peripheral benzodiazepine receptors expressed in activated macrophages, can be used to image vascular inflammation. Activated macrophages and T lymphocytes are fundamental elements in the pathogenesis of large-vessel vasculitides. Fifteen patients (age 52+/-16 years) with systemic inflammatory disorders (6 consecutive symptomatic patients with clinical suspicion of active vasculitis and 9 asymptomatic control patients) underwent positron emission tomography with [11C]-PK11195 and CT angiography. [11C]-PK11195 uptake was measured by calculating target-to-background ratios of activity normalized to venous blood. Coregistration of positron emission tomography with contrast-enhanced CT angiography facilitated localization of [11C]-PK11195 arterial wall uptake. Visual analysis revealed focal [11C]-PK11195 uptake in the arterial wall of all 6 symptomatic patients, but in none of the asymptomatic controls. Although serum inflammatory biomarkers (C-reactive protein, erythrocyte sedimentation rate, white cell count) did not differ significantly between the 2 groups, symptomatic patients had increased [11C]-PK11195 vascular uptake (target-to-background ratio 2.41+/-1.59 vs. 0.98+/-0.10; p=0.001). By binding to activated macrophages in the vessel wall, [11C]-PK11195 enables noninvasive imaging of vascular inflammation. Alternative longer-lived radioligands for probing peripheral benzodiazepine receptors are being tested for wider clinical applications.

TNF-alpha induced PMN apoptosis in whole human blood: Protective effect of SSR180575, a potent and selective peripheral benzodiazepine ligand

The peripheral benzodiazepine receptor (PBR) has been shown to play a key role in the regulation of the mitochondrial process leading to apoptosis. Despite much controversy in the literature on this subject, PBR synthetic ligands (and specifically agonists such as Ro5-4864 and SSR180575) are described as presenting potent anti-apoptotic effect against oxidative stress, TNFα- and tamoxifen-induced apoptosis when the PBR ligand is administrated at a low dose, close to the affinity range of the ligand to its receptor. Such anti-apoptotic activity has already been correlated with a protective effect of PBR ligands against ischemia–reperfusion induced tissue dysfunction. Previously, we had shown that SSR180575 is a specific and high affinity PBR ligand of potential interest in pathological cardiovascular, renal and neurodegenerative indications. Beyond its expression in steroid-producing tissues, heart, liver and kidney, the PBR is also known to be highly expressed in blood cells. In this work, we demonstrate by flow cytometry experiments, that SSR180575, at low concentrations, is able to protect polymorphonuclear leukocytes (PMNs) against TNFα-induced apoptosis in whole blood. Thus, in a new context, SSR180575 again shows potent anti-apoptotic properties. Moreover, TNFα- induced PMN apoptosis appears to be a good surrogate marker for determining SSR180575 blood availability and activity in treated patients.

Peripheral benzodiazepine receptor ligand Ro5-4864 inhibits isoprenaline-induced cardiac hypertrophy in rats

Oxidative stress plays a significant role in the pathogenesis of cardiac hypertrophy. Peripheral benzodiazepine receptors are ubiquitously expressed in various tissues, including the heart. Peripheral benzodiazepine receptors have been reported to be involved in the protection of cells against oxygen radical damage. The present study was designed to determine whether Ro5-4864 (a peripheral benzodiazepine receptor ligand) can inhibit isoprenaline-induced cardiac hypertrophy. Male Wistar rats (body weight 150–200g) were administered, isoprenaline (5mg/kg, body weight, subcutaneously) alone or along with Ro5-4864 (0.1 and 0.5mg/kg, body weight, intraperitoneally) once daily for 14days. Control rats received normal saline subcutaneously (1.0ml/kg). Isoprenaline-induced changes in heart weight to body weight ratio, left ventricular wall thickness (M-mode echocardiography and gross morphometry) and myocyte size were significantly prevented by both the doses of Ro5-4864. Ro5-4864 also attenuated isoprenaline-induced increase in interstitial fibrosis, lipid peroxidation and changes in endogenous antioxidants (glutathione, superoxide dismutase and catalase). Isoprenaline-induced cardiac hypertrophy was associated with increased expression of β myosin heavy chain, which was also prevented by Ro5-4864. This is the first study to demonstrate a salutary effect of Ro5-4864 in experimental cardiac hypertrophy.

Hologram QSAR Studies of N,N-Dialkyl-2-phenylindol-3-ylglyoxylamides Derivatives as Selective Peripheral Benzodiazepine Receptor Ligands

Hologram QSAR Studies of N,N-Dialkyl-2-phenylindol-3-ylglyoxylamides Derivatives as Selective Peripheral Benzodiazepine Receptor Ligands

Two activated stages of microglia and PET imaging of peripheral benzodiazepine receptors with [11C]PK11195 in rats

The transition of microglia from the normal resting state to the activated state is associated with an increased expression of peripheral benzodiazepine receptors (PBR). The extent of PBR expression is dependent on the level of microglial activation. A PBR ligand, [(11)C]PK11195, has been used for imaging of the activation of microglia in vivo. We evaluated whether [(11)C]PK11195 PET can indicate differences of microglial activation between no treatment and lipopolysaccharide (LPS) treatment in a rat artificial injury model of brain inflammation. On day 1, a small aliquot of absolute ethanol was injected into the rat right striatum (ST) to produce artificial brain injury. On day 3, MRI scans were performed to evaluate and select rats showing a similar degree of brain injury. Then LPS or vehicle was administered intraperitoneally. On day 4, PET scans were performed after a bolus injection of [(11)C]PK11195. Eleven rats (7 LPS administered rats, 4 LPS non-administered rats) were evaluated. We used uptake ratios of the integral of right and left striatum from 0 to 60 min as an estimate of PBR distribution volume (V (60)). The number of activated microglia and mRNA expression of inflammatory cytokines (TNFalpha, IL-1beta) were assessed by isolectin-B4 staining and RT-PCR, respectively. Right/left ST V (60) ratios of LPS group were significantly higher than those of non-LPS group (P < 0.03). Although there were no significant differences in the number of activated microglia between the two groups, LPS group showed higher expression of inflammatory cytokines (TNFalpha, IL-1beta) than the non-treated group indicating that further activation was induced by LPS treatment. The results suggest that intensity of PBR signals in [(11)C]PK11195 PET may be related to the level of microglial activation rather than the number in activated microglia at least in an artificial brain injury model.