An activator of voltage-gated K+ channels Kv1.1 as a therapeutic candidate for episodic ataxia type 1

Loss-of-function mutations in the KCNA1(Kv1.1) gene cause episodic ataxia type 1 (EA1), a neurological disease characterized by cerebellar dysfunction, ataxic attacks, persistent myokymia with painful cramps in skeletal muscles, and epilepsy. Precision medicine for EA1 treatment is currently unfeasible, as no drug that can enhance the activity of Kv1.1-containing channels and offset the functional defects caused by KCNA1 mutations has been clinically approved. Here, we uncovered that niflumic acid (NFA), a currently prescribed analgesic and anti-inflammatory drug with an excellent safety profile in the clinic, potentiates the activity of Kv1.1 channels. NFA increased Kv1.1 current amplitudes by enhancing the channel open probability, causing a hyperpolarizing shift in the voltage dependence of both channel opening and gating charge movement, slowing the OFF-gating current decay. NFA exerted similar actions on both homomeric Kv1.2 and heteromeric Kv1.1/Kv1.2 channels, which are formed in most brain structures. We show that through its potentiating action, NFA mitigated the EA1 mutation-induced functional defects in Kv1.1 and restored cerebellar synaptic transmission, Purkinje cell availability, and precision of firing. In addition, NFA ameliorated the motor performance of a knock-in mouse model of EA1 and restored the neuromuscular transmission and climbing ability in Shaker (Kv1.1) mutant Drosophila melanogaster flies (Sh5). By virtue of its multiple actions, NFA has strong potential as an efficacious single-molecule-based therapeutic agent for EA1 and serves as a valuable model for drug discovery

An Unbalanced Synaptic Transmission: Cause or Consequence of the Amyloid Oligomers Neurotoxicity?

Amyloid-β (Aβ) 1-40 and 1-42 peptides are key mediators of synaptic and cognitive dysfunction in Alzheimer’s disease (AD). Whereas in AD, Aβ is found to act as a pro-epileptogenic factor even before plaque formation, amyloid pathology has been detected among patients with epilepsy with increased risk of developing AD. Among Aβ aggregated species, soluble oligomers are suggested to be responsible for most of Aβ’s toxic effects. Aβ oligomers exert extracellular and intracellular toxicity through different mechanisms, including interaction with membrane receptors and the formation of ion-permeable channels in cellular membranes. These damages, linked to an unbalance between excitatory and inhibitory neurotransmission, often result in neuronal hyperexcitability and neural circuit dysfunction, which in turn increase Aβ deposition and facilitate neurodegeneration, resulting in an Aβ-driven vicious loop. In this review, we summarize the most representative literature on the effects that oligomeric Aβ induces on synaptic dysfunction and network disorganization

From synaptic dysfunction to neuroprotective strategies in genetic Parkinson’s disease: lessons from LRRK2

The pathogenesis of Parkinson’s disease (PD) is thought to rely on a complex interaction between the patient’s genetic background and a variety of largely unknown environmental factors. In this scenario, the investigation of the genetic bases underlying familial PD could unveil key molecular pathways to be targeted by new disease-modifying therapies, still currently unavailable. Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are responsible for the majority of inherited familial PD cases and can also be found in sporadic PD, but the pathophysiological functions of LRRK2 have not yet been fully elucidated. Here, we will review the evidence obtained in transgenic LRRK2 experimental models, characterized by altered striatal synaptic transmission, mitochondrial dysfunction, and α-synuclein aggregation. Interestingly, the processes triggered by mutant LRRK2 might represent early pathological phenomena in the pathogenesis of PD, anticipating the typical neurodegenerative features characterizing the late phases of the disease. A comprehensive view of LRRK2 neuronal pathophysiology will support the possible clinical application of pharmacological compounds targeting this protein, with potential therapeutic implications for patients suffering from both familial and sporadic PD

Identification of a new de novo mutation underlying regressive episodic ataxia type I

Episodic ataxia type 1 (EA1), a Shaker-like K+channelopathy, is a consequence of genetic anomalies in the KCNA1 gene that lead to dysfunctions in the voltage-gated K+channel Kv1. 1. Generally, KCNA1 mutations are inherited in an autosomal dominant manner. Here we report the clinical phenotype of an EA1 patient characterized by ataxia attacks that decrease in frequency with age, and eventually leading to therapy discontinuation. A new de novo mutation (c.932G>A) that changed a highly conserved glycine residue into an aspartate (p. G311D) was identified by using targeted next-generation sequencing. The conserved glycine is located in the S4-S5 linker, a crucial domain controlling Kv1.1 channel gating. In silico analyses predicted the mutation deleterious. Heterologous expression of the mutant (Kv1.1-G311D) channels resulted in remarkably decreased amplitudes of measured current, confirming the identified variant is pathogenic. Collectively, these findings corroborate the notion that EA1 also results from de novo variants and point out that regardless of the mutation-induced deleterious loss of Kv1.1 channel function the ataxia phenotype may improve spontaneously

Low doses of Perampanel protect striatal and hippocampal neurons against in vitro ischemia by reversing the ischemia-induced alteration of AMPA receptor subunit composition

Energy depletion caused by ischemic brain insults may result in persistent neuronal depolarization accompanied by hyper-stimulation of ionotropic glutamate receptors and excitotoxic phenomena, possibly leading to cell death. The use of glutamate receptor antagonists, such as the AMPARs antagonist Perampanel (PER), might be a pharmacological approach to counteract the excessive over-activation of glutamate receptors providing neuroprotective effects. Using electrophysiological and molecular analyses, we investigated the effect of PER against in vitro ischemia obtained by oxygen and glucose deprivation (OGD) in rat slices of two brain structures particularly sensitive to ischemic insults, the nucleus striatum and the hippocampus. We found that in these regions PER was able to avoid the OGD-induced neuronal suffering, at low doses not reducing basal excitatory synaptic transmission and not altering long-term potentiation (LTP) induction. Furthermore, in both the analysed regions, PER blocked the pathological form of LTP, namely ischemic LTP (iLTP). Finally, we hypothesized that the protective effect of PER against OGD was due to its capability to normalize the subunit synaptic localization and function of AMPAR altered after an ischemic insult. Taken together these findings support the idea that PER is a drug potentially effective to counteract in vivo ischemic damage

Data_Sheet_1_Identification of a New de Novo Mutation Underlying Regressive Episodic Ataxia Type I.DOCX

<p>Episodic ataxia type 1 (EA1), a Shaker-like K⁺channelopathy, is a consequence of genetic anomalies in the KCNA1 gene that lead to dysfunctions in the voltage-gated K⁺ channel Kv1. 1. Generally, KCNA1 mutations are inherited in an autosomal dominant manner. Here we report the clinical phenotype of an EA1 patient characterized by ataxia attacks that decrease in frequency with age, and eventually leading to therapy discontinuation. A new de novo mutation (c.932G>A) that changed a highly conserved glycine residue into an aspartate (p.G311D) was identified by using targeted next-generation sequencing. The conserved glycine is located in the S4–S5 linker, a crucial domain controlling Kv1.1 channel gating. In silico analyses predicted the mutation deleterious. Heterologous expression of the mutant (Kv1.1-G311D) channels resulted in remarkably decreased amplitudes of measured current, confirming the identified variant is pathogenic. Collectively, these findings corroborate the notion that EA1 also results from de novo variants and point out that regardless of the mutation-induced deleterious loss of Kv1.1 channel function the ataxia phenotype may improve spontaneously.</p

Striatal spreading depolarization: Possible implication in levodopa-induced dyskinetic-like behavior

OBJECTIVE: Spreading depolarization (SD) is a transient self-propagating wave of neuronal and glial depolarization coupled with large membrane ionic changes and a subsequent depression of neuronal activity. Spreading depolarization in the cortex is implicated in migraine, stroke, and epilepsy. Conversely, spreading depolarization in the striatum, a brain structure deeply involved in motor control and in Parkinson's disease (PD) pathophysiology, has been poorly investigated. METHODS: We characterized the participation of glutamatergic and dopaminergic transmission in the induction of striatal spreading depolarization by using a novel approach combining optical imaging, measurements of endogenous DA levels, and pharmacological and molecular analyses. RESULTS: We found that striatal spreading depolarization requires the concomitant activation of D1-like DA and N-methyl-d-aspartate receptors, and it is reduced in experimental PD. Chronic l-dopa treatment, inducing dyskinesia in the parkinsonian condition, increases the occurrence and speed of propagation of striatal spreading depolarization, which has a direct impact on one of the signaling pathways downstream from the activation of D1 receptors. CONCLUSION: Striatal spreading depolarization might contribute to abnormal basal ganglia activity in the dyskinetic condition and represents a possible therapeutic target

Dopamine-dependent early synaptic and motor dysfunctions induced by \u3b1-synuclein in the nigrostriatal circuit

Misfolding and aggregation of \u3b1-synuclein are specific features of Parkinson's disease and other neurodegenerative diseases defined as synucleinopathies. Parkinson's disease progression has been correlated with the formation and the extracellular release of \u3b1-synuclein aggregates, as well as with their spreading from neuron to neuron. Therapeutic interventions in the initial stages of Parkinson's disease require a clear understanding of the mechanisms by which \u3b1-synuclein disrupts the physiological synaptic and plastic activity of the basal ganglia. For this reason, here we have identified two early time points to clarify how the intrastriatal injection of \u3b1-synuclein preformed fibrils in rodents, via retrograde transmission, induces time-dependent electrophysiological and behavioral alterations. We found that intrastriatal \u3b1-synuclein preformed fibrils perturb the firing rate of dopaminergic neurons of the substantia nigra pars compacta while the discharge of putative GABAergic cells of the substantia nigra pars reticulata is unchanged. The \u3b1-synuclein-induced dysregulation of nigrostriatal function also impairs, in a time-dependent manner, the two main forms of striatal synaptic plasticity, long-term potentiation and long-term depression. We also observed an increased glutamatergic transmission measured as an augmented frequency of spontaneous excitatory synaptic currents. These changes in neuronal function in the substantia nigra pars compacta and striatum were observed before overt neuronal death occurred. In an additional set of experiments, we were able to rescue \u3b1-synuclein-induced alterations of motor function, striatal synaptic plasticity, and increased spontaneous excitatory synaptic currents by a sub-chronic treatment with L-Dopa, a precursor of dopamine widely used in the therapy of Parkinson's disease, clearly demonstrating that a dysfunctional dopamine system plays a critical role in the early phases of the disease