Decitabine cytotoxicity is promoted by dCMP deaminase DCTD and mitigated by SUMO-dependent E3 ligase TOPORS.

The nucleoside analogue decitabine (or 5-aza-dC) is used to treat several haematological cancers. Upon its triphosphorylation and incorporation into DNA, 5-aza-dC induces covalent DNA methyltransferase 1 DNA-protein crosslinks (DNMT1-DPCs), leading to DNA hypomethylation. However, 5-aza-dC's clinical outcomes vary, and relapse is common. Using genome-scale CRISPR/Cas9 screens, we map factors determining 5-aza-dC sensitivity. Unexpectedly, we find that loss of the dCMP deaminase DCTD causes 5-aza-dC resistance, suggesting that 5-aza-dUMP generation is cytotoxic. Combining results from a subsequent genetic screen in DCTD-deficient cells with the identification of the DNMT1-DPC-proximal proteome, we uncover the ubiquitin and SUMO1 E3 ligase, TOPORS, as a new DPC repair factor. TOPORS is recruited to SUMOylated DNMT1-DPCs and promotes their degradation. Our study suggests that 5-aza-dC-induced DPCs cause cytotoxicity when DPC repair is compromised, while cytotoxicity in wild-type cells arises from perturbed nucleotide metabolism, potentially laying the foundations for future identification of predictive biomarkers for decitabine treatment.

DNA Structure-Specific Cleavage of DNA-Protein Crosslinks by the SPRTN Protease.

Repair of covalent DNA-protein crosslinks (DPCs) by DNA-dependent proteases has emerged as an essential genome maintenance mechanism required for cellular viability and tumor suppression. However, how proteolysis is restricted to the crosslinked protein while leaving surrounding chromatin proteins unharmed has remained unknown. Using defined DPC model substrates, we show that the DPC protease SPRTN displays strict DNA structure-specific activity. Strikingly, SPRTN cleaves DPCs at or in direct proximity to disruptions within double-stranded DNA. In contrast, proteins crosslinked to intact double- or single-stranded DNA are not cleaved by SPRTN. NMR spectroscopy data suggest that specificity is not merely affinity-driven but achieved through a flexible bipartite strategy based on two DNA binding interfaces recognizing distinct structural features. This couples DNA context to activation of the enzyme, tightly confining SPRTN's action to biologically relevant scenarios.

Dysregulated lipid metabolism in TMZ-resistant glioblastoma: pathways, proteins, metabolites and therapeutic opportunities.

Glioblastoma (GBM) is a highly aggressive and lethal brain tumor with limited treatment options, such as the chemotherapeutic agent, temozolomide (TMZ). However, many GBM tumors develop resistance to TMZ, which is a major obstacle to effective therapy. Recently, dysregulated lipid metabolism has emerged as an important factor contributing to TMZ resistance in GBM. The dysregulation of lipid metabolism is a hallmark of cancer and alterations in lipid metabolism have been linked to multiple aspects of tumor biology, including proliferation, migration, and resistance to therapy. In this review, we aimed to summarize current knowledge on lipid metabolism in TMZ-resistant GBM, including key metabolites and proteins involved in lipid synthesis, uptake, and utilization, and recent advances in the application of metabolomics to study lipid metabolism in GBM. We also discussed the potential of lipid metabolism as a target for novel therapeutic interventions. Finally, we highlighted the challenges and opportunities associated with developing these interventions for clinical use, and the need for further research to fully understand the role of lipid metabolism in TMZ resistance in GBM. Our review suggests that targeting dysregulated lipid metabolism may be a promising approach to overcome TMZ resistance and improve outcomes in patients with GBM.

A ubiquitin switch controls autocatalytic inactivation of the DNA-protein crosslink repair protease SPRTN.

Repair of covalent DNA-protein crosslinks (DPCs) by the metalloprotease SPRTN prevents genome instability, premature aging and carcinogenesis. SPRTN is specifically activated by DNA structures containing single- and double-stranded features, but degrades the protein components of DPCs promiscuously and independent of amino acid sequence. This lack of specificity is useful to target diverse protein adducts, however, it requires tight control in return, in order to prohibit uncontrolled proteolysis of chromatin proteins. Here, we discover the components and principles of a ubiquitin switch, which negatively regulates SPRTN. We demonstrate that monoubiquitylation is induced in an E3 ligase-independent manner and, in contrast to previous assumptions, does not control chromatin access of the enzyme. Data obtained in cells and in vitro reveal that monoubiquitylation induces inactivation of the enzyme by triggering autocatalytic cleavage in trans while also priming SPRTN for proteasomal degradation in cis. Finally, we show that the deubiquitylating enzyme USP7 antagonizes this negative control of SPRTN in the presence of DPCs.

Pure and non-pure meningioangiomatosis of 36 Chinese patients: an analysis of clinical presentation, diagnosis, histopathology and prognosis.

Meningioangiomatosis (MA) is a disease that is extremely rarely reported. Sporadic MA is occasionally combined with meningioma or other lesions (identified as non-pure MA). This retrospective study investigated the difference between pure MA and non-pure MA by exploring clinical manifestations, histopathology characteristics, and outcomes of MA after surgery. We reviewed the medical records of 36 histopathologically confirmed MA patients (18 pure MA and 18 non-pure MA) who received surgery at our institution between 2012 and 2021. We compared differences in demographic, clinical, imaging, pathological features, and surgical outcomes between pure MA and non-pure MA through descriptive statistics. Compared to non-pure MA, pure MA presented with a more prominent male predilection (5:1 vs. 1.57:1, P = 0.264), a higher seizure incidence (83.3% vs 50.0%, P = 0.038), a more seizure type of GTCS (14/15 vs 5/9, P = 0.047), a less prominent enhancement on MRI (27.8% vs 88.9%, P < 0.001) and a preference of temporal and frontal lobe (100% vs 44.4%, P < 0.001). The differences in clinical characteristics between pure MA and non-pure MA demonstrate their disparate biological natures. Pure MA seems to be a non-neoplastic lesion, while non-pure MA is commonly combined with meningioma, which is a neoplastic lesion. A correct differential diagnosis can be achieved via a triad of the type of seizure, the location of lesion and the radiological presentation. MA is curable and the prognosis is excellent as most patients are free of seizure and recurrence after surgical treatment.

miR-105/93-3p promotes chemoresistance and circulating miR-105/93-3p acts as a diagnostic biomarker for triple negative breast cancer.

BACKGROUND: Triple negative breast cancer (TNBC) lacks both early detection biomarkers and viable targeted therapeutics. Moreover, chemotherapy only produces 20-30% pathologic complete response. Because miRNAs are frequently dysregulated in breast cancer and have broad tissue effects, individual or combinations of circulating miRNAs may serve as ideal diagnostic, predictive or prognostic biomarkers, as well as therapeutic targets. Understanding the role and mechanism of dysregulated miRNAs in TNBC may help to develop novel diagnostic and prognostic strategy for TNBC patients. METHODS: The miRNA array profiles of 1299 breast cancer patients were collected from the Metabric database and subjected to analysis of the altered miRNAs between TNBC and non-TNBC. In Student's t-test and Kaplan-Meier analysis, four upregulated miRNAs correlated with poor survival in TNBC but not in non-TNBC. Four miRNAs were manipulated in multiple cell lines to investigate their functional role in carcinogenesis. From these results, we studied miR-105 and miR-93-3p in greater detail. The level of miR-105 and miR-93-3p were evaluated in 25 breast cancer tumor tissues. In addition, the diagnostic utility of circulating miR-105 and miR-93-3p were examined in 12 normal and 118 breast cancer plasma samples by ROC curve construction. RESULTS: miR-105 and miR-93-3p were upregulated and correlated with poor survival in TNBC patients. Both miR-105 and miR-93-3p were found to activate Wnt/ß-catenin signaling by downregulation of SFPR1. By this action, stemness, chemoresistance, and metastasis were promoted. Importantly, the combination of circulating miR-105/93-3p may serve as a powerful biomarker for TNBC, even in early-stage disease. CONCLUSIONS: miR-105/93-3p activates Wnt/ß-catenin signaling by downregulating SFRP1 and thereby promotes stemness, chemoresistance, and metastasis in TNBC cells. Most importantly, combined circulating miR-105/93-3p levels represent a prime candidate for development into a diagnostic biomarker for both early- and late-stage TNBC.

Zinc Sulfide Nanosheet-Based Hybrid Superlattices with Tunable Architectures Showing Enhanced Photoelectrochemical Properties.

Zinc sulfide nanosheet-based hybrid superlattices with tunable periodicities and rod-like or tubular morphologies are constructed by the spontaneous assembly of nanosheets as they grow in amine solution. The as-prepared architectures can be used as an enhanced electrode for photocurrent response and converted to other functional materials.

Mitochondrial Mechanisms in Temozolomide Resistance: Unraveling the Complex Interplay and Therapeutic Strategies in Glioblastoma.

Glioblastoma (GBM) is a highly aggressive and lethal brain tumor, with temozolomide (TMZ) being the standard chemotherapeutic agent for its treatment. However, TMZ resistance often develops, limiting its therapeutic efficacy and contributing to poor patient outcomes. Recent evidence highlights the crucial role of mitochondria in the development of TMZ resistance through various mechanisms, including alterations in reactive oxygen species (ROS) production, metabolic reprogramming, apoptosis regulation, biogenesis, dynamics, stress response, and mtDNA mutations. This review article aims to provide a comprehensive overview of the mitochondrial mechanisms involved in TMZ resistance and discuss potential therapeutic strategies targeting these mechanisms to overcome resistance in GBM. We explore the current state of clinical trials targeting mitochondria or related pathways in primary GBM or recurrent GBM, as well as the challenges and future perspectives in this field. Understanding the complex interplay between mitochondria and TMZ resistance will facilitate the development of more effective therapeutic strategies and ultimately improve the prognosis for GBM patients.

Electro-elution-based purification of covalent DNA-protein cross-links.

Covalent DNA-protein cross-links (DPCs) are pervasive DNA lesions that challenge genome stability and can be induced by metabolic or chemotherapeutic cross-linking agents including reactive aldehydes, topoisomerase poisons and DNMT1 inhibitors. The purification of x-linked proteins (PxP), where DNA-cross-linked proteins are separated from soluble proteins via electro-elution, can be used to identify DPCs. Here we describe a versatile and sensitive strategy for PxP. Mammalian cells are collected following exposure to a DPC-inducing agent, embedded in low-melt agarose plugs and lysed under denaturing conditions. Following lysis, the soluble proteins are extracted from the agarose plug by electro-elution, while genomic DNA and cross-linked proteins are retained in the plug. The cross-linked proteins can then be analyzed by standard analytical techniques such as sodium dodecyl-sulfate-polyacrylamide gel electrophoresis followed by western blotting or fluorescent staining. Alternatively, quantitative mass spectrometry-based proteomics can be used for the unbiased identification of DPCs. The isolation and analysis of DPCs by PxP overcomes the limitations of alternative methods to analyze DPCs that rely on precipitation as the separating principle and can be performed by users trained in molecular or cell biology within 2-3 d. The protocol has been optimized to study DPC induction and repair in mammalian cells but may also be adapted to other sample types including bacteria, yeast and tissue samples.

Occurrence and risk factors for post-stroke delirium: A systematic review and meta-analysis.

OBJECTIVES: Delirium is a significant health concern in acute stroke patients. We aim to systematically summarize existing evidence to conduct a meta-analysis to quantify the occurrence and risk factors for delirium after acute stroke. METHOD: PubMed, EMBASE and MEDLINE were searched from inception to Feb. 2023 for prospective observational studies that reported the incidence or prevalence of post-stroke delirium and/or evaluated potential risk factors. The search strategy was created using controlled vocabulary terms and text words for stroke and delirium. We performed a meta-analysis of the estimates for occurrence and risk factors using random-effects models. Meta-regression and subgroup meta-analyses were conducted to explore the sources of heterogeneity. Study quality and quality of evidence were assessed using the customized Newcastle-Ottawa Scale and GRADE, respectively. RESULTS: Forty-nine studies that enrolled 12383 patients were included. The pooled occurrence rate of post-stroke delirium was 24.4 % (95 %CI, 20.4 %-28.9 %, I2=96.2 %). The pooled occurrence of hyperactive, hypoactive, and mixed delirium was 8.5 %, 5.7 % and 5.0 %, respectively. Study location, delirium assessment method and stroke type independently affected the heterogeneity of the pooled estimate of delirium. Statistically significant risk factors were older age, low education level, cigarette smoking, alcohol drinking, atrial fibrillation, lower ADL level, higher pre-stroke mRS score, premorbid cognitive impairment or dementia, aphasia, total anterior circulation impairment, higher National Institute of Health Stroke Scale score and infection. CONCLUSIONS: Delirium affected 1 in 4 acute stroke patients, although reported rates may depend on assessment method and stroke type. Timely prevention, recognition and intervention require prioritizing patients with dominant risk factors.

Is brain invasion sufficient as a stand-alone criterion for grading atypical meningioma?

OBJECTIVE: Despite the controversy surrounding brain invasion (BI) as the sole indicator used to diagnose atypical meningioma, this criterion was still incorporated in the 2021 WHO classification scheme. In this study, the authors investigated the reproducibility of this prognostic effect and the impact of BI on the prognosis in otherwise benign meningioma (benign meningioma with BI). METHODS: Patients (n = 1006) with a pathological diagnosis of benign or atypical meningioma according to the latest WHO classification criteria were enrolled in this study. In patients with atypical meningioma, the cases were further categorized as benign meningioma with BI and classical atypical meningioma. Clinical, pathological, and follow-up data were collected. Kaplan-Meier curves were compared with a log-rank test, and univariate and multivariate analyses were performed. RESULTS: The study patient cohort included 282 (28.0%) individuals who were pathologically confirmed as having BI among all 1006 patients with benign or atypical meningioma. A significant difference in recurrence-free survival was observed between patients who had benign meningioma with BI and those who had classical atypical meningioma (p < 0.001), as well as between patients with benign meningiomas and those without BI (p = 0.003). Multivariate Cox analysis indicated that BI was independently associated with increased risk of relapse in the entire population (HR 1.46, 95% CI 1.01-2.12, p = 0.049) and in the atypical meningioma subcohort (HR 2.21, 95% CI 1.32-3.71, p = 0.003), as well as the benign meningioma with and without BI subcohorts (HR 1.89, 95% CI 1.01-3.56, p = 0.049). Moreover, patients with classical atypical meningiomas had a risk of relapse four times higher than those who had benign meningioma with BI (p < 0.001). CONCLUSIONS: The findings demonstrate that benign meningioma with BI typically has an intermediate prognosis and can be differentiated from benign meningioma and classical atypical meningioma, which suggests that the importance of the diagnostic effect of BI is insufficiently accounted for in grading of atypical meningioma. Increased emphasis on the presence of BI in patients with atypical meningioma may be helpful in postsurgical decision-making and facilitating improvements in individual therapy.

Carboxyl-terminal modulator protein facilitates tumor metastasis in triple-negative breast cancer.

Currently, the survival rate for breast cancer is more than 90%, but once the cancer cells metastasize to distal organs, the survival rate is dramatically reduced, to less than 30%. Triple-negative breast cancer accounts for 15-20% of all breast cancers. Triple-negative breast cancer (TNBC) is associated with poor prognostic and diagnostic outcomes due to the limiting therapeutic strategies, relative to non-TNBC breast cancers. Therefore, the development of targeted therapy for TNBC metastasis remains an urgent issue. In this study, high Carboxyl-terminal modulator protein (CTMP) is significantly associated with recurrence and disease-free survival rate in TNBC patients. Overexpression of CTMP promotes migration and invasion abilities in BT549 cells. Down-regulating of CTMP expression inhibits migration and invasion abilities in MDA-MB-231 cells. In vivo inoculation of high-CTMP cells enhances distant metastasis in mice. The metastasis incidence rate is decreased in mice injected with CTMP-downregulating MDA-MB-231 cells. Gene expression microarray analysis indicates the Akt-dependent pathway is significantly enhanced in CTMP overexpressing cells compared to the parental cells. Blocking Akt activation via Akt inhibitor treatment or co-expression of the dominant-negative form of Akt proteins successfully abolishes the CTMP mediating invasion in TNBC cells. Our findings suggest that CTMP is a potential diagnostic marker for recurrence and poor disease-free survival in TNBC patients. CTMP promotes TNBC metastasis via the Akt-activation-dependent pathway.

SPRTN patient variants cause global-genome DNA-protein crosslink repair defects.

DNA-protein crosslinks (DPCs) are pervasive DNA lesions that are induced by reactive metabolites and various chemotherapeutic agents. Here, we develop a technique for the Purification of x-linked Proteins (PxP), which allows identification and tracking of diverse DPCs in mammalian cells. Using PxP, we investigate DPC repair in cells genetically-engineered to express variants of the SPRTN protease that cause premature ageing and early-onset liver cancer in Ruijs-Aalfs syndrome patients. We find an unexpected role for SPRTN in global-genome DPC repair, that does not rely on replication-coupled detection of the lesion. Mechanistically, we demonstrate that replication-independent DPC cleavage by SPRTN requires SUMO-targeted ubiquitylation of the protein adduct and occurs in addition to proteasomal DPC degradation. Defective ubiquitin binding of SPRTN patient variants compromises global-genome DPC repair and causes synthetic lethality in combination with a reduction in proteasomal DPC repair capacity.

Heat shock protein 90 stabilizes nucleolin to increase mRNA stability in mitosis.

Most studies on heat shock protein 90 (Hsp90) have focused on the involvement of Hsp90 in the interphase, whereas the role of this protein in the nucleus during mitosis remains largely unclear. In this study, we found that the level of the acetylated form of Hsp90 decreased dramatically during mitosis, which indicates more chaperone activity during mitosis. We thus probed proteins that interacted with Hsp90 by liquid chromatography/mass spectrometry (LC/MS) and found that nucleolin was one of those interacting proteins during mitosis. The nucleolin level decreased upon geldanamycin treatment, and Hsp90 maintained the cyclin-dependent kinase 1 (CDK1) activity to phosphorylate nucleolin at Thr-641/707. Mutation of Thr-641/707 resulted in the destabilization of nucleolin in mitosis. We globally screened the level of mitotic mRNAs and found that 229 mRNAs decreased during mitosis in the presence of geldanamycin. Furthermore, a bioinformatics tool and an RNA immunoprecipitation assay found that 16 mRNAs, including cadherin and Bcl-xl, were stabilized through the recruitment of nucleolin to the 3'-untranslated regions (3'-UTRs) of those genes. Overall, strong correlations exist between the up-regulation of Hsp90, nucleolin, and the mRNAs related to tumorigenesis of the lung. Our findings thus indicate that nucleolin stabilized by Hsp90 contributes to the lung tumorigenesis by increasing the level of many tumor-related mRNAs during mitosis.

Higher Grade Glioma Increases the Risk of Postoperative Delirium: Deficient Brain Compensation Might Be a Potential Mechanism of Postoperative Delirium.

Objective: The brain compensation mechanism in postoperative delirium (POD) has not been reported. We uncovered the mechanism by exploring the association between POD and glioma grades, and the relationship between preoperative brain structural and functional compensation with POD in patients with frontal glioma. Methods: A total of 335 adult patients with glioma were included. The multivariable analysis examined the association between tumor grade and POD. Then, 20 patients with left frontal lobe glioma who had presurgical structural and functional MRI data and Montreal Cognitive Assessment (MoCA) in this cohort were analyzed. We measured the gray matter volume (GMV) and functional connectivity (FC) in patients with (n = 8) and without (n = 12) POD and healthy controls (HCs, n = 29) to detect the correlation between the structural and functional alteration and POD. Results: The incidence of POD was 37.3%. Multivariable regression revealed that high-grade glioma had approximately six times the odds of POD. Neuroimaging data showed that compared with HC, the patients with left frontal lobe glioma showed significantly increased GMV of the right dorsal lateral prefrontal cortex (DLPFC) in the non-POD group and decreased GMV of right DLPFC in the POD group, and the POD group exhibited significantly decreased FC of right DLPFC, and the non-POD group showed the increasing tendency. Partial correlation analysis showed that GMV in contralesional DLPFC were positively correlated with preoperative neurocognition, and the GMV and FC in contralesional DLPFC were negatively correlated with POD. Conclusions: Our findings suggested that insufficient compensation for injured brain regions involving cognition might be more vulnerable to suffering from POD.

Tangutidines A-C, Three Amphoteric Diterpene Alkaloids from Aconitum tanguticum.

Three new diterpene alkaloids, tangutidines A-C (1-3), and four known alkaloids (4-7) were isolated from the whole plant of Aconitum tanguticum, from which amphoteric diterpene alkaloids (1-3) were obtained for the first time. The structures of 1-3 were elucidated by detailed interpretation of spectroscopic data, including MS and NMR data. All of them were evaluated for their cytotoxic activities.

Development of an early prediction model for postoperative delirium in neurosurgical patients admitted to the ICU after elective craniotomy (E-PREPOD-NS): A secondary analysis of a prospective cohort study.

Postoperative delirium (POD) is a significant clinical problem in neurosurgical patients after intracranial surgery. Identification of high-risk patients may optimize perioperative management, but an adequate risk model for use at early phase after operation has not been developed. In the secondary analysis of a prospective cohort study, 800 adult patients admitted to the ICU after elective intracranial surgeries were included. The POD was diagnosed as Confusion Assessment Method for the ICU positive on postoperative day 1 to 3. Multivariate logistic regression analysis was used to develop early prediction model (E-PREPOD-NS) and the final model was validated with 200 bootstrap samples. The incidence of POD in this cohort was19.6%. We identified nine variables independently associated with POD in the final model: advanced age (OR 3.336, CI 1.765-6.305, 1 point), low education level (OR 2.528, 1.446-4.419, 1), smoking history (OR 2.582, 1.611-4.140, 1), diabetes (OR 2.541, 1.201-5.377, 1), supra-tentorial lesions (OR 3.424, 2.021-5.802, 1), anesthesia duration > 360 min (OR 1.686, 1.062-2.674, 0.5), GCS < 9 at ICU admission (OR 6.059, 3.789-9.690, 1.5), metabolic acidosis (OR 13.903, 6.248-30.938, 2.5), and neurosurgical drainage tube (OR 1.924, 1.132-3.269, 0.5). The area under the receiver operator curve (AUROC) of the risk score for prediction of POD was 0.865 (95% CI 0.835-0.895). The AUROC was 0.851 after internal validation (95% CI 0.791-0.912). The model showed good calibration. The E-PREPOD-NS model can predict POD in patients admitted to the ICU after elective intracranial surgery with good accuracy. External validation is needed in the future.

Intracranial chordoid glioma: A clinical, radiological and pathological study of 14 cases.

BACKGROUND: Chordoid gliomas (CGs) are rare neuroepithelial tumors, which commonly arise from the anterior part of the third ventricle. Most studies on CGs included only one or two cases. To better understand the disease, we report 14 patients with pathologically confirmed CGs. METHOD: The clinical characteristics, including radiological and histological examination, operative records, and prognoses were analyzed and reviewed. RESULT: The case series included six male and eight female patients with an average age of 44.4 years. The most common preoperative symptom was headache (64.3%) and visual deterioration (57.1%). Radiological results showed that the third ventricle (12/14) was the most common site of the brain involved, and the lesions presented with solid (n = 9, 64.3%) or cystic-solid (n = 5, 35.7%) appearance. All patients were misdiagnosed as non-CG tumors. The operation approach was mainly determined by tumor location, thus trans-callosal approach (9/14) and trans-laminar terminalis approach were commonly used. Gross total resection (GTR) was achieved in all cases and none of them received any adjuvant therapy postoperatively. The most frequent postoperative complications were diabetes insipidus, electrolyte disturbance, hypopituitarism, cognitive dysfunction, and obstructive hydrocephalus. During an average follow-up period of 40.1 months, 2 cases (14.3%) were died of refractory hypopituitarism and pulmonary embolism, respectively. The preoperative symptoms and postoperative complications were all significantly improved in other 12 patients, and MRI showed no tumor recurrence. CONCLUSION: According to our experience, we recommend GTR as the primary goal, which is associated with improved rates of tumor control and without increasing rates of postoperative complications.

Publisher Correction: Orexin signaling modulates synchronized excitation in the sublaterodorsal tegmental nucleus to stabilize REM sleep.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Orexin signaling modulates synchronized excitation in the sublaterodorsal tegmental nucleus to stabilize REM sleep.

The relationship between orexin/hypocretin and rapid eye movement (REM) sleep remains elusive. Here, we find that a proportion of orexin neurons project to the sublaterodorsal tegmental nucleus (SLD) and exhibit REM sleep-related activation. In SLD, orexin directly excites orexin receptor-positive neurons (occupying ~3/4 of total-population) and increases gap junction conductance among neurons. Their interaction spreads the orexin-elicited partial-excitation to activate SLD network globally. Besides, the activated SLD network exhibits increased probability of synchronized firings. This synchronized excitation promotes the correspondence between SLD and its downstream target to enhance SLD output. Using optogenetics and fiber-photometry, we consequently find that orexin-enhanced SLD output prolongs REM sleep episodes through consolidating brain state activation/muscle tone inhibition. After chemogenetic silencing of SLD orexin signaling, a ~17% reduction of REM sleep amounts and disruptions of REM sleep muscle atonia are observed. These findings reveal a stabilization role of orexin in REM sleep.