Ferroptosis pathway regulation by the Dynamin superfamily of large GTPases

Ferroptosis is a recently described form of regulated cell death characterised by the iron-dependent generation of lethal amounts of lipid reactive oxygen species (ROS). Therefore, iron import is an essential process for the execution of ferroptosis. Iron uptake via transferrin receptor endocytosis is dependent on the GTPases dynamin 1 and 2. Indeed, the dynamin 1 and 2 inhibitor dynasore, can protect from ischemia/reperfusion injury, a type of tissue damage that has been shown to be also blocked by the ferroptosis inhibitor ferrostatin-1. Yet, it is unknown whether the regulation of iron uptake by dynamin 1 and 2 is essential for the execution of ferroptosis. A second characteristic hallmark of ferroptosis is the accumulation of ROS. Mitochondria play a central role in the generation of ROS through oxidative phosphorylation (OXPHOS). Importantly, experimental induction of ferroptosis was shown to induce mitochondrial fragmentation and mitochondrial ROS. Morphological changes of mitochondria are mainly regulated by another member of the dynamin family of GTPases, dynamin-related protein 1 (Drp1). Interestingly, heterozygous drp1 knockout mice show defective mitochondrial fission and low levels of lipid ROS in tissues. Yet, how mitochondrial events are regulated during ferroptosis, including a potential role of Drp1, have remained unexplored. The aim of this study was to investigate potential roles for the dynamin family members dynamin 1, 2 and Drp1 in the regulation of the ferroptosis pathway and to elucidate underlying molecular mechanisms. Surprisingly, while the dynamin 1 and 2 inhibitor dynasore efficiently blocked ferroptosis induction, silencing of its main molecular targets dynamin 1 and 2 was not sufficient to block ferroptosis. Instead, in cell free systems, dynasore showed radical scavenger properties and acted as a broadly active antioxidant. Moreover, we found that Drp1 translocates to mitochondria and promotes cysteine-deprivation induced (CDI) ferroptosis. Of note, we observed Drp1 to be phosphorylated upon induction of ferroptosis in a manner dependent on CaMKIIα. Collectively, these data propose that dynasore can function as a highly active inhibitor of ROS-driven types of cell death via combined modulation of the iron pool and inhibition of general ROS. On the other hand, our data reveal that dynamin 1 and 2 silencing is insufficient to regulate ferroptosis execution. Furthermore, we have reported a key role of Drp1 in the regulation of mitochondrial fragmentation in CDI ferroptosis. These findings contribute towards our understanding of the ferroptosis pathway, as well as its implication in the physiopathology of diseases associated with this type of cell death

Prevalence, features and predictive factors of liver nodules in Fontan surgery patients: The VALDIG Fonliver prospective cohort

Background & Aims: Fontan surgery is used to treat a variety of congenital heart malformations, and may lead to advanced chronic liver disease in the long-term. This study examines the prevalence, characteristics and predictors of liver nodules in patients following Fontan surgery. Methods: This was a prospective, cross-sectional, observational study conducted at 8 European centres. Consecutive patients who had undergone Fontan surgery underwent blood tests, abdominal ultrasonography (US), transient elastography (Fibroscan®), echocardiography, haemodynamic assessments, and abdominal MRI/CT scan. The primary outcome measure was liver nodules detected in the MRI/CT scan. Predictors of liver nodules were identified by multivariate logistic regression. Results: One hundred and fifty-two patients were enrolled (mean age 27.3 years). The mean time elapsed from surgery to inclusion was 18.3 years. Liver nodule prevalences were 29.6% (95% CI 23–37%) on US and 47.7% (95% CI 39–56%) on MRI/CT. Nodules were usually hyperechoic (76.5%), round-shaped (>80%), hyperenhancing in the arterial phase (92%) and located in the liver periphery (75%). The sensitivity and specificity of US were 50% (95% CI 38–62%) and 85.3% (95% CI 75–92%), respectively. Inter-imaging test agreement was low (adjusted kappa: 0.34). In the multivariate analysis, time since surgery >10 years was the single independent predictor of liver nodules (odds ratio 4.18; p = 0.040). Hepatocellular carcinoma was histologically diagnosed in 2 of the 8 patients with hypervascular liver nodules displaying washout. Conclusion: While liver nodules are frequent in Fontan patients, they may go unnoticed in US. Liver nodules are usually hyperechoic, hypervascular and predominantly peripheral. This population is at risk of hepatocellular carcinoma, the diagnosis of which requires confirmatory biopsy

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Dynasore Blocks Ferroptosis through Combined Modulation of Iron Uptake and Inhibition of Mitochondrial Respiration

Ferroptosis is a form of regulated necrosis characterized by a chain-reaction of detrimental membrane lipid peroxidation following collapse of glutathione peroxidase 4 (Gpx4) activity. This lipid peroxidation is catalyzed by labile ferric iron. Therefore, iron import mediated via transferrin receptors and both, enzymatic and non-enzymatic iron-dependent radical formation are crucial prerequisites for the execution of ferroptosis. Intriguingly, the dynamin inhibitor dynasore, which has been shown to block transferrin receptor endocytosis, can protect from ischemia/reperfusion injury as well as neuronal cell death following spinal cord injury. Yet, it is unknown how dynasore exerts these cell death-protective effects. Using small interfering RNA suppression, lipid reactive oxygen species (ROS), iron tracers and bona fide inducers of ferroptosis, we find that dynasore treatment in lung adenocarcinoma and neuronal cell lines strongly protects these from ferroptosis. Surprisingly, while the dynasore targets dynamin 1 and 2 promote extracellular iron uptake, their silencing was not sufficient to block ferroptosis suggesting that this route of extracellular iron uptake is dispensable for acute induction of ferroptosis and dynasore must have an additional off-target activity mediating full ferroptosis protection. Instead, in intact cells, dynasore inhibited mitochondrial respiration and thereby mitochondrial ROS production which can feed into detrimental lipid peroxidation and ferroptotic cell death in the presence of labile iron. In addition, in cell free systems, dynasore showed radical scavenger properties and acted as a broadly active antioxidant which is superior to N-acetylcysteine (NAC) in blocking ferroptosis. Thus, dynasore can function as a highly active inhibitor of ROS-driven types of cell death via combined modulation of the iron pool and inhibition of general ROS by simultaneously blocking two routes required for ROS and lipid-ROS driven cell death, respectively. These data have important implications for the interpretation of studies observing tissue-protective effects of this dynamin inhibitor as well as raise awareness that off-target ROS scavenging activities of small molecules used to interrogate the ferroptosis pathway should be taken into consideration

Revista de psicodidáctica

Título, resumen y palabras clave en español y en inglésResumen basado en el de la publicaciónLa tutoría es un instrumento ligado a la docencia universitaria que, en el contexto de la universidad española, no siempre ha desarrollado sus potencialidades. La incorporación de las universidades españoles al sistema europeo abre vías muy interesantes para el desarrollo de sistemas tutoriales que realmente contribuyan a la educación de los alumnos. Se exponen las posibilidades de contribución a la formación universitaria de la acción tutorial.ES

Claves de la práctica de la tutorización entre iguales en las universidades anglosajonas: Algunas aplicaciones a nuestra realidad universitaria

Las universidades anglosajonas, en general, tienen un modo de funcionamiento particular que difiere del que existe en nuestras universidades. Los contexto, las tradiciones y las herencias históricas no son tampoco las mismas. Así la figura del tutor y la utilización de sus funciones viene existiendo en aquéllas desde hace mucho mas tiempo que en nuestras instituciones, constituyéndose en un recurso pedagógico de indudable entidad en el entramado organizativo de la enseñanza universitaria. A lo largo del presente trabajo hacernos una revisión crítica de las diferentes realidades de la "tutoría entre iguales" (peer teaching), con la pretensión de discernir aquellos aspectos que, debidamente contextualizados en la tradición y características de la realidad de nuestras Facultades Universitarias, puedan servir a la hora de diseñar innovaciones respiro a la enseñanza y el aprendizaje en nuestras instituciones de educación superior ante el reto de una mayor calidad universitaria. Además de las conclusiones deducidas del estudio critico, formulamos unas propuestas en orden a introducir mejoras en la práctica docente en nuestras instituciones universitarias

Ferroptosis in Cancer Cell Biology

A major hallmark of cancer is successful evasion of regulated forms of cell death. Ferroptosis is a recently discovered type of regulated necrosis which, unlike apoptosis or necroptosis, is independent of caspase activity and receptor-interacting protein 1 (RIPK1) kinase activity. Instead, ferroptotic cells die following iron-dependent lipid peroxidation, a process which is antagonised by glutathione peroxidase 4 (GPX4) and ferroptosis suppressor protein 1 (FSP1). Importantly, tumour cells escaping other forms of cell death have been suggested to maintain or acquire sensitivity to ferroptosis. Therefore, therapeutic exploitation of ferroptosis in cancer has received increasing attention. Here, we systematically review current literature on ferroptosis signalling, cross-signalling to cellular metabolism in cancer and a potential role for ferroptosis in tumour suppression and tumour immunology. By summarising current findings on cell biology relevant to ferroptosis in cancer, we aim to point out new conceptual avenues for utilising ferroptosis in systemic treatment approaches for cancer

The Selective Loss of Purkinje Cells Induces Specific Peripheral Immune Alterations.

[EN]The progression of neurodegenerative diseases is reciprocally associated with impairments in peripheral immune responses. We investigated different contexts of selective neurodegeneration to identify specific alterations of peripheral immune cells and, at the same time, discover potential biomarkers associated to this pathological condition. Consequently, a model of human cerebellar degeneration and ataxia -the Purkinje Cell Degeneration (PCD) mouse- has been employed, as it allows the study of different processes of selective neuronal death in the same animal, i.e., Purkinje cells in the cerebellum and mitral cells in the olfactory bulb. Infiltrated leukocytes were studied in both brain areas and compared with those from other standardized neuroinflammatory models obtained by administering either gamma radiation or lipopolysaccharide. Moreover, both myeloid and lymphoid splenic populations were analyzed by flow cytometry, focusing on markers of functional maturity and antigen presentation. The severity and type of neural damage and inflammation affected immune cell infiltration. Leukocytes were more numerous in the cerebellum of PCD mice, being located predominantly within those cerebellar layers mostly affected by neurodegeneration, in a completely different manner than the typical models of induced neuroinflammation. Furthermore, the milder degeneration of the olfactory bulb did not foster leukocyte attraction. Concerning the splenic analysis, in PCD mice we found: (1) a decreased percentage of several myeloid cell subsets, and (2) a reduced mean fluorescence intensity in those myeloid markers related to both antigen presentation and functional maturity. In conclusion, the selective degeneration of Purkinje cells triggers a specific effect on peripheral immune cells, fostering both attraction and functional changes. This fact endorses the employment of peripheral immune cell populations as concrete biomarkers for monitoring different neuronal death processes

Dynasore Blocks Ferroptosis through Combined Modulation of Iron Uptake and Inhibition of Mitochondrial Respiration

Ferroptosis is a form of regulated necrosis characterized by a chain-reaction of detrimental membrane lipid peroxidation following collapse of glutathione peroxidase 4 (Gpx4) activity. This lipid peroxidation is catalyzed by labile ferric iron. Therefore, iron import mediated via transferrin receptors and both, enzymatic and non-enzymatic iron-dependent radical formation are crucial prerequisites for the execution of ferroptosis. Intriguingly, the dynamin inhibitor dynasore, which has been shown to block transferrin receptor endocytosis, can protect from ischemia/reperfusion injury as well as neuronal cell death following spinal cord injury. Yet, it is unknown how dynasore exerts these cell death-protective effects. Using small interfering RNA suppression, lipid reactive oxygen species (ROS), iron tracers and bona fide inducers of ferroptosis, we find that dynasore treatment in lung adenocarcinoma and neuronal cell lines strongly protects these from ferroptosis. Surprisingly, while the dynasore targets dynamin 1 and 2 promote extracellular iron uptake, their silencing was not sufficient to block ferroptosis suggesting that this route of extracellular iron uptake is dispensable for acute induction of ferroptosis and dynasore must have an additional off-target activity mediating full ferroptosis protection. Instead, in intact cells, dynasore inhibited mitochondrial respiration and thereby mitochondrial ROS production which can feed into detrimental lipid peroxidation and ferroptotic cell death in the presence of labile iron. In addition, in cell free systems, dynasore showed radical scavenger properties and acted as a broadly active antioxidant which is superior to N-acetylcysteine (NAC) in blocking ferroptosis. Thus, dynasore can function as a highly active inhibitor of ROS-driven types of cell death via combined modulation of the iron pool and inhibition of general ROS by simultaneously blocking two routes required for ROS and lipid-ROS driven cell death, respectively. These data have important implications for the interpretation of studies observing tissue-protective effects of this dynamin inhibitor as well as raise awareness that off-target ROS scavenging activities of small molecules used to interrogate the ferroptosis pathway should be taken into consideration