Effect on Intermittent Hypoxia on Plasma Exosomal Micro RNA Signature and Endothelial Function in Healthy Adults

The role and research progress of epigenetic modifications in obstructive sleep apnoea-hypopnea syndrome and related complications

Epigenetic modifications are heritable changes in gene expression that do not alter the DNA sequence. Histone modifications, non-coding RNA expression, and DNA methylation are examples of common epigenetic changes. Obstructive sleep apnoea-hypopnea syndrome (OSAHS) is the most common sleep-related breathing disorder, and its incidence is increasing annually, making it a hotspot of clinical research and significantly impacting health and well-being. The main cause of OSAHS is related to complications caused by repeated chronic intermittent hypoxia (CIH). Currently, polysomnography (PSG) and continuous positive airway pressure (CPAP) remain the gold standards for the diagnosis and treatment of OSAHS. However, their limitations-such as time consumption, high cost, and poor patient comfort-contribute to the paradox of high disease prevalence yet low rates of diagnosis and treatment, resulting in a substantial disease burden. In recent years, rapid advances in epigenetics have revealed that biomarkers such as microRNAs (miRNAs), circular RNAs (circRNAs), and other epigenetic modifications hold promise as non-invasive tools for the diagnosis and treatment of OSAHS and its related complications. Although numerous studies have explored epigenetic modifications in other diseases, this study focuses on how epigenetic modifications participate in the process of OSAHS and its related complications, with an aim of elucidating the pathogenesis of OSAHS from an epigenetic perspective and provide new directions for identifying molecular targets for the diagnosis and treatment of OSAHS and related complications.

Effect of hypoxia on extracellular vesicles in malignant and non-malignant conditions

Extracellular vesicles (EVs) are produced by virtually all types of cells and can be detected in nearly all extracellular places. These particles mediate intercellular communication and transfer their cargo to the recipient cells, inducing a variety of processes in these cells through transmission of several biomolecules such as miRNAs, lncRNAs, other transcripts and a variety of proteins. It has been documented that size, quantity, and expression of biomolecules in the EVs are influenced by the level of oxygen. In fact, hypoxia can affect several cellular processes through modulation of the cargo of these vesicles. Hypoxic exosomes derived from tumor cells have several protumoral effects on the recipient cells, including enhancement of proliferation, migration, and invasion in other tumoral cells, induction of metastasis in distant organs, stimulation of angiogenesis in the endothelial cells, and modulation of macrophage polarization. Hypoxic EVs also contribute to several non-malignant diseases. This review summarizes the effect of hypoxia on EVs cargo in malignant and nonmalignant diseases of different organs.

Exosomes from IH- Induced bEnd3 Cells Promote OSA Cognitive Impairment via miR-20a-5p/MFN2 Mediated Pyroptosis of HT22 Cells

Background

OSA can cause cognitive impairment (CI). The aim of this study was to investigate whether miR-20a-5p in exosomes derived from bEnd3 cells with IH mediates intercellular crosstalk and induces CI through hippocampal neuronal cell pyroptosis.

Materials and Methods

BEnd3-derived exosomes were isolated from the normal oxygen control group (NC-EXOS) and IH group (IH-EXOS). In vitro, exosomes were cocultured with HT22 cells. Meanwhile, in vivo, exosomes were injected into mice via the caudal vein. The spatial memory ability of mice was tested by MWM method to evaluate the effect of exosomes on the cognitive function of mice. Adults diagnosed with OSA underwent the MoCA and ESS tests to assess cognitive function and daytime sleepiness. Spearman's rank correlation analysis was used to evaluate the correlation between miR-20a-5p and candidate proteins and clinical parameters. Transfection using small interfering RNAs, miRNA mimics, and plasmids to evaluate the role of miR-20a-5p and its target genes. Dual luciferase reporter gene assay was used to confirm the binding of miR-20a-5p to its target gene.

Results

IH could cause pyroptosis and inflammation in bEnd3 cells, and promote the expression of miR-20a-5p. Isolated IH-EXOS induced increased pyroptosis and activation of inflammatory response in vitro and in vivo, accompanied by increased expression of miR-20a-5p. In addition, IH-EXOS led to decreased learning and memory ability in mice. Interestingly, AHI was higher and MoCA scores were lower in severe OSA compared to healthy comparisons. In addition, miR-20a-5p and GSDMD were positively correlated with AHI but negatively correlated with MoCA in severe OSA. IH-induced exosomes were rich in miR-20a-5p, and these exosomes were found to deliver miR-20a-5p to HT22 cells, playing a key role in the induction of OSA-CI by directly targeting MFN2.

Conclusion

Exosome miR-20a-5p from IH-stimulated bEnd3 cells can promote OSA-CI by increasing HT22 cells pyroptosis through its target MFN2.

Nocturia and obstructive sleep apnoea

Nocturia, the need to urinate at night, is a common symptom in patients with obstructive sleep apnoea (OSA). Continuous positive airway pressure treatment can reduce nocturia in some patients, but the underlying mechanisms are complex and not fully understood. OSA affects the autonomic nervous system, oxidative stress and endothelial damage. Furthermore, the commonly held theory attributing polyuria to a false signal of cardiac overload and response natriuresis has limitations. A comprehensive approach to the management of nocturia in OSA, considering factors such as comorbidities, medication use, alcohol consumption and lifestyle, is needed. Effective management of nocturia in OSA requires a multidisciplinary approach, and urologists should be aware of the potential effect of OSA on physiology and refer patients for further testing at a sleep centre. In addition to continuous positive airway pressure, other interventions such as oral appliances and surgical obstruction treatment could be beneficial for some patients. Overall, understanding the complex interplay between OSA and nocturia is crucial for optimizing patient outcomes.

Benchmarking miRNA reference genes in B-cell precursor acute lymphoblastic leukemia

MicroRNAs (miRNAs) play dual roles in acute lymphoblastic leukemia (ALL) as both tumor suppressors and oncogenes, and miRNA expression profiles can be used for patient risk stratification. Precise assessment of miRNA levels is crucial for understanding their role and function in gene regulation. Quantitative real-time polymerase chain reaction (qPCR) is a reliable, rapid, and cost-effective method for analyzing miRNA expression, assuming that appropriate normalization to stable references is performed to ensure valid data. In this study, we evaluated the stability of six commonly used miRNA references (5sRNA, SNORD44, RNU6, RNU1A1, miR-103a-3p, and miR-532-5p) across nine B-cell precursor (BCP) ALL cell lines, 22 patient-derived xenograft (PDX) BCP ALL samples from different organ compartments of leukemia bearing mice, and peripheral blood mononuclear cells (PBMCs) from six healthy donors. We used four different algorithms (Normfinder, ∆CT, geNorm, and BestKeeper) to assess the most stably expressed reference across all samples. Moreover, we validated our data in an additional set of 13 PDX ALL samples and six healthy controls, identifying miR-103a-3p and miR-532-5p as the most stable references for miRNA normalization in BCP ALL studies. Additionally, we demonstrated the critical importance of using a stable reference to accurately interpret miRNA data.

Soluble Vascular Adhesion Protein-1 Level Correlates With Adropin and Inflammatory Biomarkers in Patients With Obstructive Sleep Apnea

PURPOSE

Soluble vascular adhesion protein-1 (sVAP-1) and adropin are 2 biomarkers of endothelial dysfunction. The main purpose of this study was to evaluate the levels of sVAP-1 in patients with moderate and severe obstructive sleep apnea (OSA) compared to healthy controls, and to further determine the relationship between sVAP-1 and adropin levels, as well as inflammatory biomarkers and sleep parameters.

METHODS

In this study, we included 50 male patients with OSA (25 moderate and 25 severe) and 20 age- and sex-matched control subjects. Patients with OSA underwent polysomnography. All subjects underwent fasting peripheral blood sampling for laboratory analysis.

RESULTS

Serum sVAP-1 and inflammatory biomarkers (IL-6, TNF-α, and hsCRP) levels were significantly higher in patients with severe OSA compared to those with moderate OSA and control groups, while plasma levels of adropin showed the opposite trend. Furthermore, sVAP-1 levels had a significant positive correlation with AHI, ODI, TNF-α, IL-6, and hsCRP levels and a significant negative correlation with adropin levels. The receiver operating characteristic analysis showed an Area Under Curve (AUC) of .876 (P < .001) for sVAP-1 levels predicting OSA. Serum sVAP-1 threshold of > 445.5 ng/mL had an 88% sensitivity and 80% specificity for detecting OSA status. Multivariate regression analysis demonstrated that sVAP-1 remained a significant positive predictor of OSA severity.

CONCLUSIONS

Increased sVAP-1 levels in OSA patients are significantly correlated with indices of OSA severity, adropin levels, and inflammatory biomarkers, suggesting that sVAP-1 plays a vital role in the pathophysiology of OSA and may become a potential screening tool in the evaluation of OSA severity.

Identification biomarkers in disease progression of obstructive sleep apnea from children serum based on WGCNA and Mfuzz

Obstructive sleep apnea (OSA) syndrome is a prevalent form of respiratory sleep disorder, with an increasing prevalence among children. The consequences of OSA include obesity, diabetes, cardiovascular disease, and neuropsychological diseases. Despite its pervasive impact, a significant proportion of individuals especially children remain unaware that they suffer from OSA. Consequently, there is an urgent need for an accessible diagnostic approach. In this study, we conducted a bioinformatic analysis to identify potential biomarkers from a proteomics dataset comprising serum samples from children with OSA in the progression stage. In the Gene Set Enrichment Analysis (GSEA), we observed that the complement and immune response pathways persisted throughout the development of OSA and could be detected in the early stages. Subsequent to soft clustering and WGCNA analysis, it was revealed that the Hippo pathway, including ITGAL and FERMT3, plays a role in mild OSA. The analysis revealed a significant alteration of the complement and coagulation pathways, including TFPI and MLB2, in moderate OSA. In severe OSA, there was an association between hypoxia and the extracellular matrix (ECM) receptor interaction and collagen binding. In summary, it can be posited that the systemic inflammation may persist throughout the progression of OSA. Furthermore, severe OSA is characterized by abnormal vascular endothelial function, which may be attributed to chronic hypoxia. Finally, four potential biomarkers (ITGAL, TFPI, TTR, ANTXR1) were identified based on LASSO regression, and a prediction model for OSA progression was constructed based on the biomarkers.

Obstructive Sleep Apnea Plasma-Derived Exosomes Mediate Cognitive Impairment Through Hippocampal Neuronal Cell Pyroptosis

OBJECTIVE

Obstructive sleep apnea (OSA) is associated with impaired cognitive function. Exosomes are secreted by most cells and play a role in OSA-associated cognitive impairment (CI). The aim of this study was to investigate whether OSA plasma-derived exosomes cause CI through hippocampal neuronal cell pyroptosis, and to identify exosomal miRNAs in OSA plasma-derived.

MATERIALS AND METHODS

Plasma-derived exosomes were isolated from patients with severe OSA and healthy comparisons. Daytime sleepiness and cognitive function were assessed using the Epworth Sleepiness Scale (ESS) and the Beijing version of the Montreal Cognitive Assessment Scale (MoCA). Exosomes were coincubated with mouse hippocampal neurons (HT22) cells to evaluate the effect of exosomes on pyroptosis and inflammation of HT22 cells. Meanwhile, exosomes were injected into C57BL/6 male mice via caudal vein, and then morris water maze was used to evaluate the spatial learning and memory ability of the mice, so as to observe the effects of exosomes on the cognitive function of the mice. Western blot and qRT-PCR were used to detect the expressions of Gasdermin D (GSDMD) and Caspase-1 to evaluate the pyroptosis level. The expression of IL-1β, IL-6, IL-18 and TNF-α was detected by qRT-PCR to assess the level of inflammation. Correlations of GSDMD and Caspase-1 expression with clinical parameters were evaluated using Spearman's rank correlation analysis. In addition, plasma exosome miRNAs profile was identified, followed by Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways.

RESULTS

Compared to healthy comparisons, body mass index (BMI), apnea-hypopnea index (AHI), oxygen desaturation index (ODI), and ESS scores were increased in patients with severe OSA, while lowest oxygen saturation during sleep (LSaO2), mean oxygen saturation during sleep (MSaO2) and MoCA scores were decreased. Compared to the PBS group (NC) and the healthy comparison plasma-derived exosomes (NC-EXOS), the levels of GSDMD and Caspase-1 and IL-1β, IL-6, IL-18 and TNF-α were increased significantly in the severe OSA plasma-derived exosomes (OSA-EXOS) coincubated with HT22 cells. Compared to the NC and NC-EXOS groups, the learning and memory ability of mice injected with OSA-EXOS was decreased, and the expression of GSDMD and Caspase-1 in hippocampus were significantly increased, along with the levels of IL-1β, IL-6, IL-18 and TNF-α. Spearman correlation analysis found that clinical AHI in HCs and severe OSA patients was positively correlated with GSDMD and Caspase-1 in HT22 cells from NC-EXOS and OSA-EXOS groups, while negatively correlated with clinical MoCA. At the same time, clinical MoCA in HCs and severe OSA patients was negatively correlated with GSDMD and Caspase-1 in HT22 cells from NC-EXOS and OSA-EXOS groups. A unique exosomal miRNAs profile was identified in OSA-EXOS group compared to the NC-EXOS group, in which 28 miRNAs were regulated and several KEGG and GO pathways were identified.

CONCLUSIONS

The results of this study show a hypothesis that plasma-derived exosomes from severe OSA patients promote pyroptosis and increased expression of inflammatory factors in vivo and in vitro, and lead to impaired cognitive function in mice, suggesting that OSA-EXOS can mediate CI through pyroptosis of hippocampal neurons. In addition, exosome cargo from OSA-EXOS showed a unique miRNAs profile compared to NC-EXOS, suggesting that plasma exosome associated miRNAs may reflect the differential profile of OSA related diseases, such as CI.

Exosomes regulate SIRT3-related autophagy by delivering miR-421 to regulate macrophage polarization and participate in OSA-related NAFLD

PURPOSE

To analyze the role of and mechanism underlying obstructive sleep apnea (OSA)-derived exosomes in inducing non-alcoholic fatty liver (NAFLD).

METHODS

The role of OSA-derived exosomes was analyzed in inducing hepatocyte fat accumulation in mice models both in vivo and in vitro.

RESULTS

OSA-derived exosomes caused fat accumulation and macrophage activation in the liver tissue. These exosomes promoted fat accumulation; steatosis was more noticeable in the presence of macrophages. Macrophages could internalize OSA-derived exosomes, which promoted macrophage polarization to the M1 type. Moreover, it inhibited sirtuin-3 (SIRT3)/AMP-activated protein kinase (AMPK) and autophagy and promoted the activation of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasomes. The use of 3-methyladenine (3-MA) to inhibit autophagy blocked NLRP3 inflammasome activation and inhibited the M1 polarization of macrophages. miR-421 targeting inhibited SIRT3 protein expression in the macrophages. miR-421 was significantly increased in OSA-derived exosomes. Additionally, miR-421 levels were increased in OSA + NAFLD mice- and patient-derived exosomes. In the liver tissues of OSA and OSA + NAFLD mice, miR-421 displayed similar co-localization with the macrophages. Intermittent hypoxia-induced hepatocytes deliver miR-421 to the macrophages via exosomes to inhibit SIRT3, thereby participating in macrophage M1 polarization. After OSA and NAFLD modeling in miR-421-/- mice, liver steatosis and M1 polarization were significantly reduced. Additionally, in the case of miR-421 knockout, the inhibitory effects of OSA-derived exosomes on SIRT3 and autophagy were significantly alleviated. Furthermore, their effects on liver steatosis and macrophage M1 polarization were significantly reduced.

CONCLUSIONS

OSA promotes the delivery of miR-421 from the hepatocytes to macrophages. Additionally, it promotes M1 polarization by regulating the SIRT3/AMPK-autophagy pathway, thereby causing NAFLD.

Extracellular vesicles: Mediators of microenvironment in hypoxia-associated neurological diseases

Hypoxia is a prevalent characteristic of numerous neurological disorders including stroke, Alzheimer's disease, and Parkinson's disease. Extracellular vesicles (EVs) are minute particles released by cells that contain diverse biological materials, including proteins, lipids, and nucleic acids. They have been implicated in a range of physiological and pathological processes including intercellular communication, immune responses, and disease progression. EVs are believed to play a pivotal role in modulating the microenvironment of hypoxia-associated neurological diseases. These EVs are capable of transporting hypoxia-inducible factors such as proteins and microRNAs to neighboring or remote cells, thereby influencing their behavior. Furthermore, EVs can traverse the blood-brain barrier, shielding the brain from detrimental substances in the bloodstream. This enables them to deliver their payload directly to the brain cells, potentially intensifying the effects of hypoxia. Nonetheless, the capacity of EVs to breach the blood-brain barrier presents new opportunities for drug delivery. The objective of this study was to elucidate the role of EVs as mediators of information exchange during tissue hypoxia, a pathophysiological process in ischemic stroke and malignant gliomas. We also investigated their involvement in the progression and regression of major diseases of the central nervous system, which are pertinent to the development of therapeutic interventions for neurological disorders.

Small Extracellular Vesicles Harboring PD-L1 in Obstructive Sleep Apnea

Obstructive sleep apnea syndrome (OSA) has been associated with increased cancer incidence and aggressiveness. One hypothesis to support this association is the implication of immune response, particularly the programmed cell death pathway, formed by the receptor PD-1 and its ligand PD-L1. Recent studies have shown dysregulation of this pathway in severe OSA patients. It has also been shown that small extracellular vesicles (sEVs) carrying PD-L1 induce lymphocyte dysfunction. Thus, the aim of our study was to analyze the expression of PD-L1 on sEVs of OSA patients and to evaluate the role of sEVs on lymphocyte activation and cytotoxicity. Circulating sEVs were isolated from OSA patients and the control group. Lymphocytes were isolated from the control group. Circulating sEVs were characterized by western blot, nanotracking analysis, and flow cytometry and were incubated with lymphocytes. Our results show no differences in the quantity and composition of sEVs in OSA patients and no significant effects of sEVs in OSA patients on lymphocyte activation and cytotoxicity. These results suggest that OSA does not modify PD-L1 expression on sEVs, which does not contribute to dysregulation of cytotoxic lymphocytes.

Multi-Omics Analysis of Circulating Exosomes in Adherent Long-Term Treated OSA Patients

Obstructive sleep apnea (OSA) is a highly prevalent chronic disease affecting nearly a billion people globally and increasing the risk of multi-organ morbidity and overall mortality. However, the mechanisms underlying such adverse outcomes remain incompletely delineated. Extracellular vesicles (exosomes) are secreted by most cells, are involved in both proximal and long-distance intercellular communication, and contribute toward homeostasis under physiological conditions. A multi-omics integrative assessment of plasma-derived exosomes from adult OSA patients prior to and after 1-year adherent CPAP treatment is lacking. We conducted multi-omic integrative assessments of plasma-derived exosomes from adult OSA patients prior to and following 1-year adherent CPAP treatment to identify potential specific disease candidates. Fasting morning plasma exosomes isolated from 12 adult patients with polysomnographically-diagnosed OSA were analyzed before and after 12 months of adherent CPAP therapy (mean ≥ 6 h/night) (OSAT). Exosomes were characterized by flow cytometry, transmission electron microscopy, and nanoparticle tracking analysis. Endothelial cell barrier integrity, wound healing, and tube formation were also performed. Multi-omics analysis for exosome cargos was integrated. Exosomes derived from OSAT improved endothelial permeability and dysfunction as well as significant improvement in tube formation compared with OSA. Multi-omic approaches for OSA circulating exosomes included lipidomic, proteomic, and small RNA (miRNAs) assessments. We found 30 differentially expressed proteins (DEPs), 72 lipids (DELs), and 13 miRNAs (DEMs). We found that the cholesterol metabolism (has04979) pathway is associated with lipid classes in OSA patients. Among the 12 subjects of OSA and OSAT, seven subjects had complete comprehensive exosome cargo information including lipids, proteins, and miRNAs. Multi-omic approaches identify potential signature biomarkers in plasma exosomes that are responsive to adherent OSA treatment. These differentially expressed molecules may also play a mechanistic role in OSA-induced morbidities and their reversibility. Our data suggest that a multi-omic integrative approach might be useful in understanding how exosomes function, their origin, and their potential clinical relevance, all of which merit future exploration in the context of relevant phenotypic variance. Developing an integrated molecular classification should lead to improved diagnostic classification, risk stratification, and patient management of OSA by assigning molecular disease-specific therapies.

Circulating levels of miR125a, miR126, and miR146a-5p in patients with obstructive sleep apnea and their relation with markers of endothelial dysfunction

BACKGROUND

obstructive sleep apnea (OSA) is a prevalent sleep disorder that is associated with increased risk factors for cardiovascular diseases (CVDs). Oxidative stress, insulin resistance, inflammation, and endothelial dysfunction are increased in OSA patients and microRNAs (miRs) are regulatory elements that influence these pathological mechanisms. miR125a, miR126, and miR146a-5p play a role in these pathological mechanisms and have not been evaluated in patients with OSA.

METHOD

This case-control study was performed on 90 OSA patients and 34 controls. Circulating levels of miR125a, miR126, and miR146a-5 were determined using real-time PCR, and serum levels of hsCRP, ICAM-1, and VCAM-1 were evaluated using ELISA kits.

RESULTS

miR125a and miR146a were elevated in patients with OSA compared to controls while miR126 decreased significantly. All three miRs indicated a remarkable difference between the mild-OSA group compared to the severe-OSA group. Furthermore, patients with OSA showed elevated levels of hsCRP, ICAM-1, and VCAM-1. Multiple linear regression indicated an independent association of miR125a with ICAM-1 and hsCRP, miR126 associated with VCAM-1 and total cholesterol, and miR146a-5p represented an association with apnea-hypopnea index and ICAM-1. Furthermore, miR146a-5p illustrated a good diagnostic ability to differentiate between OSA and controls.

CONCLUSIONS

Circulating miR125a, miR126, and miR146a-5p fluctuations in patients with OSA and their relations with markers of endothelial dysfunction provide in vivo evidence and suggest a potential role for these miRs with endothelial dysfunction in patients with OSA.

Potential Pathophysiological Pathways in the Complex Relationships between OSA and Cancer

Several epidemiological and clinical studies have suggested a relationship between obstructive sleep apnea (OSA) and a higher incidence or severity of cancer. This relationship appears to be dependent on a myriad of factors. These include non-modifiable factors, such as age and gender; and modifiable or preventable factors, such as specific comorbidities (especially obesity), the use of particular treatments, and, above all, the histological type or location of the cancer. Heterogeneity in the relationship between OSA and cancer is also related to the influences of intermittent hypoxemia (a hallmark feature of OSA), among others, on metabolism and the microenvironment of different types of tumoral cells. The hypoxia inducible transcription factor (HIF-1α), a molecule activated and expressed in situations of hypoxemia, seems to be key to enabling a variety of pathophysiological mechanisms that are becoming increasingly better recognized. These mechanisms appear to be operationally involved via alterations in different cellular functions (mainly involving the immune system) and molecular functions, and by inducing modifications in the microbiome. This, in turn, may individually or collectively increase the risk of cancer, which is then, further modulated by the genetic susceptibility of the individual. Here, we provide an updated and brief review of the different pathophysiological pathways that have been identified and could explain the relationship between OSA and cancer. We also identify future challenges that need to be overcome in this intriguing field of research.

Extracellular Vesicles and Hypertension

Hypertension implicates multiple organs and systems, accounting for the majority of cardiovascular diseases and cardiac death worldwide. Extracellular vesicles derived from various types of cells could transfer a variety of substances such as proteins, lipids, and nucleic acids from cells to cells, playing essential roles in both physiological and pathological processes. Extracellular vesicles are demonstrated to be closely associated with the development of essential hypertension by mediating the renin-angiotensin-aldosterone system and crosstalk between multiple vascular cells. Extracellular vesicles also participate in various kinds of pathogenesis of secondary hypertensions including acute kidney injury, renal parenchymal diseases, kidney transplantation, secretory diseases (primary aldosteronism, pheochromocytoma and paraganglioma, Cushing's syndrome), and obstructive sleep apnea. Extracellular vesicles have been proved to have the potential to be served as new biomarkers in the diagnosis, treatment, and prognosis assessment of hypertension. In the future, large multicenter cohorts are highly in demand for further verifying the sensitivity and specificity of extracellular vesicles as biomarkers.

Obstructive Sleep Apnea: A Look towards Micro-RNAs as Biomarkers of the Future

Sleep-disordered breathing (SDB) includes a broad spectrum of diseases, of which obstructive sleep apnea syndrome (OSA) is the most clinically significant manifestation. OSA is a respiratory disorder characterized by episodes of complete or partial obstruction of the upper airways that disturb ventilation and sleep architecture. In recent years, interest in the clinical implications of OSA seems to have increased, probably due to the numerous studies that have shown the existence of an important correlation between OSA and cardiovascular, dysmetabolic, and neoplastic changes. The guidelines currently available highlight the importance of diagnosis and effective treatment for OSA, underlining the need for new biomarkers that are useful in clinical practice, feasible, and reproducible to guide medical decision making. In this review, we intend to provide an overview of the potential role of microRNAs as new indicators for OSA management. MicroRNAs (miRNAs) are small non-coding RNA molecules that play an important role in RNA silencing and regulation of gene expression at the post-transcriptional level. These can bind specifically to their target genes by forming silencing complexes, thus inducing degradation or altered gene expression. A wide range of miRNAs have been extensively studied in a variety of diseases including cancer, and recently, miRNAs have been shown to have enormous potential to function as diagnostic and clinical biomarkers of disease. This review includes recent studies that establish the inevitable role of miRNAs in the pathogenesis of OSA.

Gut-Derived Exosomes Induce Liver Injury After Intestinal Ischemia/Reperfusion by Promoting Hepatic Macrophage Polarization

Liver injury induced by intestinal ischemia/reperfusion (I/R) is accompanied by the polarization of Kupffer cells, which are specialized macrophages located in the liver. However, the causes of hepatic macrophage polarization after intestinal I/R remain unknown. This study investigated whether gut-derived exosomes contribute to the pathogenesis of liver injury triggered by intestinal I/R in a murine model and explored the underlying mechanisms. Intestinal I/R models were established by temporally clamping the superior mesenteric arteries of mice. Exosomes were isolated from the intestinal tissue of mice that underwent intestinal I/R or sham surgery according to a centrifugation-based protocol. Exosomes were co-cultured with RAW 264.7 macrophages or injected intravenously in mice. Liposomal clodronate was administered intraperitoneally to deplete the macrophages. Macrophage polarization was determined by flow cytometry, immunohistochemistry, and quantitative polymerase chain reaction. Liver injury was assessed by histological morphology and increased serum aspartate aminotransferase and alanine aminotransferase levels. Exosomes from mice intestines subjected to I/R (IR-Exo) promoted macrophage activation in vitro. Intravenous injection of IR-Exo caused hepatic M1 macrophage polarization and led to liver injury in mice. Depleting macrophages ameliorated liver injury caused by intestinal I/R or the injection of IR-Exo. Furthermore, inhibiting exosome release improved intestinal injury, liver function, and survival rates of mice subjected to intestinal I/R. Our study provides evidence that gut-derived exosomes induce liver injury after intestinal I/R by promoting hepatic M1 macrophage polarization. Inhibition of exosome secretion could be a therapeutic target for preventing hepatic impairment after intestinal I/R.

Experimental Models to Study End-Organ Morbidity in Sleep Apnea: Lessons Learned and Future Directions

Sleep apnea (SA) is a very prevalent sleep breathing disorder mainly characterized by intermittent hypoxemia and sleep fragmentation, with ensuing systemic inflammation, oxidative stress, and immune deregulation. These perturbations promote the risk of end-organ morbidity, such that SA patients are at increased risk of cardiovascular, neurocognitive, metabolic and malignant disorders. Investigating the potential mechanisms underlying SA-induced end-organ dysfunction requires the use of comprehensive experimental models at the cell, animal and human levels. This review is primarily focused on the experimental models employed to date in the study of the consequences of SA and tackles 3 different approaches. First, cell culture systems whereby controlled patterns of intermittent hypoxia cycling fast enough to mimic the rates of episodic hypoxemia experienced by patients with SA. Second, animal models consisting of implementing realistic upper airway obstruction patterns, intermittent hypoxia, or sleep fragmentation such as to reproduce the noxious events characterizing SA. Finally, human SA models, which consist either in subjecting healthy volunteers to intermittent hypoxia or sleep fragmentation, or alternatively applying oxygen supplementation or temporary nasal pressure therapy withdrawal to SA patients. The advantages, limitations, and potential improvements of these models along with some of their pertinent findings are reviewed.

Micro-RNA in obstructive sleep apnoea: biomarker of cardiovascular outcome?

PURPOSE OF REVIEW

Obstructive sleep apnoea (OSA) is a global health problem with important cardiovascular consequences. Risk assessment tools are essential in OSA to identify patients at increased risk of cardiovascular disease and to achieve a cost-effective clinical management of the disease in the era of precision medicine. The objective is to provide an updated perspective on the role of microRNAs (miRNAs) in OSA as a biomarker of cardiovascular risk.

RECENT FINDINGS

Specific miRNAs have already been associated with patients with OSA and specific cardiovascular diseases such as hypertension, myocardial infarction or endothelial dysfunction. Numerous studies have addressed the use of miRNAs to identify the cardiovascular risk associated with OSA, both in patients and in animals with in vivo hypoxia models. Thus, these studies identified profiles of differentially expressed miRNAs in patients with OSA. In addition, the in vitro studies suggest that therapies with miRNA inhibitors that could help reduce cardiovascular risk. Therefore, this review highlights the primary approaches of the potential of miRNAs as biomarkers at the prognostic, diagnostic and therapeutic strategy levels.

SUMMARY

Given the heterogeneity of OSA and its cardiovascular consequences, miRNAs have emerged as powerful biomarkers that can help improve the clinical management of OSA and its cardiovascular risk.

EVs-miRNA: The New Molecular Markers for Chronic Respiratory Diseases

Idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma and sleep disorders are chronic respiratory diseases that affect the airways, compromising lung function over time. These diseases affect hundreds of millions of people around the world and their frequency seems to be increasing every year. Extracellular vesicles (EVs) are small-sized vesicles released by every cell in the body. They are present in most body fluids and contain various biomolecules including proteins, lipids, mRNA and non-coding RNA (micro-RNA). The EVs can release their cargo, specifically micro-RNAs (miRNAs), to both neighboring and/or distal cells, playing a fundamental role in cell-cell communication. Recent studies have shown their possible role in the pathogenesis of various chronic respiratory diseases. The expression of miRNAs and, in particular, of miRNAs contained within the extracellular vesicles seems to be a good starting point in order to identify new potential biomarkers of disease, allowing a non-invasive clinical diagnosis. In this review we summarize some studies, present in the literature, about the functions of extracellular vesicles and miRNAs contained in extracellular vesicles in chronic respiratory diseases and we discuss the potential clinical applications of EVs and EVs-miRNAs for their possible use such as future biomarkers.

Intermittent Hypoxia and Atherosclerosis: From Molecular Mechanisms to the Therapeutic Treatment

Intermittent hypoxia (IH) has a dual nature. On the one hand, chronic IH (CIH) is an important pathologic feature of obstructive sleep apnea (OSA) syndrome (OSAS), and many studies have confirmed that OSA-related CIH (OSA-CIH) has atherogenic effects involving complex and interacting mechanisms. Limited preventive and treatment methods are currently available for this condition. On the other hand, non-OSA-related IH has beneficial or detrimental effects on the body, depending on the degree, duration, and cyclic cycle of hypoxia. It includes two main states: intermittent hypoxia in a simulated plateau environment and intermittent hypoxia in a normobaric environment. In this paper, we compare the two types of IH and summarizes the pathologic mechanisms and research advances in the treatment of OSA-CIH-induced atherosclerosis (AS), to provide evidence for the systematic prevention and treatment of OSAS-related AS.

Predictors of Sleep-Problem Trajectories Across Adolescence

Stress and sleep problems are significantly correlated in adolescents. Few longitudinal studies, however, have evaluated possible correlates and predictors of sleep problems at multiple points across adolescence. The current study examined the relation between stress and sleep problems across four years in a sample of adolescents who varied in risk for psychopathology. Participants included 223 adolescents (55% female) and 223 mothers (77% with a history of a mood disorder during their child's life). Youth were evaluated in grade 7 (M = 12.69 years, SD = 0.61) and again in grades 8, 9, and 11. Sleep problems were assessed as part of a clinical interview, and weekly stressful events were measured with the Life Events Interview for Adolescents. Multi-group latent growth curve analyses were conducted. Among youth whose mothers had a history of depression (high-risk), sleep problems significantly increased over time (p < .001). Second, among high-risk youth, at each time point, higher stress levels during the prior three months significantly predicted higher levels of sleep problems (p < .001). Finally, across the entire sample, at each time point a greater level of sleep problems predicted higher stress ratings a year later (p ≤ .001). Thus, stress was a significant predictor of sleep problems across multiple years of adolescence, particularly among offspring of mothers with a history of depression. Results highlight targets for preventive interventions for sleep problems in youth.

The Mystery of Exosomes in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is one of the common pregnancy complications, which increases the risk of short-term and long-term adverse consequences in both the mother and offspring. However, the pathophysiological mechanism of GDM is still poorly understood. Inflammation, insulin resistance and oxidative stress are considered critical factors in the occurrence and development of GDM. Although the lifestyle intervention and insulin are the primary treatment, adverse pregnancy outcomes still cannot be ignored. Exosomes have a specific function of carrying biological information, which can transmit information to target cells and play an essential role in intercellular communication. Their possible roles in normal pregnancy and GDM have been widely concerned. The possibility of exosomal cargos as biomarkers of GDM is proposed. This paper reviews the literature in recent years and discusses the role of exosomes in GDM and their possible mechanisms to provide some reference for the prediction, prevention, and treatment of GDM and improve the outcome of pregnancy.

Hypoxia Induced Changes of Exosome Cargo and Subsequent Biological Effects

Exosomes are small extracellular vesicles that are secreted by almost all types of cells and exist in almost all extracellular spaces. As an important mediator of intercellular communication, exosomes encapsulate the miRNA, lncRNA, cirRNA, mRNA, cytokine, enzyme, lipid, and other components from the cytoplasm into its closed single membrane structure and transfer them to recipient units in an autocrine, paracrine, or endocrine manner. Hypoxia is a state of low oxygen tension and is involved in many pathological processes. Hypoxia influences the size, quantity, and expression of exosome cargos. Exosomes derived from hypoxic tumor cells transfer genetics, proteins, and lipids to the recipient units to exert pleiotropic effects. Different donor cells produce different cargo contents, target different recipient units and lead to different biological effects. Hypoxic exosomes derived from tumor cells uptaken by normoxic tumor cells lead to promoted proliferation, migration, and invasion; uptaken by extracellular space or liver lead to promoted metastasis; uptaken by endothelial cells lead to promoted angiogenesis; uptaken by immune cells lead to promoted macrophage polarization and changed tumor immune microenvironment. In addition to various types of tumors, hypoxic exosomes also participate in the development of diseases in the cardiovascular system, neuron system, respiratory system, hematology system, endocrine system, urinary system, reproduction system, and skeletomuscular system. Understanding the special characteristics of hypoxic exosomes provide new insight into elaborating the pathogenesis of hypoxia related disease. This review summarizes hypoxia induced cargo changes and the biological effects of hypoxic exosomes in tumors and non-malignant diseases in different systems.

Relationships Between Cardinal Features of Obstructive Sleep Apnea and Blood Pressure: A Retrospective Study

BACKGROUND

Obstructive sleep apnea (OSA) is associated with hypertension; however, the associations between cardinal features of OSA, such as intermittent hypoxia (IH) and sleep fragmentation (SF), and blood pressure remain unclear. We performed this study to address this issue.

METHOD

We investigated 335 subjects with the polysomnography (PSG) tests. Data, including basic characteristics, PSG parameters, and blood pressure, were collected. We calculated p-values for linear trends of blood pressure across oxygen-desaturation index (ODI)/microarousal index (MAI) quartiles. Logistic regressions were used to determine the risk factors for abnormal blood pressure and to detect the multiplicative interaction between ODI and MAI with blood pressure.

RESULTS

After adjusting for multiple variables, compared with subjects with lower ODI quartiles, those with higher ODI quartiles had significant higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) (p for trend = 0.010 and 0.018, respectively). And compared with subjects with lower ODI quartiles, those with higher ODI quartiles were also more likely to have abnormal DBP and hypertension after adjusting for multiple variables. Similarly, compared with subjects with lower MAI quartiles, those with higher MAI quartiles had significant higher SBP and DBP, and were more likely to have abnormal DBP and hypertension. No significant multiplicative interactions between ODI and MAI with blood pressure were detected.

CONCLUSION

Subjects with more severe IH/SF had significant higher blood pressure and were more likely to have abnormal DBP and hypertension than those with less severe IH/SF. No interaction between IH and SF on the relationship with blood pressure was shown.

Cardiovascular Outcomes in Sleep-Disordered Breathing: Are We Under-estimating?

Obstructive sleep apnea is a growing health concern, affecting nearly one billion people worldwide; increasingly recognized as an independent cardiovascular risk factor associated with incident obesity, insulin resistance, hypertension, arrhythmias, stroke, coronary artery disease, and heart failure. The prevalence of obstructive sleep apnea could be underestimated in the previous studies, leading to only modest predictions of cardiovascular outcomes. Using more physiologic data will increase sensitivity for the diagnosis of obstructive sleep apnea. Individuals at high risk of obstructive sleep apnea should be identified so that treatment efforts can be focused on them. This review will assess the evidence for the relationship between obstructive sleep apnea and cardiovascular consequences in the past, present, and future. We will also explore the role of adding physiological data obtained from sleep studies and its ability to enhance the cardiovascular outcome's predictability. Finally, we will discuss future directions and gaps that need further research.

Obstructive Sleep Apnea Impacts Cardiac Function in Dilated Cardiomyopathy Patients Through Circulating Exosomes

Background

Obstructive sleep apnea (OSA) is common and independently associated with heart failure. This study aimed to investigate the impact of OSA on heart function in patients with dilated cardiomyopathy (DCM) as well as the possible mechanism related to exosomes regulated autophagy.

Methods and Results

A total of 126 patients with DCM who underwent sleep evaluations were analyzed retrospectively. Cardiomyocytes were treated with exosomes isolated from untreated OSA patients and healthy controls. Fibrotic and hypertrophic markers were evaluated, and Akt/mTOR pathway-mediated autophagy was investigated. DCM patients with severe OSA had larger right ventricular end-diastolic diameter (RVEDd) and right atrial diameter (RAD) and increased N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels than DCM patients without OSA. Moreover, NT-proBNP and diabetes mellitus were independently correlated with the apnea-hypopnea index in multiple linear regression analysis. Treatment with OSA-derived exosomes significantly increased Col1A1, ANP, and BNP protein expression and decreased the expression of the autophagy markers LC3B II/I and beclin1. Rapamycin treatment significantly increased the decreased autophagy markers and attenuated the increased expression of Col1A1, ANP and BNP induced by OSA-derived exosomes.

Conclusion

The severity of OSA is significantly associated with cardiac injury and remodeling. The underlying mechanism may be related to changed autophagy levels, which are regulated by circulating exosomes via the Akt/mTOR signaling pathway. This study may provide a new clue for the treatment of heart failure with OSA.

OSA and cardiorespiratory fitness: a review

The effects of untreated obstructive sleep apnea (OSA) on cardiopulmonary function remain unclear. Cardiorespiratory fitness (CRF), commonly reflected by VO₂ max measured during cardiopulmonary exercise testing, has gained popularity in evaluating numerous cardiopulmonary conditions and may provide a novel means of identifying OSA patients with the most clinically significant disease. This emerging testing modality provides simultaneous assessment of respiratory and cardiovascular function with results helping uncover evidence of evolving pathology in either organ system. In this review, we highlight the current state of the literature in regard to OSA and CRF with a specific focus on changes in cardiovascular function that have been previously noted. While OSA does not appear to limit respiratory function during exercise, studies seem to suggest an abnormal cardiovascular exercise response in this population including decreased cardiac output, a blunted heart rate response (ie, chronotropic incompetence), and exaggerated blood pressure response. Surprisingly, despite these observed changes in the cardiovascular response to exercise, results involving VO₂ max in OSA remain inconclusive. This is reflected by VO₂ max studies involving middle-aged OSA patients showing both normal and reduced CRF. As prior studies have not extensively characterized oxygen desaturation burden, we propose that reductions in VO₂ max may exist in OSA patients with only the most significant disease (as reflected by nocturnal hypoxia). Further characterizing this relationship remains important as some research suggests that positive airway pressure therapy or aerobic exercise may improve CRF in patients with OSA. In conclusion, while it likely that severe OSA, via an abnormal cardiovascular response to exercise, is associated with decreased CRF, further study is clearly warranted to include determining if OSA with decreased CRF is associated with increased morbidity or mortality.

CITATION

Powell TA, Mysliwiec V, Brock MS, Morris MJ. OSA and cardiorespiratory fitness: a review. J Clin Sleep Med. 2022;18(1):279-288.

Involvement of epithelia-derived exosomes in chronic respiratory diseases

Exosomes are tiny membrane lipid bilayer vesicles (φ40-100 nm) formed by the fusion of multivesicular bodies with plasma membrane, which are released extracellular by exocytosis. As natural nanocarriers, exosomes contain a variety of signal substances of the mother cell: nucleic acids, proteins and lipids, etc., which always play a vital role in the transmission of signal molecules between different cells. Epithelial cells are the first-line defense system against various inhaled allergens causing chronic respiratory diseases (CRD), such as asthma and chronic obstructive pulmonary disease (COPD). It's noted that increasing literature shows the exosomes derived from epithelial cells are involved in the pathogenesis of CRD. Moreover, the correlations between exosome cargo and the disease phenotypes show a high potential of using exosomes as biomarkers of CRD. In this review, we mainly focus on the physiological functions of epithelial-derived exosomes and illustrate the involved mechanism of epithelial-derived exosomes in common CRD.

Heterogeneity of Melanoma Cell Responses to Sleep Apnea-Derived Plasma Exosomes and to Intermittent Hypoxia

Obstructive sleep apnea (OSA) is associated with increased cutaneous melanoma incidence and adverse outcomes. Exosomes are secreted by most cells, and play a role in OSA-associated tumor progression and metastasis. We aimed to study the effects of plasma exosomes from OSA patients before and after adherent treatment with continuous positive airway pressure (CPAP) on melanoma cells lines, and also to identify exosomal miRNAs from melanoma cells exposed to intermittent hypoxia (IH) or normoxia. Plasma-derived exosomes were isolated from moderate-to-severe OSA patients before (V1) and after (V2) adherent CPAP treatment for one year. Exosomes were co-incubated with three3 different melanoma cell lines (CRL 1424; CRL 1619; CRL 1675) that are characterized by genotypes involving different mutations in BRAF, STK11, CDKN2A, and PTEN genes to assess the effect of exosomes on cell proliferation and migration, as well as on pAMK activity in the presence or absence of a chemical activator. Subsequently, CRL-1424 and CRL-1675 cells were exposed to intermittent hypoxia (IH) and normoxia, and exosomal miRNAs were identified followed by GO and KEG pathways and gene networks. The exosomes from these IH-exposed melanoma cells were also administered to THP1 macrophages to examine changes in M1 and M2 polarity markers. Plasma exosomes from V1 increased CRL-1424 melanoma cell proliferation and migration compared to V2, but not the other two cell lines. Exposure to CRL-1424 exosomes reduced pAMPK/tAMPK in V1 compared to V2, and treatment with AMPK activator reversed the effects. Unique exosomal miRNAs profiles were identified for CRL-1424 and CRL-1675 in IH compared to normoxia, with six miRNAs being regulated and several KEGG pathways were identified. Two M1 markers (CXCL10 and IL6) were significantly increased in monocytes when treated with exosomes from IH-exposed CRL-1424 and CRL-1625 cells. Our findings suggest that exosomes from untreated OSA patients increase CRL-1424 melanoma malignant properties, an effect that is not observed in two other melanoma cell lines. Exosomal cargo from CRL-1424 cells showed a unique miRNA signature compared to CRL-1675 cells after IH exposures, suggesting that melanoma cells are differentially susceptible to IH, even if they retain similar effects on immune cell polarity. It is postulated that mutations in STK-11 gene encoding for the serine/threonine kinase family that acts as a tumor suppressor may underlie susceptibility to IH-induced metabolic dysfunction, as illustrated by CRL-1424 cells.

The role of sleep disorders in cardiovascular diseases: Culprit or accomplice?

Sleep disorders frequently comorbid with several cardiovascular diseases (CVDs), attracting increasing scientific attention and interest. Sleep disorders include insomnia, sleep-disordered breathing, restless legs syndrome, etc. It is well known that inflammation, sympathetic activation, and endothelial dysfunction play critical roles in sleep disorders, all of which are predisposing factors for CVDs. The comorbidity of sleep disorders and CVDs may have a bidirectional relationship. Patients with CVDs may have a high incidence of sleep disorders and vice versa. This review focused on the comorbidity of sleep disorders and CVDs and discussed the potential pathophysiological mechanisms and therapeutic strategies. In addition to the existing mechanisms, this review summarized novel potential mechanisms underlying comorbidities, such as gut microbiota, orexin, and extracellular vesicles, which may provide a theoretical basis for further basic research and clinical investigations on improving therapeutic outcomes.

Interplay between Hypoxia and Extracellular Vesicles in Cancer and Inflammation

Simple Summary

Mounting evidence suggests a role for extracellular vesicles in cell-to-cell communication, in both physiological and pathological conditions. Moreover, the molecular content of vesicles can be exploited for diagnostic and therapeutic purposes. Inflamed tissues and tumors are often characterized by hypoxic areas, where oxygen levels drop dramatically. Several studies demonstrated that hypoxic stress affects the release of vesicles and their content. This review is intended to provide an exhaustive overview on the relationship between hypoxia and vesicles in inflammatory diseases and cancer.

Abstract

Hypoxia is a severe stress condition often observed in cancer and chronically inflamed cells and tissues. Extracellular vesicles play pivotal roles in these pathological processes and carry biomolecules that can be detected in many biofluids and may be exploited for diagnostic purposes. Several studies report the effects of hypoxia on extracellular vesicles’ release, molecular content, and biological functions in disease. This review summarizes the most recent findings in this field, highlighting the areas that warrant further investigation.

Cell-Selective Altered Cargo Properties of Extracellular Vesicles Following In Vitro Exposures to Intermittent Hypoxia

Intermittent hypoxia (IH), a hallmark of obstructive sleep apnea (OSA), is associated with cardiovascular and metabolic dysfunction. However, the mechanisms underlying these morbidities remain poorly delineated. Extracellular vesicles (EVs) mediate intercellular communications, play pivotal roles in a multitude of physiological and pathological processes, and could mediate IH-induced cellular effects. Here, the effects of IH on human primary cells and the release of EVs were examined. Microvascular endothelial cells (HMVEC-d), THP1 monocytes, THP1 macrophages M0, THP1 macrophages M1, THP1 macrophages M2, pre-adipocytes, and differentiated adipocytes (HAd) were exposed to either room air (RA) or IH for 24 h. Secreted EVs were isolated and characterized using transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. The effects of each of the cell-derived EVs on endothelial cell (EC) monolayer barrier integrity, on naïve THP1 macrophage polarity, and on adipocyte insulin sensitivity were also evaluated. IH did not alter EVs cell quantal release, but IH-EVs derived from HMVEC-d (p < 0.01), THP1 M0 (p < 0.01) and HAd (p < 0.05) significantly disrupted HMVEC-d monolayer integrity, particularly after H₂O₂ pre-conditioning. IH-EVs from HMVEC-d and THP1 M0 elicited M2-polarity changes did not alter insulin sensitivity responses. IH induces cell-selective changes in EVs cargo, which primarily seem to target the emergence of endothelial dysfunction. Thus, changes in EVs cargo from selected cell sources in vivo may play causal roles in some of the adverse outcomes associated with OSA.

Extracellular vesicle microRNA cargoes from intermittent hypoxia-exposed cardiomyocytes and their effect on endothelium

Intermittent hypoxia (IH), a main characteristic of obstructive sleep apnea (OSA) syndrome, is an independent risk factor of cardiovascular complications. However, the mechanism has not been fully elucidated. Growing evidence has revealed alterations of extracellular vesicle (EV) contents, mostly miRNAs, playing a pathogenic role in cardiovascular complications. In current study, we attempt to compare the disparity of myocardial EV miRNA components after IH or normoxia treatment and determine whether EVs from IH-treated cardiomyocytes could affect endothelial function. 63 differentially expressed miRNAs were identified in EVs from IH-exposed cardiomyocytes by miRNA chip assay. Among them, 16 miRNAs with homologous sequence in mouse and human were verified by qPCR assay and 11 miRNAs were proved with the same tendency as miRNA chip assay. KEGG predicted that the function of differentially expressed miRNA was enriched to Akt signaling pathway. Notably, EVs from IH-exposed cardiomyocytes dramatically impaired endothelial-dependent relaxation and inhibited Akt/eNOS expression in endothelial cells. This study provides the first evidence that IH significantly alters myocardial EV miRNA composition and reveals a novel role of myocardial EVs in endothelial function under IH status, which will help to understand the OSA- or IH-related endothelial dysfunction from a new scope.

An Update on Obstructive Sleep Apnea for Atherosclerosis: Mechanism, Diagnosis, and Treatment

The occurrence and development of atherosclerosis could be influenced by intermittent hypoxia. Obstructive sleep apnea (OSA), characterized by intermittent hypoxia, is world-wide prevalence with increasing morbidity and mortality rates. Researches remain focused on the study of its mechanism and improvement of diagnosis and treatment. However, the underlying mechanism is complex, and the best practice for OSA diagnosis and treatment considering atherosclerosis and related cardiovascular diseases is still debatable. In this review, we provided an update on research in OSA in the last 5 years with regard to atherosclerosis. The processes of inflammation, oxidative stress, autonomic nervous system activation, vascular dysfunction, platelet activation, metabolite dysfunction, small molecule RNA regulation, and the cardioprotective occurrence was discussed. Additionally, improved diagnosis such as, the utilized of portable device, and treatment especially with inconsistent results in continuous positive airway pressure and mandibular advancement devices were illustrated in detail. Therefore, further fundamental and clinical research should be carried out for a better understanding the deep interaction between OSA and atherosclerosis, as well as the suggestion of newer diagnostic and treatment options.

miR-3574 ameliorates intermittent hypoxia-induced cardiomyocyte injury through inhibiting Axin1

Objective: miRNAs play critical roles in the regulation of many cardiovascular diseases. However, its role and potential mechanism in cardiac injury caused by obstructive sleep apnea (OSA) remain poorly elucidated. In the present study, we aimed to investigate the effects of miR-3574 on cardiomyocyte injury under intermittent hypoxia (IH).

Results: We confirmed that IH inhibited cell viability, induced cell apoptosis and suppressed miR-3574 expression in the H9c2. miR-3574 overexpression could ameliorate the effects of IH on the cell viability and cell apoptosis in the H9c2. Axin1 was a target gene of miR-3574, and miR-3574 overexpression reduced the expression of Axin1. miR-3574 could inhibit the IH-induced cardiomyocyte injury via downregulating Axin1. However, Axin1 could partially reverse these effects of miR-3574.

Conclusion: Our study first reveals that miR-3574 could alleviate IH-induced cardiomyocyte injury by targeting Axin1, which may function as a novel and promising therapy target for OSA-associated cardiovascular diseases.

Methods: H9c2 were exposed to IH condition. CCK-8 assay was applied to determine cell viability of H9c2. qRT-PCR was conducted to measure the expression level of mRNA and miRNA. Western blot assay was then performed to detect the protein levels. Finally, we used dual-luciferase reporter assay identify the potential target of miR-3574.

Exosome-Derived Mediators as Potential Biomarkers for Cardiovascular Diseases: A Network Approach

Cardiovascular diseases (CVDs) are widely recognized as the leading cause of mortality worldwide. Despite the advances in clinical management over the past decades, the underlying pathological mechanisms remain largely unknown. Exosomes have drawn the attention of researchers for their relevance in intercellular communication under both physiological and pathological conditions. These vesicles are suggested as complementary prospective biomarkers of CVDs; however, the role of exosomes in CVDs is still not fully elucidated. Here, we performed a literature search on exosomal biogenesis, characteristics, and functions, as well as the different available exosomal isolation techniques. Moreover, aiming to give new insights into the interaction between exosomes and CVDs, network analysis on the role of exosome-derived mediators in coronary artery disease (CAD) and heart failure (HF) was also performed to incorporate the different sources of information. The upregulated exosomal miRNAs miR-133a, miR-208a, miR-1, miR-499-5p, and miR-30a were described for the early diagnosis of acute myocardial infarction, while the exosome-derived miR-192, miR-194, miR-146a, and miR-92b-5p were considered as potential biomarkers for HF development. In CAD patients, upregulated exosomal proteins, including fibrinogen beta/gamma chain, inter-alpha-trypsin inhibitor heavy chain, and alpha-1 antichymotrypsin, were assessed as putative protein biomarkers. From downregulated proteins in CAD patients, albumin, clusterin, and vitamin D-binding protein were considered relevant to assess prognosis. The Vesiclepedia database included miR-133a of exosomal origin upregulated in patients with CAD and the exosomal miR-192, miR-194, and miR-146a upregulated in patients with HF. Additionally, Vesiclepedia included 5 upregulated and 13 downregulated exosomal proteins in patients in CAD. The non-included miRNAs and proteins have not yet been identified in exosomes and can be proposed for further research. This report highlights the need for further studies focusing on the identification and validation of miRNAs and proteins of exosomal origin as biomarkers of CAD and HF, which will enable, using exosomal biomarkers, the guiding of diagnosis/prognosis in CVDs.

MicroRNAs to guide medical decision-making in obstructive sleep apnea: A review

Obstructive sleep apnea (OSA) is a common and frequently underdiagnosed sleep disorder tightly associated with a wide range of morbidities and an elevated risk of the main causes of mortality. This condition represents a major public health concern due to its increasing worldwide prevalence and its serious pathological consequences. Current clinical guidelines support the importance of effective diagnosis and treatment of OSA and emphasize the unmet need for biomarkers to guide medical decision-making. In recent years, the noncoding transcriptome has emerged as a new opportunity for biomarker discovery. In this review, we provide a brief overview of the current understanding of noncoding RNAs, specifically microRNAs (miRNAs). Then, we carefully address the potential role of miRNAs as novel indicators for the management of both pediatric and adult OSA, highlighting their translational applicability, particularly for diagnosis and therapy allocation. Finally, we identify the gaps in the research state-of-art, discuss current methodological and conceptual limitations and propose future key steps and perspectives for the incorporation of miRNAs into routine clinical practice.

Circulating exosomes and gut microbiome induced insulin resistance in mice exposed to intermittent hypoxia: Effects of physical activity

Background

Gut microbiota (GM) contribute to obesity and insulin resistance (IR). Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), promotes IR and alters GM. Since circulating exosomes are implicated in IR, we examined the effects of IH and physical activity (PA) in mice on GM, colonic epithelium permeability, systemic IR, and plasma exosome cargo, and exosome effects on visceral white adipose tissues (vWAT) IR.

Methods

C57BL/6 mice were exposed to IH or room air (RA) for 6 weeks with and without PA (n = 12/group), and GM and systemic IR changes were assessed, as well as the effects of plasma exosomes on naïve adipocyte insulin sensitivity. Fecal microbiota transfers (FMT) were performed in naïve mice (n = 5/group), followed by fecal 16S rRNA sequencing, and systemic IR and exosome-induced effects on adipocyte insulin sensitivity were evaluated.

Findings

Principal coordinate analysis (PCoA) ordinates revealed B-diversity among IH and FMT recipients that accounted for 64% principal component 1 (PC1) and 12.5% (PC2) of total variance. Dominant microbiota families and genera in IH-exposed and FMT-treated were preserved, and IH-exposed GM and IH-FMT induced increased gut permeability. Plasma exosomes from IH-exposed and IH-FMT mice decreased pAKT/AKT responses to exogenous insulin in adipocytes vs. IH+PA or RA FMT-treated mice (p = 0.001).

Interpretation

IH exposures mimicking OSA induce changes in GM, increase gut permeability, and alter plasma exosome cargo, the latter inducing adipocyte dysfunction (increased IR). Furthermore, these alterations improved with PA. Thus, IH leads to perturbations of a singular GM-circulating exosome pathway that disrupts adipocyte homeostasis resulting in metabolic dysfunction, as reflected by IR.

Funding

This study was supported by grants from the National Institutes of Health grants HL130984 and HL140548 and University of Missouri Tier 2 grant. The study has not received any funding or grants from pharmaceutical or other industrial corporations.

Extracellular Vesicles Derived from Intermittent Hypoxia-Treated Red Blood Cells Impair Endothelial Function Through Regulating eNOS Phosphorylation and ET-1 Expression

PURPOSE

Intermittent hypoxia (IH), a main characteristic of obstructive sleep apnea (OSA) syndrome, has been known as a dominant cause of OSA-related endothelial dysfunction and hypertension. However, the underlying mechanism still remains unclear. Extracellular vesicles (EVs), small vesicles secreted by various cells, can be absorbed by endothelial cells and then influence vascular function. The aim of this research is to clarify whether and how EVs shedding from red blood cells (RBCs) are involved in IH-induced endothelial dysfunction.

METHODS

EVs were extracted by ultracentrifugation. After the identification of property and purity, EVs from IH-exposed RBCs (IH REVs) and normoxia-exposed RBCs (NOR REVs) or from OSA and non-OSA patient RBCs were utilized to treat C57BL/6 mouse aortas or human umbilical vein endothelial cells (HUVECs) for mechanistic exploration.

RESULTS

Functional results demonstrated that REVs from OSA patients dramatically impaired endothelium-dependent relaxations (EDRs). Similarly, in vivo and ex vivo studies showed that IH REVs caused significant endothelial dysfunction compared to control group. Further results presented that IH REVs blocked endothelial nitric oxide synthase (eNOS) phosphorylation through inhibiting PI3K/Akt pathway and enhanced endothelin-1 (ET-1) expression through activating Erk1/2 pathway in endothelial cells. Meanwhile, endothelial dysfunction caused by IH REVs was reversed by Akt activator SC79 as well as Erk kinase inhibitor PD98059, suggesting that PI3K/Akt/eNOS and Erk1/2/ET-1 pathways were implicated in IH REV-induced impaired EDRs.

CONCLUSIONS

This study reveals a novel role of REVs in endothelial dysfunction under IH and dissects the relevant mechanism involved in this process, which will help to establish a comprehensive understanding of OSA or IH-related endothelial dysfunction from a new scope.

Circulating Exosomal miRNAs Signal Circadian Misalignment to Peripheral Metabolic Tissues

Night shift work increases risk of metabolic disorders, particularly obesity and insulin resistance. While the underlying mechanisms are unknown, evidence points to misalignment of peripheral oscillators causing metabolic disturbances. A pathway conveying such misalignment may involve exosome-based intercellular communication. Fourteen volunteers were assigned to a simulated day shift (DS) or night shift (NS) condition. After 3 days on the simulated shift schedule, blood samples were collected during a 24-h constant routine protocol. Exosomes were isolated from the plasma samples from each of the blood draws. Exosomes were added to naïve differentiated adipocytes, and insulin-induced pAkt/Akt expression changes were assessed. ChIP-Seq analyses for BMAL1 protein, mRNA microarrays and exosomal miRNA arrays combined with bioinformatics and functional effects of agomirs and antagomirs targeting miRNAs in NS and DS exosomal cargo were examined. Human adipocytes treated with exosomes from the NS condition showed altered Akt phosphorylation responses to insulin in comparison to those treated with exosomes from the DS condition. BMAL1 ChIP-Seq of exosome-treated adipocytes showed 42,037 binding sites in the DS condition and 5538 sites in the NS condition, with a large proportion of BMAL1 targets including genes encoding for metabolic regulators. A significant and restricted miRNA exosomal signature emerged after exposure to the NS condition. Among the exosomal miRNAs regulated differentially after 3 days of simulated NS versus DS, proof-of-concept validation of circadian misalignment signaling was demonstrated with hsa-mir-3614-5p. Exosomes from the NS condition markedly altered expression of key genes related to circadian rhythm in several cultured cell types, including adipocytes, myocytes, and hepatocytes, along with significant changes in 29 genes and downstream gene network interactions. Our results indicate that a simulated NS schedule leads to changes in exosomal cargo in the circulation. These changes promote reduction of insulin sensitivity of adipocytes in vitro and alter the expression of core clock genes in peripheral tissues. Circulating exosomal miRNAs may play an important role in metabolic dysfunction in NS workers by serving as messengers of circadian misalignment to peripheral tissues.

Cardiovascular morbidities of obstructive sleep apnea and the role of circulating extracellular vesicles

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway collapse during sleep resulting in impaired blood gas exchange, namely intermittent hypoxia (IH) and hypercapnia, fragmented sleep (SF), increased oxidative stress and systemic inflammation. Among a myriad of potential associated morbidities, OSA has been particularly implicated as mechanistically contributing to the prevalence and severity of cardiovascular diseases (CVD). However, the benefits of continuous positive airway pressure (CPAP), which is generally employed in OSA treatment, to either prevent or improve CVD outcomes remain unconvincing, suggesting that the pathophysiological mechanisms underlying the incremental CVD risk associated with OSA are not clearly understood. One of the challenges in development of non-invasive diagnostic assays is the ability to identify clinically and mechanistically relevant biomarkers. Circulating extracellular vesicles (EVs) and their cargos reflect underlying changes in cellular homeostasis and can provide insights into how cells and systems cope with physiological perturbations by virtue of the identity and abundance of miRNAs, mRNAs, proteins, and lipids that are packaged in the EVs under normal as well as diseased states, such as OSA. EVs can not only provide unique insights into coordinated cellular responses at the organ or systemic level, but can also serve as reporters of the effects of OSA in CVD, either by their properties enabling regeneration and repair of injured vascular cells or by damaging them. Here, we highlight recent progress in the pathological CVD consequences of OSA, and explore the putative roles of EVs in OSA-associated CVD, along with emerging diagnostic and therapeutic opportunities.

The reviews of this paper are available via the supplemental material section.

Advances and challenges in pursuing biomarkers for obstructive sleep apnea: Implications for the cardiovascular risk

Obstructive sleep apnea (OSA) is a common clinical condition associated with increased cardiovascular morbidity and mortality. Recent evidence from clinical studies and animal models suggest that OSA can promote cardiovascular disease by inducing autonomic, hemodynamic, inflammatory and metabolic dysregulation. However, most of the evidence addressing hard endpoints in humans is derived from observational studies. Several challenges have been noted in the pursuit of a comprehensive knowledge base about the impact of OSA including: 1) the precise mechanisms by which OSA causes metabolic and cardiovascular consequences are not clear, which limits our current ability to address potential targets in OSA; 2) several patients with OSA, even with severe forms, present with no or mild daytime symptoms. Beyond the obvious challenges for obtaining good adherence for conventional OSA treatments, there is evidence that symptomatic vs. asymptomatic patients with OSA do not necessarily have the same metabolic and cardiovascular outcomes; and 3) the cardiovascular response to OSA treatment may vary even in those patients with good adherence. In this scenario, there is an obvious need to develop biomarkers in the OSA research area. This review focuses on describing the advances that have occurred so far in exploring potential OSA biomarkers with clear emphasis for the cardiovascular risk. Particular attention will be devoted to discuss molecular biomarkers including the potential role of microRNAs, proteomics and metabolomics. We also discuss the major challenges and perspectives in this growing research field.

How hypoxia regulate exosomes in ischemic diseases and cancer microenvironment?

Exosomes, as natural occurring vesicles, play highly important roles in the behavior and fate of ischemic diseases and different tumors. Secretion, composition, and function of exosomes are remarkably influenced by hypoxia in ischemic diseases and tumor microenvironment. Exosomes secreted from hypoxic cells affect development, growth, angiogenesis, and progression in ischemic diseases and tumors through a variety of signaling pathways. In this review article, we discuss how hypoxia affects the quantity and quality of exosomes, and review the mechanisms by which hypoxic cell-derived exosomes regulate ischemic cell behaviors in both cancerous and noncancerous cells.

Plasma exosomes in OSA patients promote endothelial senescence: effect of long-term adherent continuous positive airway pressure

Obstructive sleep apnea (OSA) is associated with increased risk for end-organ morbidities, which can collectively be viewed as accelerated aging. Vascular senescence is an important contributor to end-organ dysfunction. Exosomes are released ubiquitously into the circulation, and transfer their cargo to target cells facilitating physiological and pathological processes. Plasma exosomes from 15 patients with polysomnographically diagnosed OSA at baseline (OSA-T1) after 12 months of adherent continuous positive airway pressure (CPAP) treatment (OSA-T2), 13 untreated OSA patients at 12-month intervals (OSA-NT1, OSA-NT2), and 12 controls (CO1 and CO2) were applied on naïve human microvascular endothelialcells-dermal (HMVEC-d). Expression of several senescence gene markers including p16 (CDKN2A), SIRT1, and SIRT6 and immunostaining for β-galactosidase activity (x-gal) were performed. Endothelial cells were also exposed to intermittent hypoxia (IH) or normoxia (RA) or treated with hydrogen peroxide (H2O2), stained with x-gal and subjected to qRT-PCR. Exosomes from OSA-T1, OSA-NT1, and OSA-NT2 induced significant increases in x-gal staining compared to OSA-T2, CO1, and CO2 (p-value < 0.01). p16 expression was significantly increased (p < 0.01), while SIRT1 and SIRT6 expression levels were decreased (p < 0.02 and p < 0.009). Endothelial cells exposed to IH or to H2O2 showed significant increases in x-gal staining (p < 0.001) and in senescence gene expression. Circulating exosomes in untreated OSA induce marked and significant increases in senescence of naïve endothelial cells, which are only partially reversible upon long-term adherent CPAP treatment. Furthermore, endothelial cells exposed to IH or H2O2 also elicit similar responses. Thus, OSA either directly or indirectly via exosomes may initiate and exacerbate cellular aging, possibly via oxidative stress-related pathways.

Circulating plasma exosomes in obstructive sleep apnoea and reverse dipping blood pressure

BACKGROUND

Obstructive sleep apnoea (OSA) increases the risk of an abnormal nondipping 24 h blood pressure profile, an independent risk factor for cardiovascular disease (CVD). We examined differential exosomal microRNA (miRNA) expression in untreated OSA patients with normal dipping blood pressure (NDBP) and reverse dipping blood pressure (RDBP), an extreme form of nondipping, to understand the mechanisms underlying nondipping blood pressure in OSA.

METHODS

46 patients (15 RDBP versus 31 NDBP) matched for OSA severity (respiratory event index 32.6±22.5 versus 32.2±18.1 events·h^-1; p=0.9), age (54.8±12.9 versus 49±9.9 years; p=0.09) and body mass index (36.2±6.6 versus 34.4±6.8 kg·m^-2; p=0.4) were included. Plasma exosomes were characterised by flow cytometry and functional in vitro reporter assays were conducted on cultured endothelial cells. Exosome miRNA cargo was profiled with microarrays followed by bioinformatics analyses.

RESULTS

Exosomes from RDBP patients increased the permeability of endothelial cell tight junctions and adhesion molecule expression. Principal component analyses of miRNA array data showed strict separation and identification of the two groups. A restricted and validated signature of exosomal miRNAs was identified in the RDBP versus NDBP group. Their predicted target genes involved phosphatidylinositol 3-kinase-Akt (p=0.004), Ras (p=3.42E-05), Wnt (p=0.003) and hypoxia inducible factor-1 signalling (p=0.04), inflammatory mediator regulation of transient receptor potential channels (p=0.01), and several cancer-related pathways.

CONCLUSIONS

Patients with RDBP have altered miRNA cargoes in circulating exosomes that invoke in vitro endothelial dysfunction. A selected number of circulating exosomal miRNAs play an important role in abnormal circadian regulation of blood pressure and may provide prognostic biomarkers of CVD risk in OSA.

Non-Exosomal and Exosomal Circulatory MicroRNAs: Which Are More Valid as Biomarkers?

MicroRNAs (miRNAs) are a group of small non-coding RNAs with approximately 19–25 nucleotides that are involved in regulating a range of developmental and physiological processes. Non-exosomal circulating and exosomal miRNAs have also been proposed to be useful in diagnostics as biomarkers for diseases and different types of cancer. In this review, the quantity of miRNAs and of reliable experimental data analyses of miRNAs that come from exosomal and non-exosomal sources are discussed from the perspective of their use as biomarkers for cancer and other diseases, including viral infections, nervous system disorders, cardiovascular disorders, and diabetes. We summarize other research findings regarding the use of miRNA from these two sources as biomarkers in diagnostics and clinical use. The challenges in using miRNA from these two sources in cancer and disease diagnostics are evaluated and discussed. Validation of specific miRNA signatures as biomarkers is a critical milestone in diagnostics.

Obstructive Sleep Apnea, Hypertension, and Cardiovascular Risk: Epidemiology, Pathophysiology, and Management

PURPOSE OF REVIEW

Given the rising prevalence of obstructive sleep apnea (OSA), we aimed to review the epidemiologic and pathophysiologic relationship of OSA, hypertension, and cardiovascular disease, and to summarize recent advances in the treatment of OSA.

RECENT FINDINGS

OSA is associated with an elevated risk of hypertension and cardiovascular disease. Several pathophysiologic factors contribute to the relationship between OSA and vascular risk, including neurohormonal dysregulation, endothelial dysfunction, and inflammation. While CPAP reduces blood pressure, it has not been demonstrated to reduce cardiovascular risk. The combination of CPAP and weight loss has a synergistic effect on blood pressure and several metabolic parameters. Adherence to CPAP is poor across studies, potentially contributing to the attenuation of perceived cardiovascular benefit from CPAP therapy. A greater emphasis on adherence to CPAP and the combination of CPAP and weight loss are central to reducing cardiovascular risk among individuals with OSA.