Fibroblast growth factor 21 attenuates iron overload-induced liver injury and fibrosis by inhibiting ferroptosis

Formononetin ameliorates ferroptosis-associated fibrosis in renal tubular epithelial cells and in mice with chronic kidney disease by suppressing the Smad3/ATF3/SLC7A11 signaling

AIMS

Chronic kidney disease (CKD) is characterized by interstitial fibrosis, while limited treatment drugs are available. Ferroptosis is a newly identified process that can trigger tubular atrophy and fibrosis. The aim of this study is to investigate the effects of formononetin (FN), a bioflavonoid, on ferroptosis and renal fibrosis.

MAIN METHODS

In vivo experiments, unilateral ureteral obstruction (UUO)- and folic acid (FA, 250 mg/kg)-induced CKD models were constructed in C57BL/6 mice of 6-8 weeks old, followed by the administration with 40 mg/kg/day FN by gavage. For in vitro experiments, ferroptosis was induced with RSL3 or erastin in primary mouse renal tubular epithelial cells (TECs), followed by the addition of indicated concentrations of FN. Then, the levels of ferroptosis and fibrosis were analyzed. The translocation of Smad3, ATF3, and Nrf2 from the cytoplasm to the nucleus was checked by western blotting. The interaction of Smad3 and ATF3 was detected by Co-immunoprecipitation.

KEY FINDINGS

FN dramatically ameliorated tubular injury along with reduced expression of the profibrotic genes including α-SMA, Col1a1, and fibronectin in both two CKD mouse models and RSL3/erastin-treated TECs. Furthermore, FN administration also significantly suppressed ferroptosis, as evidenced by increased expression of SLC7A11 and GPX4, and decreased levels of 4-HNE. In mechanism, FN disrupted the interaction between Smad3 and ATF3, resulting in the blocking of their translocation from the cytoplasm to the nucleus. In addition, FN also promoted the separation of the Nrf2/Keap1 complex and enhanced Nrf2 nuclear accumulation.

SIGNIFICANCE

FN alleviates CKD by impeding ferroptosis-associated fibrosis by suppressing the Smad3/ATF3/SLC7A11 signaling and could serve as a candidate therapeutic drug for CKD.

Blocking P2RX7 Attenuates Ferroptosis in Endothelium and Reduces HG-induced Hemorrhagic Transformation After MCAO by Inhibiting ERK1/2 and P53 Signaling Pathways

Hyperglycemia is a risk factor for poor prognosis after acute ischemic stroke and promote the occurrence of hemorrhagic transformation (HT). The activation of P2RX7 play an important role in endotheliocyte damage and BBB disruption. Ferroptosis is a novel pattern of programmed cell death caused by the accumulation of intracellular iron and lipid peroxidation, resulting in ROS production and cell death. This study is to explore the mechanism of P2RX7 in reducing HT pathogenesis after acute ischemic stroke through regulating endotheliocyte ferroptosis. Male SD rats were performed to establish middle cerebral artery occlusion (MCAO) model injected with 50% high glucose (HG) and HUVECs were subjected to OGD/R treated with high glucose (30 mM) for establishing HT model in vivo and in vitro. P2RX7 inhibitor (BBG), and P2RX7 small interfering RNAs (siRNA) were used to investigate the role of P2RX7 in BBB after MCAO in vivo and OGD/R in vitro, respectively. The neurological deficits, infarct volume, degree of intracranial hemorrhage, integrity of the BBB, immunoblotting, and immunofluorescence were evaluated at 24 h after MCAO. Our study found that the level of P2RX7 was gradually increased after MCAO and/or treated with HG. Our results showed that treatment with HG after MCAO can aggravate neurological deficits, infarct volume, oxidative stress, iron accumulation, and BBB injury in HT model, and HG-induced HUVECs damage. The inhibition of P2RX7 reversed the damage effect of HG, significantly downregulated the expression level of P53, HO-1, and p-ERK1/2 and upregulated the level of SLC7A11 and GPX4, which implicated that P2RX7 inhibition could attenuate oxidative stress and ferroptosis of endothelium in vivo and in vitro. Our data provided evidence that the P2RX7 play an important role in HG-associated oxidative stress, endothelial damage, and BBB disruption, which regulates HG-induced HT by ERK1/2 and P53 signaling pathways after MCAO.

HDAC1 overexpression promoted by METTL3-IGF2BP2 inhibits FGF21 expression in metabolic syndrome-related liver injury

Metabolic syndrome (MetS) represents a cluster of diseases that includes diabetes and insulin resistance. A combination of these metabolic disorders damages liver function. We hypothesized here that histone deacetylase 1 (HDAC1) inhibits fibroblast growth factor 21 (FGF21) expression through histone deacetylation, thereby accentuating liver injury in rats with MetS. MetS rats induced by a high-fat diet were monitored weekly for blood pressure and body weight measurement. The changes of hepatic injury parameters were also measured. The pathological changes in the liver were observed by HE staining and oil red O staining. We found that HDAC1 was increased in the liver of rats with MetS, while sh-HDAC1 reduced blood pressure, body weight, and hepatic injury parameters. Improvement of structural pathological alterations and reduction of lipid deposition were observed after HDAC1 inhibition. Notably, HDAC1 inhibited FGF21 expression through histone deacetylation. The hepatoprotective effects of sh-HDAC1 on rats were reversed by adenovirus-mediated knockdown of FGF21. Moreover, methyltransferase-like 3 (METTL3) mediated the N6-methyladenosine (m6A) modification of HDAC1 mRNA and increased its binding to IGF2BP2. Consistently, sh-METTL3 inhibited HDAC1 and increased FGF21 expression, thereby ameliorating liver injury in MetS rats. This study discovered that HDAC1 is capable of managing liver injury in MetS. Targeting HDAC1 may be an optimal treatment for MetS-related liver injury.

Self-assembled FGF21 nanoparticles alleviate drug-induced acute liver injury

Acetaminophen (N-acetyl-p-aminophenol, APAP) is a common antipyretic agent and analgesic. An overdose of APAP can result in acute liver injury (ALI). Oxidative stress and inflammation are central to liver injury. N-acetylcysteine (NAC), a precursor of glutathione, is used commonly in clinical settings. However, the window of NAC treatment is limited, and more efficacious alternatives must be found. Endogenous cytokines such as fibroblast growth factor (FGF) 21 can improve mitochondrial function while decreasing intracellular oxidative stress and inflammatory responses, thereby exhibiting antioxidant-like effects. In this study, self-assembled nanoparticles comprising chitosan and heparin (CH) were developed to deliver FGF21 (CH-FGF21) to achieve the sustained release of FGF21 and optimize the in vivo distribution of FGF21. CH-FGF21 attenuated the oxidative damage and intracellular inflammation caused by APAP to hepatocytes effectively. In a murine model of APAP-induced hepatotoxicity, CH-FGF21 could alleviate ALI progression and promote the recovery of liver function. These findings demonstrated that a simple assembly of CH nanoparticles carrying FGF21 could be applied for the treatment of liver diseases.

Pharmacological modulation of ferroptosis as a therapeutic target for liver fibrosis

Liver fibrosis, which is characterized by the excessive deposition of extracellular matrix (ECM) materials (primarily fibrillar collagen-I), is an abnormal repair reaction and pathological outcome of chronic liver diseases caused by alcohol abuse, non-alcoholic fatty liver disease, and chronic hepatitis B and C virus infections. Liver fibrosis often progresses to liver cirrhosis and hepatocellular carcinoma. Ferroptosis, characterized by lipid peroxidation, is a form of iron-dependent non-apoptotic cell death, and recent studies have reported that ferroptosis contribute to the development of liver fibrosis. Moreover, several agents have demonstrated therapeutic effects in experimental liver fibrosis models by inducing hepatic stellate cell (HSCs) ferroptosis. This review delineates the specific mechanism by which ferroptosis contributes to the development of liver fibrosis. Specifically, we focused on the different types of therapeutic agents that can induce HSCs ferroptosis and summarize their pharmacological effectiveness for liver fibrosis treatment. We suggest that HSCs ferroptosis may be a potential useful target of novel therapies for preventing and treating liver fibrosis.

Dietary lysolecithin supplementation improves growth performance of weaned piglets via improving nutrients absorption, lipid metabolism, and redox status

Lysolecithin is widely used as emulsifier to improve the digestibility and retention of fat. The current study aimed to investigate the effects of dietary lysolecithin supplementation on growth performance, nutrients absorption, lipid metabolism, and redox status of weaned pigs. A total of 60 weaned piglets were assigned into 2 dietary treatments in a randomized complete block design, receiving basal diet with 0 or 1,000 mg/kg lysolecithin for a period of 28 d. Each dietary treatment had 10 replicates with 3 piglets per replicate. Growth performance and fecal score were monitored during trial. Samples of blood, ileum, and liver tissues were collected and analyzed for serology, intestinal histomorphology, and lipid metabolism-related gene and protein expressions. Dietary lysolecithin supplementation increased average daily gain (+15%, P < 0.05) and tended to increase average daily feed intake (+14%, P = 0.08) in overall experimental period. At final, the average body weight of piglets in lysolecithin group was 10% greater than that of control group (P = 0.09). In addition, dietary lysolecithin supplementation improved the ability of nutrients absorption as indicated by the higher d-xylose level in plasma (P < 0.05). Moreover, piglets from lysolecithin group had higher concentration of high-density lipoprotein (P < 0.05), but lower triglyceride (P < 0.05) in plasma. The inclusion of lysolecithin in diet increased the level of reduced glutathione (GSH) and GSH to oxidized glutathione (GSSG) ratio in plasma and liver (P < 0.05), but attenuated the levels of malondialdehyde and GSSG in ileum (P < 0.05). The upregulation of lipogenesis-related genes (FAS and ACC), downregulation of lipolysis (PNPLA2 and PABP1), and lipid mobilization (PGC-1α and SRIT1) genes were observed in lysolecithin relative to control piglets. Compared with control group, dietary lysolecithin supplementation upregulated protein expressions of GPX4, SREBP1, and LPL in liver and LPL in ileum (P < 0.05). Collectively, our study indicates that dietary lysolecithin supplementation improved growth performance of weaned piglets, which may be associated with the improved nutrients absorption, redox status, and lipid metabolism.

Epigallocatechin gallate alleviates high-fat diet-induced hepatic lipotoxicity by targeting mitochondrial ROS-mediated ferroptosis

Background: Non-alcoholic fatty liver disease (NAFLD) is a chronic advanced liver disease that is highly related to metabolic disorders and induced by a high-fat diet (HFD). Recently, epigallocatechin gallate (EGCG) has been regarded as a protective bioactive polyphenol in green tea that has the ability to protect against non-alcoholic fatty liver disease, but the molecular mechanism remains poorly deciphered. Ferroptosis plays a vital role in the progression of non-alcoholic fatty liver disease, but experimental evidence of ferroptosis inhibition by epigallocatechin gallate is limited. Hence, our study aimed to investigate the effect and mechanisms of epigallocatechin gallate on hepatic ferroptosis to mitigate hepatic injury in high-fat diet-fed mice. Methods: Fifty male C57BL/6 mice were fed either a standard chow diet (SCD), a high-fat diet, or a high-fat diet and administered epigallocatechin gallate or ferrostatin-1 (a ferroptosis-specific inhibitor) for 12 weeks. Liver injury, lipid accumulation, hepatic steatosis, oxidative stress, iron overload, and ferroptosis marker proteins were examined. In vitro, steatotic L-02 cells were used to explore the underlying mechanism. Results: In our research, we found that epigallocatechin gallate notably alleviated liver injury and lipid accumulation, oxidative stress, hepatic steatosis, decreased iron overload and inhibited ferroptosis in a high-fat diet-induced murine model of non-alcoholic fatty liver disease. In vitro experiments, using ferrostatin-1 and a mitochondrial reactive oxygen species (MtROS) scavenger (Mito-TEMPO), we found that epigallocatechin gallate remarkably alleviated oxidative stress and inhibited ferroptosis by reducing the level of mitochondrial reactive oxygen species in steatotic L-02 cells. Conclusion: Taken together, our results revealed that epigallocatechin gallate may exert protective effects on hepatic lipotoxicity by inhibiting mitochondrial reactive oxygen species-mediated hepatic ferroptosis. Findings from our study provide new insight into prevention and treatment strategies for non-alcoholic fatty liver disease pathological processes.

Ferroptosis As a Mechanism for Health Effects of Essential Trace Elements and Potentially Toxic Trace Elements

Ferroptosis is a unique form of programmed cell death driven by iron-dependent phospholipid peroxidation that was proposed in recent years. It plays an important role in processes of various trace element-related diseases and is regulated by redox homeostasis and various cellular metabolic pathways (iron, amino acids, lipids, sugars), as well as disease-related signaling pathways. Some limited pioneering studies have demonstrated ferroptosis as a mechanism for the health effects of essential trace elements and potentially toxic trace elements, with crosstalk among them. The aim of this review is to bring together research articles and identify key direct and indirect evidence regarding essential trace elements (iron, selenium, zinc, copper, chromium, manganese) and potentially toxic trace elements (arsenic, aluminum, mercury) and their possible roles in ferroptosis. Our review may help determine future research priorities and opportunities.

Ferroptosis contribute to hepatic stellate cell activation and liver fibrogenesis

Ferroptosis is a widely known regulator of cell death in connection with the redox state as a consequence of the depletion of glutathione or accumulation of lipid peroxidation. Hepatic stellate cells (HSCs) play a pivotal role in the progression of hepatic fibrosis by increasing the production and secretion of the extracellular matrix. However, the role of ferroptosis in HSC activation and liver fibrogenesis has not been clearly elucidated. The ferroptosis inducer RAS-selective lethal 3 (RSL3) or erastin treatment in HSCs caused cell death. This effect was suppressed only after exposure to ferroptosis inhibitors. We observed induction of ferroptosis by RSL3 treatment in HSCs supported by decreased glutathione peroxidase 4, glutathione deficiency, reactive oxygen species generation, or lipid peroxidation. Interestingly, RSL3 treatment upregulated the expression of plasminogen activator inhibitor-1, a representative fibrogenic marker of HSCs. In addition, treatment with ferroptosis-inducing compounds increased c-JUN phosphorylation and activator protein 1 luciferase activity but did not alter Smad phosphorylation and Smad-binding element luciferase activity. Chronic administration of iron dextran to mice causes ferroptosis of liver in vivo. The expression of fibrosis markers, such as alpha-smooth muscle actin and plasminogen activator inhibitor-1, was increased in the livers of mice with iron accumulation. Hepatic injury accompanying liver fibrosis was observed based on the levels of alanine aminotransferase, aspartate aminotransferase, and hematoxylin and eosin staining. Furthermore, we found that both isolated primary hepatocyte and HSCs undergo ferroptosis. Consistently, cirrhotic liver tissue of patients indicated glutathione peroxidase 4 downregulation in fibrotic region. In conclusion, our results suggest that ferroptosis contribute to HSC activation and the progression of hepatic fibrosis.

Ferroptosis and its role in skeletal muscle diseases

Ferroptosis is characterized by the accumulation of iron and lipid peroxidation products, which regulates physiological and pathological processes in numerous organs and tissues. A growing body of research suggests that ferroptosis is a key causative factor in a variety of skeletal muscle diseases, including sarcopenia, rhabdomyolysis, rhabdomyosarcoma, and exhaustive exercise-induced fatigue. However, the relationship between ferroptosis and various skeletal muscle diseases has not been investigated systematically. This review’s objective is to provide a comprehensive summary of the mechanisms and signaling factors that regulate ferroptosis, including lipid peroxidation, iron/heme, amino acid metabolism, and autophagy. In addition, we tease out the role of ferroptosis in the progression of different skeletal muscle diseases and ferroptosis as a potential target for the treatment of multiple skeletal muscle diseases. This review can provide valuable reference for the research on the pathogenesis of skeletal muscle diseases, as well as for clinical prevention and treatment.

L-Citrulline Supplementation Restrains Ferritinophagy-Mediated Ferroptosis to Alleviate Iron Overload-Induced Thymus Oxidative Damage and Immune Dysfunction

L-citrulline (L-cit) is a key intermediate in the urea cycle and is known to possess antioxidant and anti-inflammation characteristics. However, the role of L-cit in ameliorating oxidative damage and immune dysfunction against iron overload in the thymus remains unclear. This study explored the underlying mechanism of the antioxidant and anti-inflammation qualities of L-cit on iron overload induced in the thymus. We reported that L-cit administration could robustly alleviate thymus histological damage and reduce iron deposition, as evidenced by the elevation of the CD8+ T lymphocyte number and antioxidative capacity. Moreover, the NF-κB pathway, NCOA4-mediated ferritinophagy, and ferroptosis were attenuated. We further demonstrated that L-cit supplementation significantly elevated the mTEC1 cells' viability and reversed LDH activity, iron levels, and lipid peroxidation caused by FAC. Importantly, NCOA4 knockdown could reduce the intracellular cytoplasmic ROS, which probably relied on the Nfr2 activation. The results subsequently indicated that NCOA4-mediated ferritinophagy was required for ferroptosis by showing that NCOA4 knockdown reduced ferroptosis and lipid ROS, accompanied with mitochondrial membrane potential elevation. Intriguingly, L-cit treatment significantly inhibited the NF-κB pathway, which might depend on restraining ferritinophagy-mediated ferroptosis. Overall, this study indicated that L-cit might target ferritinophagy-mediated ferroptosis to exert antioxidant and anti-inflammation capacities, which could be a therapeutic strategy against iron overload-induced thymus oxidative damage and immune dysfunction.

Physiological Effects of Ferroptosis on Organ Fibrosis

Ferroptosis is a new type of programmed cell death with unique morphological, biochemical, and genetic features. From the initial study of histomorphology to the exploration of subcellular organelles and even molecular mechanisms, a net connecting ferroptosis and fibrosis is being woven and formed. Inflammation may be the bridge between both processes. In this review, we will discuss the ferroptosis theory and process and the physiological functions of ferroptosis, followed by a description of the pathological effects and the underlying mechanisms of ferroptosis in the pathogenesis of tumorigenesis, ischemic damage, degenerative lesions, autoimmune diseases, and necroinflammation. We then focus on the role of ferroptosis in the fibrosis process in the liver, lung, kidney, heart, and other organs. Although the molecular mechanism of ferroptosis has been explored extensively in the past few years, many challenges remain to be resolved to translate this information into antifibrotic practice, which is becoming a promising new direction in the field of fibrotic disease prevention and treatment.

TRPM7 channel inhibition attenuates rheumatoid arthritis articular chondrocyte ferroptosis by suppression of the PKCα-NOX4 axis

A role for ferroptosis in articular cartilage destruction associated with rheumatoid arthritis (RA) has not been identified. We previously reported transient receptor potential melastatin 7 (TRPM7) expression was correlated with RA cartilage destruction. Herein, we further characterized a role for TRPM7 in chondrocyte ferroptosis. The expression of TRPM7 was found to be elevated in articular chondrocytes derived from adjuvant arthritis (AA) rats, human RA patients, and cultured chondrocytes treated with the ferroptosis inducer, erastin. TRPM7 knockdown or pharmacological inhibition protected primary rat articular chondrocytes and human chondrocytes (C28/I2 cells) from ferroptosis. Moreover, TRPM7 channel activity was demonstrated to contribute to chondrocyte ferroptosis by elevation of intracellular Ca2+. Mechanistically, the PKCα-NOX4 axis was found to respond to stimulation with erastin, which resulted in TRPM7-mediated chondrocyte ferroptosis. Meanwhile, PKCα was shown to directly bind to NOX4, which could be reduced by TRPM7 channel inhibition. Adeno-associated virus 9-mediated TRPM7 silencing or TRPM7 blockade with 2-APB alleviated articular cartilage destruction in AA rats and inhibited chondrocyte ferroptosis. Collectively, both genetic and pharmacological inhibitions of TRPM7 attenuated articular cartilage damage and chondrocyte ferroptosis via the PKCα-NOX4 axis, suggesting that TRPM7-mediated chondrocyte ferroptosis is a promising target for the prevention and treatment of RA.

Exosomes Derived from Baicalin-Pretreated Mesenchymal Stem Cells Alleviate Hepatocyte Ferroptosis after Acute Liver Injury via the Keap1-NRF2 Pathway

Acute liver injury (ALI) is characterized as a severe metabolic dysfunction caused by extensive damage to liver cells. Ferroptosis is a type of cell death dependent on iron and oxidative stress, which differs from classical cell death, such as apoptosis and necrosis. Ferroptosis has unique morphological features, which mainly include mitochondrial dissolution and mitochondrial outline reduction. Furthermore, the intracellular accumulation of lipid peroxides directly affects the occurrence of ferroptosis. Baicalin, the main compound isolated from Scutellaria baicalensis, has anti-inflammatory and antioxidative effects. Recently, exosomes derived from preconditioned mesenchymal stem cells (MSCs) have shown great potential in the treatment of various diseases including ALI. This study investigates the ability of exosomes derived from baicalin-pretreated MSCs (Ba-Exo) to promote liver function recovery in mice with ALI compared with those without pretreatment. Through in vivo and in vitro experiments, this study demonstrates for the first time that Ba-Exo greatly attenuates D-galactosamine and lipopolysaccharide (D-GaIN/LPS)-induced liver damage and inhibits reactive oxygen species (ROS) production and lipid peroxide-induced ferroptosis. Moreover, P62 was significantly upregulated in Ba-Exo, whereas its downregulation in Ba-Exo counteracted the beneficial effect of Ba-Exo. P62 regulates hepatocyte ferroptosis by activating the Keap1-NRF2 pathway. The beneficial effect of Ba-Exo in inhibiting ferroptosis was also attenuated after the NRF2 pathway was inhibited. Therefore, baicalin pretreatment is an effective and promising approach to optimize the therapeutic efficacy of MSC-derived exosomes in ALI.

An overview of ferroptosis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a public health problem associated with high mortality and high morbidity rates worldwide. Presently, its complex pathophysiology is still unclear, and there is no specific drug to reverse NAFLD. Ferroptosis is an iron-dependent and non-apoptotic form of cell death characterized by the iron-induced accumulation of lipid reactive oxygen species (ROS), which damage nucleic acids, proteins, and lipids; generate intracellular oxidative stress; and ultimately cause cell death. Emerging evidence indicates that ferroptosis is involved in the progression of NAFLD, although the mechanism of action of ferroptosis in NAFLD is still poorly understood. Herein, we summarize the mechanism of action of ferroptosis in certain diseases, especially in the pathogenesis of NAFLD, and discuss the potential therapeutic approaches currently used to treat NAFLD. This review also highlights further directions for the treatment and prevention of NAFLD and related diseases.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Ferroptosis and Its Role in Chronic Diseases

Ferroptosis, which has been widely associated with many diseases, is an iron-dependent regulated cell death characterized by intracellular lipid peroxide accumulation. It exhibits morphological, biochemical, and genetic characteristics that are unique in comparison to other types of cell death. The course of ferroptosis can be accurately regulated by the metabolism of iron, lipids, amino acids, and various signal pathways. In this review, we summarize the basic characteristics of ferroptosis, its regulation, as well as the relationship between ferroptosis and chronic diseases such as cancer, nervous system diseases, metabolic diseases, and inflammatory bowel diseases. Finally, we describe the regulatory effects of food-borne active ingredients on ferroptosis.

Understanding the mechanistic regulation of ferroptosis in cancer: gene matters

Ferroptosis has emerged as a crucial regulated cell death involved in a variety of physiological processes or pathological diseases, such as tumor suppression. Though initially being found from anti-cancer drug screening and considered not essential as apoptosis for growth and development, numerous studies have demonstrated that ferroptosis is tightly regulated by key genetic pathways and/or genes, including several tumor suppressors and oncogenes. In this review, we will first introduce the basic concepts of ferroptosis, characterized by the features of non-apoptotic, iron-dependent and overwhelmed accumulation of lipid peroxides, and the underlying regulated circuits are considered to be pro-ferroptotic pathways. Then we discuss several established lipid peroxidation defending systems within cells, including SLC7A11/GPX4, FSP1/CoQ, GCH1/BH4, and mitochondria DHODH/CoQ, all of which serve as anti-ferroptoic pathways to prevent ferroptosis. Moreover, we provide a comprehensive summary of the genetic regulation of ferroptosis via targeting the above-mentioned pro-ferroptotic or anti-ferroptotic pathways. The regulation of pro- and anti-ferroptotic pathways gives rise to more specific responses to the tumor cells in a context-dependent manner, highlighting the unceasing study and deeper understanding of mechanistic regulation of ferroptosis for the purpose of applying ferroptosis induction in cancer therapy.

Role of Ferroptosis in Fibrotic Diseases

Ferroptosis is a unique and pervasive form of regulated cell death driven by iron-dependent phospholipid peroxidation. It results from disturbed cellular metabolism and imbalanced redox homeostasis and is regulated by various cellular metabolic pathways. Recent preclinical studies have revealed that ferroptosis may be an attractive therapeutic target in fibrotic diseases, such as liver fibrosis, pulmonary fibrosis, kidney fibrosis, and myocardial fibrosis. This review summarizes the latest knowledge on the regulatory mechanism of ferroptosis and its roles in fibrotic diseases. These updates may provide a novel perspective for the treatment of fibrotic diseases as well as future research.

Research Progress of Fibroblast Growth Factor 21 in Fibrotic Diseases

Fibrosis is a common pathological outcome of chronic injuries, characterized by excessive deposition of extracellular matrix components in organs, as seen in most chronic inflammatory diseases. At present, there is an increasing tendency of the morbidity and mortality of diseases caused by fibrosis, but the treatment measures for fibrosis are still limited. Fibroblast growth factor 21 (FGF21) belongs to the FGF19 subfamily, which also has the name endocrine FGFs because of their endocrine manner. In recent years, it has been found that plasma FGF21 level is significantly correlated with fibrosis progression. Furthermore, there is evidence that FGF21 has a pronounced antifibrotic effect in a variety of fibrotic diseases. This review summarizes the biological effects of FGF21 and discusses what is currently known about this factor and fibrosis disease, highlighting emerging insights that warrant further research.

MicroRNA-4735-3p Facilitates Ferroptosis in Clear Cell Renal Cell Carcinoma by Targeting SLC40A1

Objective. Clear cell renal cell carcinoma (ccRCC) is the major histopathological subtype of renal cancer, and ferroptosis is implicated in the pathogenesis of ccRCC. The present study was aimed at investigating the role and underlying mechanisms of microRNA-4735-3p (miR-4735-3p) in ccRCC. Methods. Human ccRCC cell lines were transfected with the miR-4735-3p mimic or inhibitor to manipulate the expression of miR-4735-3p. Cell proliferation, colony formation, cell migration, cell invasion, cell death, oxidative stress, lipid peroxidation, and iron metabolism were determined. To validate the necessity of solute carrier family 40 member 1 (SLC40A1), human ccRCC cell lines were overexpressed with SLC40A1 using adenoviral vectors. Results. miR-4735-3p expression was reduced in human ccRCC tissues and cell lines but elevated upon ferroptotic stimulation. The miR-4735-3p mimic increased, while the miR-4735-3p inhibitor decreased oxidative stress, lipid peroxidation, iron overload, and ferroptosis of human ccRCC cell lines. Mechanistic studies identified SLC40A1 as a direct target of miR-4735-3p, and SLC40A1 overexpression significantly attenuated iron overload and ferroptosis in the miR-4735-3p mimic-treated human ccRCC cell lines. Conclusion. miR-4735-3p facilitates ferroptosis and tumor suppression in ccRCC by targeting SLC40A1.

CRISPR-Cas9-based genome-wide screening identified novel targets for treating sorafenib-resistant hepatocellular carcinoma: a cross-talk between FGF21 and the NRF2 pathway

The treatment of hepatocellular carcinoma (HCC) has been dominated by multikinase inhibitors for more than a decade. However, drug resistance can severely restrict the efficacy of these drugs. Using CRISPR/CAS9 genome library screening, we evaluated Kelch-like ECH-associated protein 1 (KEAP1) as a key regulator of sorafenib's susceptibility in HCC. We also investigated whether KEAP1's knockdown can stabilize nuclear factor (erythroid-derived 2)-like 2 (NRF2) protein levels that led to sorafenib's resistance, including an NRF2 inhibitor that can synergize with sorafenib to abolish HCC's growth in vitro and in vivo. Furthermore, we clarified that fibroblast growth factor 21 (FGF21) is an important downstream regulator of NRF2 in HCC. Intriguingly, we observed that FGF21 bound to NRF2 through the C-terminus of FGF21, thereby stabilizing NRF2 by reducing its ubiquitination and generating a positive feedback loop in sorafenib-resistant HCC. These findings, therefore, propose that targeting FGF21 is a promising strategy to combat HCC sorafenib's resistance.