Frontiers in Cellular Neuroscience最新文献

Tight junctions form a paracellular barrier in epithelial and endothelial cells, and they regulate the diffusion of fluids, molecules, and the penetration of cells across tissue compartments. Tight junctions are composed of a group of integral membrane proteins, which include the claudin family, tight junction-associated Marvel protein family, junctional adhesion molecule family, and proteins that anchor the cytoskeleton, such as zonula occludens proteins and the cingulin family. Several factors, such as neurotransmitters or cytokines, and processes like ischemia/hypoxia, inflammation, tumorigenesis, phosphorylation/dephosphorylation, ubiquitination, and palmitoylation, regulate tight junction proteins. Claudins are involved in tumorigenesis processes that lead to glioma formation. In gliomas, there is a noticeable dysregulation of claudins, occludin, and zonula occludens-1 abundance, and their dislocation has been observed. The weakening of intercellular adhesion and cell detachment is responsible for glioma infiltration into surrounding tissues. Furthermore, the paracellular permeability of the blood-brain barrier, formed with the involvement of tight junction proteins, influences the development of peritumoral edema - and, simultaneously, the rate of drug delivery to the glial tumor. Understanding the junctional and paracellular environments in brain tumors is crucial to predicting glial tumor progression and the feasibility of chemotherapeutic drug delivery. This knowledge may also illuminate differences between high and low-grade gliomas.

Age-related hearing loss (ARHL) is a complex condition with genetic, aging, and environmental influences. Sirtuins, particularly SIRT1, are NAD-dependent protein deacetylases critical to aging and stress responses. SIRT1 is modulated by nicotinamide N-methyltransferase (NNMT) and its product, N¹-methylnicotinamide (MNAM), which influence ARHL progression. While SIRT1 is protective under certain conditions, its overexpression may paradoxically exacerbate hearing loss. This study examines MNAM supplementation's impact on SIRT1 expression and ARHL in low-fat diet (LFD)-fed B6 and CBA mice. Mice were divided into LFD and LFD + MNAM groups and evaluated for auditory function, cochlear morphology, metabolic profiles, and SIRT1 expression at 3, 6, and 12 months of age. MNAM supplementation accelerated ARHL in both strains, with B6 mice showing more pronounced and earlier disease progression. Auditory brainstem response (ABR) thresholds were significantly elevated, and distortion-product otoacoustic emissions (DPOAE) indicated outer hair cell dysfunction. Cochlear histology revealed reduced hair cell and spiral ganglion cell counts, as well as decreased Na⁺/K⁺-ATPase α1 expression and endocochlear potential. MNAM increased SIRT1 protein levels in the cochlea without altering Sirt1 mRNA, suggesting post-transcriptional regulation. Metabolomic analysis revealed disrupted mitochondrial and oxidative pathways, including fatty acid oxidation and gluconeogenesis. Tricarboxylic acid (TCA) cycle dysregulation was evident, particularly in B6 mice, with elevated pyruvate, fumarate, and lactate levels. Despite similar metabolic trends in CBA mice, their slower aging profiles mitigated ARHL progression. These results suggest that while moderate SIRT1 expression protects against ARHL, overexpression disrupts metabolic homeostasis, accelerating cochlear aging and dysfunction. The dual role of SIRT1 emphasizes the need for precise modulation of its expression for effective therapeutic interventions. Future research should explore mechanisms underlying SIRT1-induced cochlear damage and strategies to maintain balanced SIRT1 expression. This study highlights MNAM's detrimental effects on ARHL, underscoring its significance for developing targeted approaches to delay ARHL onset and preserve auditory function.

During sleep, several crucial processes for brain homeostasis occur, including the rearrangement of synaptic connections, which is essential for memory formation and updating. Sleep also facilitates the removal of neurotoxic waste products, the accumulation of which plays a key role in neurodegeneration. Various neural components and environmental factors regulate and influence the physiological transition between wakefulness and sleep. Disruptions in this complex system form the basis of sleep disorders, as commonly observed in synucleinopathies. Synucleinopathies are neurodegenerative disorders characterized by abnormal build-up of α-synuclein protein aggregates in the brain. This accumulation in different brain regions leads to a spectrum of clinical manifestations, including hypokinesia, cognitive impairment, psychiatric symptoms, and neurovegetative disturbances. Sleep disorders are highly prevalent in individuals with synucleinopathies, and they not only affect the overall well-being of patients but also directly contribute to disease severity and progression. Therefore, it is crucial to develop effective therapeutic strategies to improve sleep quality in these patients. Adequate sleep is vital for brain health, and the role of synucleinopathies in disrupting sleep patterns must be taken into account. In this context, it is essential to explore the role of physical exercise as a potential non-pharmacological intervention to manage sleep disorders in individuals with synucleinopathies. The current evidence on the efficacy of exercise programs to enhance sleep quality in this patient population is discussed.

In the mammalian cochlea, the transduction from vibrations to inner hair cell receptor currents is preceded by a stage of mechanical pre-processing that involves a rapid, strongly nonlinear compression. The mechanisms by which the cochlea realizes this dynamic compression are still poorly understood. Previous work by our group suggested that compression does not occur locally, but is realized by a cascade of weakly nonlinear elements along the cochlear partition. The resulting progressive accumulation of nonlinearity was termed the spatial buildup of compression. Here we studied mechanical compression in the basal turn of the sensitive gerbil cochlea using optical coherence tomography. We recorded vibrations at multiple positions along the length of the cochlear partition. Such longitudinal studies were virtually impossible with previous techniques. Using a tailored two-tone stimulus we quantified the spatial profile of compression. We found that the amount of compression grew gradually in an intensity-dependent fashion along our measurement stretch, as we moved apically toward the place of maximum vibration. This gradual buildup of compression was not mirrored by a gradual reduction beyond the peak. In fact the amount of compression accumulated even beyond the peak. This asymmetric pattern supports the view that mechanical compression is realized in a cascaded, distributed fashion which hinges on the traveling wave nature of cochlear vibrations.

Many retinal diseases are characterized by direct or indirect retinal ganglion cell (RGC) neurodegeneration. In glaucoma and optic nerve neuropathies, RGCs are the primary affected cells, whereas in photoreceptor dystrophies, RGC loss is secondary to the death of rods and cones. The death of RGCs in either case will irreversibly cause loss of vision, as RGCs are the sole output neurons of the retina. RGC neurodegeneration affects certain neurons preferentially, resulting in subpopulations of resilient and susceptible cells. Neurotrophins (NTs) are known to mediate neuronal survival through the downstream activation of various anti-apoptotic pathways. In this review, we summarize the current methods of RGC identification and quantification in animal models of direct or indirect neurodegeneration, and describe the advantages and disadvantages associated with these techniques. Using these techniques, multiple studies have uncovered the potential role of NTs in protecting RGCs during direct neurodegeneration, with BDNF and NGF delivery promoting RGC survival in models of experimental glaucoma. Many fewer studies have addressed similar questions in retinal diseases where RGC loss is secondary to photoreceptor degeneration, yielding conflicting results. Our analysis suggests that these seemingly contradictory results can be explained by the varying onset and geographic distribution of photoreceptor death.

Organotypic brain slices are three-dimensional, 150-μm-thick sections derived from postnatal day 10 mice that can be cultured for several weeks in vitro. However, these slices pose challenges for live-cell imaging due to their thickness, particularly without access to expensive two-photon microscopy. In this study, we present an innovative method to label and visualize specific brain cell populations in living slices. Using microcontact printing, antibodies are applied directly onto the slices in a controlled 400-μm-diameter pattern. Astrocytes are labeled with glial fibrillary acidic protein (GFAP), and vessels are labeled with laminin. Subsequently, slices are incubated with secondary fluorescent antibodies (green fluorescent Alexa-488 or red fluorescent Alexa-546) and visualized using an inverted fluorescence microscope. This approach offers a cost-effective and detailed visualization technique for astroglia and vessels in living brain slices, enabling investigation to be conducted over several weeks.

Variants in genes encoding for voltage-gated K⁺ (Kv) channels are frequent cause of drug-resistant pediatric epilepsies. Obtaining a molecular diagnosis gives the opportunity to assess the efficacy of pharmacological strategies based on in vitro features of mutant channels. In this retrospective observational study, we selected patients with drug-resistant pediatric epilepsies caused by variants in potassium channel encoding genes, followed at the Fondazione IRCCS Istituto Neurologico Carlo Besta of Milan, Italy. After the experimental characterization of variants' functional properties in transiently transfected Chinese Hamster Ovary (CHO) cells, we identified drugs to be used as pharmacological approaches. We recruited six patients carrying different missense variants in four Kv channels (Kv7.2, Kv7.3, Kv3.1, and K_Na1.1). In vitro experiments demonstrated that variants in Kv7 channels induced loss-of-function (LoF) effects, while those affecting Kv3.1 or K_Na1.1 led to gain-of-function (GoF). Moreover, we found that the Kv7 channels activator gabapentin was able to revert the LoF effects caused by Kv7.2/Kv7.3 variants, and the potassium channel-blocker fluoxetine counteracted the GoF effects in Kv3.1 or K_Na1.1 variants. According to experimental data, patients carrying Kv7 variants were treated with gabapentin. While this treatment resulted successful in two patients (#1, Kv7.2 G310S variant; #3, Kv7.3 V359L + Kv7.3 D542N), it resulted detrimental in the remaining case (#2, Kv7.2 D535E), requiring drug withdrawal. The application in vivo of fluoxetine to counteract GoF effects induced by Kv3.1 or K_Na1.1 variants determined a significant reduction of both seizure frequency and behavior disturbances in patient #4 (Kv3.1 V425M), and in both subjects carrying K_Na1.1 variants (#5, S937G and #6, R262Q). However, for the latter case, this drug was halted due to severe behavioral side effects. For most of the patients herein reported, pharmacological strategies, selected according to the in vitro functional properties of Kv-channels pathogenic variants, resulted in a significant improvement of both epileptic and cognitive features.

The transmembrane protein Synapse Differentiation Induced Gene 4 (SynDIG4), also known as Proline-rich transmembrane protein 1 (PRRT1), is an AMPA-type glutamate receptor (AMPAR) auxiliary factor that is necessary for maintaining extra-synaptic pools of GluA1. Loss of SynDIG4, and the subsequent decrease in extra-synaptic GluA1, has been found to significantly impact synaptic plasticity in the hippocampus. However, how SynDIG4 establishes and maintains these pools is unclear. Previous studies suggested that endocytic machinery is important for maintaining a pool of mobile surface AMPARs, and that proteins associated with such cellular machinery are critical for proper protein trafficking and internalization. Given that SynDIG4 co-localizes with GluA1 in early and recycling endosomes in cultured hippocampal neurons, we sought to identify the sorting signals that target SynDIG4 to endosomes to further elucidate the role of SynDIG4 in GluA1 trafficking. In this study, we report that SynDIG4 possesses a YxxΦ sorting motif, 178-YVPV-181, responsible for binding to the AP-2 complex cargo-sorting subunit μ2. This motif appears critical for proper SynDIG4 internalization, as SynDIG4 mutant 178-AVPA-181, which disrupts binding to μ2, induces aberrant SynDIG4 accumulation at the plasma-membrane of heterologous cells and primary rat hippocampal neurons. We also show that SynDIG4 mutants lacking an endocytic signal co-localize with GluA1 but less so with GluA2 on the surface of heterologous cells. Furthermore, we show that another family member, SynDIG1, is enriched in the trans-Golgi network (TGN) and can traffic between the TGN and plasma membrane. We have identified a non-canonical μ2 binding sequence in SynDIG1 that induces aberrant accumulation at the plasma membrane of heterologous cells and primary rat hippocampal neurons, suggesting a conserved role for μ2-mediated endocytosis within the SynDIG family. These results provide important insight into the mechanisms by which SynDIG proteins are targeted to endosomal compartments as a step in understanding SynDIG-mediated regulation of AMPAR trafficking.

Understanding cortical inhibition and its diverse roles remains a key challenge in neurophysiological research. Traditionally, inhibition has been recognized for controlling the stability and rhythmicity of network dynamics, or refining the spatiotemporal properties of cortical representations. In this perspective, we propose that specific types of interneurons may play a complementary role, by modulating the computational properties of neural networks. We review experimental and theoretical evidence, mainly from rodent sensory cortices, that supports this view. Additionally, we explore how dysfunctions in these interneurons may disrupt the network's ability to switch between computational modes, impacting the flexibility of cortical processing and potentially contributing to various neurodevelopmental and psychiatric disorders.