System X(c) (-)/GSH/GPX4 axis: An important antioxidant system for the ferroptosis in drug-resistant solid tumor therapy.

The activation of ferroptosis is a new effective way to treat drug-resistant solid tumors. Ferroptosis is an iron-mediated form of cell death caused by the accumulation of lipid peroxides. The intracellular imbalance between oxidant and antioxidant due to the abnormal expression of multiple redox active enzymes will promote the produce of reactive oxygen species (ROS). So far, a few pathways and regulators have been discovered to regulate ferroptosis. In particular, the cystine/glutamate antiporter (System Xc -), glutathione peroxidase 4 (GPX4) and glutathione (GSH) (System Xc -/GSH/GPX4 axis) plays a key role in preventing lipid peroxidation-mediated ferroptosis, because of which could be inhibited by blocking System Xc -/GSH/GPX4 axis. This review aims to present the current understanding of the mechanism of ferroptosis based on the System Xc -/GSH/GPX4 axis in the treatment of drug-resistant solid tumors.

Li FJ ，Long HZ ，Zhou ZW ，Luo HY ，Xu SG ，Gao LC ... -  《Frontiers in Pharmacology》

Electroacupuncture Inhibits Neural Ferroptosis in Rat Model of Traumatic Brain Injury via Activating System Xc(-)/GSH/GPX4 Axis.

Ferroptosis is an iron-dependent regulating programmed cell death discovered recently that has been receiving much attention in traumatic brain injury (TBI). xCT, a major functional subunit of Cystine/glutamic acid reverse transporter (System Xc-), promotes cystine intake and glutathione biosynthesis, thereby protecting against oxidative stress and ferroptosis. The intention of this research was to verify the hypothesis that electroacupuncture (EA) exerted an anti-ferroptosis effect via an increase in the expression of xCT and activation of the System Xc-/GSH/GPX4 axis in cortical neurons of TBI rats. After the TBI rat model was prepared, animals received EA treatment at GV20, GV26, ST36 and PC6, for 15 min. The xCT inhibitor Sulfasalazine (SSZ) was administered 2h prior to model being prepared. The degree of neurological impairment was evaluated by means of TUNEL staining and the modified neurological severity score (mNSS). Specific indicators of ferroptosis (Ultrastructure of mitochondria, Iron and ROS) were detected by transmission electron microscopy (TEM), Prussian blue staining (Perls stain) and flow cytometry (FCM), respectively. GSH synthesis and metabolism-related factors in the content of the cerebral cortex were detected by an assay kit. Real-time quantitative PCR (RT-QPCR), Western blot (WB), and immunofluorescence (IF) were used for detecting the expression of System Xc-/GSH/GPX4 axisrelated proteins in injured cerebral cortex tissues. EA successfully relieved nerve damage within 7 days after TBI, significantly inhibited neuronal ferroptosis, upregulated the expression of xCT and System Xc-/GSH/GPX4 axis forward protein and promoted glutathione (GSH) synthesis and metabolism in the injured area of the cerebral cortex. However, aggravation of nerve damage and increased ferroptosis effect were found in TBI rats injected with xCT inhibitors. EA inhibits neuronal ferroptosis by up-regulated xCT expression and by activating System Xc-/GSH/GPX4 axis after TBI, confirming the relevant theories regarding the EA effect in treating TBI and providing theoretical support for clinical practice.

Li N ，Wang R ，Ai X ，Guo J ，Bai Y ，Guo X ，Zhang R ，Du X ，Chen J ，Li H ... -  《-》

Lipid Peroxidation and Iron Metabolism: Two Corner Stones in the Homeostasis Control of Ferroptosis.

Rochette L ，Dogon G ，Rigal E ，Zeller M ，Cottin Y ，Vergely C ... -  《INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES》

Berberine-mediated Ferroptosis through System Xc(-)/GSH/GPX4 Axis Inhibits Metastasis of Nasopharyngeal Carcinoma.

Wu Y ，Jia Q ，Tang Q ，Deng H ，He Y ，Tang F ... -  《Journal of Cancer》

Directly targeting glutathione peroxidase 4 may be more effective than disrupting glutathione on ferroptosis-based cancer therapy.

Cancer is one of the major threats to human health and current cancer therapies have been unsuccessful in eradicating it. Ferroptosis is characterized by iron-dependence and lipid hydroperoxides accumulation, and its primary mechanism involves the suppression of system Xc--GSH (glutathione)-GPX4 (glutathione peroxidase 4) axis. Co-incidentally, cancer cells are also metabolically characterized by iron addiction and ROS tolerance, which makes them vulnerable to ferroptosis. This may provide a new tactic for cancer therapy. The general features and mechanisms of ferroptosis, and the basis that makes cancer cells vulnerable to ferroptosis are described. Further, we emphatically discussed that disrupting GSH may not be ideal for triggering ferroptosis of cancer cells in vivo, but directly inhibiting GPX4 and its compensatory members could be more effective. Finally, the various approaches to directly inhibit GPX4 without disturbing GSH were described. Targeting system Xc- or GSH may not effectively trigger cancer cells' ferroptosis in vivo the existence of other compensatory pathways. However, directly targeting GPX4 and its compensatory members without disrupting GSH may be more effective to induce ferroptosis in cancer cells in vivo, as GPX4 is essential in preventing ferroptosis. Cancer is a severe threat to human health. Ferroptosis-based cancer therapy strategies are promising, but how to effectively induce ferroptosis in cancer cells in vivo is still a question without clear answers. Thus, the viewpoints raised in this review may provide some references and different perspectives for researchers working on ferroptosis-based cancer therapy.

Wei Y ，Lv H ，Shaikh AB ，Han W ，Hou H ，Zhang Z ，Wang S ，Shang P ... -  《-》