Ketone bodies are a major source of cerebral energy during fasting and the ketogenic diet, but whether they can sustain brain tissue metabolism when glucose is absent remains uncertain. This question is difficult to resolve in vivo because circulating glucose is maintained, even during starvation, through endogenous production. We therefore used an ex vivo brain preparation to examine the metabolic capacity of tissue following incubation with β-hydroxybutyrate (BHB) as the only exogenous fuel, isolating brain tissue from its primary endogenous glucose sources. Mitochondrial respiration was monitored following 4-hour incubation in glucose-free, BHB-rich artificial cerebrospinal fluid, and tissue resilience was tested by inducing spreading depolarization, a severe energetic challenge that requires rapid restoration of ionic and metabolic homeostasis. Following acute reliance on exogenous BHB, in addition to endogenous energy reserves, mitochondrial electron transfer system function persisted, with lower O2 flux than following incubation with exogenous glucose. BHB-supported tissue maintained sufficient energetic capacity to generate and recover from repeated spreading depolarizations. In contrast, tissue relying solely on endogenous energy reserves failed to undergo repeated spreading depolarizations, suggesting that exogenous BHB provided the needed short-term energetic support beyond that available from endogenous substrates in the complete absence of exogenous glucose. The results broaden our understanding of cerebral fuel flexibility and provide evidence that BHB can support highly energetic neural function in the absence of exogenous glucose.

Dementia is clinically and biologically heterogeneous, and genetically supported plasma protein associations across dementia subtypes remain incompletely characterized. We aimed to genetically prioritize plasma proteins associated with overall dementia and major dementia subtypes using proteome-wide Mendelian randomization (MR) and Bayesian colocalization. We used the UK Biobank Pharma Proteomics Project (UKB-PPP) as a harmonized source of cis-protein quantitative trait loci (cis-pQTLs) for 2,941 Olink-measured plasma analytes. The European-ancestry discovery cis-pQTL analysis included up to 34,557 participants, whereas 54,219 participants were profiled in the overall UKB-PPP. Outcomes included FinnGen R10 genome-wide association studies (GWAS) for dementia, Alzheimer's dementia, vascular dementia, frontotemporal dementia, and unspecified dementia, plus a European GWAS for dementia with Lewy bodies. At the nominal threshold of P < 0.05, 134, 132, 102, 78, 101, and 112 exploratory protein-outcome signals were observed for dementia, Alzheimer's dementia, vascular dementia, frontotemporal dementia, dementia with Lewy bodies, and unspecified dementia, respectively; 23 associations remained significant after outcome-specific Benjamini-Hochberg false discovery rate (FDR) correction. Key FDR-significant proteins included APOE, NECTIN2, PVR, SERPINF2, GRN, TREM2, and ATXN2L. The strongest risk and protective associations were NECTIN2 with Alzheimer's dementia (odds ratio [OR] = 2.650, 95% confidence interval [CI]: 1.875-3.744, FDR-adjusted P = 1.58 × 10[- 5]) and ATXN2L with dementia (OR = 0.408, 95% CI: 0.255-0.654, FDR-adjusted P = 0.0370), respectively. Strong colocalization support was observed for selected SERPINF2 and TREM2 associations. These findings genetically prioritize several plasma proteins as candidate biomarkers and potential therapeutic targets across dementia subtypes, but do not establish that circulating protein abundance directly mediates dementia risk.

One of the major challenges in neuroscience is understanding how the human brain develops into a highly organized and functionally integrated organ, because many developmental processes cannot be investigated directly in humans and are not fully recapitulated in animal models. Brain organoids derived from human pluripotent stem cells have emerged as powerful three-dimensional (3D) experimental models that recapitulate key features of human neurodevelopment, including regional patterning, cellular diversification, and neural circuit assembly. Recent advances in long-term organoid culture, organoid bioengineering, vascularization, assembloid technology, transplantation, multi-omics, and artificial intelligence have substantially expanded the applications of brain organoids to investigate human neurodevelopment, model neurological disorders, support drug discovery, and advance therapeutic development. Integration of single-cell and spatial multi-omics with computational approaches has enabled robust molecular benchmarking, assessment of developmental fidelity, and evaluation of organoid reproducibility, facilitating direct comparison with primary human fetal brain tissue. However, current organoid systems remain limited owing to incomplete cellular and tissue complexity, inter-organoid variability, limited vascularization, limited functional maturation, and incomplete physiological integration. Continued advances in tissue engineering, computational biology, and standardized differentiation protocols are expected to enhance the biological fidelity and translational utility of brain organoids for basic and translational neuroscience, as well as mechanistic and translational research.

Mitochondria integrate metabolic, signalling, and quality-control pathways that are critical for neuronal and glial homeostasis. Beyond ATP production, they regulate redox balance, calcium dynamics, proteostasis, innate immune signalling, and the molecular pathways governing cell survival and death. This Closing Editorial synthesizes the main advances reported in this Collection across neurodegeneration, neurodevelopmental vulnerability, inherited mitochondrial disorders, neurotrauma, drug-induced neurotoxicity, and neuroimmune regulation. Collectively, these studies establish mitochondrial dysfunction as a heterogeneous and context-dependent process rather than a uniform or secondary consequence of neurological disease. Mitochondrial alterations are dynamically regulated across cell types, subcellular compartments, and disease stages, and are tightly coupled to inter-organelle communication and cellular stress-response pathways. The contributions highlight convergent mechanisms linking astrocytic mitochondrial DNA damage, dysregulated RNA-binding proteins, altered mitochondria-endoplasmic reticulum contacts, disrupted iron and redox homeostasis, and mitochondrial-inflammatory signalling to neuronal vulnerability and impaired circuit integrity. They also identify potential therapeutic targets while defining key unresolved questions, particularly the need to establish mechanistic causality, delineate cell- and compartment-specific mitochondrial responses, and validate findings using clinically relevant models and outcome measures. Overall, this Collection positions mitochondrial biology as a mechanistic framework connecting metabolic dysfunction, cellular stress, neuroinflammation, and neuronal degeneration, and supports its development as a therapeutic target for disease-modifying interventions in neurological disorders.

The targeted differentiation of stem cell-like cells into functional neurons is a central goal in developmental biology and comparative neurobiology. In this study, we report for the first time on the successful neuronal remodeling of cell line derived from the Atlantic sturgeon larvae (Acipenser oxyrinchus; AOXlar7y) under defined in vitro conditions. The cells were cultured on poly-D-lysine-coated surfaces and exposed to a reduced-serum medium supplemented with nerve growth factor-β to induce neuronal differentiation. Morphologically, time-dependent formation of neurite-like processes and network structures was observed over a period of 14 days. The neuronal identity of the differentiated cells was confirmed by immunocytochemistry with the neuronal marker NeuN. Functional maturation was examined by measurement of cytoplasmatic calcium activity. After stimulation with 200 µM ATP, cells with neuronal morphology showed distinct intracellular calcium transients, indicating functional purinergic signaling pathways. AOXlar7y thus represents a novel in vitro model for studying neurogenesis and neuronal function in a cellular model of ancient fish species and provides a valuable basis for future studies in comparative neurobiology, neurotoxicology, and evolutionary developmental biology.

Peripheral nerve injury (PNI) disrupts nerve function, there has been increasing focus on the role of macrophages in PNI. This study provides a comprehensive analysis of research trends and key topics related to macrophages in the field of PNI. We conducted a search in the Web of Science Core Collection database for studies published between 2000 and 2023 using "macrophages" and "PNI" as keywords. Bibliometric analysis was performed using visualization tools, including VOSviewer, CiteSpace, and GraphPad Prism 8, and others. As of December 31, 2023, a total of 905 relevant publications were identified. In terms of author contributions, Japanese researchers Kiguchi Norikazu and Kishioka Shiroh shared the highest number of publications, each with 15 articles. In terms of journals, Experimental Neurology published the most articles, while the University of Würzburg in Germany emerged as the leading institution in this field, with the highest publication output. Among the 51 countries involved in this research, the United States ranked first, followed by China. The keyword 'exosomes' first appeared in 2021, making it the most recent keyword. Cluster analysis categorized the keywords into four main groups: the role of macrophages in Wallerian degeneration, the role of macrophages in pathological peripheral neuropathic pain, macrophage-derived products after PNI, and role of macrophages in PNI repair and strategies for modulating their function using biomaterials. Macrophages are increasingly crucial in PNI research, and future studies integrating novel approaches may yield innovative therapies for nerve repair.

Alzheimer's disease (AD) is a neurodegenerative disorder characterised by progressive dementia, brain atrophy, and ultimately death. Using cerebral organoids derived from human-induced pluripotent stem cells (hiPSCs) carrying the familial PSEN1 A246E variant, we investigated the temporal relationship between amyloid-β (Aβ) dysregulation and spontaneous neuronal activity. Multielectrode array recordings from the differentiation day 60 (DD60) to at least DD130 revealed that AD organoids exhibited transient hyperexcitability and hypersynchrony compared with wild-type (WT) controls, followed by a gradual decline in activity. During the enhanced excitability stage, both elevated Aβ42/40 and Aβ aggregate size showed positive correlations with the percentage of active electrodes and the global synchrony index (GSI) in AD organoids. These findings indicate that Aβ dysregulation might contribute to transient network hyperexcitability in early AD. The results also suggest that patient-derived cerebral organoids may serve as a translational model to examine early network dysfunction and inform future investigations of potential Aβ-induced changes in excitability during the preclinical stages of AD.

Fumaric acid esters have proven to be effective medications in relapsing-remitting multiple sclerosis with neuroprotective effects. In this study, we investigated the impact of fumaric acid esters on primary murine microglia in vitro compared to DMSO vehicle control. Monomethyl fumarate (MMF) increased MTT reduction in a dose-dependent manner, whereas dimethyl fumarate (DMF) exhibited a biphasic response with low concentrations enhancing MTT reduction and higher concentrations inducing toxicity. Notably, complementary analyses of cell number and cell death did not reveal differences between MMF-treated and control conditions, indicating that the increased MTT reduction reflects enhanced cellular metabolic activity rather than increased viability. Consistent with this interpretation, MMF-treated cells exhibited higher basal and maximal oxygen consumption, spare respiratory capacity, and ATP production in the Seahorse XF Cell Mito Stress Test. Proteomic analysis did not indicate an upregulation of mitochondrial respiratory chain proteins, but instead suggested a qualitative shift in mitochondrial homeostasis, including increased expression of mitophagy-associated proteins. MMF-treated Nrf2-deficient microglia showed a blunted increase in MTT reduction, suggesting an involvement of Nrf2 in mediating MMF-induced metabolic effects. Additionally, MMF modulated the microglial iron metabolism and reduced the uptake of non-transferrin-bound iron and altered the gene expression of iron transport proteins, promoting a shift toward the uptake of less toxic, transferrin-bound iron. MMF mitigated iron-induced toxicity and was associated with upregulation of the ferroptosis suppressor protein, indicating a protective response to iron overload. Together, these findings suggest that MMF enhances microglial metabolic activity and mitochondrial function while reducing iron-mediated toxicity, thereby contributing to its neuroprotective effects.

Mitochondrial dysfunction has been recognized as one of the three hallmark biological features of autism spectrum disorder. This study is intended to investigate the molecular mechanisms underlying prenatal psychological fear stress‑induced hippocampal mitochondrial damage in offspring. Bioinformatics analysis revealed that the calcium signaling pathway, particularly the phospholipase C beta 1(PLCβ1)- inositol 1,4,5‑trisphosphate receptor (IP3R)- voltage‑dependent anion channel 1(VDAC1) pathway, may play a key role in prenatal stress‑induced hippocampal mitochondrial damage in offspring. To validate this, we examined pathway activation in the offspring hippocampus of prenatal fear stressed rats and in corticotropin-releasing hormone (CRH; also known as CRF in rodents) overexposed SH‑SY5Y cells, along with mitochondrial calcium levels in the cells. Prenatal fear stress induced depressive-like behavior and HPA axis activation in pregnant dams, and reduced survival and growth in offspring. Placental and neonatal brain CRF levels were elevated. At the early socialization stage (Postnatal day 21-30), model offspring showed normal basal but exaggerated stress-induced HPA responses. Their hippocampus exhibited expanded MAM coverage, reduced ER-mitochondria distance, and upregulated PLCβ1, IP3R1, VDAC1 expression, along with increased GRP75‑VDAC1 co‑localization, confirming MAM remodeling at the molecular level. In vitro, CRH (20 µM for 48 h or 5-20 µM for 96 h) inhibited SH-SY5Y cell proliferation, upregulated CRH receptor 1(CRHR1), PLCβ1, VDAC1, and increased mitochondrial calcium; these effects were reversed by the CRHR1 antagonist CP376395 or PLCβ1 knockdown. Furthermore, the MCU inhibitor DS16570511 partially reversed CRH‑induced mitochondrial calcium elevation and proliferation inhibition, suggesting that mitochondrial calcium overload contributes to the proliferation inhibition. Collectively, these results suggest that prenatal fear stress may, via the CRF-CRFR1 axis, influence the PLCβ1-IP3R-VDAC1 pathway, inducing MAM remodeling and mitochondrial calcium overload, thereby contributing to offspring hippocampal neuronal damage.

Early-life nutrition is increasingly recognized as a key determinant of brain developmental trajectories. Because the dorsal (dHIP) and ventral (vHIP) hippocampus regulate distinct cognitive and emotional functions, understanding how maternal diet shapes maturation along this axis may provide insight into later behavioral vulnerability. However, the impact of maternal diet on the spatial organization of hippocampal maturation along the dorsal-ventral axis remains unclear. Here, we tested whether maternal isocaloric monosaccharide diets containing glucose (GLU) or fructose (FRU) are associated with age-, sex-, and region-dependent molecular remodeling along the dorsal-ventral axis of the hippocampus. In an established Wistar rat cohort, we quantified mRNA expression of genes associated with neuronal maturation and plasticity (Bdnf, Dcx, Gfap, Nes, Rbfox3) and protein levels of DCX, GFAP, and NeuN in the dHIP and vHIP of dams and male and female offspring during adolescence (PND28) and young adulthood (PND63). In dams, FRU exposure was associated with modestly increased Bdnf expression, and both GLU and FRU diets were associated with region-dependent differences in DCX, GFAP, and NeuN protein levels. In offspring, perinatal exposure to GLU or FRU diets induced sex-dependent patterns of hippocampal gene expression. Diet-related molecular differences were more prominent in the dHIP during adolescence, whereas additional vHIP-associated alterations emerged in young adulthood. Several proteins exhibited region-dependent differences, with the vHIP generally displaying higher protein abundance, although diet-induced alterations differed between hippocampal subregions. Guided by PCA and a composite RNA-protein molecular index highlighting persistent molecular remodeling within the vHIP, subsequent analyses focused on the vHIP in male offspring. Targeted analysis of the male vHIP at PND63 revealed that maternal FRU exposure was associated with increased Mc4r expression and elevated MC4R protein levels, whereas both maternal GLU and FRU exposure were associated with increased ARC protein levels. In contrast, maternal monosaccharide exposure was associated with reduced Npas4 expression, and maternal FRU exposure was additionally associated with reduced NPAS4 protein levels. Collectively, maternal monosaccharide diets were associated with age-, sex-, and region-dependent remodeling of hippocampal maturation- and plasticity-related molecular profiles. Subsequent analyses identified persistent alterations in MC4R-, ARC-, and NPAS4-related molecular profiles in the young adult male vHIP.

The present study aimed to investigate MR-based evidence for potential causal relationships between circulating leukocytes, immune cell traits, and multiple sclerosis (MS) using a two-sample, bidirectional Mendelian randomisation (MR) approach. We analysed summary-level data from large-scale genome-wide association studies conducted by the International Multiple Sclerosis Genetics Consortium, the Blood Cell Consortium, and Immune Cell traits. Using inverse variance weighted (IVW), weighted mode, weighted median, simple mode, and MR-Egger methods, we estimated genetically predicted associations. The MR-Egger intercept assessed horizontal pleiotropy, Cochran's Q test examined genetic heterogeneity, and leave-one-out procedures evaluated the sensitivity of the results. We adjusted for multiple comparisons using the false discovery rate (FDR). Forward MR analysis using IVW as the primary method revealed associations between increased white blood cell count (OR = 1.16, 95% CI = 1.05-1.29, P = 0.004, PFDR = 0.031) and lymphocyte count (OR = 1.18, 95% CI = 1.06-1.31, P = 0.003, PFDR = 0.035) with a higher risk of developing MS. Conversely, the CD25hi CD45RA-CD4 not Treg %CD4+ (OR = 0.87, 95% CI = 0.808-0.942, P = 0.0005, PFDR = 0.075) and the CD16-CD56 on HLA DR+ NK (OR = 0.85, 95% CI = 0.780-0.935, P = 0.0007, PFDR = 0.093) were associated with a reduced risk of MS. In reverse MR analyses, MS showed no robust evidence of a causal effect on white blood cell or lymphocyte counts. Although an FDR-significant reverse association was observed for the IgD+ CD38 + B-cell absolute count subtype, leave-one-out sensitivity analysis indicated instability. Therefore, this finding was not considered reliable evidence of reverse causality. Genetic predisposition to increased white blood cell and lymphocyte counts elevates the risk of MS, while certain immune cell traits may reduce this risk.

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disorder characterized by motoneurons degeneration. Functional studies have linked ALS to hyperexcitability and excitotoxicity, but the cause of the disease is unknown, though familial ALS cases are linked to pathogenic variants in several genes, including SOD1, TARDBP and FUS. Here we focused on the effect of the severe FUS (P525L) mutation on the functional properties of human spinal neurons derived from induced pluripotent stem cells (hiPSCs). This mutation delayed functional maturation, as revealed by the observation that mutated neurons showed alterations of membrane potential, reduced spontaneous synaptic activity, and altered action potentials at early differentiation stages. FUS (P525L) mutation was associated with a significant alteration of inhibitory signalling transmission: mutated neurons showed a significantly lower current response to GABA and glycine compared to control isogenic WT neurons of the same age. Also, glutamatergic currents exhibited a different temporal evolution in control and mutated neurons, but at a lower extent in comparison to inhibitory neurotransmitters. The decrease in the glycine-evoked currents was confirmed by the reduction of the expression of the α1 subunit of glycine receptor, measured by immunofluorescence assay. Similar functional alterations were measured in spinal neurons differentiated form a second hiPSC line, confirming the causative role of the FUS (P525L) mutation. Our data indicate that the FUS (P525L) mutation reduces the maturation rates and the function of hiPSC-derived spinal neurons, with a strong decrease of inhibitory transmission, which may affect the excitatory/inhibitory balance, possibly predisposing to excitotoxicity and neurodegeneration.

Glial cells, namely microglia, astrocytes, and oligodendrocytes, play crucial roles in maintaining homeostasis in the central nervous system and orchestrating responses to injury, infection, and disease. Among the molecular regulators of glial function, cysteine cathepsins have emerged as key modulators of both physiological and pathological processes. These lysosomal peptidases are traditionally known for their housekeeping roles in protein degradation; however, accumulating evidence highlights their broader involvement in antigen presentation, microglial and astrocyte reactivity, inflammatory signalling, apoptosis, and myelination. Under normal conditions, cysteine cathepsins support essential functions in the central nervous system, including immune surveillance and tissue remodelling. Conversely, their dysregulation, characterized by overexpression, increased enzymatic activity, or mislocalization, can promote neuroinflammation and neurodegeneration, contributing to the pathogenesis of disorders such as Alzheimer's disease and multiple sclerosis. This review provides a comprehensive synthesis specifically focused on the diverse roles of cysteine cathepsins across major glial cell types, systematically summarizing current knowledge in microglia, astrocytes, and oligodendrocytes. We emphasize their cell type-specific, context-dependent, protective, and deleterious functions. Furthermore, we discuss mechanistic links between cysteine cathepsin activity and neurodegenerative processes and evaluate the therapeutic potential and current limitations of selectively targeting glial cysteine cathepsins. A deeper understanding of the context-dependent dual roles of these enzymes in brain physiology and pathology is critical for designing targeted interventions that could mitigate neuroinflammation and neurodegeneration.

Fingolimod (FNG) is a sphingosine-1-phosphate receptor agonist currently prescribed for the treatment of remitting-relapsing multiple sclerosis. However, an increasing body of evidence indicates that FNG has a variety of other effects on the central nervous system, making it a good candidate to target other brain disorders that display loss of neuronal cells and synaptic plasticity. FNG treatments induce production of brain-derived neurotrophic factor (BDNF), which promotes neuronal plasticity, arborization and survival via signaling through its cognate receptor TRKB. In this study we characterize the relationship between FNG and TRKB in vitro and in vivo following acute treatments. We found that FNG induces TRKB activation in primary neuronal cultures in a BDNF-dependent way, indicating a rapid effect of FNG. This effect is different from the one elicited by antidepressants and is likely mediated by modulation of plasma membrane properties, as the enhancement of fluoxetine binding and dimerization of the cholesterol-insensitive TRKB mutant Y433F mimic the effects of cholesterol. Moreover, acute FNG treatment normalizes the generalization of conditioned fear response seen in heterozygous BDNF null female mice without affecting the wild-type littermates. Taken together, our data indicate that FNG allosterically promotes TRKB signaling and thereby induces the increase in BDNF production, which mediates the therapeutic effects of the drug on neuronal plasticity.

Neuronal differentiation is a highly regulated process in which morphogens establish cellular identities through coordinated transcriptional programs. However, the contribution of physiologically derived metabolites to human neural development remains poorly understood. β-hydroxybutyrate (bhb) has been recognized as an inflammatory, epigenetic, energetic, and neuroprotective regulator. We differentiated midbrain floor plate neural precursor cells (mfNPC) from human embryonic stem cells to generate midbrain organoids (MBOs), which were exposed to bhb. Although dopaminergic differentiation occurred in control MBOs, treatment with 1 mM bhb for 16 days significantly increased both the number of Tyrosine hydroxylase-positive (TH[+]) neurons, and the corresponding transcripts assessed by bulk RNA sequencing. Such transcriptomic profiling revealed modest but consistent bhb-associated changes in trophic, neuronal and dopaminergic transcripts. To further characterize these changes, we performed gene set enrichment analysis using curated cell phenotypes-associated transcriptional programs. These analyses indicated that bhb treatment is associated with shifts in the enrichment scores of dopaminergic programs in day 16 MBOs. At the epigenomic level, we used CUT&RUN assays to map H3K27 acetylation, and the selected candidates H3K27ac regions after bhb treatment were linked to their closest neighboring genes, suggesting positive enrichment of neural and dopaminergic gene ontology categories at both time points. Unsupervised analysis of H3K27ac-enriched regions revealed three major clusters detected across differentiation, although present in both control and bhb-treated MBOs. Motif enrichment analysis of clustering regions identified distinct predicted transcription factor binding motifs in mfNPC and MBOs. Finally, we integrated this motif analysis, enhancer annotation, and our transcriptomic data on a web platform, Enhancer Network Explorer, to explore relationships between H3K27ac profiles, transcriptional changes and bhb exposure during human MBOs differentiation. Together, our results indicate that bhb treatment is associated with increased TH-positive cell abundance and with population-level changes related to neurodevelopmental transcriptional programs. These findings suggest that bhb might support early human midbrain differentiation and provide a starting point for future studies addressing the mechanisms linking metabolic cues, chromatin-associated regulation and dopaminergic differentiation.