The role of transcriptional and translational mechanisms in flumazenil-induced up-regulation of recombinant GABA(A) receptors

Outcomes of patients treated with low-dose flumazenil for benzodiazepine detoxification: A description of 26 participants

INTRODUCTION

Benzodiazepines are commonly prescribed for a variety of indications and can be employed in the short- and long-term. While they are efficacious, issues arise from long-term use with the emergence of dependence and tolerance to doses within the therapeutic range and beyond. Discontinuation from benzodiazepines can be problematic for patients and may result in a withdrawal syndrome, which can be protracted and last months to years.

METHODS

26 participants received low-dose subcutaneous flumazenil infusions (4 mg/24 h for approximately eight days) as part of a randomised control crossover trial. Return to benzodiazepine use was assessed monthly for three months based on the benzodiazepine use in the previous week. Where data was not available, the treating psychiatrist examined patient files and clinical documents to determine benzodiazepine use. Withdrawal and craving scores were also measured.

RESULTS

Abstinence rates from benzodiazepines at one-, two-, and three-month follow ups were 65.4 %, 50.0 %, and 46.2 % respectively. When considering patient files and clinical documents for those lost to follow-up, abstinence rates were higher at 73.1 %, 65.4 % and 61.5 % at the one-, two-, and three-month follow ups respectively. Withdrawal and craving scores were higher in those that had returned to any benzodiazepine use.

CONCLUSION

Self-reported rates of abstinence from benzodiazepines at three months was between 46.2 % and 61.5 %. Flumazenil may yield greater success than benzodiazepine tapering from high dose benzodiazepine use (≥30 mg diazepam equivalent). Further research should compare abstinence rates after treatment with flumazenil compared to benzodiazepine tapering in high dose benzodiazepine users.

Bioinformatics Analysis of Potential Biomarkers and Pathway Identification for Major Depressive Disorder

Aiming at a more comprehensive understanding of the molecular biomarkers and potential mechanisms of major depressive disorder (MDD), from the Gene Expression Omnibus (GEO) database, we first obtained mRNA expression profiles and identified 585 differentially expressed genes (DEGs) through the R software, including 263 upregulated genes and 322 downregulated genes. Then, through the Kyoto Encyclopedia of Genome and Genome (KEGG) pathway and biological process (BP) analysis, we found that the upregulated and downregulated DEGs were abundant in different pathways, respectively. It was noteworthy that upregulated DEGs were the most significantly enriched in the mTOR signaling pathway. Subsequently, through the protein-protein interaction (PPI) network, we identified seven hub genes, namely, EXOSC2, CAMK2A, PRIM1, SMC4, TYMS, CDK6, and RPA2. Finally, through gene set enrichment analysis (GSEA), we obtained that hypoxia, epithelial-mesenchymal transition, hedgehog signaling, and reactive oxygen species pathway were the enriched pathways for MDD patients. The above data results would provide a new direction for the treatment of MDD patients.

Chronic treatment with anesthetic propofol improves cognitive function and attenuates caspase activation in both aged and Alzheimer's disease transgenic mice

There is a need to seek new treatment(s) for Alzheimer's disease (AD). A recent study showed that AD patients may have decreased levels of functional GABA receptors. Propofol, a commonly used anesthetic, is a GABA receptor agonist. We therefore set out to perform a proof of concept study to determine whether chronic treatment with propofol (50 mg/kg/week) can improve cognitive function in both aged wild-type (WT) and AD transgenic (Tg) mice. Propofol was administrated to the WT and AD Tg mice once a week for 8 or 12 weeks, respectively. Morris water maze was used to assess the cognitive function of the mice following the propofol treatment. Activation of caspase-3, caspase-9, and caspase-8 was investigated using western blot analysis at the end of the propofol treatment. In the mechanistic studies, effects of propofol, amyloid-β protein (Aβ), and GABA receptor antagonist flumazenil on caspase-3 activation and opening of the mitochondrial permeability transition pore were assessed in H4 human neuroglioma and mouse neuroblastoma cells by western blot analysis and flow cytometry. Here we showed that the propofol treatment improved cognitive function and attenuated brain caspase-3 and caspase-9 activation in both aged WT and AD Tg mice. Propofol attenuated Aβ-induced caspase-3 activation and opening of the mitochondrial permeability transition pore in the cells, and flumazenil inhibited the propofol's effects. These results suggested that propofol might improve cognitive function via attenuating the Aβ-induced mitochondria dysfunction and caspase activation, which explored the potential that anesthetic propofol could improve cognitive function in elderly and AD patients.

High dose benzodiazepine dependence: description of 29 patients treated with flumazenil infusion and stabilised with clonazepam

The withdrawal syndrome from benzodiazepine (BZD) can be severe and in some cases may impede cessation of the use of the drug. We present here a case series of benzodiazepine detoxification by flumazenil infusion, stabilised with clonazepam. Patients were treated with flumazenil 1.35 mg/day for a median of 7 days. Self-reported physical withdrawal symptoms were recorded daily. In addition to flumazenil, antidepressants were given before treatment commenced and clonazepam was administered nightly with both being continued after discharge. Twenty-nine patients were treated. No patients dropped out from the treatment programme. Nine patients (31%) required a temporary reduction/cessation of the infusion. The linear trend in the reduction of the daily withdrawal scores in the overall study population was significant. The linear trends were also significant in the group of patients for whom a temporary reduction/suspension of the flumazenil was required. Six months after treatment, 15 patients (53%) were abstinent from clonazepam and other BZDs. For five (21%) the BZD dependence were reinstated. More than two-thirds of the subjects tolerated the procedure well and about half had a good long term response. Slow flumazenil infusion appears to merit consideration as a possible future treatment. Suggestions for future research are examined.

The effects of zolpidem treatment on GABA(A) receptors in cultured cerebellar granule cells: changes in functional coupling

AIMS

Hypnotic zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) action, with preferential although not exclusive binding for α1 subunit-containing GABA(A) receptors. The pharmacological profile of this drug is different from that of classical benzodiazepines, although it acts through benzodiazepine binding sites at GABA(A) receptors. The aim of this study was to further explore the molecular mechanisms of GABA(A) receptor induction by zolpidem.

MAIN METHODS

In the present study, we explored the effects of two-day zolpidem (10 μM) treatment on GABA(A) receptors on the membranes of rat cerebellar granule cells (CGCs) using [(3)H]flunitrazepam binding and semi-quantitative PCR analysis.

KEY FINDINGS

Two-day zolpidem treatment of CGCs did not significantly affect the maximum number (B(max)) of [(3)H]flunitrazepam binding sites or the expression of α1 subunit mRNA. However, as shown by decreased GABA [(3)H]flunitrazepam binding, two-day exposure of CGCs to zolpidem caused functional uncoupling of GABA and benzodiazepine binding sites at GABA(A) receptor complexes.

SIGNIFICANCE

If functional uncoupling of GABA and benzodiazepine binding sites at GABA(A) receptors is the mechanism responsible for the development of tolerance following long-term administration of classical benzodiazepines, chronic zolpidem treatment may induce tolerance.

Rapid brain-derived neurotrophic factor-dependent sequestration of amygdala and hippocampal GABA(A) receptors via different tyrosine receptor kinase B-mediated phosphorylation pathways

During the consolidation of fear memory, it has been shown that GABA(A) receptors (GABA(A)R) are rapidly downregulated in amygdala. This rapid decrease in GABA(A)R functioning may permit transient hyperexcitablity, contributing to cellular mechanisms of memory consolidation. Memory consolidation also requires brain-derived neurotrophic factor (BDNF) activation of tyrosine receptor kinase B (TrkB) receptors in the amygdala and hippocampus. We hypothesized that rapid internalization of GABA(A)Rα1 is mediated via TrkB activation of PKA and PKC-dependent processes. Primary neuronal cell cultures, from postnatal day 14-21 mouse amygdala and hippocampus, were analyzed with immunofluorescence using cell-surface, whole-cell permeabilization, and antibody internalization techniques, as well as with (3)H-muscimol binding assays. In both hippocampal and amygdala cultures, we found a >60% reduction in surface GABA(A)Rα1 within 5 min of BDNF treatment. Notably, the rapid decrease in surface GABA(A)Rα1 was confirmed biochemically using surface biotinylation assays followed by western blotting. This rapid effect was accompanied by TrkB phosphorylation and increased internal GABA(A)Rα1 immunofluorescence, and was blocked by k252a, a broad-spectrum tyrosine kinase antagonist. To further demonstrate TrkB specificity, we used previously characterized TrkB(F616A) mice, in which the highly selective TrkB-mutant specific antagonist, 1NMPP1, prevented the BDNF-dependent GABA(A)Rα1 internalization. In hippocampus, we found both PKA and PKC inhibition, using Rp-8-Br-cAMP and Calphostin C, respectively, blocked GABA(A)Rα1 internalization, whereas inhibition of MAPK (U0126) and PI3K (LY294002) did not prevent rapid internalization. By contrast in amygdala cultures, Rp-8-Br-cAMP had no effect. Together, these data suggest that rapid GABA(A)R internalization during memory consolidation is BDNF-TrkB dependent. Further, it appears that hippocampal GABA(A)R internalization is PKA and PKC dependent, while it may be primarily PKC dependent in amygdala, implying differential roles for TrkB-dependent kinase activation in BDNF-dependent memory formation.

The effects of zolpidem treatment and withdrawal on the in vitro expression of recombinant alpha1beta2gamma2s GABA(A) receptors expressed in HEK 293 cells

Zolpidem, a widely used hypnotic drug which acts through benzodiazepine binding sites, is a positive allosteric modulator of gamma-aminobutyric acid (GABA) action with preferential affinity for GABA(A) receptors containing alpha1 subunit. The pharmacological profile of zolpidem is different from that of classical benzodiazepines. The aim of this study was to find out whether zolpidem treatment triggers adaptive changes in the recombinant alpha1 subunit-containing GABA(A) receptors other than those observed following treatment with classical benzodiazepine-diazepam. Radioligand binding studies showed that 2-day exposure of human embryonic kidney (HEK) 293 cells stably expressing recombinant alpha1beta2gamma2s GABA(A) receptors to zolpidem (10 muM) up-regulated the maximum number (B (max)) of [(3)H]flunitrazepam, [(3)H]muscimol, and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding sites without changing their affinity (K (d)), suggesting an increase in total GABA(A) receptor number. Semi-quantitative RT-PCR analysis demonstrated increased levels of alpha1 subunit mRNA, while Western blot demonstrated up-regulated gamma2 subunit proteins, suggesting that zolpidem induced de novo synthesis of receptors proteins, at both the transcriptional and translational levels. GABA-induced potentiation of [(3)H]flunitrazepam binding to membranes obtained from zolpidem-treated cells was markedly reduced, indicating allosteric uncoupling between GABA and benzodiazepine binding sites. The number of benzodiazepine and convulsant binding sites as well as the functional coupling between GABA and benzodiazepine binding sites normalized in 24 h following discontinuation of zolpidem treatment. The results of our in vitro studies suggest that a 2-day exposure of recombinant alpha1 subunit-containing GABA(A) receptors stably transfected in HEK 293 cells to zolpidem induces adaptive changes in this selective GABA(A) receptor subtype, which are not substantially different from those obtained after prolonged exposure of cells to high concentrations of diazepam.

The role of flumazenil in the treatment of benzodiazepine dependence: physiological and psychological profiles

Two-related studies are presented here, detailing our early experience with benzodiazepine-dependent patients treated with a four-day flumazenil infusion using a novel delivery technique. Patients with long-term benzodiazepine dependence who attended the Australian Medical Procedures Research Foundation (AMPRF, Perth, Australia) for treatment were recruited for these studies. Self-reported psychological and physical symptoms, as well as objective vital signs data were collected at intervals before, during and 2 weeks postinfusion. Study A is a case series with cardiovascular measures; study B is an open trial that tracks the psychological profiles of 13 subjects. Withdrawal symptoms were tracked, however, the nature and severity of these symptoms differed between patients. No major complications or discomfort prompting study dropout was observed. Significant benzodiazepine abstinence occurred with this flumazenil infusion method despite high levels of initial dependence, comorbid substance use and comorbid psychiatric illness. Low-dose flumazenil infusion appears to be a safe and effective treatment resulting in withdrawal symptoms of lesser severity than any other cessation method currently available. Recommendations for future research are discussed.