Redox states of hemoglobin determine left ventricle pressure recovery and activity of mitochondrial complex IV in hypoxic rat hearts

Hemolysis-associated release of hemoglobin induces mitochondrial oxidative phosphorylation (OXPHOS) disturbance and aggravates cell oxidative damage in grass carp (Ctenopharyngodon idella)

The liver is a key site for the removal of cell-free hemin during hemolysis. However, the mechanism underlying liver damage caused by hemolysis in teleost hemolytic disorderss remains unclear. In this study, the hemin incubation of grass carp liver cells (L8824) and phenylhydrazine (PHZ) injection were employed to simulate in vitro and in vivo hemolysis models. The Cell Counting Kit (CCK) assay results of the L8824 cells showed that the hemin caused obvious cell death and exhibited concentration-dependent characteristics. Furthermore, hemin stimulation significantly increased intracellular iron content, markedly enhanced intracellular ROS (reactive oxygen species) production, triggered the activation of genes linked to iron metabolism, and disrupted mitochondrial structural integrity. The quantitative real-time PCR (qRT-PCR) assay and enzyme activity findings indicated that the hemoglobin (Hb) treatment activated the activity and expression of mitochondrial respiratory chain complexes, while the addition of compound inhibitors I, II, and III could rescue hemin-induced cell death. Finally, a hemolysis model was established via intraperitoneal injection of PHZ in the grass carp. Histopathological analysis and in vivo transcriptome data showed that PHZ-induced hemolysis resulted in liver inflammation and iron and collagen fiber buildup. Additionally, immunofluorescence and immunohistochemical data indicated it enhanced the ROS generation, malondialdehyde (MDA), and 4-hydroxy-2-nonenal (4-HNE), destroyed the mitochondria, and up-regulated the transcription of mitochondrial respiratory chain complexes. In summary, the cell-free Hb released during hemolysis increased iron deposition, disrupted iron metabolism homeostasis, and caused oxidative stress. Consequently, this destroyed mitochondria function and ultimately exacerbated cell death.

Exploring the Molecular Interplay Between Oxygen Transport, Cellular Oxygen Sensing, and Mitochondrial Respiration

Significance: The mitochondria play a key role in maintaining oxygen homeostasis under normal oxygen tension (normoxia) and during oxygen deprivation (hypoxia). This is a critical balancing act between the oxygen content of the blood, the tissue oxygen sensing mechanisms, and the mitochondria, which ultimately consume most oxygen for energy production. Recent Advances: We describe the well-defined role of the mitochondria in oxygen metabolism with a special focus on the impact on blood physiology and pathophysiology. Critical Issues: Fundamental questions remain regarding the impact of mitochondrial responses to changes in overall blood oxygen content under normoxic and hypoxic states and in the case of impaired oxygen sensing in various cardiovascular and pulmonary complications including blood disorders involving hemolysis and hemoglobin toxicity, ischemia reperfusion, and even in COVID-19 disease. Future Directions: Understanding the nature of the crosstalk among normal homeostatic pathways, oxygen carrying by hemoglobin, utilization of oxygen by the mitochondrial respiratory chain machinery, and oxygen sensing by hypoxia-inducible factor proteins, may provide a target for future therapeutic interventions. Antioxid. Redox Signal. 00, 000-000.

Protective effect and mechanism of low P50 haemoglobin oxygen carrier on isolated rat heart

The protection of the isolated heart is very important in heart transplantation surgery, meanwhile, the ischaemia/reperfusion (I/R) of the isolated heart is the main cause of its damage. A timely supply of oxygen can significantly improve the prevention of myocardial ischaemia, however, the cardioprotective solution does not have an oxygen supply function. Haemoglobin Based on Oxygen Carriers (HBOCs) is a kind of nano-oxygen drug, which can effectively and timely supply oxygen to hypoxic organs and tissues. However, the oxygen-carrying and releasing capacity (P50) is different with different HBOCs. The aim of our study was to investigate whether STS (a kind of cardioprotective solution, St Thomas Solution) +different P50 HBOCs provide superior myocardial protection and decrease myocardial injury compared to only STS in rats Langendorff isolated heart perfusion model. The results showed that STS + HBOCs can improve cardiac function at 37 °C for 35 min and 120 min, and reduce myocardial infarctions, pathological changes, and apoptosis of cardiomyocytes, and the STS + low P50 HBOCs is more effective than the other two higher P50 HBOCs. We further demonstrated the outstanding protective effect of STS + low P50 HBOCs on cardiac function, reducing myocardial infarctions and apoptosis of cardiomyocytes in rat Langendorff isolated heart perfusion model.

Oxidation reactions of cellular and acellular hemoglobins: Implications for human health

Oxygen reversibly binds to the redox active iron, a transition metal in human Hemoglobin (Hb), which subsequently undergoes oxidation in air. This process is akin to iron rusting in non-biological systems. This results in the formation of non-oxygen carrying methemoglobin (ferric) (Fe3+) and reactive oxygen species (ROS). In circulating red blood cells (RBCs), Hb remains largely in the ferrous functional form (HbF2+) throughout the RBC's lifespan due to the presence of effective enzymatic and non-enzymatic proteins that keep the levels of metHb to a minimum (1%-3%). In biological systems Hb is viewed as a Fenton reagent where oxidative toxicity is attributed to the formation of a highly reactive hydroxyl radical (OH•) generated by the reaction between Hb's iron (Fe2+) and hydrogen peroxide (H2O2). However, recent research on both cellular and acellular Hbs revealed that the protein engages in enzymatic-like activity when challenged with H2O2, resulting in the formation of a highly reactive ferryl heme (Fe4+) that can target other biological molecules before it self-destructs. Accumulating evidence from several in vitro and in vivo studies are summarized in this review to show that Hb's pseudoperoxidase activity is physiologically more dominant than the Fenton reaction and it plays a pivotal role in the pathophysiology of several blood disorders, storage lesions associated with old blood, and in the toxicity associated with the infusion of Hb-derived oxygen therapeutics.