Astrocytic expression of the Alzheimer's disease beta-secretase (BACE1) is stimulus-dependent

The beta-site APP-cleaving enzyme (BACE1) is a prerequisite for the generation of beta-amyloid peptides, which give rise to cerebrovascular and parenchymal beta-amyloid deposits in the brain of Alzheimer's disease patients. BACE1 is neuronally expressed in the brains of humans and experimental animals such as mice and rats. In addition, we have recently shown that BACE1 protein is expressed by reactive astrocytes in close proximity to beta-amyloid plaques in the brains of aged transgenic Tg2576 mice that overexpress human amyloid precursor protein carrying the double mutation K670N-M671L. To address the question whether astrocytic BACE1 expression is an event specifically triggered by beta-amyloid plaques or whether glial cell activation by other mechanisms also induces BACE1 expression, we used six different experimental strategies to activate brain glial cells acutely or chronically. Brain sections were processed for the expression of BACE1 and glial markers by double immunofluorescence labeling and evaluated by confocal laser scanning microscopy. There was no detectable expression of BACE1 protein by activated microglial cells of the ameboid or ramified phenotype in any of the lesion paradigms studied. In contrast, BACE1 expression by reactive astrocytes was evident in chronic but not in acute models of gliosis. Additionally, we observed BACE1-immunoreactive astrocytes in proximity to beta-amyloid plaques in the brains of aged Tg2576 mice and Alzheimer's disease patients.     

A proposed mechanism of bupivacaine-induced contraction of human umbilical artery smooth muscle cells

This in vitro study using ring preparations of human umbilical vessels and cultured human umbilical artery smooth muscle cells was designed to determine: (a) the mechanism of bupivacaine-induced contraction of ring preparations, and (b) whether similar concentrations of bupivacaine release Cal(2+) in cultured smooth muscle cells. Isometric tension was recorded from ring preparations of human umbilical veins and arteries in an isolated tissue chamber. Separate fluorescence and electrophysiology studies were done with cultured human umbilical artery smooth muscle cells. Bupivacaine-evoked contractions of ring preparations were either tonic or twitch in nature. The contraction of ring preparations was dependent on extracellular Cal(2+) and sensitive to nifedipine inhibition. Bupivacaine also increased intracellular Cal(2+) in patterns consistent with tonic or phasic tension responses seen in isometric recordings. In addition, the membrane-resting potential was depolarized by bupivacaine. Since similar concentrations of bupivacaine caused both contraction and a rise in intracellular Ca(2+), the bupivacaine-evoked contraction was the result of increased cell Cal(2+) and the source of this Ca(2+) was the extracellular space.     

Hyperactivity is a Core Endophenotype of Elevated Neuregulin-1 Signaling in Embryonic Glutamatergic Networks

The neuregulin 1 (NRG1) ErbB4 module is at the core of an “at risk” signaling pathway in schizophrenia. Several human studies suggest hyperstimulation of NRG1-ErbB4 signaling as a plausible pathomechanism; however, little is known about the significance of stage-, brain area-, or neural cell type-specific NRG1-ErbB4 hyperactivity for disease-relevant brain endophenotypes. To address these spatiotemporal aspects, we generated transgenic mice for Cre recombinase-mediated overexpression of cystein-rich domain (CRD) NRG1, the most prominent NRG1 isoform in the brain. A comparison of “brain-wide” vs cell type-specific CRD-NRG1 overexpressing mice revealed that pathogenic CRD-NRG1 signals for ventricular enlargement and neuroinflammation originate outside glutamatergic neurons and suggests a subcortical function of CRD-NRG1 in the control of body weight. Embryonic onset of CRD-NRG1 in glutamatergic cortical networks resulted in reduced inhibitory neurotransmission and locomotor hyperactivity. Our findings identify ventricular enlargement and locomotor hyperactivity, 2 main endophenotypes of schizophrenia, as specific consequences of spatiotemporally distinct expression profiles of hyperactivated CRD-NRG1 signaling.     

Role of prolyl endopeptidase in intracellular transport and protein secretion

Prolyl endopeptidase (E.C. 3.4.21.26, PREP) also known as prolyl oligopeptidase is an enzyme which cleaves several peptides at the carboxyl side of proline residues. Since brain contains relatively large amounts of this enzyme and because of its substrate specificity it has been suggested to play a role in the metabolism of neuropeptides, acting both on their maturation and their degradation. The final step of neuropeptide processing occurs in the synaptic vesicles and degradation of most of these peptides takes place in the synaptic cleft. Thus, a localization of PREP in these cellular compartments appears to be feasible. Here we summarize recent data and provide novel evidence for the subcellular localization of PREP. Most importantly, immunocytochemical double labelling, confocal laser scanning and electron microscopic procedures as well as functional assays strongly suggest a role for PREP in intracellular transport mechanisms and in protein secretion.     

Glutaminyl cyclase contributes to the formation of focal and diffuse pyroglutamate (pGlu)-Aβ deposits in hippocampus via distinct cellular mechanisms

In the hippocampal formation of Alzheimer??s disease (AD) patients, both focal and diffuse deposits of A?? peptides appear in a subregion- and layer-specific manner. Recently, pyroglutamate (pGlu or pE)-modified A?? peptides were identified as a highly pathogenic and seeding A?? peptide species. Since the pE modification is catalyzed by glutaminyl cyclase (QC) this enzyme emerged as a novel pharmacological target for AD therapy. Here, we reveal the role of QC in the formation of different types of hippocampal pE-A?? aggregates. First, we demonstrate that both, focal and diffuse pE-A?? deposits are present in defined layers of the AD hippocampus. While the focal type of pE-A?? aggregates was found to be associated with the somata of QC-expressing interneurons, the diffuse type was not. To address this discrepancy, the hippocampus of amyloid precursor protein transgenic mice was analysed. Similar to observations made in AD, focal (i.e. core-containing) pE-A?? deposits originating from QC-positive neurons and diffuse pE-A?? deposits not associated with QC were detected in Tg2576 mouse hippocampus. The hippocampal layers harbouring diffuse pE-A?? deposits receive multiple afferents from QC-rich neuronal populations of the entorhinal cortex and locus coeruleus. This might point towards a mechanism in which pE-A?? and/or QC are being released from projection neurons at hippocampal synapses. Indeed, there are a number of reports demonstrating the reduction of diffuse, but not of focal, A?? deposits in hippocampus after deafferentation experiments. Moreover, we demonstrate in neurons by live cell imaging and by enzymatic activity assays that QC is secreted in a constitutive and regulated manner. Thus, it is concluded that hippocampal pE-A?? plaques may develop through at least two different mechanisms: intracellularly at sites of somatic QC activity as well as extracellularly through seeding at terminal fields of QC expressing projection neurons.     

8. THE CYTOGENETIC ANALYSIS IN OCCUPATIONALLY EXPOSED GROUPS IN THE CZECH REPUBLIC

Biomonitoring of the genotoxic potential of occupational and environmental factors and their biological effects in man is essential for ensuring primary prevention of human cancers and damage of genetic material. The groups of population monitored in the Czech Republic for the occupational exposure to clastogenic genotoxins comprise broad spectrum of exposure, the most of them involve complex mixtures of gases, vapors, and particular matters. The increase of the chromosomal aberration frequency     

The risk of anal incontinence in obese women

The objectives of this study was to estimate the risk of anal incontinence in morbidly obese women and to identify risk factors associated with anal incontinence in an obese population sample. A case-control study based on the registry of a university hospital obesity unit. A consecutive sample of women with body mass index > or = 35 (obesity class II) was randomly matched by age, gender and residential county to control subjects using the computerised Register of the Total Population. Data were collected by a self-reported postal survey including detailed questions on medical and obstetrical history, obesity history, socioeconomic indices, life style factors and the validated Cleveland Clinic Incontinence Score. The questionnaire was returned by 131/179 (73%) of the cases and 453/892 (51%) of the control subjects. Compared to the control group, obese women reported a significantly increased defecation frequency (p < 0.001), inability to discriminate between flatus and faeces (p < 0.001) and flatus incontinence (p < 0.001). Compared with non-obese women, the adjusted odds ratio (OR) for flatus incontinence in morbidly obese women was 1.5 [95% confidence interval (CI) 1.1-4.1]. A history of obstetric sphincter injury was independently associated with an increased risk of flatus incontinence (OR, 4.3; 95% CI, 2.0-9.2) and incontinence of loose stools (OR, 6.6; 95% CI, 1.4-31.4). Other medical and life style interactions did not remain at significant levels in an adjusted multivariable analysis. Obese women are at increased risk for mild to moderate flatus incontinence.