Cognitive Impairments, Neuroinflammation and Blood-Brain Barrier Permeability in Mice Exposed to Chronic Sleep Fragmentation during the Daylight Period

Circulating exosomes in pediatric obstructive sleep apnea with or without neurocognitive deficits and their effects on a 3D-blood-brain barrier spheroid model

Obstructive sleep apnea (OSA) in children is linked to cognitive impairments, potentially due to blood-brain barrier (BBB) dysfunction. Exosomes, small vesicles released by most cells, reflect cellular changes. This study examined the effects of exosomes from children with OSA, with or without cognitive deficits, on neurovascular unit (NVU) models. Twenty-six children were categorized into three groups: healthy controls (Cont, n = 6), OSA without cognitive deficits (OSA-NG, n = 10), and OSA with neurocognitive deficits (OSA-POS, n = 10). Plasma exosomes were characterized and applied to human 3D NVU spheroids for 24 h. Barrier integrity, permeability, and angiogenesis were assessed using trans-endothelial electrical resistance (TEER), tight junction integrity, and tube formation assays. Single-nucleus RNA sequencing (snRNA-seq) and bioinformatics, including CellChat analysis, identified intercellular signaling pathways. Results showed that exosomes from OSA-POS children disrupted TEER, increased permeability, and impaired ZO1 staining in spheroids, compared to the other groups. Both OSA-POS and OSA-NG exosomes increased permeability in NVU cells in monolayer and microfluidic BBB models. snRNA-seq analysis further revealed distinct cell clusters and pathways associated with the different groups. This 3D NVU spheroid model provides a robust platform to study BBB properties and the role of exosomes in OSA. These findings suggest that integrating snRNA-seq with exosome studies can uncover mechanisms underlying neurocognitive dysfunction in pediatric OSA, potentially leading to personalized therapeutic approaches.

Obstructive sleep apnea and memory impairments: Clinical characterization, treatment strategies, and mechanisms

Obstructive sleep apnea (OSA), is associated with dysfunction in the cardiovascular, metabolic and neurological systems. However, the relationship between OSA and memory impairment, intervention effects, and underlying pathways are not well understood. This review summarizes recent advances in the clinical characterization, treatment strategies, and mechanisms of OSA-induced memory impairments. OSA patients may exhibit significant memory declines, including impairments in working memory from visual and verbal sources. The underlying mechanisms behind OSA-related memory impairment are complex and multifactorial with poorly understood aspects that require further investigation. Neuroinflammation, oxidative stress, neuronal damage, synaptic plasticity, and blood-brain barrier dysfunction, as observed under exposures to intermittent hypoxia and sleep fragmentation are likely contributors to learning and memory dysfunction. Continuous positive airway pressure treatment can provide remarkable relief from memory impairment in OSA patients. Other treatments are emerging but need to be rigorously evaluated for cognitive improvement. Clinically, reliable and objective diagnostic tools are necessary for accurate diagnosis and clinical characterization of cognitive impairments in OSA patients. The complex links between gut-brain axis, epigenetic landscape, genetic susceptibility, and OSA-induced memory impairments suggest new directions for research. Characterization of clinical phenotypic clusters can facilitate advances in precision medicine to predict and treat OSA-related memory deficits.

Prolonged 5-week and 12-week chronic stress differentially modulates CNS expression of pro- and anti-neuroinflammatory biomarkers, brain monoamines and affective behavior in adult zebrafish

Chronic stress is a major cause of affective pathogenesis, such as anxiety and depression. Experimental animal models, including rodents and zebrafish, are a valuable tool for translational neuroscience research focusing on stress-related brain disorders. Here, we examined the effects of 5- and 12-week chronic unpredictable stress (CUS5 and CUS12) on zebrafish behavior, whole-body cortisol and neuroinflammation-related biomarker gene expression, including markers of pro-inflammatory microglia (NOS2a, COX2, P75NTR) and astroglia (C3, GBP), and markers of anti-inflammatory microglia (ARG-1, CD206) and astroglia (S100a10, PTX). We also assessed stress-induced changes in brain monoamine levels and brain-blood-barrier permeability. Overall, CUS5 induced anxiety-like behavior, accompanied by elevated CNS pro-inflammatory marker gene expression, cortisol signaling and norepinephrine levels. In contrast, CUS12 induced depression-like behavior, accompanied by lowered cortisol levels, impaired serotonin turnover and activated anti-inflammatory biomarker gene expression, as well as upregulated histone deacetylase 4 gene (suggesting the involvement of epigenetic regulation). Collectively, this confirms the importance of stress duration as a key factor in the development of stress-related disorders in zebrafish models, and further implicates pro- and inti-inflammatory neuroglia in affective pathogenesis.

Rutin ameliorates stress-induced blood‒brain barrier dysfunction and cognitive decline via the endothelial HDAC1‒Claudin-5 axis

BACKGROUND

Emerging evidence suggests that chronic stress compromises blood‒brain barrier (BBB) integrity by disrupting brain microvascular endothelial cells (BMECs), contributing to the development of cognitive impairments. Thus, targeting the BBB is expected to be a promising treatment strategy. The biological function of rutin has been investigated in neurological disorders; however, its regulatory role in stress-induced BBB damage and cognitive decline and the underlying mechanisms remain elusive.

METHODS

In a chronic unpredictable mild stress (CUMS) mouse model, a fluorescent dye assay and behavioral tests, including a novel object recognition test and Morris water maze, were performed to evaluate the protective effects of rutin on BBB integrity and cognition. The effects of rutin on BMEC function were also investigated in hCMEC/D3 cells (a human brain microvascular endothelial cell line) in vitro. Furthermore, the molecular mechanisms by which rutin restores BBB endothelium dysfunction were explored via RNA-seq, quantitative real-time PCR, western blotting, immunofluorescence and chromatin immunoprecipitation. Finally, biotinylated tumor necrosis factor-α (TNF-α) was employed to test the influence of rutin on the ability of circulating TNF-α to cross the BBB.

RESULTS

We identified that rutin attenuated BBB hyperpermeability and cognitive impairment caused by the 8-week CUMS procedure. Moreover, rutin promoted the proliferation, migration and angiogenesis ability of BMECs, and the integrity of the cellular monolayer through positively regulating the expression of genes involved. Furthermore, rutin impeded histone deacetylase 1 (HDAC1) recruitment and stabilized H3K27ac to increase Claudin-5 protein levels. Ultimately, normalization of the hippocampal HDAC1‒Claudin-5 axis by rutin blocked the infiltration of circulating TNF-α into the brain parenchyma and alleviated neuroinflammation.

CONCLUSIONS

This work establishes a protective role of rutin in regulating BMEC function and BBB integrity, and reveals that rutin is a potential drug candidate for curing chronic stress-induced cognitive deficits.

Individualised Therapy for Obstructive Sleep Apnoea: Predictive Models and Anatomical Phenotyping of Mandibular Advancement Devices Responses

OBJECTIVES

This non-randomised clinical study aimed to identify the phenotypic characteristics that distinguish responders from non-responders. Additionally, it sought to establish a predictive model for treatment response to obstructive sleep apnoea (OSA) using mandibular advancement devices (MAD), based on the analysed phenotypic characteristics.

MATERIAL AND METHODS

This study, registered under identifier NCT05596825, prospectively analysed MAD treatment over 6 years using two-piece adjustable appliances according to a standardised protocol. Two response definitions aligned with the latest International Consensus Statement on OSA severity were established. Logistic regression and CHAID models integrated baseline clinical, anthropometric, cephalometric anatomical, soft tissue characteristics and physiological upper airway variables.

RESULTS

A total of 112 patients completed the study: 64 responders and 48 non-responders according to response definition 1, and 81 responders and 31 non-responders according to response definition 2. Responders to MAD treatment had lower body mass index (BMI), neck and waist circumference, Epworth Sleepiness Scale scores, apnoea-hypopnea index (AHI), snoring intensity on the Visual Analog Scale, CPAP pressure, and higher T90% and minSaO2. Patients exhibiting greater anatomical imbalance, smaller airway volume, smaller minimum cross-sectional area (CSAmin) and longer airway length demonstrated a poorer response to treatment.

CONCLUSIONS

Airway length, initial T90% and anterior facial height collectively formed a highly predictive logistic regression model for response definition 1. Jarabak's ratio, gonial angle, CSAmin, airway length, initial BMI and baseline AHI constituted a highly predictive model for the second response definition. Furthermore, the CHAID regression tree established cutoff values for the variables that form the predictive models.

Polysomnographic phenotypes: predictors of treatment response in Obstructive Sleep Apnea with Mandibular Advancement devices

PURPOSE

This non-randomized clinical study aims to identify polysomnographic phenotypic characteristics that differentiate responders from non-responders to mandibular advancement devices (MAD) treatment for obstructive sleep apnea (OSA) and to establish a predictive model of treatment response for OSA using oral devices based on the set of anthropometric, demographic, and polysomnographic phenotypic characteristics.

METHODS

This study was registered under the identifier number: NCT02724865. It prospectively analyzed patients receiving MAD treatment for six years. The MADs used were two-piece adjustable appliances following a standardized protocol. Treatment response was defined according to the latest International Consensus Statement on OSA severity. The study analyzed polysomnographic phenotypes, categorizing them into positional phenotype, sleep-stage phenotype (REM/NREM-OSA), and airway collapsibility phenotype. A logistic regression model and a classification and regression tree were implemented.

RESULTS

A total of 112 patients completed the study (64 responders and 48 non-responders). Positional-OSA patients had higher response rates than non-positional (64.1% vs. 35.9; p 0.032). REM-OSA and apnea-predominant phenotype showed a lower response (p < 0.001). In these phenotypes, most patients were women, with higher body mass index, higher scores in the Epworth Sleepiness Scale, lower minSaO2 in REM-OSA phenotype, and higher T90% in apnea-predominant phenotype.

CONCLUSION

This study underscores the importance of hypoxic burden in the severity of OSA. The parameters T90% and POSA formed predictive model. Additionally, MAD appears to be less effective in the REM-OSA phenotype. Moreover, although patients with an apnea-predominant phenotype responded less favorably, there was a conversion from apneas to hypopneas, reducing severity.

Differential inflammatory profiles in carriers of reciprocal 22q11.2 copy number variants

BACKGROUND

Genetic copy number variants (CNVs; i.e., a deletion or duplication) at the 22q11.2 locus confer increased risk of neuropsychiatric disorders and immune dysfunction. Inflammatory profiles of 22q11.2 CNV carriers can shed light on gene-immune relationships that may be related to neuropsychiatric symptoms. However, little is known about inflammation and its relationship to clinical phenotypes in 22q11.2 CNV carriers. Here, we investigate differences in peripheral inflammatory markers in 22q11.2 CNV carriers and explore their relationship with psychosis risk symptoms and sleep disturbance.

METHODS

Blood samples and clinical assessments were collected from 22q11.2 deletion (22qDel) carriers (n=45), 22q11.2 duplication (22qDup) carriers (n=29), and typically developing (TD) control participants (n=92). Blood plasma levels of pro-inflammatory cytokines, including interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), and anti-inflammatory cytokine interleukin-10 (IL-10) were measured using a MesoScale Discovery multiplex immunoassay. Plasma levels of C-reactive protein (CRP) were measured using Enzyme-linked Immunosorbent Assay (ELISA). Linear mixed effects models controlling for age, sex, and body mass index were used to: a) examine group differences in inflammatory markers between 22qDel, 22qDup, and TD controls, b) test differences in inflammatory markers between 22qDel carriers with psychosis risk symptoms (22qDelPS+) and those without (22qDelPS-), and c) conduct an exploratory analysis testing the effect of sleep disturbance on inflammation in 22qDel and 22qDup carriers. A false discovery rate correction was used to correct for multiple comparisons.

RESULTS

22qDup carriers exhibited significantly elevated levels of IL-8 relative to TD controls (q<0.001) and marginally elevated IL-8 levels relative to 22qDel carriers (q=0.08). There were no other significant differences in inflammatory markers between the three groups (q>0.13). 22qDelPS+ exhibited increased levels of IL-8 relative to both 22qDelPS- (q=0.02) and TD controls (p=0.002). There were no relationships between sleep and inflammatory markers that survived FDR correction (q>0.14).

CONCLUSION

Our results suggest that CNVs at the 22q11.2 locus may have differential effects on inflammatory processes related to IL-8, a key mediator of inflammation produced by macrophages and microglia. Further, these IL-8-mediated inflammatory processes may be related to psychosis risk symptoms in 22qDel carriers. Additional research is required to understand the mechanisms contributing to these differential levels of IL-8 between 22q11.2 CNV carriers and IL-8's association with psychosis risk.

Cerebral oxidative stress, inflammation and apoptosis induced by intermittent hypoxia: a systematic review and meta-analysis of rodent data

Obstructive sleep apnoea (OSA) contributes to cerebrovascular diseases and cognitive decline. Preclinical studies support the deleterious impact on the brain of intermittent hypoxia (IH), one of the main components of OSA, but heterogeneity in rodent species and brain regions studied, or induced by IH paradigms, can challenge interpretation of the studies. Hence, we conducted a systematic review and meta-analysis to evaluate the impact of IH on rodent brain oxidative stress, inflammation, apoptosis and the expression of brain-derived neurotrophic factor (BDNF) and hypoxia-inducible factor 1 (HIF-1). PubMed and Web of Science searches identified 663 articles related to IH exposure, of which 60 were included. The examined outcomes were oxidative stress, inflammation, apoptosis, HIF-1 or BDNF in brains. Standardised mean difference was used to compare studies. Metaregressions were performed to clarify the impact of IH exposure parameters, rodent characteristics or cerebral localisation on these outcomes. IH-induced oxidative stress (increased malondialdehyde (MDA) and NADPH oxidase (NOX) and decreased superoxide dismutase), increased inflammation (tumour necrosis factor-α, NF-κB and inducible nitric oxide synthase), HIF-1 and apoptosis evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labelling and cleaved caspase-3. In contrast, B-cell lymphoma 2 (BCL2) and BDNF expression were not significantly modified. Metaregressions showed that MDA, NOX and BDNF were associated with determinants of IH cycles (inspired oxygen fraction and duration of hypoxia) and some parameters depended on localisation. Rodent characteristics had little impact on the outcomes. Our meta-analysis robustly establishes that IH, independently of other confounders, has a strong effect on the brain by inducing oxidative stress, inflammation and apoptosis in rodent models. Our findings support the interest of considering and treating cerebral consequences of OSA in clinical practice.

Association of sleep quality with cognitive dysfunction in middle-aged and elderly adults: a cross-sectional study in China

Objectives

Sleep is an indispensable part of human health, which can help us to restore physical strength, enhance immunity and maintain nervous system stability. The relationship between sleep quality and cognitive dysfunction is unclear, especially at the community population level. This study aims to explore the association between sleep quality and cognitive dysfunction.

Methods

A total of 5,224 community residents were enrolled in this cross-sectional study. Cognitive function was assessed by the Mini-Mental State Examination (MMSE). Sleep quality was assessed by the multidimensional sleep questionnaire. Multivariate logistic regression was used to analyze the association between sleep quality and cognitive dysfunction. The adjusted models took into account relevant demographic, clinical, and sleep variables.

Results

A total of 3,106 participants were enrolled in this study, of whom 463 (15%) had cognitive dysfunction. Total sleep duration, staying up, sleep latency, number of awakenings, and history of sleep medications were associated with cognitive dysfunction in unadjusted models, and these effects were consistent after adjustment. First, those who slept 6-7.9 h per day (OR = 0.57, 95% CI 0.40 to 0.80, p = 0.001) had a lower risk for cognitive dysfunction compared to those who slept less than 6 h per day. Second, participants who stayed up more than 10 times over the 3 months (OR = 1.90, 95% CI 1.20 to 3.00, p = 0.006) were more likely to suffer cognitive dysfunction than those who never stayed up. Third, we also found that participants with sleep latencies of 16-30 min were less likely to experience cognitive dysfunction than those with sleep latencies of less than 16 min after adjusting confounders (OR = 0.33, 95% CI 0.23 to 0.47, p < 0.001). Fourth, participants who woke up once (OR = 1.65, 95% CI 1.19 to 2.30, p = 0.003) and three or more times (OR = 2.34, 95% CI 1.25 to 4.36, p = 0.008) after falling asleep had a higher risk than those who did not wake up at night. Last, participants taking sleep medication (OR = 2.97, 95% CI 1.19 to 7.45, p = 0.020) were more vulnerable to cognitive dysfunction, relative to participants without taking any medications.

Conclusion

Our results suggest that after adjustment for potential confounding variables, poor sleep quality is associated with cognitive dysfunction.

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

Melatonin modulates TLR4/MyD88/NF-κB signaling pathway to ameliorate cognitive impairment in sleep-deprived rats

Sleep deprivation (SD) is commonplace in today's fast-paced society. SD is a severe public health problem globally since it may cause cognitive decline and even neurodegenerative disorders like Alzheimer's disease. Melatonin (MT) is a natural chemical secreted by the pineal gland with neuroprotective effects. The purpose of this study was to investigate the protective effect and mechanism of MT on chronic sleep deprivation-induced cognitive impairment. A 3-week modified multi-platform method was used to create the SD rat model. The Morris water maze test (MWM), Tissue staining (including Hematoxylin and Eosin (H & E) staining, Nissl staining, and immunofluorescence), Western blot, Enzyme-linked immunosorbent assay (ELISA), and Quantitative real-time polymerase chain reaction (qPCR) were used to investigate the protective effect and mechanism of MT in ameliorating cognitive impairment in SD rats. The results showed that MT (50 and 100 mg/kg) significantly improved cognitive function in rats, as evidenced by a shortening of escape latency and increased time of crossing the platform and time spent in the quadrant. Additionally, MT therapy alleviated hippocampus neurodegeneration and neuronal loss while lowering levels of pathogenic factors (LPS) and inflammatory indicators (IL-1β, IL-6, TNF-α, iNOS, and COX2). Furthermore, MT treatment reversed the high expression of Aβ42 and Iba1 as well as the low expression of ZO-1 and occludin, and inhibited the SD-induced TLR4/MyD88/NF-κB signaling pathway. In summary, MT ameliorated spatial recognition and learning memory dysfunction in SD rats by reducing neuroinflammation and increasing neuroprotection while inhibiting the TLR4/MyD88/NF-κB signaling pathway. Our study supports the use of MT as an alternate treatment for SD with cognitive impairment.

Real-time visualization of dextran extravasation in intermittent hypoxia mice using noninvasive SWIR imaging

Imaging tools are crucial for studying the vascular network and its barrier function in various physiopathological conditions. Shortwave infrared (SWIR) window optical imaging allows noninvasive, in-depth exploration. We applied SWIR imaging, combined with vessel segmentation and deep learning analyses, to study real-time dextran probe extravasation in mice experiencing intermittent hypoxia (IH)-a characteristic of obstructive sleep apnea associated with potential cardiovascular alterations due to early vascular permeability. Evidence for permeability in this context is limited, making our investigation significant. C57Bl/6 mice were exposed to normoxia or intermittent hypoxia for 14 days. Then SWIR imaging between 1,250 and 1,700 nm was performed on the saphenous artery and vein and on the surrounding tissue after intravenous injection of labeled dextrans of two different sizes (10 or 70 kDa). Postprocessing and segmentation of the SWIR images were conducted using deep learning treatment. We monitored high-resolution signals, distinguishing arteries, veins, and surrounding tissues. In the saphenous artery and vein, after 70-kD dextran injection, tissue/vessel ratio was higher after intermittent hypoxia (IH) than normoxia (N) over 500 seconds (P < 0.05). However, the ratio was similar in N and IH after 10-kD dextran injection. The SWIR imaging technique allows noninvasive, real-time monitoring of dextran extravasation in vivo. Dextran 70 extravasation is increased after exposure to IH, suggesting an increased vessel permeability in this mice model of obstructive sleep apnea.NEW & NOTEWORTHY We demonstrate that SWIR imaging technique is a useful tool to monitor real-time dextran extravasation from vessels in vivo, with a high resolution. We report for the first time an increased real-time dextran (70 kD) extravasation in mice exposed to intermittent hypoxia for 14 days compared with normoxic controls.

The role of lncRNAs in intermittent hypoxia and sleep Apnea: A review of experimental and clinical evidence

In this narrative review, we present a comprehensive assessment on the putative roles of long non-coding RNAs (lncRNAs) in intermittent hypoxia (IH) and sleep apnea. Collectively, the evidence from cell culture, animal, and clinical research studies points to the functional involvement of lncRNAs in the pathogenesis, diagnosis, and potential treatment strategies for this highly prevalent disorder. Further research is clearly warranted to uncover the mechanistic pathways and to exploit the therapeutic potential of lncRNAs, thereby improving the management and outcomes of patients suffering from sleep apnea.