Biomedical subjects

H Soreq

Publications and source records attributed to H Soreq.

At least 37 records · Page 2Linked to original sources

PubMed2001

Changes in neuronal acetylcholinesterase gene expression and division of labor in honey bee colonies.

Division of labor in honey bee colonies is highlighted by adult bees making a transition at 2-3 wk of age from working in the hive to foraging for nectar and pollen outside. This behavioral development involves acquisition of new tasks that may require advanced learning capabilities. Because acetylcholinesterase (AChE) hydrolyzes acetylcholine, a major neurotransmitter associated with learning in the insect brain, we searched for changes in AChE expression in the brain during bee behavioral development. Biochemical aspects of the AChE protein were similar in foragers and "nurse" bees that work in the hive tending brood. However, catalytic AChE activity was significantly lower in foragers. Cloning of bee AChE cDNA enabled mRNA analysis, which demonstrated that the forager-related decrease in AChE activity was associated with decreased AChE mRNA levels. This was particularly apparent in the mushroom bodies, a brain region known to be involved with olfactory and visual learning and memory. In addition, treatment with the AChE-inhibitor metrifonate improved performance in an olfactory-learning assay. These findings demonstrate long-term, naturally occurring developmental downregulation of AChE gene expression in the bee brain, and suggest that this genomic plasticity can contribute to facilitated learning capabilities in forager bees.

Acetylcholinesterase↗

PubMed2001

ARP, a peptide derived from the stress-associated acetylcholinesterase variant, has hematopoietic growth promoting activities.

BACKGROUND: Psychological stress induces rapid and long-lasting changes in blood cell composition, implying the existence of stress-induced factors that modulate hematopoiesis. Here we report the involvement of the stress-associated "readthrough" acetylcholinesterase (AChE-R) variant, and its 26 amino acid C-terminal domain (ARP) in hematopoietic stress responses. MATERIALS AND METHODS: We studied the effects of stress, cortisol, antisense oligonucleotides to AChE, and synthetic ARP on peripheral blood cell composition and clonogenic progenitor status in mice under normal and stress conditions, and on purified CD34 cells of human origin. We employed in situ hybridization and immunocytochemical staining to monitor gene expression, and 5-bromo-2-deoxyuridine (BrdU), primary liquid cultures, and clonogenic progenitor assays to correlate AChE-R and ARP with proliferation and differentiation of hematopoietic progenitors. RESULTS: We identified two putative glucocorticoid response elements in the human ACHE gene encoding AChE. In human CD34+ hematopoietic progenitor cells, cortisol elevated AChE-R mRNA levels and promoted hematopoietic expansion. In mice, a small peptide crossreacting with anti-ARP antiserum appeared in serum following forced swim stress. Ex vivo, ARP was more effective than cortisol and equally as effective as stem cell factor in promoting expansion and differentiation of early hematopoietic progenitor cells into myeloid and megakaryocyte lineages. CONCLUSIONS: Our findings attribute a role to AChE-R and ARP in hematopoietic homeostasis following stress, and suggest the use of ARP in clinical settings where ex vivo expansion of progenitor cells is required.

Acetylcholinesterase↗

PubMed2000

Excess "read-through" acetylcholinesterase attenuates but the "synaptic" variant intensifies neurodeterioration correlates.

Acute stress increases the risk for neurodegeneration, but the molecular signals regulating the shift from transient stress responses to progressive disease are not yet known. The "read-through" variant of acetylcholinesterase (AChE-R) accumulates in the mammalian brain under acute stress. Therefore, markers of neurodeterioration were examined in transgenic mice overexpressing either AChE-R or the "synaptic" AChE variant, AChE-S. Several observations demonstrate that excess AChE-R attenuates, whereas AChE-S intensifies, neurodeterioration. In the somatosensory cortex, AChE-S transgenics, but not AChE-R or control FVB/N mice, displayed a high density of curled neuronal processes indicative of hyperexcitation. In the hippocampus, AChE-S and control mice, but not AChE-R transgenics, presented progressive accumulation of clustered, heat shock protein 70-immunopositive neuronal fragments and displayed a high incidence of reactive astrocytes. Our findings suggest that AChE-R serves as a modulator that may play a role in preventing the shift from transient, acute stress to progressive neurological disease.

Acetylcholinesterase↗

PubMed2000

A transcription-activating polymorphism in the ACHE promoter associated with acute sensitivity to anti-acetylcholinesterases.

Hypersensitivity to acetylcholinesterase inhibitors (anti-AChEs) causes severe nervous system symptoms under low dose exposure. In search of direct genetic origin(s) for this sensitivity, we studied six regions in the extended 22 kb promoter of the ACHE gene in individuals who presented adverse responses to anti-AChEs and in randomly chosen controls. Two contiguous mutations, a T-->A substitution, disrupting a putative glucocorticoid response element, and a 4-bp deletion, abolishing one of two adjacent HNF3 binding sites, were identified 17 kb upstream of the transcription start site. Allele frequencies for these mutations were 0.006 and 0.012, respectively, in 333 individuals of various ethnic origins, with a strong linkage between the deletion and the biochemically neutral H322N mutation in the coding region of ACHE. Heterozygous carriers of the deletion included a proband who presented with acute hypersensitivity to the anti-AChE pyridostigmine and another with unexplained excessive vomiting during a fourth pregnancy following three spontaneous abortions. Electromobility shift assays, transfection studies and measurements of AChE levels in immortalized lymphocytes as well as in peripheral blood from both carriers and non-carriers, revealed functional relevance for this mutation both in vitro and in vivo and showed it to increase AChE expression, probably by alleviating competition between the two hepatocyte nuclear factor 3 binding sites. Moreover, AChE-overexpressing transgenic mice, unlike normal FVB/N mice, displayed anti-AChE hypersensitivity and failed to transcriptionally induce AChE production following exposure to anti-AChEs. Our findings point to promoter polymorphism(s) in the ACHE gene as the dominant susceptibility factor(s) for adverse responses to exposure or to treatment with anti-AChEs.

Acetylcholinesterase↗

PubMed2000

Nicotinic receptor subtypes in human brain ageing, Alzheimer and Lewy body diseases.

Human brain ageing is associated with reductions in a variety of nicotinic receptors subtypes, whereas changes in age-related disorders including Alzheimer's disease or Parkinson's disease are more selective. In Alzheimer's disease, in the cortex there is a selective loss of the alpha4 (but not alpha3 or 7) subunit immunoreactivity and of nicotine or epibatidine binding but not alpha-bungarotoxin binding. Epibatidine binding is inversely correlated with clinical dementia ratings and with the level of Abeta1-42, but not related to plaque or tangle densities. In contrast, alpha-bungarotoxin binding is positively correlated with plaque densities in the entorhinal cortex. In human temporal cortex loss of acetylcholinesterase catalytic activity is positively correlated with decreased epibatidine binding and in a transgenic mouse model over expressing acetylcholinesterase, epibatidine binding is elevated. In Parkinson's disease, loss of striatal nicotine binding appears to occur early but is not associated with a loss of alpha4 subunit immunoreactivity. Tobacco use in normal elderly individuals is associated with increased alpha4 immunoreactivity in the cortex and lower densities of amyloid-beta plaques, and with greater numbers of dopaminergic neurons in the substantia nigra pars compacta. These findings indicate an early involvement of the alpha4 subunit in beta-amyloidosis but not in nigro-striatal dopaminergic degeneration.

Acetylcholinesterase↗

PubMed2000

Antisense prevention of neuronal damages following head injury in mice.

Closed head injury (CHI) is an important cause of death among young adults and a prominent risk factor for nonfamilial Alzheimer's disease. Emergency intervention following CHI should therefore strive to improve survival, promote recovery, and prevent delayed neuropathologies. We employed high-resolution nonradioactive in situ hybridization to determine whether a single intracerebro-ventricular injection of 500 ng 2'-O-methyl RNA-capped antisense oligonucleotide (AS-ODN) against acetylcholinesterase (AChE) mRNA blocks overexpression of the stress-related readthrough AChE (AChE-R) mRNA splicing variant in head-injured mice. Silver-based Golgi staining revealed pronounced dendrite outgrowth in somatosensory cortex of traumatized mice 14 days postinjury that was associated with sites of AChE-R mRNA overexpression and suppressed by anti-AChE AS-ODNs. Furthermore, antisense treatment reduced the number of dead CA3 hippocampal neurons in injured mice, and facilitated neurological recovery as determined by performance in tests of neuromotor coordination. In trauma-sensitive transgenic mice overproducing AChE, antisense treatment reduced mortality from 50% to 20%, similar to that displayed by head-injured control mice. These findings demonstrate the potential of antisense therapeutics in treating acute injury, and suggest antisense prevention of AChE-R overproduction to mitigate the detrimental consequences of various traumatic brain insults.

Acetylcholinesterase↗

PubMed2000

Differentiation of human embryonic stem cells into embryoid bodies compromising the three embryonic germ layers.

BACKGROUND: Embryonic stem (ES) cells are lines of cells that are isolated from blastocysts. The murine ES cells were demonstrated to be true pluripotent cells as they differentiate into all embryonic lineages. Yet, in vitro differentiation of rhesus ES cells was somewhat inconsistent and disorganized. The recent isolation of human ES cells calls for exploring their pluripotential nature. MATERIALS AND METHODS: Human ES cells were grown in suspension to induce their differentiation into embryoid bodies (EBs). The differentiation status of the human ES cells and EBs was analyzed by following the expression pattern of several lineage-specific molecular markers using reverse transcription polymerase chain reaction (RT-PCR) and in situ hybridization. RESULTS: Here we report the induction in vitro of cystic embryoid bodies from human ES cells. Our findings demonstrate induction of expression of cell-specific genes during differentiation of the human ES cells into EBs. In the human EBs, we could show a characteristic regional expression of embryonic markers specific to different cellular lineages, namely, zeta-globin (mesoderm), neurofilament 68Kd (ectoderm), and alpha-fetoprotein (endoderm). Moreover, we present a synchronously pulsing embryoid body that expresses the myocardium marker alpha-cardiac actin. In addition, dissociating the embryoid bodies and plating the cells as monolayers results in multiple morphologies, among them cells with neuronal appearance that express neurofilament 68Kd chain. CONCLUSION: Human ES cells can reproducibly differentiate in vitro into EBs comprising the three embryonic germ layers. The ability to induce formation of human embryoid bodies that contain cells of neuronal, hematopoietic and cardiac origins will be useful in studying early human embryonic development as well as in transplantation medicine.

Animals↗

PubMed2000

Genomic and transcriptional characterization of the human ACHE locus: complex involvement with acquired and inherited diseases.

BACKGROUND: Abnormal levels of the acetylcholinesterase enzyme or aberrations involving the long arm of chromosome 7, harboring the ACHE gene at 7q22, occur in various diseases such as Alzheimer's, Parkinson's, and leukemias. However, the cause(s) of these abnormalities are still unknown. OBJECTIVE: To search for the genomic elements and transcriptional processes controlling ACHE gene expression and the plausible stability of its locus, by isolating, sequencing and characterizing the human (h)ACHE locus and its mRNA products. METHODS: Three clones containing the ACHE gene were isolated from a human chromosome 7 cosmid library. Two of these clones were thereafter sequenced and searched for repetitive elements, open reading frames and corresponding expressed sequence tags. Reverse transcription-polymerase chain reaction was employed to further explore these findings. RESULTS: The locus harboring the G,C-rich ACHE gene was found to be exceptionally rich in Alu repeats. It includes an additional, inversely oriented gene (ARS), tentatively associated with arsenite resistance. EST clones corresponding to both genes were found in cDNA libraries from 11 different human tissue sources, with ARS expressed in 10 additional tissues. Co-regulation of brain ACHE and ARS was suggested from their mutually increased expression following acute psychological stress. CONCLUSIONS: The abundance of Alu retrotransposones may predispose the ACHE locus to chromosomal rearrangements. Additionally, coordinated transcriptional regulation is implied from the joint ARS-AChE expression in stress insult responses. Disease-related changes in AChE may therefore reflect locus-specific regulation mechanisms affecting multiple tissues.

Acetylcholinesterase↗

PubMed2000

Anti-sense approach to anticholinesterase therapeutics.

The acetylcholine-hydrolyzing enzyme, acetylcholinesterase, is the molecular target of approved drugs for Alzheimer's disease and myasthenia gravis. However, recent data implicate AChE splicing variants in the etiology of complex diseases such as AD and MG. Despite the large arsenal of anti-AChE drugs, therapeutic inhibitors are primarily targeted towards an active site shared by all variants. In contrast, anti-sense oligonucleotides attack unique mRNA sequences rather than tertiary protein structures. AS-ODNs thus offer a means to target gene expression in a highly discriminative manner using very low concentrations of drug. In light of the likely role(s) of specific AChE variants in various diseases affecting cholinergic neurotransmission, the potential contribution that anti-sense technology can make towards improved approaches to anti-AChE therapeutics deserves serious attention.

Acetylcholinesterase↗

PubMed1999

Manipulations of ACHE gene expression suggest non-catalytic involvement of acetylcholinesterase in the functioning of mammalian photoreceptors but not in retinal degeneration.

To explore role(s) of acetylcholinesterase (AChE) in functioning and diseased photoreceptors, we studied normal (rd/+) and degenerating (rd/rd) murine retinas. All retinal neurons, expressed AChEmRNA throughout fetal development. AChE and c-Fos mRNAs peaked at post-natal days 10-12, when apoptosis of rd/rd photoreceptors begins. Moreover, c-Fos and AChEmRNA were co-overexpressed in rd/rd mice producing transgenic human (h), and host (m) AChE, but not in rd/+ mice. However, mAChE overexpression also occurred in transgenics expressing human serum albumin. Drastic variations in AChE catalytic activity were ineffective during development. Neither transgenic excess nor diisopropylfluorophosphonate (DFP) inhibition (80%) affected the rd phenotype; nor did DFP exposure induce photoreceptor degeneration or affect other key cholinergic proteins in rd/+ mice, unlike reports of adult mice and despite massive induction under DFP of c-Fos70 years). Therefore, the extreme retinal sensitivity to AChE modulation may reflect non-catalytic function(s) of AChE in adult photoreceptors. These findings exclude AChE as causing the rd phenotype, suggest that its primary function(s) in mammalian retinal development are non-catalytic ones and indicate special role(s) for the AChE protein in adult photoreceptors.

Acetylcholinesterase↗

PubMed1999

Anticholinesterases induce multigenic transcriptional feedback response suppressing cholinergic neurotransmission.

Cholinesterase inhibitors (anti-ChEs) include a wide range of therapeutic, agricultural and warfare agents all aimed to inhibit the catalytic activity of the acetylcholine (ACh) hydrolysing enzyme acetylcholinesterase (AChE). In addition to promoting immediate excitation of cholinergic neurotransmission through transient elevation of synaptic ACh levels, anti-ChEs exposure is associated with long-term effects reminiscent of post-traumatic stress disorder. This suggested that exposure to anti-ChEs leads to persistent changes in brain proteins and called for exploring the mechanism(s) through which such changes could occur. For this purpose, we established an in vitro system of perfused, sagittal mouse brain slices which sustains authentic transcriptional responses for over 10 h and enables the study of gene regulation under controlled exposure to anti-ChEs. Slices were exposed to either organophosphate or cabamate anti-ChEs, both of which induced within 10 min excessive overexpression of the mRNA encoding the immediate early response transcription factor c-Fos. Twenty minutes later we noted 8-fold increases over control levels in AChE mRNA, accompanied by a 3-fold decrease in the mRNAs encoding for the ACh synthesizing enzyme choline acetyltransferase (ChAT) and the vesicular ACh transporter (VAChT). No changes were detected in synaptophysin mRNA levels. These modulations in gene expression paralleled those taking place under in vivo exposure. Of particular concern is the possibility that feedback processes leading to elevated levels of brain AChE may be similarly associated with low-level exposure to common organophosphorous anti-cholinesterases, and lead to long-term deleterious changes in cognitive functions.

Acetylcholinesterase↗

PubMed1999

Structural roles of acetylcholinesterase variants in biology and pathology.

Apart from its catalytic function in hydrolyzing acetylcholine, acetylcholinesterase (AChE) affects cell proliferation, differentiation and responses to various insults, including stress. These responses are at least in part specific to the three C-terminal variants of AChE which are produced by alternative splicing of the single ACHE gene. 'Synaptic' AChE-S constitutes the principal multimeric enzyme in brain and muscle; soluble, monomeric 'readthrough' AChE-R appears in embryonic and tumor cells and is induced under psychological, chemical and physical stress; and glypiated dimers of erythrocytic AChE-E associate with red blood cell membranes. We postulate that the homology of AChE to the cell adhesion proteins, gliotactin, glutactin and the neurexins, which have more established functions in nervous system development, is the basis of its morphogenic functions. Competition between AChE variants and their homologs on interactions with the corresponding protein partners would inevitably modify cellular signaling. This can explain why AChE-S exerts process extension from cultured amphibian, avian and mammalian glia and neurons in a manner that is C-terminus-dependent, refractory to several active site inhibitors and, in certain cases, redundant to the function of AChE-like proteins. Structural functions of AChE variants can explain their proliferative and developmental roles in blood, bone, retinal and neuronal cells. Moreover, the association of AChE excess with amyloid plaques in the degenerating human brain and with progressive cognitive and neuromotor deficiencies observed in AChE-transgenic animal models most likely reflects the combined contributions of catalytic and structural roles.

Acetylcholinesterase↗

PubMed1999

Human erythrocyte but not brain acetylcholinesterase hydrolyses heroin to morphine.

1. In human blood, heroin is rapidly hydrolysed by sequential deacylation of two ester bonds to yield first 6-monoacetylmorphine (6-MAM), then morphine. 2. Serum butyrylcholinesterase (BuChE) hydrolyses heroin to 6-MAM with a catalytic efficiency of 4.5/min per mumol/L, but does not proceed to produce morphine. 3. In vitro, human erythrocyte acetylcholinesterase (AChE) hydrolyses heroin to 6-MAM, with a catalytic efficiency of 0.5/min per mumol/L under first-order kinetics. Moreover, erythrocyte AChE, but not BuChE is capable of further hydrolysing 6-MAM to morphine, albeit at a considerably slower rate. 4. Both hydrolysis steps by erythrocyte AChE were totally blocked by the selective AChE inhibitor BW284c51 but were not blocked by the BuChE-specific inhibitor, iso-OMPA (tetraisopropylpyrophosphoramide). 5. The brain synaptic form of AChE, which differs from the erythrocyte enzyme in its C-terminus, was incapable of hydrolysing heroin. 6. Heroin suppressed substrate hydrolysis by antibody-immobilized erythrocyte but not by brain AChE. 7. These findings reveal a new metabolic role for erythrocyte AChE, the biological function of which is as yet unexplained, and demonstrate distinct biochemical properties for the two AChE variants, which were previously considered catalytically indistinguishable.

Acetylcholinesterase↗

PubMed1999

Antisense technologies have a future fighting neurodegenerative diseases.

Our growing understanding of the role that unfavorable patterns of gene expression play in the etiology of neurodegenerative disease emphasizes the need for strategies to selectively block the biosynthesis of harmful proteins in the brain. Antisense technologies are ideally suited to this purpose. Tailor-designed to target specific RNA, antisense oligonucleotides and ribozymes offer tools to suppress the production of proteins mediating neurodegeneration. Although technical limitations must still be overcome, the antisense approach represents a novel and exciting strategy for intervention in diseases of the central nervous system.

Animals↗

PubMed1999

Tracking cholinergic pathways from psychological and chemical stressors to variable neurodeterioration paradigms.

Cholinergic hyperexcitation can be induced by both acute psychological stress and exposure to acetylcholinesterase inhibitors. Both factors are known risk factors for delayed neurodeterioration processes such as Alzheimer's disease and Parkinson's disease. Recent publications on the involvement of cholinergic pathways in these and other neurodeterioration syndromes are reviewed.

Brain↗

PubMed1999

Human osteogenesis involves differentiation-dependent increases in the morphogenically active 3' alternative splicing variant of acetylcholinesterase.

The extended human acetylcholinesterase (AChE) promoter contains many binding sites for osteogenic factors, including 1,25-(OH)2 vitamin D3 and 17beta-estradiol. In differentiating osteosarcoma Saos-2 cells, both of these factors enhanced transcription of the AChE mRNA variant 3' terminated with exon 6 (E6-AChE mRNA), which encodes the catalytically and morphogenically active E6-AChE isoform. In contrast, antisense oligodeoxynucleotide suppression of E6-AChE mRNA expression increased Saos-2 proliferation in a dose- and sequence-dependent manner. The antisense mechanism of action was most likely mediated by mRNA destruction or translational arrest, as cytochemical staining revealed reduction in AChE gene expression. In vivo, we found that E6-AChE mRNA levels rose following midgestation in normally differentiating, postproliferative fetal chondrocytes but not in the osteogenically impaired chondrocytes of dwarf fetuses with thanatophoric dysplasia. Taken together, these findings suggest morphogenic involvement of E6-AChE in the proliferation-differentiation balance characteristic of human osteogenesis.

Acetylcholinesterase↗

PubMed1999

Neurobiology.

The IBRO World Congress of Neuroscience covered the full spectrum of neuroscience, from molecular and developmental neurobiology to behavioral pharmacology and neurodegeneration.

Journal Article↗

PubMed1998

In vivo and in vitro resistance to multiple anticholinesterases in Xenopus laevis tadpoles.

Natural and man-made anticholinesterases comprise a significant share of the Xenobiotic poisons to which many living organisms are exposed. To evaluate the potential correlation between the resistance of acetylcholinesterase (AChE) to such toxic agents and the systemic toxicity they confer, we characterized the sensitivity of AChE from Xenopus laevis tadpoles to inhibitors, examined the susceptibility of such tadpoles to poisoning by various anticholinesterases and tested the inhibitor sensitivities of recombinant human AChE produced in these amphibian embryos from microinjected DNA. Our findings reveal exceptionally high resistance of Xenopus AChE to carbamate, organophosphate and quaternary anticholinesterases. In spite of the effective in vivo penetrance to Xenopus tadpole tissues of paraoxon, the poisonous metabolite of the pro-insecticide parathion, the amphibian embryos displayed impressive resistance to this organophosphorous agent. The species specificity of this phenomenon was clearly displayed in Xenopus tadpoles expressing recombinant human AChE, which was far more sensitive than the frog enzyme to in vivo paraoxon inhibition. Our findings demonstrate a clear correlation between AChE susceptibility to enzymatic inhibition and the systemic toxicity of anticholinesterases and raise a serious concern regarding the use of Xenopus tadpoles for developmental toxicology tests of anticholinesterases.

Animals↗