Protein kinase C binding protein 1 inhibits hypoxia-inducible factor-1 in the heart

The Effect of Hypoxia on Irisin Expression in HL-1 Cardiomyocytes

BACKGROUND/AIM

Cardiovascular diseases (CVD) are the leading cause of death worldwide. In 2019, 523 million people were diagnosed with CVD, with 18.6 million deaths. Improved treatment and diagnostics could reduce CVD's impact. Irisin (Ir) is crucial for heart function and may be a biomarker for heart attack. Ir is a glycoprotein with sugar residues attached to its protein structure. This glycosylation affects Ir stability, solubility, and receptor interactions on target cells. Its secondary structure includes a fibronectin type III domain, essential for its biological functions. Ir helps cardiomyocytes to respond to hypoxia and protects mitochondria. The aim of the study was to determine the FNDC5 gene expression level and the Ir level in HL-1 cardiomyocytes subjected to hypoxia.

MATERIALS AND METHODS

We examined the effect of hypoxia on the expression levels of the FNDC5 gene and those of Ir in mouse cardiomyocytes of the HL-1 cell line. Real-time PCR (RT-PCR) was used to estimate the expression levels of the FNDC5 gene. Western blot and immunofluorescence methods were used to analyze the Ir protein levels.

RESULTS

Analyses showed an increased Ir level in HL-1 cardiomyocytes in response to hypoxia. This is the first study to confirm the presence of Ir in HL-1 cells.

CONCLUSION

The observed increase in Ir expression in murine cardiomyocytes is associated with the hypoxic environment and can be potentially used to diagnose hypoxia and CVD.

Hypothalamic Oxytocin Neuron Activation Attenuates Intermittent Hypoxia-Induced Hypertension and Cardiac Dysfunction in an Animal Model of Sleep Apnea

BACKGROUND

Obstructive sleep apnea is a prevalent and poorly treated cardiovascular disease that leads to hypertension and autonomic imbalance. Recent studies that restore cardiac parasympathetic tone using selective activation of hypothalamic oxytocin neurons have shown beneficial cardiovascular outcomes in animal models of cardiovascular disease. This study aimed to determine if chemogenetic activation of hypothalamic oxytocin neurons in animals with existing obstructive sleep apnea-induced hypertension would reverse or blunt the progression of autonomic and cardiovascular dysfunction.

METHODS

Two groups of rats were exposed to chronic intermittent hypoxia (CIH), a model of obstructive sleep apnea, for 4 weeks to induce hypertension. During an additional 4 weeks of exposure to CIH, 1 group was treated with selective activation of hypothalamic oxytocin neurons while the other group was untreated.

RESULTS

Hypertensive animals exposed to CIH and treated with daily hypothalamic oxytocin neuron activation had lower blood pressure, faster heart rate recovery times after exercise, and improved indices of cardiac function compared with untreated hypertensive animals. Microarray analysis suggested that, compared with treated animals, untreated animals had gene expression profiles associated with cellular stress response activation, hypoxia-inducible factor stabilization, and myocardial extracellular matrix remodeling and fibrosis.

CONCLUSIONS

In animals already presenting with CIH-induced hypertension, chronic activation of hypothalamic oxytocin neurons blunted the progression of hypertension and conferred cardioprotection after an additional 4 weeks of CIH exposure. These results have significant clinical translation for the treatment of cardiovascular disease in patients with obstructive sleep apnea.

Mapping signalling perturbations in myocardial fibrosis via the integrative phosphoproteomic profiling of tissue from diverse sources

Study of the molecular basis of myocardial fibrosis is hampered by limited access to tissues from human patients and by confounding variables associated with sample accessibility, collection, processing and storage. Here, we report an integrative strategy based on mass spectrometry for the phosphoproteomic profiling of normal and fibrotic cardiac tissue obtained from surgical explants from patients with hypertrophic cardiomyopathy, from a transaortic-constriction mouse model of cardiac hypertrophy and fibrosis, and from a heart-on-a-chip model of cardiac fibrosis. We used the integrative approach to map the relative abundance of thousands of proteins, phosphoproteins and phosphorylation sites specific to each tissue source, to identify key signalling pathways driving fibrosis and to screen for anti-fibrotic compounds targeting glycogen synthase kinase 3, which has a consistent role as a key mediator of fibrosis in all three types of tissue specimen. The integrative disease-modelling strategy may reveal new insights into mechanisms of cardiac disease and serve as a test bed for drug screening.

Cardiomyopathy in Thalassemia: Quick Review from Cellular Aspects to Diagnosis and Current Treatments

BACKGROUND

Cardiomyopathic manifestations induced by continuous blood transfusion are the leading cause of death among patients with thalassemia major (TM). Despite introduction of chelation therapy, heart failure after cardiomyopathic manifestations is still a major threat to patients.

METHODS

We performed a search of relevant English-language literature, retrieving publications from the PubMed database and the Google Scholar search engine (2005-2018). We used "thalassemia major", "cardiomyopathy", "iron overload", "cardiac magnetic resonance T2" "chelation therapy", and "iron burden" as keywords.

RESULTS

The results of the studies we found suggest that cardiac hepcidin is a major regulator of iron homeostasis in cardiac tissue. Unlike previous assumptions, the heart appears to have a limited regeneration capability, originating from a small population of hypoxic cardiomyocytes.

CONCLUSIONS

Oxygen levels determine cardiomyocyte gene-expression patterns. Upregulation of cardiac hepcidin in hypoxia preserves cardiomyocytes from forming out of reactive oxygen species catalyzed by free cellular iron in cardiomyocytes. Using the limited regeneration capacity of cardiac cells and gaining further understanding of the cellular aspects of cardiomyopathic manifestations may help health care professionals to develop new therapeutic strategies.

Cytoplasmic upregulation of Cyto c and AIF serve as biomarkers of mechanical asphyxia death

The certification of death due to mechanical asphyxia has been a complex problem in some cases. The use of protein expression to identify mechanical asphyxia death has recently attracted attention. Asphyxia creates an extremely hypoxic environment for cells, which should reactivate the mitochondria in the cells. Cyto c and AIF, located in the mitochondria, are transferred to the cytoplasm under hypoxia to trigger the apoptotic process. Based this phenomenon, we designed the animal asphyxia model and cell hypoxia model to examine whether Cyto c and AIF are expressed in the cytoplasm, and we used human samples to verify the results. We found that the two proteins were detectably expressed in the cytoplasm of mechanical asphyxia groups and were hardly detected in the cytoplasm of other groups. This is a promising finding that may shed light on the precise mechanisms associated with mechanical asphyxia.