Dissecting the molecular determinants of GABAA receptors current rundown, a hallmark of refractory human epilepsy

GABAA receptors-(Rs) are fundamental for the maintenance of an efficient inhibitory function in the central nervous system (CNS). Their dysfunction is associated with a wide range of CNS disorders, many of which characterized by seizures and epilepsy. Recently, an increased use-dependent desensitization due to a repetitive GABA stimulation (GABAA current rundown) of GABAARs has been associated with drug-resistant temporal lobe epilepsy (TLE). Here, we aimed to investigate the molecular determinants of GABAA current rundown with two different heterologous expression systems (Xenopus oocytes and human embryonic kidney cells; HEK) which allowed us to manipulate receptor stoichiometry and to study the GABAA current rundown on different GABAAR configurations. To this purpose, we performed electrophysiology experiments using two-electrode voltage clamp in oocytes and confirming part of our results in HEK. We found that different degrees of GABAA current rundown can be associated with the expression of different GABAAR beta-subunits reaching the maximum current decrease when functional alpha1beta2 receptors are expressed. Furthermore, the blockade of phosphatases can prevent the current rundown observed in alpha1beta2 GABAARs. Since GABAAR represents one important therapeutic target in the treatment of human epilepsy, our results could open new perspectives on the therapeutic management of drug-resistant patients showing a GABAergic impairment

Neuromuscular magnetic stimulation counteracts muscle decline in ALS patients: results of a randomized, double-blind, controlled study

The aim of the study was to verify whether neuromuscular magnetic stimulation (NMMS) improves muscle function in spinal-onset amyotrophic lateral sclerosis (ALS) patients. Twenty-two ALS patients were randomized in two groups to receive, daily for two weeks, NMMS in right or left arm (referred to as real-NMMS, rNMMS), and sham NMMS (sNMMS) in the opposite arm. All the patients underwent a median nerve conduction (compound muscle action potential, CMAP) study and a clinical examination that included a handgrip strength test and an evaluation of upper limb muscle strength by means of the Medical Research Council Muscle Scale (MRC). Muscle biopsy was then performed bilaterally on the flexor carpi radialis muscle to monitor morpho-functional parameters and molecular changes. Patients and physicians who performed examinations were blinded to the side of real intervention. The primary outcome was the change in the muscle strength in upper arms. The secondary outcomes were the change from baseline in the CMAP amplitudes, in the nicotinic ACh currents, in the expression levels of a selected panel of genes involved in muscle growth and atrophy, and in histomorphometric parameters of ALS muscle fibers. The Repeated Measures (RM) ANOVA with a Greenhouse-Geisser correction (sphericity not assumed) showed a significant effect [F(3, 63) = 5.907, p < 0.01] of rNMMS on MRC scale at the flexor carpi radialis muscle, thus demonstrating that the rNMMS significantly improves muscle strength in flexor muscles in the forearm. Secondary outcomes showed that the improvement observed in rNMMS-treated muscles was associated to counteracting muscle atrophy, down-modulating the proteolysis, and increasing the efficacy of nicotinic ACh receptors (AChRs). We did not observe any significant difference in pre- and post-stimulation CMAP amplitudes, evoked by median nerve stimulation. This suggests that the improvement in muscle strength observed in the stimulated arm is unlikely related to reinnervation. The real and sham treatments were well tolerated without evident side effects. Although promising, this is a proof of concept study, without an immediate clinical translation, that requires further clinical validation

GABA(A) receptor function is enhanced by Interleukin-10 in human epileptogenic gangliogliomas and its effect is counteracted by Interleukin-1 beta

Gangliogliomas (GGs) are low-grade brain tumours that cause intractable focal epilepsy in children and adults. In GG, as in epileptogenic focal malformations (i.e., tuberous sclerosis complex, TSC), there is evidence of sustained neuroinflammation with involvement of the pro-inflammatory cytokine IL-1β. On the other hand, anti-inflammatory mediators are less studied but bear relevance for understanding seizure mechanisms. Therefore, we investigated the effect of the key anti-inflammatory cytokine IL-10 on GABAergic neurotransmission in GG. We assessed the IL-10 dependent signaling by transcriptomic analysis, immunohistochemistry and performed voltage-clamp recordings on Xenopus oocytes microtransplanted with cell membranes from brain specimens, to overcome the limited availability of acute GG slices. We report that IL-10-related mRNAs were up-regulated in GG and slightly in TSC. Moreover, we found IL-10 receptors are expressed by neurons and astroglia. Furthermore, GABA currents were potentiated significantly by IL-10 in GG. This effect was time and dose-dependent and inhibited by blockade of IL-10 signaling. Notably, in the same tissue, IL-1β reduced GABA current amplitude and prevented the IL-10 effect. These results suggest that in epileptogenic tissue, pro-inflammatory mechanisms of hyperexcitability prevail over key anti-inflammatory pathways enhancing GABAergic inhibition. Hence, boosting the effects of specific anti-inflammatory molecules could resolve inflammation and reduce intractable seizures

Impaired GABAergic regulation and developmental immaturity in interneurons derived from the medial ganglionic eminence in the tuberous sclerosis complex

GABAergic interneurons play a critical role in maintaining neural circuit balance, excitation-inhibition regulation, and cognitive function modulation. In tuberous sclerosis complex (TSC), GABAergic neuron dysfunction contributes to disrupted network activity and associated neurological symptoms, assumingly in a cell type-specific manner. This GABAergic centric study focuses on identifying specific interneuron subpopulations within TSC, emphasizing the unique characteristics of medial ganglionic eminence (MGE)- and caudal ganglionic eminence (CGE)-derived interneurons. Using single-nuclei RNA sequencing in TSC patient material, we identify somatostatin-expressing (SST+) interneurons as a unique and immature subpopulation in TSC. The disrupted maturation of SST+ interneurons may undergo an incomplete switch from excitatory to inhibitory GABAergic signaling during development, resulting in reduced inhibitory properties. Notably, this study reveals markers of immaturity specifically in SST+ interneurons, including an abnormal NKCC1/KCC2 ratio, indicating an imbalance in chloride homeostasis crucial for the postsynaptic consequences of GABAergic signaling as well as the downregulation of GABA A receptor subunits, GABRA1, and upregulation of GABRA2. Further exploration of SST+ interneurons revealed altered localization patterns of SST+ interneurons in TSC brain tissue, concentrated in deeper cortical layers, possibly linked to cortical dyslamination. In the epilepsy context, our research underscores the diverse cell type-specific roles of GABAergic interneurons in shaping seizures, advocating for precise therapeutic considerations. Moreover, this study illuminates the potential contribution of SST+ interneurons to TSC pathophysiology, offering insights for targeted therapeutic interventions

Innovative syntheses of heterocycles via transition-metal or organic catalysis

Dottorato di ricerca in Methodologies for the Development of Molecules of pharmacological Interest XXII CicloUniversità della Calabri

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