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The Journal of Pharmacology and... Jan 2024Botulinum neurotoxin (BoNT) is a potent protein toxin that causes muscle paralysis and death by asphyxiation. Treatments for symptomatic botulism are intubation and...
Botulinum neurotoxin (BoNT) is a potent protein toxin that causes muscle paralysis and death by asphyxiation. Treatments for symptomatic botulism are intubation and supportive care until respiratory function recovers. Aminopyridines have recently emerged as potential treatments for botulism. The clinically approved drug 3,4-diaminopyridine (3,4-DAP) rapidly reverses toxic signs of botulism and has antidotal effects when continuously administered in rodent models of lethal botulism. Although the therapeutic effects of 3,4-DAP likely result from the reversal of diaphragm paralysis, the corresponding effects on respiratory physiology are not understood. Here, we combined unrestrained whole-body plethysmography (UWBP) with arterial blood gas measurements to study the effects of 3,4-DAP, and other aminopyridines, on ventilation and respiration at terminal stages of botulism in mice. Treatment with clinically relevant doses of 3,4-DAP restored ventilation in a dose-dependent manner, producing significant improvements in ventilatory parameters within 10 minutes. Concomitant with improved ventilation, 3,4-DAP treatment reversed botulism-induced respiratory acidosis, restoring blood levels of CO, pH, and lactate to normal physiologic levels. Having established that 3,4-DAP-mediated improvements in ventilation were directly correlated with improved respiration, we used UWBP to quantitatively evaluate nine additional aminopyridines in BoNT/A-intoxicated mice. Multiple aminopyridines were identified with comparable or enhanced therapeutic efficacies compared with 3,4-DAP, including aminopyridines that selectively improved tidal volume versus respiratory rate and vice versa. In addition to contributing to a growing body of evidence supporting the use of aminopyridines to treat clinical botulism, these data lay the groundwork for the development of aminopyridine derivatives with improved pharmacological properties. SIGNIFICANCE STATEMENT: There is a critical need for fast-acting treatments to reverse respiratory paralysis in patients with botulism. This study used unrestrained, whole-body plethysmography and arterial blood gas analysis to show that aminopyridines rapidly restore ventilation and respiration and reverse respiratory acidosis when administered to mice at terminal stages of botulism. In addition to supporting the use of aminopyridines as first-line treatments for botulism symptoms, these data are expected to contribute to the development of new aminopyridine derivatives with improved pharmacological properties.
Topics: Mice; Humans; Animals; Botulism; Aminopyridines; Amifampridine; Acidosis, Respiratory; Botulinum Toxins, Type A; Paralysis; Respiration
PubMed: 37977816
DOI: 10.1124/jpet.123.001773 -
Cureus Jan 2024After a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, approximately 10-20% of patients are affected by the post-COVID syndrome (PCS). This...
After a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, approximately 10-20% of patients are affected by the post-COVID syndrome (PCS). This condition leads to a variety of functional complaints, including symptoms of fatigue. To date, there is still no adequate treatment option. Five patients are presented, including the self-observation of one of the authors, in whom the administration of amifampridine as an "off-label use" led to a normalization of the unphysiologically increased need for sleep with a simultaneous increase in the Bell score. This effect was confirmed in a double-blind discontinuation trial (the medication was discontinued on a trial basis) in two of the patients. The five patients, who were previously unable to lead a normal life due to their fatigue symptoms, were able to return to everyday life after treatment with amifampridine. This offers hope to millions of affected patients.
PubMed: 38406122
DOI: 10.7759/cureus.52935 -
Medicine Sep 2017To report our experience on 7 patients (4 males and 3 females), affected by nonparaneoplastic Lambert-Eaton myasthenic syndrome, treated with 3,4-diaminopyridine...
RATIONALE
To report our experience on 7 patients (4 males and 3 females), affected by nonparaneoplastic Lambert-Eaton myasthenic syndrome, treated with 3,4-diaminopyridine phosphate (3,4-DAPP) either alone or in combination with other immunosuppressants or steroids.
PATIENT CONCERNS
Patients have been evaluated at specific timepoints (ie, baseline and last 5 year follow-up), with neurological examination, autoantibodies against presynaptic voltage-gated Cav2.1 (P/Q type) calcium ion channel (VGCC) dosage, neurophysiological evaluation focusing on the increased amplitude of the compound muscle action potential (cMAP) after maximum voluntary effort, quantitative myasthenia gravis (QMG) and activities of daily living scales, and autonomic nervous system involvement evaluation.
OUTCOMES
Five out of 7 patients presented a clinical improvement persisting at last 5-year follow-up; 2 out of them improved taking only 3,4-DAPP at the maximal dosage, whereas the remaining received concomitant medications, such as prednisone and azathioprine. However, the clinical amelioration was not statistically significant. No one of the patients reported severe adverse events, except one, complaining of transient chin and perioral paresthesias. A significant association between QMG and the type of pharmacological drugs therapy (P = .028) emerged. Indeed, we observed an improvement of the clinical condition in all 3 subjects treated with 3,4-DAPP and prednisone.
CONCLUSIONS
In this study, we confirm 3,4-DAPP treatment efficacy on muscle strength, but minor evidence of drug effectiveness have been demonstrated on the autonomic nervous system involvement and on the deep tendon reflexes reappearance, a part from patients who received 3,4-DAPP associated to prednisone.
Topics: 4-Aminopyridine; Activities of Daily Living; Adult; Amifampridine; Azathioprine; Drug Therapy, Combination; Female; Humans; Immunosuppressive Agents; Lambert-Eaton Myasthenic Syndrome; Male; Middle Aged; Muscle Strength; Prednisone; Severity of Illness Index; Treatment Outcome
PubMed: 28930822
DOI: 10.1097/MD.0000000000007839 -
Tremor and Other Hyperkinetic Movements... Oct 2020The diagnosis of a paroxysmal dyskinesia is difficult and status dystonicus is a rare life threatening movement disorder characterised by severe, frequent or continuous...
The diagnosis of a paroxysmal dyskinesia is difficult and status dystonicus is a rare life threatening movement disorder characterised by severe, frequent or continuous episodes of dystonic spasms. A 25 year old woman with chronic ataxia and paroxysmal dyskinesia presented with facial twitching, writhing of arms, oculogyric crisis and visual and auditory hallucinations. She developed respiratory failure and was ventilated. No cause was found so whole exome sequencing was performed and this revealed a novel, non-synonymous heterozygous variant in exon 11 of the gene, K457E (c 1369A>G) in the patient but not her parents. This variant has not been previously reported in gnomAD or ClinVar. The finding of a de novo variant in a potassium channel gene guided a trial of the potassium channel antagonist 3,4 diaminopyridine resulting in significant improvement, discharge from the intensive care unit and ultimately home.
Topics: Adult; Amifampridine; Ataxia; Chorea; Dystonia; Electroencephalography; Female; Hallucinations; Humans; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Ocular Motility Disorders; Potassium Channel Blockers
PubMed: 33178487
DOI: 10.5334/tohm.549 -
The Journal of Biological Chemistry 20213,4-Diaminopyridine (3,4-DAP) increases transmitter release from neuromuscular junctions (NMJs), and low doses of 3,4-DAP (estimated to reach ∼1 μM in serum) are the...
3,4-Diaminopyridine (3,4-DAP) increases transmitter release from neuromuscular junctions (NMJs), and low doses of 3,4-DAP (estimated to reach ∼1 μM in serum) are the Food and Drug Administration (FDA)-approved treatment for neuromuscular weakness caused by Lambert-Eaton myasthenic syndrome. Canonically, 3,4-DAP is thought to block voltage-gated potassium (Kv) channels, resulting in prolongation of the presynaptic action potential (AP). However, recent reports have shown that low millimolar concentrations of 3,4-DAP have an off-target agonist effect on the Cav1 subtype ("L-type") of voltage-gated calcium (Cav) channels and have speculated that this agonist effect might contribute to 3,4-DAP effects on transmitter release at the NMJ. To address 3,4-DAP's mechanism(s) of action, we first used the patch-clamp electrophysiology to characterize the concentration-dependent block of 3,4-DAP on the predominant presynaptic Kv channel subtypes found at the mammalian NMJ (Kv3.3 and Kv3.4). We identified a previously unreported high-affinity (1-10 μM) partial antagonist effect of 3,4-DAP in addition to the well-known low-affinity (0.1-1 mM) antagonist activity. We also showed that 1.5-μM DAP had no effects on Cav1.2 or Cav2.1 current. Next, we used voltage imaging to show that 1.5- or 100-μM 3,4-DAP broadened the AP waveform in a dose-dependent manner, independent of Cav1 calcium channels. Finally, we demonstrated that 1.5- or 100-μM 3,4-DAP augmented transmitter release in a dose-dependent manner and this effect was also independent of Cav1 channels. From these results, we conclude that low micromolar concentrations of 3,4-DAP act solely on Kv channels to mediate AP broadening and enhance transmitter release at the NMJ.
Topics: Acetylcholine; Action Potentials; Amifampridine; Animals; Calcium Channels, L-Type; Calcium Channels, N-Type; Dose-Response Relationship, Drug; Female; Gene Expression; Male; Mice; Microelectrodes; Neuromuscular Agents; Neuromuscular Junction; Potassium Channel Blockers; Presynaptic Terminals; Rana pipiens; Shaw Potassium Channels; Tissue Culture Techniques
PubMed: 33465376
DOI: 10.1016/j.jbc.2021.100302 -
Journal of Neurophysiology Dec 2016The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which...
The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (Ca: Ca1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of Ca to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. Ca is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, Ca activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, Ca boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, Ca either suppresses or enhances firing at sound levels that evoke maximum firing. Ca multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level.
Topics: 4-Aminopyridine; Acoustic Stimulation; Action Potentials; Amifampridine; Animals; Biophysical Phenomena; Calcium; Calcium Channel Blockers; Calcium Channels, L-Type; Excitatory Amino Acid Antagonists; In Vitro Techniques; Inferior Colliculi; Mice; Mice, Inbred CBA; Neurons; Nimodipine; Potassium Channel Blockers; Quinoxalines; Sound; Wakefulness; omega-Conotoxin GVIA
PubMed: 27605536
DOI: 10.1152/jn.00657.2016 -
Scientific Reports Nov 2017Botulinum neurotoxins (BoNTs) are highly potent toxins that cleave neuronal SNARE proteins required for neurotransmission, causing flaccid paralysis and death by...
Botulinum neurotoxins (BoNTs) are highly potent toxins that cleave neuronal SNARE proteins required for neurotransmission, causing flaccid paralysis and death by asphyxiation. Currently, there are no clinical treatments to delay or reverse BoNT-induced blockade of neuromuscular transmission. While aminopyridines have demonstrated varying efficacy in transiently reducing paralysis following BoNT poisoning, the precise mechanisms by which aminopyridines symptomatically treat botulism are not understood. Here we found that activity-dependent potentiation of presynaptic voltage-gated calcium channels (VGCCs) underlies 3,4-diaminopyridine (3,4-DAP)-mediated rescue of neurotransmission in central nervous system synapses and mouse diaphragm neuromuscular junctions fully intoxicated by BoNT serotype A. Combinatorial treatments with 3,4-DAP and VGCC agonists proved synergistic in restoring suprathreshold endplate potentials in mouse diaphragms fully intoxicated by BoNT/A. In contrast, synapses fully intoxicated by BoNT serotypes D or E were refractory to synaptic rescue by any treatment. We interpret these data to propose that increasing the duration or extent of VGCC activation prolongs the opportunity for low-efficiency fusion by fusogenic complexes incorporating BoNT/A-cleaved SNAP-25. The identification of VGCC agonists that rescue neurotransmission in BoNT/A-intoxicated synapses provides compelling evidence for potential therapeutic utility in some cases of human botulism.
Topics: Amifampridine; Animals; Botulinum Toxins, Type A; Botulism; Calcium; Calcium Channels; Excitatory Postsynaptic Potentials; Humans; Mice; Neuromuscular Junction; Neurons; Paralysis; Serogroup; Synapses; Synaptic Transmission; Synaptosomal-Associated Protein 25
PubMed: 29158500
DOI: 10.1038/s41598-017-16064-3 -
Chemical Communications (Cambridge,... Mar 20163,4-Diaminopyridine has shown promise in reversing botulinum intoxication, but poor pharmacokinetics and a narrow therapeutic window limit its clinical utility. Thus, we...
3,4-Diaminopyridine has shown promise in reversing botulinum intoxication, but poor pharmacokinetics and a narrow therapeutic window limit its clinical utility. Thus, we developed a pH-dependent oral delivery platform using club moss spore exines. These exine microcapsules slowed 3,4-diaminopyridine absorption, limited its seizure activity, and enabled delivery of doses which prolonged mouse survival after botulism neurotoxin A intoxication.
Topics: 4-Aminopyridine; Administration, Oral; Amifampridine; Botulinum Toxins, Type A; Capsules; Lycopodium; Microscopy, Electron, Scanning
PubMed: 26906286
DOI: 10.1039/c6cc00615a -
Cureus May 2024Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune neuromuscular disorder caused by pathogenic autoantibodies directed against voltage-gated calcium channels...
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune neuromuscular disorder caused by pathogenic autoantibodies directed against voltage-gated calcium channels present on the presynaptic nerve terminal. For LEMS patients refractory to initial symptomatic treatment with amifampridine, immunomodulatory therapy with intravenous immunoglobulin (IVIG) is often utilized. However, in the authors' review of literature, the utility of subcutaneous immunoglobulin (SCIG) in the treatment of LEMS has been scarcely reported. Here, we present a unique case of non-paraneoplastic LEMS managed with SCIG with excellent clinical response and improvement on electromyography. SCIG therapy may be a reasonable alternative for patients with LEMS who do not tolerate the intravenous formulation.
PubMed: 38903354
DOI: 10.7759/cureus.60773 -
The Journal of Physiology Aug 2014Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder in which a significant fraction of the presynaptic P/Q-type Ca(2+) channels critical to the triggering...
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder in which a significant fraction of the presynaptic P/Q-type Ca(2+) channels critical to the triggering of neurotransmitter release at the neuromuscular junction (NMJ) are thought to be removed. There is no cure for LEMS, and the current most commonly used symptomatic treatment option is a potassium channel blocker [3,4-diaminopyridine (3,4-DAP)] that does not completely reverse symptoms and can have dose-limiting side-effects. We previously reported the development of a novel Ca(2+) channel agonist, GV-58, as a possible alternative treatment strategy for LEMS. In this study, we tested the hypothesis that the combination of GV-58 and 3,4-DAP will elicit a supra-additive increase in neurotransmitter release at LEMS model NMJs. First, we tested GV-58 in a cell survival assay to assess potential effects on cyclin-dependent kinases (Cdks) and showed that GV-58 did not affect cell survival at the relevant concentrations for Ca(2+) channel effects. Then, we examined the voltage dependence of GV-58 effects on Ca(2+) channels using patch clamp techniques; this showed the effects of GV-58 to be dependent upon Ca(2+) channel opening. Based on this mechanism, we predicted an interaction between 3,4-DAP and GV-58. We tested this hypothesis using a mouse passive transfer model of LEMS. Using intracellular electrophysiological ex vivo recordings, we demonstrated that a combined application of 3,4-DAP plus GV-58 had a supra-additive effect that completely reversed the deficit in neurotransmitter release magnitude at LEMS model NMJs. This reversal contrasts with the less significant improvement observed with either compound alone. Our data indicate that a combination of 3,4-DAP and GV-58 represents a promising treatment option for LEMS and potentially for other disorders of the NMJ.
Topics: 4-Aminopyridine; Amifampridine; Animals; Calcium Channel Agonists; Cell Line, Tumor; Drug Synergism; Female; Humans; Lambert-Eaton Myasthenic Syndrome; Mice; Neuromuscular Junction; Potassium Channel Blockers; Purines; Synaptic Potentials; Thiophenes
PubMed: 25015919
DOI: 10.1113/jphysiol.2014.276493