Transport of BMAA into Neurons and Astrocytes by System x\u3csub\u3ec\u3c/sub\u3e-

The study of the mechanism of β-N-methylamino-l-alanine (BMAA) neurotoxicity originally focused on its effects at the N-methyl-d-aspartate (NMDA) receptor. In recent years, it has become clear that its mechanism of action is more complicated. First, there are certain cell types, such as motor neurons and cholinergic neurons, where the dominate mechanism of toxicity is through action at AMPA receptors. Second, even in cortical neurons where the primary mechanism of toxicity appears to be activation of NMDA receptors, there are other mechanisms involved. We found that along with NMDA receptors, activation of mGLuR5 receptors and effects on the cystine/glutamate antiporter (system xc-) were involved in the toxicity. The effects on system xc- are of particular interest. System xc- mediates the transport of cystine into the cell in exchange for releasing glutamate into the extracellular fluid. By releasing glutamate, system xc- can potentially cause excitotoxicity. However, through providing cystine to the cell, it regulates the levels of cellular glutathione (GSH), the main endogenous intracellular antioxidant, and in this way may protect cells against oxidative stress. We have previously published that BMAA inhibits cystine uptake leading to GSH depletion and had indirect evidence that BMAA is transported into the cells by system xc-. We now present direct evidence that BMAA is transported into both astrocytes and neurons through system xc-. The fact that BMAA is transported by system xc- also provides a mechanism for BMAA to enter brain cells potentially leading to misincorporation into proteins and protein misfolding

FGF-2 Induces Neuronal Death through Upregulation of System xc-

The cystine/glutamate antiporter (system xc-) transports cystine into cell in exchange for glutamate. Fibroblast growth factor-2 (FGF-2) upregulates system xc- selectively on astrocytes, which leads to increased cystine uptake, the substrate for glutathione production, and increased glutamate release. While increased intracellular glutathione can limit oxidative stress, the increased glutamate release can potentially lead to excitotoxicity to neurons. To test this hypothesis, mixed neuronal and glial cortical cultures were treated with FGF-2. Treatment with FGF-2 for 48 h caused a significant neuronal death in these cultures. Cell death was not observed in neuronal-enriched cultures, or astrocyte-enriched cultures, suggesting the toxicity was the result of neuron-glia interaction. Blocking system xc- eliminated the neuronal death as did the AMPA/kainate receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione (NBQX), but not the NMDA receptor antagonist memantine. When cultures were exposed directly to glutamate, both NBQX and memantine blocked the neuronal toxicity. The mechanism of this altered profile of glutamate receptor mediated toxicity by FGF-2 is unclear. The selective calcium permeable AMPA receptor antagonist 1-naphthyl acetyl spermine (NASPM) failed to offer protection. The most likely explanation for the results is that 48 h FGF-2 treatment induces AMPA/kainate receptor toxicity through increased system xc- function resulting in increased release of glutamate. At the same time, FGF-2 alters the sensitivity of the neurons to glutamate toxicity in a manner that promotes selective AMPA/kainate receptor mediated toxicity

Regulation of the Cystine/Glutamate Antiporter and its Contribution to Neuronal Death

The aim of this thesis is to better understand the regulation of the cystine/glutamate antiporter (system xc-) and its role in regulating neuronal survival and death. Expressed primarily on astrocytes, system xc- takes up cystine and releases glutamate in a 1:1 ratio. Cystine uptake is the rate-limiting step in glutathione synthesis, the brain’s main antioxidant. Glutamate released into the extrasynaptic space can regulate neuronal function; however excessive glutamate release can cause excitotoxicity. The dual actions of system xc- make it of interest in many neurodegenerative diseases where oxidative stress and excitotoxicity are involved. We investigated the regulation of system xc- in SOD1-G93A transgenic mouse model of ALS. We observed an increase in cystine uptake and glutamate release through system xc- in spinal cord slices of SOD1-G93A transgenic mice. We did not observe a change in the function of the main glutamate clearance transporter, excitatory amino acid transporter (EAAT). This study was the first to show that system xc- activity is dysregulated in an ALS model and suggests that the excitotoxicity in the SOD1-G93A transgenic mouse may be due to increased system xc- activity. Using primary mixed cortical cultures we assessed how different compounds that deplete intracellular glutathione (GSH), L-buthionine-sulfoximine (BSO) and diethyl maleate (DEM), affect system xc- function. Both compounds caused significant decreases in intracellular GSH levels; however, DEM caused an increase in cystine uptake through system xc-, while unexpectedly BSO caused a decrease in uptake. Also, DEM caused a decrease in intracellular cysteine, while BSO increased cysteine levels. The results suggest that negative feedback by intracellular cysteine is a more important regulator of system xc- than intracellular GSH. Transforming growth factor-β1 (TGF-β1) is a cytokine involved in regulating many cellular processes, including neuronal survival and death. We found that TGF-β1 increased cystine uptake through system xc- in astrocyte-enriched glial cultures via the MAPK/ERK pathway. TGF-β1 increased the export of GSH from astrocytes, which suggests a neuroprotective role; however, in mixed cortical cultures TGF-β1 enhanced rotenone-induced neurotoxicity through AMPA receptors. The data suggests that the increase in system xc- activity by TGF-β1 may have antioxidant defenses, but also exacerbates excitotoxicity

Regulation of System x\u3csub\u3ec\u3c/sub\u3e\u3csup\u3e-\u3c/sup\u3e by Pharmacological Manipulation of Cellular Thiols

The cystine/glutamate exchanger (system xc-) mediates the transport of cystine into the cell in exchange for glutamate. By releasing glutamate, system xc- can potentially cause excitotoxicity. However, through providing cystine to the cell, it regulates the levels of cellular glutathione (GSH), the main endogenous intracellular antioxidant, and may protect cells against oxidative stress. We tested two different compounds that deplete primary cortical cultures containing both neurons and astrocytes of intracellular GSH, L-buthionine-sulfoximine (L-BSO), and diethyl maleate (DEM). Both compounds caused significant concentration and time dependent decreases in intracellular GSH levels. However; DEM caused an increase in radiolabeled cystine uptake through system xc- , while unexpectedly BSO caused a decrease in uptake. The compounds caused similar low levels of neurotoxicity, while only BSO caused an increase in oxidative stress. The mechanism of GSH depletion by these two compounds is different, DEM directly conjugates to GSH, while BSO inhibits γ-glutamylcysteine synthetase, a key enzyme in GSH synthesis. As would be expected from these mechanisms of action, DEM caused a decrease in intracellular cysteine, while BSO increased cysteine levels. The results suggest that negative feedback by intracellular cysteine is an important regulator of system xc- in this culture system

Pituitary Adenylate Cyclase-Activating Polypeptide Orchestrates Neuronal Regulation Of The Astrocytic Glutamate-Releasing Mechanism System x\u3csub\u3ec\u3c/sub\u3e\u3csup\u3e−\u3c/sup\u3e

Glutamate signaling is achieved by an elaborate network involving neurons and astrocytes. Hence, it is critical to better understand how neurons and astrocytes interact to coordinate the cellular regulation of glutamate signaling. In these studies, we used rat cortical cell cultures to examine whether neurons or releasable neuronal factors were capable of regulating system xc-(Sxc), a glutamate-releasing mechanism that is expressed primarily by astrocytes and has been shown to regulate synaptic transmission. We found that astrocytes cultured with neurons or exposed to neuronal-conditioned media displayed significantly higher levels of Sxc activity. Next, we demonstrated that the pituitary adenylate cyclase-activating polypeptide (PACAP) may be a neuronal factor capable of regulating astrocytes. In support, we found that PACAP expression was restricted to neurons, and that PACAP receptors were expressed in astro-cytes. Interestingly, blockade of PACAP receptors in cultures comprised of astrocytes and neurons significantly decreased Sxc activity to the level observed in purified astrocytes, whereas application of PACAP to purified astrocytes increased Sxc activity to the level observed in cultures comprised of neurons and astrocytes. Collectively, these data reveal that neurons coordinate the actions of glutamate-related mechanisms expressed by astrocytes, such as Sxc, a process that likely involves PACAP

O estado e o terceiro setor

Resumo: Partindo-se da análise das relações entre Estado e indivíduos, o presente estudo almeja demonstrar de que maneira surge e se estabelece o chamado Terceiro Setor, buscando conceituá-lo com a finalidade de aprofundar questão atual do direito brasileiro, que diz respeito às Organizações da Sociedade Civil de Interesse Público. A partir da observação da legislação pertinente ao tema, de posicionamentos doutrinários e jurisprudenciais, delineia-se o contexto em que hoje estão imersas tais entidades, revelando-se a aterradora realidade do desvio das finalidades a que as OSCIPs deveriam se prestar. Tendo em vista os desvirtuamentos constatados, que envolvem, essencialmente, a burla ao regime jurídico-administrativo e a apropriação privada de recursos públicos, recorre-se ao controle como forma de barrar o cometimento de ilicitudes e irregularidades por intermédio das parcerias do Estado com as OSCIPs. Destaca-se, ainda, a recente edição da Lei nº 12.846, a chamada "Lei Anticorrupção", que tem por objetivo a responsabilização administrativa e civil de pessoas jurídicas pela prática de atos contra a Administração Pública. Tudo com o escopo de demonstrar que, em princípio, tanto o Terceiro Setor quanto as OSCIPs são benéficos, e que o Estado deve fomentar suas atividades através de parcerias. Contudo, não é admissível que tais ajustes sejam utilizados com desígnios que não o atendimento do interesse público, devendo ser realizado o controle para que tais práticas sejam eliminadas e os responsáveis pelos desvios de finalidades sofram as sanções previstas no ordenament

Regulation of System x

The cystine/glutamate exchanger (system xc-) mediates the transport of cystine into the cell in exchange for glutamate. By releasing glutamate, system xc- can potentially cause excitotoxicity. However, through providing cystine to the cell, it regulates the levels of cellular glutathione (GSH), the main endogenous intracellular antioxidant, and may protect cells against oxidative stress. We tested two different compounds that deplete primary cortical cultures containing both neurons and astrocytes of intracellular GSH, L-buthionine-sulfoximine (L-BSO), and diethyl maleate (DEM). Both compounds caused significant concentration and time dependent decreases in intracellular GSH levels. However; DEM caused an increase in radiolabeled cystine uptake through system xc-, while unexpectedly BSO caused a decrease in uptake. The compounds caused similar low levels of neurotoxicity, while only BSO caused an increase in oxidative stress. The mechanism of GSH depletion by these two compounds is different, DEM directly conjugates to GSH, while BSO inhibits γ-glutamylcysteine synthetase, a key enzyme in GSH synthesis. As would be expected from these mechanisms of action, DEM caused a decrease in intracellular cysteine, while BSO increased cysteine levels. The results suggest that negative feedback by intracellular cysteine is an important regulator of system xc- in this culture system

Measuring routine childhood vaccination coverage in 204 countries and territories, 1980-2019 : a systematic analysis for the Global Burden of Disease Study 2020, Release 1

Background Measuring routine childhood vaccination is crucial to inform global vaccine policies and programme implementation, and to track progress towards targets set by the Global Vaccine Action Plan (GVAP) and Immunization Agenda 2030. Robust estimates of routine vaccine coverage are needed to identify past successes and persistent vulnerabilities. Drawing from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2020, Release 1, we did a systematic analysis of global, regional, and national vaccine coverage trends using a statistical framework, by vaccine and over time. Methods For this analysis we collated 55 326 country-specific, cohort-specific, year-specific, vaccine-specific, and dosespecific observations of routine childhood vaccination coverage between 1980 and 2019. Using spatiotemporal Gaussian process regression, we produced location-specific and year-specific estimates of 11 routine childhood vaccine coverage indicators for 204 countries and territories from 1980 to 2019, adjusting for biases in countryreported data and reflecting reported stockouts and supply disruptions. We analysed global and regional trends in coverage and numbers of zero-dose children (defined as those who never received a diphtheria-tetanus-pertussis [DTP] vaccine dose), progress towards GVAP targets, and the relationship between vaccine coverage and sociodemographic development. Findings By 2019, global coverage of third-dose DTP (DTP3; 81.6% [95% uncertainty interval 80.4-82 .7]) more than doubled from levels estimated in 1980 (39.9% [37.5-42.1]), as did global coverage of the first-dose measles-containing vaccine (MCV1; from 38.5% [35.4-41.3] in 1980 to 83.6% [82.3-84.8] in 2019). Third- dose polio vaccine (Pol3) coverage also increased, from 42.6% (41.4-44.1) in 1980 to 79.8% (78.4-81.1) in 2019, and global coverage of newer vaccines increased rapidly between 2000 and 2019. The global number of zero-dose children fell by nearly 75% between 1980 and 2019, from 56.8 million (52.6-60. 9) to 14.5 million (13.4-15.9). However, over the past decade, global vaccine coverage broadly plateaued; 94 countries and territories recorded decreasing DTP3 coverage since 2010. Only 11 countries and territories were estimated to have reached the national GVAP target of at least 90% coverage for all assessed vaccines in 2019. Interpretation After achieving large gains in childhood vaccine coverage worldwide, in much of the world this progress was stalled or reversed from 2010 to 2019. These findings underscore the importance of revisiting routine immunisation strategies and programmatic approaches, recentring service delivery around equity and underserved populations. Strengthening vaccine data and monitoring systems is crucial to these pursuits, now and through to 2030, to ensure that all children have access to, and can benefit from, lifesaving vaccines. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.Peer reviewe