Two Signaling Modes Are Better than One: Flux-Independent Signaling by Ionotropic Glutamate Receptors Is Coming of Age

Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamatergic transmission can be mediated by ionotropic glutamate receptors (iGluRs), which mediate rapid synaptic depolarization that can be associated with Ca2+ entry and activity-dependent change in the strength of synaptic transmission, as well as by metabotropic glutamate receptors (mGluRs), which mediate slower postsynaptic responses through the recruitment of second messenger systems. A wealth of evidence reported over the last three decades has shown that this dogmatic subdivision between iGluRs and mGluRs may not reflect the actual physiological signaling mode of the iGluRs, i.e., α-amino-3-hydroxy-5-methyl-4-isoxasolepropionic acid (AMPA) receptors (AMPAR), kainate receptors (KARs), and N-methyl-D-aspartate (NMDA) receptors (NMDARs). Herein, we review the evidence available supporting the notion that the canonical iGluRs can recruit flux-independent signaling pathways not only in neurons, but also in brain astrocytes and cerebrovascular endothelial cells. Understanding the signaling versatility of iGluRs can exert a profound impact on our understanding of glutamatergic synapses. Furthermore, it may shed light on novel neuroprotective strategies against brain disorders.

Bilateral temporal lobe dysplasia and seizure onset associated with biallelic CNTNAP2 variants

Biallelic CNTNAP2 variants have been associated with Pitt-Hopkins-like syndrome. We describe six novel and one previously reported patients from six independent families and review the literature including 64 patients carrying biallelic CNTNAP2 variants. Initial reports highlighted intractable focal seizures and the failure of epilepsy surgery in children, but subsequent reports did not expand on this aspect. In all our patients (n = 7), brain MRI showed bilateral temporal gray/white matter blurring with white matter high signal intensity, more obvious on the T2-FLAIR sequences, consistent with bilateral temporal lobe dysplasia. All patients had focal seizures with temporal lobe onset and semiology, which were recorded on EEG in five, showing bilateral independent temporal onset in four. Epilepsy was responsive to anti-seizure medications in two patients (2/7, 28.5%), and pharmaco-resistant in five (5/7, 71.5%). Splice-site variants identified in five patients (5/7, 71.5%) were the most common mutational finding. Our observation expands the phenotypic and genetic spectrum of biallelic CNTNAP2 alterations focusing on the neuroimaging features and provides evidence for an elective bilateral anatomoelectroclinical involvement of the temporal lobes in the associated epilepsy, with relevant implications on clinical management.

Refining the electroclinical spectrum of NPRL3-related epilepsy: A novel multiplex family and literature review

OBJECTIVE

NPRL3-related epilepsy (NRE) is an emerging condition set within the wide GATOR-1 spectrum with a particularly heterogeneous and elusive phenotypic expression. Here, we delineated the genotype-phenotype spectrum of NRE, reporting an illustrative familial case and reviewing pertinent literature.

METHODS

Through exome sequencing (ES), we investigated a 12-year-old girl with recurrent focal motor seizures during sleep, suggestive of sleep-related hypermotor epilepsy (SHE), and a family history of epilepsy in siblings. Variant segregation analysis was performed by Sanger sequencing. All previously published NRE patients were thoroughly reviewed and their electroclinical features were analyzed and compared with the reported subjects.

RESULTS

In the proband, ES detected the novel NPRL3 frameshift variant (NM_001077350.3): c.151_152del (p.Thr51Glyfs*5). This variant is predicted to cause a loss of function and segregated in one affected brother. The review of 76 patients from 18 publications revealed the predominance of focal-onset seizures (67/74-90%), with mainly frontal and frontotemporal (32/67-47.7%), unspecified (19/67-28%), or temporal (9/67-13%) onset. Epileptic syndromes included familial focal epilepsy with variable foci (FFEVF) (29/74-39%) and SHE (11/74-14.9%). Fifteen patients out of 60 (25%) underwent epilepsy surgery, 11 of whom achieved complete seizure remission (11/15-73%). Focal cortical dysplasia (FCD) type 2A was the most frequent histopathological finding.

SIGNIFICANCE

We reported an illustrative NPRL3-related epilepsy (NRE) family with incomplete penetrance. This condition consists of a heterogeneous spectrum of clinical and neuroradiological features. Focal-onset motor seizures are predominant, and almost half of the cases fulfill the criteria for SHE or FFEVF. MRI-negative cases are prevalent, but the association with malformations of cortical developments (MCDs) is significant, especially FCD type 2a. The beneficial impact of epilepsy surgery in patients with MCD-related epilepsy further supports the inclusion of brain MRI in the workup of NRE patients.

The Effects of CYP2C19 Genotype on Proxies of SSRI Antidepressant Response in the UK Biobank

Selective serotonin reuptake inhibitors (SSRIs) are the most commonly used psychopharmaceutical treatment for major depressive disorder (MDD), but individual responses to SSRIs vary greatly. CYP2C19 is a key enzyme involved in the metabolism of several drugs, including SSRIs. Variations in the CYP2C19 gene are associated with differential metabolic activity, and thus differential SSRI exposure; accordingly, the CYP2C19 genotype may affect the therapeutic response and clinical outcomes, though existing evidence of this link is not entirely consistent. Therefore, we analysed data from the UK Biobank, a large, deeply phenotyped prospective study, to investigate the effects of CYP2C19 metaboliser phenotypes on several clinical outcomes derived from primary care records, including multiple measures of antidepressant switching, discontinuation, duration, and side effects. In this dataset, 24,729 individuals were prescribed citalopram, 3012 individuals were prescribed escitalopram, and 12,544 individuals were prescribed sertraline. Consistent with pharmacological expectations, CYP2C19 poor metabolisers on escitalopram were more likely to switch antidepressants, have side effects following first prescription, and be on escitalopram for a shorter duration compared to normal metabolisers. CYP2C19 poor and intermediate metabolisers on citalopram also exhibited increased odds of discontinuation and shorter durations relative to normal metabolisers. Generally, no associations were found between metabolic phenotypes and proxies of response to sertraline. Sensitivity analyses in a depression subgroup and metabolic activity scores corroborated results from the primary analysis. In summary, our findings suggest that CYP2C19 genotypes, and thus metabolic phenotypes, may have utility in determining clinical responses to SSRIs, particularly escitalopram and citalopram, though further investigation of such a relationship is warranted.

Exosomes: Potential Next-Generation Nanocarriers for the Therapy of Inflammatory Diseases

Inflammatory diseases are common pathological processes caused by various acute and chronic factors, and some of them are autoimmune diseases. Exosomes are fundamental extracellular vesicles secreted by almost all cells, which contain a series of constituents, i.e., cytoskeletal and cytosolic proteins (actin, tubulin, and histones), nucleic acids (mRNA, miRNA, and DNA), lipids (diacylglycerophosphates, cholesterol, sphingomyelin, and ceramide), and other bioactive components (cytokines, signal transduction proteins, enzymes, antigen presentation and membrane transport/fusion molecules, and adhesion molecules). This review will be a synopsis of the knowledge on the contribution of exosomes from different cell sources as possible therapeutic agents against inflammation, focusing on several inflammatory diseases, neurological diseases, rheumatoid arthritis and osteoarthritis, intestinal bowel disease, asthma, and liver and kidney injuries. Current knowledge indicates that the role of exosomes in the therapy of inflammation and in inflammatory diseases could be distinctive. The main limitations to their clinical translation are still production, isolation, and storage. Additionally, there is an urgent need to personalize the treatments in terms of the selection of exosomes; their dosages and routes of administration; and a deeper knowledge about their biodistribution, type and incidence of adverse events, and long-term effects of exosomes. In conclusion, exosomes can be a very promising next-generation therapeutic option, superior to synthetic nanocarriers and cell therapy, and can represent a new strategy of effective, safe, versatile, and selective delivery systems in the future.