Neuroinflammation after traumatic injury to the developing brain

PURPOSES: Mechanical trauma to the developing rodent brain induces a diffuse secondary neuroapoptosis associated with infiltration of immune cells, local and systemic increased levels of proinflammatory mediators. Our aim was to study their expression, cellular localization, distribution pattern and time course in various brain regions. MATERIALS AND METHODS: 7-day-old Wistar rats and C57/BL6 mice were subjected to cortical trauma. Animals were sacrificed at defined time points - from 2 h to 14 days following trauma. Brain tissues were processed for molecular analyses, single or double indirect peroxidase/fluorescence immunohistochemistry for apoptotic cell death, microglia and interleukin (IL)-1ß/IL-18. RESULTS: Apoptotic neuronal cell death detected by TUNEL was found at distant regions to trauma site mainly ipsilateral from 6 h to 5 days later. A substantial activation of ED1+ microglia occurred at the site of primary and secondary damages. It was first evident at 12 h, peaked at 36-48 h and decreased significantly after 5 days. A marked increase of mRNA, protein levels and imunohistochemical expression of two pro-inflammatory cytokines, interleukin (IL)-1ß and IL-18, was found from 2 h to 5 days following trauma. Mice deficient in IL-18 (IL-18−/−) were protected against post-traumatic brain damage. CONCLUSIONS: Brain trauma leads to neuroinflammation expressed by microglial activation and an increase in IL-1ß and IL-18. Activated microglia are one of the main cellular sources of elevated levels for both cytokines. They are probably involved in and help sustain apoptotic neurodegeneration over several days after trauma. This finding might define microglia and IL-1ß/IL-18 as potential post-traumatic therapeutic targets

Suppression of the intrinsic apoptosis pathway by sinaptic activity

Synaptic activity promotes resistance to diverse apoptotic insults, the mechanism behind which is incompletely understood. We show here that a coordinated downregulation of core components of the intrinsic apoptosis pathway by neuronal activity forms a key part of the underlying mechanism. Activity-dependent protection against apoptotic insults is associated with inhibition of cytochrome c release in most but not all neurons, indicative of anti-apoptotic signaling both upstream and downstream of this step. We find that enhanced firing activity suppresses expression of the proapoptotic BH3-only member gene Puma in a NMDA receptor-dependent, p53-independent manner. Puma expression is sufficient to induce cytochrome c loss and neuronal apoptosis. Puma deficiency protects neurons against apoptosis and also occludes the protective effect of synaptic activity, while blockade of physiological NMDA receptor activity in the developing mouse brain induces neuronal apoptosis that is preceded by upregulation of Puma. However, enhanced activity can also confer resistance to Puma-induced apoptosis, acting downstream of cytochrome c release. This mechanism is mediated by transcriptional suppression of apoptosome components Apaf-1 and procaspase-9, and limiting caspase-9 activity, since overexpression of procaspase-9 accelerates the rate of apoptosis in active neurons back to control levels. Synaptic activity does not exert further significant anti-apoptotic effects downstream of caspase-9 activation, since an inducible form of caspase-9 overrides the protective effect of synaptic activity, despite activity-induced transcriptional suppression of caspase-3. Thus, suppression of apoptotic gene expression may synergize with other activity-dependent events such as enhancement of antioxidant defenses to promote neuronal survival

Toxicity of Tungsten Carbide and Cobalt-Doped Tungsten Carbide Nanoparticles in Mammalian Cells in Vitro

BACKGROUND: Tungsten carbide nanoparticles are being explored for their use in the manufacture of hard metals. To develop nanoparticles for broad applications, potential risks to human health and the environment should be evaluated and taken into consideration. OBJECTIVE: We aimed to assess the toxicity of well-characterized tungsten carbide (WC) and cobalt-doped tungsten carbide (WC-Co) nanoparticle suspensions in an array of mammalian cells. METHODS: We examined acute toxicity of WC and of WC-Co (10% weight content Co) nanoparticles in different human cell lines (lung, skin, and colon) as well as in rat neuronal and glial cells (i.e., primary neuronal and astroglial cultures and the oligodendrocyte precursor cell line OLN-93). Furthermore, using electron microscopy, we assessed whether natioparticles can be taken up by living cells. We chose these in vitro systems in order to evaluate for potential toxicity of the nanoparticles in different mammalian organs (i.e., lung, skin, intestine, and brain). RESULTS: Chemical-physical characterization confirmed that WC as well as WC-Co natioparticles with a mean particle size of 145 nm form stable suspensions in serum-containing cell culture media. WC nanoparticles were not acutely toxic to the studied cell lines. However, cytotoxicity became apparent when particles were doped with Co. The most sensitive were astrocytes and colon epithelial cells. Cytotoxicity of WC-Co nanoparticles was higher than expected based on the ionic Co content of the particles. Analysis by electron microscopy demonstrated presence of WC nanoparticles within mammalian cells. CONCLUSIONS: Our findings demonstrate that doping of WC nanoparticles with Co markedly increases their cytotoxic effect and that the presence of WC-Co in particulate form is essential to elicit this combinatorial effect

Expanding the phenotypic spectrum of lupus erythematosus in Aicardi-Goutie`res syndrome

Objective. Aicardi-Goutie`res syndrome (AGS) isan early-onset encephalopathy resembling congenitalviral infection that is characterized by basal gangliacalcifications, loss of white matter, cerebrospinal fluid(CSF) lymphocytosis, and elevated interferon- levels inthe CSF. Studies have shown that AGS is an autosomalrecessivedisease linked to mutations in 5 genes, encodingthe 3 -repair DNA exonuclease 1 (TREX1), the 3subunits of ribonuclease H2 (RNASEH2A–C), and sterilealpha motif domain and HD domain–containingprotein 1 (SAMHD1). In this study we further characterizedthe phenotypic spectrum of this disease.Methods. Clinical and laboratory data were obtainedfrom 26 patients fulfilling the clinical diagnosticcriteria for AGS. Genomic DNA was screened for mutationsin all 5 AGS genes by direct sequencing, and serawere analyzed for autoantibodies.Results. In 20 patients with AGS, 20 mutations,12 of which were novel, were identified in all 5 AGSgenes. Clinical and laboratory investigations revealed ahigh prevalence of features (some not previously describedin patients with AGS) that are commonly seen inpatients with systemic lupus erythematosus (SLE), suchas thrombocytopenia, leukocytopenia, antinuclear antibodies,erythematous lesions, oral ulcers, and arthritis,which were observed in 12 (60%) of 20 patients withAGS. Moreover, the coexistence of AGS and SLE, wasfor the first time, demonstrated in 2 patients withmolecularly proven AGS.Conclusion. These findings expand the phenotypicspectrum of lupus erythematosus in AGS andprovide further insight into its disease mechanisms by showing that activation of the innate immune system asa result of inherited defects in nucleic acid metabolismcould lead to systemic autoimmunity

Synaptic NMDA receptor activity boosts intrinsic antioxidant defenses

Intrinsic antioxidant defenses are important for neuronal longevity. We found that in rat neurons, synaptic activity, acting via NMDA receptor (NMDAR) signaling, boosted antioxidant defenses by making changes to the thioredoxin-peroxiredoxin (Prx) system. Synaptic activity enhanced thioredoxin activity, facilitated the reduction of overoxidized Prxs and promoted resistance to oxidative stress. Resistance was mediated by coordinated transcriptional changes; synaptic NMDAR activity inactivated a previously unknown Forkhead box O target gene, the thioredoxin inhibitor Txnip. Conversely, NMDAR blockade upregulated Txnip in vivo and in vitro, where it bound thioredoxin and promoted vulnerability to oxidative damage. Synaptic activity also upregulated the Prx reactivating genes Sesn2 (sestrin 2) and Srxn1 (sulfiredoxin), via C/EBPβ and AP-1, respectively. Mimicking these expression changes was sufficient to strengthen antioxidant defenses. Trans-synaptic stimulation of synaptic NMDARs was crucial for boosting antioxidant defenses; chronic bath activation of all (synaptic and extrasynaptic) NMDARs induced no antioxidative effects. Thus, synaptic NMDAR activity may influence the progression of pathological processes associated with oxidative damage

Cerebrospinal Fluid Biomarkers in Childhood Leukemias

Involvement of the central nervous system (CNS) in childhood leukemias remains a major cause of treatment failures. Analysis of the cerebrospinal fluid constitutes the most important diagnostic pillar in the detection of CNS leukemia and relies primarily on cytological and flow-cytometry studies. With increasing survival rates, it has become clear that treatments for pediatric leukemias pose a toll on the developing brain, as they may cause acute toxicities and persistent neurocognitive deficits. Preclinical research has demonstrated that established and newer therapies can injure and even destroy neuronal and glial cells in the brain. Both passive and active cell death forms can result from DNA damage, oxidative stress, cytokine release, and acceleration of cell aging. In addition, chemotherapy agents may impair neurogenesis as well as the function, formation, and plasticity of synapses. Clinical studies show that neurocognitive toxicity of chemotherapy is greatest in younger children. This raises concerns that, in addition to injury, chemotherapy may also disrupt crucial developmental events resulting in impairment of the formation and efficiency of neuronal networks. This review presents an overview of studies demonstrating that cerebrospinal fluid biomarkers can be utilized in tracing both CNS disease and neurotoxicity of administered treatments in childhood leukemias