Memory deficits in APP23/Abca1+/− mice correlate with the level of Aβ oligomers

ABCA1, a member of the ATP-binding cassette family of transporters, lipidates ApoE (apolipoprotein A) and is essential for the generation of HDL (high-density lipoprotein)-like particles in the CNS (central nervous system). Lack of Abca1 increases amyloid deposition in several AD (Alzheimer's disease) mouse models. We hypothesized that deletion of only one copy of Abca1 in APP23 (where APP is amyloid precursor protein) AD model mice will aggravate memory deficits in these mice. Using the Morris Water Maze, we demonstrate that 2-year-old Abca1 heterozygous APP23 mice (referred to as APP23/het) have impaired learning during acquisition, and impaired memory retention during the probe trial when compared with age-matched wild-type mice (referred to as APP23/wt). As in our previous studies, the levels of ApoE in APP23/het mice were decreased, but the differences in the levels of Aβ and thioflavin-S-positive plaques between both groups were insignificant. Importantly, dot blot analysis demonstrated that APP23/het mice have a significantly higher level of soluble A11-positive Aβ (amyloid β protein) oligomers compared with APP23/wt which correlated negatively with cognitive performance. To confirm this finding, we performed immunohistochemistry with the A11 antibody, which revealed a significant increase of A11-positive oligomer structures in the CA1 region of hippocampi of APP23/het. This characteristic region-specific pattern of A11 staining was age-dependent and was missing in younger APP23 mice lacking Abca1. In contrast, the levels of Aβ*56, as well as other low-molecular-mass Aβ oligomers, were unchanged among the groups. Overall, the results of the present study demonstrate that in aged APP23 mice memory deficits depend on Abca1 and are likely to be mediated by the amount of Aβ oligomers deposited in the hippocampus

Opposing effects ofApoe/Apoa1double deletion on amyloid-β pathology and cognitive performance in APP mice

Producción CientíficaATP binding cassette transporter A1 (encoded by ABCA1) regulates cholesterol efflux from cells to apolipoproteins A-I and E (ApoA-I and APOE; encoded by APOA1 and APOE, respectively) and the generation of high density lipoproteins. In Abca1 knockout mice (Abca1(ko)), high density lipoproteins and ApoA-I are virtually lacking, and total APOE and APOE-containing lipoproteins in brain substantially decreased. As the ε4 allele of APOE is the major genetic risk factor for late-onset Alzheimer's disease, ABCA1 role as a modifier of APOE lipidation is of significance for this disease. Reportedly, Abca1 deficiency in mice expressing human APP accelerates amyloid deposition and behaviour deficits. We used APP/PS1dE9 mice crossed to Apoe and Apoa1 knockout mice to generate Apoe/Apoa1 double-knockout mice. We hypothesized that Apoe/Apoa1 double-knockout mice would mimic the phenotype of APP/Abca1(ko) mice in regards to amyloid plaques and cognitive deficits. Amyloid pathology, peripheral lipoprotein metabolism, cognitive deficits and dendritic morphology of Apoe/Apoa1 double-knockout mice were compared to APP/Abca1(ko), APP/PS1dE9, and single Apoa1 and Apoe knockouts. Contrary to our prediction, the results demonstrate that double deletion of Apoe and Apoa1 ameliorated the amyloid pathology, including amyloid plaques and soluble amyloid. In double knockout mice we show that (125)I-amyloid-β microinjected into the central nervous system cleared at a rate twice faster compared to Abca1 knockout mice. We tested the effect of Apoe, Apoa1 or Abca1 deficiency on spreading of exogenous amyloid-β seeds injected into the brain of young pre-depositing APP mice. The results show that lack of Abca1 augments dissemination of exogenous amyloid significantly more than the lack of Apoe. In the periphery, Apoe/Apoa1 double-knockout mice exhibited substantial atherosclerosis and very high levels of low density lipoproteins compared to APP/PS1dE9 and APP/Abca1(ko). Plasma level of amyloid-β42 measured at several time points for each mouse was significantly higher in Apoe/Apoa1 double-knockout then in APP/Abca1(ko) mice. This result demonstrates that mice with the lowest level of plasma lipoproteins, APP/Abca1(ko), have the lowest level of peripheral amyloid-β. Unexpectedly, and independent of amyloid pathology, the deletion of both apolipoproteins worsened behaviour deficits of double knockout mice and their performance was undistinguishable from those of Abca1 knockout mice. Finally we observed that the dendritic complexity in the CA1 region of hippocampus but not in CA2 is significantly impaired by Apoe/Apoa1 double deletion as well as by lack of ABCA1. In conclusion: (i) plasma lipoproteins may affect amyloid-β clearance from the brain by the 'peripheral sink' mechanism; and (ii) deficiency of brain APOE-containing lipoproteins is of significance for dendritic complexity and cognition

Sulfide Toxicity and Its Modulation by Nitric Oxide in Bovine Pulmonary Artery Endothelial Cells

Bovine pulmonary artery endothelial cells (BPAEC) respond in a dose-dependent manner to millimolar (0–10) levels of sodium sulfide (NaHS). No measurable increase in caspase-3 activity and no change in the extent of autophagy (or mitophagy) were observed in BPAEC. However, lactate dehydrogenase levels increased in the BPAEC exposed NaHS, which indicated necrotic cell death. In the case of galactose-conditioned BPAEC, the toxicity of NaHS was increased by 30% compared to that observed in BPAEC maintained in the regular glucose-containing culture medium, which indicated a link between mitochondrial oxidative phosphorylation and the mechanism of toxicant action. This is consistent with the widely held view that cytochrome c oxidase (complex IV of the mitochondrial electron-transport system) is the principal molecular target involved in the acute toxicity of “sulfide” (H₂S/HS^–). In support of this view, elevated NO (which can reverse cytochrome <i>c</i> oxidase inhibition) ameliorated the toxicity of NaHS and, conversely, suppression of endogenous NO production exacerbated the observed toxicity. Respirometric measurements showed the BPAEC to possess a robust sulfide oxidizing system, which was able to out-compete cytochrome c oxidase for available H₂S/HS^– at micromolar concentrations. This detoxification system has previously been reported by other groups in several cell types, but notably, not neurons. The findings appear to provide some insight into the question of why human survivors of H₂S inhalation frequently present at the clinic with respiratory insufficiency/pulmonary edema, while acutely poisoned laboratory animals tend to either succumb to cardiopulmonary paralysis or fully recover without any intervention

Genome-wide alteration of histone H3K9 acetylation pattern in mouse offspring prenatally exposed to arsenic.

Chronic exposure to arsenic in drinking water, especially in utero or perinatal exposure, can initiate neurological and cognitive dysfunction, as well as memory impairment. Several epidemiological studies have demonstrated cognitive and learning deficits in children with early exposure to low to moderate levels of arsenic, but pathogenic mechanisms or etiology for these deficits are poorly understood. Since in vivo studies show a role for histone acetylation in cognitive performance and memory formation, we examined if prenatal exposure to arsenic causes changes in the epigenomic landscape. We exposed C57Bl6/J mice to 100 μg/L arsenic in the drinking water starting 1 week before conception till birth and applied chromatin immunoprecipitation followed by high-throughput massive parallel sequencing (ChIP-seq) to evaluate H3K9 acetylation pattern in the offspring of exposed and control mice. Arsenic exposure during embryonic life caused global hypo-acetylation at H3K9 and changes in functional annotation with highly significant representation of Krüppel associated box (KRAB) transcription factors in brain samples from exposed pups. We also found that arsenic exposure of adult mice impaired spatial and episodic memory, as well as fear conditioning performance. This is the first study to demonstrate: a) genome wide changes in H3K9 acetylation pattern in an offspring prenatally exposed to arsenic, and b) a connection between moderate arsenic exposure and cognitive impairment in adult mice. The results also emphasize the applicability of Next Generation Sequencing methodology in studies aiming to reveal the role of environmental factors, other than dietary restriction, in developmental reprogramming through histone modifications during embryonic development

Mechanistic Investigation of a Non-Heme Iron Enzyme Catalyzed Epoxidation in (−)-4′-Methoxycyclopenin Biosynthesis

Mechanisms have been proposed for α-KG-dependent non-heme iron enzyme catalyzed oxygen atom insertion into an olefinic moiety in various natural products, but they have not been examined in detail. Using a combination of methods including transient kinetics, Mössbauer spectroscopy, and mass spectrometry, we demonstrate that AsqJ-catalyzed (−)-4′-methoxy­cyclopenin formation uses a high-spin Fe­(IV)-oxo intermediate to carry out epoxidation. Furthermore, product analysis on ¹⁶O/¹⁸O isotope incorporation from the reactions using the native substrate, 4′-methoxy­dehydro­cyclopeptin, and a mechanistic probe, dehydro­cyclopeptin, reveals evidence supporting oxo↔hydroxo tautomerism of the Fe­(IV)-oxo species in the non-heme iron enzyme catalysis

A Comparison of the Cyanide-Scavenging Capabilities of Some Cobalt-Containing Complexes in Mice

Four cobalt-containing macrocyclic compounds previously shown to ameliorate cyanide toxicity have been comparatively evaluated with an acute sublethal toxicity model in conscious (unanesthetized) adult male Swiss-Webster mice. All of the compounds (the cobalt-corrins cobalamin and cobinamide, a cobalt-porphyrin, plus a cobalt-Schiff base macrocycle) given 5 min prior to the toxicant dose significantly decreased the righting-recovery time of cyanide-intoxicated mice, but the doses required for maximal antidotal effect varied. Additionally, all of the compounds tested significantly reduced the righting-recovery time when administered at either 1 or 2 min after cyanide intoxication, but none of the compounds tested significantly reduced the righting-recovery time when delivered 5 min after the toxicant dose. Using the lowest effective dose of each compound determined during the first (prophylactic) set of experiments, neuromuscular recovery following cyanide intoxication in the presence/absence of the cobalt-based antidotes was assessed by RotaRod testing. All the compounds tested accelerated recovery of neuromuscular coordination, and no persistent impairment in any group, including those animals that received toxicant and no antidote, was apparent up to 2 weeks postexposures. The relative effectiveness of the cobalt compounds as cyanide antidotes are discussed and rationalized on the basis of the cyanide-binding stoichiometries and stability constants of the Co­(III) cyano adducts, together with consideration of the rate constants for axial ligand substitutions by cyanide in the Co­(II) forms

List of all unique and overlapping KRAB genes with significant enrichment of H3K9ac identified by HOMER in each of the conditions.

<p>Members of the KRAB box transcription factor family in arsenic and control gene sets (1757 and 1803 respectively, processed by DAVID for generation of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053478#pone-0053478-t001" target="_blank">Table 1</a>) were identified in the corresponding output Functional Annotation tables. Note, that the lists in the table do not correspond to the lists presented on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053478#pone-0053478-t001" target="_blank">Table 1</a>, where the output was according to the definitions of fold enrichment and Benjamini cut-off as described in the Methods.</p

Functional annotation clusters in common between gene lists from arsenic and control datasets.

<p>Significantly enriched Biological Processes and Molecular Functions in common for both gene lists have been identified by overlapping all terms that met the criteria as specified in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053478#pone-0053478-t001" target="_blank">Table 1</a>.</p