Deciphering the Iron Side of Stroke: Neurodegeneration at the Crossroads Between Iron Dyshomeostasis, Excitotoxicity, and Ferroptosis

In general, iron represents a double-edged sword in metabolism in most tissues, especially in the brain. Although the high metabolic demands of brain cells require iron as a redox-active metal for ATP-producing enzymes, the brain is highly vulnerable to the devastating consequences of excessive iron-induced oxidative stress and, as recently found, to ferroptosis as well. The blood–brain barrier (BBB) protects the brain from fluctuations in systemic iron. Under pathological conditions, especially in acute brain pathologies such as stroke, the BBB is disrupted, and iron pools from the blood gain sudden access to the brain parenchyma, which is crucial in mediating stroke-induced neurodegeneration. Each brain cell type reacts with changes in their expression of proteins involved in iron uptake, efflux, storage, and mobilization to preserve its internal iron homeostasis, with specific organelles such as mitochondria showing specialized responses. However, during ischemia, neurons are challenged with excess extracellular glutamate in the presence of high levels of extracellular iron; this causes glutamate receptor overactivation that boosts neuronal iron uptake and a subsequent overproduction of membrane peroxides. This glutamate-driven neuronal death can be attenuated by iron-chelating compounds or free radical scavenger molecules. Moreover, vascular wall rupture in hemorrhagic stroke results in the accumulation and lysis of iron-rich red blood cells at the brain parenchyma and the subsequent presence of hemoglobin and heme iron at the extracellular milieu, thereby contributing to iron-induced lipid peroxidation and cell death. This review summarizes recent progresses made in understanding the ferroptosis component underlying both ischemic and hemorrhagic stroke subtypes

Modificacions neuroendocrinològiques amb l'estrès

Sota el terme estrès s'engloben una àmplia gamma de canvis orgànics que tenen lloc en resposta a tot un ventall d'estímuls i situacions que no podrien ser afrontats satisfactòriament mitjancant els mecanismes homeostàtics normals. Tant el component físic i psicòlogic dels estímuls estressants, la seva intensitat , com la forma en que els organismes hi són exposats, determinen el tipus de resposta que es posarà en marxa. Els estímuls estressants són processats a nivell del sistema nerviós central. Però els centres, les vies i els neurotransmissors implicats són encara lluny d'estar ben caracteritzats, si bé les vies noradrenèrgiques procedents del tronc encefàlic podrien tenir un paper rellevant. Per la seva banda, l'hipotàlem i la corticoliberina tenen un paper clau en la integració de tot aquest proces, i aixi, l'activació subsegüent de 1'eix neuroendocrí hipotalamico - pituitario - adrenal (HPA) constitueix un dels puntals de la resposta d'estrès. En situacions cròniques d'estrès, malgrat que la capacitat potencial de resposta de 1'eix HPA està notablement incrementada, la resposta de 1'adrenocorticotropina (ACTH) al mateix estímul (homotípic) està freqüentment atenuada (habituació), mentre que davant d' un estímul estressant nou (heterotípic) es troba, almenys en alguns casos, exacerbada (facilitació). Les perspectives de recerca es dirigeixen cap a l'estudi de la relació entre estrès i sistema immunitari, cada dia més clara.The term of stress comprises a myriad of organic changes occurring in response to a wide range of stimuli and situations which could not be satisfactorily faced by means of normal homeostatic mechanisms. Both the physical and psychological components of stressors, their intensity and the way the organisms are exposed to them, determine the type of response that will be triggered. Stressors are processed within the central nervous system, but the centers, pathways and neurotransmitters involved are far from being well understood. Nevertheless, brainstern noradrenergic system might be of relevance. Similarly, the hypothalamus and the corticotropin -releasing factor play a pivotal role in integrating this process, and thus, the subsequent activation of the neuroendocrine hypothalamicpituitary-adrenal (HPA) axis, one of the crucial components of the stress response. During chronic stress situations, despite the fact that the potential response of the HPA axis is increased, the adrenocorticotropin (ACTH) response to the same (homotypic) stimulus has usually been found to be attenuated (habituation) and that to novel (heterotypic) stressors to be exacerbated, at least in some cases (facilitation). The growing body of evidence about the close relationship between stress and the immune system opens a universe of research perspectives in this field

Bench-to-bedside review: Brain-lung interaction in the critically ill – a pending issue revisited

Brain and/or lung injury is the most frequent cause of admission to critical care units and patients in this setting frequently develop multiple organ dysfunction with high rates of morbidity and mortality. Mechanical ventilation is commonly used in the management of these critically ill patients and the consequent inflammatory response, together with other physiological factors, is also thought to be involved in distal organ dysfunction. This peripheral imbalance is based on a multiple-pathway cross-talk between the lungs and other organs, including the brain. Interestingly, acute respiratory distress syndrome survivors frequently present some cognitive deterioration at discharge. Such neurological dysfunction might be a secondary marker of injury and the neuroanatomical substrate for downstream impairment of other organs. Brain-lung interactions have received little attention in the literature, but recent evidence suggests that both the lungs and brain are promoters of inflammation through common mediators. This review addresses the current status of evidence regarding brain-lung interactions, their pathways and current interventions in critically ill patients receiving mechanical ventilation

Injurious mechanical ventilation affects neuronal activation in ventilated rats

Survivors of critical illness often have significant long-term brain dysfunction, and routine clinical procedures like mechanical ventilation (MV) may affect long-term brain outcome. We aimed to investigate the effect of the increase of tidal volume (Vt) on brain activation in a rat model. Male Sprague Dawley rats were randomized to three groups: 1) Basal: anesthetized unventilated animals, 2) low Vt (LVt): MV for three hours with Vt 8 ml/kg and zero positive end-expiratory pressure (ZEEP), and 3) high Vt (HVt) MV for three hours with Vt 30 ml/kg and ZEEP. We measured lung mechanics, mean arterial pressure (MAP), arterial blood gases, and plasma and lung levels of cytokines. We used immunohistochemistry to examine c-fos as a marker of neuronal activation. An additional group of spontaneously breathing rats was added to discriminate the effect of surgical procedure and anesthesia in the brain. After three hours on LVt, PaOdecreased and PaCOincreased significantly. MAP and compliance remained stable in MV groups. Systemic and pulmonary inflammation was higher in MV rats than in unventilated rats. Plasma TNFα was significantly higher in HVt than in LVt. Immunopositive cells to c-fos in the retrosplenial cortex and thalamus increased significantly in HVt rats but not in LVt or unventilated rats. MV promoted brain activation. The intensity of the response was higher in HVt animals, suggesting an iatrogenic effect of MV on the brain. These findings suggest that this novel cross-talking mechanism between the lung and the brain should be explored in patients undergoing MV

Relevance of Porcine Stroke Models to Bridge the Gap from Pre-Clinical Findings to Clinical Implementation

Altres ajuts: This research is supported by grants from the Fondo de Investigaciones Sanitarias-Instituto de Salud Carlos III (ISCIII) to A.D. that was susceptible to be co-financed by FEDER funds, and a grant from Agència de Gestió d'Ajuts Universitaris i de Recerca to A.D. and to T.G. The group has received funding from "la Caixa Foundation" CI15-00009, from the European Institute of Innovation and Technology (EIT), which receives support from the European Union's Horizon 2020 research and innovation programme, from the Fundación para la Innovación y la Prospectiva en Salud en España (FIPSE) program 3594-18. M.M.-S. is a recipient of a PFIS contract FI19/00174.In the search of animal stroke models providing translational advantages for biomedical research, pigs are large mammals with interesting brain characteristics and wide social acceptance. Compared to rodents, pigs have human-like highly gyrencephalic brains. In addition, increasingly through phylogeny, animals have more sophisticated white matter connectivity; thus, ratios of white-to-gray matter in humans and pigs are higher than in rodents. Swine models provide the opportunity to study the effect of stroke with emphasis on white matter damage and neuroanatomical changes in connectivity, and their pathophysiological correlate. In addition, the subarachnoid space surrounding the swine brain resembles that of humans. This allows the accumulation of blood and clots in subarachnoid hemorrhage models mimicking the clinical condition. The clot accumulation has been reported to mediate pathological mechanisms known to contribute to infarct progression and final damage in stroke patients. Importantly, swine allows trustworthy tracking of brain damage evolution using the same non-invasive multimodal imaging sequences used in the clinical practice. Moreover, several models of comorbidities and pathologies usually found in stroke patients have recently been established in swine. We review here ischemic and hemorrhagic stroke models reported so far in pigs. The advantages and limitations of each model are also discussed

Comparative Proteomics Unveils LRRFIP1 as a New Player in the DAPK1 Interactome of Neurons Exposed to Oxygen and Glucose Deprivation

Altres ajuts: The group has received funding from 'la Caixa Foundation' CI15-00009, from the European Institute of Innovation and Technology (EIT) PoC-2016-SPAIN-04, which receives support from the European Union's Horizon 2020 research and innovation program, and from the 'Fundación para la Innovación y la Prospectiva en Salud en España (FIPSE)' program 3594-18.Death-associated protein kinase 1 (DAPK1) is a pleiotropic hub of a number of networked distributed intracellular processes. Among them, DAPK1 is known to interact with the excitotoxicity driver NMDA receptor (NMDAR), and in sudden pathophysiological conditions of the brain, e.g., stroke, several lines of evidence link DAPK1 with the transduction of glutamate-induced events that determine neuronal fate. In turn, DAPK1 expression and activity are known to be affected by the redox status of the cell. To delineate specific and differential neuronal DAPK1 interactors in stroke-like conditions in vitro, we exposed primary cultures of rat cortical neurons to oxygen/glucose deprivation (OGD), a condition that increases reactive oxygen species (ROS) and lipid peroxides. OGD or control samples were co-immunoprecipitated separately, trypsin-digested, and proteins in the interactome identified by high-resolution LC-MS/MS. Data were processed and curated using bioinformatics tools. OGD increased total DAPK1 protein levels, cleavage into shorter isoforms, and dephosphorylation to render the active DAPK1 form. The DAPK1 interactome comprises some 600 proteins, mostly involving binding, catalytic and structural molecular functions. OGD up-regulated 190 and down-regulated 192 candidate DAPK1-interacting proteins. Some differentially up-regulated interactors related to NMDAR were validated by WB. In addition, a novel differential DAPK1 partner, LRRFIP1, was further confirmed by reverse Co-IP. Furthermore, LRRFIP1 levels were increased by pro-oxidant conditions such as ODG or the ferroptosis inducer erastin. The present study identifies novel partners of DAPK1, such as LRRFIP1, which are suitable as targets for neuroprotection

Targeting pro-oxidant iron with exogenously administered apotransferrin provides benefits associated with changes in crucial cellular iron gate protein TfR in a model of intracerebral hemorrhagic stroke in mice

We have previously demonstrated that the post-stroke administration of iron-free transferrin (apotransferrin, ATf) is beneficial in different models of ischemic stroke (IS) through the inhibition of the neuronal uptake of pro-oxidant iron. In the present study, we asked whether ATf is safe and also beneficial when given after the induction of intracerebral hemorrhage (ICH) in mice, and investigated the underlying mechanisms. We first compared the main iron actors in the brain of IS- or collagenase-induced ICH mice and then obtained insight into these iron-related proteins in ICH 72 h after the administration of ATf. The infarct size of the IS mice was double that of hemorrhage in ICH mice, but both groups showed similar body weight loss, edema, and increased ferritin and transferrin levels in the ipsilateral brain hemisphere. Although the administration of human ATf (hATf) to ICH mice did not alter the hemorrhage volume or levels of the classical ferroptosis GPX4/system xc- pathways, hATf induced better neurobehavioral performance, decreased 4-hydroxynonenal levels and those of the second-generation ferroptosis marker transferrin receptor (TfR), and restored the mRNA levels of the recently recognized cytosolic iron chaperone poly(RC) binding protein 2. In addition, hATf treatment lowered the ICH-induced increase in both endogenous mouse transferrin mRNA levels and the activation of caspase-2. In conclusion, hATf treatment provides neurobehavioral benefits post-ICH associated with the modulation of iron/oxidative players

Establishment of a reproducible and minimally invasive ischemic stroke model in swine

The need for advances in the management/treatment options for ischemic stroke patients requires that upcoming preclinical research uses animals with more human-like brain characteristics. The porcine brain is considered appropriate, although the presence of the rete mirabile (RM) prevents direct catheterization of the intracranial arteries to produce focal cerebral ischemia. To develop a reproducible minimally invasive porcine stroke model, a guide catheter and guide wire were introduced through the femoral artery until reaching the left RM. Using the pressure cooker technique, Squid-12 embolization material was deposited to fill, overflow, and occlude the left RM, the left internal carotid artery, and left circle of Willis wing up to the origins of the middle cerebral arteries (MCAs), mimicking the occlusion produced in the filament model in rodents. Longitudinal multimodal cerebral MRI was conducted to assess the brain damage and cerebral blood supply. The technique we describe here occluded up to the origins of the MCAs in 7 of 8 swine, inducing early damage 90 minutes after occlusion that later evolved to a large cerebral infarction and producing no mortality during the intervention. This minimally invasive ischemic stroke model in swine produced reproducible infarcts and shows translational features common to human stroke

Modificacions neuroendocrinològiques amb l'estrès

Sota el terme estrès s'engloben una àmplia gamma de canvis orgànics que tenen lloc en resposta a tot un ventall d'estímuls i situacions que no podrien ser afrontats satisfactòriament mitjancant els mecanismes homeostàtics normals. Tant el component físic i psicòlogic dels estímuls estressants, la seva intensitat , com la forma en que els organismes hi són exposats, determinen el tipus de resposta que es posarà en marxa. Els estímuls estressants són processats a nivell del sistema nerviós central. Però els centres, les vies i els neurotransmissors implicats són encara lluny d'estar ben caracteritzats, si bé les vies noradrenèrgiques procedents del tronc encefàlic podrien tenir un paper rellevant. Per la seva banda, l'hipotàlem i la corticoliberina tenen un paper clau en la integració de tot aquest proces, i aixi, l'activació subsegüent de 1'eix neuroendocrí hipotalamico - pituitario - adrenal (HPA) constitueix un dels puntals de la resposta d'estrès. En situacions cròniques d'estrès, malgrat que la capacitat potencial de resposta de 1'eix HPA està notablement incrementada, la resposta de 1'adrenocorticotropina (ACTH) al mateix estímul (homotípic) està freqüentment atenuada (habituació), mentre que davant d' un estímul estressant nou (heterotípic) es troba, almenys en alguns casos, exacerbada (facilitació). Les perspectives de recerca es dirigeixen cap a l'estudi de la relació entre estrès i sistema immunitari, cada dia més clara.The term of stress comprises a myriad of organic changes occurring in response to a wide range of stimuli and situations which could not be satisfactorily faced by means of normal homeostatic mechanisms. Both the physical and psychological components of stressors, their intensity and the way the organisms are exposed to them, determine the type of response that will be triggered. Stressors are processed within the central nervous system, but the centers, pathways and neurotransmitters involved are far from being well understood. Nevertheless, brainstern noradrenergic system might be of relevance. Similarly, the hypothalamus and the corticotropin -releasing factor play a pivotal role in integrating this process, and thus, the subsequent activation of the neuroendocrine hypothalamicpituitary-adrenal (HPA) axis, one of the crucial components of the stress response. During chronic stress situations, despite the fact that the potential response of the HPA axis is increased, the adrenocorticotropin (ACTH) response to the same (homotypic) stimulus has usually been found to be attenuated (habituation) and that to novel (heterotypic) stressors to be exacerbated, at least in some cases (facilitation). The growing body of evidence about the close relationship between stress and the immune system opens a universe of research perspectives in this field