The role of ferroptosis in chronic intermittent hypoxia-induced lung injury

Hypoxia impairs male reproductive functions via inducing rat Leydig cell ferroptosis under simulated environment at altitude of 5000 m

AIMS

Many studies demonstrated reproductive damage in men residing in plains who are exposed to hypoxia at high altitudes. However, little is known about mechanisms between male reproductive impairment and hypobaric hypoxia. Hypoxia is one of the reasons for the imbalance of cellular redox system. Ferroptosis, involved in many pathophysiological progresses, is an oxidative damage-related, iron-dependent regulated cell death, which needs exogenous inducer. In our study, we explored the mechanism between hypoxia and male reproductive dysfunction.

MATERIALS AND METHODS

Here, we established animal model simulating hypobaric hypoxia at an altitude of 5000 m and used ELISA, WB, qPCR, flow cytometry and etc. to obtain different results.

KEY FINDINGS

The results demonstrated decrease of plasma testosterone (T) and free testosterone (FT) levels under hypoxia, meanwhile there's decline in sperm counts and sperm motility, coupled with increase in sperm malformation rates. Flow cytometry confirmed significant reduction in Leydig cell numbers. Prussian blue staining showed iron depositions in interstitial testis. Features of ferroptosis such as increased MDA (malondialdehyde) levels, reduced solute carrier family 7 member 11 (SLC7A11, xCT) and glutathione peroxidase 4 (GPX4) expression were observed in testis after hypoxic exposure. Further in vitro experiments, we observed that hypoxia suppressed xCT-GPX4 pathway and enhanced cellular ROS accumulation to lead Leydig cell proliferation activity decline.

SIGNIFICANCE

Our findings firstly indicated that hypoxia leads to male reproductive dysfunction via inducing Leydig cell ferroptosis. This discovery may offer a potential intervention target for addressing male reproductive injuries under hypoxic conditions.

Overexpression of transcription factor TBX5 inhibits the activation of YAP1-TEAD1 pathway to promote ferroptosis in lung cancer cells

BACKGROUND

Non-small cell lung cancer (NSCLC) accounts for more than 80 % of lung cancer (LC) cases, making it the primary cause of cancer-related mortality worldwide. T-box transcription factor 5 (TBX5) is an important regulator of embryonic and organ development and plays a key role in cancer development. Here, our objective was to investigate the involvement of TBX5 in ferroptosis within LC cells and the underlying mechanisms.

METHODS

First, TBX5 expression was examined in human LC cells. Next, overexpression of TBX5 and Yes1-associated transcriptional regulator (YAP1) and knockdown of TEA domain 1 (TEAD1) were performed in A549 and NCI-H1703 cells. The proliferation ability of A549 and NCI-H1703 cells, GSH, MDA, ROS, and Fe2+ levels were measured. Co-immunoprecipitation (Co-IP) was performed to verify whether TBX5 protein could bind YAP1. Then TBX5, YAP1, TEAD1, GPX4, p53, FTH1, SLC7A11 and PTGS2 protein levels were assessed. Finally, we verified the effect of TBX5 on ferroptosis in LC cells in vivo.

RESULTS

TBX5 expression was down-regulated in LC cells, especially in A549 and NCI-H1703 cells. Overexpression of TBX5 significantly decreased proliferation ability of A549 and NCI-H1703 cells, downregulated GPX4 and GSH levels, and upregulated MDA, ROS, and Fe2+ levels. Co-IP verified that TBX5 protein could bind YAP1. Moreover, oe-YAP1 promoted proliferation ability of A549 and NCI-H1703 cells transfected with Lv-TBX5, upregulated GPX4 and GSH levels and downregulated MDA, ROS, and Fe2+ levels. Additionally, oe-YAP1 promoted FTH1 and SLC7A11 levels and inhibited p53 and PTGS2 levels in A549 and NCI-H1703 cells transfected with Lv-TBX5. However, transfection with si-TEAD1 further reversed these effects. In vivo experiments further validated that TBX5 promoted ferroptosis in LC cells.

CONCLUSIONS

TBX5 inhibited the activation of YAP1-TEAD1 pathway to promote ferroptosis in LC cells.

Emerging roles of ferroptosis in pulmonary fibrosis: current perspectives, opportunities and challenges

Pulmonary fibrosis (PF) is a chronic interstitial lung disorder characterized by abnormal myofibroblast activation, accumulation of extracellular matrix (ECM), and thickening of fibrotic alveolar walls, resulting in deteriorated lung function. PF is initiated by dysregulated wound healing processes triggered by factors such as excessive inflammation, oxidative stress, and coronavirus disease (COVID-19). Despite advancements in understanding the disease's pathogenesis, effective preventive and therapeutic interventions are currently lacking. Ferroptosis, an iron-dependent regulated cell death (RCD) mechanism involving lipid peroxidation and glutathione (GSH) depletion, exhibits unique features distinct from other RCD forms (e.g., apoptosis, necrosis, and pyroptosis). Imbalance between reactive oxygen species (ROS) production and detoxification leads to ferroptosis, causing cellular dysfunction through lipid peroxidation, protein modifications, and DNA damage. Emerging evidence points to the crucial role of ferroptosis in PF progression, driving macrophage polarization, fibroblast proliferation, and ECM deposition, ultimately contributing to alveolar cell death and lung tissue scarring. This review provides a comprehensive overview of the latest findings on the involvement and signaling mechanisms of ferroptosis in PF pathogenesis, emphasizing potential novel anti-fibrotic therapeutic approaches targeting ferroptosis for PF management.

Immune Dysregulation in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a disease whose incidence increase with age and is characterised by chronic inflammation and significant immune dysregulation. Inhalation of toxic substances cause oxidative stress in the lung tissue as well as airway inflammation, under the recruitment of chemokines, immune cells gathered and are activated to play a defensive role. However, persistent inflammation damages the immune system and leads to immune dysregulation, which is mainly manifested in the reduction of the body's immune response to antigens, and immune cells function are impaired, further destroy the respiratory defensive system, leading to recurrent lower respiratory infections and progressive exacerbation of the disease, thus immune dysregulation play an important role in the pathogenesis of COPD. This review summarizes the changes of innate and adaptive immune-related cells during the pathogenesis of COPD, aiming to control COPD airway inflammation and improve lung tissue remodelling by regulating immune dysregulation, for further reducing the risk of COPD progression and opening new avenues of therapeutic intervention in COPD.

Ferrostatin-1 Reversed Chronic Intermittent Hypoxia-Induced Ferroptosis in Aortic Endothelial Cells via Reprogramming Mitochondrial Function

Purpose

Chronic intermittent hypoxia (CIH) related arterial endothelium injury is a common cause of cardiovascular system injury. However, the mechanism still needs to be clarified. In this study, we aimed to clarify the role and mechanism of ferrostatin-1 (Fer-1) in CIH-related rat arterial endothelial cells (ROAEC) ferroptosis.

Methods

ROAEC was divided into control group, CIH group, and CIH+ Fer-1 group. Cell viability was detected by cell counting kit 8 kits (CCK8). The apoptotic rate, reactive oxygen species (ROS) levels, Fe2+ levels, and lipid ROS levels were detected by flow cytometry. Malondialdehyde (MDA) levels and nicotinamide adenine dinucleotide (NAD+)/NADH ratio were detected via Elisa kits. The mRNA and protein levels of cystine/glutamate antiporter solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) were detected by qRT-PCR and Western blot. Mitochondrial structure and function were observed by transmission electron microscope (TEM) and mitochondrial membrane potential (MMP). Central carbon metabolism was measured to compare metabolites among each group.

Results

After the CIH exposure, ROAEC cell viability decreased; The levels of cell apoptosis, ROS, Fe2+, MDA, and lip ROS increased; The levels of NAD+/NADP ratio decreased; The mRNA and protein levels of GPX4 and SLC7A11 decreased (all p<0.05). Co-cultured with Fer-1 reversed the levels of apoptosis rate, cell viability, ROS, Fe2+, MAD, lipid ROS, NAD+/NADH ratio and the mRNA and protein expression of GPX4 and SLC7A11 (all p<0.05). The TEM results showed that damaged mitochondrial membrane and the matrix spillover in the CIH group. The results of the JC-1 assay showed decreased MMP in the CIH group. Fer-1 treatment ameliorated the mitochondrial injury. The results of central carbon metabolism found that CIH altered the metabolites in the TCA cycle, which were reversed by Fer-1 treatment.

Conclusion

CIH-induced ferroptosis in ROAEC, which were reversed by Fer-1 via reprogramming mitochondrial function.

4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) alleviates lung injury by inhibiting SIRT6-HIF-1α signaling pathway activation through the upregulation of miR-212-5p expression

OBJECTIVE

Obstructive sleep apnea is closely related to oxidative stress. 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol) can scavenge reactive oxygen species (ROS) and ameliorate oxidative damage in the body. The mechanism by which Tempol alleviates chronic intermittent hypoxia-induced lung injury has rarely been reported. This study aimed to confirm the molecular mechanism by which Tempol alleviates lung injury.

METHODS

The levels of miR-212-5p and Sirtuin 6 (SIRT6) in injured lungs were analyzed using bioinformatics. In vitro, intermittent hypoxia (IH) treatment induced hypoxia in BEAS-2B cells and we established a model of chronic intermittent hypoxia (CIH) in mouse using a programmed hypoxia chamber. We used HE staining to observe the morphology of lung tissue, and the changes in lung fibers were observed by Masson staining. The levels of inflammatory factors in mouse serum were detected by ELISA, and the levels of the oxidative stress indicators GSH, MDA, SOD and ROS were detected using commercially available kits. Moreover, a real-time qPCR assay was used to detect miR-212-5p expression, and Western blotting was used to detect the levels of SIRT6, HIF-1α and apoptosis-related proteins. CCK-8 was used to detect cell proliferation. Subsequently, we used flow cytometry to detect cell apoptosis. Dual-luciferase gene reporters determine the on-target binding relationship of miR-212-5p and SIRT6.

RESULTS

SIRT6 was highly expressed in CIH-induced lung injury, as shown by bioinformatics analysis; however, miR-212-5p expression was decreased. Tempol promoted miR-212-5p expression, and the levels of SIRT6 and HIF-1α were inhibited. In BEAS-2B cells, Tempol also increased proliferation, inhibited apoptosis and inhibited oxidative stress in BEAS-2B cells under IH conditions. In BEAS-2B cells, these effects of Tempol were reversed after transfection with an miR-212-5p inhibitor. miR-212-5p targeted and negatively regulated the level of SIRT6 and overexpression of SIRT6 effectively reversed the enhanced influence of the miR-212-5p mimic on Tempol's antioxidant activity. Tempol effectively ameliorated lung injury in CIH mice and inhibited collagen deposition and inflammatory cell infiltration. Likewise, the therapeutic effect of Tempol could be effectively reversed by interference with the miR-212-5p inhibitor.

CONCLUSION

Inhibition of the SIRT6-HIF-1α signaling pathway could promote the effect of Tempol by upregulating the level of miR-212-5p, thereby alleviating the occurrence of lung injury and providing a new underlying target for the treatment of lung injury.

Ferroptosis-related genes are considered as potential targets for CPAP treatment of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common syndrome characterized by upper airway dysfunction during sleep. Continuous positive airway pressure (CPAP) is the most frequently utilized non-surgical treatment for OSA. Ferroptosis play a crucial role in the physiological diseases caused by chronic intermittent hypoxia, but its involvement in the development of OSA and the exact mechanisms have incompletely elucidated. GSE75097 microarray dataset was used to identify differentially expressed genes between OSA patients and CPAP-treated OSA patients. Subsequently, Gene Ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, STRING database, and FerrDb database were conducted to analyze the biological functions of differentially expressed genes and screen ferroptosis-related genes. Finally, GSE135917 dataset employed for validation. There were 1,540 differentially expressed genes between OSA patients and CPAP-treated OSA patients. These differentially expressed genes were significantly enriched in the regulation of interleukin-1-mediated signaling pathway and ferroptosis-related signaling pathway. Subsequently, 13 ferroptosis-related genes (DRD5, TSC22D3, TFAP2A, STMN1, DDIT3, MYCN, ELAVL1, JUN, DUSP1, MIB1, PSAT1, LCE2C, and MIR27A) were identified from the interaction between differentially expressed genes and FerrDb database, which are regarded as the potential targets of CPAP-treated OSA. These ferroptosis-related genes were mainly involved in cell proliferation and apoptosis and MAPK signaling pathway. Furthermore, DRD5 and TFAP2A were downregulated in OSA patients, which showed good diagnostic properties for OSA, but these abnormal signatures are not reversed with short-term effective CPAP therapy. In summary, the identification of 13 ferroptosis-related genes as potential targets for the CPAP treatment of OSA provides valuable insights into the development of novel, reliable, and accurate therapeutic options.

Identification of a novel intermittent hypoxia-related prognostic lncRNA signature and the ceRNA of lncRNA GSEC/miR-873-3p/EGLN3 regulatory axis in lung adenocarcinoma

Background

Lung adenocarcinoma (LUAD) is still the most prevalent type of respiratory cancer. Intermittent hypoxia can increase the mortality and morbidity associated with lung cancer. Long non-coding RNAs (lncRNAs) are crucial in lung adenocarcinoma. However, the effects of intermittent hypoxia-related long non-coding RNAs (IHRLs) on lung adenocarcinoma are still unknown.

Method

In the current research, eight IHRLs were selected to create a prognostic model. The risk score of the prognostic model was evaluated using multivariate and univariate analyses, and its accuracy and reliability were validated using a nomogram and ROC. Additionally, we investigated the relationships between IHRLs and the immune microenvironment.

Result

Our analysis identified GSEC, AC099850.3, and AL391001.1 as risk lncRNAs, while AC010615.2, AC010654.1, AL513550.1, LINC00996, and LINC01150 were categorized as protective lncRNAs. We observed variances in the expression of seven immune cells and 15 immune-correlated pathways between the two risk groups. Furthermore, our results confirmed the ceRNA network associated with the intermittent hypoxia-related lncRNA GSEC/miR-873-3p/EGLN3 regulatory pathway. GSEC showed pronounced expression in lung adenocarcinoma tissues and specific cell lines, and its inhibition resulted in reduced proliferation and migration in A549 and PC9 cells. Intriguingly, GSEC manifested oncogenic properties by sponging miR-873-3p and demonstrated a tendency to modulate EGLN3 expression favorably.

Conclusion

GSEC acts as an oncogenic lncRNA by interacting with miR-873-3p, modulating EGLN3 expression. This observation underscores the potential of GSEC as a diagnostic and therapeutic target for LUAD.

Ferroptosis Regulated by Hypoxia in Cells

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