Metabotropic Glutamate Receptor 4 (mGlu4) Positive Allosteric Modulators Lack Efficacy in Rat and Marmoset Models of L-DOPA-Induced Dyskinesia.

Background: Increased activity across corticostriatal glutamatergic synapses may contribute to L-DOPA-induced dyskinesia in Parkinson's disease. Given the weak efficacy and side-effect profile of amantadine, alternative strategies to reduce glutamate transmission are being investigated. Metabotropic glutamate receptor 4 (mGlu4) is a promising target since its activation would reduce glutamate release. Objective: We hypothesized that two mGlu4 positive allosteric modulators, Lu AF21934 ((1 S,2 R)-N1-(3,4-dichlorophenyl)cyclohexane-1,2-dicarboxamide) and ADX88178 (5-Methyl-N-(4-methylpyrimidin-2-yl)-4-(1H-pyrazol-4-yl)thiazol-2-amine), would provide relief in rat and primate models of L-DOPA-induced dyskinesia. Methods: The ability of Lu AF21934 or ADX88178 to reverse pre-established dyskinesia was examined in L-DOPA-primed 6-hydroxydopamine-lesioned rats expressing abnormal involuntary movements (AIMs) or in 1-methyl-4-phenyl,1,2,3,6-tetrahydropyridine (MPTP)-treated common marmosets expressing L-DOPA-induced dyskinesia. Additionally, the ability of Lu AF21934 to prevent the development of de novo L-DOPA-induced AIMs was explored in the 6-hydroxydopamine-lesioned rats. Results: Neither Lu AF21934 (10 or 30 mg/kg p.o.) nor ADX88178 (10 or 30 mg/kg p.o.) reduced pre-established AIMs in 6-hydroxydopamine-lesioned rats. Similarly, in L-DOPA-primed common marmosets, no reduction in established dyskinesia was observed with Lu AF21934 (3 or 10 mg/kg p.o.). Conversely, amantadine significantly reduced (>40%) the expression of dyskinesia in both models. Lu AF21934 also failed to suppress the development of AIMs in 6-hydroxydopamine-lesioned rats. Conclusions: This study found no benefit of mGlu4 positive allosteric modulators in tackling L-DOPA-induced dyskinesia. These findings are concordant with the recent failure of foliglurax in phase II clinical trials supporting the predictive validity of these pre-clinical dyskinesia models, while raising further doubt on the anti-dyskinetic potential of mGlu4 positive allosteric modulators.

Tackling Influenza A virus by M2 ion channel blockers: Latest progress and limitations.

Influenza outbreaks cause pandemics in millions of people. The treatment of influenza remains a challenge due to significant genetic polymorphism in the influenza virus. Also, developing vaccines to protect against seasonal and pandemic influenza infections is constantly impeded. Thus, antibiotics are the only first line of defense against antigenically distinct strains or new subtypes of influenza viruses. Among several anti-influenza targets, the M2 protein of the influenza virus performs several activities. M2 protein is an ion channel that permits proton conductance through the virion envelope and the deacidification of the Golgi apparatus. Both these functions are critical for viral replication. Thus, targeting the M2 protein of the influenza virus is an essential target. Rimantadine and amantadine are two well-known drugs that act on the M2 protein. However, these drugs acquired resistance to influenza and thus are not recommended to treat influenza infections. This review discusses an overview of anti-influenza therapy, M2 ion channel functions, and its working principle. It also discusses the M2 structure and its role, and the change in the structure leads to mutant variants of influenza A virus. We also shed light on the recently identified compounds acting against wild-type and mutated M2 proteins of influenza virus A. These scaffolds could be an alternative to M2 inhibitors and be developed as antibiotics for treating influenza infections.

Exploration of newly synthesized amantadine-thiourea conjugates for their DNA binding, anti-elastase, and anti-glioma potentials.

Three newly synthesized amantadine thiourea conjugates namely MS-1 N-(((3 s,5 s,7 s)-adamantan-1-yl)carbamothioyl)benzamide, MS-2 N-(((3 s,5 s,7 s)-adamantan-1-yl)carbamothioyl)-4-methylbenzamide and MS-3 N-((3 s,5 s,7 s)-adamantan-1-ylcarbamothioyl)-4-chlorobenzamide were investigated for their structures, bindings (DNA/ elastase), and for their impact on healthy and cancerous cells. Theoretical (DFT/docking) and experimental {UV-visible (UV-), fluorescence (Flu-), and cyclic voltammetry (CV)} studies indicated binding interactions of each conjugate with DNA and elastase enzyme. Theoretically and experimentally calculated binding parameters for conjugate - DNA interaction revealed MS-3 - DNA to have most significant binding with comparatively greater values of binding parameters {(Kb/M-1: docking, 3.8 × 105; UV-, 5.95 × 103; Flu-,1.55 × 105; CV, 1.52 × 104), (∆G/ kJmol-1: docking, -32.09; UV-, -22.40; Flu-,-30.81; CV, -24.82)}. The docked structures, greater bindings site size values (n), and the trend in DNA viscosity changes in the presence of each conjugate concentration confirmed a mixed binding mode of interaction among them. Conjugate - elastase binding by docking agreed with the experimental anti-elastase findings. Cytotoxicity studies of each tested conjugate demonstrated greater cytotoxicity for cancerous (MG-U87) cells in comparison to control, while for the normal (HEK-293) cells the cytotoxicity was found comparatively low. Overall exploration suggested that MS-3 is the most effective candidate for DNA binding, anti-elastase, and for anti-glioma activities.

A bridge to recovery: Acute amantadine prior to environmental enrichment after brain trauma augments cognitive benefit.

Environmental enrichment (EE) facilitates motor and cognitive recovery after traumatic brain injury (TBI). Historically, EE has been provided immediately and continuously after TBI, but this paradigm does not model the clinic where rehabilitation is typically not initiated until after critical care. Yet, treating TBI early may facilitate recovery. Hence, we sought to provide amantadine (AMT) as a bridge therapy before commencing EE. It was hypothesized that bridging EE with AMT would augment motor and cognitive benefits. Anesthetized adult male rats received a cortical impact (2.8 mm deformation at 4 m/s) or sham surgery and then were housed in standard (STD) conditions where they received intraperitoneal AMT (10 mg/kg or 20 mg/kg) or saline vehicle (VEH; 1 mL/kg) beginning 24 h after surgery and once daily during the 6-day bridge phase or once daily for 19 days for the non-bridge groups (i.e., continuously STD-housed) to compare the effects of acute AMT plus EE vs. chronic AMT alone. Abbreviated EE, which was presented to closer emulate clinical rehabilitation (e.g., 6 h/day), began on day 7 for the AMT bridge and chronic EE groups. Motor (beam-walking) and cognition (acquisition of spatial learning and memory) were assessed on days 7-11 and 14-19, respectively. Cortical lesion volume and hippocampal cell survival were quantified on day 21. EE, whether provided in combination with VEH or AMT, and AMT (20 mg/kg) + STD, benefitted motor and cognition vs. the STD-housed VEH and AMT (10 mg/kg) groups (p < 0.05). The AMT (20 mg/kg) + EE group performed better than the VEH + EE, AMT (10 mg/kg) + EE, and AMT (20 mg/kg) + STD groups in the acquisition of spatial learning (p < 0.05) but did not differ in motor function (p > 0.05). All groups receiving EE exhibited decreased cortical lesion volumes and increased CA3 neuron survival relative to the STD-housed groups (p < 0.05) but did not differ from one another (p > 0.05). The added cognitive benefit achieved by bridging EE with AMT (20 mg/kg) supports the hypothesis that the temporal separation of combinational therapies is more effective after TBI.

Dopamine-Depleted Dopamine Transporter Knockout (DDD) Mice: Dyskinesia with L-DOPA and Dopamine D1 Agonists.

L-DOPA is the mainstay of treatment for Parkinson's disease (PD). However, over time this drug can produce dyskinesia. A useful acute PD model for screening novel compounds for anti-parkinsonian and L-DOPA-induced dyskinesia (LID) are dopamine-depleted dopamine-transporter KO (DDD) mice. Treatment with α-methyl-para-tyrosine rapidly depletes their brain stores of DA and renders them akinetic. During sensitization in the open field (OF), their locomotion declines as vertical activities increase and upon encountering a wall they stand on one leg or tail and engage in climbing behavior termed "three-paw dyskinesia". We have hypothesized that L-DOPA induces a stereotypic activation of locomotion in DDD mice, where they are unable to alter the course of their locomotion, and upon encountering walls engage in "three-paw dyskinesia" as reflected in vertical counts or beam-breaks. The purpose of our studies was to identify a valid index of LID in DDD mice that met three criteria: (a) sensitization with repeated L-DOPA administration, (b) insensitivity to a change in the test context, and (c) stimulatory or inhibitory responses to dopamine D1 receptor agonists (5 mg/kg SKF81297; 5 and 10 mg/kg MLM55-38, a novel compound) and amantadine (45 mg/kg), respectively. Responses were compared between the OF and a circular maze (CM) that did not hinder locomotion. We found vertical counts and climbing were specific for testing in the OF, while oral stereotypies were sensitized to L-DOPA in both the OF and CM and responded to D1R agonists and amantadine. Hence, in DDD mice oral stereotypies should be used as an index of LID in screening compounds for PD.

Metabolic profiling to evaluate the impact of amantadine and rimantadine on the secondary metabolism of a model organism.

Metabolic profiling offers huge potential to highlight markers and mechanisms in support of toxicology and pathology investigations during drug development. The main objective was to modify therapy with adamantane derivatives: amantadine and rimantadine, to increase their bioavailability and evaluate the influence of such therapy on drug metabolism using Saccharomyces cerevisiae as the model organism. In this study, the profile of endogenous metabolites of a model organism was measured and interpreted to provide an opportunity to investigate changes induced by treatment with amantadine and rimantadine. It was found that resveratrol supplementation synergistically enhanced the effects of amantadine treatment and increased rimantadine metabolism, potentially reducing side effects. The fingerprinting strategy was used as an efficient technique for qualitatively evaluating and monitoring changes in the profiles of endogenous components and their contents in a model organism. Chemometric tools were employed to find marker compounds that can be defined as characteristic indicators of a pharmacological response to a therapeutic intervention. An improved understanding of the mechanisms involved in drug effect and an increased ability to predict individual variations in the drug response of organisms will improve the treatment process and the development of new therapies.

Amantadine for Refractory Tremor in Parkinson Disease and Other Indications: A Chart Review With Long-Term Follow-up.

OBJECTIVES: The aim of this study was to determine how amantadine was used in a movement disorders clinic and how effective it was. METHODS: A chart review over a 2-month period in 2022 of all patients in a movement disorders clinic who had ever taken amantadine was undertaken. RESULTS: One hundred six charts were included. Amantadine was initiated primarily for tremor and secondly for l -dopa-induced dyskinesias (LIDs). Sixty-two percent of tremor patients improved and tolerated amantadine; 74% of those with LID improved and tolerated the drug. Hallucinations occurred in 23%. Initiating amantadine as a syrup allowed a more conservative titration than other formulations, which is attractive given the high percentage of hallucinations that may occur. Patients who tolerated drug initiation were generally kept on the drug for many years. CONCLUSIONS: Amantadine should be considered as adjunctive therapy in Parkinson disease patients with refractory tremor as well as for LIDs.

Effects of Amantadine Sulfate on Motor Impairment and Execution of Motor Sequences in Patients With Parkinson Disease.

BACKGROUND: Intravenous application of amantadine sulfate induces a rapid improvement of motor behavior in patients with Parkinson disease. OBJECTIVES: To determine efficacy of daily infusion of 200 mg amantadine sulfate on scored motor symptoms and performance of standardized movement sequences with components of low and high cognitive efforts. METHODS: Thirty-one participants received infusions of amantadine sulfate in addition to their previous stable drug regimens on 3 consecutive days. Motor symptoms of upper limbs were determined with selected items of the part motor examination of the Unified Parkinson's Disease Rating Scale. Instrumental tasks were executed under cued conditions before and after the infusions. RESULTS: Scored motor symptoms and components with a need for a higher cognitive load became better. Performance of motion series, characterized by an automated set with low cognitive efforts, did not improve. CONCLUSION: Our trial outcomes suggest that the amantadine has a positive impact on cognitive abilities, drive, and vigilance, all of which are necessary for carrying out of higher brain functions.

The M2 proteins of bat influenza A viruses reveal atypical features compared to conventional M2 proteins.

The influenza A virus (IAV) M2 protein has proton channel activity, which plays a role in virus uncoating and may help to preserve the metastable conformation of the IAV hemagglutinin (HA). In contrast to the highly conserved M2 proteins of conventional IAV, the primary sequences of bat IAV H17N10 and H18N11 M2 proteins show remarkable divergence, suggesting that these proteins may differ in their biological function. We, therefore, assessed the proton channel activity of bat IAV M2 proteins and investigated its role in virus replication. Here, we show that the M2 proteins of bat IAV did not fully protect acid-sensitive HA of classical IAV from low pH-induced conformational change, indicating low proton channel activity. Interestingly, the N31S substitution not only rendered bat IAV M2 proteins sensitive to inhibition by amantadine but also preserved the metastable conformation of acid-sensitive HA to a greater extent. In contrast, the acid-stable HA of H18N11 did not rely on such support by M2 protein. When mutant M2(N31S) protein was expressed in the context of chimeric H18N11/H5N1(6:2) encoding HA and NA of avian IAV H5N1, amantadine significantly inhibited virus entry, suggesting that ion channel activity supported virus uncoating. Finally, the cytoplasmic domain of the H18N11 M2 protein mediated rapid internalization of the protein from the plasma membrane leading to low-level expression at the cell surface. However, cell surface levels of H18N11 M2 protein were significantly enhanced in cells infected with the chimeric H18N11/H5N1(6:2) virus. The potential role of the N1 sialidase in arresting M2 internalization is discussed. IMPORTANCE Bat IAV M2 proteins not only differ from the homologous proteins of classical IAV by their divergent primary sequence but are also unable to preserve the metastable conformation of acid-sensitive HA, indicating low proton channel activity. This unusual feature may help to avoid M2-mediated cytotoxic effects and inflammation in bats infected with H17N10 or H18N11. Unlike classical M2 proteins, bat IAV M2 proteins with the N31S substitution mediated increased protection of HA from acid-induced conformational change. This remarkable gain of function may help to understand how single point mutations can modulate proton channel activity. In addition, the cytoplasmic domain was found to be responsible for the low cell surface expression level of bat IAV M2 proteins. Given that the M2 cytoplasmic domain of conventional IAV is well known to participate in virus assembly at the plasma membrane, this atypical feature might have consequences for bat IAV budding and egress.

A Study of the Activity of Adamantyl Amines against Mutant Influenza A M2 Channels Identified a Polycyclic Cage Amine Triple Blocker, Explored by Molecular Dynamics Simulations and Solid-State NMR.

We compared the anti-influenza potencies of 57 adamantyl amines and analogs against influenza A virus with serine-31 M2 proton channel, usually termed as WT M2 channel, which is amantadine sensitive. We also tested a subset of these compounds against viruses with the amantadine-resistant L26F, V27A, A30T, G34E M2 mutant channels. Four compounds inhibited WT M2 virus in vitro with mid-nanomolar potency, with 27 compounds showing sub-micromolar to low micromolar potency. Several compounds inhibited L26F M2 virus in vitro with sub-micromolar to low micromolar potency, but only three compounds blocked L26F M2-mediated proton current as determined by electrophysiology (EP). One compound was found to be a triple blocker of WT, L26F, V27A M2 channels by EP assays, but did not inhibit V27A M2 virus in vitro, and one compound inhibited WT, L26F, V27A M2 in vitro without blocking V27A M2 channel. One compound blocked only L26F M2 channel by EP, but did not inhibit virus replication. The triple blocker compound is as long as rimantadine, but could bind and block V27A M2 channel due to its larger girth as revealed by molecular dynamics simulations, while MAS NMR informed on the interaction of the compound with M2(18-60) WT or L26F or V27A.

Altered amantadine effects after repetitive treatment for l-dopa-induced involuntary movements in a rat model of Parkinson's disease.

BACKGROUND: l-3,4-dihydroxyphenylalanine (l-dopa) is the most effective drug for Parkinson's disease (PD); however, most PD patients develop motor fluctuations including wearing-off and l-dopa-induced dyskinesia (LID). Amantadine is beneficial for improving the motor symptoms, reducing "off" time, and ameliorating LID, although its long-term efficacy remains unknown. OBJECTIVES: To investigate the effects of amantadine on PD and LID using a rat model with repetitive drug treatment. METHOD: We utilized 6-hydroxydopamine injections to develop a hemiparkinsonian rat model. The rats were assigned to four groups: five rats received l-dopa and benserazide for 31 days, six rats received l-dopa and benserazide plus amantadine for 31 days, five rats received l-dopa and benserazide for 15 days followed by l-dopa and benserazide plus amantadine for 16 days, and five rats received l-dopa and benserazide plus amantadine for 15 days followed by l-dopa and benserazide treatment for 16 days. We evaluated the l-dopa-induced abnormal involuntary movements on treatment days 1, 7, 14, 16, 22, and 29. Subsequently, immunohistochemistry for drebrin was performed. RESULTS: l-dopa-induced abnormal movements were reduced on the first day of amantadine treatment, and these effects disappeared with repetitive treatment. In contrast, the extension of l-dopa "on" time was observed after repetitive amantadine treatment. All groups showed enlarged drebrin immunoreactive dots in the dopamine-denervated striatum, indicating that amantadine did not prevent priming effects of repetitive l-dopa treatment. CONCLUSION: Anti-LID effect of amantadine diminished after repetitive treatment, and the effect of amantadine on wearing-off emerged after repetitive treatment in a hemiparkinsonian rat model. Fluctuations in amantadine effects should be considered when using it in clinical settings.

Aminoadamantanes: from treatment of Parkinson's and Alzheimer's disease to symptom amelioration of long COVID-19 syndrome?

INTRODUCTION: The aminoadamantanes amantadine and memantine are well known. They mainly act as N-methyl-D-aspartate antagonists. AREAS COVERED: The antiviral drug amantadine moderately ameliorates impaired motor behavior in patients with Parkinson's disease. Memantine provides beneficial effects on memory function in patients with advanced Alzheimer's disease already treated with acetylcholine esterase inhibitors. Both compounds counteract impaired monoamine neurotransmission with associated symptoms, such as depression. They improve vigilance, lack of attention and concentration, fatigue syndromes according to clinical findings in patients with chronic neurodegenerative processes. Their extrasynaptic N-methyl-D-Aspartate receptor blockade weakens a prolonged influx of Ca2+ ions as the main responsible components of neuronal excitotoxicity. This causes neuronal dying and associated functional deficits. EXPERT OPINION: We suggest aminoadamantanes as future therapies for amelioration of short- and long-term consequences of a COVID 19 infection. Particularly the extended-release amantadine formulations will be suitable. They showed better clinical efficacy compared with the conventional available compounds. Amantadine may particularly be suitable for amelioration of fatigue or chronic exhaustion, memantine for improvement of cognitive deficits. Clinical research in patients, who are affected by the short- and long-term consequences of a COVID 19 infection, is warranted to confirm these still hypothetical putative beneficial effects of aminoadamantanes.

The drugs amantadine and memantine are known as aminoadamantanes. Amantadine improves motor skills in patients with Parkinson's disease. It also reduces fatigue in individuals suffering from multiple sclerosis. Memantine improves memory dysfunction linked to Alzheimer's disease. Aminoadamantanes affect communication between nerve cells by supporting neurotransmission of monoamines. Clinical studies have found that these drugs benefit patients with chronic neurodegenerative diseases, who have depression, fatigue, loss of attention or concentration deficits. These brain function problems may also appear to some extent due to COVID-19 infection. We suggest that aminoadamantanes could improve these problems in COVID-19 patients in both the short and long term. Clinical research is needed to confirm this hypothesis.

Antiglycoxidative properties of amantadine - a systematic review and comprehensive in vitro study.

An important drug used in the treatment of Parkinson's disease is amantadine. We are the first to perform a comprehensive study based on various glycation and oxidation factors, determining the impact of amantadine on protein glycoxidation. Sugars (glucose, fructose, galactose) and aldehydes (glyoxal, methylglyoxal) were used as glycation agents, and chloramine T was used as an oxidant. Glycoxidation biomarkers in albumin treated with amantadine were generally not different from the control group (glycation/oxidation factors), indicating that the drug did not affect oxidation and glycation processes. Molecular docking analysis did not reveal strong binding sites of amantadine on the bovine serum albumin structure. Although amantadine poorly scavenged hydroxyl radical and hydrogen peroxide, it had significantly lower antioxidant and antiglycation effect than all protein oxidation and glycation inhibitors. In some cases, amantadine even demonstrated glycoxidant, proglycation, and prooxidant properties. In summary, amantadine exhibited weak antioxidant properties and a lack of antiglycation activity.

Hybridization of amantadine with gardenamide A enhances NMDA antagonism and in vivo anti-PD effects.

Eight hybrids of amantadine (ATD) with a natural modulator gardenamide A (GA) via an alkylene carbonyl bridge or alkylene bridge have been designed and synthesized. Evaluated by electrophysiological assay, compound 5b was confirmed an enhanced NMDAR antagonist compared to ATD with IC50 value of 10.2 ± 1.2 µM. 5b has been demonstrated to reverse the damages of behavioral performance, the loss of dopaminergic neurons, the reduction of TH positive, and the increase of α-synuclein in both MPTP-treated mice and zebrafish models. In both ethological and ecological experiments, the activity of 5b was confirmed better than ATD or ATD/GA combination, and was almost equal to the positive selegiline. In vivo and in vitro, 5b is shown to reverse the ascend of NR1 and i-NOS levels. This candidate was also demonstrated the activity to down-regulated MPTP-increased Ca2+ influx in SH-SY5Y cells in a steep and sharp mode. It is displayed that 5b exerts neuroprotective effect partly by activating the PI3K/Akt signaling pathway. Taken all together, our data support that 5b is a more promising agent against PD than ATD.

Morbidity and severity of COVID-19 in patients with Parkinson's disease treated with amantadine - A multicenter, retrospective, observational study.

BACKGROUND: After more than 2 years of the pandemic, effective treatment for COVID-19 is still under research. In recent months, publications hypothesized amantadine's potential beneficial effect on SARS-CoV-2 infection. OBJECTIVE: To compare the groups of Parkinson's Disease (PD) patients who were administered amantadine chronically and those who did not take this medication in the context of the incidence and severity of COVID-19 infection. METHODS: An observational, retrospective, multicenter cohort study was conducted among consecutive patients with idiopathic PD. The structured questionnaires were completed during the patient's follow-up visits at the Outpatient Clinic or during hospitalization. The questionnaire included the following informations: patient's age, duration of PD, Hoehn-Yahr (H-Y) stage, comorbidities, medications, COVID-19 confirmed by reverse transcription polymerase chain reaction (RT-PCR) swab test for SARS-CoV-2 with specified symptoms and their severity (home or hospital treatment). The vaccination status was verified as well. RESULTS: Five hundred fifty-two (n = 552) patients participated in the study - 329 men (60%). The mean H-Y stage was 2.44 (range: 1-4) and the mean duration of PD was 9.6 years (range: 1-34). One hundred four subjects (19%) had confirmed COVID-19 infection. Subjects over 50 years of age had a significantly lower incidence of COVID-19 (17% vs 38%, p = 0.0001) with difference also in mean H-Y stage (2.27 vs 2.49; p = 0.011) and disease duration (8.4 vs 9.9 years, p = 0.007). There were no differences between patients with and without co-morbidities. In the whole analyzed group 219 (40%) subjects were treated with amantadine. Comparing COVID-19 positive and negative patients, amantadine was used by 48/104 (46%) and 171/448 (38%) respectively. 22% of patients on amantadine vs. 17% of patients without amantadine developed COVID-19. These differences were not significant. There were no differences in morbidity and severity of COVID-19 between amantadine users and non-users as well. CONCLUSIONS: COVID-19 was less common in older (>50) with longer duration and more advanced patients. Amantadine did not affect the risk of developing COVID-19 or the severity of infection.

Inhibition of SARS-CoV-2 Viral Channel Activity Using FDA-Approved Channel Modulators Independent of Variants.

BACKGROUND: SARS-CoV-2 has undergone mutations, yielding clinically relevant variants. HYPOTHESIS: We hypothesized that in SARS-CoV-2, two highly conserved Orf3a and E channels directly related to the virus replication were a target for the detection and inhibition of the viral replication, independent of the variant, using FDA-approved ion channel modulators. METHODS: A combination of a fluorescence potassium ion assay with channel modulators was developed to detect SARS-CoV-2 Orf3a/E channel activity. Two FDA-approved drugs, amantadine (an antiviral) and amitriptyline (an antidepressant), which are ion channel blockers, were tested as to whether they inhibited Orf3a/E channel activity in isolated virus variants and in nasal swab samples from COVID-19 patients. The variants were confirmed by PCR sequencing. RESULTS: In isolated SARS-CoV-2 Alpha, Beta, and Delta variants, the channel activity of Orf3a/E was detected and inhibited by emodin and gliclazide (IC50 = 0.42 mM). In the Delta swab samples, amitriptyline and amantadine inhibited the channel activity of viral proteins, with IC50 values of 0.73 mM and 1.11 mM, respectively. In the Omicron swab samples, amitriptyline inhibited the channel activity, with an IC50 of 0.76 mM. CONCLUSIONS: We developed an efficient method to screen FDA-approved ion channel modulators that could be repurposed to detect and inhibit SARS-CoV-2 viral replication, independent of variants.

AV-101, a Pro-Drug Antagonist at the NMDA Receptor Glycine Site, Reduces L-Dopa Induced Dyskinesias in MPTP Monkeys.

N-methyl-D-aspartate (NMDA) receptors have been implicated in L-Dopa-induced dyskinesias (LID) in Parkinson's disease patients, but the use of antagonists that directly inhibit this receptor is associated with severe side effects. L-4-chlorokynurenine (4-Cl-KYN or AV-101) is a pro-drug of 7-chlorokynurenic acid (7-Cl-KYNA), a potent and specific antagonist of the glycine (GlyB) co-agonist site of NMDA receptors. The 7-Cl-KYNA has limited ability to cross the blood-brain barrier, whereas AV-101 readily accesses the brain. We investigated if AV-101 reduces LID in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys while maintaining the antiparkinsonian activity of L-Dopa. A first pilot study using three dyskinetic MPTP monkeys showed that acute AV-101 treatment (250 and 450 mg/kg) reduced LID and maintained the antiparkinsonian activity of L-Dopa. The main study using six additional dyskinetic MPTP monkeys showed that repeated AV-101 treatment (250 mg/kg, b.i.d. for 4 consecutive days) maintained their L-Dopa antiparkinsonian response. We measured significantly less LID when AV-101 was combined with L-Dopa treatment. AV-101 alone or with L-Dopa had no non-motor adverse effects in MPTP monkeys. Our study showed antidyskinetic activity of AV-101 in MPTP monkeys was comparable to amantadine tested previously in our laboratory in this model. We observed no adverse effects with AV-101, which is an improvement over amantadine, with its known side effects.

Requirement of a functional ion channel for Sindbis virus glycoprotein transport, CPV-II formation, and efficient virus budding.

Many viruses encode ion channel proteins that oligomerize to form hydrophilic pores in membranes of virus-infected cells and the viral membrane in some enveloped viruses. Alphavirus 6K, human immunodeficiency virus type 1 Vpu (HIV-Vpu), influenza A virus M2 (IAV-M2), and hepatitis C virus P7 (HCV-P7) are transmembrane ion channel proteins that play essential roles in virus assembly, budding, and entry. While the oligomeric structures and mechanisms of ion channel activity are well-established for M2 and P7, these remain unknown for 6K. Here we investigated the functional role of the ion channel activity of 6K in alphavirus assembly by utilizing a series of Sindbis virus (SINV) ion channel chimeras expressing the ion channel helix from Vpu or M2 or substituting the entire 6K protein with full-length P7, in cis. We demonstrate that the Vpu helix efficiently complements 6K, whereas M2 and P7 are less efficient. Our results indicate that while SINV is primarily insensitive to the M2 ion channel inhibitor amantadine, the Vpu inhibitor 5-N, N-Hexamethylene amiloride (HMA), significantly reduces SINV release, suggesting that the ion channel activity of 6K similar to Vpu, promotes virus budding. Using live-cell imaging of SINV with a miniSOG-tagged 6K and mCherry-tagged E2, we further demonstrate that 6K and E2 colocalize with the Golgi apparatus in the secretory pathway. To contextualize the localization of 6K in the Golgi, we analyzed cells infected with SINV and SINV-ion channel chimeras using transmission electron microscopy. Our results provide evidence for the first time for the functional role of 6K in type II cytopathic vacuoles (CPV-II) formation. We demonstrate that in the absence of 6K, CPV-II, which originates from the Golgi apparatus, is not detected in infected cells, with a concomitant reduction in the glycoprotein transport to the plasma membrane. Substituting a functional ion channel, M2 or Vpu localizing to Golgi, restores CPV-II production, whereas P7, retained in the ER, is inadequate to induce CPV-II formation. Altogether our results indicate that ion channel activity of 6K is required for the formation of CPV-II from the Golgi apparatus, promoting glycoprotein spike transport to the plasma membrane and efficient virus budding.

Neuroprotective effects of amantadine for experimental acute carbon monoxide poisoning.

OBJECTIVE: Amantadine is known to have a neuroprotective effect in many neurological diseases. This study aims at investigating the neuroprotective effect of amantadine in rats exposed to carbon monoxide (CO) poisoning. MATERIALS AND METHODS: Rats were maintained under standard experimental laboratory conditions and randomized into 4 different groups of 7 each namely control, amantadine only, CO exposure, and amantadine + CO exposure. For immunohistochemical analysis, tissues taken from the prefrontal and hippocampal regions were taken into formalin and kept for at least one day. Afterward, the tissue was followed and blocked for paraffin blocking. N-Methyl D-Aspartate (NMDA) levels in homogenates were studied by the Enzyme-Linked Immunosorbent Assay (ELISA) method. Superoxide dismutase (SOD) and catalase (CAT) activities in the supernatants were studied with commercial kits. Nitric oxide (NO) and Asymmetric Dimethyl Arginine (ADMA) levels were studied by the ELISA method. Enzyme activity values were calculated by dividing the protein values in the supernatants and normalizing them. RESULTS: CAT, SOD, NMDA, ADMA, and NO levels were statistically significantly different between the groups (p < 0.05). According to post-hoc pairwise comparison test results, the values of the control and amantadine groups for CAT, SOD, NMDA, ADMA, and NO parameters were significantly higher than that of CO group. Similarly, values in the control and amantadine groups were considerably higher than values for the amantadine + CO group. NMDA values were significantly lower in group amantadine + CO than in CO group (p: 0.049). CONCLUSIONS: Apoptosis and endothelial damage after CO poisoning is a complex process, and amantadine administration has a limited contribution in preventing this process.

Amantadine and Rimantadine Inhibit Hepatitis A Virus Replication through the Induction of Autophagy.

Hepatitis A virus (HAV) infection is a major cause of acute viral hepatitis worldwide. Furthermore, HAV causes acute liver failure or acute-on-chronic liver failure. However, no potent anti-HAV drugs are currently available in the clinical situations. There have been some reports that amantadine, a broad-spectrum antiviral, suppresses HAV replication in vitro. Therefore, we examined the effects of amantadine and rimantadine, derivates of adamantane, on HAV replication, and investigated the mechanisms of these drugs. In the present study, we evaluated the effects of amantadine and rimantadine on HAV HM175 genotype IB subgenomic replicon replication and HAV HA11-1299 genotype IIIA replication in cell culture infection systems. Amantadine and rimantadine significantly inhibited HAV replication at the post-entry stage in Huh7 cells. HAV infection inhibited autophagy by suppressing the autophagy marker light chain 3 and reducing number of lysosomes. Proteomic analysis on HAV-infected Huh7 cells treated by amantadine and rimantadine revealed the changes of the expression levels in 42 of 373 immune response-related proteins. Amantadine and rimantadine inhibited HAV replication, partially through the enhancement of autophagy. Taken together, our results suggest a novel mechanism by which HAV replicates along with the inhibition of autophagy and that amantadine and rimantadine inhibit HAV replication by enhancing autophagy. IMPORTANCE Amantadine, a nonspecific antiviral medication, also effectively inhibits HAV replication. Autophagy is an important cellular mechanism in several virus-host cell interactions. The results of this study provide evidence indicating that autophagy is involved in HAV replication and plays a role in the HAV life cycle. In addition, amantadine and its derivative rimantadine suppress HAV replication partly by enhancing autophagy at the post-entry phase of HAV infection in human hepatocytes. Amantadine may be useful for the control of acute HAV infection by inhibiting cellular autophagy pathways during HAV infection processes.