Iron homeostasis and disorders revisited in the sepsis

Impaired GPX4 activity elicits ferroptosis in alveolar type II cells promoting PHMG-induced pulmonary fibrosis development

Inhaling polyhexamethylene guanidine (PHMG) aerosol, a broad-spectrum disinfectant, can lead to severe pulmonary fibrosis. Ferroptosis, a form of programmed cell death triggered by iron-dependent lipid peroxidation, is believed to play a role in the chemical-induced pulmonary injury. This study aimed to investigate the mechanism of ferroptosis in the progression of PHMG-induced pulmonary fibrosis. C57BL/6 J mice and the alveolar type II cell line MLE-12 were used to evaluate the toxicity of PHMG in vivo and in vitro, respectively. The findings indicated that iron deposition was observed in PHMG induced pulmonary fibrosis mouse model and ferroptosis related genes have changed after 8 weeks PHMG exposure. Additionally, there were disturbances in the antioxidant system and mitochondrial damage in MLE-12 cells following a 12-hour treatment with PHMG. Furthermore, the study observed an increase in lipid peroxidation and a decrease in GPX4 activity in MLE-12 cells after exposure to PHMG. Moreover, pretreatment with the ferroptosis inhibitors Ferrostatin-1 (Fer-1) and Liproxstatin-1 (Lip-1) not only restored the antioxidant system and GPX4 activity but also mitigated lipid peroxidation. Current data exhibit the role of ferroptosis pathway in PHMG-induced pulmonary fibrosis and provide a potential target for future treatment.

The Role of Iron Metabolism in Sepsis-associated Encephalopathy: a Potential Target

Sepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction secondary to infection, and the severity can range from mild delirium to deep coma. Disorders of iron metabolism have been proven to play an important role in a variety of neurodegenerative diseases by inducing cell damage through iron accumulation in glial cells and neurons. Recent studies have found that iron accumulation is also a potential mechanism of SAE. Systemic inflammation can induce changes in the expression of transporters and receptors on cells, especially high expression of divalent metal transporter1 (DMT1) and low expression of ferroportin (Fpn) 1, which leads to iron accumulation in cells. Excessive free Fe2+ can participate in the Fenton reaction to produce reactive oxygen species (ROS) to directly damage cells or induce ferroptosis. As a result, it may be of great help to improve SAE by treatment of targeting disorders of iron metabolism. Therefore, it is important to review the current research progress on the mechanism of SAE based on iron metabolism disorders. In addition, we also briefly describe the current status of SAE and iron metabolism disorders and emphasize the therapeutic prospect of targeting iron accumulation as a treatment for SAE, especially iron chelator. Moreover, drug delivery and side effects can be improved with the development of nanotechnology. This work suggests that treating SAE based on disorders of iron metabolism will be a thriving field.

Knockdown of LncRNA Lcn2-204 alleviates sepsis-induced myocardial injury by regulation of iron overload and ferroptosis

Ferroptosis is an iron-dependent programmed cell death form resulting from lipid peroxidation damage, it plays a key role in organ damage and tumor development from various causes. Sepsis leads to severe host response after infection with high mortality. The long non-coding RNAs (LncRNAs) are involved in different pathophysiological mechanisms of multiple diseases. Here, we used cecal ligation and puncture (CLP) operation to mimic sepsis induced myocardial injury (SIMI) in mouse model, and LncRNAs and mRNAs were profiled by Arraystar mouse LncRNA Array V3.0. Based on the microarray results, 552 LncRNAs and 520 mRNAs were differentially expressed in the sham and CLP groups, among them, LncRNA Lcn2-204 was the highest differentially expressed up-regulated LncRNA. Iron metabolism disorder was involved in SIMI by bioinformatics analysis, meanwhile, myocardial iron content and lipocalin-2 (Lcn2) protein expressions were increased. The CNC network comprised 137 positive interactions and 138 negative interactions. Bioinformatics analysis showed several iron-related terms were enriched and six genes (Scara5, Tfrc, Lcn2, Cp, Clic5, Ank1) were closely associated with iron metabolism. Then, we constructed knockdown LncRNA Lcn2-204 targeting myocardium and found that it ameliorated cardiac injury in mouse sepsis model through modulating iron overload and ferroptosis. In addition, we found that LncRNA Lcn2-204 was involved in the regulation of Lcn2 expression in septic myocardial injury. Based on these findings, we conclude that iron overload and ferroptosis are the key mechanisms leading to myocardial injury in sepsis, knockdown of LncRNA Lcn2-204 plays the cardioprotective effect through inhibition of iron overload, ferroptosis and Lcn2 expression. It may provide a novel therapeutic approach to ameliorate sepsis-induced myocardial injury.

Ribonuclease inhibitor 1 emerges as a potential biomarker and modulates inflammation and iron homeostasis in sepsis

Sepsis, marked by organ dysfunction, necessitates reliable biomarkers. Ribonuclease inhibitor 1 (RNH1), a ribonuclease (RNase) inhibitor, emerged as a potential biomarker for acute kidney injury and mortality in thoracoabdominal aortic aneurysm patients. Our study investigates RNH1 dynamics in sepsis, its links to mortality and organ dysfunction, and the interplay with RNase 1 and RNase 5. Furthermore, we explore RNH1 as a therapeutic target in sepsis-related processes like inflammation, non-canonical inflammasome activation, and iron homeostasis. We showed that RNH1 levels are significantly higher in deceased patients compared to sepsis survivors and correlate with creatine kinase, aspartate and alanine transaminase, bilirubin, serum creatinine and RNase 5, but not RNase 1. RNH1 mitigated LPS-induced TNFα and RNase 5 secretion, and relative mRNA expression of ferroptosis-associated genes HMOX1, FTH1 and HAMP in PBMCs. Monocytes were identified as the predominant type of LPS-positive PBMCs. Exogenous RNH1 attenuated LPS-induced CASP5 expression, while increasing IL-1β secretion in PBMCs and THP-1 macrophages. As RNH1 has contradictory effects on inflammation and non-canonical inflammasome activation, its use as a therapeutic agent is limited. However, RNH1 levels may play a central role in iron homeostasis during sepsis, supporting our clinical observations. Hence, RNH1 shows promise as biomarkers for renal and hepatic dysfunction and hepatocyte injury, and may be useful in predicting the outcome of septic patients.

Iron Metabolism in the Recovery Phase of Critical Illness with a Focus on Sepsis

Iron is an essential nutrient for humans and microbes, such as bacteria. Iron deficiency commonly occurs in critically ill patients, but supplementary iron therapy is not considered during the acute phase of critical illness since it increases iron availability for invading microbes and oxidative stress. However, persistent iron deficiency in the recovery phase is harmful and has potential adverse outcomes such as cognitive dysfunction, fatigue, and cardiopulmonary dysfunction. Therefore, it is important to treat iron deficiency quickly and efficiently. This article reviews current knowledge about iron-related biomarkers in critical illness with a focus on patients with sepsis, and provides possible criteria to guide decision-making for iron supplementation in the recovery phase of those patients.

Inhibition of STAT3-NF-κB pathway facilitates SSPH I-induced ferroptosis in HepG2 cells

Hepatocellular carcinoma (HCC), a highly lethal solid tumor, has shown responsiveness to ferroptosis inducers, presenting new avenues in cancer treatment. Our study focuses on the roles of STAT3 and Nf-κB in regulating ferroptosis, particularly their interaction in this process. Using HepG2 cells, we employed specific inhibitors (Stattic for STAT3 and Bay11-7082 for Nf-κB) and a ferroptosis inducer, SSPH I, to dissect their collective impact on ferroptosis. Our findings reveal that inhibiting STAT3 and Nf-κB enhances ferroptosis and cytotoxicity induced by SSPH I. This is mechanistically linked to alterations in iron metabolism-related proteins and GPX4 resulting from SSPH I action, which consequently triggers a STAT3-dependent activation of Nf-κB. The inhibition of STAT3 and Nf-κB led to increased intracellular ROS, MDA, and Fe2+, along with significant GSH depletion, thereby intensifying lipid peroxidation and iron overload in HepG2 cells. This study offers a deeper understanding of the ferroptosis mechanisms in HCC. It highlights the therapeutic potential of targeting STAT3 and Nf-κB pathways to enhance the efficacy of ferroptosis-based treatments.

Iron and ferritin effects on intensive care unit mortality: A meta-analysis

BACKGROUND

The effect of serum iron or ferritin parameters on mortality among critically ill patients is not well characterized.

AIM

To determine the association between serum iron or ferritin parameters and mortality among critically ill patients.

METHODS

Web of Science, Embase, PubMed, and Cochrane Library databases were searched for studies on serum iron or ferritin parameters and mortality among critically ill patients. Two reviewers independently assessed, selected, and abstracted data from studies reporting on serum iron or ferritin parameters and mortality among critically ill patients. Data on serum iron or ferritin levels, mortality, and demographics were extracted.

RESULTS

Nineteen studies comprising 125490 patients were eligible for inclusion. We observed a slight negative effect of serum ferritin on mortality in the United States population [relative risk (RR) 1.002; 95%CI: 1.002-1.004). In patients with sepsis, serum iron had a significant negative effect on mortality (RR = 1.567; 95%CI: 1.208-1.925).

CONCLUSION

This systematic review presents evidence of a negative correlation between serum iron levels and mortality among patients with sepsis. Furthermore, it reveals a minor yet adverse impact of serum ferritin on mortality among the United States population.

The crosstalk between mitochondrial quality control and metal-dependent cell death

Mitochondria are the centers of energy and material metabolism, and they also serve as the storage and dispatch hubs of metal ions. Damage to mitochondrial structure and function can cause abnormal levels and distribution of metal ions, leading to cell dysfunction and even death. For a long time, mitochondrial quality control pathways such as mitochondrial dynamics and mitophagy have been considered to inhibit metal-induced cell death. However, with the discovery of new metal-dependent cell death including ferroptosis and cuproptosis, increasing evidence shows that there is a complex relationship between mitochondrial quality control and metal-dependent cell death. This article reviews the latest research results and mechanisms of crosstalk between mitochondrial quality control and metal-dependent cell death in recent years, as well as their involvement in neurodegenerative diseases, tumors and other diseases, in order to provide new ideas for the research and treatment of related diseases.

Sepsis during short bowel syndrome hospitalizations: Identifying trends, disparities, and clinical outcomes in the United States

BACKGROUND

Short bowel syndrome (SBS) hospitalizations are often complicated with sepsis. There is a significant paucity of data on adult SBS hospitalizations in the United States and across the globe.

AIM

To assess trends and outcomes of SBS hospitalizations complicated by sepsis in the United States.

METHODS

The National Inpatient Sample was utilized to identify all adult SBS hospitalizations between 2005-2014. The study cohort was further divided based on the presence or absence of sepsis. Trends were identified, and hospitalization characteristics and clinical outcomes were compared. Predictors of mortality for SBS hospitalizations complicated with sepsis were assessed.

RESULTS

Of 247097 SBS hospitalizations, 21.7% were complicated by sepsis. Septic SBS hospitalizations had a rising trend of hospitalizations from 20.8% in 2005 to 23.5% in 2014 (P trend < 0.0001). Compared to non-septic SBS hospitalizations, septic SBS hospitalizations had a higher proportion of males (32.8% vs 29.3%, P < 0.0001), patients in the 35-49 (45.9% vs 42.5%, P < 0.0001) and 50-64 (32.1% vs 31.1%, P < 0.0001) age groups, and ethnic minorities, i.e., Blacks (12.4% vs 11.3%, P < 0.0001) and Hispanics (6.7% vs 5.5%, P < 0.0001). Furthermore, septic SBS hospitalizations had a higher proportion of patients with intestinal transplantation (0.33% vs 0.22%, P < 0.0001), inpatient mortality (8.5% vs 1.4%, P < 0.0001), and mean length of stay (16.1 d vs 7.7 d, P < 0.0001) compared to the non-sepsis cohort. A younger age, female gender, White race, and presence of comorbidities such as anemia and depression were identified to be independent predictors of inpatient mortality for septic SBS hospitalizations.

CONCLUSION

Septic SBS hospitalizations had a rising trend between 2005-2014 and were associated with higher inpatient mortality compared to non-septic SBS hospitalizations.

The possible mechanisms of ferroptosis in sepsis-associated acquired weakness

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and its morbidity and mortality rates are increasing annually. It is an independent risk factor for intensive care unit-acquired weakness (ICU-AW), which is a common complication of patients in ICU. This situation is also known as sepsis-associated acquired weakness (SAW), and it can be a complication in more than 60% of patients with sepsis. The outcomes of SAW are often prolonged mechanical ventilation, extended hospital stays, and increased morbidity and mortality of patients in ICUs. The pathogenesis of SAW is unclear, and an effective clinical treatment is not available. Ferroptosis is an iron-dependent type of cell death with unique morphological, biochemical, and genetic features. Unlike other forms of cell death such as autophagy, apoptosis, and necrosis, ferroptosis is primarily driven by lipid peroxidation. Cells undergo ferroptosis during sepsis, which further enhances the inflammatory response. This process leads to increased cell death, as well as multi-organ dysfunction and failure. Recently, there have been sporadic reports suggesting that SAW is associated with ferroptosis, but the exact pathophysiological mechanisms remain unclear. Therefore, we reviewed the possible pathogenesis of ferroptosis that leads to SAW and offer new strategies to prevent and treat SAW.

Andrographolide attenuates sepsis-induced acute kidney injury by inhibiting ferroptosis through the Nrf2/FSP1 pathway

Sepsis is a systemic inflammatory response syndrome caused by infection, which causes renal dysfunction known as sepsis-associated acute kidney injury (S-AKI). Ferroptosis is a form of lipid peroxidation dependent on iron and reactive oxygen species that differs from other forms of programmed cell death at the morphological and biochemical levels. Andrographolide (AG), a natural diterpenoid lactone compound extracted from Andrographis paniculata, has been shown to have therapeutic effects in kidney disease. In this study, we investigated the novel mechanism by which AG attenuates septic acute kidney injury by inhibiting ferroptosis in renal tubular epithelial cells (HK-2) through the Nrf2/FSP1 pathway. Cecum ligation and puncture (CLP)-induced septic rats and lipopolysaccharide (LPS)-induced HK-2 cells were used for in vivo and in vitro experiments. Firstly, in septic rats and HK-2 cells, AG effectively decreased the levels of kidney injury indicators, including blood creatinine, urea nitrogen, and markers of kidney injury such as neutrophil gelatinase-associated lipid transport protein and kidney injury molecule-1 (KIM-1). In addition, AG prevented ferroptotosis, by avoiding the accumulation of iron and lipid peroxidation, and an increase in SLC7A11 and GPX4 in AG-treated HK-2 cells. Furthermore, AG attenuated mitochondrial damage, including mitochondrial swelling, outer membrane rupture, and a reduction in mitochondrial cristae in LPS-treated HK-2 cells. Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, significantly inhibited LPS-induced ferroptosis in HK-2 cells. Importantly, our results confirm that Nrf2/FSP1 is an important pathway for ferroptosis resistance. Nrf2 siRNA hindered the effect of AG in attenuating acute kidney injury and inhibiting ferroptosis. These findings demonstrate that Nrf2/FSP1-mediated HK-2 ferroptosis is associated with AG, alleviates septic acute kidney injury, and indicates a novel avenue for therapeutic interventions in the treatment of acute kidney injury in sepsis.

Value of serum iron and urine neutrophil gelatinase-associated lipocalin in predicting the mortality of critically ill patients with sepsis

INTRODUCTION

We aimed to investigate the association of iron metabolism-related parameters with 60-day mortality in critically ill patients with sepsis.

METHODS

Serum or urine concentrations of iron metabolism-related parameters on intensive care unit admission were measured in a prospective cohort of 133 eligible patients with sepsis according to the Sepsis-3 criteria, and these values were compared between survivors and nonsurvivors, categorized according to their 60-day survival status. Cox regression analyses were performed to examine the association between iron parameters and 60-day mortality. Kaplan-Meier methods were used to illustrate the differences in survival between different iron parameters.

RESULTS

Of the 133 patients included in the study, 61 (45.8%) had died by day 60. After adjusting for confounding variables, higher concentrations of serum iron (cut-off 9.5 μmol/mL) and higher concentrations of urine neutrophil gelatinase-associated lipocalin (uNGAL; cut-off 169.3 ng/mL) were associated with a significantly greater risk of death in the Cox regression analysis. These two biomarkers combined with Sequential Organ Failure Assessment (SOFA) scores increased the area under the receiver operating characteristic (AUROC) curve to 0.85.

DISCUSSION

These findings suggest that higher concentrations of serum iron and uNGAL are each associated with higher 60-day mortality, and they add significant accuracy to this prediction in combination with SOFA. Abbreviations: uNGAL: urine neutrophil gelatinase-associated lipocalin; ICU: intensive care unit; SOFA: Sequential Organ Failure Assessment; APACHE II: the Acute Physiology and Chronic Health Evaluation II; ELISA: enzyme-linked immunosorbent assay; HR: hazard ratio; CIs: confidence intervals; WBC: white blood cell; TBIL: total bilirubin.

Suppressing Endoplasmic Reticulum Stress Alleviates LPS-Induced Acute Lung Injury via Inhibiting Inflammation and Ferroptosis

Acute lung injury (ALI) is a life-threatening clinical disorder with high mortality rate. Ferroptosis is a new type of programmed cell death with lipid peroxidation and iron ion overloading as the main characteristics. Endoplasmic reticulum (ER) stress and ferroptosis play pivotal roles in the pathogenesis of ALI. The study aimed to investigate the underlying relationship between ER stress and ferroptosis in ALI. The ER stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated LPS-induced inflammation, and decreased IL-1β, IL-6, and TNF-α levels in BALF and lungs. The increased MDA and decreased GSH induced by LPS were partially reversed by 4-PBA, which also inhibited the expressions of ferroptosis-related protein ACSL4, COX-2, and FTH1. TEM further confirmed the ferroptosis within airway epithelia cells was ameliorated by 4-PBA. Moreover, 4-PBA reduced the production of ROS and lipid ROS in LPS-exposed BEAS-2B cells in a concentration-dependent way. Meanwhile, 4-PBA mitigated LPS-induced cell apoptosis in vivo and in vitro. Mechanistically, the MAPK signaling pathway activated by LPS was downregulated by 4-PBA. Collectively, these findings suggested that 4-PBA protected against ALI by inhibiting inflammation and ferroptosis through downregulating ER stress, thus providing a potential intervention for ALI and revealing the possible interaction between ER stress and ferroptosis in ALI.

Radix Sanguisorbae Improves Intestinal Barrier in Septic Rats via HIF-1 α/HO-1/Fe2+ Axis

OBJECTIVE

To investigate whether Radix Sanguisorbae (RS, Diyu) could restore intestinal barrier function following sepsis using a cecal ligation and puncture (CLP)-induced septic rat model and lipopolysaccharide (LPS)-challenged IEC-6 cell model, respectively.

METHODS

Totally 224 rats were divided into 4 groups including a control, sham, CLP and RS group according to a random number table. The rats in the control group were administrated with Ringer's lactate solution (30 mL/kg) with additional dopamine [10 µ g/(kg·min)] and given intramuscular injections of cefuroxime sodium (10 mg/kg) 12 h following CLP. The rats in the RS group were administrated with RS (10 mg/kg) through tail vein 1 h before CLP and treated with RS (10 mg/kg) 12 h following CLP. The rats in the sham group were only performed abdominal surgery without CLP. The rats in the CLP group were performed with CLP without any treatment. The other steps were same as control group. The effects of RS on intestinal barrier function, mesenteric microvessels barrier function, multi-organ function indicators, inflammatory response and 72 h survival window following sepsis were observed. In vitro, the effects of RS on LPS-challenged IEC-6 cell viability, the expressions of zona occludens-1 (ZO-1) and ferroptosis index were evaluated by cell counting kit-8, immunofluorescence and Western blot analysis. Bioinformatic tools were applied to investigate the pharmacological network of RS in sepsis to predict the active compounds and potential protein targets and pathways.

RESULTS

The sepsis caused severe intestinal barrier dysfunction, multi-organ injury, lipid peroxidation accumulation, and ferroptosis in vivo. RS treatment significantly prolonged the survival time to 56 h and increased 72-h survival rate to 7/16 (43.75%). RS also improved intestinal barrier function and relieved intestinal inflammation. Moreover, RS significantly decreased lipid peroxidation and inhibited ferroptosis (P<0.05 or P<0.01). Administration of RS significantly worked better than Ringer's solution used alone. Using network pharmacology prediction, we found that ferroptosis and hypoxia inducible factor-1 (HIF-1 α) signaling pathways might be involved in RS effects on sepsis. Subsequent Western blot, ferrous iron measurements, and FerroOrange fluorescence of ferrous iron verified the network pharmacology predictions.

CONCLUSION

RS improved the intestinal barrier function and alleviated intestinal injury by inhibiting ferroptosis, which was related in part to HIF-1 α/heme oxygenase-1/Fe2+ axis.

Glycine recalibrates iron homeostasis of lens epithelial cells by blocking lysosome-dependent ferritin degradation

One of the major pathological processes in cataracts has been identified as ferroptosis. However, studies on the iron metabolism mechanism in lens epithelial cells (LECs) and the methods of effectively alleviating ferroptosis in LECs are scarce. Along these lines, we found that in the ultraviolet radiation b (UVB) induced cataract model in vitro and in vivo, the ferritin of LECs is over-degraded by lysosomes, resulting in the occurrence of iron homeostasis disorder. Glycine can affect the ferritin degradation through the proton-coupled amino acid transporter (PAT1) on the lysosome membrane, further upregulating the content of nuclear factor erythrocyte 2 related factor 2 (Nrf2) to reduce the damage of LECs from two aspects of regulating iron homeostasis and alleviating oxidative stress. By co-staining, we further demonstrate that there is a more sensitive poly-(rC)-binding protein 2 (PCBP2) transportation of iron ions in LECs after UVB irradiation. Additionally, this study illustrated the increased expression of nuclear receptor coactivator 4 (NCOA4) in NRF2-KO mice, indicating that Nrf2 may affect ferritin degradation by decreasing the expression of NCOA4. Collectively, glycine can effectively regulate cellular iron homeostasis by synergistically affecting the lysosome-dependent ferritin degradation and PCBP2-mediated ferrous ion transportation, ultimately delaying the development of cataracts.

Perspectives on Iron Deficiency as a Cause of Human Disease in Global Public Health

Iron (Fe) is a necessary trace element in numerous pathways of human metabolism. Therefore, Fe deficiency is capable of causing multiple health problems. Apart from the well-known microcytic anemia, lack of Fe can cause severe psychomotor disorders in children, pregnant women, and adults in general. Iron deficiency is a global health issue, mainly caused by dietary deficiency but aggravated by inflammatory conditions. The challenges related to this deficiency need to be addressed on national and international levels. This review aims to summarize briefly the disease burden caused by Fe deficiency in the context of global public health and aspires to offer some hands-on guidelines.

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy

Ferroptosis, characterized by iron accumulation and lipid peroxidation, is a form of iron-driven cell death. Mitophagy is a type of selective autophagy, where degradation of damaged mitochondria is the key mechanism for maintaining mitochondrial homeostasis. Additionally, Chaperone-mediated autophagy (CMA) is a biological process that transports individual cytoplasmic proteins to lysosomes for degradation through companion molecules such as heat shock proteins. Research has demonstrated the involvement of ferroptosis, mitophagy, and CMA in the pathological progression of Osteoarthritis (OA). Furthermore, research has indicated a significant correlation between alterations in the expression of reactive oxygen species (ROS), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factors (HIFs) and the occurrence of OA, particularly in relation to ferroptosis and mitophagy. In light of these findings, our study aims to assess the regulatory functions of ferroptosis and mitophagy/CMA in the pathogenesis of OA. Additionally, we propose a mechanism of crosstalk between ferroptosis and mitophagy, while also examining potential pharmacological interventions for targeted therapy in OA. Ultimately, our research endeavors to offer novel insights and directions for the prevention and treatment of OA.

Iron as an emerging therapeutic target in critically ill patients

The multiple roles of iron in the body have been known for decades, particularly its involvement in iron overload diseases such as hemochromatosis. More recently, compelling evidence has emerged regarding the critical role of non-transferrin bound iron (NTBI), also known as catalytic iron, in the care of critically ill patients in intensive care units (ICUs). These trace amounts of iron constitute a small percentage of the serum iron, yet they are heavily implicated in the exacerbation of diseases, primarily by catalyzing the formation of reactive oxygen species, which promote oxidative stress. Additionally, catalytic iron activates macrophages and facilitates the growth of pathogens. This review aims to shed light on this underappreciated phenomenon and explore the various common sources of NTBI in ICU patients, which lead to transient iron dysregulation during acute phases of disease. Iron serves as the linchpin of a vicious cycle in many ICU pathologies that are often multifactorial. The clinical evidence showing its detrimental impact on patient outcomes will be outlined in the major ICU pathologies. Finally, different therapeutic strategies will be reviewed, including the targeting of proteins involved in iron metabolism, conventional chelation therapy, and the combination of renal replacement therapy with chelation therapy.

Autophagy-dependent ferroptosis in infectious disease

Autophagy is the initial defense response of the host against pathogens. Autophagy can be either non-selective or selective. It selectively targets the degradation of autophagic substrates through the sorting and transportation of autophagic receptor proteins. However, excessive autophagy activity will trigger cell death especially ferroptosis, which was characterized by the accumulation of lipid peroxide and free iron. Several certain types of selective autophagy degrade antioxidant systems and ferritin. Here, we summarized the latest researches of autophagy in infection and discuss the regulatory mechanisms and signaling pathways of autophagy-dependent ferroptosis.

The Mechanisms of Action of Hyperbaric Oxygen in Restoring Host Homeostasis during Sepsis

The perception of sepsis has shifted over time; however, it remains a leading cause of death worldwide. Sepsis is now recognized as an imbalance in host cellular functions triggered by the invading pathogens, both related to immune cells, endothelial function, glucose and oxygen metabolism, tissue repair and restoration. Many of these key mechanisms in sepsis are also targets of hyperbaric oxygen (HBO2) treatment. HBO2 treatment has been shown to improve survival in clinical studies on patients with necrotizing soft tissue infections as well as experimental sepsis models. High tissue oxygen tension during HBO2 treatment may affect oxidative phosphorylation in mitochondria. Oxygen is converted to energy, and, as a natural byproduct, reactive oxygen species are produced. Reactive oxygen species can act as mediators, and both these and the HBO2-mediated increase in oxygen supply have the potential to influence the cellular processes involved in sepsis. The pathophysiology of sepsis can be explained comprehensively through resistance and tolerance to infection. We argue that HBO2 treatment may protect the host from collateral tissue damage during resistance by reducing neutrophil extracellular traps, inhibiting neutrophil adhesion to vascular endothelium, reducing proinflammatory cytokines, and halting the Warburg effect, while also assisting the host in tolerance to infection by reducing iron-mediated injury and upregulating anti-inflammatory measures. Finally, we show how inflammation and oxygen-sensing pathways are connected on the cellular level in a self-reinforcing and detrimental manner in inflammatory conditions, and with support from a substantial body of studies from the literature, we conclude by demonstrating that HBO2 treatment can intervene to maintain homeostasis.

The Road from AKI to CKD: Molecular Mechanisms and Therapeutic Targets of Ferroptosis

Acute kidney injury (AKI) is a prevalent pathological condition that is characterized by a precipitous decline in renal function. In recent years, a growing body of studies have demonstrated that renal maladaptation following AKI results in chronic kidney disease (CKD). Therefore, targeting the transition of AKI to CKD displays excellent therapeutic potential. However, the mechanism of AKI to CKD is mediated by multifactor, and there is still a lack of effective treatments. Ferroptosis, a novel nonapoptotic form of cell death, is believed to have a role in the AKI to CKD progression. In this study, we retrospectively examined the history and characteristics of ferroptosis, summarized ferroptosis's research progress in AKI and CKD, and discussed how ferroptosis participates in regulating the pathological mechanism in the progression of AKI to CKD. Furthermore, we highlighted the limitations of present research and projected the future evolution of ferroptosis. We hope this work will provide clues for further studies of ferroptosis in AKI to CKD and contribute to the study of effective therapeutic targets to prevent the progression of kidney diseases.

Structures and coordination chemistry of transporters involved in manganese and iron homeostasis

A repertoire of transporters plays a crucial role in maintaining homeostasis of biologically essential transition metals, manganese, and iron, thus ensuring cell viability. Elucidating the structure and function of many of these transporters has provided substantial understanding into how these proteins help maintain the optimal cellular concentrations of these metals. In particular, recent high-resolution structures of several transporters bound to different metals enable an examination of how the coordination chemistry of metal ion-protein complexes can help us understand metal selectivity and specificity. In this review, we first provide a comprehensive list of both specific and broad-based transporters that contribute to cellular homeostasis of manganese (Mn2+) and iron (Fe2+ and Fe3+) in bacteria, plants, fungi, and animals. Furthermore, we explore the metal-binding sites of the available high-resolution metal-bound transporter structures (Nramps, ABC transporters, P-type ATPase) and provide a detailed analysis of their coordination spheres (ligands, bond lengths, bond angles, and overall geometry and coordination number). Combining this information with the measured binding affinity of the transporters towards different metals sheds light into the molecular basis of substrate selectivity and transport. Moreover, comparison of the transporters with some metal scavenging and storage proteins, which bind metal with high affinity, reveal how the coordination geometry and affinity trends reflect the biological role of individual proteins involved in the homeostasis of these essential transition metals.

The mechanism of ferroptosis in early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a cerebrovascular accident with an acute onset, severe disease characteristics, and poor prognosis. Within 72 hours after the occurrence of SAH, a sequence of pathological changes occur in the body including blood-brain barrier breakdown, cerebral edema, and reduced cerebrovascular flow that are defined as early brain injury (EBI), and it has been demonstrated that EBI exhibits an obvious correlation with poor prognosis. Ferroptosis is a novel programmed cell death mode. Ferroptosis is induced by the iron-dependent accumulation of lipid peroxides and reactive oxygen species (ROS). Ferroptosis involves abnormal iron metabolism, glutathione depletion, and lipid peroxidation. Recent study revealed that ferroptosis is involved in EBI and is significantly correlated with poor prognosis. With the gradual realization of the importance of ferroptosis, an increasing number of studies have been conducted to examine this process. This review summarizes the latest work in this field and tracks current research progress. We focused on iron metabolism, lipid metabolism, reduction systems centered on the GSH/GPX4 system, other newly discovered GSH/GPX4-independent antioxidant systems, and their related targets in the context of early brain injury. Additionally, we examined certain ferroptosis regulatory mechanisms that have been studied in other fields but not in SAH. A link between death and oxidative stress has been described. Additionally, we highlight the future research direction of ferroptosis in EBI of SAH, and this provides new ideas for follow-up research.

Pharmacological inhibition of ferroptosis as a therapeutic target for sepsis-associated organ damage

Sepsis is a complex clinical syndrome caused by dysfunctional host response to infection, which contributes to excess mortality and morbidity worldwide. The development of life-threatening sepsis-associated organ injury to the brain, heart, kidneys, lungs, and liver is a major concern for sepsis patients. However, the molecular mechanisms underlying sepsis-associated organ injury remain incompletely understood. Ferroptosis, an iron-dependent non-apoptotic form of cell death characterized by lipid peroxidation, is involved in sepsis and sepsis-related organ damage, including sepsis-associated encephalopathy, septic cardiomyopathy, sepsis-associated acute kidney injury, sepsis-associated acute lung injury, and sepsis-induced acute liver injury. Moreover, compounds that inhibit ferroptosis exert potential therapeutic effects in the context of sepsis-related organ damage. This review summarizes the mechanism by which ferroptosis contributes to sepsis and sepsis-related organ damage. We focus on the emerging types of therapeutic compounds that can inhibit ferroptosis and delineate their beneficial pharmacological effects for the treatment of sepsis-related organ damage. The present review highlights pharmacologically inhibiting ferroptosis as an attractive therapeutic strategy for sepsis-related organ damage.

Dysregulated Iron Homeostasis as Common Disease Etiology and Promising Therapeutic Target

Iron is irreplaceably required for animal and human cells as it provides the activity center for a wide variety of essential enzymes needed for energy production, nucleic acid synthesis, carbon metabolism and cellular defense. However, iron is toxic when present in excess and its uptake and storage must, therefore, be tightly regulated to avoid damage. A growing body of evidence indicates that iron dysregulation leading to excess quantities of free reactive iron is responsible for a wide range of otherwise discrete diseases. Iron excess can promote proliferative diseases such as infections and cancer by supplying iron to pathogens or cancer cells. Toxicity from reactive iron plays roles in the pathogenesis of various metabolic, neurological and inflammatory diseases. Interestingly, a common underlying aspect of these conditions is availability of excess reactive iron. This underpinning aspect provides a potential new therapeutic avenue. Existing hematologically used iron chelators to take up excess iron have shown serious limitations for use but new purpose-designed chelators in development show promise for suppressing microbial pathogen and cancer cell growth, and also for relieving iron-induced toxicity in neurological and other diseases. Hepcidin and hepcidin agonists are also showing promise for relieving iron dysregulation. Harnessing iron-driven reactive oxygen species (ROS) generation with ferroptosis has shown promise for selective destruction of cancer cells. We review biological iron requirements, iron regulation and the nature of iron dysregulation in various diseases. Current results pertaining to potential new therapies are also reviewed.

Identification of iron metabolism-related genes as diagnostic signatures in sepsis by blood transcriptomic analysis

Iron metabolism is considered to play the principal role in sepsis, but the key iron metabolism-related genetic signatures are unclear. In this study, we analyzed and identified the genetic signatures related to the iron-metabolism in sepsis by using a bioinformatics analysis of four transcriptomic datasets from the GEO database. A total of 21 differentially expressed iron metabolism-related signatures were identified including 9 transporters, 8 enzymes, and 4 regulatory factors. Among them, lipocalin 2 was found to have the highest diagnostic value as its expression showed significant differences in all the comparisons including sepsis vs healthy controls, sepsis vs non-sepsis diseases, and mild forms vs severe forms of sepsis. Besides, the cytochrome P450 gene CYP1B1 also showed diagnostic values for sepsis from the non-sepsis diseases. The CYP4V2, LTF, and GCLM showed diagnostic values for distinguishing the severe forms from mild forms of sepsis. Our analysis identified 21 sepsis-associated iron metabolism-related genetic signatures, which may represent diagnostic and therapeutic biomarkers of sepsis, and will improve our understanding of the molecular mechanism underlying the occurrence of sepsis.

Targeting Iron Metabolism and Ferroptosis as Novel Therapeutic Approaches in Cardiovascular Diseases

Iron functions as an essential micronutrient and participates in normal physiological and biochemical processes in the cardiovascular system. Ferroptosis is a novel type of iron-dependent cell death driven by iron accumulation and lipid peroxidation, characterized by depletion of glutathione and suppression of glutathione peroxidase 4 (GPX4). Dysregulation of iron metabolism and ferroptosis have been implicated in the occurrence and development of cardiovascular diseases (CVDs), including hypertension, atherosclerosis, pulmonary hypertension, myocardial ischemia/reperfusion injury, cardiomyopathy, and heart failure. Iron chelators deferoxamine and dexrazoxane, and lipophilic antioxidants ferrostatin-1 and liproxstatin-1 have been revealed to abolish ferroptosis and suppress lipid peroxidation in atherosclerosis, cardiomyopathy, hypertension, and other CVDs. Notably, inhibition of ferroptosis by ferrostatin-1 has been demonstrated to alleviate cardiac impairments, fibrosis and pathological remodeling during hypertension by potentiating GPX4 signaling. Administration of deferoxamine improved myocardial ischemia/reperfusion injury by inhibiting lipid peroxidation. Several novel small molecules may be effective in the treatment of ferroptosis-mediated CVDs. In this article, we summarize the regulatory roles and underlying mechanisms of iron metabolism dysregulation and ferroptosis in the occurrence and development of CVDs. Targeting iron metabolism and ferroptosis are potential therapeutic strategies in the prevention and treatment of hypertension and other CVDs.

Exploring Dysregulated Ferroptosis-Related Genes in Septic Myocardial Injury Based on Human Heart Transcriptomes: Evidence and New Insights

Introduction

Sepsis is currently a common condition in emergency and intensive care units, and is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Cardiac dysfunction caused by septic myocardial injury (SMI) is associated with adverse prognosis and has significant economic and human costs. The pathophysiological mechanisms underlying SMI have long been a subject of interest. Recent studies have identified ferroptosis, a form of programmed cell death associated with iron accumulation and lipid peroxidation, as a pathological factor in the development of SMI. However, the current understanding of how ferroptosis functions and regulates in SMI remains limited, particularly in the absence of direct evidence from human heart.

Methods

We performed a sequential comprehensive bioinformatics analysis of human sepsis cardiac transcriptome data obtained through the GEO database. The lipopolysaccharide-induced mouse SMI model was used to validate the ferroptosis features and transcriptional expression of key genes.

Results

We identified widespread dysregulation of ferroptosis-related genes (FRGs) in SMI based on the human septic heart transcriptomes, deeply explored the underlying biological mechanisms and crosstalks, followed by the identification of key functional modules and hub genes through the construction of protein-protein interaction network. Eight key FRGs that regulate ferroptosis in SMI, including HIF1A, MAPK3, NOX4, PPARA, PTEN, RELA, STAT3 and TP53, were identified, as well as the ferroptosis features. All the key FRGs showed excellent diagnostic capability for SMI, part of them was associated with the prognosis of sepsis patients and the immune infiltration in the septic hearts, and potential ferroptosis-modulating drugs for SMI were predicted based on key FRGs.

Conclusion

This study provides human septic heart transcriptome-based evidence and brings new insights into the role of ferroptosis in SMI, which is significant for expanding the understanding of the pathobiological mechanisms of SMI and exploring promising diagnostic and therapeutic targets for SMI.

Association of whole blood metals/metalloids with severity in sepsis patients: A prospective, single-center, pilot study

BACKGROUND

Trace metals/metalloids were important for the biological functions of both the eukaryotic host and the microorganism. Their concentrations and variations may associate with the critical illness in sepsis, which still needs to be investigated.

METHODS

We performed a prospective cohort study on the patients with sepsis admitted to Tongji hospital (Wuhan, China) from Jul 01 to Dec 31, 2021. Sepsis was diagnosed in accordance with the third international consensus definitions for sepsis and septic shock (Sepsis-3). The concentrations of metals/metalloids including magnesium (Mg), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), mercury (Hg), thallium (Tl) and lead (Pb) in whole blood were analyzed by ICP-MS based methods.

RESULTS

Compared to the healthy controls, patients with sepsis showed higher levels of Ca, Cr and Cu, and lower levels of Mg, Mn, Fe, Zn, As, Hg and Pb. Further analysis between the critical illness and noncritical illness, revealed the Mn, Fe were significantly lower in the critically-ill sepsis. The longitudinal profile of the two metals show the differences appeared to exist almost throughout the clinical course. By performing the binary regression logistic analysis, we determined the Fe, Mn as independently risk factors for critical illness in sepsis, with effect sizes (β) of 17.14 (95%CI: 1.79-163.81) and 10.83 (1.96-59.83), respectively, which collectively discriminated 83.3% of all cases between critical-illness and non-critically illness.

CONCLUSIONS

The variations of whole blood metals/metalloids were associated with the critically-ill sepsis.

Iron-dependent ferroptosis participated in benzene-induced anemia of inflammation through IRP1-DHODH-ALOX12 axis

Benzene, a widely existing environmental pollutant, gives huge harm to the hematopoietic system. Iron is one of the raw materials for the creation of blood cells, but the role of iron in the blood toxicity of benzene is still unknown. Here, we examined the role of iron homeostasis in benzene-induced toxicity both in vivo and in vitro. In this study, mice exposed to benzene at 50 ppm for 8 weeks demonstrated the anemia of inflammation, mainly manifested as the decreased serum Fe²⁺, increased serum ferritin and inflammation factors (TNF-α, IL6, IL1β) in the plasma of mice. Furthermore, we found that iron maldistribution in the spleen and bone marrow is accompanied by inflammation reaction and ferroptosis. In the vitro study, benzene metabolite 1,4-BQ stimulated the obvious ROS production and ferroptosis activation in the normal B lymphocytes cells. Meanwhile, from the molecular perspective, the combined proteomics and transcriptome enriched the ferroptosis pathway, and we further confirmed the increased expression of iron regulator IRP1, ferroptosis-regulator DHODH, and fatty acids metabolism enzyme ALOX12 were the crucial participators in regulating benzene-mediated iron metabolism imbalance and ferroptosis. Particularly, the targeted and un-targeted metabolomics in the vivo and vitro study further emphasized the importance of DHODH in benzene-induced ferroptosis. In conclusion, this study revealed that iron-dependent ferroptosis participated in benzene-induced anemia of inflammation and provided a constructive perspective on targeting ferroptosis for the prevention and control of benzene toxicity.

Identification of Molecular Subtypes and a Novel Prognostic Model of Sepsis Based on Ferroptosis-Associated Gene Signature

Ferroptosis has recently been associated with immunological changes in sepsis. However, the clinical significance of ferroptosis-associated genes (FAGs) remains unknown. In this paper, a FAG-based prognostic model was constructed for sepsis patients using an integrated machine learning approach. The prognosis model was composed of 14 FAGs that classify the patients as high or low risk. Based on immunological study, it was found that the immune status differed between the high-risk and low-risk clusters. Cox regression analysis revealed that FAGs were independent risk factors for the overall survival of sepsis patients. ROC curves and nomograms revealed that the FAG-based model was robust for prognosis prediction. Lastly, NEDD4L was identified from the 14 FAGs as a potential hub gene for sepsis prediction.

Screening of potential key ferroptosis-related genes in sepsis

Background

Sepsis leads to multiple organ dysfunction caused by a dysregulated host response to infection with a high incidence and mortality. The effect of ferroptosis on the development of sepsis remains unclear. In this study, we aimed to identify the key ferroptosis-related genes involved in sepsis and further explore the potential biological functions of these ferroptosis-related genes in sepsis using bioinformatics analysis.

Methods

The GSE13904 (from children) and GSE28750 (from adults) datasets were downloaded from the Gene Expression Omnibus (GEO). The ferroptosis-related genes were obtained from the FerrDb database. The ferroptosis-related differentially expressed genes (DEGs) were screened by the limma R package. The DAVID online database or clusterProfiler R package was used for the functional enrichment analysis. Then, the STRING database was used to predict the interactions of proteins, and the CytoHubba plugin of Cytoscape was used to confirm key clustering modules. Then, the miRNAs and lncRNAs associated with the key clustering modules were predicted by miRWalk 2.0 and LncBase v.2 respectively. Finally, we generated a cecal ligation and puncture (CLP) polymicrobial sepsis model in C57 male mice and examined the expression of the mRNAs and noncoding RNAs of interest in peripheral blood leukocytes by PCR during the acute inflammation phase.

Results

In total, 34 ferroptosis-related DEGs were identified in both adult and pediatric septic patients. These ferroptosis-related DEGs were mainly enriched in inflammatory pathways. Then, a significant clustering module containing eight genes was identified. Among them, the following five genes were closely associated with the MAPK signaling pathway: MAPK14, MAPK8, DUSP1, MAP3K5 and MAPK1. Then, crucial miRNAs and lncRNAs associated with biomarker MAPK-related genes were also identified. In particular, let-7b-5p and NEAT1 were selected as noncoding RNAs of interest because of their correlation with ferroptosis in previous studies. Finally, we examined the mRNAs, miRNAs and lncRNAs of interest using CLP-induced sepsis in peripheral blood leukocytes of mice. The results showed that MAPK14, MAPK8, MAP3K5, MAPK1 and NEAT1 were upregulated, while DUSP1 and let-7b-5p were downregulated in the CLP group compared with the sham group.

Conclusions

The MAPK signaling pathway may play a key role in regulating ferroptosis during sepsis. This study provides a valuable resource for future studies investigating the mechanism of MAPK-related ferroptosis in sepsis.

Ferroptosis and its emerging roles in acute pancreatitis

ABSTRACT

Acute pancreatitis (AP) is a common and potentially life-threatening pancreatic inflammatory disease. Although it is usually self-limiting, up to 20% of patients will develop into severe AP. It may lead to systemic inflammatory response syndrome and multiple organ dysfunction, affecting the lungs, kidneys, liver, heart, etc. Surviving patients usually have sequelae of varying degrees, such as chronic hyperglycemia after AP (CHAP), pancreatic exocrine insufficiency, and chronic pancreatitis. Lacking specific target treatments is the main reason for high mortality and morbidity, which means that more research on the pathogenesis of AP is needed. Ferroptosis is a newly discovered regulated cell death (RCD), originally described in cancer cells, involving the accumulation of iron and the depletion of plasma membrane polyunsaturated fatty acids, and a caspase-independent RCD. It is closely related to neurological diseases, myocardial infarction, ischemia/reperfusion injury, cancer, etc. Research in the past years has also found the effects of ferroptosis in AP, pancreatic cancer, and AP complications, such as acute lung injury and acute kidney injury. This article reviews the research progress of ferroptosis and its association with the pathophysiological mechanisms of AP, trying to provide new insight into the pathogenesis and treatment of AP, facilitating the development of better-targeted drugs.

Fluorene methoxycarbonyl-PEG-deferoxamine conjugates "hitchhike" with albumin in situ for iron overload therapy

Although deferoxamine (DFO) has been approved for the treatment the iron overloaded diseases, its clinical application is impeded by very short circulation time and its relating toxicity. In this work, the fluorene methoxycarbonyl (FMOC) for "albumin hitchhiking" was used to prolong the plasma circulation time of DFO and reduce toxicity. The designed FMOC-PEG-DFO conjugates were found to reversible bind to albumin and gradually release DFO in vivo. Herein, the FMOC-PEG₁₀₀₀-DFO conjugates could increase 30 times the blood circulation time of DFO with the improvement of the iron elimination efficacy. Meanwhile, the conjugates markedly reduced the cytotoxicity of DFO. Taken together, the result demonstrated the FMOC-PEG₁₀₀₀-DFO conjugates could be a potential therapeutic choice for iron-overload-related diseases.

Ferroptosis in sepsis: The mechanism, the role and the therapeutic potential

Sepsis is a common critical illness in the Intensive care unit(ICU) and its management and treatment has always been a major challenge in critical care medicine. The dysregulated host response to infection, causing systemic multi-organ and multi-system damage is the main pathogenesis. Notably, intense stress during sepsis can lead to metabolic disturbances of ions, lipids and energy in the organism. Ferroptosis is an iron-dependent, non-apoptotic cell death distinguished by a disruption of iron metabolism and iron-dependent accumulation of lipid peroxides. Mounting researches have established that ferroptosis has an essential part in anti-inflammatory and sepsis, and drugs targeting ferroptosis-related molecules, such as ferroptosis inhibitors, are gradually proving their effectiveness in sepsis. This paper summarizes and reviews the pathogenesis of ferroptosis, its regulatory network, and its vital involvement in the initiation of sepsis and related organ damage, and finally discusses the possible target drugs provided by the above mechanisms, describes the dilemmas as well as the outlook, in the hope of finding more links between ferroptosis and sepsis and providing new perspectives for the future treatment of sepsis.

Cardiomyocyte death in sepsis: Mechanisms and regulation (Review)

Sepsis‑induced cardiac dysfunction is one of the most common types of organ dysfunction in sepsis; its pathogenesis is highly complex and not yet fully understood. Cardiomyocytes serve a key role in the pathophysiology of cardiac function; due to the limited ability of cardiomyocytes to regenerate, their loss contributes to decreased cardiac function. The activation of inflammatory signalling pathways affects cardiomyocyte function and modes of cardiomyocyte death in sepsis. Prevention of cardiomyocyte death is an important therapeutic strategy for sepsis‑induced cardiac dysfunction. Thus, understanding the signalling pathways that activate cardiomyocyte death and cross‑regulation between death modes are key to finding therapeutic targets. The present review focused on advances in understanding of sepsis‑induced cardiomyocyte death pathways, including apoptosis, necroptosis, mitochondria‑mediated necrosis, pyroptosis, ferroptosis and autophagy. The present review summarizes the effect of inflammatory activation on cardiomyocyte death mechanisms, the diversity of regulatory mechanisms and cross‑regulation between death modes and the effect on cardiac function in sepsis to provide a theoretical basis for treatment of sepsis‑induced cardiac dysfunction.

The liver in sepsis: molecular mechanism of liver failure and their potential for clinical translation

Liver failure is a life-threatening complication of infections restricting the host's response to infection. The pivotal role of the liver in metabolic, synthetic, and immunological pathways enforces limits the host's ability to control the immune response appropriately, making it vulnerable to ineffective pathogen resistance and tissue damage. Deregulated networks of liver diseases are gradually uncovered by high-throughput, single-cell resolved OMICS technologies visualizing an astonishing diversity of cell types and regulatory interaction driving tolerogenic signaling in health and inflammation in disease. Therefore, this review elucidates the effects of the dysregulated host response on the liver, consequences for the immune response, and possible avenues for personalized therapeutics.

The interaction between STING and NCOA4 exacerbates lethal sepsis by orchestrating ferroptosis and inflammatory responses in macrophages

The discovery of STING-related innate immunity has recently provided a deep mechanistic understanding of immunopathy. While the detrimental effects of STING during sepsis had been well documented, the exact mechanism by which STING causes lethal sepsis remains obscure. Through single-cell RNA sequence, genetic approaches, and mass spectrometry, we demonstrate that STING promotes sepsis-induced multiple organ injury by inducing macrophage ferroptosis in a cGAS- and interferon-independent manner. Mechanistically, Q237, E316, and S322 in the CBD domain of STING are critical binding sites for the interaction with the coiled-coil domain of NCOA4. Their interaction not only triggers ferritinophagy-mediated ferroptosis, but also maintains the stability of STING dimers leading to enhanced inflammatory response, and reduces the nuclear localization of NCOA4, which impairs the transcription factor coregulator function of NCOA4. Meanwhile, we identified HET0016 by high throughput screening, a selective 20-HETE synthase inhibitor, decreased STING-induced ferroptosis in peripheral blood mononuclear cells from patients with sepsis and mortality in septic mice model. Our findings uncover a novel mechanism by which the interaction between STING and NCOA4 regulates innate immune response and ferroptosis, which can be reversed by HET0016, providing mechanistic and promising targets insights into sepsis.

Alteration of osteoclast activity in childhood cancer survivors: Role of iron and of CB2/TRPV1 receptors

Childhood cancer survivors (CCS) are predisposed to the onset of osteoporosis (OP). It is known that iron overload induces osteoclasts (OCs) overactivity and that the iron chelator Deferasirox (DFX) can counteract it. The Cannabinoid Receptor type 2 (CB2) and the transient receptor potential vanilloid type-1 (TRPV1) are potential therapeutic targets for OP. In this study we isolated OCs from peripheral blood of 20 CCS and investigated osteoclast biomarkers expression and iron metabolism evaluating iron release by OCs and the expression of several molecules involved in its regulation. Moreover, we analyzed the effects of CB2 and TRPV1 stimulation in combination with DFX on osteoclast activity and iron metabolism. We observed, for the first time, an osteoclast hyperactivation in CCS suggesting a role for iron in its development. Moreover, we confirmed the well-known role of CB2 and TRPV1 receptors in bone metabolism, suggesting the receptors as possible key biomarkers of bone damage. Moreover, we demonstrated a promising synergism between pharmacological compounds, stimulating CB2 or inhibiting/desensitizing TRPV1 and DFX, in counteracting osteoclast overactivity in CCS to improve their quality of life.

Contribution of prognostic ferroptosis-related subtypes classification and hub genes of sepsis

BACKGROUND

Sepsis in patients is a great threat to human health due to its high incidence rate, its rapid and unpredictable progression, as well as it is difficult to treat, and it has poor prognosis. Ferroptosis is a newly discovered type of cell death characterized by the iron-dependent peroxide aggregation. Furthermore, ferroptosis is different from other forms of cell death, namely apoptosis, necrosis, pyroptosis and autophagy. Our study investigated the role of ferroptosis-related genes in sepsis.

METHODS

The GSE65682 dataset from the Gene Expression Omnibus (GEO) database was used to screen ferroptosis-related genes associated with sepsis, and the GSE134347 dataset for the external validation of selected hub genes. The univariate Cox regression analysis, Kaplan-Meier (K-M) survival analysis and weighted gene co-expression network analysis (WGCNA) were used to identify hub genes. Evaluation of the immune cell infiltration in sepsis was used to explain the immune heterogeneity among the cell subtypes. Gene set variation analysis (GSVA) and transcriptional regulatory analysis of selected hub genes further elucidated the probable mechanism of ferroptosis-related genes associated with prognosis in sepsis. Finally, we constructed a competing endogenous RNA (ceRNA) network model.

RESULTS

A total of 479 RNA-seq data points were used for analysis, including 365 samples from patients who survived sepsis and 114 samples from patients who succumbed to sepsis from the available GSE65682 dataset. Consequently, the univariate Cox regression analysis and consensus clustering analysis divide all 479 sepsis samples into two clusters of "survivals" vs. "non-survivals". Following complex analysis were identified as the most important ferroptosis-related genes. Indeed, the WGCNA and K-M analyses associated the expression patterns of NEDD4L and SIAH2 hub genes as the best prognosis for the survival of sepsis (p < 0.05). The expression trend was also consistent with the survival trend of the NEDD4L and SIAH2 hub genes by the external validation of GSE134347 (p < 0.05). Immune cell infiltration analysis indicated that the types and numbers of different immune cells vary among different subtypes and NEDD4L and SIAH2 hub genes. For example, NEDD4L and SIAH2 gene expression had a positive correlation with M0 macrophages and a negative correlation with neutrophils (p > 0.05). Finally, analysis of two hub genes and transcription factors (TFs) showed that 71 TFs were predicted to be related to NEDD4L while 64 TFs to SIAH2 by the Cistrome DB online database.

CONCLUSION

We suggest that NEDD4L and SIAH2 hub genes are involved in the ferroptosis-associated sepsis. The pattern of NEDD4L and SIAH2 expression in patients undergoing sepsis may have prognostic potential for the severity of sepsis and eventually for patients' survival.

Resveratrol mediates the miR-149/HMGB1 axis and regulates the ferroptosis pathway to protect myocardium in endotoxemia mice

Endotoxemia is a common complication often used to model the acute inflammatory response associated with endotoxemia. Resveratrol has been shown to exert a wide range of therapeutic effects due to its anti-inflammatory and antioxidant properties. This study explored the effect of resveratrol on endotoxemia. Lipopolysaccharide (LPS)-induced endotoxemia mouse model and endotoxemia myocardial injury cell model were established and treated with resveratrol. Cardiomyocyte activity, lactate dehydrogenase (LDH) content in cell supernatant, glutathione (GSH) consumption, lipid reactive oxygen species (ROS) production, and iron accumulation were detected. Cardiac function indexes [left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), ejection fraction (EF)%, and fractional shortening (FS)%] were measured using echocardiography. The creatine kinase muscle/brain isoenzyme (CK-MB) and CK levels in the serum were detected using an automatic biochemical analyzer. The downstream target of miR-149 was predicted, and the binding relationship between miR-149 and high mobility group box 1 (HMGB1) was verified using a dual-luciferase assay. miR-149 and HMGB1 expressions were detected using RT-qPCR and Western blot. After resveratrol treatment, cardiomyocyte viability and GSH were increased, and LDH secretion, lipid ROS production, lipid peroxidation, and iron accumulation were decreased, and cardiac function and cardiomyocyte injury were improved. Resveratrol improved LPS-induced endotoxemia cardiomyocyte injury by upregulating miR-149 and inhibiting ferroptosis. Resveratrol inhibited HMGB1 expression by upregulating miR-149. HMGB1 upregulation reversed the inhibitory effect of miR-149 on LPS-induced ferroptosis in cardiomyocytes. Resveratrol upregulated miR-149 and downregulated HMGB1 to inhibit ferroptosis and improve myocardial injury in mice with LPS-induced endotoxemia. Collectively, resveratrol upregulated miR-149, downregulated HMGB1, and inhibited the ferroptosis pathway, thus improving cardiomyocyte injury in LPS-induced endotoxemia.NEW & NOTEWORTHY Sepsis is an unusual systemic reaction. Resveratrol is involved in sepsis treatment. This study explored the mechanism of resveratrol in sepsis by regulating the miR-149/HMGB1 axis.

Deferiprone: A Forty-Year-Old Multi-Targeting Drug with Possible Activity against COVID-19 and Diseases of Similar Symptomatology

The need for preparing new strategies for the design of emergency drug therapies against COVID-19 and similar diseases in the future is rather urgent, considering the high rate of morbidity and especially mortality associated with COVID-19, which so far has exceeded 18 million lives. Such strategies could be conceived by targeting the causes and also the serious toxic side effects of the diseases, as well as associated biochemical and physiological pathways. Deferiprone (L1) is an EMA- and FDA-approved drug used worldwide for the treatment of iron overload and also other conditions where there are no effective treatments. The multi-potent effects and high safety record of L1 in iron loaded and non-iron loaded categories of patients suggests that L1 could be developed as a “magic bullet” drug against COVID-19 and diseases of similar symptomatology. The mode of action of L1 includes antiviral, antimicrobial, antioxidant, anti-hypoxic and anti-ferroptotic effects, iron buffering interactions with transferrin, iron mobilizing effects from ferritin, macrophages and other cells involved in the immune response and hyperinflammation, as well as many other therapeutic interventions. Similarly, several pharmacological and other characteristics of L1, including extensive tissue distribution and low cost of production, increase the prospect of worldwide availability, as well as many other therapeutic approach strategies involving drug combinations, adjuvant therapies and disease prevention.

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

Acetaminophen alleviates ferroptosis in mice with sepsis-associated encephalopathy via the GPX4 pathway

Sepsis-associated encephalopathy (SAE) is a cognitive impairment caused by sepsis, associated with increased morbidity and death. And acetaminophen (APAP) is a promising therapeutic medicine for SAE treatment. This research was designed to determine whether APAP alleviates SAE by attenuating ferroptosis and mediating the glutathione peroxidase (GPX4) pathway. The cecal ligation and puncture (CLP) approach was used to establish septic mouse models. The survival rates for 7 days were determined. The Morris water maze (MWM) was utilized to assess cognitive function. Hematoxylin and eosin (HE) staining identified histopathologic alterations in hippocampal tissue. Mitochondrial damage was discovered in hippocampal tissue using transmission electron microscopy (TEM). The reactive oxygen (ROS) levels in hippocampal tissue were measured using commercial assays. Septic cell models were produced using HT22 cells grown with 1 μg/ml lipopolysaccharide (LPS). ROS were quantified using immunofluorescence. Ferroptosis-related protein expression levels in hippocampal tissue and HT22 cells were measured using western blotting. To evaluate the iron content of hippocampal tissue and HT22 cells, commercial kits were employed. According to the findings, APAP improved survival rates, lowered hippocampal and mitochondrial damage, and improve cognitive impairment. In both animal and cell studies, APAP reduced iron content, ROS, glutamate antiporter (xCT), 4-hydroxy-2-nonenal (4-HNE) levels but increased GPX4 expression. However, RSL3, a GPX4 inhibitor that acts as a ferroptosis activator, decreased the protective properties of APAP in vitro. Our findings suggest that APAP reduces sepsis-induced cognitive impairment by reducing ferroptosis, which is mediated by the GPX4 signaling pathway.

Ferrostatin-1 alleviates lipopolysaccharide-induced cardiac dysfunction

Cardiac dysfunction is a common complication of sepsis, and is attributed to severe inflammatory responses. Ferroptosis is reported to be involved in sepsis-induced cardiac inflammation. Therefore, we speculated that ferrostatin-1 (Fer-1), a ferroptosis inhibitor, improves cardiac dysfunction caused by sepsis. An intraperitoneal injection of lipopolysaccharide (LPS) was performed to induce a rat cardiac dysfunction model. Echocardiography, cardiac histopathology, biochemical and western blot results were analyzed. Twelve hours after the LPS injection, LPS-treated rats exhibited deteriorating cardiac systolic function, increased levels of cardiac injury markers and levels of ferroptosis markers prostaglandin endoperoxide synthase 2 (PTGS2). Additionally, LPS increased iron deposition in the myocardium, with downregulating ferroportin (FPN, SLC40A1) and transferrin receptor (TfR)expression, and upregulating ferritin light chain (FTL) and ferritin heavy chain (FTH1) expression. Meanwhile, LPS also increased lipid peroxidation in the rat heart by decreasing the expression of glutathione peroxidase 4 (GPX4). Moreover, the expression of inflammatory cytokines, such as tumor necrosis-alpha (TNF-α), interleukin-1 (IL-1β), and interleukin-6 (IL-6), and inflammatory cell infiltration were also increased following LPS challenge. Finally, the abovementioned adverse effects of LPS were relieved by Fer-1 except for TfR expression. Mechanistically, Fer-1 significantly reduced the levels of toll-like receptor 4 (TLR4), phospho-nuclear factor kappa B (NF-κB), and phospho-inhibitor of kappa Bα (IκBα) in LPS-treated rats. In summary, these findings imply that Fer-1 improved sepsis-induced cardiac dysfunction at least partially via the TLR4/NF-κB signaling pathway.