Novel proteins associated with chronic intermittent hypoxia and obstructive sleep apnea: From rat model to clinical evidence

In-depth proteomics and Phosphoproteomics reveal biomarkers and molecular pathways of chronic intermittent hypoxia in mice

Obstructive sleep apnea (OSA) syndrome is characterized by Chronic Intermittent Hypoxia (CIH). In this study, we employed Data-independent acquisition (DIA) Mass Spectrometry to conduct comprehensive proteomic and phosphoproteomic profiling of a murine model subjected to Chronic Intermittent Hypoxia (CIH), a model we had previously established. Utilizing three CIH and three normal control genioglossus samples, we gathered valuable insights into the molecular alterations associated with CIH. Our analyses identified a total of 4576 protein groups and 13,867 phosphosites. Differential analysis of the proteomic data highlighted a significant upregulation of Ras signaling (Egf, Ngf, and Fyb1) and calcium signaling (Tnn, Thbs4, and Ppp2r2d) in CIH samples, contrasting with a notable decrease in oxidative phosphorylation (Atp5mf, Atp5me, and Atp5mg). Additionally, we observed a substantial increase in the phosphorylation of PI3K-AKT signaling (Ptk2_Y861, Mapk3_T203, and Eif4b_S230) and HIF-1 signaling (Gapdh_S208, Eno3_T229, and Camk2b_T382) in CIH samples. These findings prompted a deeper investigation into the association of the characterized proteins and phosphoproteins with Obstructive Sleep Apnea (OSA). The comprehensive profiling revealed molecular signatures that may serve as valuable insights into the pathophysiology of chronic intermittent hypoxia and its link to obstructive sleep apnea. Our observations provide a foundation for future research endeavors, offering potential avenues for advancing our understanding and treatment strategies for these conditions. SIGNIFICANCE: The significance of this study lies in its comprehensive exploration of the molecular mechanisms underpinning Chronic Intermittent Hypoxia (CIH), a key feature of Obstructive Sleep Apnea (OSA). By employing Data-independent acquisition (DIA) Mass Spectrometry, this research provides an in-depth proteomic and phosphoproteomic analysis, uncovering critical signaling pathways and molecular alterations associated with CIH. The identification of significant changes in Ras and calcium signaling pathways, along with increased phosphorylation in PI3K-AKT and HIF-1 signaling, offers novel insights into the pathophysiological processes involved in CIH and OSA. These findings not only enhance our understanding of the molecular basis of OSA but also pave the way for the development of targeted therapeutic strategies, ultimately contributing to better management and treatment of OSA and related conditions.

Intermittent Hypoxia Impairs Cognitive Function and Promotes Mitophagy and Lysophagy in Obstructive Sleep Apnea-Hypopnea Syndrome Rat Model

Autophagy regulates intermittent hypoxia (IH)-induced obstructive sleep apnea-hypopnea syndrome (OSAHS). We investigated the effects of IH and its withdrawal on cognitive function, autophagy, and lysophagy in OSAHS. An OSAHS rat model was established, and rats were divided into five groups: normoxia control, IH-4w (4-week IH), IH-6w (6-week IH), IH-8w (8-week IH), and IH-8w + 4w (8-week IH and 4-week normoxia). The cognitive behavior; mitochondrial and lysosomal morphology of the hippocampal tissue; mitochondrial respiratory function, permeability, and membrane potential; lysosomal function; autophagy- and lysophagy-related protein levels; and hypoxia-associated autophagy gene expression in rats were assessed. The cognitive function of rats in the IH-4w, IH-6w, and IH-8w groups was significantly impaired. In IH-8w cells, mitochondrial function was damaged with swollen morphology and decreased quantity, respiration, permeability, and membrane potential, along with significantly increased mitophagy-related protein ATG5 and LC3II/LC3 levels and decreased p62 levels. Expression of hypoxia-associated autophagy genes Becn1, Hif1, Bnip3, Bnip3l, and Fundc1 was significantly higher in the IH-8w group. Significantly increased LAMP2, CTSB, and ACP2 levels in IH-8w cells further indicated impaired lysosomal function. Lysophagy-related protein LAMP1, LC3II/LC3I, and TFEB levels were significantly increased in the IH-8w group, whereas p62 level was significantly decreased. The above listed evidence indicated damage to the mitochondria and lysosomes, as well as stimulation of mitophagy and lysophagy in IH-treatment OSAHS rat model. After withdrawing IH and culturing for 4 weeks in normal conditions, the cognitive function of rats improved, and mitophagy and lysophagy decreased. Our findings indicate that IH impairs cognitive function and promotes mitophagy and lysophagy in an OSAHS rat model, and IH withdrawal recovered the above effects.

Intermittent Hypoxia Promotes TAM-Induced Glycolysis in Laryngeal Cancer Cells via Regulation of HK1 Expression through Activation of ZBTB10

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH), may increase the risk of cancer development and a poor cancer prognosis. TAMs of the M2 phenotype, together with the intermittent hypoxic environment within the tumor, drive tumor aggressiveness. However, the mechanism of TAMs in IH remains unclear. In our study, IH induced the recruitment of macrophages, and IH-induced M2-like TAMs promoted glycolysis in laryngeal cancer cells through hexokinase 1. The hexokinase inhibitor 2-deoxy-D-glucose and HK1 shRNA were applied to verify this finding, confirming that M2-like TAMs enhanced glycolysis in laryngeal cancer cells through HK1 under intermittent hypoxic conditions. Comprehensive RNA-seq analysis disclosed a marked elevation in the expression levels of the transcription factor ZBTB10, while evaluation of a laryngeal cancer patient tissue microarray demonstrated a positive correlation between ZBTB10 and HK1 expression in laryngeal carcinoma. Knockdown of ZBTB10 decreased HK1 expression, and overexpression of ZBTB10 increased HK1 expression in both laryngeal cancer cells and 293T cells. The luciferase reporter assay and Chromatin immunoprecipitation assay confirmed that ZBTB10 directly bound to the promoter region of HK1 and regulated the transcriptional activity of HK1. Finally, the CLEC3B level of the M2 supernatant is significantly higher in the IH group and showed a protumor effect on Hep2 cells. As ZBTB10-mediated regulation of HK1 affects glycolysis in laryngeal cancer, our findings may provide new potential therapeutic targets for laryngeal cancer.

Advances in animal models of obstructive sleep apnea

Animal experiments play an important role in the study of the pathogenesis of human diseases and new methods of diagnosis and treatment. Due to the great differences in the anatomical structure and physiology of the upper airway between animals and humans, there is currently no animal model that can fully simulate the pathological anatomy and pathophysiological characteristics of human obstructive sleep apnea (OSA) patients. Herein, we summarizes the construction methods of several OSA animal models that have been widely used in the studies published in the last 5 years, the advantages and limitations of each model as well as related evaluation techniques are described. This information has potential to provide further guide for the development of OSA related animal experiments.

Hypoxia modeling techniques: A review

Hypoxia is the main cause and effect of a large number of diseases, including the most recent one facing the world, the coronavirus disease (COVID-19). Hypoxia is divided into short-term, long-term, and periodic, it can be the result of diseases, climate change, or living and traveling in the high mountain regions of the world. Since each type of hypoxia can be a cause and a consequence of various physiological changes, the methods for modeling these hypoxias are also different. There are many techniques for modeling hypoxia under experimental conditions. The most common animal for modeling hypoxia is a rat. Hypoxia models (hypoxia simulations) in rats are a tool to study the effect of various conditions on the oxygen supply of the body. These models can provide a necessary information to understand hypoxia and also provide effective treatment, highlighting the importance of various reactions of the body to hypoxia. The main parameters when choosing a model should be reproducibility and the goal that the scientist wants to achieve. Hypoxia in rats can be reproduced both ways exogenously and endogenously. The reason for writing this review was the aim to systematize the models of rats available in the literature in order to facilitate their selection by scientists. The relative strengths and limitations of each model need to be identified and understood in order to evaluate the information obtained from these models and extrapolate these results to humans to develop the necessary generalizations. Despite these problems, animal models have been and remain vital to understanding the mechanisms involved in the development and progression of hypoxia. The eligibility criteria for the selected studies was a comprehensive review of the methods and results obtained from the studies. This made it possible to make generalizations and give recommendations on the application of these methods. The review will assist scientists in choosing an appropriate hypoxia simulation method, as well as assist in interpreting the results obtained with these methods.

Construction of a mitochondrial dysfunction related signature of diagnosed model to obstructive sleep apnea

Background: The molecular mechanisms underlying obstructive sleep apnea (OSA) and its comorbidities may involve mitochondrial dysfunction. However, very little is known about the relationships between mitochondrial dysfunction-related genes and OSA. Methods: Mitochondrial dysfunction-related differentially expressed genes (DEGs) between OSA and control adipose tissue samples were identified using data from the Gene Expression Omnibus database and information on mitochondrial dysfunction-related genes from the GeneCards database. A mitochondrial dysfunction-related signature of diagnostic model was established using least absolute shrinkage and selection operator Cox regression and then verified. Additionally, consensus clustering algorithms were used to conduct an unsupervised cluster analysis. A protein-protein interaction network of the DEGs between the mitochondrial dysfunction-related clusters was constructed using STRING database and the hub genes were identified. Functional analyses, including Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene set enrichment analysis (GSEA), and gene set variation analysis (GSVA), were conducted to explore the mechanisms involved in mitochondrial dysfunction in OSA. Immune cell infiltration analyses were conducted using CIBERSORT and single-sample GSEA (ssGSEA). Results: we established mitochondrial dysfunction related four-gene signature of diagnostic model consisted of NPR3, PDIA3, SLPI, ERAP2, and which could easily distinguish between OSA patients and controls. In addition, based on mitochondrial dysfunction-related gene expression, we identified two clusters among all the samples and three clusters among the OSA samples. A total of 10 hub genes were selected from the PPI network of DEGs between the two mitochondrial dysfunction-related clusters. There were correlations between the 10 hub genes and the 4 diagnostic genes. Enrichment analyses suggested that autophagy, inflammation pathways, and immune pathways are crucial in mitochondrial dysfunction in OSA. Plasma cells and M0 and M1 macrophages were significantly different between the OSA and control samples, while several immune cell types, especially T cells (γ/δ T cells, natural killer T cells, regulatory T cells, and type 17 T helper cells), were significantly different among mitochondrial dysfunction-related clusters of OSA samples. Conclusion: A novel mitochondrial dysfunction-related four-gen signature of diagnostic model was built. The genes are potential biomarkers for OSA and may play important roles in the development of OSA complications.

Disorders of gut microbiota in children with Tetralogy of Fallot

BACKGROUND

Gut microbiota plays an important role in cardiovascular health and disease, including congenital heart disease (CHD). Tetralogy of Fallot (TOF) is the most common form of cyanotic CHD characterized by systemic chronic hypoxia and sustained pressure overload of the right ventricle. It is well-known that hypoxia and pressure overload can affect gut microbiota. However, the effects of TOF on the gut microbiota remain little understood. This study explored the profile of the gut microbiota in children with unrepaired TOF.

METHODS

A total of 12 pediatric patients diagnosed with TOF and 9 healthy age- and gender-matched children were enrolled in this study. Fecal samples were collected from every participant and subjected to 16S rDNA gene sequencing. The raw sequencing data were processed using the Quantitative Insights Into Microbial Ecology pipeline.

RESULTS

A comparison of the gut microbiota revealed that pediatric patients with TOF had developed dysbiosis as reflected by the altered taxonomic composition and impaired functional profile. A total of 14 indicative bacterial genera were identified as differential biomarkers capable of distinguishing between healthy children and TOF patients. Furthermore, functional annotations revealed that the gut microbiota in TOF patients was characterized by increased levels of inflammatory, oxidative, and immune responses, and decreased activities of adaptation, synthesis, and metabolism.

CONCLUSIONS

Pediatric patients with unrepaired TOF have intestinal dysbacteriosis that is characterized by altered taxonomic composition and impaired functional profile. These findings suggested that the interplay between gut microbiota and the host may be dysregulated in patients with TOF.

Silencing MR-1 Protects against Myocardial Injury Induced by Chronic Intermittent Hypoxia by Targeting Nrf2 through Antioxidant Stress and Anti-Inflammation Pathways

BACKGROUND

Patients with obstructive sleep apnea hypopnea syndrome (OSAHS) often have cardiac insufficiency mainly due to hypoxia/reperfusion injury caused by chronic intermittent hypoxia (CIH). Inflammation and oxidative stress are involved in the cardiovascular events of OSAHS patients. Studies have found that myofibrillation regulator-1 (MR-1) participates in the pathological process of OSAHS-induced myocardial injury, but the specific mechanism is still unclear.

METHODS

We used a CIH-induced rat model to simulate the process of OSAHS disease. Indices of myocardial injury, inflammation, and oxidative stress were detected using quantitative PCR and enzyme-linked immunosorbent assay (ELISA). After administration of adenoassociated viral vector (AAV) encoding silencing RNA against MR-1, we examined expression of the classic antioxidant stress pathway protein NF-E2-related factor 2 (Nrf2) using western blotting.

RESULTS

We found that levels of serum inflammatory factors tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 were increased, and we further observed disturbance of the oxidative stress system, in which the content of reactive oxygen species (ROS), superoxide dismutase (SOD), reduced glutathione (GSH), and malondialdehyde (MDA) was enhanced in CIH-induced rats. Subsequently, we detected that expression of Nrf2 and heme oxygenase-1 (HO-1) was slightly increased, while the expression of Kelch-like ECH-associated protein 1 (Keap-1) was significantly increased in the CIH model. Interestingly, after administration of silencing MR-1 AAV, the elevated levels of inflammatory factors were reduced, and the disordered oxidative stress system was corrected. Additionally, the expression of Nrf2 and HO-1 was distinctly increased, but the high expression of Keap-1 was decreased.

CONCLUSIONS

Our research results demonstrate that silencing MR-1 rescued the myocardium the injury from inflammatory and oxidative stress in CIH-induced rats by administration of the Nrf2 signaling pathway.