Mitochondrial ferritin expression in human macrophages is facilitated by thrombin-mediated cleavage under hypoxia

PAR1 inhibition sensitizes HPV-negative HNSCC cells to ferroptosis through inhibition of the STAT3-mediated regulation of iron and lipid metabolic pathways

Ferroptosis, a cell death mechanism characterized by the accumulation of lipid peroxides and subsequent membrane disruption, is emerging as a promising strategy for cancer treatment. However, many tumors, including head and neck squamous cell carcinoma (HNSCC), show resistance to ferroptosis, which reduces its therapeutic effect. Protease-activated receptors (PARs) are highly expressed in many tumors and are closely associated with tumor progression. Our study showed that the expression of protease-activated receptor 1 (PAR1) was downregulated during ferroptosis in HPV-negative HNSCC. Further studies showed that downregulation of PAR1 expression could enhance the therapeutic effect of Erastin on HPV-negative HNSCC, where PAR1 regulated the expression levels of SLC7A11, GPX4, and FTH1. In addition, we found that PAR1 activated the JAK2/STAT3 pathway in a Rac-1-dependent manner and identified STAT3 as a critical transcription factor in PAR1-mediated HPV-negative HNSCC progression and ferroptosis regulation. Inhibition of STAT3 expression attenuated the tumorigenicity of PAR1. It is worth noting that the PAR1 small molecule inhibitor Vorapaxar can further enhance the therapeutic effect of Erastin on HPV-negative HNSCC. Therefore, we propose that PAR1 participates in the progression of HPV-negative HNSCC through STAT3 and reduces the sensitivity of HPV-negative HNSCC to ferroptosis, providing a new perspective for discovering ferroptosis regulatory factors.

Angiotensin type 1 and type 2 receptors-induced mitochondrial dysfunction promotes ferroptosis in cardiomyocytes

Previous studies suggest that ferroptosis is involved in cardiovascular diseases. The aim of the present study is to investigate the causal relationship between angiotensin II type 1 and type 2 receptors (AT1/2R) activities and mitochondrial dysfunction in induction of cardiomyocyte ferroptosis. Human AC16 cardiomyocytes were first pre-treated with an AT1/2R blockers, before stimulated with angiotensin II (Ang II) for 24 h. The redox status of the cardiomyocytes were assessed by measuring the cellular malondialdehyde (MDA), superoxide dismutase (SOD), and Nicotinamide-adenine dinucleotide phosphate, (NADPH) levels using biochemical methods. Mitochondrial reactive oxygen specifics (mitROS), mitochondrial memebrane potential, and Fe2+ levels were determined using flow cytometry. The signaling pathways, including the glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1), sirtuin1, and ferroptosis suppressor protein 1 (FSP1)-coenzyme Q10 (CoQ10) pathways, were evaluated using western blotting. Our results demonstrated that Ang II significantly elevated the levels of MDA, Fe2+, mitoROS, and FtMt and markedly reduced SOD, NADPH, mitochondrial membrane potential, GPX4, HO-1, Sirt1, SFXN1, Nrf2, and FSP1 levels in cardiomyocyte, which were reversed by blockade of AT1/2R. Our results suggest that AT1/2R signaling can induce myocardial ferroptosis by impairing mitochondrial function via multiple signaling pathways, including the cyst (e)ine /GSH/GPX4 axis and FSP1/coenzyme Q10 (CoQ10) axis.

Inflammation in a ferroptotic environment

Ferroptosis is an iron-dependent form of cell death, which finally culminates in lipid peroxidation and membrane damage. During the past decade, the interest in ferroptosis increased substantially and various regulatory components were discovered. The role of ferroptosis during inflammation and its impact on different immune cell populations is still under debate. Activation of inflammatory pathways such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and hypoxia inducible factors (HIFs) are known to alter the ability of cells to undergo ferroptosis and are closely connected to iron metabolism. During inflammation, iron regulatory systems fundamentally change and cells such as macrophages and neutrophils adapt their metabolism towards iron sequestering phenotypes. In this review, we discuss how ferroptosis alters inflammatory pathways and how iron metabolism under inflammatory conditions affects immune cell ferroptosis.

Newly uncovered biochemical and functional aspects of ferritin

Iron homeostasis is strictly regulated at both the systemic and cellular levels by complex mechanisms because of its indispensability and toxicity. Among the various iron-regulatory proteins, ferritin is the earliest discovered regulator of iron metabolism and is a molecule that safely retains excess intracellular iron in the cores of its shells. Two types of ferritin, cytosolic ferritin and mitochondrial ferritin (FTMT), have been identified in a range of organisms from plants to humans. FTMT was identified approximately 60 years after the discovery of cytosolic ferritin. Cytosolic ferritin expression is regulated in an iron-responsive manner. Recently, the molecular mechanisms of iron-dependent degradation of cytosolic ferritin or its secretion into serum have been clarified. FTMT, which shares a high degree of sequence homology with cytosolic ferritin, has distinct functions and is regulated in different ways from cytosolic ferritin. Although knowledge of the physiological role of FTMT is still incomplete, recent studies have shed light on the function and regulation of FTMT. The accumulating biological evidence of both ferritins has made it possible to deepen our knowledge about iron metabolism and its significance in diseases. In this review, we discuss the biological properties of both ferritins, focusing on their newly uncovered behaviors.

Ferroptosis Regulated by Hypoxia in Cells

Ferroptosis is an oxidative damage-related, iron-dependent regulated cell death with intracellular lipid peroxide accumulation, which is associated with many physiological and pathological processes. It exhibits unique features that are morphologically, biochemically, and immunologically distinct from other regulated cell death forms. Ferroptosis is regulated by iron metabolism, lipid metabolism, anti-oxidant defense systems, as well as various signal pathways. Hypoxia, which is found in a group of physiological and pathological conditions, can affect multiple cellular functions by activation of the hypoxia-inducible factor (HIF) signaling and other mechanisms. Emerging evidence demonstrated that hypoxia regulates ferroptosis in certain cell types and conditions. In this review, we summarize the basic mechanisms and regulations of ferroptosis and hypoxia, as well as the regulation of ferroptosis by hypoxia in physiological and pathological conditions, which may contribute to the numerous diseases therapies.