Transferrin Enhances Neuronal Differentiation.

Although transferrin (Tf) is a glycoprotein best known for its role in iron delivery, iron-independent functions have also been reported. Here, we assessed apoTf (aTf) treatment effects on Neuro-2a (N2a) cells, a mouse neuroblastoma cell line which, once differentiated, shares many properties with neurons, including process outgrowth, expression of selective neuronal markers, and electrical activity. We first examined the binding of Tf to its receptor (TfR) in our model and verified that, like neurons, N2a cells can internalize Tf from the culture medium. Next, studies on neuronal developmental parameters showed that Tf increases N2a survival through a decrease in apoptosis. Additionally, Tf accelerated the morphological development of N2a cells by promoting neurite outgrowth. These pro-differentiating effects were also observed in primary cultures of mouse cortical neurons treated with aTf, as neurons matured at a higher rate than controls and showed a decrease in the expression of early neuronal markers. Further experiments in iron-enriched and iron-deficient media showed that Tf preserved its pro-differentiation properties in N2a cells, with results hinting at a modulatory role for iron. Moreover, N2a-microglia co-cultures revealed an increase in IL-10 upon aTf treatment, which may be thought to favor N2a differentiation. Taken together, these findings suggest that Tf reduces cell death and favors the neuronal differentiation process, thus making Tf a promising candidate to be used in regenerative strategies for neurodegenerative diseases.

Transferrin Receptor Is Necessary for Proper Oligodendrocyte Iron Homeostasis and Development.

To test the hypothesis that the transferrin (Tf) cycle has unique importance for oligodendrocyte development and function, we disrupted the expression of the Tf receptor (Tfr) gene in oligodendrocyte progenitor cells (OPCs) on mice of either sex using the Cre/lox system. This ablation results in the elimination of iron incorporation via the Tf cycle but leaves other Tf functions intact. Mice lacking Tfr, specifically in NG2 or Sox10-positive OPCs, developed a hypomyelination phenotype. Both OPC differentiation and myelination were affected, and Tfr deletion resulted in impaired OPC iron absorption. Specifically, the brains of Tfr cKO animals presented a reduction in the quantity of myelinated axons, as well as fewer mature oligodendrocytes. In contrast, the ablation of Tfr in adult mice affected neither mature oligodendrocytes nor myelin synthesis. RNA-seq analysis performed in Tfr cKO OPCs revealed misregulated genes involved in OPC maturation, myelination, and mitochondrial activity. Tfr deletion in cortical OPCs also disrupted the activity of the mTORC1 signaling pathway, epigenetic mechanisms critical for gene transcription and the expression of structural mitochondrial genes. RNA-seq studies were additionally conducted in OPCs in which iron storage was disrupted by deleting the ferritin heavy chain. These OPCs display abnormal regulation of genes associated with iron transport, antioxidant activity, and mitochondrial activity. Thus, our results indicate that the Tf cycle is central for iron homeostasis in OPCs during postnatal development and suggest that both iron uptake via Tfr and iron storage in ferritin are critical for energy production, mitochondrial activity, and maturation of postnatal OPCs.SIGNIFICANCE STATEMENT By knocking-out transferrin receptor (Tfr) specifically in oligodendrocyte progenitor cells (OPCs), we have established that iron incorporation via the Tf cycle is key for OPC iron homeostasis and for the normal function of these cells during the postnatal development of the CNS. Moreover, RNA-seq analysis indicated that both Tfr iron uptake and ferritin iron storage are critical for proper OPC mitochondrial activity, energy production, and maturation.

Lanthionine Ketimine Ethyl Ester Accelerates Remyelination in a Mouse Model of Multiple Sclerosis.

Although over 20 disease modifying therapies are approved to treat Multiple Sclerosis (MS), these do not increase remyelination of demyelinated axons or mitigate axon damage. Previous studies showed that lanthionine ketenamine ethyl ester (LKE) reduces clinical signs in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS and increased maturation of oligodendrocyte (OL) progenitor cells (OPCs) in vitro. In the current study, we used the cuprizone (CPZ) demyelination model of MS to test if LKE could increase remyelination. The corpus callosum (CC) and somatosensory cortex was examined by immunohistochemistry (IHC), electron microscopy and for mRNA expression changes in mice provided 5 weeks of CPZ diet followed by 2 weeks of normal diet in the presence of LKE or vehicle. A significant increase in the number of myelinated axons, and increased myelin thickness was observed in the CC of LKE-treated groups compared to vehicle-treated groups. LKE also increased myelin basic protein and proteolipid protein expression in the CC and cortex, and increased the number of mature OLs in the cortex. In contrast, LKE did not increase the percentage of proliferating OPCs suggesting effects on OPC survival and differentiation but not proliferation. The effects of LKE on OL maturation and remyelination were supported by similar changes in their relative mRNA levels. Interestingly, LKE did not have significant effects on GFAP or Iba1 immunostaining or mRNA levels. These findings suggest that remyelinating actions of LKE can potentially be formulated to induce remyelination in neurological diseases associated with demyelination including MS.

Importancia de la ruta de señalización JAK/STAT en la sepsis / Importance of the JAK/STAT signaling pathway in sepsis

RESUMEN El transductor de señal Janus-Kinasa y la vía de activación de la transcripción conocida como JAK/STAT es una ruta de señalización principal para la transducción de información en muchas citocinas inflamatorias implicadas durante la sepsis. Se ha demostrado que la vía JAK/STAT está fuertemente relacionada con el fallo multiorgánico, además que muchas citocinas pueden ejercer sus efectos biológicos a través de esta ruta. En los últimos años, se ha logrado un progreso significativo en la comprensión de las funciones de este complejo, sin embargo, su rol en la sepsis como objetivo terapéutico permanece en experimentación. En esta revisión se describen las funciones específicas de la vía JAK/STAT, su rol en la sepsis y presentamos un enfoque traslacional respecto a la perspectiva terapéutica para inhibir esta ruta de señalización durante la sepsis y su interacción con enfermedades inflamatorias como la COVID-19.

ABSTRACT The Janus-Kinase signal transducer and the transcription activation pathway known as JAK /STAT is a major signaling pathway for the transduction of information in many inflammatory cytokines involved during sepsis. The JAK /STAT pathway has been shown to be strongly related to multiorgan failure, and many cytokines can exert their biological effects through this pathway. In recent years, considerable progress has been made in understanding functions of this complex; however, its role in sepsis as a therapeutic target remains under experimentation. This review describes the specific functions of the JAK /STAT pathway, its role in sepsis, and presents a translational approach to the therapeutic perspective aiming to inhibit this signaling pathway during sepsis and its interaction with inflammatory diseases such as COVID-19.

Mean platelet volume and mean platelet volume to platelet count ratio as predictors of severity and mortality in sepsis.

INTRODUCTION: Sepsis is a public health problem due to its high prevalence and mortality. Mean platelet volume (MPV), a biomarker reported in routine blood counts, has been investigated and shows promise for determining fatal outcomes in septic patients. OBJECTIVE: Evaluate whether the mean platelet volume (MPV) and mean platelet volume-to-platelet count (MPV/P) ratio are predictors of clinical severity and mortality in patients with sepsis. METHODS: A prospective population cohort of 163 patients aged 18-97 years was recruited at the Intensive Care Unit of Pablo Arturo Hospital, Quito, Ecuador from 2017-2019 and followed up for 28 days. Patients were diagnosed with sepsis based on SEPSIS-3 septic shock criteria; in which the MPV and the MPV/P ratio were measured on days 1, 2, and 3. Sequential organ failure assessment (SOFA) score and presence of septic shock assessed clinical severity. Mortality on day 28 was considered the fatal outcome. RESULTS: The average age of the patients was 61,15 years (SD 20,94) and female sex was predominant. MPV cutoff points at days 1, 2 and 3 were >9,45fL, >8,95fL and >8, 85fL; and (MPV/P) ratio >8, 18, >4, 12 y >3, 95, respectively. MPV at days 2 (9,85fL) and 3 (8,55fL) and (MPV/P) ratio at days 1 (4,42), 2 (4,21), and 3 (8,55), were predictors of clinical severity assessed by septic shock, which reached significance in the ROC curves. MPV and (MPV/P) ratio were also predictors of clinical severity determined by SOFA at days 1, 2, and 3, where higher values were observed in non-survivors reaching significance in all categories. MPV and MPV/P ratio at days 1, 2 and 3 were independent predictor factors of mortality using Cox proportional hazards model (HR 2,31; 95% CI 1,36-3,94), (HR 2,11; 95% CI 1,17-3,82), (HR 2,13; 95% CI 1,07-4,21) and (HR 2,38; 95% CI 1,38-4,12), (HR 2,15; 95% CI 1,14-4,06), (HR 4,43; 95% CI, 1,72-11,37) respectively. CONCLUSIONS: MPV and the MPV/P ratio are predictors of clinical severity and mortality in sepsis. The MPV and its coefficient are indicators of the biological behavior of platelets in sepsis. They should be considered as a cost-effective and rapidly available tool that guides the treatment.

Lactato y catecolaminas: respuesta fisiológica en el paciente crítico / Lactate and catecholamines: a physiological response in critically ill patients

RESUMEN El lactato es un metabolito altamente dinámico que, en condiciones anaerobias, es producido por hipoxia o isquemia; y en condiciones aerobias, es sintetizado por un mecanismo impulsado por la estimulación adrenérgica, a través del receptor β2, que potencia la acción de la bomba sodio-potasio, y por un estado de glicólisis aerobia acelerada. Este metabolito es capaz de intercambiarse entre diferentes células productoras y consumidoras, con lo que asegura la materia prima para obtener energía. El sistema nervioso simpático responde a los estímulos de estrés con la liberación de catecolaminas, que actúan como hormonas y como neurotransmisores en varios tejidos del cuerpo y permiten un aumento del metabolismo que eleva los valores de glucosa y el oxígeno disponible. Existe una relación fisiológica de dependencia entre las catecolaminas y la producción de lactato que predispone al organismo para responder de forma efectiva ante una situación de estrés. Sin embargo, en tejidos sensibles, la respuesta adrenérgica exacerbada puede ocasionar efectos exagerados que pueden incrementar la probabilidad de fallo. En base al conocimiento de estos mecanismos, se plantean estrategias terapéuticas enfocadas en regular la actividad simpática.

ABSTRACT Lactate is a highly dynamic metabolite that is produced, under anaerobic conditions, due to hypoxia or ischemia. Under aerobic conditions, it is synthesized by a mechanism driven by the stimulation of the β2 adrenergic receptor, which increases the activity of the sodium-potassium pump, and by a state of accelerated aerobic glycolysis. This metabolite is capable of being exchanged between different producing and consuming cells, ensuring the raw material for energy production. The sympathetic nervous system responds to stress stimuli through the release of catecholamines, which act as hormones and neurotransmitters in various tissues of the body, allowing an increase in metabolism that raises glucose and available oxygen levels. There is a physiological dependence between catecholamine levels and lactate production, predisposing the body to respond effectively to a stressful situation. However, an exacerbated adrenergic response may cause exaggerated effects on sensitive tissues that increase the probability of failure. Based on the knowledge of these mechanisms, therapeutic strategies focused on regulating the sympathetic activity are proposed.

H-ferritin expression in astrocytes is necessary for proper oligodendrocyte development and myelination.

How iron is delivered to the CNS for myelination is poorly understood. Astrocytes are the most abundant glial cells in the brain and are the only cells in close contact with blood vessels. Therefore, they are strategically located to obtain nutrients, such as iron, from circulating blood. To determine the importance of astrocyte iron uptake and storage in myelination and remyelination, we conditionally knocked-out the expression of the divalent metal transporter 1 (DMT1), the transferrin receptor 1 (Tfr1), and the ferritin heavy subunit (Fth) in Glast-1-positive astrocytes. DMT1 or Tfr1 ablation in astrocytes throughout early brain development did not significantly affects oligodendrocyte maturation or iron homeostasis. However, blocking Fth production in astrocytes during the first postnatal week drastically delayed oligodendrocyte development and myelin synthesis. Fth knockout animals presented an important decrease in the number of myelinating oligodendrocytes and a substantial reduction in the percentage of myelinated axons. This postnatal hypomyelination was accompanied by a decline in oligodendrocyte iron uptake and with an increase in brain oxidative stress. We also tested the relevance of astrocytic Fth expression in the cuprizone model of myelin damage and repair. Fth deletion in Glast1-positive astrocytes significantly reduced myelin production and the density of mature myelinating oligodendrocytes throughout the complete remyelination process. These results indicate that Fth iron storage in astrocytes is vital for early oligodendrocyte development as well as for the remyelination of the CNS.

Calcineurin Activity Is Increased in Charcot-Marie-Tooth 1B Demyelinating Neuropathy.

Schwann cells produce a considerable amount of lipids and proteins to form myelin in the PNS. For this reason, the quality control of myelin proteins is crucial to ensure proper myelin synthesis. Deletion of serine 63 from P0 (P0S63del) protein in myelin forming Schwann cells causes Charcot-Marie-Tooth type 1B neuropathy in humans and mice. Misfolded P0S63del accumulates in the ER of Schwann cells where it elicits the unfolded protein response (UPR). PERK is the UPR transducer that attenuates global translation and reduces ER stress by phosphorylating the translation initiation factor eIF2alpha. Paradoxically, Perk ablation in P0S63del Schwann cells (S63del/PerkSCKO ) reduced the level of P-eIF2alpha, leaving UPR markers upregulated, yet unexpectedly improved S63del myelin defects in vivo We therefore investigated the hypothesis that PERK may interfere with signals outside of the UPR and specifically with calcineurin/NFATc4 pro-myelinating pathway. Using mouse genetics including females and males in our experimental setting, we show that PERK and calcineurin interact in P0S63del nerves and that calcineurin activity and NFATc4 nuclear localization are increased in S63del Schwann cells, without altering EGR2/KROX20 expression. Moreover, genetic manipulation of the calcineurin subunits appears to be either protective or toxic in S63del in a context-dependent manner, suggesting that Schwann cells are highly sensitive to alterations of calcineurin activity.SIGNIFICANCE STATEMENT Our work shows a novel activity and function for calcineurin in Schwann cells in the context of ER stress. Schwann cells expressing the S63del mutation in P0 protein induce the unfolded protein response and upregulate calcineurin activity. Calcineurin interacts with the ER stress transducer PERK, but the relationship between the UPR and calcineurin in Schwann cells is unclear. Here we propose a protective role for calcineurin in S63del neuropathy, although Schwann cells appear to be very sensitive to its regulation. The paper uncovers a new important role for calcineurin in a demyelinating diseases.

Un plan protocolizado de rehabilitación domiciliaria tuvo mejores resultados que el tratamiento habitual en pacientes operados de prótesis total de rodilla: cohorte prospectiva / A protocolized home rehabilitation program had better outcomes than the usual care following total knee replacement: a prospective cohort study

Objetivo: comparar los resultados funcionales y de calidad de vida, y algunos indicadores de calidad y satisfacción, entre dos estrategias de cuidados posoperatorios de prótesis total de rodilla: 1) Cuidados protocolizados brindados por la Unidad de Rehabilitación del Hospital Italiano (URED) para pacientes que residen en CABA; 2) Cuidados habituales brindados por el sistema tercerizado de rehabilitación kinésica. Materiales y métodos: cohorte prospectiva de pacientes que fueron sometidos a una cirugía de reemplazo articular de la rodilla en el Hospital Italiano. Fueron evaluados mediante cuestionarios de funcionalidad y calidad de vida percibida, y goniometría, a los 45 días, por kinesiólogos entrenados. Resultados: se incluyeron 81 pacientes en el grupo de cuidados protocolizados y 28 en el de cuidados habituales. Se observaron diferencias estadísticamente significativas en todas las variables evaluadas y destacamos la relevancia clínica de que solamente el 2,43% de los pacientes atendidos en la URED continuaban usando andador a los 45 días frente al 35,71% de los que habían sido atendidos con los cuidados habituales (p = 0,004), así como la menor proporción de pacientes con déficit de flexión (2,47% vs. 46%, respectivamente; p < 0,001) y de extensión (18,52 vs. 75%; p < 0,001) en el mismo lapso, requisitos que son importantes para lograr una marcha funcional. Conclusión: un programa de rehabilitación domiciliaria protocolizada y supervisada por kinesiólogos entrenados mostró ser eficaz para una progresión más rápida hacia una marcha independiente con un menor riesgo de déficit de flexión o de extensión a los 45 días. (AU)

Objective: to compare functionality and quality of life, and some indicators of patient satisfaction, between two postoperative rehabilitation care following total knee replacement: 1) Protocolized care provided by the Italian Hospital Rehabilitation Unit for patients who live in CABA; 2) Usual care provided by the outsourced rehabilitation system. Materials and methods: prospective cohort of patients who underwent total knee replacement at the Italian Hospital were evaluated using questionnaires of functionality and quality of life at 45 days. Results: 81 patients were included in the protocolized care group and 28 in the usual care group. Statistically significant differences were observed in all the variables evaluated, highlighting clinical relevance that only 2.43% of the patients treated by the URED continued using the walker at 45 days vs 35.71% of those who had been treated with the usual care (p = 0.004); as well as the lower proportion of patients with flexion deficit (2.47 vs. 46%, respectively; p < 0.001) and extension (18.52 vs. 75%; p < 0.001) at the same time. Conclusion: a home protocolarized rehabilitation program supervised by a physical therapist proved to be effective for a quicker progression to an independent walk with lower risks of flexion or extension deficits at 45 days. (AU)

Impaired Postnatal Myelination in a Conditional Knockout Mouse for the Ferritin Heavy Chain in Oligodendroglial Cells.

To define the importance of iron storage in oligodendrocyte development and function, the ferritin heavy subunit (Fth) was specifically deleted in oligodendroglial cells. Blocking Fth synthesis in Sox10 or NG2-positive oligodendrocytes during the first or the third postnatal week significantly reduces oligodendrocyte iron storage and maturation. The brain of Fth KO animals presented an important decrease in the expression of myelin proteins and a substantial reduction in the percentage of myelinated axons. This hypomyelination was accompanied by a decline in the number of myelinating oligodendrocytes and with a reduction in proliferating oligodendrocyte progenitor cells (OPCs). Importantly, deleting Fth in Sox10-positive oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte quantities. We also tested the capacity of Fth-deficient OPCs to remyelinate the adult brain in the cuprizone model of myelin injury and repair. Fth deletion in NG2-positive OPCs significantly reduces the number of mature oligodendrocytes and myelin production throughout the remyelination process. Furthermore, the corpus callosum of Fth KO animals presented a significant decrease in the percentage of remyelinated axons and a substantial reduction in the average myelin thickness. These results indicate that Fth synthesis during the first three postnatal weeks is important for an appropriate oligodendrocyte development, and suggest that Fth iron storage in adult OPCs is also essential for an effective remyelination of the mouse brain.SIGNIFICANCE STATEMENT To define the importance of iron storage in oligodendrocyte function, we have deleted the ferritin heavy chain (Fth) specifically in the oligodendrocyte lineage. Fth ablation in oligodendroglial cells throughout early postnatal development significantly reduces oligodendrocyte maturation and myelination. In contrast, deletion of Fth in oligodendroglial cells after postnatal day 60 has no effect on myelin production and/or oligodendrocyte numbers. We have also tested the consequences of disrupting Fth iron storage in oligodendrocyte progenitor cells (OPCs) after demyelination. We have found that Fth deletion in NG2-positive OPCs significantly delays the remyelination process in the adult brain. Therefore, Fth iron storage is essential for early oligodendrocyte development as well as for OPC maturation in the demyelinated adult brain.

Iron Metabolism in Oligodendrocytes and Astrocytes, Implications for Myelination and Remyelination.

Iron is a key nutrient for normal central nervous system (CNS) development and function; thus, iron deficiency as well as iron excess may result in harmful effects in the CNS. Oligodendrocytes and astrocytes are crucial players in brain iron equilibrium. However, the mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes during CNS development or under pathological situations such as demyelination are not completely understood. In the CNS, iron is directly required for myelin production as a cofactor for enzymes involved in ATP, cholesterol and lipid synthesis, and oligodendrocytes are the cells with the highest iron levels in the brain which is linked to their elevated metabolic needs associated with the process of myelination. Unlike oligodendrocytes, astrocytes do not have a high metabolic requirement for iron. However, these cells are in close contact with blood vessel and have a strong iron transport capacity. In several pathological situations, changes in iron homoeostasis result in altered cellular iron distribution and accumulation and oxidative stress. In inflammatory demyelinating diseases such as multiple sclerosis, reactive astrocytes accumulate iron and upregulate iron efflux and influx molecules, which suggest that they are outfitted to take up and safely recycle iron. In this review, we will discuss the participation of oligodendrocytes and astrocytes in CNS iron homeostasis. Understanding the molecular mechanisms of iron uptake, storage, and efflux in oligodendrocytes and astrocytes is necessary for planning effective strategies for iron management during CNS development as well as for the treatment of demyelinating diseases.

Volumen plaquetario medio como predictor de la mortalidad en pacientes con sepsis: revisión sistemática y metanálisis / Mean platelet volume as a predictor of mortality in patients with sepsis: systematic review and meta-analysis

Introducción: El volumen medio plaquetario (VMP) es un biomarcador utilizado en el abordaje integral de la sepsis. Objetivo: Evaluar la asociación entre VMP con la mortalidad en pacientes con sepsis. Métodos: Se realizó una revisión sistemática de estudios observacionales en cinco bases de datos. Se analizó la mortalidad asociada con la sepsis; las intervenciones consideradas fueron VMP, APACHE y lactato sérico. Resultados: Respecto a la mortalidad asociada a sepsis, se encontró un valor significativo en la VMP a las 72 horas (200 fallecidos versus 654 no fallecidos; MD 0.83 IC95% 0.53-1.13, p=< 0.0001, I2 =72.9%); así como el valor de APACHE II (220 muertos frente a 604 no fallecidos; MD 0.81 IC95% 0.62-1.0, p= 0.0001, I2 =32%). No se encontró significancia estadística para las demás variables clínicas. Conclusiones: El aumento de la VMP se asocia con mayor riesgo de mortalidad en pacientes con sepsis, especialmente después de 72 horas de evolución de las características clínicas.

Introduction: Platelet mean volume (MVP) is a biomarker used in the integral approach to sepsis. Objective: To assess the association between MVP and mortality in patients with sepsis. Methods: A systematic review of observational studies in five databases was performed. Mortality associated with sepsis was analysed; interventions considered were MPV, APACHE and serum lactate. Results: Regarding mortality associated with sepsis, a significant value was found in the MVP at 72 hours (200 deceased versus 654 not deceased; MD 0.83 IC95% 0.53-1.13, p=<0.0001, I2 =72.9%); as well as the value of APACHE II (220 dead versus 604 not deceased; MD 0.81 IC95% 0.62-1.0, p= 0.0001, I2 =32%). No statistical significance was found for the other clinical variables. Conclusions: Increased MVP is associated with increased risk of mortality in patients with sepsis, especially after 72 hours of evolution of clinical features.

Deletion of Voltage-Gated Calcium Channels in Astrocytes during Demyelination Reduces Brain Inflammation and Promotes Myelin Regeneration in Mice.

To determine whether Cav1.2 voltage-gated Ca2+ channels contribute to astrocyte activation, we generated an inducible conditional knock-out mouse in which the Cav1.2 α subunit was deleted in GFAP-positive astrocytes. This astrocytic Cav1.2 knock-out mouse was tested in the cuprizone model of myelin injury and repair which causes astrocyte and microglia activation in the absence of a lymphocytic response. Deletion of Cav1.2 channels in GFAP-positive astrocytes during cuprizone-induced demyelination leads to a significant reduction in the degree of astrocyte and microglia activation and proliferation in mice of either sex. Concomitantly, the production of proinflammatory factors such as TNFα, IL1ß and TGFß1 was significantly decreased in the corpus callosum and cortex of Cav1.2 knock-out mice through demyelination. Furthermore, this mild inflammatory environment promotes oligodendrocyte progenitor cells maturation and myelin regeneration across the remyelination phase of the cuprizone model. Similar results were found in animals treated with nimodipine, a Cav1.2 Ca2+ channel inhibitor with high affinity to the CNS. Mice of either sex injected with nimodipine during the demyelination stage of the cuprizone treatment displayed a reduced number of reactive astrocytes and showed a faster and more efficient brain remyelination. Together, these results indicate that Cav1.2 Ca2+ channels play a crucial role in the induction and proliferation of reactive astrocytes during demyelination; and that attenuation of astrocytic voltage-gated Ca2+ influx may be an effective therapy to reduce brain inflammation and promote myelin recovery in demyelinating diseases.SIGNIFICANCE STATEMENT Reducing voltage-gated Ca2+ influx in astrocytes during brain demyelination significantly attenuates brain inflammation and astrocyte reactivity. Furthermore, these changes promote myelin restoration and oligodendrocyte maturation throughout remyelination.

Calcium Signaling in the Oligodendrocyte Lineage: Regulators and Consequences.

Cells of the oligodendrocyte lineage express a wide range of Ca2+ channels and receptors that regulate oligodendrocyte progenitor cell (OPC) and oligodendrocyte formation and function. Here we define those key channels and receptors that regulate Ca2+ signaling and OPC development and myelination. We then discuss how the regulation of intracellular Ca2+ in turn affects OPC and oligodendrocyte biology in the healthy nervous system and under pathological conditions. Activation of Ca2+ channels and receptors in OPCs and oligodendrocytes by neurotransmitters converges on regulating intracellular Ca2+, making Ca2+ signaling a central candidate mediator of activity-driven myelination. Indeed, recent evidence indicates that localized changes in Ca2+ in oligodendrocytes can regulate the formation and remodeling of myelin sheaths and perhaps additional functions of oligodendrocytes and OPCs. Thus, decoding how OPCs and myelinating oligodendrocytes integrate and process Ca2+ signals will be important to fully understand central nervous system formation, health, and function.

Hormonas sexuales en la enfermedad crítica / Sexual hormones in critical disease

INTRODUCCIÓN. En el paciente crítico ha existido un conglomerado de situaciones dadas por alteración de las hormonas acorde al comportamiento del eje hipotalámi-co-hipofisario- gonadal, entender su rol es fundamental. OBJETIVO. Describir las alteraciones de las hormonas sexuales en el paciente críticamente enfermo desde un enfoque fisiológico y clínico. MATERIALES Y MÉTODOS. Estudio observacional, de revisión bibliográfica y análisis sistemático de 84 artículos científicos y selección de muestra de 27 en MedLine, The Cochrane Library Plus, LILACS y Web of Science; en español e inglés y variables: hormonas esteroides gonadales, enfermedad crítica, endocrinología, estrés, gónadas y disfunción, periodo 1998-2017. CONCLUSIÓN. Las alteraciones detectadas fueron un mecanismo para la producción de hormonas esteroideas hacia la síntesis predominante de cortisol y soportar el alto estrés meta-bólico de los pacientes. Las citocinas pro inflamatorias fueron importantes en éstos cambios. La polifarmacia fue un factor adicional poco ponderado de la alteración endocrina sexual.

INTRODUCTION. In the critical patient there has been a conglomerate of situations given by alteration of the hormones according to the behavior of the hypothalamic-pi-tuitary-gonadal axis, understanding their role is fundamental. OBJECTIVE. Describe the alterations of sex hormones in the critically ill patient from a physiological and clinical approach.MATERIALS AND METHODS.Observational, literature review and systematic analysis of 84 scientific articles and sample selection of 27 in MedLine, The Cochrane Library Plus, LILACS and Web of Science; in Spanish and English and variables: gonadal steroid hormones, critical illness, endocrinology, stress, gonads and dysfunction, period 1998-2017. CONCLUSION. The alterations detected were a mechanism for the production of steroid hormones towards the predominant syn-thesis of cortisol and withstand the high metabolic stress of the patients. Pro inflam-matory cytokines were important in these changes. Polypharmacy was an additional unweighted factor of sexual endocrine disruption.

Iron Metabolism in the Peripheral Nervous System: The Role of DMT1, Ferritin, and Transferrin Receptor in Schwann Cell Maturation and Myelination.

Iron is an essential cofactor for many cellular enzymes involved in myelin synthesis, and iron homeostasis unbalance is a central component of peripheral neuropathies. However, iron absorption and management in the PNS are poorly understood. To study iron metabolism in Schwann cells (SCs), we have created 3 inducible conditional KO mice in which three essential proteins implicated in iron uptake and storage, the divalent metal transporter 1 (DMT1), the ferritin heavy chain (Fth), and the transferrin receptor 1 (Tfr1), were postnatally ablated specifically in SCs. Deleting DMT1, Fth, or Tfr1 in vitro significantly reduce SC proliferation, maturation, and the myelination of DRG axons. This was accompanied by an important reduction in iron incorporation and storage. When these proteins were KO in vivo during the first postnatal week, the sciatic nerve of all 3 conditional KO animals displayed a significant reduction in the synthesis of myelin proteins and in the percentage of myelinated axons. Knocking out Fth produced the most severe phenotype, followed by DMT1 and, last, Tfr1. Importantly, DMT1 as well as Fth KO mice showed substantial motor coordination deficits. In contrast, deleting these proteins in mature myelinating SCs results in milder phenotypes characterized by small reductions in the percentage of myelinated axons and minor changes in the g-ratio of myelinated axons. These results indicate that DMT1, Fth, and Tfr1 are critical proteins for early postnatal iron uptake and storage in SCs and, as a consequence, for the normal myelination of the PNS.SIGNIFICANCE STATEMENT To determine the function of the divalent metal transporter 1, the transferrin receptor 1, and the ferritin heavy chain in Schwann cell (SC) maturation and myelination, we created 3 conditional KO mice in which these proteins were postnatally deleted in Sox10-positive SCs. We have established that these proteins are necessary for normal SC iron incorporation and storage, and, as a consequence, for an effective myelination of the PNS. Since iron is indispensable for SC maturation, understanding iron metabolism in SCs is an essential prerequisite for developing therapies for demyelinating diseases in the PNS.

Revisión Bibliográfica: Glicocálix Endotelial como Blanco de Agresión del Fenómeno Isquemia Reperfusión / Bibliographic Review: Endothelial Glycocalyx as Target of Aggression of the Ischemia-Reperfusion Injury

El glicocálix endotelial es una estructura rica en glucosaminoglicanos, proteoglicanos y glucoproteínas que recubre el endotelio vascular; además de ser una estructura de protección, al estar en contacto directo con la sangre se convierte en el blanco de agresión de diversos mecanismos fisiopatológicos. El fenómeno isquemia-reperfusión se presenta comúnmente en varias entidades del paciente crítico, incluyendo: eventos cerebro vasculares isquémicos, síndrome coronario agudo, sepsis y choque en sus distintos tipos, traumatismos mayores, cirugía y trasplante. Las complicaciones derivadas de este fenómeno son múltiples y dependientes del sitio de presentación; el común denominador es la disfunción microvascular que potencialmente podría desencadenar un fallo multisistémico. El objetivo de esta revisión bibliográfica fue realizar una actualización de los conocimientos en relación a la injuria del glicocálix endotelial durante el fenómeno isquemia-reperfusión.(au)

The endothelial glycocalyx is a structure rich in glycosaminoglycans, proteoglycans and glycoproteins that cover vascular endothelium; in addition of being a protective structure, the direct contact with blood turns it the target of aggression of multiple physiopathological mechanisms. The ischemia-reperfusion injury commonly presents in several critical care entities, including: ischemic stroke, acute coronary syndrome, sepsis and shock, major trauma, surgery and transplantation. Complications are multiple and dependent of the site of presentation; the common denominator is microvascular dysfunction that could potentially trigger multiple organ dysfunction syndrome. The aim of this bibliographic review was to update the knowledge regarding endothelial glycocalyx damage and ischemia-reperfusion injury.(au)

The Divalent Metal Transporter 1 (DMT1) Is Required for Iron Uptake and Normal Development of Oligodendrocyte Progenitor Cells.

The divalent metal transporter 1 (DMT1) is a multimetal transporter with a primary role in iron transport. Although DMT1 has been described previously in the CNS, nothing was known about the role of this metal transporter in oligodendrocyte maturation and myelination. To determine whether DMT1 is required for oligodendrocyte progenitor cell (OPC) maturation, we used siRNAs and the Cre-lox system to knock down/knock out DMT1 expression in vitro as well as in vivo Blocking DMT1 synthesis in primary cultures of OPCs reduced oligodendrocyte iron uptake and significantly delayed OPC development. In vivo, a significant hypomyelination was found in DMT1 conditional knock-out mice in which DMT1 was postnatally deleted in NG2- or Sox10-positive OPCs. The brain of DMT1 knock-out animals presented a decrease in the expression levels of myelin proteins and a substantial reduction in the percentage of myelinated axons. This reduced postnatal myelination was accompanied by a decrease in the number of myelinating oligodendrocytes and a rise in proliferating OPCs. Furthermore, using the cuprizone model of demyelination, we established that DMT1 deletion in NG2-positive OPCs lead to less efficient remyelination of the adult brain. These results indicate that DMT1 is vital for OPC maturation and for the normal myelination of the mouse brain.SIGNIFICANCE STATEMENT To determine whether divalent metal transporter 1 (DMT1), a multimetal transporter with a primary role in iron transport, is essential for oligodendrocyte development, we created two conditional knock-out mice in which DMT1 was postnatally deleted in NG2- or Sox10-positive oligodendrocyte progenitor cells (OPCs). We have established that DMT1 is necessary for normal OPC maturation and is required for an efficient remyelination of the adult brain. Since iron accumulation by OPCs is indispensable for myelination, understanding the iron incorporation mechanism as well as the molecules involved is critical to design new therapeutic approaches to intervene in diseases in which the myelin sheath is damaged or lost.

Enhanced oligodendrocyte maturation and myelination in a mouse model of Timothy syndrome.

To study the role of L-type voltage-gated Ca++ channels in oligodendrocyte development, we used a mouse model of Timothy syndrome (TS) in which a gain-of-function mutation in the α1 subunit of the L-type Ca++ channel Cav1.2 gives rise to an autism spectrum disorder (ASD). Oligodendrocyte progenitor cells (OPCs) isolated from the cortex of TS mice showed greater L-type Ca++ influx and displayed characteristics suggestive of advanced maturation compared to control OPCs, including a more complex morphology and higher levels of myelin protein expression. Consistent with this, expression of Cav1.2 channels bearing the TS mutation in wild-type OPCs triggered process formation and promoted oligodendrocyte-neuron interaction via the activation of Ca++ /calmodulin-dependent protein kinase II. To ascertain whether accelerated OPC maturation correlated with functional enhancements, we examined myelination in the TS brain at different postnatal time points. The expression of myelin proteins was significantly higher in the corpus callosum, cortex and striatum of TS animals, and immunohistochemical analysis for oligodendrocyte stage-specific markers revealed an increase in the density of myelinating oligodendrocytes in several areas of the TS brain. Along the same line, electron microscopy studies in the corpus callosum of TS animals showed significant increases both in the percentage of myelinated axons and in the thickness of myelin sheaths. In summary, these data indicate that OPC development and oligodendrocyte myelination is enhanced in the brain of TS mice, and suggest that this mouse model of a syndromic ASD is a useful tool to explore the role of L-type Ca++ channels in myelination.

Muscarinic Receptor M3R Signaling Prevents Efficient Remyelination by Human and Mouse Oligodendrocyte Progenitor Cells.

Muscarinic receptor antagonists act as potent inducers of oligodendrocyte differentiation and accelerate remyelination. However, the use of muscarinic antagonists in the clinic is limited by poor understanding of the operant receptor subtype, and questions regarding possible species differences between rodents and humans. Based on high selective expression in human oligodendrocyte progenitor cells (OPCs), we hypothesized that M3R is the functionally relevant receptor. Lentiviral M3R knockdown in human primary CD140a/PDGFαR+ OPCs resulted in enhanced differentiation in vitro and substantially reduced the calcium response following muscarinic agonist treatment. Importantly, following transplantation in hypomyelinating shiverer/rag2 mice, M3R knockdown improved remyelination by human OPCs. Furthermore, conditional M3R ablation in adult NG2-expressing OPCs increased oligodendrocyte differentiation and led to improved spontaneous remyelination in mice. Together, we demonstrate that M3R receptor mediates muscarinic signaling in human OPCs that act to delay differentiation and remyelination, suggesting that M3 receptors are viable targets for human demyelinating disease.SIGNIFICANCE STATEMENT The identification of drug targets aimed at improving remyelination in patients with demyelination disease is a key step in development of effective regenerative therapies to treat diseases, such as multiple sclerosis. Muscarinic receptor antagonists have been identified as effective potentiators of remyelination, but the receptor subtypes that mediate these receptors are unclear. In this study, we show that genetic M3R ablation in both mouse and human cells results in improved remyelination and is mediated by acceleration of oligodendrocyte commitment from oligodendrocyte progenitor cells. Therefore, M3R represents an attractive target for induced remyelination in human disease.