Peripheral Benzodiazepine Receptor mRNA Research Articles

Electroacupuncture improves insomnia by down-regulating peripheral benzodiazepine receptor expression in hippocampus, and up-regulating 5-HT, 5-HIAA, TNF-α and IL-1β contents in hypothalamus in insomnia rats

To observe the therapeutic effect of electroacupuncture (EA) at five Back-Shu points on sleep, hippocampal peripheral benzodiazepine receptor (PBR) expression and hypothalamic 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β contents in insomnia rats, so as to explore its mechanisms underlying improvement of insomnia. Forty male SD rats were randomly divided into control, model, EA and medication (Diazepam) groups (n=10 rats in each group). The insomnia model was established by intraperitoneal injection (i.p.) of para-Chlorophenylalanine (PCPA, 300 mg/kg) once daily for 2 days. EA (60 Hz, 1 mA) was applied to bilateral five Back-Shu points, i.e., Feishu (BL13), Xinshu (BL15), Ganshu (BL18), Pishu (BL20) and Shenshu (BL23) for 10 min, once daily for 6 days. Rats of the medication group were treated by gavage of Diazepam (0.92 mg/kg) once daily for 6 days. The sleep duration was recorded after i.p. of Pentobarbital Sodium (45 mg/kg). Histopathological changes of the hippocampus were displayed by H.E. staining. The contents of 5-HT, 5-HIAA, TNF-α and IL-1β in the hypothalamus were assessed by using ELISA. The expression levels of PBR mRNA and protein in the hippocampus were detected by quantitative real-time PCR, immunohistochemistry and Western blot, separately. Following modeling, the sleep duration was considerably shortened in rats of the model group relevant to the control group (P<0.05). After the treatment, the sleep duration was significantly increased in both EA and medication groups relevant to the model group (P<0.05). After modeling, the hippocampal neurons were obviously decreased in number, and disordered in the arrangement, the levels of hypothalamic 5-HT, 5-HIAA, TNF-α, and IL-1β were significantly down-regulated (P<0.05), and the expression of PBR mRNA and protein in hippocampus was obviously increased relevant to the control group (P<0.05). Following the treatment, the hippocampal neurons were increased in number and arranged regularly, and the contents of hypothalamic 5-HT, 5-HIAA, TNF-α, and IL-1β were considerably increased (P<0.05), and the expression of PBR mRNA and protein in hippocampus was significantly decreased in both EA and medication groups relevant to the model group (P<0.05). The therapeutic effect of EA was comparable to that of medication in increasing sleep duration, body weight, 5-HT and 5-HIAA contents (P>0.05), and significantly superior to that of the medication in increasing TNF-α and IL-1β levels (P<0.05), and considerably superior to that of medication in down-regulating PBR mRNA and protein expression (P<0.05). EA at five Back-Shu-points of the five Zang-organs can significantly improve the sleep in insomnia rats, which is closely associated with its effects in reducing the expression of PBR in hippocampus and up-regulating the levels of 5-HT, 5-HIAA, TNF-α and IL-1β in hypothalamus.

Permethrin exposure during puberty has the potential to enantioselectively induce reproductive toxicity in mice

Permethrin (PM), as a chiral pesticide, has two asymmetric centers, resulting in two pairs of enantiomers. In China, the commercial formulation of PM contains four enantiomers. The enantiomer-specific activity for endocrine disruption in mice remains unclear. In the present study, the four individual PM enantiomers were separated by preparative HPLC. Then, three week-old male ICR mice (after maternal ablactation) were orally administered (+)-cis, (−)-cis, (+)-trans, and (−)-trans-PM separately daily for 3weeks at doses of 0, 25, 50 and 100mg/kg/day, respectively. The results showed that 100mg/kg of (+)-cis, (−)-cis and (−)-trans-PM treatments resulted in serious testicular histopathological damage, decreases in testis weight and serum testosterone (T) concentrations. Moreover, the transcription status of some key genes involved in cholesterol synthesis and transport as well as T synthesis in the testes were also influenced selectively by PM enantiomers, especially by the (+)-cis-PM. Additionally, peripheral benzodiazepine receptor (PBR) and 17β-hydroxysteroid dehydrogenase (17β-HSD) mRNA levels decreased significantly in the (+)-cis-PM group regardless of the administrated doses, while steroidogenic acute regulatory protein (StAR) levels were significantly down-regulated by (+)-cis and (−)-trans-PM. Moreover, significant differences were mainly found in HMG-CoA reductase, PBR, StAR and 17β-HSD mRNA levels between different enantiomers. Combined with the effects on physiology, histopathology and the expression of genes related to T synthesis, (+)-cis-PM showed the greatest endocrine disruption activities, (−)-cis and (−)-trans-PM were moderate, while (+)-trans-PM exhibited the lowest. These results suggested significant PM enantioselectivity in the reproductive toxicity of mice during puberty exposure.

Upregulation of PBR mRNA expression in human neuroblastoma cells by flavonoids

To investigate the putative mediation of peripheral benzodiazepine receptor (PBR) in the cytotoxicity of flavonoids, in this study, modulatory effects of several flavonoids on the lipid peroxide (LPO) production and PBR mRNA expression of human neuroblastoma cells were observed. Elevated levels of peroxidated products in cancer cells may activate pro-apoptotic and anti-proliferative signaling pathways. Treatment of 10(-6) M 4'-chlorodiazepam and PK 11195 ligands of the PBR for 6 days enhanced the generation of LPO of the human neuroblastoma cells. Several flavonoids, well-known cytotoxic substances, potentiated the enhancement of LPO production by PBR ligands. Treatment of 10(-6) M flavonoids for 6 days elevated the expression of PBR mRNA in cells. These findings indicate that the potential of flavonoids to induce apoptosis in cancer cells is strongly associated with their PBR-inducing properties, thereby providing a new mechanism by which polyphenolic compounds may exert their cancer-preventive and anti-neoplastic effects.

Evidence in favour of a role for peripheral-type benzodiazepine receptor ligands in amplification of neuronal apoptosis

The mitochondrial peripheral benzodiazepine receptor (PBR) is involved in a functional structure designated as the mitochondrial permeability transition (MPT) pore, which controls apoptosis. PBR expression in nervous system has been reported in glial and immune cells. We now show expression of both PBR mRNA and protein, and the appearance of binding of a synthetic ligand fluo-FGIN-1-27 in mitochondria of rat cerebellar granule cells (CGCs). Additionally, the effect of PBR ligands on colchicine-induced apoptosis was investigated. Colchicine-induced neurotoxicity in CGCs was measured at 24 h. We show that, in vitro, 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 diazepam (25- 50 microM) enhanced apoptosis induced by colchicine, as demonstrated by viability experiments, flow cytometry and nuclear chromatin condensation. Enhancement of colchicine-induced apoptosis was characterized by an increase in mitochondrial release of cytochrome c and AIF proteins and an enhanced activation of caspase-3, suggesting mitochondrion dependent mechanism that is involved in apoptotic process. Our results indicate that exposure of neural cells to PBR ligands generates an amplification of apoptotic process induced by colchicine and that the MPT pore may be involved in this process.

Upregulation of mitochondrial peripheral benzodiazepine receptor expression by cytokine‐induced damage of human pancreatic islets

Cytokines produced by immune system cells infiltrating pancreatic islets are candidate mediators of islet beta-cell destruction in autoimmune insulin-dependent diabetes mellitus. After 72 h exposure of human pancreatic islets to a cytotoxic cytokine combination of interleukin 1 beta (50 U/ml), tumor necrosis factor alpha (1,000 U/ml), and interferon gamma (1,000 U/ml), an increase of cell death vs. control islets was demonstrated by TUNEL and cell death detection ELISA method. Islet death was associated with apoptosis and mitochondrial swelling as evidenced by electron microscopy. This effect was correlated with a marked decrease of Bcl-2 mRNA expression (without any major change of Bax mRNA) and a marked increase of inducible nitric oxide synthase mRNA. Since peripheral benzodiazepine receptors constitute the aspecific mitochondrial permeability transition pore, and that it has been suggested to be involved in cytokine-induced cell death, we evaluated the effects of the cytotoxic cytokines on PBR density and mRNA expression. We demonstrated that cytokine treatment of human islets induced an increase of maximum density of (3)H1-(2-chlorophenyl-N-methyl-1-methylpropyl)-3- isoquinolinecarboxamide binding sites, (5,110+/-193 vs. 3,421+/-336 fmol/mg proteins, P<0.05) with no significant change in the affinity constant value (9.45+/-0.869 vs. 8.7+/-1.159 nM). Moreover, an increase of the expression of peripheral benzodiazepine receptor mRNA was observed, suggesting an increased transcription from the coding gene. These results suggest a possible role of peripheral benzodiazepine receptors in the organism response to tissue damage associated with inflammatory mediator production.

Stress, anxiety and peripheral benzodiazepine receptor mRNA levels in human lymphocytes

Peripheral benzodiazepine receptor (PBR) mRNA levels were measured in lymphocytes obtained from a cohort of university students and clinically diagnosed anxious patients. The average level of PBR mRNA was decreased in anxious patients compared to a control group. This data confirms previously published results, but it also indicates that PBR mRNA levels cannot be used as a sole diagnostic measure of anxiety because the range of the individual PBR mRNA levels of the anxious group overlapped the range of the PBR mRNA levels of the control group. PBR mRNA levels in students following academic examinations were increased in some individuals and decreased in others. In the same cohort of students individual levels of cortisol and prolactin were predominantly increased and decreased respectively. There was no correlation between the individual changes in the hormone levels or PBR mRNA, which suggests that each of these parameters is affected by different environmental and physiological factors. Lymphocyte PBR mRNA measurement is a useful additional methodology for studying human stress responses however, its use in clinical studies would require the elucidation of PBR's physiological role.

Lymphocyte peripheral benzodiazepine receptor mRNA decreases in obsessive-compulsive disorder

The relative content of peripheral benzodiazepine receptor (pBR) mRNA was examined by reverse transcriptase-polymerase chain reaction in lymphocytes of obsessive-compulsive disorder (OCD) patients, according to their clinical course of illness. pBR mRNA significantly decreased only in chronic OCD patients ( n=8) as compared to controls ( n=10), whereas no significant changes were observed in episodic OCD patients ( n=7). We suggest that modulation of pBR gene expression might delineate a clinical heterogeneity in OCD.

Expression of adrenocortical steroidogenic acute regulatory (StAR) protein is influenced by chromaffin cells

Cell–cell interactions are crucial role for the proper functioning of endocrine glands. We recently demonstrated that interactions of chromaffin and cortical cells are important for adrenocortical steroidogenesis. However, the molecular mechanisms have not been elucidated and it is unclear if this involves acute and/or chronic processes. By Northern analysis and the quantitative technique of TaqMan PCR we investigated whether chromaffin cells influence the regulation of StAR and the peripheral benzodiazepine receptor (PBR), both required for the rate-limiting step, the delivery of cholesterol to the inner mitochondrial membrane. StAR mRNA levels in bovine adrenocortical cells were increased by incubation with chromaffin cell-conditioned medium (CCM). Short-term treatment for 4 h resulted in a greater stimulation (229±29% of basal, mean±SEM) than did longer incubation times of 8 h and 5 days (159±13 and 177±24%). Neither short nor a long-term treatment affected PBR expression. Consistently, the major secretion of chromaffin cells, epinephrine dose-dependently stimulated StAR expression with no effect on PBR mRNA. In conclusion, adrenomedullary secretory products are not necessary for the maintenance of PBR expression but facilitate steroid biosynthesis by increasing StAR mRNA expression and therefore can account for an ACTH-independent regulation of the rate-limiting step in steroidogenesis.

Diazepam-binding inhibitor/acyl-CoA-binding protein mRNA and peripheral benzodiazepine receptor mRNA in endocrine and immune tissues after prenatal diazepam exposure of male and female rats.

Peripheral benzodiazepine (BDZ) receptor (PBR) and diazepam-binding inhibitor/acyl-CoA-binding protein (DBI/ACBP) characterized as a ligand at central BDZ receptors, at PBR with involvement in the regulation of steroidogenesis, and as an intracellular acyl-CoA transporter, are both known to interact with BDZ in adult systems. We investigated their expression after prenatal exposure to BDZ. Diazepam (1.25 mg/kg per day s.c.) was administered to time-pregnant Long Evans rats from gestational day (GD) 14 to 20. Expression of mRNAs encoding for PBR and for DBI/ACBP was studied in the same animals with (33)P-labeled 60 mer oligonucleotides (oligos) by in situ hybridization at GD20, and with (32)P-labeled oligos by Northern blot in steroidogenic and immune organs at postnatal day (PN) 14 and in adult offspring. Prenatal diazepam increased DBI/ACBP mRNA expression in male fetal adrenal and in fetal and PN14 testis. Thymus exhibited increased DBI/ACBP mRNA in male fetuses and in adult female offspring, and reduced organ weight at PN14 in both sexes. In female spleen, an increase in DBI/ACBP mRNA and a decrease in PBR mRNA was seen at PN14. Apart from the finding in spleen, no drug-induced changes in PBR mRNA were observed. The effects of prenatal diazepam were superimposed on treatment-independent sex differences in DBI/ACBP mRNA and PBR mRNA expression. Our data indicate that expression of DBI/ACBP mRNA in steroidogenic and immune organs can be affected by exposure to BDZ during ontogeny, while PBR mRNA expression appears to be less sensitive. They further reveal marked sex differences in the developmental patterns of the two proteins during pre- and postpubertal ontogeny.

GnRH agonist treatment decreases progesterone synthesis, luteal peripheral benzodiazepine receptor mRNA, ligand binding and steroidogenic acute regulatory protein expression during pregnancy.

We have demonstrated that continuous administration of a gonadotropin-releasing hormone agonist (GnRH-Ag) suppresses luteal steroidogenesis in the pregnant rat. We further demonstrated that the peripheral-type benzodiazepine receptor (PBR) and the steroidogenic acute regulatory protein (StAR) play key roles in cholesterol transport leading to steroidogenesis. The purpose of this study was to understand the cellular and molecular mechanisms involved in the suppression of luteal steroidogenesis leading to a fall in serum progesterone levels in GnRH-Ag-treated rats during early pregnancy. Pregnant rats were treated individually starting on day 8 of pregnancy with 5 microgram/day GnRH-Ag using an osmotic minipump. Sham-operated control rats received no treatment. At 0, 4, 8 and 24 h after initiation of the treatment, rats were killed and corpora lutea (CL) were removed for PBR mRNA, protein and radioligand binding analyses, immunoblot 1-D gel analysis of StAR, P450 scc and 3beta-hydroxysteroid dehydrogenase as well as 2-D gel analysis of StAR. The treatment decreased the luteal PBR mRNA expression at all time periods starting at 4 h compared with that in corresponding sham controls. GnRH-Ag also reduced, in the CL, the PBR protein/ligand binding, the StAR protein and P450 scc protein and its activity as early as 8 h after the treatment and they remained low compared with those in corresponding sham controls. The data from 2-D gel studies suggest that the majority of the decrease in StAR protein appears to be in the phosphorylated forms of StAR. Thus, we have demonstrated, for the first time, the presence of PBR and StAR in the pregnant rat CL and that the coordinated suppression of these proteins involved in the mitochondrial cholesterol transport along with P450 scc by GnRH-Ag leads to reduced ovarian steroidogenesis.

Ontogeny of diazepam binding inhibitor/acyl-CoA binding protein mRNA and peripheral benzodiazepine receptor mRNA expression in the rat.

The Diazepam Binding Inhibitor/Acyl-CoA Binding Protein (DBI/ACBP) has been implicated in different functions, as acyl-CoA transporter and as an endogenous ligand at the GABA(A) receptor and the peripheral benzodiazepine receptor (PBR). The latter is thought to be involved in control of steroidogenesis. We studied the ontogeny of DBI/ACBP and PBR mRNA expression in embryos and offspring of time-pregnant Long Evans rats by in-situ hybridization with 33P-endlabelled oligonucleotides. Both mRNAs were present in embryo and placenta at gestational day (G)11, the earliest stage studied. DBI/ACBP mRNA was strongly expressed from embryonic through mid-foetal stages in central nervous system (maximum in neuroepithelium), cranial and sympathetic ganglia, anterior pituitary, adrenal cortex, thyroid, thymus, liver and (late foetal) brown adipose tissue, moderately in testis, heart, lung and kidney. In brain, a late foetal decrease of DBI/ACBP mRNA was followed by an increase at postnatal day 6. Peripheral benzodiazepine receptor mRNA expression started very low and increased to moderate levels in adrenal cortex and medulla, testis, thyroid, brown adipose tissue, liver, heart, lung, salivary gland at mid- to late-foetal stages. Data suggest a significant role of DBI/ACBP at early developmental stages. Both proteins may be involved in the control of foetal steroidogenesis. However, differences in developmental patterns indicate that additional functions may be equally important during ontogeny, such as the involvement in lipid metabolism in the case of DBI/ACBP.

In vivo studies on the role of the peripheral benzodiazepine receptor (PBR) in steroidogenesis

In various steroidogenic cell models, mitochondrial preparations and submito-chondrial fractions, the expression of the mitochondrial 18 kDa peripheral-type benzodiazepine receptor (PBR) protein confers the ability to take up and release, upon ligand activation, cholesterol. Thus, cholesterol becomes available to P450scc on the inner mitochondrial membrane. These in vitro studies were validated by in vivo experiments. Treatment of rats with ginkgolide B (GKB), specifically reduced the ligand binding capacity and mRNA expression of the adrenocortical PBR and circulating glucocorticoid levels. Treatment with GKB also resulted in inhibition of PBR protein synthesis and corticosterone production by isolated adrenocortical cells in response to ACTH. The ontogeny of both PBR binding capacity and protein directly paralleled that of ACTH-inducible steroidogenesis in rat adrenal cells and in rats injected with ACTH. In addition, the previously described suppression of luteal progesterone synthesis in the pregnant rat by continuous in vivo administration of a gonadotropin-releasing hormone agonist may be due to decreased luteal PBR ligand binding and mRNA. These results suggest that (i) PBR is an absolute prerequisite for adrenocortical and luteal steroidogenesis, (ii) regulation of adrenal PBR expression may be used as a tool to control circulating glucocorticoid levels and (iii) the stress hypo-responsive period of neonatal rats may result from decreased adrenal cortical PBR expression.

The human peripheral renzodiazepine receptor gene: Cloning and characterization of alternative splicing in normal tissues and in a patient with congenital lipoid adrenal hyperplasia

The mitochondrial benzodiazepine receptor (mBzR)appears to be a key factor in the flow of cholesterol into mitochondia to permit the initiation of steroid hormone synthesis. The mBzR consists of three components; the 18-kDa component on the outer mitochondrial membrane appears to contain the benzodiazepine binding site, and is hence often termed the peripheral benzodiazepine receptor (PBR). Using a cloned human PBR cDNA as probe, we have cloned the human PBR gene. The 13-kb gene is divided into four exons, with exon 1 encoding only a short 5′ untranslated segment. The 5′ flanking DNA lacks TATA and CAAT boxes but contains a cluster of SP-1 binding sites, typical of “housekeeping” genes. The encoded PBR mRNA is alternately spliced into two forms: “authentic” PBR mRNA retains all four exons, while a short form termed PBRS lacks exon 2. While PBR-S contains a 102-codon open reading frame with a typical initiator sequence, the reading frame differs from that of PBR, so that the encoded protein is unrelated to PBR. RT-PCR and RNase protection experiments confirm that both PBR and PBR-S are expressed in all tissues examined and that expression PBR-S is about 10 times the level of PBR. Expression of PBR cDNA in pCMV5 vectors transfected into COS-1 cells resulted in increased binding of [3H]PK11195, but expression of PBR-S did not. It has been speculated that patients with congenital lipoid adrenal hyperplasia, who cannot make any steroids, might have a genetic lesion in mBzR. RT-PCR analysis of testicular RNA from such a patient, sequencing of the cDNA, and blotting analysis of genomic DNA all indicate that the gene and mRNA for the PBR component of mBzR are normal in this disease.