Suppressing the Substance P-NK1R Signalling Protects Mice against Sepsis-Associated Acute Inflammatory Injury and Ferroptosis in the Liver and Lungs

Investigation into the influence of mild hypothermia on regulating ferroptosis through the P53-SLC7A11/GPX4 signaling pathway in sepsis-induced acute lung injury

BACKGROUND

Sepsis-induced acute lung injury (S-ALI) significantly contributes to unfavorable clinical outcomes. Emerging evidence suggests a novel role for ferroptosis in the pathophysiology of ALI, though the precise mechanisms remain unclear. Mild hypothermia (32-34 °C) has been shown to inhibit inflammatory responses, reduce oxidative stress, and regulate metabolic processes. P53 has been reported to downregulate the transcriptional activity of solute carrier family 7 member 11 (SLC7A11), thereby limiting cystine uptake. This reduction in cystine availability compromises the activity of Glutathione peroxidase 4 (GPX4), a cystine-dependent enzyme, ultimately increasing cellular susceptibility to ferroptosis. However, it remains unclear whether mild hypothermia exerts protective effects through the P53-SLC7A11/GPX4 signaling pathway. This study investigates the influence of mild hypothermia on ferroptosis mediated by the P53-SLC7A11/GPX4 pathway in S-ALI.

METHODS

This study utilized both in vivo and in vitro models. In the vivo model, 64 Sprague-Dawley rats were employed, with 40 analyzed for survival outcomes. Sepsis was induced using the cecum ligation and puncture (CLP) method, after which rats were subjected to either normothermic (36-38 °C) or mild hypothermic (32-34 °C) conditions for a duration of 10 h. Twelve hours post-surgery, blood samples, bronchoalveolar lavage fluid, and lung tissue samples were harvested for histological analysis, measurement of inflammatory markers, wet/dry ratios, blood gas analysis, assessment of oxidative stress and ferroptosis, Western blotting, and RT-qPCR analysis. In the in vitro model, RLE-6TN cells were exposed to lipopolysaccharide (LPS) for 24 h under normothermic and mild hypothermic conditions. These cells were then evaluated for cell viability, inflammatory markers, oxidative stress levels, ferroptosis markers, as well as Western blot and RT-qPCR analyses.

RESULTS

CLP-induced sepsis led to elevated levels of inflammatory markers, increased lung injury scores, and heightened oxidative stress markers. These detrimental effects were significantly ameliorated by mild hypothermia. Furthermore, mild hypothermia reversed the modified expression of P53, SLC7A11, and GPX4 signaling molecules. Notably, mild hypothermia also improved the 5-day survival rate of CLP rats.

CONCLUSION

Mild hypothermia attenuates S-ALI and modulates ferroptosis through the P53-SLC7A11/GPX4 signaling pathway.

FBLN1 regulates ferroptosis in acute respiratory distress syndrome by reducing free ferrous iron by inhibiting the TGF-β/Smad pathway

BACKGROUND

Acute respiratory distress syndrome (ARDS) / acute lung injury (ALI) is a serious medical disease characterized by pulmonary dysfunction and inflammation. This study aims to determine the main molecular modules linked to ARDS and investigate the role of Fibulin-1 (FBLN1) in regulating ferroptosis in ARDS.

METHODS

Weighted Gene Co-expression Network Analysis (WGCNA) was employed on the GSE263867 dataset to find key modules associated with ALI. Differentially expressed genes (DEGs) and protein-protein interaction (PPI) networks were analyzed. MLE-12 cells were treated with lipopolysaccharide (LPS) to induce ferroptosis. In vitro studies were conducted to investigate the effects of FBLN1 and Transforming Growth Factor Beta 1 (TGF-β) overexpression on cell viability, oxidative stress markers, and ferroptosis-related proteins.

RESULTS

WGCNA identified the turquoise module as significantly negatively correlated with ARDS. Five key overlapping genes (GRIA1, OGN, COL14A1, FBLN1, and COL6A3) were significantly downregulated in ARDS samples. LPS treatment induced ferroptosis in MLE-12 cells, indicated by increased malondialdehyde (MDA), lipid reactive oxygen species (ROS), and ferrous iron (Fe2⁺) levels, and decreased cell viability and glutathione (GSH) levels. FBLN1 overexpression partially reversed these effects. Additionally, FBLN1 inhibited the TGF-β/Smad signaling pathway, as shown by decreased TGF-β and p-Smad protein levels. TGF-β overexpression exacerbated LPS-induced oxidative stress and ferroptosis, reducing cell viability and GSH levels. FBLN1 overexpression counteracted this effect, suggesting antagonistic roles for FBLN1 and TGF-β in regulating ferroptosis.

CONCLUSION

This study highlights FBLN1 as a critical regulator of ferroptosis in ARDS. Targeting the TGF-β/Smad pathway to modulate FBLN1 expression offers a potential therapeutic strategy to alleviate oxidative stress and mitigate pulmonary injury in inflammatory lung diseases.

Substance P Promotes Leukocyte Infiltration in the Liver and Lungs of Mice with Sepsis: A Key Role for Adhesion Molecules on Vascular Endothelial Cells

Substance P (SP), encoded by the Tac1 gene, has been shown to promote leukocyte infiltration and organ impairment in mice with sepsis. Neurokinin-1 receptor (NK1R) is the major receptor that mediates the detrimental impact of SP on sepsis. This investigation studied whether SP affects the expression of adhesion molecules, including intercellular cell adhesion molecule-1 (ICAM1) and vascular cell adhesion molecule-1 (VCAM1) on vascular endothelial cells in the liver and lungs, contributing to leukocyte infiltration in these tissues of mice with sepsis. Sepsis was induced by caecal ligation and puncture (CLP) surgery in mice. The actions of SP were inhibited by deleting the Tac1 gene, blocking NK1R, or combining these two methods. The activity of myeloperoxidase and the concentrations of ICAM1 and VCAM1 in the liver and lungs, as well as the expression of ICAM1 and VCAM1 on vascular endothelial cells in these tissues, were measured. The activity of myeloperoxidase and the concentration of ICAM1 and VCAM1 in the liver and lungs, as well as the expression of ICAM1 and VCAM1 on vascular endothelial cells in these tissues, increased in mice with CLP surgery-induced sepsis. Suppressing the biosynthesis of SP and its interactions with NK1R attenuated CLP surgery-induced alterations in the liver and lungs of mice. Our findings indicate that SP upregulates the expression of ICAM1 and VCAM1 on vascular endothelial cells in the liver and lungs, thereby increasing leukocyte infiltration in these tissues of mice with CLP surgery-induced sepsis by activating NK1R.

Ferroptosis inhibitors: past, present and future

Ferroptosis is a non-apoptotic mode of programmed cell death characterized by iron dependence and lipid peroxidation. Since the ferroptosis was proposed, researchers have revealed the mechanisms of its formation and continue to explore effective inhibitors of ferroptosis in disease. Recent studies have shown a correlation between ferroptosis and the pathological mechanisms of neurodegenerative diseases, as well as diseases involving tissue or organ damage. Acting on ferroptosis-related targets may provide new strategies for the treatment of ferroptosis-mediated diseases. This article specifically describes the metabolic pathways of ferroptosis and summarizes the reported mechanisms of action of natural and synthetic small molecule inhibitors of ferroptosis and their efficacy in disease. The paper also describes ferroptosis treatments such as gene therapy, cell therapy, and nanotechnology, and summarises the challenges encountered in the clinical translation of ferroptosis inhibitors. Finally, the relationship between ferroptosis and other modes of cell death is discussed, hopefully paving the way for future drug design and discovery.