Immunomodulatory effect of peripheral benzodiazepine receptor ligands on human mononuclear cells

The preventative effect of of Ro5-4864 (peripheral benzodiazepine receptor agonist) on spinal epidural fibrosis after laminectomy in a rat model

OBJECTIVE

To investigate the histopathological effects of a peripheral benzodiazepine receptor agonist (Ro5-4864) on epidural fibrosis (EF) in an experimental study model (post-laminectomy) in rats.

METHODS

A total of 32 albino Wistar rats were randomly divided into four equal groups (n = 8). In Group 1, no treatment was applied after laminectomy (control group). In Group 2, hemostasis was achieved after Laminectomy, and the surgical procedure was terminated by placing a 2-mm absorbable gelatin sponge dipped in saline into the epidural space. In Group 3, low-dose (4 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. In Group 4, high-dose (8 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. A histopathological examination was performed to evaluate arachnoidal invasion and EF.

RESULTS

Our data revealed the EF was significantly reduced in rats treated with high-dose Ro5-4864 (Group 4) compared to the control and saline-soaked Spongostan groups (p = 0.000 and p = 0.006, respectively). There was no significant difference between the groups treated with high- and low-dose Ro5-4864. Arachnoidal invasion was not seen in any of the rats in the high-dose R05-4864 group. However, the arachnoidal invasion results did not significantly differ between the study groups (p = 0.052 = 0.05).

CONCLUSIONS

Our study showed that Ro5-4864 could be effective in reducing EF in rats after.

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.

TSPO-ligands prevent oxidative damage and inflammatory response in C6 glioma cells by neurosteroid synthesis

Translocator protein 18kDa (TSPO) is predominantly located in the mitochondrial outer membrane, playing an important role in steroidogenesis, inflammation, cell survival and proliferation. Its expression in central nervous system, mainly in glial cells, has been found to be upregulated in neuropathology, and brain injury. In this study, we investigated the anti-oxidative and anti-inflammatory effects of a group of TSPO ligands from the N,N-dialkyl-2-phenylindol-3-ylglyoxylamide class (PIGAs), highlighting the involvement of neurosteroids in their pharmacological effects. To this aim we used a well-known in vitro model of neurosteroidogenesis: the astrocytic C6 glioma cell line, where TSPO expression and localization, as well as cell response to TSPO ligand treatment, have been established. All PIGAs reduced l-buthionine-(S,R)-sulfoximine (BSO)-driven cell cytotoxicity and lipid peroxidation. Moreover, an anti-inflammatory effect was observed due to the reduction of inducible nitric oxide synthase and cyclooxygenase-2 induction in LPS/IFNγ challenged cells. Both effects were blunted by aminoglutethimide (AMG), an inhibitor of pregnenolone synthesis, suggesting neurosteroids' involvement in PIGA protective mechanism. Finally, pregnenolone evaluation in PIGA exposed cells revealed an increase in its synthesis, which was prevented by AMG pre-treatment. These findings indicate that these TSPO ligands reduce oxidative stress and pro-inflammatory enzymes in glial cells through the de novo synthesis of neurosteroids, suggesting that these compounds could be potential new therapeutic tools for the treatment of inflammatory-based neuropathologies with beneficial effects possibly comparable to steroids, but potentially avoiding the negative side effects of long-term therapies with steroid hormones.

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.

Diazepam decreases leukocyte-endothelium interactions in situ

High doses of diazepam reduce the inflammatory paw edema in rats. This effect was attributed to an action of diazepam on the Translocator Protein (TSPO). We evaluated the effects of diazepam (10 mg/kg, intraperitoneally) on leukocyte rolling and migration. In carrageenan-induced acute inflammation, diazepam decreased the interaction of leukocytes with endothelial cells (rolling) and the number of leukocytes in the mesentery (migration). RU486 (antagonist of glucocorticoid receptors) reduced the effects of diazepam on leukocyte rolling and migration, suggesting a participation of endogenous corticosteroids. We also showed that the effects of diazepam on leukocyte-endothelium interactions are mediated by nitric oxide (NO), since prior treatment with l-arginine (precursor of NO) partially precludes the inhibitory effects of diazepam; conversely, pretreatment with L-NAME (false substrate of the NO synthase) somewhat potentiates the effects of diazepam. The pathways that underlie the effects of diazepam remain to be further elucidated, but we believe that both local and systemic mechanisms may overlap to explain the influence of diazepam on leukocyte-endothelium interactions.

Effects of different doses and schedules of diazepam treatment on lymphocyte parameters in rats

Benzodiazepines (BZD) are widely used for the treatment of anxiety. They enhance GABA-ergic neurotransmission through the binding on specific BDZ recognition sites, within the GABA(A) receptor-ion channel complex. However, recent studies showed that BZD also act on peripheral benzodiazepine receptor sites (PBR) or translocator protein 18 kDa (TSPO). Evidence for a direct immunomodulatory action for BZD emerged from studies that demonstrated the presence of TSPO on immune/inflammatory cells. The present study was designed to analyze the effects of diazepam on rat lymphocyte parameters, specifically on phenotype, cell proliferation and cell death. The effects of both acute and long-term (21 days) diazepam (1 and 10 mg/kg/day) administrations were evaluated. Results showed that diazepam (1 mg/kg) treatment did not change the immune parameters analyzed. However, both diazepam (10 mg/kg) acute and long-term treatments decreased the number of apoptotic cells; they also increased the percentage of T cytotoxic cells; decreased the percentage of B cells and increased the corticosterone serum levels. The induction of functional tolerance was suggested for the highest dose of diazepam (10 mg/kg), but not for the smaller dose (1 mg/kg) used, at least for diazepam effects on corticosterone serum levels. Diazepam effects were discussed as being related to the number of TSPO sites present on immune cells and/or to the increased levels of serum corticosterone observed after the treatments used.

Immunomodulating properties of gamma-hydroxybutyrate (GHB), flunitrazepam and ethanol in 'club drugs' users

Despite the increasing concern about gamma-hydroxybutyrate (GHB) toxicity in users, no studies have addressed GHB and other club drugs effects on the immune system under controlled administration. Lymphocyte subsets and functional responsiveness of lymphocytes to mitogenic stimulation were measured in 10 healthy male recreational users of GHB who participated in five experimental sessions within the framework of a clinical trial. The study was randomized, double blind, double dummy and cross-over. Drug conditions were: a single oral dose of GHB (40 mg/kg or 60 mg/kg), ethanol (0.7 g/kg), flunitrazepam (1.25 mg) and placebo. Acute GHB produced a time-dependent immune impairment in the first 4 hours after drug administration associated with an increase in cortisol secretion. Although total leukocyte count remained unchanged, there was a significant decrease in the CD4 T/CD8 T-cell ratio, as well as in the percentage of mature T lymphocytes, probably because of a decrease in both the percentage and absolute number of T helper cells. A significant decrease was also observed in natural killer cells and in functional responsiveness of lymphocytes to mitogenic stimulation. Flunitrazepam administration did not produce any change in the immune system, while ethanol intake produced a decrease in B lymphocytes and in lymphocyte proliferative response to mitogens. These results provide the first evidence that GHB intake under a controlled environmental setting impairs the immunological status and confirms the alterations in the immune function caused by ethanol.

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.

Spinal translocator protein (TSPO) modulates pain behavior in rats with CFA-induced monoarthritis

Translocator protein 18 kDa (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is predominantly located in the mitochondrial outer membrane and plays an important role in steroidogenesis, immunomodulation, cell survival and proliferation. Previous studies have shown an increased expression of TSPO centrally in neuropathology, as well as in injured nerves. TSPO has also been implicated in modulation of nociception. In the present study, we examined the hypothesis that TSPO is involved in the initiation and maintenance of inflammatory pain using a rat model of Complete Freund's Adjuvant (CFA)-induced monoarthritis of the tibio-tarsal joint. Immunohistochemistry was performed using Iba-1 (microglia), NeuN (neurons), anti-Glial Fibrillary Acidic Protein, GFAP (astrocytes) and anti-PBR (TSPO) on Days 1, 7 and 14 after CFA-induced arthritis. Rats with CFA-induced monoarthritis showed mechanical allodynia and thermal hyperalgesia on the ipsilateral hindpaw, which correlated with the increased TSPO expression in ipsilateral laminae I-II on all experimental days. Iba-1 expression in the ipsilateral dorsal horn was also increased on Days 7 and 14. Moreover, TSPO was colocalized with Iba-1, GFAP and NeuN within the spinal cord dorsal horn. The TSPO agonist Ro5-4864, given intrathecally, dose-dependently retarded or prevented the development of mechanical allodynia and thermal hyperalgesia in rats with CFA-induced monoarthritis. These findings provide evidence that spinal TSPO is involved in the development and maintenance of inflammatory pain behaviors in rats. Thus, spinal TSPO may present a central target as a complementary therapy to reduce inflammatory pain.

Translocator protein 18 kDa is involved in the regulation of reactive gliosis

Translocator protein (18 kDa) (TSPO), previously known as peripheral-type benzodiazepine receptor, is a critical component of the mitochondrial permeability transition pore. Brain inflammation results in the induction of the expression of TSPO in glial cells and some TSPO ligands decrease reactive gliosis after brain injury. However, since some TSPO ligands are neuroprotective, their effects on reactive gliosis may be the consequence of a reduced neurodegeneration. To assess whether TSPO ligands can modulate reactive gliosis in absence of neuronal death, we have tested their effects on the inflammatory response induced in the hippocampus of male rats by the intracerebroventricular infusion of lipopolysaccharide (LPS). LPS treatment did not induce neuronal death, assessed by Fluoro jade-B staining, but increased the number of cells immunoreactive for vimentin and MHC-II, used as markers of reactive astrocytes and reactive microglia, respectively. Furthermore, LPS produced an increase in the number of proliferating microglia. The TSPO ligand PK11195 reduced the number of MHC-II immunoreactive cells and the proliferation of microglia in LPS treated rats. In contrast, another TSPO ligand, Ro5-4864, did not significantly affect the response of microglia to LPS. Neither PK11195 nor Ro5-4864 affected the LPS-mediated increase in the number of vimentin-immunoreactive astrocytes at the time point studied, although PK11195 reduced vimentin immunoreactivity. These findings identify TSPO as a potential target for controlling neural inflammation, showing that the TSPO ligand PK11195 may reduce microglia activation by a mechanism that is independent of the regulation of neuronal survival.

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.

Peripheral benzodiazepine receptor ligand PK11195 reduces microglial activation and neuronal death in quinolinic acid-injected rat striatum

The effects of the peripheral benzodiazepine receptor (PBR) ligand, PK11195, were investigated in the rat striatum following the administration of quinolinic acid (QUIN). Intrastriatal QUIN injection caused an increase of PBR expression in the lesioned striatum as demonstrated by immunohistochemical analysis. Double immunofluorescent staining indicated PBR was primarily expressed in ED1-immunoreactive microglia but not in GFAP-immunoreactive astrocytes or NeuN-immunoreactive neurons. PK11195 treatment significantly reduced the level of microglial activation and the expression of pro-inflammatory cytokines and iNOS in QUIN-injected striatum. Oxidative-mediated striatal QUIN damage, characterized by increased expression of markers for lipid peroxidation (4-HNE) and oxidative DNA damage (8-OHdG), was significantly diminished by PK11195 administration. Furthermore, intrastriatal injection of PK11195 with QUIN significantly reduced striatal lesions induced by the excitatory amino acid and diminished QUIN-mediated caspase-3 activation in striatal neurons. These results suggest that inflammatory responses from activated microglia are damaging to striatal neurons and pharmacological targeting of PBR in microglia may be an effective strategy in protecting neurons in neurological disorders such as Huntington's disease.

Human peripheral blood mononuclear cells express GABAA receptor subunits

The polymerase chain reaction was used to screen human peripheral blood mononuclear cells (PBMC) and Jurkat cells for the presence of GABAA receptor subunit mRNAs. Positive signals were detected for the alpha1, alpha3, beta2, beta3, delta and epsilon subunit mRNAs in both cell populations, with the Jurkat cells giving a positive signal for some additional species. Real-time PCR was used to confirm that PBMC, lymphocytes and monocytes contained significant levels of the alpha1 subunit mRNA and that PBMC and lymphocytes contained low levels of beta2 mRNA. The alpha1 subunit was detected in PBMC and fractionated T-cell populations, as well as Jurkat and HL-60 cell lines, by Western blotting and immunofluorescence using a specific antibody. The application of 1mM GABA reduced the specific increase in intracellular PBMC Ca2+ levels produced by addition of 1 nM fMLP: this effect was mimicked by muscimol, but not glycine, and was blocked by bicuculline. The inhibitory effect of GABA was limited to a subset of PBMC. We conclude that cells within the human PBMC population, including lymphocytes, express functional GABAA receptors and these receptors may modulate immune responses.

Cytokine levels and phagocytic activity in patients with Alzheimer's disease

BACKGROUND

Clinical observations indicate that patients with Alzheimer's disease show a greater susceptibility to infections. One possible explanation is that this predisposition is due to alterations in their immune system.

OBJECTIVE

To investigate this assumption, pro- and anti-inflammatory cytokines, as well as the phagocytic activity and superoxide anion generation was examined in aged individuals with and without Alzheimer's disease.

METHODS

The production of IL-1beta, IL-2, IL-6, TNFalpha and IL-10 by peripheral blood mononuclear cells from 12 patients with Alzheimer's disease was compared with that of 12 age-matched individuals without any signs of dementia and 12 middle-aged healthy volunteers who served as an additional control. The engulfing capacity of the phagocytic cells was detected by counting cells containing latex beads and the number of particles internalized by each individual cell.

RESULTS

The secretion of IL-2 was markedly low in the demented patients, compared with both elderly and middle-aged subjects. IL-1beta and TNFalpha production was similar in the individuals of the 3 groups. The production of IL-6 and IL-10 was significantly lower when compared to that of the middle-aged, but did not differ between the elderly patients with and without dementia. The phagocytic function of both polymorphonuclear cells and monocytes was decreased in individuals of the elderly groups with a low number of engulfed latex particles by each individual polymorphonuclear cell. The production of superoxide anions was increased only by monocytes from the elderly groups.

CONCLUSIONS

The results suggest that although the impaired immune function in patients with Alzheimer's disease is related to the aging process, the significant low IL-2 production in these patients may play a role in their increased susceptibility to infections.

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.

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.

Potential role of peripheral benzodiazepine receptors in inflammatory responses

This study investigates the anti-inflammatory effects of 1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide and 7-chloro-5-(4-chlorophenyl)-1, 3-dihydro-1-methyl-2-H-1,4-benzodiazepin-2-one in paw oedema induced by carrageenan in mice. Pretreatment (24 h) with both ligands inhibited oedema formation in at different doses (0.00001-10 mg/kg, i.p.) with range of inhibition of 25% to 70%, in animals with or without adrenal glands. These results demonstrate, for the first time, an in vivo anti-inflammatory property of peripheral benzodiazepine receptor ligands.

The peripheral benzodiazepine receptor ligand PK 11195 inhibits arthritis in the MRL-lpr mouse model

OBJECTIVE

Mice of the MRL-lpr strain develop a severe autoimmune arthritic condition when primed with complete Freund's adjuvant. The pathology is similar to that seen in human rheumatoid arthritis. We investigated whether PK 11195, a powerful ligand for peripheral benzodiazepine receptors, would have preventative or therapeutic effects in this model.

METHODS

MRL-lpr mice were primed with complete Freund's adjuvant at 13-14 weeks of age. Daily PK 11195 injections were started on the same day as priming to test for preventative effects. Daily PK 11195 injections were started 10 days after priming to test therapeutic effects.

RESULTS

PK 11195 showed both preventative and therapeutic effects. At 1 mg/kg/day, it inhibited disease onset. At 3 mg/kg/day, it inhibited established disease progression.

CONCLUSION

The evidence suggests that PK 11195 may be the prototype of a new class of anti-inflammatory agents.

Decreased platelet peripheral-type benzodiazepine receptors in adolescent inpatients with repeated suicide attempts

BACKGROUND

Peripheral-type benzodiazepine receptors (PBR) are responsible for mitochondrial cholesterol uptake, the rate limiting step of steroidiogenesis. They have been shown to be increased after acute stress, and decreased during exposure to chronic stressful conditions, and in patients with generalized anxiety disorder and post-traumatic stress disorder. In view of the proven connection between adolescent suicidal behavior and stress, we hypothesized that PBR may be decreased in the suicidal adolescent population.

METHODS

We measured [3H] PK 11195 binding to platelet membrane in nine adolescent (age 13-20 years) inpatients with a history of at least three suicidal attempts and ten age-matched psychiatric inpatients with no history of suicide attempts. Suicidality was assessed with the Suicide Risk Scale (SRS), and symptom severity with the Beck Depression Inventory, State-Trait Anxiety Inventory (STAI), Overt Aggression Scale (OAS), and Impulsivity Scale (IS).

RESULTS

Suicide Risk Scale scores were significantly higher in the suicidal group. The suicidal group showed a significant decrease in platelet PBR density (-35%) compared to the controls (p < 0.005).

CONCLUSIONS

Our results of PBR depletion in adolescent suicide are in accordance with the findings in patients with generalized anxiety disorder and posttraumatic stress disorder and lend further support to the role of PBR in human response to chronic stress in adolescent suicide.

Peripheral type benzodiazepine receptor in T lymphocyte rich preparation

Some types of mood disorders and drugs are suggested to affect peripheral type benzodiazepine receptors (PBR), but their mechanisms are unclear. The isolation of pure lymphocytes is requisite for the investigation of the function of PBR on lymphocytes, since platelets and monocytes also have many PBR. The objective of this study was to establish a method of binding assay for PBR using pure T lymphocytes. Mononuclear cells and T lymphocytes were prepared by using a density gradient material and magnetic beads, respectively. The cells were analyzed using flow cytometry and a counting chamber. Binding studies were performed using T lymphocytes from 10 normal volunteers. The T lymphocytes were incubated with [3H]PK11195, harvested on glass fiber filters, and counted with a plate scintillation counter. The binding data were analyzed by the Scatchard method. With the magnetic bead technique, pure T cells were selected that contained only 1.5% monocytes and platelet/cell ratio of 1.4. The Scatchard plot of the data indicated that only one type of specific binding site was involved in the binding. The dissociation constant (Kd) was 3.8+/-1.3nM (mean+/-SD), and the Bmax was 379+/-124 fmol//10(6) cells (mean+/-SD). The density gradient- magnetic beads technique can be used as an appropriate method of preparation of T cells for PBR binding assay.

The urinary ratio of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid in surgical patients with chronic alcohol misuse

The urinary ratio of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid was reported to be elevated for a period of up to 22 h following acute alcohol ingestion. Therefore, the ratio could detect continuous alcohol consumption, in what was considered to be a high-risk surgical group, on the evening prior to surgery. The aim of this study was to determine the preoperative ratio of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid in patients with continuous preoperative alcohol misuse. Forty-two patients participated in this institutionally approved study, once their written informed consent had been obtained. Chronic alcoholics were defined by meeting the criteria of the Diagnostic and Statistical Manual of Mental Disorders criteria and an ethanol consumption > or =60 g/day. The urine samples were taken preoperatively and determined by means of gas chromatography-mass spectrometry and high performance liquid chromatography. The urinary ratio of 5-hydroxytryptophol to 5-hydroxyindole-3-acetic acid was significantly increased in chronic alcoholics. The ICU stay of these patients was significantly prolonged due to an increased incidence of pneumonia and sepsis. Five chronic alcoholics died, whereas no deaths occurred in the nonalcoholic group (p = 0.05). As the measurement of the urinary ratio of 5-hydroxy-tryptophol to 5-hydroxyindole-3-acetic acid could detect alcohol consumption immediately prior to operation, this marker could assist the carbohydrate-deficient transferrin in screening for patients with high-level dependency; these patients were considered to be at a high risk of developing intercurrent complications.

Benzodiazepines, glia, and HIV-1 neuropathogenesis

Although the precise mechanisms whereby HIV-1 infection induces neurodegeneration have yet to be determined, a great deal of evidence has incriminated glial cells and the production of proinflammatory mediators in this pathologic process. For this reason, ideal therapeutic agents for the treatment of AIDS dementia would attenuate HIV-1 neuropathogenesis through both direct inhibition of viral expression and suppression of brain cell-produced immune mediators. Benzodiazepines (BDZs), such as Valium, are extensively prescribed drugs for anxiety disorders, which readily cross the blood-brain barrier and have demonstrated immunomodulatory properties. BDZs bind to primary human microglial cells, the principal site of HIV-1 replication in the brain, and inhibit lipopolysaccharide (LPS) induced tumour necrosis factor (TNF-alpha) production by these cells in a concentration-dependent manner. Treatment of HIV-1-infected primary human microglial, as well as mixed glial/neuronal, cell cultures with BDZs inhibits the expression of HIV-1 p24 antigen. BDZ-induced inhibition of HIV-1 expression in chronically infected promonocytic (U1) cells has been found to be associated with decreased activation of the nuclear transcription factor kappa B (NF-kappa B). Because HIV-1 expression is critically dependent on the cellular transcription machinery, inhibition of the activation of transcription factors, which participate in both HIV-1 expression and the production of neurotoxic immune mediators, by BDZ analogs may provide new therapeutic options for AIDS dementia.

Diazepam-mediated inhibition of human immunodeficiency virus type 1 expression in human brain cells

Treatment of acutely infected human brain cell and enriched microglial cell cultures with diazepam inhibited human immunodeficiency virus type 1 (HIV-1) p24 antigen expression. Similarly, diazepam suppressed HIV-1 expression in chronically infected promonocytic (U1) cells and acutely infected monocyte-derived macrophages, and this antiviral activity was associated with decreased activation of nuclear factor kappa B.

Peripheral-type benzodiazepine receptor ligands and serum steroid hormones

The peripheral-type benzodiazepine receptors (PBR) are involved in various cellular functions, including steroidogenesis. The impact of these receptor ligands has been demonstrated mainly in steroidogenic cells. The aim of the present study was to assess in intact female rats the effect of chronic (21 days) administration of the PBR ligands PK 11195 (15 mg/kg) and Ro 5-4864 (5 mg/kg), the mixed ligand diazepam (5 mg/kg), and the central benzodiazepine receptor ligand clonazepam (1 mg/kg) on PBR binding characteristics in steroidogenic (ovary and adrenal) and non-steroidogenic (uterus and kidney) organs, as well as on serum hormonal steroids (estradiol, progesterone, and corticosterone). Selective and mixed PBR ligands up-regulated PBR density in the two steroidogenic organs, while Ro 5-4864 also induced elevation of the receptor density in the non-steroidogenic organs. In contrast to Ro 5-4864, PK 11195 treatment down-regulated renal PBR. Clonazepam elevated adrenal PBR. On the serum hormonal level, Ro 5-4864 suppressed estradiol secretion. The other ligands did not affect hormonal steroid levels. It appears that in female rats, at least at these doses and dosing schedules, there is no correlation between the impact of chronic in vivo exposure to these agents on PBR density and ovarian and adrenal hormone levels.

Benzodiazepines, anxiety and immunity

Experimental and clinical studies suggest that the central and peripheral benzodiazepine (BDZ) receptors together with their ligands form the molecular basis of a novel regulatory network that contributes to the effects of anxiety on immune status. The peripheral-type receptors located on phagocytes and glial cells appear to play a key role in mediating the effects of endogenous and exogenous BDZs both on the defence mechanisms that protect the host against pathogens and on inflammatory reactions that take place within the periphery and the brain in response to injury. In addition, the central-type receptor, which forms part of the gamma-aminobutyric acidA receptor complex, may contribute to the regulation of T-cell function by modulating the activity of the hypothalamo-pituitary-adrenocortical axis or the sympathoadrenal system or both, which, in turn, exert a significant effect on immune function. Thus, anxiogenic BDZs in general suppress the immune response, whereas anxiolytic BDZs may protect the individual from stress-induced immunosuppression.

Platelet and lymphocyte benzodiazepine binding in patients with Alzheimer's disease

Peripheral blood cells, such as platelets or lymphocytes, have been studied in the investigation of systemic derangements and central nervous system biochemical changes occurring in several neuropsychiatric disorders. In the present work, assaying platelet and lymphocyte peripheral-type benzodiazepine binding in patients with Alzheimer's disease (AD) and healthy controls, we found a significantly reduced number of cell receptors in patients' platelets and lymphocytes. These results are discussed with reference to central nervous system biochemical abnormalities in AD. Moreover, the lymphocyte binding data may represent an impairment of the immune response in AD, since lymphocyte surface peripheral-type benzodiazepine receptors seem to be related to immune function.

Peripheral-type benzodiazepine receptor ligands modulate human natural killer cell activity

Following our earlier work, we evaluated the in vitro effect of ligands active at the peripheral-type benzodiazepine receptors on human natural killer cell activity. Peripheral blood mononuclear cells were incubated with benzodiazepine receptor ligands. After 4 h we observed a nonspecific inhibition of natural killer cell activity induced by both peripheral (Ro5-4864 and PK 11195) and central (clonazepam) benzodiazepine receptor ligands; after 24 h, the suppressive activity was specific to peripheral and mixed (diazepam) ligands, and the central-type ligand had no effect. This significant, specific suppression of NK cell activity was completely reversed by the addition of human recombinant interleukin-2 or human leukocyte interferon. Our research provides additional information on the immunomodulatory effects of peripheral-type benzodiazepine ligands. Further studies are needed to clarify the underlying mechanism of natural killer cell inhibition and to determine the clinical implications of these findings.

T lymphocyte benzodiazepine binding is reduced in demented patients

Blood cells, especially platelets and lymphocytes, are used in neuropsychiatric research as tools for investigating systemic derangements in neuropsychiatric disorders, and as peripheral models for studying central nervous system biochemistry. In the present work, we determined T lymphocyte peripheral-type benzodiazepine binding: a significant reduction of Bmax values was observed in demented patients as compared with healthy controls, whereas Kd values were similar in the two subjects' groups. A significant negative correlation was found between Bmax values and illness severity. These data, which seem to be related to an impairment of immune response and cell energy metabolism in demented patients, may represent a state-dependent marker in monitoring disease course and treatment efficacy.

T-lymphocyte peripheral-type benzodiazepine binding in parkinsonian patients

Human peripheral blood cells, especially lymphocytes and platelets, are being studied increasingly in neuropsychiatric research both as tools for investigating systemic disturbances in neuropsychiatric disorders, and as peripheral models for getting information on central nervous system biochemistry. In this study, we determined T lymphocyte peripheral-type benzodiazepine binding in parkinsonians and controls: significantly reduced B(max) values were found in patients compared with healthy controls, whereas K(d) values were similar. These data argue for an immune response disturbance and a cell energy metabolism impairment in parkinsonian patients, since cell surface peripheral-type benzodiazepine receptors are related with the immune function, and mitochondrial binding sites with energy metabolic pathways.

Modifications of diazepam binding inhibitor and peripheral benzodiazepine receptors in the lymphocytes of epileptic patients

Recent experimental evidence has suggested that peripheral benzodiazepine receptors (PBR) may play a role in epilepsy and antiepileptic drug action. Since PBR are also present in circulating lymphocytes, and may interact with anticonvulsant drugs, this study was designed to look for possible modifications of these receptors and their endogenous ligand diazepam binding inhibitor (DBI) in the lymphocytes of epileptic patients treated with various drugs. PBR levels were 50% to 80% higher in patients treated with carbamazepine, phenobarbital and valproic acid than in controls and untreated epileptics. DBI levels were significantly increased in the lymphocytes of untreated patients, and showed only a slight further increase after anticonvulsant therapy. The possibility that PBR and DBI modifications in the lymphocytes of epileptic patients may be linked to the immunological alterations reported in these patients and/or may represent possible markers of neurochemical modifications in the central nervous system is discussed.

Positive and negative immunomodulation by opioid peptides

The data that follow review part of the existing evidence concerning the neuroimmune functions mediated by opioid peptides, with particular regard to dual immunomodulatory effects. Limited references to substances other than opioid peptides are included, mainly to emphasize the possible similarities in the mediation of neuroimmune interactions by different informational substances, while the interactions directed from the immune to the nervous system have deliberately been omitted.

Environmentally induced changes in peripheral benzodiazepine receptors are stressor and tissue specific

The stress-induced changes in peripheral benzodiazepine receptors (PBR) can be observed in a number of different tissues, depending upon the nature and chronicity of the aversive experience. In addition, virtually all stress procedures that cause rapid changes in PBR simultaneously increase the physical activity or metabolic rate of the subjects. The present study analyzed the contributions of rapid alterations in activity or metabolic rate with and without aversive stimulation and their subsequent impact on PBR. Mechanically induced increases in activity by forced running stress results in a significant reduction in [3H]Ro 5-4864 binding to PBR in olfactory bulb, opposite to the PBR changes in this tissue following forced cold-water swim stress. Pharmacological induction of increased locomotor activity as well as metabolic rate by d-amphetamine causes a significant increase in cardiac PBR binding, again, opposite to the response typically observed following inescapable shock stress. Finally, administration of the anxiogenic beta-carboline, FG-7142, causes increases in both hippocampus and adrenal gland PBR binding reminiscent of acute noise stress exposure. These experiments demonstrate that increased locomotor activity or metabolic rate alone is not a necessary and sufficient condition for previous stress-induced changes in PBR. Conversely, increased metabolic rate coupled with an aversive stimulus appears to be an important factor for inducing stress-like changes in PBR. This data, coupled with previous reports, suggests that rapid alterations in these sites are stressor and tissue dependent. Finally, we propose that the PBR may be involved in many aspects of the stress response including: a) a blowarning system in adrenal gland, b) participation in stress-induced hypertension via renal PBR, and c) a modulator of stress-induced immunosuppression and subsequent recovery of function or recuperation by actions on immune cells.

Effect of anticonvulsant drugs on peripheral benzodiazepine receptors of human lymphocytes

Anticonvulsant drugs, such as carbamazepine, may exert some of their effects through peripheral benzodiazepine receptors (PBR), which are present in glial cells and regulate the synthesis of neurosteroids. PBR have also been demonstrated in human lymphocytes, where they might be used as peripheral markers of anticonvulsant drug effects. In the present paper we investigated the interaction of various antiepileptic drugs with PBR of human lymphocytes and evaluated possible effects of acute and chronic treatment with these drugs. At normal therapeutic concentrations, diazepam, carbamazepine and phenobarbital occupy respectively 70, 30 and 10% of PBR sites in human lymphocytes. Although no change of receptor density or affinity was observed after acute in vitro treatment, in epileptic patients chronically treated with carbamazepine, phenobarbital and valproic acid, PBR Bmax was increased with respect to controls and untreated epileptics. Since PBR of human lymphocytes may be affected by anticonvulsant drug treatment, we suggest that they might be involved in the immunological alterations reported in these patients and might be used as peripheral markers of drug effects on the central nervous system.

Antidepressants reverse the olfactory bulbectomy-induced decreases in splenic peripheral-type benzodiazepine receptors in rats

The present study investigated the effects of 21-day administration of clorgyline (1 mg/kg/day), desipramine (10 mg/kg/day) or paroxetine (10 mg/kg/day) on peripheral-type benzodiazepine receptors in rat peripheral tissues following bilateral olfactory bulbectomy. Thymus and spleen weights decreased as a result of bulbectomy. Subsequent antidepressant drug administration had no further effects on the weights of thymus glands but increased those of spleens. In thymus glands, higher densities of peripheral-type benzodiazepine receptors were observed in medulla than in cortex; no significant variations were observed following bulbectomy or antidepressant drug administration. In spleen, higher densities were observed in white pulp than in red pulp. The bulbectomy-induced decreases in binding densities observed in both regions were reversed following administration of antidepressants. Adrenal peripheral-type benzodiazepine receptors were not altered by bulbectomy or subsequent treatment with clorgyline or desipramine while paroxetine upregulated these receptors. No changes in kidney peripheral-type benzodiazepine receptors were observed. The present study confirms that cell lines of the rat immune system possess high densities of peripheral-type benzodiazepine receptor binding sites and further support the contention that, following olfactory bulbectomy, rats may present an antidepressant-reversible immunitary dysfunction.

Effect of peripheral benzodiazepine receptor ligands on lipopolysaccharide-induced tumor necrosis factor activity in thioglycolate-treated mice

To investigate the effect of peripheral and central benzodiazepine receptor ligands on lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) activity in mouse macrophages, three types of ligands, 4'-chlorodiazepam (pure peripheral), midazolam (mixed), and clonazepam (pure central), were compared. Midazolam and 4'-chlorodiazepam significantly suppressed LPS (1-microgram/ml)-induced TNF activity in thioglycolate-elicited mouse macrophages. In every concentration examined (0.001 to 100 microM), 4'-chlorodiazepam was the most effective agent, clonazepam was the least effective agent, and midazolam had an effect intermediate between those of the other two ligands. The peripheral benzodiazepine receptor ligands had a dose-dependent suppressive effect, and the 50% inhibitory concentrations were 0.01 microM for 4'-chlorodiazepam and 5 microM for midazolam. Concomitant use of PK 11195 (10 microM), an antagonist of the peripheral benzodiazepine receptor, reversed this suppressive effect with 4'-chlorodiazepam (10 microM) or midazolam (10 microM). PK 11195 showed this antagonistic effect in a dose-dependent manner. Intravenous 4'-chlorodiazepam (5 mg/kg of body weight) significantly suppressed LPS (100-micrograms)-induced TNF activity of sera (2 h postchallenge with LPS) from thioglycolate-treated mice. The present findings suggest that the peripheral benzodiazepine receptor plays an important role in modulating LPS-induced TNF activity in mouse macrophages.

Peripheral-type benzodiazepine receptors on human blood mononuclear cells are not regulated by ovarian steroids

Peripheral-type benzodiazepine receptors (pBZr) have been shown to be sensitive to hormonal perturbations, including changes in ovarian steroids. This study examines whether estradiol and progesterone modulate pBZr binding in membranes of human blood mononuclear cells, as measured by binding of both 3H-PK 11195 and 3H-Ro 5-4864. Our findings were negative. There was no steroidal modulation of pBZr binding to these membrane preparations in vivo in normal women studied at different sex-steroid phases of the menstrual cycle, or during 8-30 weeks of pregnancy. There was also no effect of hormones on the binding sites in cultures of mononuclear cells treated with estradiol or progesterone (up to 10(-5) M) over a period between 2 and 72 h. Further, we performed in vitro competition experiments, which showed that both steroids are not active at the pBZr. Our data suggest that pBZr located in human blood mononuclear cells are insensitive to the physiological variations of circulating female hormones.

Peripheral benzodiazepine receptor modulation with phagocyte differentiation

Peripheral benzodiazepine receptor (PBR) was found to be less expressed in the immature phagocytic HL-60 and U-937 cell lines than in the more mature monocytic THP-1 cell line. Cell differentiation by several agents induced a strong enhancement of PBR density on these three phagocytic cell lines but not on the lymphocytic CEM cell line. Detailed analysis of phorbol 12-myristate 13-acetate-treated THP-1 cells showed an increased PBR expression and the rise came along with an increase of CD11a and CD11b antigens and a secretion of macrophagic cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta and IL-8. Quantitation of mRNA using polymerase chain reaction (PCR)-based technique showed that overexpression of PBR did not parallel mRNA expression, indicating a gene-independent regulation. These results suggest that PBR predominance on phagocytic cells could be related to maturation process.

Peripheral-type benzodiazepine receptors and diazepam binding inhibitor-like immunoreactivity distribution in human peripheral blood mononuclear cells

Peripheral-type benzodiazepine receptors (pBZr) in human lymphocytes have been detected only in mixtures of peripheral blood mononuclear cells (PBMC). The present investigation was designed to describe precisely the location of pBZr in the various sets and subsets of PBMC, purified using monoclonal antibodies to specific PBMC surface markers. Site densities and affinities of pBZr were measured in the intact cells by conventional binding, using 3H-PK 11195 as a ligand. Moreover, we used a specific radioimmunoassay to identify in these cells the presence of the polypeptide diazepam binding inhibitor (DBI), a putative endogenous ligand for various benzodiazepine receptors including the peripheral type. Two major findings are derived from these studies: first, the coexistence of pBZr and DBI, or closely related immunoreactive material, in all major lymphocyte sets and subsets, as well as in monocytes. And second, the significant correlation (r = 0.87, p < 0.001) observed between the density of pBZr in a given cell type and its abundance of DBI like-immunoreactivity (DBI-LI). For both pBZr and DBI-LI content the cell distribution was monocytes > B cells and large granular lymphocytes > T cells (CD3+ set or CD4+ and CD8+ subsets) (ANOVA: pBZr: F = 114.11, p < 0.001; DBI-LI: F = 20.79, p < 0.001). The results are discussed in terms of the possibility that DBI and pBZr might share a relevant interaction in immunocompetent elements, thereby contributing to a new route of connection between the immune and the nervous systems.

Benzodiazepine receptors and diazepam binding inhibitor: a possible link between stress, anxiety and the immune system

This review summarizes the evidence available on the involvement in stress of different classes of benzodiazepine receptors and their putative endogenous ligand, diazepam binding inhibitor (DBI), with particular reference to their role in modifications of the immune response. The presented data from in vitro, experimental, and clinical studies suggest that benzodiazepine receptors and DBI play a major role in regulating steroid production in both the adrenals and central nervous system, and may be involved in the activation of the hypothalamic-pituitary-adrenal axis in stress response.

An analysis of peripheral type benzodiazepine receptors on blood mononuclear cells during high dose steroid treatment of multiple sclerosis

We report here a study of peripheral type benzodiazepine receptors (pBZr) in mononuclear cells (MNC) from blood of patients with multiple sclerosis (MS) during periods of stable and active disease and from normal controls. Most active MS patients were retested in a longitudinal study, both during a treatment with high dose steroids and while medication free. Active MS produces a significant decrease of receptor density compared with the controls whereas remission of the disease shows no effect. Four weeks of steroid treatment restore binding density to normal levels, and two weeks of drug withdrawal result in a small, but significant increase in number of the binding sites compared with the control value. We suggest that the number of pBZr in blood MNC might change during the clinical course and steroid therapy of MS.