Benzodiazepine receptor-mediated chemotaxis of human monocytes

Comparison of the effects of remimazolam tosylate and propofol on immune function and hemodynamics in patients undergoing laparoscopic partial hepatectomy: a randomized controlled trial

BACKGROUND

Laparoscopic partial hepatectomy inevitably decrease patient immune function. Propofol has been shown to have immunomodulatory effects but is associated with hemodynamic side effects. Despite studies showing a negligible impact of remimazolam tosylate on hemodynamics, it has not been reported for partial hepatectomy patients. Its influence on immune function also remains unexplored. This study sought to investigate the differences in immune function and intraoperative hemodynamics between patients who underwent laparoscopic partial hepatectomy with remimazolam tosylate and those who underwent laparoscopic partial hepatectomy with propofol.

METHODS

This was a single-center, randomized controlled trial involving 70 patients, who underwent elective laparoscopic partial hepatectomy. The patients were randomly divided into two groups: the remimazolam group (group R) and the propofol group (group P). In this study, the primary outcomes assessed included the patient's immune function and hemodynamic parameters, and the secondary outcomes encompassed the patient's liver function and adverse events.

RESULTS

Data from 64 patients (group R, n = 31; group P, n = 33) were analyzed. The differences in the percentages of CD3+, CD4+, CD8+, and NK cells and the CD4+/CD8+ ratio between the two groups were not statistically significant at 1 day or 3 days after surgery. Compared with those in group P, the MAP and HR at T2 and the MAP at T1 in group R were significantly increased(P < 0.05). The differences in HR and MAP at T0, T3, T4, T5, T6, and T7 and HR at T1 between the two groups were not statistically significant. There were no differences in liver function or adverse effects between the two groups, suggesting that remimazolam tosylate is a safe sedative drug(P > 0.05).

CONCLUSION

The effects of remimazolam tosylate on the immune function of patients after partial hepatectomy are comparable to those of propofol. Additionally, its minimal effect on hemodynamics significantly decreases the incidence of hypotension during anesthesia induction, thereby enhancing overall perioperative safety.

TRIAL REGISTRATION

The trial was registered on May 9, 2022 in the Chinese Clinical Trial Registry, registration number ChiCTR2200059715 (09/05/2022).

The ligands of translocator protein inhibit human Th1 responses and the rejection of murine skin allografts

The translocator protein (TSPO) ligands affected inflammatory and immune responses. However, the exact effects of TSPO ligands on Th1 responses in vitro and in vivo are still unclear. In the present study, we found that TSPO ligands, FGIN1-27 and Ro5-4864, suppressed the cytokine production in a dose-dependent manner by purified human CD4⁺ T-cells from peripheral blood mononuclear cells (PBMCs) after stimulation. TSPO ligands inhibited the production of interferon γ (IFN-γ) by memory CD4⁺ T-cells and the differentiation of naïve CD4⁺ T-cells into Th1 cells via suppressing the activity of the corresponding transcription factors as indicated by reduced expression of T-bet and down-regulation of STAT1, STAT4 and STAT5 phosphorylation. TSPO ligands suppressed cell proliferation and activation of CD4⁺ T-cells by the inhibition of TCR signal transduction including membrane proteins: Zap, Lck, Src; cytoplasm proteins: Plcγ1, Slp-76, ERK, JNK and the nucleoproteins: c-Jun and c-Fos. In addition, FGIN1-27 inhibited mixed lymphocyte reactions by human or murine cells. After the transplantation of allogeneic murine skin, injection of FGIN1-27 into mice prevented graft rejection by inhibition of cell infiltration and IFN-γ production. Taken together, our data suggest that TSPO ligands inhibit Th1 cell responses and might be novel therapeutic medicine for the treatment of autoimmune diseases and prevention of transplant rejection.

GABAergic modulation with classical benzodiazepines prevent stress-induced neuro-immune dysregulation and behavioral alterations

OBJECTIVE

Psychosocial stress is associated with altered immunity, anxiety, and depression. Repeated social defeat (RSD), a model of social stress, triggers egress of inflammatory myeloid progenitor cells (MPCs; CD11b(+)/Ly6C(hi)) that traffic to the brain, promoting anxiety-like behavior. In parallel, RSD enhances neuroinflammatory signaling and long-lasting social avoidant behavior. Lorazepam and clonazepam are routinely prescribed anxiolytics that act by enhancing GABAergic activity in the brain. Besides binding to the central benzodiazepine binding site (CBBS) in the central nervous system (CNS), lorazepam binds to the translocator protein (TSPO) with high affinity causing immunomodulation. Clonazepam targets the CBBS and has low affinity for the TSPO. Here the aims were to determine if lorazepam and clonazepam would: (1) prevent stress-induced peripheral and central inflammatory responses, and (2) block anxiety and social avoidance behavior in mice subjected to RSD.

METHODS

C57/BL6 mice were divided into experimental groups, and treated with either lorazepam (0.10mg/kg), clonazepam (0.25mg/kg) or vehicle (0.9% NaCl). Behavioral data and tissues were collected the morning after the last cycle of RSD.

RESULTS

Lorazepam and clonazepam were effective in attenuating mRNA expression of CRH in the hypothalamus and corticosterone in plasma in mice subjected to RSD. Both drugs blocked stress-induced levels of IL-6 in plasma. Lorazepam and clonazepam had different effects on stress-induced enhancement of myelopoiesis and inhibited trafficking of monocytes and granulocytes in circulation. Furthermore, lorazepam, but not clonazepam, inhibited splenomegaly and the production of pro-inflammatory cytokines in the spleen following RSD. Additionally, lorazepam and clonazepam, blocked stress-induced accumulation of macrophages (CD11b(+)/CD45(high)) in the CNS. In a similar manner, both lorazepam and clonazepam prevented neuroinflammatory signaling and reversed anxiety-like and depressive-like behavior in mice exposed to RSD.

CONCLUSION

These data support the notion that lorazepam and clonazepam, aside from exerting anxiolytic and antidepressant effects, may have therapeutic potential as neuroimmunomodulators during psychosocial stress. The reversal of RSD-induced behavioral outcomes may be due to the enhancement of GABAergic neurotransmission, or some other off-target effect. The peripheral actions of lorazepam, but not clonazepam, seem to be mediated by TSPO activation.

Positron emission tomography and functional characterization of a complete PBR/TSPO knockout

The evolutionarily conserved peripheral benzodiazepine receptor (PBR), or 18-kDa translocator protein (TSPO), is thought to be essential for cholesterol transport and steroidogenesis, and thus life. TSPO has been proposed as a biomarker of neuroinflammation and a new drug target in neurological diseases ranging from Alzheimer's disease to anxiety. Here we show that global C57BL/6-Tspo(tm1GuWu(GuwiyangWurra))-knockout mice are viable with normal growth, lifespan, cholesterol transport, blood pregnenolone concentration, protoporphyrin IX metabolism, fertility and behaviour. However, while the activation of microglia after neuronal injury appears to be unimpaired, microglia from (GuwiyangWurra)TSPO knockouts produce significantly less ATP, suggesting reduced metabolic activity. Using the isoquinoline PK11195, the ligand originally used for the pharmacological and structural characterization of the PBR/TSPO, and the imidazopyridines CLINDE and PBR111, we demonstrate the utility of (GuwiyangWurra)TSPO knockouts to provide robust data on drug specificity and selectivity, both in vitro and in vivo, as well as the mechanism of action of putative TSPO-targeting drugs.

Structure-to-function relationships of bacterial translocator protein (TSPO): a focus on Pseudomonas

The translocator protein (TSPO), which was previously designated as the peripheral-type benzodiazepine receptor, is a 3.5 billion year-old evolutionarily conserved protein expressed by most Eukarya, Archae and Bacteria, but its organization and functions differ remarkably. By taking advantage of the genomic data available on TSPO, we focused on bacterial TSPO and attempted to define functions of TSPO in Pseudomonas via in silico approaches. A tspo ortholog has been identified in several fluorescent Pseudomonas. This protein presents putative binding motifs for cholesterol and PK 11195, which is a specific drug ligand of mitochondrial TSPO. While it is a common surface distribution, the sense of insertion and membrane localization differ between α- and γ-proteobacteria. Experimental published data and STRING analysis of common TSPO partners in fluorescent Pseudomonas indicate a potential role of TSPO in the oxidative stress response, iron homeostasis and virulence expression. In these bacteria, TSPO could also take part in signal transduction and in the preservation of membrane integrity.

[(18)F]DPA-714 PET imaging of AMD3100 treatment in a mouse model of stroke

Chemokine receptor 4 and stromal-cell-derived factor 1 have been found to be related to the initiation of neuroinflammation in ischemic brain. Herein, we aimed to monitor the changes of neuorinflammation after AMD3100 treatment using a translocator protein (TSPO) specific PET tracer in a mouse model of stroke. The transient MCAO model was established with Balb/C mice. The success of the model was confirmed by magnetic resonance imaging and FDG PET. The treatment started the same day after surgery via daily intraperitoneal injection of 1 mg of AMD3100/kg for three consecutive days. [¹⁸F]DPA-714 was used as the TSPO imaging tracer. In vivo PET was performed at different time points after surgery in both control and treated mice. Ex vivo histological and immunofluorescence staining of brain slices was performed to confirm the lesion site and inflammatory cell activation. The TSPO level was also evaluated using Western blotting. Longitudinal PET scans revealed that the level of [¹⁸F]DPA-714 uptake was significantly increased in the ischemic brain area with a peak accumulation at around day 10 after surgery, and the level of uptake remained high until day 16. The in vivo PET data were consistent with those from ex vivo immunofluorescence staining. After AMD3100 treatment, the signal intensity was significantly decreased compared with that of normal saline-treated control group. In conclusion, TSPO-targeted PET imaging using [¹⁸F]DPA-714 can be used to monitor inflammatory response after stroke and provide a useful method for evaluating the efficacy of anti-inflammation treatment.

Translocator protein (18 kDa) (TSPO) is expressed in reactive retinal microglia and modulates microglial inflammation and phagocytosis

BACKGROUND

The translocator protein (18 kDa) (TSPO) is a mitochondrial protein expressed on reactive glial cells and a biomarker for gliosis in the brain. TSPO ligands have been shown to reduce neuroinflammation in several mouse models of neurodegeneration. Here, we analyzed TSPO expression in mouse and human retinal microglia and studied the effects of the TSPO ligand XBD173 on microglial functions.

METHODS

TSPO protein analyses were performed in retinoschisin-deficient mouse retinas and human retinas. Lipopolysaccharide (LPS)-challenged BV-2 microglial cells were treated with XBD173 and TSPO shRNAs in vitro and pro-inflammatory markers were determined by qRT-PCR. The migration potential of microglia was determined with wound healing assays and the proliferation was studied with Fluorescence Activated Cell Sorting (FACS) analysis. Microglial neurotoxicity was estimated by nitrite measurement and quantification of caspase 3/7 levels in 661 W photoreceptors cultured in the presence of microglia-conditioned medium. The effects of XBD173 on filopodia formation and phagocytosis were analyzed in BV-2 cells and human induced pluripotent stem (iPS) cell-derived microglia (iPSdM). The morphology of microglia was quantified in mouse retinal explants treated with XBD173.

RESULTS

TSPO was strongly up-regulated in microglial cells of the dystrophic mouse retina and also co-localized with microglia in human retinas. Constitutive TSPO expression was high in the early postnatal Day 3 mouse retina and declined to low levels in the adult tissue. TSPO mRNA and protein were also strongly induced in LPS-challenged BV-2 microglia while the TSPO ligand XBD173 efficiently suppressed transcription of the pro-inflammatory marker genes chemokine (C-C motif) ligand 2 (CCL2), interleukin 6 (IL6) and inducible nitric oxide (NO)-synthase (iNOS). Moreover, treatment with XBD173 significantly reduced the migratory capacity and proliferation of microglia, their level of NO secretion and their neurotoxic activity on 661 W photoreceptor cells. Furthermore, XBD173 treatment of murine and human microglial cells promoted the formation of filopodia and increased their phagocytic capacity to ingest latex beads or photoreceptor debris. Finally, treatment with XBD173 reversed the amoeboid alerted phenotype of microglial cells in explanted organotypic mouse retinal cultures after challenge with LPS.

CONCLUSIONS

These findings suggest that TSPO is highly expressed in reactive retinal microglia and a promising target to control microglial reactivity during retinal degeneration.

Benzodiazepine augmented γ-amino-butyric acid signaling increases mortality from pneumonia in mice

OBJECTIVES

Benzodiazepines are used for treating anxiety, epilepsy, muscle spasm, alcohol withdrawal, palliation, insomnia, and sedation as they allosterically modulate γ-amino-butyric acid type A (GABAA) receptors. Despite widespread use, the importance and mechanism of their immune side-effects are poorly understood. Herein we sought to elucidate the impact and mechanism of benzodiazepine-induced susceptibility to infection at anxiolytic doses in mice.

DESIGN

Animal randomized controlled trial.

SETTING

Laboratory.

SUBJECTS

Adult female C57BL/6 and BALB/c mice.

INTERVENTIONS

The effect of a subsedative, anxiolytic dose of diazepam (2 mg kg intraperitoneal) was investigated in a murine Streptococcus pneumoniae pneumonia model.

MEASUREMENT AND MAIN RESULTS

Mortality, bacterial and cytokine load, cell recruitment, and intracellular pH were measured. Diazepam treatment did not affect immune homeostasis in the lung. However, diazepam increased mortality and bacterial load from S. pneumoniae pneumonia. The increases in mortality and bacterial load were reversed by a GABAA antagonist, bicuculline, indicating dependence on GABAA receptor signaling. While cell recruitment was unaltered by diazepam, the cytokine response to infection was affected, suggesting that local responses to the pathogen were perturbed. Macrophage and monocytes expressed benzodiazepine sensitive (α1-γ2) GABAA receptors. Interestingly macrophage GABAA receptor expression was regulated by bacterial toll-like receptor agonists and cytokines indicating an endogenous role in the immune response. Functionally diazepam appeared to counteract the endogenous down-regulation of GABAA signaling during infection. Consistent with augmented GABAA signaling, diazepam provoked intracellular acidosis in macrophage, leading to impaired cytokine production, bacterial phagocytosis and killing. In contrast, selective benzodiazepines that do not target the α1 GABAA subunit did not affect macrophage function ex vivo or increase susceptibility to pneumonia in vivo.

CONCLUSIONS

Our data highlight the regulation of macrophage function by GABAA receptor signaling and the potential harm of benzodiazepine exposure during pneumonia. Therapeutically, selective drugs may improve the safety profile of benzodiazepines.

A TSPO ligand is protective in a mouse model of multiple sclerosis

Local production of neurosteroids such as progesterone and allopregnanolone confers neuroprotection in central nervous system (CNS) inflammatory diseases. The mitochondrial translocator protein (TSPO) performs a rate-limiting step in the conversion of cholesterol to pregnenolone and its steroid derivatives. Previous studies have shown that TSPO is upregulated in microglia and astroglia during neural inflammation, and radiolabelled TSPO ligands such as PK11195 have been used to image and localize injury in the CNS. Recent studies have shown that modulating TSPO activity with pharmacological ligands such as etifoxine can initiate the production of neurosteroids locally in the injured CNS. In this study, we examined the effects of etifoxine, a clinically available anxiolytic drug, in the development and progression of mouse experimental autoimmune encephalomyelitis (EAE), an experimental model for multiple sclerosis (MS). Our results showed that etifoxine attenuated EAE severity when administered before the development of clinical signs and also improved symptomatic recovery when administered at the peak of the disease. In both cases, recovery was correlated with diminished inflammatory pathology in the lumbar spinal cord. Modulation of TSPO activity by etifoxine led to less peripheral immune cell infiltration of the spinal cord, and increased oligodendroglial regeneration after inflammatory demyelination in EAE. Our results suggest that a TSPO ligand, e.g. etifoxine, could be a potential new therapeutic option for MS with benefits that could be comparable to the administration of systemic steroids but potentially avoiding the detrimental side effects of long-term direct use of steroids.

The upregulation of translocator protein (18 kDa) promotes recovery from neuropathic pain in rats

At present, effective drug for treatment of neuropathic pain is still lacking. Recent studies have shown that the ligands of translocator protein (TSPO, 18 kDa), a peripheral receptor for benzodiazepine, modulate inflammatory pain. Here, we report that TSPO was upregulated in astrocytes and microglia in the ipsilateral spinal dorsal horn of rats following L5 spinal nerve ligation (L5 SNL), lasting until the vanishing of the behavioral signs of neuropathic pain (∼50 d). Importantly, a single intrathecal injection of specific TSPO agonists Ro5-4864 or FGIN-1-27 at 7 and 21 d after L5 SNL depressed the established mechanical allodynia and thermal hyperalgesia dramatically, and the effect was abolished by pretreatment with AMG, a neurosteroid synthesis inhibitor. Mechanically, Ro5-4864 substantially inhibited spinal astrocytes but not microglia, and reduced the production of tumor necrosis factor-α (TNF-α) in vivo and in vitro. The anti-neuroinflammatory effect was also prevented by AMG. Interestingly, TSPO expression returned to control levels or decreased substantially, when neuropathic pain healed naturally or was reversed by Ro5-4864, suggesting that the role of TSPO upregulation might be to promote recovery from the neurological disorder. Finally, the neuropathic pain and the upregulation of TSPO by L5 SNL were prevented by pharmacological blockage of Toll-like receptor 4 (TLR4). These data suggested that TSPO might be a novel therapeutic target for the treatment of neuropathic pain.

The translocator protein (TSPO) ligand PK11195 induces apoptosis and cell cycle arrest and sensitizes to chemotherapy treatment in pre- and post-relapse neuroblastoma cell lines

High-risk neuroblastoma (NB) has a poor prognosis. Even with intensive myeloablative chemotherapy, relapse is common and almost uniformly fatal, and new treatments are needed. Translocator protein 18kDa (TSPO) ligands have been studied as potential new therapeutic agents in many cancers, but not in NB. We studied the effects of TSPO ligands on cell proliferation, cell cycle progression and apoptosis using paired cell lines derived from the same patient at the time of initial surgery and again after development of progressive disease or relapse post-chemotherapy. We found that TSPO expression was significantly increased 2- to 10-fold in post-relapse cell lines compared with pre-treatment lines derived from the same individual. Subsequently, these cell lines were treated with the specific TSPO ligand 1-(2-chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide (PK11195) (0-160µM) as a single agent, with cytotoxic chemotherapy agents alone (carboplatin, etoposide or melphalan), or with combinations of PK11195 and chemotherapy drugs. We found that PK11195 inhibited proliferation in a dose-dependent manner, induced apoptosis and caused G 1/S cell cycle arrest in all tested NB cell lines at micromolar concentrations. In addition, PK11195 significantly decreased mRNA expression of the chemotherapy resistance efflux pumps ABCA3, ABCB1 and ABCC1 in two post-relapse NB cell lines. We also found that pre-treatment with PK11195 sensitized these cell lines to treatment with cytotoxic chemotherapy agents. These results suggest that PK11195 alone or in combination with standard chemotherapeutic drugs warrants further study for the treatment of neuroblastoma.

Effects of 18-kDa translocator protein knockdown on gene expression of glutamate receptors, transporters, and metabolism, and on cell viability affected by glutamate

OBJECTIVE

Previously, several important roles for glutamate have been described for the biology of primary brain tumors. For example, glutamate has been suggested to promote glioma cell proliferation by the activation of the 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propanoic acid (AMPA) subtype of glutamate receptors. In the present study, we determined the potential regulatory roles of the 18-kDa translocator protein (TSPO) in the glutamatergic system in relation to cell death of brain tumor cells through knockdown of the TSPO by genetic manipulation.

MATERIALS AND METHODS

With microarray analysis and validation of gene expression of particular genes using real-time PCR, we found effects because of small inhibitory RNA knockdown of the TSPO in human U118MG glioblastoma cells on gene expression of glutamate receptors, glutamate transporters, and enzymes for glutamate metabolism. We also applied antisense RNA to silence TSPO in rat C6 glioblastoma cells and assayed the effects on DNA fragmentation, indicative of apoptosis, because of glutamate exposure.

RESULTS

In particular, the effects of TSPO silencing in human U118MG cells related to glutamate metabolism indicate a net effect of a reduction in glutamate levels, which may potentially protect the cells in question from cell death. The TSPO knockdown in C6 cells showed that TSPO is required for the induction of apoptosis because of glutamate exposure.

CONCLUSION

These findings show that interactions between the TSPO and the glutamatergic system may play a role in tumor development of glioblastoma cells. This may also have implications for our understanding of the involvement of the TSPO in secondary brain damage and neurodegenerative diseases.

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

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.

The 18 kDa translocator protein influences angiogenesis, as well as aggressiveness, adhesion, migration, and proliferation of glioblastoma cells

BACKGROUND

It is known that the mitochondrial 18 kDa translocator protein (TSPO) is present in almost all peripheral tissues and also in glial cells in the brain. TSPO levels are typically enhanced in correlation with tumorigenesis of cancer cells including glioblastoma. Relevant for angiogenesis, TSPO is also present in almost all cells of the cardiovascular system.

METHODS

We studied the effect of TSPO knockdown by siRNA on various aspects of tumor growth of U118MG glioblastoma cells in two in-vivo models: a nude mouse model with intracerebral implants of U118MG glioblastoma cells and implantation of U118MG glioblastoma cells on the chorionallantoic membrane (CAM) of chicken embryos. In vitro, we further assayed the influence of TSPO on the invasive potential of U118MG cells.

RESULTS

TSPO knockdown increased tumor growth in both in-vivo models compared with the scrambled siRNA control. Angiogenesis was also increased by TSPO knockdown as determined by a CAM assay. TSPO knockdown led to a decrease in adhesion to the proteins of the extracellular matrix, including fibronectin, collagen I, collagen IV, laminin I, and fibrinogen. TSPO knockdown also led to an enhancement in the migratory capability of U118MG cells, as determined in a modified Boyden chamber. Application of the TSPO ligand 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK 11195) at a concentration of 25 µmol/l in the in-vitro models yielded results similar to those obtained on TSPO knockdown. We found no effects of PK 11195 on TSPO protein expression. Interestingly, at low nmol/l concentrations (around 1 nmol/l), PK 11195 enhanced adhesion to collagen I, suggesting a bimodal concentration effect of PK 11195.

CONCLUSION

Intact TSPO appears to be able to counteract the invasive and angiogenic characteristics related to the aggressiveness of U118MG glioblastoma cells in vivo and in vitro.

PET imaging of lung inflammation with [18F]FEDAC, a radioligand for translocator protein (18 kDa)

Purpose

The translocator protein (18 kDa) (TSPO) is highly expressed on the bronchial and bronchiole epithelium, submucosal glands in intrapulmonary bronchi, pneumocytes and alveolar macrophages in human lung. This study aimed to perform positron emission tomography (PET) imaging of lung inflammation with [¹⁸F]FEDAC, a specific TSPO radioligand, and to determine cellular sources enriching TSPO expression in the lung.

Methods

An acute lung injury model was prepared by intratracheal administration of lipopolysaccharide (LPS) to rat. Uptake of radioactivity in the rat lungs was measured with small-animal PET after injection of [¹⁸F]FEDAC. Presence of TSPO was examined in the lung tissue using Western blot and immunohistochemical assays.

Results

The uptake of [¹⁸F]FEDAC increased in the lung with the progress of inflammation by treatment with LPS. Pretreatment with a TSPO-selective ligand PK11195 showed a significant decrease in the lung uptake of [¹⁸F]FEDAC due to competitive binding to TSPO. TSPO expression was elevated in the inflamed lung section and its level responded to the [¹⁸F]FEDAC uptake and severity of inflammation. Increase of TSPO expression was mainly found in the neutrophils and macrophages of inflamed lungs.

Conclusion

From this study we conclude that PET with [¹⁸F]FEDAC may be a useful tool for imaging TSPO expression and evaluating progress of lung inflammation. Study on human lung using [¹⁸F]FEDAC-PET is promising.

The 18 kDa translocator protein (peripheral benzodiazepine receptor) expression in the bone of normal, osteoprotegerin or low calcium diet treated mice

The presence of the translocator protein (TSPO), previously named as the mitochondrial or peripheral benzodiazepine receptor, in bone cells was studied in vitro and in situ using RT-qPCR, and receptor autoradiography using the selective TSPO ligand PK11195.

In vitro, the TSPO is highly expressed in osteoblastic and osteoclastic cells.

In situ, constitutive expression of TSPO is found in bone marrow and trabecular bone, e.g., spongiosa. Mice with a reduction of bone turnover induced by a 4-day treatment of osteoprotegerin reduces [³H]PK11195 binding in the spongiosa (320±128 Bq.mg⁻¹, 499±106 Bq.mg⁻¹ in saline-treated controls). In contrast, mice with an increase in bone turnover caused by a 4-day low calcium diet increases [³H]PK11195 binding in the spongiosa (615±90 Bq.mg⁻¹).

Further, our study includes technical feasibility data on [¹⁸F]fluoride microPET imaging of rodent bone with altered turnover. Despite [¹⁸F]fluoride having high uptake, the in vivo signal differences were small. Using a phantom model, we describe the spillover effect and partial volume loss that affect the quantitative microPET imaging of the small bone structures in experimental mouse models.

In summary, we demonstrate the expression of TSPO in small rodent bone tissues, including osteoblasts and osteoclasts. A trend increase in TSPO expression was observed in the spongiosa from low to high bone turnover conditions. However, despite the potential utility of TSPO expression as an in vivo biomarker of bone turnover in experimental rodent models, our small animal PET imaging data using [¹⁸F]fluoride show that even under the condition of a good biological signal-to-noise ratio and high tracer uptake, the currently achievable instrument sensitivity and spatial resolution is unlikely to be sufficient to detect subtle differences in small structures, such as mouse bone.

Magnitude of [(11)C]PK11195 binding is related to severity of motor deficits in a rabbit model of cerebral palsy induced by intrauterine endotoxin exposure

Intrauterine inflammation is known to be a risk factor for the development of periventricular leukomalacia (PVL) and cerebral palsy. In recent years, activated microglial cells have been implicated in the pathogenesis of PVL and in the development of white matter injury. Clinical studies have shown the increased presence of activated microglial cells diffusely throughout the white matter in brains of patients with PVL. In vitro studies have reported that activated microglial cells induce oligodendrocyte damage and white matter injury by release of inflammatory cytokines, reactive nitrogen and oxygen species and the production of excitotoxic metabolites. PK11195 [1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline carboxamide] is a ligand that is selective for the 18-kDa translocator protein expressed on the outer mitochondrial membrane of activated microglia and macrophages. When labeled with carbon-11, [(11)C]PK11195 can effectively be used as a ligand in positron emission tomography (PET) studies for the detection of activated microglial cells in various neuroinflammatory and neurodegenerative conditions. In this study, we hypothesized that the magnitude of [(11)C]-(R)-PK11195 uptake in the newborn rabbit brain, as measured using a small-animal PET scanner, would match the severity of motor deficits resulting from intrauterine inflammation-induced perinatal brain injury. Pregnant New Zealand white rabbits were intrauterinely injected with endotoxin or saline at 28 days of gestation. Kits were born spontaneously at 31 days and underwent neurobehavioral testing and PET imaging following intravenous injection of the tracer [(11)C]-(R)-PK11195 on the day of birth. The neurobehavioral scores were compared with the change in [(11)C]PK11195 uptake over the time of scanning, for each of the kits. Upon analysis using receiver operating characteristic curves, an optimal combined sensitivity and specificity for detecting abnormal neurobehavioral scores suggestive of cerebral palsy in the neonatal rabbit was noted for a positive change in [(11)C]PK11195 uptake in the brain over time on PET imaging (sensitivity of 100% and area under the curve of >0.82 for all parameters tested). The strongest agreements were noted between a positive uptake slope - indicating increased [(11)C]PK11195 uptake over time - and worsening scores for measures of locomotion (indicated by hindlimb movement, forelimb movement, circular motion and straight- line motion; Cohen's κ >0.75 for each) and feeding (indicated by ability to suck and swallow and turn the head during feeding; Cohen's κ >0.85 for each). This was also associated with increased numbers of activated microglia (mean ratio ± SD of activated to total microglia: 0.96 ± 0.16 in the endotoxin group vs. 0.13 ± 0.08 in controls; p < 0.001) in the internal capsule and corona radiata. Our findings indicate that the magnitude of [(11)C]PK11195 binding measured in vivo by PET imaging matches the severity of motor deficits in the neonatal rabbit. Molecular imaging of ongoing neuroinflammation in the neonatal period may be helpful as a screening biomarker for detecting patients at risk of developing cerebral palsy due to a perinatal insult.

Positron emission tomography imaging of neuroinflammation

Injury to the central nervous system is characterized by localization of activated microglia at the site of injury. The peripheral benzodiazepine receptor expressed on the outer mitochondrial membrane of the activated microglia is a sensitive biomarker for the detection of this neuroinflammatory response to an insult. PK11195, an isoquinoline ligand that specifically binds peripheral benzodiazepine receptor, can be tagged with a positron emitter and used as a tracer for molecular imaging of this receptor in vivo by positron emission tomography (PET). [(11)C](R)PK11195 has been used in the imaging of various neuroinflammatory disorders, such as Alzheimer disease and multiple sclerosis. On the basis of our small-animal PET imaging studies using a neonatal rabbit model of maternal inflammation-induced cerebral palsy, we propose that PET imaging using [(11)C](R)PK11195 may be a valuable tool for detecting neuroinflammation in the brain of newborns born to mothers with chorioamnionitis.

Estradiol modulates uterine 18 kDa translocator protein gene expression in uterus and kidney of rats

We examined the effect of ovariectomy, with and without estradiol treatment, on 18 kDa translocator protein (TSPO) gene expression and its binding density in the uterus and kidney of rats. Ovariectomy causes a significant decrease in uterine, but not renal TSPO binding density, while estradiol treatment of ovariectomized rats restored TSPO binding density in the uterus. These TSPO density levels did not correlate with steady state or new RNA transcription. Our in vivo study suggests that estradiol is responsible for the maintenance of uterine TSPO density via transcriptional mechanisms. Our in vivo study also suggests that in the kidney estradiol appears to operate via post-transcriptional mechanisms to maintain TSPO density.

Radiomimetic Cell Cycle Delay Induced by Tetranodecanoyl Phorbol Acetate is Enhanced by Caffeine and by the Protein Kinase Inhibitor 2-aminopurine

The tumour promoter and protein kinase C agonist, 12-O-tetranodecanoyl-phorbol-13-acetate (TPA), has been reported to show a radiomimetic action because it transiently delays the passage of HeLa cells through the G2 phase, as do ionizing radiation and other DNA damaging agents. Caffeine is known to override the G2 delay imposed by DNA damage; it is shown here that caffeine does not override the radiomimetic delay imposed by TPA in HeLa, but instead enhances it, without affecting G2 progression in control cells. Most of the other agents which more specifically affect some of the diverse range of caffeine targets either do not affect G2 progression after TPA, or delay G2 progression in control cells and exert a further delay in the presence of TPA. The exception is 2-aminopurine, a protein kinase inhibitor which has been shown to have an action similar to that of caffeine is allowing progression of the cell cycle to mitosis after the inhibition of DNA synthesis, without affecting normal cycle progression through G2. This agent, like caffeine, also has the contrary action of retarding cycle progression after TPA. It is concluded that the G2 delays induced by ionizing radiation and by TPA operate by different mechanisms, which are modulated in opposite senses by mechanisms involving protein kinase inhibition.

A benzodiazepines derived compound, 4-(3-chlorophenyl)-1,3-dihydronaphtho [2,3-b][1,4]diazepin-2-one (ND700C), inhibits fMLP-induced superoxide anion release by activating protein phosphatase 2A in human neutrophils

We studied the mechanism underlying the inhibitory effect of a benzodiazepines derivative, 4-(3-chlorophenyl)-1,3-dihydronaphtho [2,3-b][1,4]diazepin-2-one (ND700C), on superoxide anion production induced by formly-methionyl-leucyl-phenylalanine (fMLP) in human neutrophils. ND700C inhibited the fMLP-induced superoxide anion production and cathepsin G release in a concentration-dependent manner with respective IC50 values of 5.0+/-0.5 and 8.7+/-0.8muM. In addition, ND700C was found to suppress fMLP-induced intracellular calcium mobilization and the phosphorylation of ERK and Akt. In another study, ND700C was observed to cause a rapid increase in intracellular cAMP level by up to threefold. Furthermore, when H89 was used to inhibit cAMP-dependent protein kinase A (PKA), we discovered that ND700C's suppressive effects on calcium mobilization, phosphorylation, and superoxide anion production were abrogated. ND700C demonstrated additive effect on the PGE1-induced increase in cAMP. However, this additive effect was not demonstrated with the IBMX-induced rise in cAMP. Our results indicated that ND700C did not directly inhibit the activity of phosphodiesterase 4. In another set of experiments, calyculin A and okadaic acid (both protein phosphatase 2A inhibitors) were found to reverse ND700C's positive effect on cAMP level. This observation suggested the involvement of protein phosphatase 2A in ND700C's cAMP-elevating mechanism. We found that the activity of protein phosphatase 2A was activated by ND700C. Furthermore, protein phosphatase 2A was co-immunoprecipitated with phosphodiesterase 4 after ND700C treatment in human neutrophils.

CONCLUSION

ND700C inhibited fMLP-induced superoxide anion production through a PKA-dependent pathway. ND700C increased cAMP by activating protein phosphatase 2A, which subsequently inhibited phosphodiesterase 4.

Translocator protein 18 kDa (TSPO): molecular sensor of brain injury and repair

For over 15 years, the peripheral benzodiazepine receptor (PBR), recently named translocator protein 18 kDa (TSPO) has been studied as a biomarker of reactive gliosis and inflammation associated with a variety of neuropathological conditions. Early studies documented that in the brain parenchyma, TSPO is exclusively localized in glial cells. Under normal physiological conditions, TSPO levels are low in the brain neuropil but they markedly increase at sites of brain injury and inflammation making it uniquely suited for assessing active gliosis. This research has generated significant efforts from multiple research groups throughout the world to apply TSPO as a marker of "active" brain pathology using in vivo imaging modalities such as Positron Emission Tomography (PET) in experimental animals and humans. Further, in the last few years, there has been an increased interest in understanding the molecular and cellular function(s) of TSPO in glial cells. The latest evidence suggests that TSPO may not only serve as a biomarker of active brain disease but also the use of TSPO-specific ligands may have therapeutic implications in brain injury and repair. This review presents an overview of the history and function of TSPO focusing on studies related to its use as a sensor of active brain disease in experimental animals and in human studies.

Peripheral benzodiazepine receptors on platelets of fibromyalgic patients

OBJECTIVE

The aim of the present study was to analyze if alterations of peripheral-type benzodiazepine receptor (PBR) characteristics occurred in platelet membranes of patients affected by primary fibromyalgia (FM).

DESIGN AND METHODS

Platelets were obtained from 30 patients with FM. Evaluation of kinetic parameters of PBR was performed using [(3)H] PK11195 as specific radioligand compared with 16 healthy volunteers.

RESULTS

The results showed a significant increase of PBR binding sites value in platelet membranes from FM patients (B(max) was 5366+/-188 fmol/mg vs. controls, 4193+/-341 fmol/mg, mean+/-SEM) (**p<0.01) but not for affinity value (K(d) was 4.90+/-0.39 nM vs. controls, 4.74+/-0.39 nM, mean+/-SEM) (p>0.05). Symptom severity scores (pain and tiredness) were positively correlated with B(max).

CONCLUSIONS

Our results showed an up-regulation of PBR in platelets of FM patients, and this seems to be related to the severity of fibromyalgic symptoms.

The peripheral-type benzodiazepine receptor and the cardiovascular system. Implications for drug development

Peripheral-type benzodiazepine receptors (PBRs) are abundant in the cardiovascular system. In the cardiovascular lumen, PBRs are present in platelets, erythrocytes, lymphocytes, and mononuclear cells. In the walls of the cardiovascular system, PBR can be found in the endothelium, the striated cardiac muscle, the vascular smooth muscles, and the mast cells. The subcellular location of PBR is primarily in mitochondria. The PBR complex includes the isoquinoline binding protein (IBP), voltage-dependent anion channel (VDAC), and adenine nucleotide transporter (ANT). Putative endogenous ligands for PBR include protoporphyrin IX, diazepam binding inhibitor (DBI), triakontatetraneuropeptide (TTN), and phospholipase A2 (PLA2). Classical synthetic ligands for PBR are the isoquinoline 1-(2-chlorophenyl)-N-methyl-N-(1-methyl-propyl)-3-isoquinolinecarboxamide (PK 11195) and the benzodiazepine 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (Ro5 4864). Novel PBR ligands include N,N-di-n-hexyl 2-(4-fluorophenyl)indole-3-acetamide (FGIN-1-27) and 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide (SSR180575), both possessing steroidogenic properties, but while FGIN-1-27 is pro-apoptotic, SSR180575 is anti-apoptotic. Putative PBR functions include regulation of steroidogenesis, apoptosis, cell proliferation, the mitochondrial membrane potential, the mitochondrial respiratory chain, voltage-dependent calcium channels, responses to stress, and microglial activation. PBRs in blood vessel walls appear to take part in responses to trauma such as ischemia. The irreversible PBR antagonist, SSR180575, was found to reduce damage correlated with ischemia. Stress, anxiety disorders, and neurological disorders, as well as their treatment, can affect PBR levels in blood cells. PBRs in blood cells appear to play roles in several aspects of the immune response, such as phagocytosis and the secretion of interleukin-2, interleukin-3, and immunoglobulin A (IgA). Thus, alterations in PBR density in blood cells may have immunological consequences in the affected person. In conclusion, PBR in the cardiovascular system may represent a new target for drug development.

Imaging the peripheral benzodiazepine receptor response in central nervous system demyelination and remyelination

We used a rodent model of cuprizone-induced demyelination to examine the peripheral benzodiazepine receptor (PBR) response during remyelination. C57BL/6J mice were fed a 0.2% cuprizone-containing or control diet for 3 weeks and then removed to allow for remyelination. Quantitative autoradiography of 3H-(R)-PK11195 binding to PBR in the corpus callosum showed increased levels at 3 weeks of demyelination and gradually decreased as a function of remyelination. PBR levels were associated with the degree of remyelination and activation of microglia and astrocytes. However, the temporal pattern suggests that the PBR signal during the late stages of remyelination was primarily associated with astrocytes. We also used small-animal positron-emission tomography (PET) imaging to determine if this technique could be used to monitor PBR levels in the brain of living mice. The results indicate that 11C-(R)-PK11195 levels are significantly elevated in the mouse brain during cuprizone-induced demyelination and normalize at a time in which remyelination is complete. These findings support the notion that PBR is a sensitive marker for the visualization and quantification of brain injury and recovery. Further, the in vivo imaging of the PBR response is now possible in the living rodent brain.

Implication of glucocorticoid in anti-inflammatory effects of Ro5-4864 in mouse pleurisy induced by carrageenan

Mouse pleurisy induced by carrageenan is used to determine the mechanism of anti-inflammatory action of 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2-H-1,4-benzodiazepin-2 (Ro5-4864). Pre-treatment with Ro5-4864 inhibits different inflammatory parameters, such as neutrophil influx, MPO activity and NO levels in the early phase (4 h), as well as mononuclear cells and ADA activity in the late phase (48 h) of pleurisy. dl-Aminoglutethimide, inhibitor of steroidal synthesis, reverted the effect of Ro5-4864 on these different inflammatory parameters. Our results suggest that anti-inflammatory action of Ro5-4864 may be partly due to its capacity to inhibit leukocyte migration, as well as leukocyte activation and formation of NO by a mechanism dependent on glucocorticoids.

The peripheral GABAergic system as a target in endocrine disorders

In addition to its well-recognized function as a cerebral inhibitory transmitter, less well established is the role of GABA in peripheral nervous and endocrine systems. We summarize current evidence that GABA serves as a neurotransmitter or neuromodulator in the autonomic nervous system and as a hormone or trophic factor in non-neuronal peripheral tissue as well. GABA is widely distributed in endocrine tissues including the pituitary, pancreas, adrenal glands, uterus, ovaries, placenta and testis. Moreover, GABA is involved in the pathophysiology of endocrine disorders such as diabetes mellitus, diseases of adrenal glands and reproductive tracts. Current literature indicates that the peripheral GABA system in the autonomic nervous system, endocrine and immune systems is as yet nearly an unexplored target for diagnosis and drug treatment.

In Vivo Imaging of Peripheral Benzodiazepine Receptors in Mouse Lungs: A Biomarker of Inflammation

The ability to visualize the immune response with radioligands targeted to immune cells will enhance our understanding of cellular responses in inflammatory diseases. Peripheral benzodiazepine receptors (PBR) are present in monocytes and neutrophils as well as in lung tissue. We used lipopolysaccharide (LPS) as a model of inflammation to assess whether the PBR could be used as a noninvasive marker of inflammation in the lungs. Planar imaging of mice administrated 10 or 30 mg/kg LPS showed increased [123I]-( R)-PK11195 radioactivity in the thorax 2 days after LPS treatment relative to control. Following imaging, lungs from control and LPS-treated mice were harvested for ex vivo gamma counting and showed significantly increased radioactivity above control levels. The specificity of the PBR response was determined using a blocking dose of nonradioactive PK11195 given 30 min prior to radiotracer injection. Static planar images of the thorax of nonradioactive PK11195 pretreated animals showed a significantly lower level of radiotracer accumulation in control and in LPS-treated animals ( p < .05). These data show that LPS induces specific increases in PBR ligand binding in the lungs. We also used in vivo small-animal PET studies to demonstrate increased [11C]-( R)-PK11195 accumulation in the lungs of LPS-treated mice. This study suggests that measuring PBR expression using in vivo imaging techniques may be a useful biomarker to image lung inflammation.

Decreased density of peripheral benzodiazepine receptors in psychiatric patients after a suicide attempt

To date, two main types of benzodiazepine (BDZ) receptors have been identified: one of these is the so-called central receptor which is found mainly in the cortex, limbic areas and cerebellum, and the other is known as the peripheral receptor, which is found in the kidneys, lungs, ovaries, testes, adrenal glands and blood cells, but is present also in the central nervous system (CNS), in particular in glial cells. Although for some time the peripheral BDZ receptor has been considered an acceptor site with no pharmacological activity, recent data have suggested that it may be involved in a variety of actions, such as the response to stress. The presence of these receptors in blood platelets, which are considered a reliable, peripheral mirror of the same structures located in the SNC, prompted us to evaluate them in a group of psychiatric patients after a suicide attempt, as compared with healthy control subjects, by means of the specific binding of 3H-PK 11195. Suicide, with no doubt, may be considered one of the most stressful situations occurring to humans. The results showed the presence of a significant decrease in the density of 3H-PK 11195 binding sites in the patients, as compared with healthy control subjects. This finding may represent a non-specific indicator of a condition of stress, since peripheral BDZ receptors are modulated by stress and hormones, or it may result more from an abnormal metabolism of steroid substances which could play a pivotal role in the development of vulnerability towards suicide.

Changes in peripheral benzodiazepine receptors in patients with bipolar disorder

Peripheral benzodiazepine (BDZ) receptors were investigated by means of the binding of the specific ligand (3)H-PK 11195 to platelet membranes in patients suffering from bipolar disorder and in healthy controls. The results showed that the density (Bmax) of peripheral BDZ receptors was significantly higher in patients than in control subjects, with no change in the dissociation constant. No correlation with demographic or clinical features was observed. These findings would suggest that alterations of peripheral BDZ receptors are present in patients suffering from bipolar disorder, but it is premature to conclude whether they may be related to the pathophysiology of the disorder, or are secondary to changes occurring in other systems, such as those regulating the stress response.

[3H]PK11195 binding sites in human neutrophils: effect of fMLP stimulation and modulation in rheumatic diseases

OBJECTIVE

The objectives of this study were to evaluate the [3H]PK11195 binding parameters in a model of acute inflammation, the N-formylmethionine-leucine-phenylalanine (fMLP)-stimulated neutrophil cell membranes, and to analyze if alterations of peripheral-type benzodiazepine receptor (PBR) characteristics occurred in neutrophil cell membranes of patients affected by osteoarthritis (OA), rheumatoid arthritis (RA), and psoriasic arthritis (PA).

DESIGN AND METHODS

Neutrophils were obtained from 15 patients with OA, 15 patients with RA, and 15 patients with PA. fMLP stimulation was performed to aliquots of neutrophils from six healthy individuals. Evaluation of kinetic parameters of PBR was performed using [3H]PK11195, as specific radioligand compared with 15 healthy volunteers.

RESULTS

The results showed a significant decrease of Kd and Bmax in fMLP-stimulated neutrophil membranes. Moreover, an increase of PBR binding sites and affinity value was observed in neutrophils membranes from PA patients.

CONCLUSIONS

Our data suggested a fMLP modulation on [3H]PK11195 binding in human neutrophils. Moreover, our results showed an up-regulation of PBR in neutrophils of PA patients.

Peripheral-type benzodiazepine receptor density and in vitro tumorigenicity of glioma cell lines

The peripheral-type benzodiazepine receptor is found primarily on the outer mitochondrial membrane and consists of three subunits: the 18kDa isoquinoline binding protein, the 32kDa voltage-dependent anion channel, and the 30kDa adenine nucleotide transporter. The current study evaluates the potential importance of peripheral-type benzodiazepine receptor expression in glioma cell tumorigenicity. While previous studies have suggested that peripheral-type benzodiazepine receptor-binding may be relatively increased in tumor tissue and cells, so far, little is known about the relationships between peripheral-type benzodiazepine receptor density and factors underlying tumorigenicity. In the present study, we found in glioma cell lines (C6, U87MG, and T98G), that peripheral-type benzodiazepine receptor ligand-binding density is relatively high for C6 and low for T98G, while U87MG displays intermediate levels. Cell growth of these cell lines in soft agar indicated that high levels of peripheral-type benzodiazepine receptor-binding were associated with increased colony size, indicative of their ability to establish anchorage independent cell proliferation. Potential causes for differences in tumorigenicity between these cell lines were suggested by various cell death and proliferation assays. Cell death, including apoptosis, appeared to be low in C6, and high in T98G, while U87MG displayed intermediate levels in this respect. Cell proliferation appeared to be high in C6, low in T98G, and intermediate in U87MG. In conclusion, our study suggests that relatively high peripheral-type benzodiazepine receptor-binding density is associated with enhanced tumorigenicity and cell proliferation rate. In particular, apoptosis appears to be an important tumorigenic determinant in these glioma cell lines. Moreover, application of PBR-specific ligands indicated that PBR indeed are functionally involved in apoptosis in glioma cells.

Expression of the peripheral benzodiazepine receptor triggers thymocyte differentiation

In the thymus, during T-cell differentiation, the expression of the peripheral benzodiazepine receptor (PBR) modulates. The protein level decreases between the double negative and double positive stages, and then increases when thymocytes become single positive. We addressed the role played by PBR in T-cell maturation. To this aim, we used Jurkat cells, which are immature T lymphocytes derived from an acute lymphoblastic leukemia. These cells are PBR negative and were stably transfected to achieve PBR levels similar to that in mature T cells. Using the DNA chip technology, we analyzed the PBR expression-dependent gene changes and evidenced that PBR-expressing cells exhibited more mature features than mock-transfected ones. A majority of the modulated genes encode proteins playing direct or indirect roles during the lymphocyte maturation process. In particular, PBR expression induced several differentiation markers (such as CD1, CD6), or key regulating elements (e.g., RAG1, RAG2, CD99, TCR). By contrast, some regulators of TCR signaling were reduced. PBR expression also affected the expression of critical apoptosis regulators: the proapoptotic lipocortin I, galectin-1, and galectin-9 were reduced while the antiapoptotic Bcl-2 was induced. Altogether our results supported the hypothesis that PBR controls T-cell maturation and suggested mechanisms through which PBR may regulate thymocyte-positive selection.

Effects of acute and long-term diazepam administrations on neutrophil activity: a flow cytometric study

This study analyzed the effects of acute and long-term diazepam treatments on rat peripheral blood neutrophil activity and cortisol serum levels. Rats were acutely and long-term (21 days, once daily) treated with diazepam (10 mg/kg) or its vehicle (1.0 ml/kg). Blood was collected 1 h after treatments for flow cytometric analysis of neutrophil oxidative burst and phagocytosis. Corticosterone and diazepam concentrations were also determined. Results showed that: (1) both diazepam treatments increased lipopolysaccharide (LPS) and phorbol myristate acetate (PMA)-induced neutrophil oxidative burst; (2) the increase in oxidative burst after Staphylococcus aureus induction in acutely treated animals was higher than that observed after long-term treatment; (3) phagocytosis is increased by acute diazepam treatment and decreased by a long-term regimen; (4) acute, but not long-term, diazepam treatment increased corticosterone levels; (5) diazepam plasmatic levels after acute and long-term treatments were not different. These results indicate the development of tolerance to diazepam effects on corticosterone serum levels but not on neutrophil activity.

Chemotherapeutics and hormesis

This article represents the first comprehensive assessment of hormetic effects of chemotherapeutic agents. Hormetic dose-response relationships were reported for a wide range of chemotherapeutics, including antibiotics, antiviral, and antitumor agents as well as substances that affect hair growth, prostate function, cognitive performance, and numerous other endpoints. Particular attention was given to assessing the quantitative features of the dose response, the underlying mechanistic features of the biphasic nature of the dose response, and the clinical implications of hormetic responses. Recognition of the hormetic-like biphasic nature of the dose response is expected to have an important impact on the design of experiments to assess chemotherapeutics and how such agents may be employed more successfully in clinical applications.

Comparison of two PBR ligands with classical antiinflammatory drugs in LPS-induced arthritis in rats

The antinociceptive and anti-edematogenic effects of peripheral benzodiazepine receptor (PBR) ligands, Ro5-4864 (7-chloro-5- (4-chlorophenyl)-1,3-dihydro-1-methyl-2-H-1,4-benzodiazepine-2) and PK11195 (1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide), were studied in an experimental model of carrageenan/LPS -induced arthritis in rats. These effects were compared with those of indomethacin and dexamethasone. Both pre and post-treatments with PK11195 were found to be anti-edematogenic and antinociceptive. The lower dose (0.01 mg/kg) exhibited the higher anti-edematogenic effect. On the other hand, the higher dose (0.5 mg/kg) produced antinociception, but with a decreased anti-edematogenic effect. Ro5-4864 produced a negligible antinociception and anti-edematogenic effect as pretreatment, but a pro-edematogenic effect when given as post-treatment. Dexamethasone and indomethacin presented parallel and dose-dependent antinociceptive and anti-edematogenic effects. In conclusion, PK11195 can effectively diminish arthritic nociception and edema elicited by LPS, but probably by mechanisms different from those of dexamethasone or indomethacin. RO5-4864 seemed to have opposite effect on this model.

Peripheral-type benzodiazepine receptors in human mononuclear cells of patients affected by osteoarthritis, rheumatoid arthritis or psoriasic arthritis

OBJECTIVES

The objective of this study was to evaluate the kinetic parameters at equilibrium of peripheral benzodiazepine receptors (PBR) in human mononuclear cells from patients affected by osteoarthritis (OA), rheumatoid arthritis (RA) and psoriasic arthritis (PA).

DESIGN AND METHODS

Mononuclear cells were obtained from 10 patients with OA, 10 patients with RA and 10 patients with PA. Evaluation of kinetic parameters of PBR was performed using [(3)H]PK 11195, a specific radioligand for this receptor, and compared with 10 healthy controls.

RESULTS

The results show a statistically significant decrease (37.5%, as an absolute percentage) in the maximal number of binding sites (B(max)) of patients with OA, compared with healthy controls; however, the values of the dissociation constant (K(d)) at equilibrium do not show any statistically significant variations.

CONCLUSIONS

These data further confirm the presence of peripheral biochemical alterations in OA. As peripheral benzodiazepine receptors appear to be involved in the immune function, and in the protection of hematopoietic cells against oxygen radical damage, the observed decrease in B(max) might be related to cellular protection.

Effects on free radical generation by ligands of the peripheral benzodiazepine receptor in cultured neural cells

The effect of peripheral benzodiazepine receptor (PBR) ligands on free radical production was investigated in primary cultures of rat brain astrocytes and neurons as well as in BV-2 microglial cell lines using the fluorescent dye dichlorofluorescein-diacetate. Free radical production was measured at 2, 30, 60 and 120 min of treatment with the PBR ligands 1-(2-chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide (PK11195), 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (Ro5-4864) and protoporphyrin IX (PpIX) (all at 10 nm). In astrocytes, all ligands showed a significant increase in free radical production at 2 min. The increase was short-lived with PK11195, whereas with Ro5-4864 it persisted for at least 2 h. PpIX caused an increase at 2 and 30 min, but not at 2 h. Similar results were observed in microglial cells. In neurons, PK11195 and PpIX showed an increase in free radical production only at 2 min; Ro5-4864 had no effect. The central-type benzodiazepine receptor ligand, clonazepam, was ineffective in eliciting free radical production in all cell types. As the PBR may be a component of the mitochondrial permeability transition (MPT) pore, and free radical production may occur following induction of the MPT, we further investigated whether cyclosporin A (CsA), an inhibitor of the MPT, could prevent free radical formation by PBR ligands. CsA (1 micro m) completely blocked free radical production following treatment with PK11195 and Ro5-4864 in all cell types. CsA was also effective in blocking free radical production in astrocytes following PpIX treatment, but it failed to do so in neurons and microglia. Our results indicate that exposure of neural cells to PBR ligands generates free radicals, and that the MPT may be involved in this process.

Involvement of the peripheral benzodiazepine receptor in the development of rheumatoid arthritis in Mrl/lpr mice

In this study, the effects of different peripheral benzodiazapine receptor ligands: PK 11195 [1-(2-chloro-phenyl)-N-methyl-N-(1-methylpropyl)-1-isoquinoline carboxamide], Ro5-4864 [7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one] and the newly described SSR 180575 (7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridozine[4,5-b] indole-1-acetamide) were analysed on the progression and severity of rheumatoid arthritis in vivo in the Mrl/lpr mice model, following chronic treatment (at 3 mg/kg, i.p. for 30 days). We found that peripheral benzodiazepine receptor ligands have significant beneficial therapeutic action on the development of spontaneous rheumatoid arthritis-like signs. Concomitantly, we mapped immunoreactive peripheral benzodiazepine receptor in inflamed tissues, and we observed that in addition to the infiltrated leukocytes, peripheral benzodiazepine receptor was expressed in synovial membranes, at the cartilage pannus junction and in chondrocytes. Interestingly, we observed that peripheral benzodiazepine receptor expression in chondrocytes was reduced when Mrl/lpr mice developed the pathology and restored upon peripheral benzodiazepine receptor ligand treatment. Altogether, our data provide further evidence of a role played by peripheral benzodiazepine receptor in the regulation of inflammation processes and support new therapeutic applications for specific potent peripheral benzodiazepine receptor ligands.

Peripheral benzodiazepine receptor mapping in rat kidney. Effects of angiotensin II-induced hypertension

Intrarenal distribution and function(s) of the peripheral benzodiazepine receptor (PBR) remain uncertain. The goals of this study were to (1) develop a specific anti-rat PBR antibody and (2) map intrarenal immunoreactive PBR (irPBR) in untreated rats and in rats that received chronic angiotensin II infusion (200 ng/kg per min, subcutaneously, 17 d). A polyclonal rabbit antibody was raised against the C-terminal end of rat PBR (aa 159 to 169). The antibody specifically recognized a single 18-kD protein in whole kidney extracts, and confocal microscopy showed exclusive mitochondrial localization of irPBR in cultured rat glial C6 cells. In control rats, irPBR was found along thick ascending limbs of Henle's loops, including the macula densa area, along distal tubules, and along collecting ducts. Vascular smooth-muscle cells were PBR-positive. General irPBR distribution was unaffected by angiotensin II treatment (systolic BP, 205 +/- 9 mmHg). However, irPBR appeared in parietal glomerular epithelial cells, atrophic proximal tubules, and infiltrating mononuclear cells. In conclusion, the results suggest previously unsuspected roles of PBR in the control of glomerular dynamics and in proximal tubular injury/repair processes.

Effect of midazolam on interleukin-6 mRNA expression in human peripheral blood mononuclear cells in the absence of lipopolysaccharide

Midazolam, a benzodiazepine, has an hypnotic effect via benzodiazepine receptors and is widely used as an anaesthetic. Recently, it has been suggested that benzodiazepines modulate cytokine responses. The purpose of the present study was to evaluate the effect of midazolam on interleukin-6 (IL-6) response by observing mRNA expression levels in human peripheral blood mononuclear cells (PBMCs) in the absence of lipopolysaccharide (LPS). PBMCs were isolated from healthy volunteers in endotoxin-free 0.9% sodium chloride solution. The cells were incubated for 2 h at 37 degrees C immediately after isolation. IL-6 mRNA expression levels in the cells were quantified using reverse transcription and competitive polymerase chain reaction. It was found that midazolam time-dependently inhibited the IL-6 mRNA expression in PBMCs in the absence of LPS, and significantly inhibited the IL-6 mRNA expression at 1 microg/ml (P<0.05) or 10 microg/ml (P<0.01) in the absence of LPS. However, neither a specific agonist of peripheral-type benzodiazepine receptors, Ro5-4864, nor a specific agonist of central-type benzodiazepine receptors, clonazepam, inhibited IL-6 mRNA expression. These findings indicated a suppression of the IL-6 response in human PBMCs by midazolam in the absence of LPS, and suggests that midazolam has its effect not via benzodiazepine receptors, but by another mechanism.

1,5-Benzodiazepine tricyclic derivatives exerting anti-inflammatory effects in mice by inhibiting interleukin-6 and prostaglandinE(2)production

The 1,4- and the 1,5-benzodiazepines (BDZ) are commonly used as anxiolytic and anticonvulsive drugs. It has been suggested that they influence, particularly through stimulation of peripheral BDZ receptors, some immune cell properties such as pro-inflammatory cytokine production. The availability of a new class of [1,2,4]triazolo[4,3-a][1,5]benzodiazepine derivatives (compounds IV), endowed with anti-inflammatory and/or analgesic properties but no anti-pentylenetetrazole activity, prompted us to investigate in more detail the anti-inflammatory properties of three selected compounds IV (N,N-dimethyl-1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benz- odiazepin-5-amine; N,N-dibutyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine; 1-methyl-N,N-dimethyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine) and one structurally related compound (1-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5(6H)-one). These BDZ derivatives have lost their affinity for the central and peripheral BDZ receptors. The in vivo effect on leukocyte migration of these compounds was investigated by using the mouse air-pouch model of local inflammation. Compounds A and B, significantly inhibited the carrageenan-induced leukocyte recruitment in a dose-dependent manner starting from the dose of 50 mgkg(-1), whereas compound C was effective only at the higher dose of 100 mgkg(-1). Compound D did not exert such effects at any of the doses considered. The effect of compounds A, B and C on leukocyte recruitment was paralleled by a significant inhibition of interleukin-6 and prostaglandin E(2)production in the exudate, similarly to indomethacin, and by a partial reduction of vascular permeability. These features may be relevant for the design and development of innovative anti-inflammatory molecules among the 4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amine derivatives.

Peripheral-type benzodiazepine receptor ligands: mitochondrial permeability transition induction in rat cardiac tissue

Strong evidence is emerging that mitochondrial permeability transition (MPT) may be important in certain physiological conditions and, above all, in the processes of cell damage and death. Reversible MPT, triggered by inducing agents in the presence of calcium ions, has resulted in the opening of a dynamic multiprotein complex formed in the inner mitochondrial membrane and has caused large-amplitude mitochondrial swelling. In the present work, the exposure of de-energized rat cardiac mitochondria to peripheral benzodiazepine receptor (PBR) ligands (1-(2-chlorophenyl-N-methyl-1-methylpropyl)-3-isoquinolinecarboxamide (PK 11195), 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (Ro5-4864), and diazepam) produced a dose-dependent and cyclosporin A (CSP)-sensitive loss of absorbance, which was indicative of mitochondrial swelling. By contrast, the addition of a high-affinity central benzodiazepine receptor ligand (clonazepam) was ineffective, even at the highest concentration tested. The ultrastructural changes associated with swelling were similar in mitochondria exposed either to PK 11195 or to calcium. Supporting the apoptotic role of PK 11195-induced swelling, supernatants from mitochondria that had undergone permeability transition caused apoptotic changes in isolated cardiac nuclei. In addition, ultrastructural abnormalities were observed in rat cardiac tissue following in vivo PK 11195 administration, with these abnormalities being prevented by CSP co-administration. These data indicate that PBR ligands induce mitochondrial permeability transition and ultrastructural alterations in isolated cardiac mitochondria as well as in myocardiocytes, suggesting a novel strategy for studying the implication of PBR ligands as apoptosis inducers, through a probable effect on the MPT pore.

Effects of different preparations of propofol, diazepam, and etomidate on human neutrophils in vitro

BACKGROUND

Intravenous anaesthetics and sedatives can influence polymorphonuclear cell (PMN) functions. Some of the drugs for sedation and anaesthesia have been alternatively dissolved in lipid solutions containing medium (MCT) and/or long chain (LCT) triglycerides. The in vitro effects of two different diazepam (benzyl-alcohol, LCT/MCT), etomidate (propylene-glycol, LCT/MCT), and propofol (LCT, LCT/MCT) preparations on respiratory burst (RB) and phagocytosis of human PMNs were studied.

METHODS

Diazepam (2, 20 microg ml(-1)), etomidate (0.5, 5 microg ml(-1)), and propofol (6, 60 microg ml(-1)) were investigated in clinical and 10-fold concentrations with flow cytometric assays. The RB was measured with the fluorescent dye rhodamine after induction with Escherichia coli or formyl-methionyl-leucylphenylalanine (FMLP) following priming with tumour necrosis factor alpha (TNF-alpha). Phagocytosis of PMNs was carried out in whole blood after incubation with fluorescein-labelled E. coli.

RESULTS

LCT-propofol at 60 microg ml(-1) reduced the percentage of PMNs with RB activity after induction with E. coli (52.8+/-20.4) and TNF-alpha/FMLP (10.8+/-5.1)) as well as the percentage of phagocytosing PMNs (48.9+/-19.5) in contrast to LCT/MCT-propofol, which augmented all parameters (85.4+/-10.1, 50.3+/-12.7, 66.5+/-12.5). Also the higher concentrations of LCT/MCT-diluted etomidate and diazepam increased the percentage of RB positive PMNs compared to the alternative compositions. The percentage of phagocytosing PMNs was less reduced with 20 microg ml(-1) LCT/MCT-diazepam (85.2+/-6.9) than with the same concentration of benzyl-alcohol diluted diazepam (68.8+/-12.2) compared to the control.

CONCLUSION

The in vitro effects of diazepam, etomidate, and propofol are dependent on the solvent applied. The tested LCT/MCT preparations reduce the inhibitory effects on the bacterial killing capacity of PMNs found after incubation with propyleneglycol, benzyl-alcohol, or LCT preparations, respectively.

Anti-inflammatory effects of peripheral benzodiazepine receptor ligands in two mouse models of inflammation

In vivo treatment of mice with peripheral benzodiazepine receptor ligands exerts an inhibitory effect on the inflammatory response in two models of acute inflammation. In the first model, pretreatment of the animals (24 h) with 1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide (PK11195) and 7-chloro-5-(4-Chlorophenyl)-1, 3-dihydro-1-methyl-2-H-1,4-benzodiazepin-2 (Ro5-4864), at different doses (0.00001-10 mg/kg, i.p.) dose dependently inhibited the formation of mouse paw oedema induced by carrageenan with mean ID(50s) of 0.009 (95% confidence limits=0.0076-0.013) and 0.04 (95% confidence limits=0.025-0.0086) mg/kg, respectively. Both ligands (0. 1 mg/kg, i.p.) inhibited in the same way the mouse paw oedema induced by carrageenan in animals with and without adrenal glands. PK11195 and Ro5-4864 (0.1 mg/kg, i.p.) inhibited the mouse paw oedema induced by several inflammatory mediators. In the second model, the pretreatment (24 h) with peripheral benzodiazepine receptor ligands (0.1 mg/kg, i.p.) exerted an inhibitory effect on neutrophil influx and produce a marked inhibition of carrageenan-produced interleukin-13 and interleukin-6 in pleural exudation. Our results extend previous findings that peripheral benzodiazepine receptor is involved in the inflammatory response, and suggest that this action may be linked to the action of different inflammatory mediators, probably mainly by the inhibition of the release of pro-inflammatory cytokines.

Increased expression of peripheral benzodiazepine receptors on leukocytes in silent myocardial ischemia

OBJECTIVES

The purpose of this study was to evaluate benzodiazepine receptor expression on leukocytes from patients with symptomatic or silent myocardial ischemia.

BACKGROUND

Silent myocardial ischemia is frequently observed in patients with coronary artery disease. Pain can be effectively controlled by various endogenous mechanisms. Benzodiazepines and their receptors play key roles in pain, in interactions with peptide opioids, in inflammation and in the response to stress.

METHODS

The study group consisted of 57 patients with reproducible exercise-induced myocardial ischemia. The presence of a constant behavior in the anginal pain perception during both exercise-induced ischemia and daily life was the most important inclusion criterion. Venous blood samples were taken from all patients to evaluate the expression of peripheral benzodiazepine receptors by flow cytometry. The study cohort was classified into two groups: 24 patients who had anginal pain both at home and during the exercise stress test and 33 patients who were asymptomatic during both daily life and exercise-induced ischemia.

RESULTS

Flow cytometry analysis showed increased expression of peripheral benzodiazepine receptors on all types of leukocytes in the asymptomatic patients. The difference was statistically significant for lymphocytes (p < 0.005), monocytes (p < 0.001) and granulocytes (p < 0.001).

CONCLUSIONS

These data show that expression of peripheral benzodiazepine receptors was higher in patients with silent myocardial ischemia than in symptomatic patients.

Inhibitory action of 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) on some mononuclear phagocyte functions

Peripheral benzodiazepine receptors (PBRs) are widely distributed throughout the body, but their functions are unknown. They are found on mononuclear phagocytes, and they are up-regulated in a number of neurological and other disease states. We explored the functional consequences of PBR ligand binding to mononuclear-derived cells using the high-affinity ligands 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) and 4'-chlorodiazepam (7-chloro-5-(4'-chlorophenyl)-1, 3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one; Ro 5-4864). The functions were the following: respiratory burst; secretion of glutamate, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha); toxicity of culture supernatants towards SH-SY5Y human neuroblastoma cells; and expression of the inflammatory surface markers HLA-DR and Fcgamma RII (CDw32). PK 11195 inhibited the respiratory burst response, reduced release of glutamate and IL-1beta, and suppressed secretion of products cytotoxic to neuronal cells. Selectivity was suggested by the failure of PK 11195 to influence TNF-alpha secretion or expression of HLA-DR and CDw32. Powerful ligands of PBRs, such as PK 11195, may be useful inhibitors of selective macrophage functions, retarding both local and systemic inflammation. Since PK 11195 readily enters the brain, it may be beneficial in treating central as well as peripheral inflammatory diseases.