Metabolic interaction of hydrogen peroxide and hypoxia in zebrafish fibroblasts

Chronic hypoxia drives the occurrence of ferroptosis in liver of fat greening (Hexagrammos otakii) by activating HIF-1α and promoting iron production

BACKGROUND

Hypoxia caused by global climate change and human activities has become a growing concern eliciting serious effect and damages to aquatic animals. Hexagrammos otakii is usually a victim of hypoxia which caused by high density aquaculture and high nutrient input. The mechanism underlying ferroptosis regulation after hypoxia-stress in liver of H. otakii, however, remains elusive.

METHODS

For a duration of 15 days, expose the H. otakii to low concentrations of dissolved oxygen (3.4 ± 0.2 mg/L). Detecting alterations in the H. otakii liver tissue by chemical staining, immunohistochemistry, and electron microscopy. The expression variations of relevant genes in the liver of the H. otakii were simultaneously detected using Western blot and qPCR. A correlation analysis was performed between HIF-1α and iron ion expression in the liver of H. otakii following hypoxic stress.

RESULTS

In this study, we conducted the whole ferroptosis integrated analysis of H. otakii under chronic hypoxic condition. Reactive oxygen species (ROS) are highly accumulated under the hypoxia treatment (Superoxide Dismutase, SOD; Catalase, CAT), and which results in a significantly enhanced of lipid peroxidation (Lipid Peroxidation, LPO; Malondialdehyde, MDA; Aminotransferase, AST; Alanine aminotransferase, ALT) in liver tissue. The HIF-1α signaling is activated to cope with the hypoxia stress through strategies including changing iron ion concentration (Fe3+ and TFR1) to breaking the oxidation balance (GSH and GSH-Px), and enhancing ferroptosis gene expression (GPX4). The expression of genes related to ferroptosis pathway (DMT1, FTH1, STEAP3, ACSL4, γ-GCS, SLC7A11) is significantly upregulated and associated to the expression of iron and HIF-1α.

CONCLUSIONS

It is demonstrated that the HIF-1α/Fe3+/ROS/GPX4 axis is involved in promoting ferroptosis in fat greening hepatocytes following hypoxia-stress. Ultimately, our findings unveil a process by which hypoxic stress strongly encourages ferroptosis by triggering HIF-1α and boosting iron synthesis.

Real-Time Monitoring of Hydrogen Peroxide Levels in Yeast and Mammalian Cells

Hydrogen peroxide (H2O2) is an important signaling molecule involved in regulating antioxidative transcriptional responses, cellular differentiation, and hypoxia response. H2O2 generation and signaling are highly localized processes. Understanding the dynamics of this molecule inside intact cells with subcompartmental resolution is instrumental to unravel its role in cellular signaling. Different genetically encoded fluorescent sensors have been developed over the last few years that enable such non-disruptive monitoring with high spatiotemporal resolution. In this chapter, we describe the use of these genetically encoded sensors to directly monitor H2O2 dynamics in yeast and cultured mammalian cells.

Toxicity impact of hydrogen peroxide on the fate of zebrafish and antibiotic resistant bacteria

Hydrogen peroxide (H₂O₂) is applied in various environments. It could be present at concentrations ranging from nanomolar to micromolar in a water system. It is produced through pollutants and natural activities. Since few studies have been conducted about the impact of naturally produced H₂O₂ on aquatic organisms, the objective of the present study was to monitor changes in responses of aquatic model organisms such as zebrafish and antibiotic-resistant bacteria to different exogenous H₂O₂ exposure. Increases in exposure concentration and time induced decreases in the perception of zebrafish larvae (up to 69%) and movement of adult zebrafish (average speed, average acceleration, movement distance, and activity time) compared to the control (non-exposed group). In addition, as a function of H₂O₂ exposure concentration (0-100,000 nM) and time, up to 20-fold increase (p = 5.00*10^-6) of lipid peroxidation compared to control was observed. For microorganisms, biofilm, an indirect indicator of resistance to external stressors, was increased up to 68% and gene transfer was increased (p = 2.00*10^-6) by more than 30% after H₂O₂ exposure. These results imply that naturally generated H₂O₂ could adversely affect aquatic environment organisms and public health. Thus, more careful attention is needed for H₂O₂ production in an aquatic system.