Shandilya MCV, Koutures A, Addo-Osafo K
… +18 more, Hwang K, Vicente M, Ewens AN, Katz BM, Peters ST, Choquette JM, Vaknalli RN, Venkateswaran N, Onanyan N, Narasani A, Ravishankar S, Stepter J, Western A, Benneyworth MA, Cohn W, John V, Whitelegge JP, Vossel K
Alzheimer's disease (AD) patients frequently experience seizures, sleep disturbances, and other forms of neural network dysfunction that accelerate cognitive decline. Although tau-lowering therapies may alleviate these f...Alzheimer's disease (AD) patients frequently experience seizures, sleep disturbances, and other forms of neural network dysfunction that accelerate cognitive decline. Although tau-lowering therapies may alleviate these features, they also risk disrupting essential physiological functions of tau, leading to motor impairments. We hypothesized that targeted mutations within tau's proline-rich domain-regions critical for binding SH3-containing proteins implicated in seizures and excitotoxicity-could selectively disrupt pathological interactions while preserving normal cognition and behaviour. To test this, we generated two tau knockin mouse lines: AxxA6, carrying proline-to-alanine mutations in the sixth PxxP motif, and R221A, containing an arginine-to-alanine substitution at residue 221. Tau-protein interactions were evaluated using proximity ligation assays in cultured hippocampal neurons and co-immunoprecipitation-mass spectrometry of cortical lysates. To model epilepsy, Kv1.1 heterozygous knockout mice were crossed with tau knockin mice. Mice underwent 24-hour cortical EEG recordings. Seizure susceptibility was assessed following intraperitoneal kainic acid (25 mg/kg). Hippocampal slice electrophysiology was used to measure epileptic bursting after picrotoxin/4-AP application. Comprehensive motor and cognitive testing were performed in AxxA6 and R221A lines at young and older ages. Both variants reduced tau's binding to the SH3-containing proteins BIN1, PLCγ1, and p85⍺/PI3K, with AxxA6 specifically decreasing Fyn interaction (P < 0.0001). Coimmunoprecipitation-mass spectrometry revealed variant-specific alterations in tau interactomes, including increased synaptotagmin-5 binding in both lines (P < 0.05). AxxA6 knockin mice displayed unique resistance to kainic-acid-induced seizures. AxxA6 knockin also reduced epileptic spike rates in Kv1.1-/- mice (P = 0.02), along with improved beta power during REM (P < 0.05), and rescued sleep disruptions (P < 0.002). Both AxxA6 and R221A prevented the increase in epileptiform bursting in Kv1.1-/- hippocampal slices after picrotoxin/4-AP (P < 0.05) and improved survival in Kv1.1-/- mice. Motor function, cognition, and body weight were preserved in both lines across ageing (3-7 and 14-18 months), in contrast to age-related weight gain and motor deficits in tau knockout mice. These findings demonstrate that precision targeting of tau's sixth PxxP motif can selectively disrupt pathological protein interactions while preserving physiological function, offering a promising therapeutic strategy to mitigate tau-driven neuronal and network dysfunction without compromising cognitive or motor health.
Schizophrenia is a common and often disabling neuropsychiatric condition. Whilst sensorimotor abnormalities such as dyskinesia, parkinsonism and motor incoordination are prevalent in schizophrenia, they are often attribu...Schizophrenia is a common and often disabling neuropsychiatric condition. Whilst sensorimotor abnormalities such as dyskinesia, parkinsonism and motor incoordination are prevalent in schizophrenia, they are often attributed to medication side-effects or classified as neurological soft signs or catatonic phenomena. Here, we outline the prevalence, characteristics and challenges in accurate phenotyping of sensorimotor disturbances in schizophrenia, including amongst medication naïve individuals, demonstrating that sensorimotor dysfunction may be an integral manifestation of the disease process. We then review how current understanding regarding the pathogenesis of schizophrenia supports this possibility and consider how better characterisation of sensorimotor dysfunction may improve management and the development of novel treatments for schizophrenia, playing particular attention to the role of instrumental sensorimotor assessment.
Memories are thought to be encoded in synaptic connections between assemblies of neurons that are reactivated during memory recall. However, in light of ongoing molecular turnover and synaptic decay, this widely accepted...Memories are thought to be encoded in synaptic connections between assemblies of neurons that are reactivated during memory recall. However, in light of ongoing molecular turnover and synaptic decay, this widely accepted view cannot explain how individual ensembles are maintained over (life-)long timescales. Experimentally, learning has not only been associated with synaptic modifications among neurons, but also with epigenetic alterations of learning-related gene transcription within neurons. Although these epigenetic changes are involved in all stages of memory dynamics, they have been largely omitted in computational studies. In this update, we advocate for the integration of epigenetic mechanisms into computational models of memory. Using a recurrent neural network model that includes epigenetic plasticity as a variable, we explore the role of epigenetic priming in the maintenance of memories across long timescales; we then investigate the implications of epigenetic modifications for memory allocation and for reversing cognitive decline associated with neurodegeneration; and finally, we predict several computational advantages of including epigenetics over traditional models of synaptic memory. Overall, this paper stands as a first step towards the integration of epigenetics in computational models of memory and corroborates the experimentally derived notion that memory might not be encoded solely in synaptic weights, but rather co-encoded in epigenetic patterns within the nucleus.
Chrysostomidou P, Hore Z, Somma D
… +9 more, Vlachaki Walker JM, Diallo K, Titterton HF, Elmesmari A, Schino L, Adesida S, Kurowska-Stolarska M, Denk F, Weir GA
Neuropathic pain is a highly prevalent condition for which treatments are hampered by low efficacy and dose-limiting side-effects. Injury to the somatosensory nervous system causes maladaptive plasticity that initiates a...Neuropathic pain is a highly prevalent condition for which treatments are hampered by low efficacy and dose-limiting side-effects. Injury to the somatosensory nervous system causes maladaptive plasticity that initiates and maintains chronic pain. Emerging evidence suggests that inflammatory cells of the innate immune system shape the response of the injured nervous system and thereby contribute to the pathogenesis of pain. Data from preclinical models and human patient biopsies have specifically implicated peripheral macrophage populations for a pro-algesic role, yet how these cell types influence damaged sensory neurons and whether they directly contribute to neuronal hyperexcitability is unclear. Here, we have developed an iPSC co-culture system to study the interactions of macrophages and sensory neurons in a fully humanised experimental model. We found that analogous to endogenous counterparts, iPSC-derived macrophages (iMacs) display a dynamic molecular and functional profile that is highly dependent on neuronal state. Co-culture with injured iPSC-derived sensory neurons (iSNs) induces morphological, gene expression, and secretory profile changes in iMacs that are consistent with the response of macrophages to nerve injury in vivo. iMacs in turn amplify spontaneous firing in damaged sensory neurons, implicating macrophages in this cardinal feature of neuropathic pain. These results illustrate the utility of an iPSC-based model to study signalling between these two cell types; they support a role for macrophages in directly amplifying damaged sensory neuron activity and highlight disrupting pathological signalling between these cell types as a promising strategy for future analgesic drug development.
The diagnosis of progressive supranuclear palsy (PSP) remains challenging, particularly in differentiating it from Parkinson's disease (PD) at early stages. Circulating neuron-derived extracellular vesicles (NDEVs) provi...The diagnosis of progressive supranuclear palsy (PSP) remains challenging, particularly in differentiating it from Parkinson's disease (PD) at early stages. Circulating neuron-derived extracellular vesicles (NDEVs) providing a peripheral window into central nervous system pathology may serve as promising biomarkers. A total of 188 participants were recruited from 3 centers. A discovery cohort (40 PSP patients, 36 PD patients, and 31 healthy controls [HCs]) and a multicenter validation cohort (30 PSP patients, 27 PD patients, and 24 HCs) were established. NDEVs containing total tau, 4R tau, phosphorylated tau (ptau181, ptau217, ptau231 and ptau396) in plasma samples were analyzed using nano-scale flow cytometry. Multivariable logistic regression models were developed in the discovery cohort and strictly validated in the independent cohort using fixed model parameters. In the discovery cohort, the concentrations of tau, 4R tau, ptau181, and ptau217-containing NDEVs in PSP patients were significantly higher than those in HCs and PD patients, while ptau396-containing NDEVs showed elevation exclusively in PSP compared to HCs. (PSP vs. HCs: P<0.001 for tau, P<0.001 for 4R tau, P<0.001 for ptau181, P=0.008 for ptau217, P=0.009 for ptau396; PSP vs. PD: P<0.001 for tau, P<0.001for4R tau, P=0.029 for ptau181, P=0.003 for ptau217). An integrated model incorporating these biomarkers achieved an area under the curve (AUC) of 0.965 (90.0% sensitivity, 96.8% specificity) for distinguishing PSP from HCs, and an AUC of 0.963 (87.5% sensitivity, 94.4% specificity) for distinguishing PSP from PD. In the validation cohort, the concentrations of tau, 4R tau, ptau181, ptau217, and ptau396-containing NDEVs in plasma were significantly higher in PSP patients compared to HCs (PSP vs. HCs: P<0.001 for tau, 4R tau, and ptau217, P=0.03 for ptau181, P=0.017 for ptau396). Similarly, the concentrations of tau, 4R tau, ptau181, and ptau217 were higher in PSP patients than in PD patients (PSP vs. PD: P<0.001 for tau, 4R tau, and ptau217, P=0.025 for ptau181). The integrated model yielded an AUC of 0.971 for distinguishing PSP from HCs and 0.990 for distinguishing PSP from PD. Notably, in early-stage patients, the integrated model achieved an AUC of 0.987 in differentiating early-stage PSP from PD. These findings indicate that plasma tau-species-containing NDEVs are promising biomarkers for PSP, offering high sensitivity and specificity for distinguishing PSP from both HCs and PD, particularly in early disease stages. Further large-scale, longitudinal studies are warranted to fully validate these findings and explore their role in PSP pathophysiology and progression.
Lee J, Cho Y, Choi BY
… +15 more, Kim HK, Lee Y, Kim E, Han J, Sul JH, Kim JS, Baek SH, Cho Y, Park J, Bahn G, Bae HG, Jun JH, Lai MKP, Arumugam TV, Jo DG
Alzheimer's disease (AD) is marked by amyloid-β (Aβ) accumulation, tau pathology, and neuroinflammation. The β-site APP cleaving enzyme 1 (BACE1) is a key driver of Aβ production, while the NLRP3 inflammasome mediates mi...Alzheimer's disease (AD) is marked by amyloid-β (Aβ) accumulation, tau pathology, and neuroinflammation. The β-site APP cleaving enzyme 1 (BACE1) is a key driver of Aβ production, while the NLRP3 inflammasome mediates microglial inflammatory responses. Histone deacetylase 6 (HDAC6), a cytoplasmic deacetylase, is upregulated in AD, yet its role in disease mechanisms remains unclear. Here, we show that HDAC6 promotes BACE1 protein stability through direct deacetylation of its C-terminal lysine (K501), thereby increasing Aβ production. HDAC6 also facilitated NLRP3 inflammasome activation in microglia, increasing IL-1β production in a catalytic domain-dependent manner. HDAC6 deficiency in 5xFAD mice reduced BACE1 accumulation, Aβ deposition, ASC speck formation, and IL-1β levels, accompanied by improved cognitive performance. Transcriptomic profiling further revealed downregulation of disease-associated microglial and neurotoxic astrocyte signatures alongside enrichment of synaptic pathways. These findings establish HDAC6 as a dual regulator of Aβ production and neuroinflammation, highlighting it as a promising therapeutic target in AD.
Focal cortical dysplasia type II (FCDII), a major cause of pediatric drug-resistant focal epilepsy, results from brain somatic variants in mTOR pathway genes, including germline and somatic second-hit loss-of-function va...Focal cortical dysplasia type II (FCDII), a major cause of pediatric drug-resistant focal epilepsy, results from brain somatic variants in mTOR pathway genes, including germline and somatic second-hit loss-of-function variants in the mTOR repressor DEPDC5. Here, we present a proof-of-concept model of DEPDC5 two-hit inactivation mosaicism using patient-derived human cortical organoids (hCOs). Mosaic hCOs displayed increased mTOR activity that was rescued by the mTOR inhibitor rapamycin. Mosaic hCOs also exhibited dysmorphic-like neurons and enhanced neuronal excitability, recapitulating key FCDII pathology hallmarks. Single-cell transcriptomics across three developmental stages revealed aberrant differentiation trajectories leading to premature upper-layer neuron generation, upregulated Notch and Wnt signaling pathways in neural progenitors, and altered expression of synaptic- and epilepsy-associated genes in excitatory neurons. In addition, we identified cell-autonomous alterations in metabolism and translation in mosaic DEPDC5 two-hit hCOs. This study provides novel insights into how DEPDC5 deficiency perturbs human corticogenesis, highlighting that mosaic biallelic inactivation of the gene is necessary for FCDII pathogenesis.
Semantic variant of primary progressive aphasia is a clinical subtype of frontotemporal lobar degeneration and is marked by TDP-43 subtype C pathology (FTLD-TDP C). It is a sporadic disease, yet has a strikingly homogene...Semantic variant of primary progressive aphasia is a clinical subtype of frontotemporal lobar degeneration and is marked by TDP-43 subtype C pathology (FTLD-TDP C). It is a sporadic disease, yet has a strikingly homogeneous clinicopathological presentation, suggesting a common pathophysiology. The aim of this study was to discover dysregulated pathways in FTLD-TDP C through transcriptomics of the temporal cortex, its most affected region. Bulk RNA sequencing was conducted on temporal cortices of a post-mortem cohort of 18 FTLD-TDP C patients and 23 sex- and age-matched controls. Differential expression and functional analyses were run to detect differentially expressed genes with FDR<0.05 (DEG) and functionally annotate them. We assessed enrichment of TARDBP's protein interactors and RNA targets in DEG. Our findings were compared to other published RNA sequencing data of tauopathies (Alzheimer's dementia, progressive supranuclear palsy and FTLD with MAPT), FTLD-TDP (subtypes A&B) and available proteomics of this cohort. Furthermore, we performed weighted gene co-expression network analysis (WGCNA). We adjusted for differences in cell type composition between cases and controls using cell deconvolution, and removed genes dysregulated in temporal cortices of other datasets. In DEG of FTLD-TDP we focused on enrichment of synaptic processes using SynGO. We found upregulation of damage response, cell structure, RNA splicing processes and downregulation of synaptic processes in 6322 DEG and five disease-related WGCNA modules. TARDBP-related genes were enriched in DEG. Additionally, transmembrane transport across the neurovascular unit was dysregulated. After cell deconvolution and removal of common tau-genes, postsynaptic processes remained dysregulated, specifically gene ontology terms 'modulation of chemical synaptic transmission' and 'neurotransmitter receptor localisation to postsynaptic specialisation membrane'. We found eleven synaptic FTLD-TDP C-specific genes affected on both RNA- and protein-level in the temporal cortex, which were involved in synaptic adhesion (CADM1, NCAN), signal transmission (COMT, RGS144, SLC1A2, TUBB2B) and synaptic plasticity (BEGAIN, ITPKA, LRFN1, RAB3B, SYNPO). In conclusion, a wide range of processes were dysregulated on RNA-level in the temporal cortex of FTLD-TDP C, including commonly affected processes in neurodegeneration, such as structural cell alterations. Dysregulation of TARDBP-related genes and RNA splicing has also been observed in other TDP-43 proteinopathies. Importantly, we found that postsynaptic processes were downregulated in FTLD-TDP C, after removing tauopathy-related genes and after cell deconvolution. In particular, assembly of receptors at the postsynaptic membrane and synaptic signal transmission were affected, both on RNA and protein level. Future research on these pathways could elucidate distinct pathophysiological mechanisms and guide targeted clinical approaches.
Galectin-3 (Gal3) acts as an intracellular sensor of lysosomal damage and a key driver of microglial activation and neuroinflammation in multiple neurodegenerative disorders. Despite its biological importance, no inhibit...Galectin-3 (Gal3) acts as an intracellular sensor of lysosomal damage and a key driver of microglial activation and neuroinflammation in multiple neurodegenerative disorders. Despite its biological importance, no inhibitors have been identified that both modulate intracellular Gal3 activity and effectively cross the blood-brain barrier (BBB). Here, we established an innovative high-content imaging platform utilizing microglia expressing Gal3-GFP, allowing direct visualization of Gal3 puncta formation upon lysosomal damage as a phenotypic readout for compound screening. Through screening of approximately 24,000 small molecules, we identified berbamine hydrochloride as a potent inhibitor of Gal3 puncta formation with confirmed BBB permeability. Mechanistically, berbamine hydrochloride disrupts Gal3 oligomerization and Gal3-TREM2 interaction via a unique allosteric mechanism distinct from the canonical glycan-binding domain. It attenuated lipopolysaccharide-induced inflammation in vitro, and achieved sustained brain exposure in vivo. In the R6/2 mouse model of Huntington's disease (HD), berbamine hydrochloride effectively improved motor functions, reduced mutant huntingtin protein aggregation, and restored crucial dopaminergic and ciliary signaling pathways. Transcriptomic profiling further identified Gal3 as a central regulatory hub within HD-associated networks that were corrected upon treatment. Computational docking and molecular dynamics simulations further supported an allosteric binding mode distinct from Gal3's canonical glycan-binding domain. Together, these findings establish berbamine hydrochloride as the first BBB-penetrant small molecule inhibitor targeting intracellular Gal3 with therapeutic benefit in HD. Furthermore, the puncta-based screening strategy we developed provides a robust platform for discovering intracellular modulators of Gal3 relevant to a wide range of neurological diseases.
Gaur N, Angerer C, Gunes ZI
… +19 more, Ancau M, Wang M, Riemenschneider H, Hurler CA, Mungwa S, Lüningschrör P, Zhiti A, Steinbach R, Briese M, Srivastava M, Plaas M, Hermann A, Sendtner M, Jäkel S, Edbauer D, Herms J, Liebscher S, Grosskreutz J, Brill MS
Chitinases are hydrolytic enzymes responsible for degrading chitin and have been evolutionarily conserved across various species. Although their signaling pathways are not fully understood, the chitinases are considered...Chitinases are hydrolytic enzymes responsible for degrading chitin and have been evolutionarily conserved across various species. Although their signaling pathways are not fully understood, the chitinases are considered active immunomodulators across several cell types. Specific isoforms, including Chitotriosidase-1 (CHIT1), Chitinase-3-like protein 1 (CHI3L1), and human-specific Chitinase-3-like protein 2 (CHI3L2), have emerged as markers of inflammation across the neurodegenerative spectrum, including amyotrophic lateral sclerosis (ALS). ALS is a fatal neuromuscular condition, and therapeutic development has been severely hindered by phenotypic heterogeneity and an incomplete understanding of etiology. Although several overlapping disease mechanisms can contribute to neuronal death, inflammation can exacerbate pathology. Prior studies have reported that CHIT1, CHI3L1, and CHI3L2 levels are elevated in the cerebrospinal fluid (CSF) of ALS patients and associated with disease aggressiveness. Nevertheless, several open questions critical to our understanding of the chitinases' role in ALS disease burden remain: namely, 1) which cell types in the central nervous system (CNS) are chitinase sources under physiological conditions, 2) which of these display chitinase upregulation in ALS, and 3) what is the diagnostic utility of the chitinases relative to established biomarkers. Here, we utilize pre-clinical models and post-mortem human tissue to demonstrate at both the transcriptomic and protein level that neurons are a primary source of chitinases; furthermore, neuronal chitinase expression is conserved across species. Under physiological conditions, CHI3L1 is more abundant and widely expressed across various cell types, whereas CHIT1 is predominantly expressed in neurons. Additionally, utilizing symptomatic mice from three familial ALS models, we demonstrate isoform-specific expression profiles, with astroglial and microglial upregulation of CHI3L1, and neuronal and microglial upregulation of CHIT1. Differing expression dynamics and diagnostic utility were also noted in our clinical cohort: CSF CHIT1 and CHI3L2 levels had more discriminatory power when distinguishing between ALS vs. non-ALS controls, while CHI3L1 was more closely associated with inflammation and aging across the neurodegenerative spectrum. Although the chitinases did not diagnostically outperform the neurofilament proteins as biomarkers, we propose that appreciating their expression patterns can aid in optimizing biomarker-guided trial design. Taken together, we demonstrate that chitinase upregulation in ALS is evident in various CNS cell types and that its neuronal expression may provide new insights into its role in disease activity.
Amyloid-β (Aβ) accumulation is a hallmark of Alzheimer's disease. Cerebral Aβ deposition is attenuated by a functional glymphatic system, in which perivascular entry of cerebrospinal fluid (CSF) and its exchange with int...Amyloid-β (Aβ) accumulation is a hallmark of Alzheimer's disease. Cerebral Aβ deposition is attenuated by a functional glymphatic system, in which perivascular entry of cerebrospinal fluid (CSF) and its exchange with interstitial fluid mediate solute clearance. Parenchymal border macrophages (PBMs), positioned along glymphatic pathways, are emerging as important players for glymphatic clearance. However, how glymphatic function and PBMs are affected in App knock-in models of Alzheimer's disease is unknown. In this study, we used two App knock-in mouse models that develop progressive Aβ pathology, AppNL-F and AppNL-G-F. AppNL-F mice showed reductions in glymphatic influx and clearance at 6 months, preceding substantial Aβ plaque deposition. The decrease in glymphatic function in AppNL-F mice correlated with a loss of PBMs and altered marker expression. Acute administration of Aβ into the CSF decreased the number of PBMs and impaired glymphatic transport in wild-type mice, thus recapitulating the pre-plaque stage. In contrast, the number of PBMs was not reduced in AppNL-G-F mice, possibly due to an enhanced Aβ phagocytic capacity in PBMs. Four weeks of systemic anti-Aβ antibody treatment efficiently reduced Aβ plaque load and rescued PBMs in some brain regions, however, the treatment did not restore glymphatic function in the AppNL-F model. These findings suggest that glymphatic dysfunction in App knock-in models of Alzheimer's disease is not driven by parenchymal Aβ plaque load but is closely linked to pre-plaque Aβ-induced loss of PBMs. Preservation of PBM abundance and their normal marker expression may be important for maintaining glymphatic function and mitigating early progression of Alzheimer's disease.
We here propose a new concept linked to neuroplasticity and cognitive reserve: Connectomic reserve. It is suggested and discussed as a hypothesis, aiming to stimulate experimental testing, and taking as an example the ex...We here propose a new concept linked to neuroplasticity and cognitive reserve: Connectomic reserve. It is suggested and discussed as a hypothesis, aiming to stimulate experimental testing, and taking as an example the exuberant circuits formed along development by commissural neurons and their projections. Upon reviewing the developmental strategies of formation of callosal circuits, from axonal emission by cortical cell bodies to the choice of trajectories within the ipsi and contralateral hemispheres, we identified the formation of many ectopic and heterotopic projections. Ectopic projections were first described in cases of congenital malformations, but were later shown to exist also in typical adult brains. Heterotopic projections are usually presumed to be eliminated and give way to the more restricted set of connections of adult brains. However, many experiments have shown that they, in fact, remain "hidden" in the brain throughout life in typical subjects of many species. Morphological shaping (pruning or enlargement), and physiological modulation (inhibition or enhancement) of these circuits would be resources to optimize the function of the alternative bundles and preterminal arbors, typical of neuroplasticity. The former mechanisms would take place during development, the latter in adulthood. Connectomic reserve, thus, would consist of a pervasive set of connections broadly distributed throughout the brain, susceptible to selective neuroplastic shaping or modulation depending on the requirements of the external or internal environment. Of course, being a hypothesis, it requires experimental testing in brain circuits other than commissural tracts, and functional validation using emerging imaging techniques with great resolution.
This scientific commentary refers to ‘Muscle transcriptomics of alpha-sarcoglycanopathy highlights inflammatory pathways driving disease’ by Amaro . (https://doi.org/10.1093/brain/awaf389).This scientific commentary refers to ‘Muscle transcriptomics of alpha-sarcoglycanopathy highlights inflammatory pathways driving disease’ by Amaro . (https://doi.org/10.1093/brain/awaf389).
Sleep occupies one-third of human life and serves critical functions in memory consolidation, metabolic regulation and neural homeostasis. Sleep disorders affect over 70 million people globally and are prevalent across n...Sleep occupies one-third of human life and serves critical functions in memory consolidation, metabolic regulation and neural homeostasis. Sleep disorders affect over 70 million people globally and are prevalent across neurodegenerative, psychiatric and neurological conditions. Recent advances in optogenetics and chemogenetics have enabled precise control of sleep-wake transitions in animal models, demonstrating that sleep can be actively modulated through targeted circuit manipulation. However, translating these findings to human applications faces substantial challenges. This review synthesizes current understanding of sleep circuit organization from animal studies, examines effects of direct brain stimulation on human sleep across diverse targets, analyzes discrepancies between animal and human findings and proposes translational strategies. While some principles appear conserved across species, significant differences in circuit architecture, technical capabilities and regulatory constraints necessitate novel approaches for human sleep modulation. We outline emerging solutions including improved spatiotemporal precision, oscillatory targeting and disease-specific interventions that may bridge the translational gap.
Opioids produce potent antinociception by activating μ-opioid receptors (MOR) in the spinal dorsal horn, where MOR is broadly expressed in both inhibitory and excitatory neurons. However, the neuron subtype-specific acti...Opioids produce potent antinociception by activating μ-opioid receptors (MOR) in the spinal dorsal horn, where MOR is broadly expressed in both inhibitory and excitatory neurons. However, the neuron subtype-specific actions and mechanisms of spinal MOR in opioid analgesia remain elusive. We employed chemogenetic approaches and conditional gene knockout strategies across multiple pain models to assess the roles of the NPY-NPY1R pathway and MOR signalling in spinal morphine analgesia. In addition, in situ hybridization combined with electrophysiological recordings from spinal cord slices was used to further investigate the underlying cellular and functional mechanisms. We demonstrate that MOR signalling in spinal neuropeptide Y (NPY)+ and NPY1 receptor (NPY1R)+ neurons exerts distinct effects on morphine analgesia under acute and inflammatory pain conditions in mice. Intrathecal injection of NPY synergistically enhanced morphine analgesia across pain models, an effect abolished by NPY1R antagonism or in Npy1r-/- mice. Chemogenetic activation of NPY+ interneurons or inhibition of NPY1R+ interneurons significantly reduced acute and persistent inflammatory pain. In situ hybridization further revealed that the MOR gene Oprm1 was co-expressed in 34% of NPY⁺ and 21% of NPY1R⁺ interneurons in the spinal dorsal horn. Notably, morphine analgesia is enhanced in mice with a specific Oprm1 deletion in NPY+ neurons (NpyCre;Oprm1fl/fl). However, loss of Oprm1 in NPY1R+ interneurons (Oprm1fl/fl/AAV-Npy1r-Cre-EGFP) impairs morphine analgesia. Furthermore, co-treatment with NPY or knockout of MOR in NPY+ neurons also prevented opioid-induced hyperalgesia and tolerance. Whole-cell recordings of spinal slices revealed that inflammation-induced hyperexcitability in both NPY+ and NPY1R+ neurons was suppressed by morphine perfusion, as evidenced by increased rheobase, hyperpolarized resting membrane potential and reduced action potential firing. These findings indicate that in inflammatory pain, morphine suppresses nociception by activating MOR expressed on NPY1R⁺ neurons, but undermines its antinociceptive efficacy by suppressing NPY⁺ neurons and disinhibiting the downstream nociception circuit in the spinal cord. Our data provides mechanistic insights into opioid analgesia at the spinal level and highlights the pharmacotherapeutic potential of the NPY-NPY1R pathway in pain management.