Intravenous flumazenil for Parkinson's disease: a single dose, double blind, placebo controlled, cross-over trial

The Impact of Probiotics on Clinical Symptoms and Peripheral Cytokines Levels in Parkinson's Disease: Preliminary In Vivo Data

Introduction. Previous studies have shown that probiotics have positive effects on both motor and non-motor symptoms in Parkinson's disease (PD). Additionally, in preclinical settings, probiotics have demonstrated the ability to counteract neuronal loss and alpha-synuclein aggregation, important pathological hallmarks of PD. Notably, preliminary in vitro studies have revealed the immunomodulatory properties of probiotics. This study aims to evaluate the impact of probiotics on symptoms and peripheral cytokines levels in PD patients compared to placebo. Methods. Patients were enrolled and blindly randomized to receive either active probiotics (comprising Bifidobacterium animalis subsp. lactis BS01 LMG P-21384, Bifidobacterium longum BL03 DSM 16603, Bifidobacterium adolescentis BA02 DSM 18351, Fructo-oligosaccharides and Maltodextrin-Group A) or placebo (Maltodextrin-Group B). Clinical evaluations and plasma levels cytokines (TNF-α, IFN-γ, IL-6, and TGF-β) were also assessed at enrollment and after 12 weeks. Anti-parkinsonian therapy remained stable throughout the study. Results. Forty PD patients were recruited. After 12 weeks, Group A showed significant improvement in motor symptoms (UPDRS III: 13.89 ± 4.08 vs. 12.74 ± 4.57, p = 0.028) and non-motor symptoms (NMSS: 34.32 ± 21.41 vs. 30.11 ± 19.89, p = 0.041), with notable improvement in the gastrointestinal sub-item (3.79 ± 4.14 vs. 1.89 ± 2.54, p = 0.021). A reduction of IFN-γ levels was observed in both groups, but group A also showed a significant decrease in IL-6 and a slight increase in the anti-inflammatory cytokine TGF-β. Conclusions. Our data suggest that probiotics may modulate peripheral cytokines levels and improve clinical symptoms in PD patients. Probiotics may, therefore, represent a valuable adjunctive therapy to conventional anti-parkinsonian drugs.

Neuroactive steroids and Parkinson's disease: Review of human and animal studies

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

GABAA Receptor Benzodiazepine Binding Sites and Motor Impairments in Parkinson's Disease

Flumazenil is an allosteric modulator of the γ-aminobutyric acid-A receptor (GABAAR) benzodiazepine binding site that could normalize neuronal signaling and improve motor impairments in Parkinson's disease (PD). Little is known about how regional GABAAR availability affects motor symptoms. We investigated the relationship between regional availability of GABAAR benzodiazepine binding sites and motor impairments in PD. Methods: A total of 11 Patients with PD (males; mean age 69.0 ± 4.6 years; Hoehn and Yahr stages 2-3) underwent [11C]flumazenil GABAAR benzodiazepine binding site and [11C]dihydrotetrabenazine vesicular monoamine transporter type-2 (VMAT2) PET imaging and clinical assessment. Stepwise regression analysis was used to predict regional cerebral correlates of the four cardinal UPDRS motor scores using cortical, striatal, thalamic, and cerebellar flumazenil binding estimates. Thalamic GABAAR availability was selectively associated with axial motor scores (R2 = 0.55, F = 11.0, β = -6.4, p = 0.0009). Multi-ligand analysis demonstrated significant axial motor predictor effects by both thalamic GABAAR availability (R2 = 0.47, β = -5.2, F = 7.2, p = 0.028) and striatal VMAT2 binding (R2 = 0.30, β = -3.9, F = 9.1, p = 0.019; total model: R2 = 0.77, F = 11.9, p = 0.0056). Post hoc analysis demonstrated that thalamic [11C]methyl-4-piperidinyl propionate cholinesterase PET and K1 flow delivery findings were not significant confounders. Findings suggest that reduced thalamic GABAAR availability correlates with worsened axial motor impairments in PD, independent of nigrostriatal degeneration. These findings may augur novel non-dopaminergic approaches to treating axial motor impairments in PD.

Search for Novel Therapies for Essential Tremor Based on Positive Modulation of α6-Containing GABAA Receptors

Background

Prior work using GABAA receptor subunit knockouts and the harmaline model has indicated that low-dose alcohol, gaboxadol, and ganaxolone suppress tremor via α6βδ GABAA receptors. This suggests that drugs specifically enhancing the action of α6βδ or α6βγ2 GABAA receptors, both predominantly expressed on cerebellar granule cells, would be effective against tremor. We thus examined three drugs described by in vitro studies as selective α6βδ (ketamine) or α6βγ2 (Compound 6, flumazenil) receptor modulators.

Methods

In the first step of evaluation, the maximal dose was sought at which 6/6 mice pass straight wire testing, a sensitive test for psychomotor impairment. Only non-impairing doses were used to evaluate for anti-tremor efficacy in the harmaline model, which was assessed in wildtype and α6 subunit knockout littermates.

Results

Ketamine, in maximally tolerated doses of 2.0 and 3.5 mg/kg had minimal effect on harmaline tremor in both genotypes. Compound 6, at well-tolerated doses of 1-10 mg/kg, effectively suppressed tremor in both genotypes. Flumazenil suppressed tremor in wildtype mice at doses (0.015-0.05 mg/kg) far lower than those causing straight wire impairment, and did not suppress tremor in α6 knockout mice.

Discussion

Modulators of α6βδ and α6βγ2 GABAA receptors warrant attention for novel therapies as they are anticipated to be effective and well-tolerated. Ketamine likely failed to attain α6βδ-active levels. Compound 6 is an attractive candidate, but further study is needed to clarify its mechanism of action. The flumazenil results provide proof of principle that targeting α6βγ2 receptors represents a worthy strategy for developing essential tremor therapies.

Highlights

We tested for harmaline tremor suppression drugs previously described as in vitro α6βδ or α6βγ2 GABAA receptor-selective modulators. Well-tolerated flumazenil doses suppressed tremor in α6-wildtype but not α6-knockout mice. Compound 6 and ketamine failed to display this profile, likely from off-target effects. Selective α6 modulators hold promise as tremor therapy.

Fluoroquinolone-Associated Movement Disorder: A Literature Review

BACKGROUND

Fluoroquinolones (FQNs) are related to several central nervous system side effects. This review aims to evaluate the clinical-epidemiological profile, pathophysiological mechanisms, and management of FQNs-associated movement disorders (MDs).

METHODS

Two reviewers identified and assessed relevant reports in six databases without language restriction between 1988 and 2022.

RESULTS

A total of 45 reports containing 51 cases who developed MDs secondary to FQNs were reported. The MDs included 25 myoclonus, 13 dyskinesias, 7 dystonias, 2 cerebellar syndromes, 1 ataxia, 1 tic, and 2 undefined cases. The FQNs reported were ciprofloxacin, ofloxacin, gatifloxacin, moxifloxacin, levofloxacin, gemifloxacin, and pefloxacin. The mean and median age were 64.54 (SD: 15.45) and 67 years (range: 25-87 years). The predominant sex was male (54.16%). The mean and median time of MD onset were 6.02 (SD: 10.87) and 3 days (range: 1-68 days). The mean and median recovery time after MD treatment was 5.71 (SD: 9.01) and 3 days (range: 1-56 days). A complete recovery was achieved within one week of drug withdrawal in 80.95% of the patients. Overall, 95.83% of the individuals fully recovered after management.

CONCLUSIONS

Future cases need to describe the long-term follow-up of the individuals. Additionally, FQN-induced myoclonus should include electrodiagnostic studies.

Effects of GABAa receptor antagonists on motor behavior in pharmacological Parkinson's disease model in mice

The aim of this study was to evaluate the effects of two gamma‐amino butyric acid (GABA)a receptor antagonists on motor behavioral tasks in a pharmacological model of Parkinson disease (PD) in rodents. Ninety‐six Swiss mice received intraperitoneal injection of Haloperidol (1 mg/kg) to block dopaminergic receptors. GABAa receptors antagonists Bicuculline (1 and 5 mg/kg) and Flumazenil (3 and 6 mg/kg) were used for the assessment of the interaction among these neurotransmitters, in this PD model. The motor behavior of the animals was evaluated in the catalepsy test (30, 60, and 90 min after drugs application), through open field test (after 60 min) and trough functional gait assessment (after 60 min). Both Bicuculline and Flumazenil were able to partially reverse catalepsy induced by Haloperidol. In the open field test, Haloperidol reduced the number of horizontal and vertical exploration of the animals, which was not reversed trough application of GABAa antagonists. Furthermore, the functional gait assessment was not sensitive enough to detect motor changes in this animal model of PD. There is an interaction between dopamine and GABA in the basal ganglia and the blocking GABAa receptors may have therapeutic potential in the treatment of PD.

Flumazenil for the Treatment of Refractory Hypersomnolence: Clinical Experience with 153 Patients

STUDY OBJECTIVES

Patients with central disorders of hypersomnolence sometimes do not achieve satisfactory symptom control with currently available wake-promoting medications. Based on the finding that the cerebrospinal fluid from some patients with hypersomnolence demonstrates potentiation of gamma-aminobutyric acid (GABA)-A receptors in excess of that of controls, a finding that reverses with flumazenil, we initiated prescribing compounded flumazenil to carefully selected, treatment-refractory hypersomnolent patients.

METHODS

This retrospective chart review evaluated the first 153 consecutive patients treated with transdermal and/or sublingual flumazenil by physicians at our center from 2013 through January 2015.

RESULTS

Patients were 35.5 y old (± 14.4) and 92 (60.1%) were women. Mean Epworth Sleepiness Scale scores prior to flumazenil were 15.1 (± 4.5) despite prior or current treatment with traditional wake-promoting therapies. Symptomatic benefit was noted by 96 patients (62.8%), with a mean reduction in Epworth Sleepiness Scale score of 4.7 points (± 4.7) among responders. Of these, 59 remained on flumazenil chronically, for a mean of 7.8 mo (± 6.9 mo). Female sex and presence of reported sleep inertia differentiated flumazenil responders from nonresponders. Adverse events were common, but often did not result in treatment discontinuation. Serious adverse events included a transient ischemic attack and a lupus vasculopathy, although whether these events occurred because of flumazenil administration is unknown.

CONCLUSIONS

This chart review demonstrates that sublingual and transdermal flumazenil provided sustained clinical benefit to 39% of patients with treatment-refractory hypersomnolence. Prospective, controlled studies of this GABA-A receptor antagonist for the treatment of hypersomnolence are needed.

COMMENTARY

A commentary on this article appears in this issue on page 1321.

Investigation of Proposed Activity of Clarithromycin at GABAA Receptors Using [(11)C]Flumazenil PET

Clarithromycin is a potential treatment for hypersomnia acting through proposed negative allosteric modulation of GABAA receptors. We were interested whether this therapeutic benefit might extend to Parkinson's disease (PD) patients because GABAergic neurotransmission is implicated in postural control. Prior to initiating clinical studies in PD patients, we wished to better understand clarithromycin's mechanism of action. In this work we investigated whether the proposed activity of clarithromycin at the GABAA receptor is associated with the benzodiazepine binding site using in vivo [(11)C]flumazenil positron emission tomography (PET) in primates and ex vivo [(3)H]flumazenil autoradiography in rat brain. While the studies demonstrate that clarithromycin does not change the K d of FMZ, nor does it competitively displace FMZ, there is preliminary evidence from the primate PET imaging studies that clarithromycin delays dissociation and washout of flumazenil from the primate brain in a dose-dependent fashion. These findings would be consistent with the proposed GABAA allosteric modulator function of clarithromycin. While the results are only preliminary, further investigation of the interaction of clarithromycin with GABA receptors and/or GABAergic medications is warranted, and therapeutic applications of clarithromycin alone or in combination with flumazenil, to treat hyper-GABAergic status in PD at minimally effective doses, should also be pursued.

Neurosteroid and neurotransmitter alterations in Parkinson's disease

Parkinson's disease (PD) is associated with a massive loss of dopaminergic cells in the substantia nigra leading to dopamine hypofunction and alteration of the basal ganglia circuitry. These neurons, are under the control, among others, of the excitatory glutamatergic and inhibitory γ-aminobutyric acid (GABA) systems. An imbalance between these systems may contribute to excitotoxicity and dopaminergic cell death. Neurosteroids, a group of steroid hormones synthesized in the brain, modulate the function of several neurotransmitter systems. The substantia nigra of the human brain expresses high concentrations of allopregnanolone (3α, 5αtetrahydroprogesterone), a neurosteroid that positively modulates the action of GABA at GABAA receptors and of 5α-dihydroprogesterone, a neurosteroid acting at the genomic level. This article reviews the roles of NS acting as neuroprotectants and as GABAA receptor agonists in the physiology and pathophysiology of the basal ganglia, their impact on dopaminergic cell activity and survival, and potential therapeutic application in PD.

Globus pallidus plays a critical role in neurotrophic factor induced functional improvements in hemiparkinsonian monkeys

This study was designed to test the hypothesis that the integrity of the globus pallidus (GP) is critical for neurotrophic factor, such as glial-derived neurotrophic factor (GDNF), induced functional changes in rhesus macaques with MPTP-induced parkinsonism, because our previous studies demonstrated that the GP was one of the most affected areas as assessed by the levels of dopamine (DA) and its metabolites. A group of eight hemiparkinsonian monkeys with pallidal lesions, which positively responsed to intraventricular (ICV) injections of GDNF prior to the lesions, and a group of eight hemiparkinsonian monkeys without pallidal lesions, were treated with GDNF after a long washout period after the initial ICV infusions of GDNF. Significant behavioral improvements were only seen in the monkeys without pallidal lesions that received GDNF. Monkeys with pallidal lesions failed to exhibit any behavioral improvement even though they had elevated nigral DA levels. The results suggest that the GP is critical for neurotrophic factor induced functional changes in PD monkeys.