Hypoxia Inducible Factors as Central Players in the Pathogenesis and Pathophysiology of Cardiovascular Diseases

Effects of Hypoxia and Reoxygenation on Metabolic Profiles of Cardiomyocytes

In vitro cellular models provide valuable insights into the adaptive biochemical mechanisms triggered by cells to cope with the stress situation induced by hypoxia and reoxygenation cycles. The first biological data generated in studies based on this micrometric life-scale has the potential to provide us a global overview about the main biochemical phenomena presented in some reported preconditioning therapies in life-scale of higher dimensions. Thus, in this study, a cell incubator was designed and manufactured to produce a cellular model of heart hypoxia followed by reoxygenation (HfR) through consecutive repetitions of hypoxia-normoxia gas exchange. Samples of cellular extracts and culture media were obtained from non-proliferative cardiomyocytes (CMs) cultivated under challenging HfR (stressed CMs) and regular cultivation (unstressed CMs) in rounds of four days for each case. Metabolomic based on proton magnetic resonance spectroscopy (1H-MRS) was used as an analytical approach to identify and quantify the metabolomes of these samples, the endo- and exo-metabolome. Despite the stressed CMs presented over 90% higher cellular death rate compared to the unstressed CMs, the metabolic profiles indicates that the surviving cells up-regulate their amino acid metabolism either by active protein degradation or by the consumption of culture media components to increase coenzyme A-dependent metabolic pathways. This cell auto-regulation mechanism could be well characterized in the first two days when the difference smears off under once the metabolomes become similar. The metabolic adaptations of stressed CMs identified the relevance of the cyclic oxidation/reduction reactions of nicotinamide adenine dinucleotide phosphate molecules, NADP+/NADPH, and the increased tricarboxylic acid cycle activity in an environment overloaded with such a powerful antioxidant agent to survive an extreme HfR challenge. Thus, the combination of cellular models based on CMs, investigative methods, such as metabolomic and 1H-MRS, and the instrumental development of hypoxia incubator shown in this work were able to provide the first biochemical evidences behind therapies of gaseous exchanges paving the way to future assays.

Incidence and Predictors of Cardiac Arrest Among Patients Admitted to the Intensive Care Units of a Comprehensive Specialized Hospital in Central Ethiopia

Background

Cardiac arrest (CA) is a common public health problem. Worldwide, cardiac arrest ranks highly among hospitalised patients' public health concerns, particularly in low-income nations. Data on cardiac arrest in intensive care units in low-income countries are relatively scarce. Determining the incidence and predictors of cardiac arrest among ICU patients will be a very crucial and fruitful clinical practice in resource-limited areas like Ethiopia.

Methods

A retrospective cohort study was conducted by reviewing charts of 422 systematically selected patients admitted to the ICU from 2018 to 2022 in Wachemo University Comprehensive Specialized Hospital. The extraction tool was used for the data collection, Epi-data version 4.6.0 for data entry, and STATA version 14 for data cleaning and analysis. Kaplan-Meier, log rank test, and life table were used to describe the data. The Cox proportional hazard regression model was used for analysis.

Results

The findings of this study revealed that the overall occurrence of cardiac arrest among critically ill ICU patients was 27% (95% CI: 23, 32). The incidence density rate of cardiac arrest among intensive care unit patients was 19.6 per 1000 person-days of observation. In a multivariable analysis, patients with chronic kidney disease, oxygen saturation <90%, delirium, intubation, and patients admitted to the ICU with cardiovascular disease were found to be independent predictors of cardiac arrest in the Intensive Care Unit.

Conclusion

The incidence density rate of cardiac arrest among intensive care unit patients was high. This study also revealed that chronic kidney disease, delirium, intubation, oxygen saturation level below 90% and patients admitted with cardiovascular disease were independent predictors of the occurrence of cardiac arrest among intensive care unit patients. Finally, we recommend that clinician pays attention to those identified as preventable risk factors for early interventions to improve the recovery process of patients in the ICU.

Protein-protein interaction network-based integration of GWAS and functional data for blood pressure regulation analysis

BACKGROUND

It is valuable to analyze the genome-wide association studies (GWAS) data for a complex disease phenotype in the context of the protein-protein interaction (PPI) network, as the related pathophysiology results from the function of interacting polyprotein pathways. The analysis may include the design and curation of a phenotype-specific GWAS meta-database incorporating genotypic and eQTL data linking to PPI and other biological datasets, and the development of systematic workflows for PPI network-based data integration toward protein and pathway prioritization. Here, we pursued this analysis for blood pressure (BP) regulation.

METHODS

The relational scheme of the implemented in Microsoft SQL Server BP-GWAS meta-database enabled the combined storage of: GWAS data and attributes mined from GWAS Catalog and the literature, Ensembl-defined SNP-transcript associations, and GTEx eQTL data. The BP-protein interactome was reconstructed from the PICKLE PPI meta-database, extending the GWAS-deduced network with the shortest paths connecting all GWAS-proteins into one component. The shortest-path intermediates were considered as BP-related. For protein prioritization, we combined a new integrated GWAS-based scoring scheme with two network-based criteria: one considering the protein role in the reconstructed by shortest-path (RbSP) interactome and one novel promoting the common neighbors of GWAS-prioritized proteins. Prioritized proteins were ranked by the number of satisfied criteria.

RESULTS

The meta-database includes 6687 variants linked with 1167 BP-associated protein-coding genes. The GWAS-deduced PPI network includes 1065 proteins, with 672 forming a connected component. The RbSP interactome contains 1443 additional, network-deduced proteins and indicated that essentially all BP-GWAS proteins are at most second neighbors. The prioritized BP-protein set was derived from the union of the most BP-significant by any of the GWAS-based or the network-based criteria. It included 335 proteins, with ~ 2/3 deduced from the BP PPI network extension and 126 prioritized by at least two criteria. ESR1 was the only protein satisfying all three criteria, followed in the top-10 by INSR, PTN11, CDK6, CSK, NOS3, SH2B3, ATP2B1, FES and FINC, satisfying two. Pathway analysis of the RbSP interactome revealed numerous bioprocesses, which are indeed functionally supported as BP-associated, extending our understanding about BP regulation.

CONCLUSIONS

The implemented workflow could be used for other multifactorial diseases.

HIF-2α Controls Expression and Intracellular Trafficking of the α2-Subunit of Na,K-ATPase in Hypoxic H9c2 Cardiomyocytes

The Na,K-ATPase (NKA) pump plays essential roles for optimal function of the heart. NKA activity decreases in necropsy materials from ischemic heart disease, heart failure and in experimental models. Cellular adaptation to hypoxia is regulated by hypoxia-induced transcription factors (HIF); we tested whether HIFs are involved in regulating the expression and intracellular dynamics of the α2-isoform of NKA (α2-NKA). HIF-1α and HIF-2α expression was suppressed in H9c2 cardiomyocytes by adenoviral infection, where cells were kept in 1% O2 for 24 h. The silencing efficiency of HIFs was tested on the mRNA and protein expression. We measured the mRNA expression of α2-NKA in HIF-silenced and hypoxia-exposed cells. The membrane and intracellular expression of α2-NKA was measured after labelling the cell surface with NHS-SS-biotin, immunoprecipitation and Western blotting. Hypoxia increased the mRNA expression of α2-NKA 5-fold compared to normoxic cells in an HIF-2α-sensitive manner. The plasma membrane expression of α2-NKA increased in hypoxia by 2-fold and was fully prevented by HIF-2α silencing. Intracellular expression of α2-NKA was not affected. These results showed for the first time that in hypoxic cardiomyocytes α2-NKA is transcriptionally and translationally regulated by HIF-2α. The molecular mechanism behind this regulation needs further investigation.

Identification and validation of potential hypoxia-related genes associated with coronary artery disease

Introduction: Coronary artery disease (CAD) is one of the most life-threatening cardiovascular emergencies with high mortality and morbidity. Increasing evidence has demonstrated that the degree of hypoxia is closely associated with the development and survival outcomes of CAD patients. However, the role of hypoxia in CAD has not been elucidated. Methods: Based on the GSE113079 microarray dataset and the hypoxia-associated gene collection, differential analysis, machine learning, and validation of the screened hub genes were carried out. Results: In this study, 54 differentially expressed hypoxia-related genes (DE-HRGs), and then 4 hub signature genes (ADM, PPFIA4, FAM162A, and TPBG) were identified based on microarray datasets GSE113079 which including of 93 CAD patients and 48 healthy controls and hypoxia-related gene set. Then, 4 hub genes were also validated in other three CAD related microarray datasets. Through GO and KEGG pathway enrichment analyses, we found three upregulated hub genes (ADM, PPFIA4, TPBG) were strongly correlated with differentially expressed metabolic genes and all the 4 hub genes were mainly enriched in many immune-related biological processes and pathways in CAD. Additionally, 10 immune cell types were found significantly different between the CAD and control groups, especially CD8 T cells, which were apparently essential in cardiovascular disease by immune cell infiltration analysis. Furthermore, we compared the expression of 4 hub genes in 15 cell subtypes in CAD coronary lesions and found that ADM, FAM162A and TPBG were all expressed at higher levels in endothelial cells by single-cell sequencing analysis. Discussion: The study identified four hypoxia genes associated with coronary heart disease. The findings provide more insights into the hypoxia landscape and, potentially, the therapeutic targets of CAD.

Sports Performance and Breathing Rate: What Is the Connection? A Narrative Review on Breathing Strategies

Breathing is a natural and necessary process for humans. At the same time, the respiratory pace and frequency can vary so much, depending on the status of the subject. Specifically, in sports, breathing can have the effect of limiting performance from a physiological point of view, or, on the other hand, breathing can regulate the psychological status of the athletes. Therefore, the aim of this narrative review is to focus on the literature about the physiological and psychological aspects of breathing pace in sports performance, merging these two aspects because they are usually considered split, in order to create a new integrated vision of breathing and sports performance. Voluntary breathing can be divided into a slow or fast pace (VSB and VFB, respectively), and their effects on both the physiological and psychological parameters are very different. VSB can benefit athletes in a variety of ways, not just physically but mentally as well. It can help improve cardiovascular fitness, reduce stress and anxiety, and improve overall health and well-being, allowing athletes to maintain focus and concentration during training and competition. VFB is normal during physical training and competition, but away from training, if it is not voluntary, it can cause feelings of anxiety, panic, dizziness, and lightheadedness and trigger a stress response in the body, affecting the athlete's quality of life. In summary, the role of breathing in the performance of athletes should be considered, although no definitive data are available. The connection between breathing and sports performance is still unclear, but athletes can obtain benefits in focus and concentration using slow breathing strategies.

Hypoxic Stress-Dependent Regulation of Na,K-ATPase in Ischemic Heart Disease

In cardiomyocytes, regular activity of the Na,K-ATPase (NKA) and its Na/K pump activity is essential for maintaining ion gradients, excitability, propagation of action potentials, electro-mechanical coupling, trans-membrane Na⁺ and Ca²⁺ gradients and, thus, contractility. The activity of NKA is impaired in ischemic heart disease and heart failure, which has been attributed to decreased expression of the NKA subunits. Decreased NKA activity leads to intracellular Na⁺ and Ca²⁺ overload, diastolic dysfunction and arrhythmias. One signal likely related to these events is hypoxia, where hypoxia-inducible factors (HIF) play a critical role in the adaptation of cells to low oxygen tension. HIF activity increases in ischemic heart, hypertension, heart failure and cardiac fibrosis; thus, it might contribute to the impaired function of NKA. This review will mainly focus on the regulation of NKA in ischemic heart disease in the context of stressed myocardium and the hypoxia-HIF axis and argue on possible consequences of treatment.

Advances in neovascularization after diabetic ischemia

With the high incidence of diabetes around the world, ischemic complications cause a serious influence on people’s production and living. Neovascularization plays a significant role in its development. Therefore, neovascularization after diabetic ischemia has aroused attention and has become a hot spot in recent years. Neovascularization is divided into angiogenesis represented by atherosclerosis and arteriogenesis characterized by coronary collateral circulation. When mononuclear macrophages successively migrate to the ischemia anoxic zone after ischemia or hypoxia, they induce the secretion of cytokines, such as vascular endothelial growth factor and hypoxia-inducible factor, activate signaling pathways such as classic Wnt and phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) pathways, trigger oxidative stress response, activate endothelial progenitor cells or enter the glycolysis or lactic acid process and promote the formation of new blood vessels, remodeling them into mature blood vessels and restoring blood supply. However, the hypoglycemic condition has different impacts on neovascularization. Consequently, this review aimed to introduce the mechanisms of neovascularization after diabetic ischemia, increase our un-derstanding of diabetic ischemic complications and their therapies and provide more treatment options for clinical practice and effectively relieve patients’ pain. It is believed that in the near future, neovascularization will bring more benefits and hope to patients with diabetes.

Hypoxia-inducible factors: roles in cardiovascular disease progression, prevention, and treatment

Hypoxia-inducible factors (HIF)-1 and HIF-2 are master regulators of oxygen homeostasis that regulate the expression of thousands of genes in order to match O2 supply and demand. A large body of experimental data links HIF activity to protection against multiple disorders affecting the cardiovascular system: ischemic cardiovascular disease (including coronary artery disease and peripheral artery disease), through collateral blood vessel formation and preconditioning phenomena; emphysema; lymphedema; and lung transplant rejection. In these disorders, strategies to increase the expression of one or both HIFs may be of therapeutic utility. Conversely, extensive data link HIFs to the pathogenesis of pulmonary arterial hypertension and drugs that inhibit one or both HIFs may be useful in treating this disease.

Cerebral oxygen metabolic stress is increased in children with sickle cell anemia compared to anemic controls

Patients with sickle cell anemia (SCA) experience cerebral metabolic stress with an increase in oxygen extraction fraction (OEF) to compensate for reduced oxygen carrying capacity due to anemia. It remains unclear if anemia alone drives this metabolic stress. Using MRI, we collected voxel-wise OEF measurements to test our hypothesis that OEF would be elevated in anemic controls without SCA (AC) compared to healthy controls (HC), but OEF would be even higher in SCA compared to AC. Brain MRIs (N = 159) were obtained in 120 participants (34 HC, 27 AC, 59 SCA). While hemoglobin was lower in AC versus HC (p < 0.001), hemoglobin was not different between AC and SCA cohorts (p = 0.459). Whole brain OEF was higher in AC compared to HC (p < 0.001), but lower compared to SCA (p = 0.001). Whole brain OEF remained significantly higher in SCA compared to HC (p = 0.001) while there was no longer a difference between AC versus HC (p = 0.935) in a multivariate model controlling for age and hemoglobin. OEF peaked within the border zone regions of the brain in both SCA and AC cohorts, but the volume of white matter with regionally elevated OEF in AC was smaller (1.8%) than SCA (58.0%). While infarcts colocalized within regions of elevated OEF, more SCA participants had infarcts than AC (p < 0.001). We conclude that children with SCA experience elevated OEF compared to AC and HC after controlling for the impact of anemia, suggesting that there are other pathophysiologic factors besides anemia contributing to cerebral metabolic stress in children with SCA.

Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance

The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.