Glutathione elevation and its protective role in acrolein-induced protein damage in synaptosomal membranes: relevance to brain lipid peroxidation in neurodegenerative disease.

Oxidative stress may be a hallmark of several neurodegenerative disorders, including Alzheimer's disease (AD) Huntington's, and Parkinson's diseases as well as amyotrophic lateral sclerosis. Acrolein is a highly reactive product of lipid peroxidation that is elevated in the brains of persons with AD. This alkenal potentially can react with proteins by Michael addition to alter their structure and function. In the present study, we used electron paramagnetic resonance in conjunction with a protein-specific spin label to monitor synaptosomal membrane protein conformational alterations induced by acrolein. A dose-dependent increased conformational alteration was observed. Consistent with this finding, protein carbonyl levels from protein-bound acrolein were significantly elevated. However, pretreatment of synaptosomes with glutathione ethyl ester (GEE) significantly ameliorated both the conformational alterations and protein carbonyls induced by acrolein. Based on this success, we tested the hypothesis that elevated levels of endogenous glutathione (GSH) would offer protection against acrolein-induced oxidative stress. In-vivo elevation of GSH (215% over control, P<0.04) was produced by i.p. injection of N-acetylcysteine (NAC), a known precursor of GSH. Synaptosomes were treated with vehicle or 2 nM acrolein, the level of this alkenal found in AD brain. In contrast to synaptosomes from control animals, which had significantly increased protein carbonyl levels following addition of 2 nM acrolein, synaptosomes that were isolated from NAC-treated rodents and treated with 2 nM acrolein showed no increased carbonyl levels compared to untreated controls. These results demonstrate protection by increased in-vivo GSH levels against acrolein-induced oxidative stress at levels found in AD brain and are consistent with the notion that methods to increase endogenous GSH levels in neurodegenerative diseases associated with oxidative stress may be promising.     

The cellular pathway of CD1e in immature and maturing dendritic cells

Dendritic cells (DCs) present antigens to T cells via CD1, HLA class I or class II molecules. During maturation, HLA class II-restricted presentation is optimized. The relocalization of CD1e from Golgi to endosomal compartments during DC maturation suggests also an optimization of the antigen-presentation pathway via CD1 molecules. We here detail the biosynthesis and cellular pathway of CD1e in immature and maturing DCs. Unlike the other CD1 molecules, CD1e was found to reach late endosomes through sorting endosomes, without passing through the plasma membrane in either immature or maturing cells. After induction of DC maturation, CD1e disappeared rapidly from the Golgi and was transiently localized in HLA-DR+ vesicles, while the number of CD1e+/CD1b+ compartments increased for at least 20 h. High-resolution light microscopy showed that, in immature DCs, CD1e+ vesicles were often in close apposition to EEA1+ or HLA-DR+ compartments, while CD1e displayed a nearly exclusive distribution in the lysosomes of mature DCs, a finding corroborated by immunoelectron microscopy. During maturation, CD1e synthesis progressively declined, while the endosomal cleavage of CD1e still occurred. Thus, CD1e displays peculiar properties, suggesting an unexpected role among the family of CD1 antigen-presenting molecules.     

fMRI in the public eye

The wide dissemination and expanding applications of functional MRI have not escaped the attention of the media or discussion in the wider public arena. From the bench to the bedside, this technology has introduced substantial ethical challenges. Are the boundaries of what it can and cannot achieve being communicated to the public? Are its limitations understood? And given the complexities that are inherent to neuroscience, are current avenues for communication adequate?     

Induction of gene mutations by 5-(2-chloroethyl)-2'-deoxyuridine (CEDU), an antiviral pyrimidine nucleoside analogue

5-(2-chloroethyl)-2'-deoxyuridine (CEDU) had been developed for the treatment of herpes simplex infections. In the Salmonella reverse mutation test, the compound was found to be mutagenic in strains TA1535 and TA102 at very high concentrations (> or =2500 micro g/plate), both with and without S9-mix. The mutagenic potential of CEDU was further investigated in vivo and in vitro. It did not induce DNA repair in rat hepatocyte primary cultures, and was negative in the micronucleus test in V79 cells and in the comet assay in human leukocytes. In vivo, CEDU was negative in the bone marrow micronucleus test in CD1 mice. The mouse spot test provided a clearly positive result. Treatment of mice on day 9 of pregnancy with 2000 mg/kg resulted in 5.9% of the F1 animals having genetically relevant spots, whereas the corresponding vehicle control group had a spot rate of 1.9%. Since these data clearly identified CEDU as an inducer of gene mutations in vivo, this potential was further investigated in lacZ transgenic Muta Mouse. Six female animals were treated daily on five consecutive days with 2000 mg/kg/day and sacrificed, after a treatment-free sampling time, 14 days later. The data showed a clear increase in the mutant frequency in the bone marrow, the lung and in the spleen. CEDU is an exception in the group of nucleoside analogues, because it was found to be a strong gene mutagen and, in contrast to the other compounds of this group investigated so far, had no considerable clastogenic effects.     

Vitamin C transporter gene (SLC23A1 and SLC23A2) polymorphisms, plasma vitamin C levels, and gastric cancer risk in the EPIC cohort

Vitamin C is known to protect mucosal tissues from oxidative stress and inhibit nitrosamine formation in the stomach. High consumption of fruits, particularly citrus, and higher circulating vitamin C concentrations may be inversely associated with gastric cancer (GC) risk. We investigated 20 polymorphisms in vitamin C transporter genes SCL23A1 and SCL23A2 and GC risk in 365 cases and 1,284 controls nested within the European Prospective Investigation into Cancer and Nutrition cohort. We also evaluated the association between these polymorphisms and baseline plasma vitamin C levels in a subset of participants. Four SNPs were predictors of plasma vitamin C levels (SLC23A1 rs11950646 and rs33972313; SLC23A2 rs6053005 and rs6133175) in multivariable linear regression models. One SNP (SLC23A2 rs6116569) was associated with GC risk, in particular non-cardia GC (OR = 1.63, 95 % CI = 1.11–2.39, based on 178 non-cardia cases), but this association was attenuated when plasma vitamin C was included in the logistic regression model. Haplotype analysis of SLC23A1 yielded no associations with GC. In SLC23A2, one haplotype was associated with both overall and non-cardia GC, another haplotype was associated with GC overall, and a third was associated with intestinal-type GC. Common variants in SLC23A1 and SLC23A2 may influence plasma vitamin C concentration independent of dietary intake, and variation in SLC23A2 may influence GC risk. Additional prospective studies in large populations and consortia are recommended. Investigation of variation in vitamin C transporter genes may shed light on the preventative properties of vitamin C in gastric carcinogenesis.     

NT-3 modulates BDNF and proBDNF levels in naïve and kindled rat hippocampus

Both mature and precursor forms of neurotrophins regulate nerve development, survival and plasticity. Brain-derived neurotrophic factor (BDNF) synthesis and secretion in turn are regulated by neuronal activity, such as epilepsy. Further, neurotrophins themselves are regulated by neurotrophin levels. Neurotrophin-3 (NT-3) and BDNF in particular can be co-expressed and each can regulate the levels of the other. This regulation is thought to be mediated through receptor tyrosine kinase (Trk) activity. It is not known whether this neurotrophin-neurotrophin interaction occurs in hippocampal tissue in vivo, or how it is influenced by neuronal activation. In this study, we explored the reciprocal influences of intraventricular infusions of NT-3 and BDNF in na?ve and kindled hippocampi of rats using Western blotting. We confirm that hippocampal kindling resulted in a significant increase in levels of BDNF both in cytochrome C (control) infused and NT-3 infused kindled rats. However, NT-3 infusion significantly reduced BDNF levels in both kindled and non-kindled hippocampi compared to their cytochrome C infused counterparts. These results are consistent with our earlier studies demonstrating lowered levels of TrkA and TrkC (NGF modulates BDNF levels via TrkA) following chronic NT-3 infusion. Although kindling led to an increase in BDNF, this was not accompanied by any detectable change in the levels of proBDNF. However, there was a significant increase in proBDNF following NT-3 infusions, suggesting NT-3 may reduce proBDNF processing. In contrast, neither NT-3 nor proNT-3 levels were affected by kindling or chronic BDNF infusions, consistent with down-regulation of TrkB by chronic BDNF infusion. Thus, modulation of BDNF by NT-3, likely mediated by Trk receptors, occurs in na?ve and kindled adult rat hippocampus.     

A structural inventory of native ribosomal ABCE1‐43S pre‐initiation complexes

In eukaryotic translation, termination and ribosome recycling phases are linked to subsequent initiation of a new round of translation by persistence of several factors at ribosomal sub‐complexes. These comprise/include the large eIF3 complex, eIF3j (Hcr1 in yeast) and the ATP‐binding cassette protein ABCE1 (Rli1 in yeast). The ATPase is mainly active as a recycling factor, but it can remain bound to the dissociated 40S subunit until formation of the next 43S pre‐initiation complexes. However, its functional role and native architectural context remains largely enigmatic. Here, we present an architectural inventory of native yeast and human ABCE1‐containing pre‐initiation complexes by cryo‐EM. We found that ABCE1 was mostly associated with early 43S, but also with later 48S phases of initiation. It adopted a novel hybrid conformation of its nucleotide‐binding domains, while interacting with the N‐terminus of eIF3j. Further, eIF3j occupied the mRNA entry channel via its ultimate C‐terminus providing a structural explanation for its antagonistic role with respect to mRNA binding. Overall, the native human samples provide a near‐complete molecular picture of the architecture and sophisticated interaction network of the 43S‐bound eIF3 complex and the eIF2 ternary complex containing the initiator tRNA.     

Transcriptomic effects of depleted uranium on acetylcholine and cholesterol metabolisms in Alzheimer's disease model

Some heavy metals, or aluminium, could participate in the development of Alzheimer disease (AD). Depleted uranium (DU), another heavy metal, modulates the cholinergic system and the cholesterol metabolism in the brain of rats, but without neurological disorders. The aim of this study was to determine what happens in organisms exposed to DU that will/are developing the AD. This study was thus performed on a transgenic mouse model for human amyloid precursor protein (APP), the Tg2576 strain. The possible effects of DU through drinking water (20 mg/L) over an 8-month period were analyzed on acetylcholine and cholesterol metabolisms at gene level in the cerebral cortex. The mRNA levels of choline acetyl transferase (ChAT) vesicular acetylcholine transporter (VAChT) and ATP-binding cassette transporter A1 (ABC A1) decreased in control Tg2576 mice in comparison with wild-type mice (respectively -89%, -86% and -44%, p < 0.05). Chronic exposure of Tg2576 mice to DU increased mRNA levels of ChAT (+189%, p < 0.05), VAChT (+120%, p < 0.05) and ABC A1 (+52%, p < 0.05) compared to control Tg2576 mice. Overall, these modifications of acetylcholine and cholesterol metabolisms did not lead to increased disturbances that are specific of AD, suggesting that chronic DU exposure did not worsen the pathology in this experimental model.