The Role of Thrombo-inflammation in Ischemic Stroke: Focus on the Manipulation and Clinical Application.

Stroke leaves a great economic burden due to its high morbidity and mortality. Rapid revascularization of targeted vessel(s) is the effective treatment for ischemic stroke, but subsequent ischemia-reperfusion (I/R) injury is a common complication following revascularization, leading to microcirculation dysfunction and infarct volume increase. Thrombo-inflammation, the interaction between thrombosis and inflammation, plays a critical role in the pathophysiology of ischemic stroke. In the context of I/R injury, thrombo-inflammation consists of platelet activation, endothelial injury, and inflammatory cell infiltration. Numerous studies are devoted to exploring methods of regulating thrombo-inflammation to mitigate I/R injury post-stroke, including blocking activations of platelets and neutrophils. Drugs such as antiplatelet medications, anticoagulants, and glucocorticoids have been confirmed to have the potential to regulate thrombo-inflammation. Furthermore, several recently developed drugs have also shown promises in relieving I/R injury by manipulating thrombo-inflammation. However, the majority of these studies are still in the preclinical stage. Herein, in this review, we will address the mechanisms of thrombo-inflammation in ischemic stroke, related research advances, and particularly the clinical feasibility of thrombo-inflammation as a therapeutic strategy against I/R injury.

Hinokitiol-iron complex is a ferroptosis inducer to inhibit triple-negative breast tumor growth.

BACKGROUND: Ferroptosis is a unique cell death, dependent on iron and phospholipid peroxidation, involved in massive processes of physiopathology. Tremendous attention has been caught in oncology, particularly for those therapy-resistant cancers in the mesenchymal state prone to metastasis due to their exquisite vulnerability to ferroptosis. Therefore, a therapeutical ferroptosis inducer is now underway to be exploited. RESULTS: A natural compound, hinokitiol (hino), has been considered to be an iron chelator. We have a novel finding that hino complexed with iron to form Fe(hino)3 can function as a ferroptosis inducer in vitro. The efficiency, compared with the same concentration of iron, increases nearly 1000 folds. Other iron chelators, ferroptosis inhibitors, or antioxidants can inhibit Fe(hino)3-induced ferroptosis. The complex Fe(hino)3 efficacy is further confirmed in orthotopic triple-negative breast cancer (TNBC) tumor models that Fe(hino)3 significantly boosted lipid peroxidation to induce ferroptosis and significantly reduced the sizes of TNBC cell-derived tumors. The drug's safety was also evaluated, and no detrimental side effects were found with the tested dosage. CONCLUSIONS: When entering cells, the chelated iron by hinokitiol as a complex Fe(hino)3 is proposed to be redox-active to vigorously promote the production of free radicals via the Fenton reaction. Thus, Fe(hino)3 is a ferroptosis inducer and, therapeutically, exhibits anti-TNBC activity.

Rescuers from the Other Shore: Intercellular Mitochondrial Transfer and Its Implications in Central Nervous System Injury and Diseases.

As the powerhouse and core of cellular metabolism and survival, mitochondria are the essential organelle in mammalian cells and maintain cellular homeostasis by changing their content and morphology to meet demands through mitochondrial quality control. It has been observed that mitochondria can move between cells under physiological and pathophysiological conditions, which provides a novel strategy for preserving mitochondrial homeostasis and also a therapeutic target for applications in clinical settings. Therefore, in this review, we will summarize currently known mechanisms of intercellular mitochondrial transfer, including modes, triggers, and functions. Due to the highly demanded energy and indispensable intercellular linkages of the central nervous system (CNS), we highlight the mitochondrial transfer in CNS. We also discuss future application possibilities and difficulties that need to be addressed in the treatment of CNS injury and diseases. This clarification should shed light on its potential clinical applications as a promising therapeutic target in neurological diseases. Intercellular mitochondrial transfer maintains the homeostasis of central nervous system (CNS), and its alteration is related to several neurological diseases. Supplementing exogenous mitochondrial donor cells and mitochondria, or utilizing some medications to regulate the process of transfer might mitigate the disease and injury.

Stimulation of Hepatic Ferritinophagy Mitigates Irp2 Depletion-Induced Anemia.

BACKGROUND: Iron regulatory proteins (IRPs) maintain cellular iron homeostasis. Due to aberrant tissue-iron distribution, Irp2-deficient mice suffer microcytic anemia and neurodegeneration, while iron overload occurs in the liver and intestine. We previously found that Irp2 deficiency-induced Hif2 plays an important role in neurodegeneration. METHODS: To test the role of Hif2 in Irp2 deficiency-induced anemia, we used Irp2 global knockout mice. Following Hif2 inhibition, routine blood tests, iron availability in bone marrow, histological assays, and biochemical analysis were performed to assess anemia improvement and tissue iron distribution. RESULTS: We found that Hif2 inhibition improved anemia. The increased iron bioavailability for erythropoiesis was mainly derived from hepatic iron release, and secondly from enhanced intestinal absorption. We further demonstrate that nuclear receptor coactivator 4 (Ncoa4) was upregulated for iron release via the process of ferritinophagy. The released iron was utilized not only for intracellular Fe-S biogenesis but also for erythropoiesis after being exported from the liver to circulation. The hepatic iron export reduced hepcidin expression to further support iron absorption through the hepcidin-ferroportin axis to alleviate intestinal iron overload. CONCLUSION: Irp2 not only regulates cellular iron homeostasis but also tissue iron distribution by managing the involvement of Hif2-Ncoa4.

Protective Effects of Hif2 Inhibitor PT-2385 on a Neurological Disorder Induced by Deficiency of Irp2.

Iron regulatory protein 2 (IRP2) deficiency in mice and humans causes microcytic anemia and neurodegeneration due to functional cellular iron depletion. Our previous in vitro data have demonstrated that Irp2 depletion upregulates hypoxia-inducible factor subunits Hif1α and Hif2α expression; inhibition of Hif2α rescues Irp2 ablation-induced mitochondrial dysfunction; and inhibition of Hif1α suppresses the overdose production of lactic acid derived from actively aerobic glycolysis. We wonder whether Hif1α and Hif2α are also elevated in vivo and play a similar role in neurological disorder of Irp2 -/- mice. In this study, we confirmed the upregulation of Hif2α, not Hif1α, in tissues, particularly in the central nervous system including the mainly affected cerebellum and spinal cord of Irp2 -/- mice. Consistent with this observation, inhibition of Hif2α by PT-2385, not Hif1α by PX-478, prevented neurodegenerative symptoms, which were proved by Purkinje cell arrangement from the shrunken and irregular to the full and regular array. PT-2385 treatment did not only modulate mitochondrial morphology and quality in vivo but also suppressed glycolysis. Consequently, the shift of energy metabolism from glycolysis to oxidative phosphorylation (OXPHOS) was reversed. Our results indicate that Irp2 depletion-induced Hif2α is, in vivo, in charge of the switch between OXPHOS and glycolysis, suggesting that, for the first time to our knowledge, Hif2α is a clinically potential target in the treatment of IRP2 deficiency-induced neurodegenerative syndrome.

SS-31 efficacy in a mouse model of Friedreich ataxia by upregulation of frataxin expression.

Friedreich ataxia (FRDA) is a serious hereditary neurodegenerative disease, mostly accompanied with hypertrophic cardiomyopathy, caused by the reduced expression of frataxin (FXN). However, there is still no effective treatment. Our previous studies have shown that SS-31, a mitochondrion-targeted peptide, is capable to upregulate the expression of FXN and improve the mitochondrial function in cells derived from FRDA patients. To further explore the potential of SS-31, we used the GAA expansion-based models, including Y47 and YG8R (Fxn KIKO) mice, primary neurons and macrophages from the mice and cells derived from FRDA patients. After once-daily intraperitoneal injection of 1 mg/kg SS-31 for 1 month, we observed the significant improvement of motor function. The vacuolation in dorsal root ganglia, lesions in dentate nuclei and the lost thickness of myelin sheath of spinal cord were all repaired after SS-31 treatment. In addition, the hypertrophic cardiomyocytes and disarrayed abnormal Purkinje cells were dramatically reduced. Interestingly, we found that SS-31 treatment upregulated FXN expression not only at the translational levels as observed in cell culture but also at mRNA levels in vivo. Consequently, mitochondrial morphology and function were greatly improved in all tested tissues. Importantly, our data provided additional evidence that the maintenance of the therapeutic benefits needed continuous drug administration. Taken together, our findings have demonstrated the effectiveness of SS-31 treatment through the upregulation of FXN in vivo and offer guidance of the potential usage in the clinical application for FRDA.

Iron regulatory protein 2 modulates the switch from aerobic glycolysis to oxidative phosphorylation in mouse embryonic fibroblasts.

The importance of the role of iron regulatory proteins (IRPs) in mitochondrial iron homeostasis and function has been raised. To understand how an IRP affects mitochondrial function, we used globally Irp2-depleted mouse embryonic fibroblasts (MEFs) and found that Irp2 ablation significantly induced the expression of both hypoxia-inducible factor subunits, Hif1α and Hif2α. The increase of Hif1α up-regulated its targeted genes, enhancing glycolysis, and the increase of Hif2α down-regulated the expression of iron-sulfur cluster (Fe-S) biogenesis-related and electron transport chain (ETC)-related genes, weakening mitochondrial respiration. Inhibition of Hif1α by genetic knockdown or a specific inhibitor prevented Hif1α-targeted gene expression, leading to decreased aerobic glycolysis. Inhibition of Hif2α by genetic knockdown or selective disruption of the heterodimerization of Hif2α and Hif1ß restored the mitochondrial ETC and coupled oxidative phosphorylation (OXPHOS) by enhancing Fe-S biogenesis and increasing ETC-related gene expression. Our results indicate that Irp2 modulates the metabolic switch from aerobic glycolysis to OXPHOS that is mediated by Hif1α and Hif2α in MEFs.