Lipocalin-2 in neutrophils induces ferroptosis in septic cardiac dysfunction via increasing labile iron pool of cardiomyocytes

Lipocalin-2-mediated ferroptosis as a target for protection against light-induced photoreceptor degeneration

BACKGROUND

Retinal degeneration is a leading cause of blindness worldwide. The induction of ferroptosis has been identified as an important mechanism contributing to the loss of photoreceptors in retinal degeneration. Lipocalin-2 (LCN2) exhibits iron-regulatory properties and may modulate cell viability in various diseases. However, the effects of LCN2 on ferroptosis in retinal degeneration remain unclear.

METHODS

A light-induced injury model using 661W photoreceptor cells and a light-induced retinal degeneration male rat model were established. LCN2 protein expression was assessed by western blotting. The effects of LCN2 on ferroptosis in vitro were investigated by using recombinant LCN2 protein (rLCN2) and small-interfering RNA (siRNA) targeting LCN2 (siLCN2). Fe2+, malondialdehyde (MDA), tripeptide glutathione (GSH) levels, and the expression of ferroptosis-associated proteins (solute carrier family 7 member 11 [SLC7A11] and glutathione peroxidase-4 [GPX4]) were measured. A phosphokinase array and western blotting were performed to elucidate the mechanisms underlying LCN2-modulated photoreceptor ferroptosis. Additionally, the protective effects of LCN2 knockdown using adeno-associated virus (AAV)-expressing short hairpin RNA (shRNA) targeting LCN2 (AAV-shRNA-LCN2) on retinal structure and function in vivo were evaluated by hematoxylin and eosin staining and electroretinography.

RESULTS

LCN2 expression was significantly upregulated following light exposure. Treatment with rLCN2 significantly induced ferroptosis in photoreceptor cells, as shown by decreased cell viability, increased Fe2+ levels, inhibition of SLC7A11 and GPX4 expression, depletion of GSH, and enhanced MDA levels, whereas siLCN2 protected against these effects. Exposure of photoreceptor cells to rLCN2 activated c-Jun N-terminal kinase (JNK), and administration of the JNK inhibitor SP600125 protected photoreceptor cells from ferroptosis. Lastly, AAV-shRNA-LCN2 administration inhibited light-induced ferroptosis in the retina, and protected the retinal structure and function in vivo.

CONCLUSION

LCN2 is a key regulator of light-induced ferroptosis in photoreceptors by modulating the JNK pathway. Therefore, LCN2 presents a new target for the treatment of retinal degeneration.

Advances in neutrophil extracellular traps and ferroptosis in sepsis-induced cardiomyopathy

Sepsis-induced cardiomyopathy is a reversible non-ischemic acute cardiac dysfunction associated with sepsis. It is strongly associated with an abnormal immune response. It emerges as a vital threat to public health owing to its high mortality rate. However, the exact pathogenesis requires further investigation. In recent years, NETosis and ferroptosis, which are novel modes of programmed cell death, have been identified and found to play important roles in sepsis-related organ damage. This article outlines the mechanisms of these two modes of cell death, discusses the role of neutrophil extracellular traps in myocardial injury and the importance of ferroptosis in sepsis-induced cardiomyopathy, and reviews the potential interconnection between these two types of programmed cell death in sepsis-induced cardiomyopathy.

Lipocalin-2 as a fundamental protein in type 2 diabetes and periodontitis in mice

BACKGROUND

Lipocalin-2 (LCN-2) is an osteokine that suppresses appetite, stimulates insulin secretion, regulates bone remodeling, and is induced by proinflammatory cytokines. The aim of this work was to investigate the participation of LCN-2 in periodontitis associated with type 2 diabetes (T2D) by evaluating alveolar bone loss, glycemic control, inflammation, and femur fragility.

METHODS

A murine model of periodontitis with T2D and elevated LCN-2 concentration was used. Functional LCN-2 inhibition was achieved using an anti-LCN-2 polyclonal antibody, and isotype immunoglobulin G was used as a control. The alveolar bone and femur were evaluated by micro-CT. Glucose metabolism was determined. Tumor necrosis factor (TNF-α) and receptor activator of nuclear factor kappa-B ligand (RANKL) levels in alveolar bone lysates were quantified using ELISA, and serum cytokines were quantified using flow cytometry. A three-point bending test was performed in the femur, and RANKL levels were measured in femur lysates using ELISA.

RESULTS

Functional inhibition of LCN-2 in T2D-periodontitis mice decreased alveolar bone loss in buccal and palatal surfaces and preserved the microarchitecture of the remaining bone, decreased TNF-α and RANKL in alveolar bone, reduced hyperglycemia, glucose intolerance, and insulin resistance, and increased insulin production through improving the functionality of pancreatic β cells. Furthermore, this inhibition increased serum free-glycerol levels, decreased serum interleukin (IL)-6, increased serum IL-4, and reduced femur fragility and RANKL expression in the femur.

CONCLUSIONS

LCN-2 participates in periodontitis associated with T2D. Inhibiting its function in mice with T2D and periodontitis improves pancreatic β-cell function, and glucose metabolism and decreases inflammatory cytokines and bone-RANKL levels, which results in the preservation of femoral and alveolar bone microarchitecture.

PLAIN LANGUAGE SUMMARY

In this study, we explored the role of a bone protein known as lipocalin-2 (LCN-2) in the connection between periodontitis and type 2 diabetes (T2D). Periodontitis is a destructive gum and alveolar bone disease. LCN-2 levels are increased in both T2D and periodontitis. Using a mouse model of T2D with periodontitis, we examined how blocking LCN-2 function affected various aspects of these two diseases. We found that this inhibition led to significant improvements. First, it reduced alveolar bone loss and preserved bone structure by decreasing local inflammation and bone resorption. Second, it improved glucose and lipid metabolism, leading to better blood-sugar control and decreased insulin resistance. Blocking the functions of LCN-2 also decreased systemic inflammation throughout the body and strengthened bone integrity. Overall, our results suggest that LCN-2 plays a crucial role in the periodontitis associated with T2D. By inhibiting LCN-2 function, we were able to improve pancreatic function, improve glucose metabolism, reduce inflammation, and enhance bone health. Targeting LCN-2 could be a promising strategy for the harmful effects of T2D and periodontitis.

WTX-L/β-arrestin2/LCN2 axis controls vulnerability to ferroptosis in gastric cancer

Gastric cancer (GC) is one of the most prevalent and lethal cancers worldwide. Ferroptosis is a form of iron-dependent regulated cell death emerging as a promising strategy for cancer therapy, whereas the regulation mechanism remains unclear. WTX has been recognized as a potential tumor suppressor, but attempts at targeted therapy have not achieved substantial progress. Further research into the structure, function, and mechanisms is urgently needed. Herein, we identified a long isoform of WTX (WTX-L) as a potent ferroptosis effector in GC. Mechanistically, WTX-L competitively interacts with β-arrestin2, disrupting its direct binding to IκBα and subsequently activating the NF-κB/LCN2 pathway. LCN2 further triggers ferroptosis by significantly increasing the labile Fe2+ pool and promoting excessive lipid peroxidation. Blockade of the WTX-L/β-arrestin2/NF-κB/LCN2 axis significantly diminished the activity of ferroptosis inducers (erastin and RSL3) in vivo. Collectively, these findings reveal that targeting the ferroptosis vulnerabilities through WTX-L may represent a promising strategy for GC.

IRF7 Activates LCN2 Transcription to Enhance LPS-Induced Acute Lung Injury by Inducing Macrophage Ferroptosis and M1 Polarization

Acute lung injury (ALI), a severe pulmonary disorder that poses a significant threat to life, is closely associated with macrophage ferroptosis and polarization. Lipocalin 2 (LCN2) has been previously reported to be implicated in the pathogenesis of ALI. However, the specific role of LCN2 in macrophage ferroptosis and polarization remains undetermined. Lipopolysaccharide (LPS) was used to establish a mouse model of ALI and also to stimulate mouse RAW264.7 cells. H&E staining was used for histopathologic evaluation, and immunohistochemistry analysis was used to determine the 4-HNE-positive cells. The secretion levels of TNF-α, IL-6, and IL-1β were assessed by ELISA. Gene and protein expression assays were performed using quantitative PCR and immunoblotting. The levels of MDA, GSH, ROS, and lipid ROS were detected to evaluate the alteration in ferroptosis. CD86+ and CD206+ cells were quantified by flow cytometry. The relationship between LCN2 and interferon regulatory factor 7 (IRF7) was confirmed by chromatin immunoprecipitation (ChIP) and luciferase reporter assays. LCN2 expression was upregulated in the lungs of LPS-induced ALI mice and LPS-stimulated RAW264.7 cells. In LPS-induced ALI mice, the depletion of LCN2 alleviated lung injury and ferroptosis, and also inhibited inflammation and macrophage M1 polarization. In LPS-stimulated RAW264.7 cells, the depletion of LCN2 suppressed ferroptosis, inflammation, and M1 polarization. Mechanistically, IRF7 enhanced LCN2 transcription in RAW264.7 cells by binding to its promoter region. More importantly, the silencing of IRF7 inhibited ferroptosis and M1 polarization in LPS-stimulated RAW264.7 cells by downregulating LCN2. Taken together, the IRF7/LCN2 cascade enhances the ferroptosis and M1 polarization of LPS-stimulated macrophages, thereby exacerbating ALI. Anti-IRF7 and anti-LCN2 therapies might potentially be exploited for the prevention and treatment in ALI.

Ablation of lipocalin-2 reduces neuroinflammation in a mouse model of Krabbe disease

Lipocalin-2 (LCN2) is an acute-phase secretory molecule significantly upregulated in various neuroinflammatory and demyelinating conditions. Krabbe disease (KD) is a neurodegenerative lysosomal disorder caused by a galactosylceramidase (GALC) deficiency, accumulating cytotoxic psychosine in nervous systems, and subsequent neuroinflammation. Here, we show that LCN2 is highly overexpressed in GALC-deficient astrocytes. To further understand if the elevated LCN2 is critical for KD progression, we globally deleted Lcn2 in the Galc-knockout (KO) mouse model. Interestingly, the Galc and Lcn2 double KO mice showed dramatically reduced neuroinflammation including gliosis. Pro-inflammatory cytokines such as TNF-α, MMP3, and MCP-1 were significantly downregulated in the brain of the double KO mice compared to Galc-KO. In addition, the ablation of Lcn2 marginally increased the survival and attenuated disease progression in Galc-KO mice. However, the accumulation of psychosine was not altered in the brain by LCN2 deficiency. Our findings suggest that the upregulation of LCN2 is crucial for the aggravation of neuroinflammation in a mouse model of Krabbe disease.

Ferroptosisand Its Role in the Treatment of Sepsis-Related Organ Injury: Mechanisms and Potential Therapeutic Approaches

Sepsis is a complicated clinical disease caused by a defective host response to infection, leading to elevated morbidity and fatality globally. Sepsis patients have a significant risk of life-threatening organ damage, including hearts, brains, lungs, kidneys, and livers. Nevertheless, the molecular pathways driving organ injury in sepsis are not well known. Ferroptosis, a non-apoptotic cell death, occurs due to iron metabolism disturbance and lipid peroxide buildup. Multiple studies indicate that ferroptosis has a significant role in decreasing inflammation and lipid peroxidation during sepsis. Ferroptosis inhibitors and medications, aimed at the most studied ferroptosis process, including Xc-system, Nrf2/GPX4 axis, and NCOA4-FTH1-mediated ferritinophagy, alleviating sepsis effectively. However, few clinical trials demonstrated ferroptosis-targeted drugs's effectiveness in sepsis. Our study examines ferroptosis-targeted medicinal agents and their potential benefits for treating sepsis-associated organ impairment. This review indicates that ferroptosis suppression by pharmaceutical means may be a useful therapy for sepsis-associated organ injury.

Lipocalin-2 and intestinal diseases

Dysfunction of the intestinal barrier is a prevalent phenomenon observed across a spectrum of diseases, encompassing conditions such as mesenteric artery dissection, inflammatory bowel disease, cirrhosis, and sepsis. In these pathological states, the integrity of the intestinal barrier, which normally serves to regulate the selective passage of substances between the gut lumen and the bloodstream, becomes compromised. This compromised barrier function can lead to a range of adverse consequences, including increased permeability to harmful substances, the translocation of bacteria and their products into systemic circulation, and heightened inflammatory responses within the gut and beyond. Understanding the mechanisms underlying intestinal barrier dysfunction in these diverse disease contexts is crucial for the development of targeted therapeutic interventions aimed at restoring barrier integrity and ameliorating disease progression. Lipocalin-2 (LCN2) expression is significantly upregulated during episodes of intestinal inflammation, making it a pivotal indicator for gauging the extent of such inflammatory processes. Notably, however, LCN2 derived from distinct cellular sources, whether intestinal epithelial cells or immune cells, exhibits notably divergent functional characteristics. Furthermore, the multifaceted nature of LCN2 is underscored by its varying roles across different diseases, sometimes even demonstrating contradictory effects.

Ferrostatin-1 improves acute sepsis-induced cardiomyopathy via inhibiting neutrophil infiltration through impaired chemokine axis

Introduction

Sepsis-induced cardiomyopathy is a common complication of sepsis and is associated with higher mortality. To date, effective diagnostic and management strategies are still lacking. Recent studies suggest that ferroptosis plays a critical role in sepsis-induced cardiomyopathy and ferroptosis inhibitor Ferrostatin-1 (Fer-1) improved cardiac dysfunction and survival in lipopolysaccharide (LPS) induced endotoxemia. However, the effects of Fer-1 in cardiac dysfunction in the early stages of cecal ligation and puncture (CLP) induced sepsis remains unclear. Our study aims to elucidate the role of Fer-1 in the acute phase of peritonitis sepsis induced cardiac injury.

Methods and Results

CLP was used to induce peritonitis sepsis in mice. Pretreatment of ferroptosis inhibitor ferrostatin-1 (Fer-1) was used in the in vivo models. Survival was monitored for 48h. Cardiac function and histology were analyzed 6h after surgery. We found that ejection fraction (EF) remained normal at 6h after CLP, but the contractility detected by cardiac muscle strain analysis was significantly reduced, along with increased immune cell infiltration. Pretreating the CLP mice with 5 mg/kg Fer-1 significantly reduced mortality. At 6h after CLP, ferroptosis key regulator Gpx4, cardiac iron and malonaldehyde (MDA) did not change, but ferroptosis marker gene expression increased. Fer-1 treatment showed beneficial effects in cardiac function, less myocardial inflammatory cytokine expression and significantly inhibited immune cells, especially neutrophil infiltration in the heart. Consistently, expression of neutrophil associated chemokines (Ccrl2, Cxcl2, Cxcl3 and Cxcl5) as well as extracellular matrix (ECM) degradation enzymes (Adamts1, Adamts4, Adamts9 and Mmp8) significantly decreased in Fer-1 pre-treated CLP heart.

Conclusion and Discussion

Our findings suggest that Fer-1 inhibits neutrophil infiltration in early sepsis by disrupting the chemokine axis, highlighting its potential as a therapeutic option to manage acute immune overactivation in early stages of sepsis-induced cardiomyopathy.

Lipocalin-2 promotes CKD vascular calcification by aggravating VSMCs ferroptosis through NCOA4/FTH1-mediated ferritinophagy

Vascular calcification (VC) is a common complication of chronic kidney disease (CKD), for which no effective therapies are available. Hyperphosphatemia, a feature of CKD, is a well-known inducer of VC. High phosphate (HP)-induced ferroptosis plays a crucial role in CKD-related VC (CKD-VC), but the mechanisms remain unclear. Lipocalin-2 (LCN2), an iron-trafficking protein, has been implicated in ferroptosis regulation. In the present study, the role of LCN2 as a potential mediator of CKD-VC was investigated. HP-induced LCN2 expression in the arteries of CKD-VC patients, animal models and vascular smooth muscle cells (VSMCs). LCN2 knockout (LCN2KO) mice and wild-type (WT) mice fed with a high adenine and phosphate (AP) diet were studied to explore CKD-VC. Compared with WT mice, LCN2KO mice showed an amelioration of the CKD-VC induced by the AP diet. The inhibition of LCN2 also alleviated HP-induced calcium deposition and phenotypic transition in VSMCs. Conversely, VSMCs-targeted LCN2 overexpression or recombinant LCN2 treatment exacerbated CKD-VC in vivo and in vitro. Mechanistically, nuclear receptor coactivator 4 (NCOA4)/ferritin heavy chain 1 (FTH1)-mediated ferritinophagy-dependent ferroptosis was involved in LCN2-mediated CKD-VC. Under HP conditions, LCN2 interacted with NCOA4, potentially accelerating the degradation of FTH1 and inducing ferroptosis. The inhibition of LCN2 may rescue the degradation of FTH1 and thus ameliorate ferroptosis, significantly suppressing VSMCs calcification. In summary, our study revealed a novel role for LCN2 induced ferritinophagy-dependent ferroptosis in CKD-VC, and targeting LCN2 might be a promising treatment for CKD-VC.

Inflammation in a ferroptotic environment

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

Glycyrrhizin Ameliorates Cardiac Injury in Rats with Severe Acute Pancreatitis by Inhibiting Ferroptosis via the Keap1/Nrf2/HO-1 Pathway

BACKGROUND

Severe acute pancreatitis (SAP) is a potential fatal gastrointestinal disease that is usually complicated by myocardial injury and dysfunction. Due to the lack of understanding of the mechanism of SAP-associated cardiac injury (SACI), there is still no complete treatment.

AIMS

To explore the alleviative effect and anti-ferroptosis mechanism against SACI of glycyrrhizin (GL), an inhibitor of oxidative stress.

METHODS

The SAP model was established by perfusing 5% sodium taurocholate into biliopancreatic duct in rats. H&E staining and serum assays were used to assess the injury changes of pancreas and heart. Echocardiography was used to evaluate the cardiac function. Transmission electron microscopy (TEM) and oxidative stress assays were used to investigate the ferroptosis-related morphological and biochemical changes. Western blot and immunofluorescence were performed to analyzed the expression of ferroptosis-related proteins.

RESULTS

Significant myocardial impairment was found in SAP rats according to increased histopathological scores, serum creatine kinase-MB (CK-MB) and cardiac troponin-I (cTnI) levels, and a decreased fractional shortening and ejection fraction. The decreased mitochondrial cristae and significant expression changes of ferroptosis-related proteins confirmed the presence of ferroptosis in SACI. GL treatment attenuated above-mentioned cardiac tissues damage by inhibiting ferroptosis via restoring the expression of Nrf2 and HO-1 in vivo and in vitro. Treating with ML385 (a Nrf2 inhibitor) or transfecting with siRNA-Nrf2 reversed the protective effect of GL.

CONCLUSIONS

Our findings demonstrate the involvement of ferroptosis in SACI and suggest a potential role for GL in the treatment of SACI by supressing ferroptosis via Keap1/Nrf2/HO-1 pathway.

Identification of key genes as potential diagnostic biomarkers in sepsis by bioinformatics analysis

Background

Sepsis, an infection-triggered inflammatory syndrome, poses a global clinical challenge with limited therapeutic options. Our study is designed to identify potential diagnostic biomarkers of sepsis onset in critically ill patients by bioinformatics analysis.

Methods

Gene expression profiles of GSE28750 and GSE74224 were obtained from the Gene Expression Omnibus (GEO) database. These datasets were merged, normalized and de-batched. Weighted gene co-expression network analysis (WGCNA) was performed and the gene modules most associated with sepsis were identified as key modules. Functional enrichment analysis of the key module genes was then conducted. Moreover, differentially expressed gene (DEG) analysis was conducted by the "limma" R package. Protein-protein interaction (PPI) network was created using STRING and Cytoscape, and PPI hub genes were identified with the cytoHubba plugin. The PPI hub genes overlapping with the genes in key modules of WGCNA were determined to be the sepsis-related key genes. Subsequently, the key overlapping genes were validated in an external independent dataset and sepsis patients recruited in our hospital. In addition, CIBERSORT analysis evaluated immune cell infiltration and its correlation with key genes.

Results

By WGCNA, the greenyellow module showed the highest positive correlation with sepsis (0.7, p = 2e - 19). 293 DEGs were identified in the merged datasets. The PPI network was created, and the CytoHubba was used to calculate the top 20 genes based on four algorithms (Degree, EPC, MCC, and MNC). Ultimately, LTF, LCN2, ELANE, MPO and CEACAM8 were identified as key overlapping genes as they appeared in the PPI hub genes and the key module genes of WGCNA. These sepsis-related key genes were validated in an independent external dataset (GSE131761) and sepsis patients recruited in our hospital. Additionally, the immune infiltration profiles differed significantly between sepsis and non-sepsis critical illness groups. Correlations between immune cells and these five key genes were assessed, revealing that plasma cells, macrophages M0, monocytes, T cells regulatory, eosinophils and NK cells resting were simultaneously and significantly associated with more than two key genes.

Conclusion

This study suggests a critical role of LTF, LCN2, ELANE, MPO and CEACAM8 in sepsis and may provide potential diagnostic biomarkers and therapeutic targets for the treatment of sepsis.

Inflammatory liver diseases and susceptibility to sepsis

Patients with inflammatory liver diseases, particularly alcohol-associated liver disease and metabolic dysfunction-associated fatty liver disease (MAFLD), have higher incidence of infections and mortality rate due to sepsis. The current focus in the development of drugs for MAFLD is the resolution of non-alcoholic steatohepatitis and prevention of progression to cirrhosis. In patients with cirrhosis or alcoholic hepatitis, sepsis is a major cause of death. As the metabolic center and a key immune tissue, liver is the guardian, modifier, and target of sepsis. Septic patients with liver dysfunction have the highest mortality rate compared with other organ dysfunctions. In addition to maintaining metabolic homeostasis, the liver produces and secretes hepatokines and acute phase proteins (APPs) essential in tissue protection, immunomodulation, and coagulation. Inflammatory liver diseases cause profound metabolic disorder and impairment of energy metabolism, liver regeneration, and production/secretion of APPs and hepatokines. Herein, the author reviews the roles of (1) disorders in the metabolism of glucose, fatty acids, ketone bodies, and amino acids as well as the clearance of ammonia and lactate in the pathogenesis of inflammatory liver diseases and sepsis; (2) cytokines/chemokines in inflammatory liver diseases and sepsis; (3) APPs and hepatokines in the protection against tissue injury and infections; and (4) major nuclear receptors/signaling pathways underlying the metabolic disorders and tissue injuries as well as the major drug targets for inflammatory liver diseases and sepsis. Approaches that focus on the liver dysfunction and regeneration will not only treat inflammatory liver diseases but also prevent the development of severe infections and sepsis.

Lipocalin-2 expression identifies an intestinal regulatory neutrophil population during acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT), for which therapeutic options are limited. Strategies to promote intestinal tissue tolerance during aGVHD may improve patient outcomes. Using single-cell RNA sequencing, we identified a lipocalin-2 (LCN2)-expressing neutrophil population in mice with intestinal aGVHD. Transfer of LCN2-overexpressing neutrophils or treatment with recombinant LCN2 reduced aGVHD severity, whereas the lack of epithelial or hematopoietic LCN2 enhanced aGVHD severity and caused microbiome alterations. Mechanistically, LCN2 induced insulin-like growth factor 1 receptor (IGF-1R) signaling in macrophages through the LCN2 receptor SLC22A17, which increased interleukin-10 (IL-10) production and reduced major histocompatibility complex class II (MHCII) expression. Transfer of LCN2-pretreated macrophages reduced aGVHD severity but did not reduce graft-versus-leukemia effects. Furthermore, LCN2 expression correlated with IL-10 expression in intestinal biopsies in multiple cohorts of patients with aGVHD, and LCN2 induced IGF-1R signaling in human macrophages. Collectively, we identified a LCN2-expressing intestinal neutrophil population that reduced aGVHD severity by decreasing MHCII expression and increasing IL-10 production in macrophages. This work provides the foundation for administration of LCN2 as a therapeutic approach for aGVHD.

LCN2 and ELANE overexpression induces sepsis

Sepsis is a syndrome characterized by a systemic inflammatory response due to the invasion of pathogenic microorganisms. The relationship between Lipocalin-2 (LCN2), elastase, neutrophil expressed (ELANE) and sepsis remains unclear. The sepsis datasets GSE137340 and GSE154918 profiles were downloaded from gene expression omnibus generated from GPL10558. Batch normalization, differentially expressed Genes (DEGs) screening, weighted gene co-expression network analysis (WGCNA), functional enrichment analysis, Gene Set Enrichment Analysis (GSEA), immune infiltration analysis, construction and analysis of protein-protein interaction (PPI) networks, Comparative Toxicogenomics Database (CTD) analysis were performed. Gene expression heatmaps were generated. TargetScan was used to screen miRNAs of DEGs. 328 DEGs were identified. According to Gene Ontology (GO), in the Biological Process analysis, they were mainly enriched in immune response, apoptosis, inflammatory response, and immune response regulation signaling pathways. In cellular component analysis, they were mainly enriched in vesicles, cytoplasmic vesicles, and secretory granules. In Molecular Function analysis, they were mainly concentrated in hemoglobin binding, Toll-like receptor binding, immunoglobulin binding, and RAGE receptor binding. In Kyoto Encyclopedia of Genes and Genomes (KEGG), they were mainly enriched in NOD-like receptor signaling pathway, Toll-like receptor signaling pathway, TNF signaling pathway, P53 signaling pathway, and legionellosis. Seventeen modules were generated. The PPI network identified 4 core genes (MPO, ELANE, CTSG, LCN2). Gene expression heatmaps revealed that core genes (MPO, ELANE, CTSG, LCN2) were highly expressed in sepsis samples. CTD analysis found that MPO, ELANE, CTSG and LCN2 were associated with sepsis, peritonitis, meningitis, pneumonia, infection, and inflammation. LCN2 and ELANE are highly expressed in sepsis and may serve as molecular targets.

[The role of neutrophils in the mechanisms of sepsis]

The international consensus Sepsis-3 in 2016 defined sepsis as life-threatening organ dysfunction caused by a disruption of the host response to infection. One of the main mechanisms leading to the death of patients with sepsis is an imbalance of the immune response to pathogens. Activation of immune cells, in particular neutrophils, plays a key role in the mechanisms of sepsis. During sepsis, the number of immature neutrophils in the blood increases, PD-L1 neutrophils appear, which have an immunosuppressive function, and the number of Neu1 subtype of neutrophils, characterized by high expression of the NF-kB inhibitor, the chemokine CXCL8, olfactomedine, which regulates the production of cytokines, and myeloperoxidase, increases. When the inflammatory response generalizes, the phagocytic and bactericidal functions of neutrophils are disrupted. An important role in the mechanisms of sepsis is played by the formation of neutrophil extracellular traps, extracellular DNA, and the nuclear non-histone protein HMGB1, which are DAMPs and have proinflammatory activity. The development of approaches to predicting the development and course of sepsis in injuries and infectious and inflammatory diseases based on assessing the functional activity of neutrophils and their phenotype is a promising area of research, in particular approaches to regulating the functioning of neutrophils using miRNA.

Modulation of the HIF-1α-NCOA4-FTH1 Signaling Axis Regulating Ferroptosis-induced Hepatic Stellate Cell Senescence to Explore the Anti-hepatic Fibrosis Mechanism of Curcumol

INTRODUCTION

Senescence of activated hepatic stellate cells (HSC) reduces extracellular matrix expression to reverse liver fibrosis. Ferroptosis is closely related to cellular senescence, but its regulatory mechanisms need to be further investigated. The iron ions weakly bound to ferritin in the cell are called labile iron pool (LIP), and together with ferritin, they maintain cellular iron homeostasis and regulate the cell's sensitivity to ferroptosis.

METHODS

We used lipopolysaccharide (LPS) to construct a pathological model group and divided the hepatic stellate cells into a blank group, a model group, and a curcumol 12.5 mg/L group, a curcumol 25 mg/L group, and a curcumol 50 mg/L group. HIF-1α-NCOA4- FTH1 signalling axis, ferroptosis and cellular senescence were detected by various cellular molecular biology experiments.

RESULT

We found that curcumol could induce hepatic stellate cell senescence by promoting iron death in hepatic stellate cells. Curcumol induced massive deposition of iron ions in hepatic stellate cells by activating the HIF-1α-NCOA4-FTH1 signalling axis, which further led to iron overload and lipid peroxidation-induced ferroptosis. Interestingly, our knockdown of HIF-1α rescued curcumol-induced LIP and iron deposition in hepatic stellate cells, suggesting that HIF-1α is a key target of curcumol in regulating iron metabolism and ferroptosis. We were able to rescue curcumol-induced hepatic stellate cell senescence when we reduced LIP and iron ion deposition using iron chelators.

CONCLUSION

Overall, curcumol induces ferroptosis and cellular senescence by increasing HIF-1α expression and increasing NCOA4 interaction with FTH1, leading to massive deposition of LIP and iron ions, which may be the molecular biological mechanism of its anti-liver fibrosis.

Targeting epigenetic and posttranslational modifications regulating ferroptosis for the treatment of diseases

Ferroptosis, a unique modality of cell death with mechanistic and morphological differences from other cell death modes, plays a pivotal role in regulating tumorigenesis and offers a new opportunity for modulating anticancer drug resistance. Aberrant epigenetic modifications and posttranslational modifications (PTMs) promote anticancer drug resistance, cancer progression, and metastasis. Accumulating studies indicate that epigenetic modifications can transcriptionally and translationally determine cancer cell vulnerability to ferroptosis and that ferroptosis functions as a driver in nervous system diseases (NSDs), cardiovascular diseases (CVDs), liver diseases, lung diseases, and kidney diseases. In this review, we first summarize the core molecular mechanisms of ferroptosis. Then, the roles of epigenetic processes, including histone PTMs, DNA methylation, and noncoding RNA regulation and PTMs, such as phosphorylation, ubiquitination, SUMOylation, acetylation, methylation, and ADP-ribosylation, are concisely discussed. The roles of epigenetic modifications and PTMs in ferroptosis regulation in the genesis of diseases, including cancers, NSD, CVDs, liver diseases, lung diseases, and kidney diseases, as well as the application of epigenetic and PTM modulators in the therapy of these diseases, are then discussed in detail. Elucidating the mechanisms of ferroptosis regulation mediated by epigenetic modifications and PTMs in cancer and other diseases will facilitate the development of promising combination therapeutic regimens containing epigenetic or PTM-targeting agents and ferroptosis inducers that can be used to overcome chemotherapeutic resistance in cancer and could be used to prevent other diseases. In addition, these mechanisms highlight potential therapeutic approaches to overcome chemoresistance in cancer or halt the genesis of other diseases.

Lipid Metabolism Reprogramming of Immune Cells in Acne: An Update

Acne vulgaris is one of the most widespread skin conditions and the main reason for visiting a dermatologist. Inflammatory response and abnormal infiltrations of immune cells are the main pathogenesis of acne. The increased lipid is the prerequisite for the acne, and the perturbation of lipid composition and content is consistent with the severity of acne. Furthermore, the increased lipid production not only contributes to the occurrence and development of acne, but also sensitizes the function of immune cells. The lipid metabolic dysfunction aggravates the severity of local tissue and provides pro-inflammatory-cytokine cues, which indicates the crucial roles of lipid metabolism on immune cells. Recent advances have demonstrated the lipid metabolism reprogramming of various immune cells in acne lesion. The abnormal lipid accumulation, lipolysis, and fatty acid oxidation lead to the activation and differentiation of immune cells, which promotes the pro-inflammatory cytokines production. Thus, this review discusses the emerging role of lipid metabolism reprogramming of immune cells in the progress of acne and aims to constitute food for others' projects involved in acne research.

Parecoxib attenuates inflammation injury in septic H9c2 cells by regulating the MAPK signaling pathway

Parecoxib, a non-steroidal anti-inflammatory drug, has been reported to possess protective effects against sepsis. However, its detailed role and underlying mechanisms in septic cardiomyopathy remain unclear. Therefore, the goal of the present study was to clarify the function and to investigate the mechanisms of parecoxib in lipopolysaccharide (LPS)-treated H9c2 rat cardiomyocytes. TNF-α, IL-1β and IL-6 expression levels in parecoxib-treated H9c2 cells stimulated with LPS were assessed using ELISA. Parecoxib-treated H9c2 cells stimulated with LPS were tested for viability using the Cell Counting Kit-8 assay. Western blotting analysis and 5-ethynyl-2'-deoxyuridine were used to evaluate cell proliferation. Apoptosis was assessed using TUNEL and western blotting. To assess the protein expression of the MAPK signaling pathway, western blotting was performed. The data showed that parecoxib significantly and dose-dependently reduced the inflammatory responses of LPS-treated H9c2 cells. Parecoxib also significantly and dose-dependently increased the proliferation and inhibited the apoptosis of LPS-treated H9c2 cells. In addition, parecoxib significantly suppressed the activation of the MAPK (p38, JNK and ERK) signaling pathway. The current study indicated that parecoxib could be a viable therapeutic option for septic cardiomyopathy.

Targeting ferroptosis as a promising therapeutic strategy to treat cardiomyopathy

Cardiomyopathies are a clinically heterogeneous group of cardiac diseases characterized by heart muscle damage, resulting in myocardium disorders, diminished cardiac function, heart failure, and even sudden cardiac death. The molecular mechanisms underlying the damage to cardiomyocytes remain unclear. Emerging studies have demonstrated that ferroptosis, an iron-dependent non-apoptotic regulated form of cell death characterized by iron dyshomeostasis and lipid peroxidation, contributes to the development of ischemic cardiomyopathy, diabetic cardiomyopathy, doxorubicin-induced cardiomyopathy, and septic cardiomyopathy. Numerous compounds have exerted potential therapeutic effects on cardiomyopathies by inhibiting ferroptosis. In this review, we summarize the core mechanism by which ferroptosis leads to the development of these cardiomyopathies. We emphasize the emerging types of therapeutic compounds that can inhibit ferroptosis and delineate their beneficial effects in treating cardiomyopathies. This review suggests that inhibiting ferroptosis pharmacologically may be a potential therapeutic strategy for cardiomyopathy treatment.