Yap1 alleviates sepsis associated encephalopathy by inhibiting hippocampus ferroptosis via maintaining mitochondrial dynamic homeostasis.

Sepsis-associated encephalopathy (SAE) is a serious neurological complication accompanied by acute and long-term cognitive dysfunction. Ferroptosis is a newly discovered type of cell death that is produced by iron-dependent lipid peroxidation. As a key transcriptional coactivator in the Hippo signalling pathway, Yes-associated protein 1 (YAP1) could target ferroptosis-related genes. This study was aimed to determine whether Yap1 protects against SAE and inhibits ferroptosis via maintaining mitochondrial dynamic homeostasis. Caecal ligation puncture (CLP) was used to establish the SAE model, and LPS was applied in hippocampal cells to mimic the inflammatory model in vitro. The results showed that Yap1 conditional knockout in hippocampal caused lower survival in SAE mice and cognitive dysfunction, as proved by Morri's water maze (MWM) task, tail suspension test (TST), open field test (OFT) and elevated plus maze test (EPMT). After Yap1 knockout, the production of ROS, MDA and Fe2+ and proinflammatory cytokines in the hippocampus were increased, indicating that Yap1 deficiency exacerbates CLP-induced brain injury and hippocampus ferroptosis. Meanwhile, GPX4, SLC7A11, ferritin (FTH1) and GSH levels were decreased in the Yap1 knockout group. In vitro, Yap1 overexpression mitigated LPS-induced hippocampal cell ferroptosis and improved mitochondrial function by inhibiting mitochondrial fission, as evidenced by lower mitochondrial ROS, cell viability, Fe2+ and the expression of Fis1 and Drp1. Further, the present study suggested that Yap1 could inhibit ferritinophagy-mediated ferroptosis in the hippocampus via inhibiting mitochondrial fission, thus reducing cognitive dysfunction in SAE mice.

Yang X ，Duan H ，Li S ，Zhang J ，Dong L ，Ding J ，Li X ... -  《-》

Nrf2 mitigates sepsis-associated encephalopathy-induced hippocampus ferroptosis via modulating mitochondrial dynamic homeostasis.

Sepsis-associated encephalopathy (SAE) is a serious neurological complication accompanied with acute and long-term cognitive dysfunction. Ferroptosis is a newly discovered type of cell death that is produced by iron-dependent lipid peroxidation. Emerging evidence suggests that ferroptosis is involved in SAE. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a mitochondria related gene involved in ferroptosis. However, the role of Nrf2 in SAE and the mechanisms remains elusive. In this study, we found that Nrf2 knockout aggravated cognitive and emotional dysfunction and promoted caecal ligation and puncture (CLP)-induced brain injury and hippocampus ferroptosis as indicated by the increase of ROS, Fe2+ and the levels of proinflammatory cytokines. Meanwhile, the levels of glutathione peroxidase 4 (GPX4), SLC7A11 and glutathionewere downregulatedin Nrf2 knockout group. In vitro experiments showed that mitochondrial ROS, Fe2+ and the expression of Fis1 and Drp1 decreased, and the level of Mfn1 and Opa-1 increased after Nrf2 overexpression. The silence of Nrf2 increased the expression of ROS, MDA and Fe2+, while decreased glutathione, mitochondrial membrane potential (MMP) and cell viability in vitro, indicating Nrf2 improved LPS-induced mitochondrial dysfunction and mitigated hippocampal cells ferroptosis. These results suggest that Nrf2 could inhibit ferroptosis and neuroinflammation in hippocampus and reduce cognitive dysfunction in SAE mice, making it a potential therapeutic target in the treatment of SAE. The protective effects of Nrf2 on the brain may be mediated by maintaining mitochondrial dynamic homeostasis.

Duan H ，Yang X ，Cai S ，Zhang L ，Qiu Z ，Wang J ，Wang S ，Li Z ，Li X ... -  《-》

YAP1 alleviates sepsis-induced acute lung injury via inhibiting ferritinophagy-mediated ferroptosis.

Ferroptosis is a phospholipid peroxidation-mediated and iron-dependent cell death form, involved in sepsis-induced organ injury and other lung diseases. Yes-associated protein 1 (YAP1), a key regulator of the Hippo signaling pathway, could target multiple ferroptosis regulators. Herein, this study aimed to explore the involvement of ferroptosis in the etiopathogenesis of sepsis-induced acute lung injury (ALI) and demonstrate that YAP1 could disrupt ferritinophagy and moderate sepsis-induced ALI. Cecal ligation and puncture (CLP) models were constructed in wild-type (WT) and pulmonary epithelium-conditional knockout (YAP1f/f) mice to induce ALI, while MLE-12 cells with or without YAP1 overexpression were stimulated by lipopolysaccharide (LPS) in vitro. In-vivo modes showed that YAP1 knockout aggravated CLP-induced ALI and also accelerated pulmonary ferroptosis, as presented by the downregulated expression of GPX4, FTH1, and SLC7A11, along with the upregulated expression of SFXN1 and NCOA4. Transcriptome research identified these key genes and ferroptosis pathways involved in sepsis-induced ALI. In-vitro modes consistently verified that YAP1 deficiency boosted the ferrous iron accumulation and mitochondrial dysfunction in response to LPS. Furthermore, the co-IP assay revealed that YAP1 overexpression could prevent the degradation of ferritin to a mass of Fe2+ (ferritinophagy) via disrupting the NCOA4-FTH1 interaction, which blocked the transport of cytoplasmic Fe2+ into the mitochondria via the mitochondrial membrane protein (SFXN1), further reducing the generation of mitochondrial ROS. Therefore, these findings revealed that YAP1 could inhibit ferroptosis in a ferritinophagy-mediated manner, thus alleviating sepsis-induced ALI, which may provide a new approach to the therapeutic orientation for sepsis-induced ALI.

Zhang J ，Zheng Y ，Wang Y ，Wang J ，Sang A ，Song X ，Li X ... -  《Frontiers in Immunology》

Lipid peroxidation-induced ferroptosis as a therapeutic target for mitigating neuronal injury and inflammation in sepsis-associated encephalopathy: insights into the hippocampal PEBP-1/15-LOX/GPX4 pathway.

Sepsis-associated encephalopathy (SAE) refers to the widespread impairment of brain function caused by noncentral nervous system infection mediated by sepsis. Lipid peroxidation-induced ferroptosis contributes to the occurrence and course of SAE. This study aimed to investigate the relationship between neuronal injury and lipid peroxidation-induced ferroptosis in SAE. Baseline data were collected from pediatric patients upon admission, and the expression levels of various markers related to lipid peroxidation and ferroptosis were monitored in the serum and peripheral blood mononuclear cells (PBMCs) of patients with SAE as well as SAE model mice. The hippocampal phosphatidylethanolamine-binding protein (PEBP)-1/15-lysine oxidase (LOX)/ glutathione peroxidase 4 (GPX4) pathway was assessed for its role on the inhibitory effect of ferroptosis in SAE treatment. The results showed elevated levels of S100 calcium-binding protein beta (S-100β), glial fibrillary acidic protein, and malondialdehyde in the serum of SAE patients, while superoxide dismutase levels were reduced. Furthermore, analysis of PBMCs revealed increased transcription levels of PEBP1, LOX, and long-chain fatty acyl-CoA synthetase family member 4 (ACSL4) in SAE patients, while the transcription levels of GPX4 and cystine/glutamate transporter xCT (SLC7A11) were decreased. In comparison to the control group, the SAE mice exhibited increased expression of S-100β and neuron-specific enolase (NSE) in the hippocampus, whereas the expression of S-100β and NSE were reduced in deferoxamine (DFO) mice. Additionally, iron accumulation was observed in the hippocampus of SAE mice, while the iron ion levels were reduced in the DFO mice. Inhibition of ferroptosis alleviated the mitochondrial damage (as assessed by transmission electron microscopy, hippocampal mitochondrial ATP detection, and the JC-1 polymer-to-monomer ratio in the hippocampus) and the oxidative stress response induced by SAE as well as attenuated neuroinflammatory reactions. Further investigations revealed that the mechanism underlying the inhibitory effect of ferroptosis in SAE treatment is associated with the hippocampal PEBP-1/15-LOX/GPX4 pathway. These results offer potential therapeutic targets for the management of neuronal injury in SAE and valuable insights into the potential mechanisms of ferroptosis in neurological disorders.

Wang H ，Xu L ，Tang X ，Jiang Z ，Feng X ... -  《Lipids in Health and Disease》

Irisin protects against sepsis-associated encephalopathy by suppressing ferroptosis via activation of the Nrf2/GPX4 signal axis.

Sepsis-associated encephalopathy (SAE) is a common complication of severe sepsis. Irisin is a novel exercise-induced myokine involved in the regulation of adipose browning and thermogenesis. This study is designed to verify the existence of ferroptosis in the pathogenesis of SAE and demonstrate that irisin attenuated cognitive dysfunction in SAE mice via inhibition of hippocampus ferroptosis. A mouse SAE model was induced by cecal ligation and puncture (CLP) and in vitro model was established by LPS-stimulated hippocampus cells. Irisin were pre-treated in the models. We found that SAE triggered hippocampus ferroptosis, as evidenced by increasing ROS, iron content and MDA and reducing GSH level as well as altered ferroptosis-related protein (GPX4, ACSL4 and SLC7A11) expression, whereas irisin attenuated CLP-induced learning and memory dysfunction, neurologic severity score and hippocampus ferroptosis and microglial activation in SAE mice. However, the protective effect of irisin was eliminated by ferroptosis inducer Erastin. Consistently, irisin reduced ferroptosis and improved mitochondrial dysfunction in LPS-induced HT-22 cells, as evidenced by decreased lipid ROS and increased mitochondrial membrane potential. Furthermore, proteomics identified the differentially expressed proteins linked to ferroptosis in SAE. We also observed that irisin-mediated anti-ferroptosis was abolished by siRNA-Nrf2 or in Nrf2-/- mice. Transwell assay revealed that irisin could prevent the recruitment and chemotaxis of microglial cells induced by ferroptotic hippocampal cells. In conclusion, irisin could ameliorate inflammatory microenvironment in SAE by suppressing hippocampus ferroptosis via the Nrf2/GPX4 signaling pathway.

Wang J ，Zhu Q ，Wang Y ，Peng J ，Shao L ，Li X ... -  《-》