Neurodegeneration最新文献

Maltol (3-hydroxy-2-methyl-4-pyrone), a product of carbohydrate degradation, is known to enhance aluminium-induced neurofibrillary degeneration in neuronal systems, but few toxicological studies have been conducted. We report maltol toxicity in neuroblastoma cell lines of mouse (Neuro 2a) and human (IMR 32) origin, and in primary murine fetal hippocam-pal neuronal cultures. As determined by MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxy-methoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt] conversion, maltol exhibited a dose-dependent toxicity on the viability of both neuroblastoma cell lines, but the toxicity was more pronounced in Neuro 2a cells. Maltol was also toxic in a dose-dependent manner in primary murine fetal hippocampal neurons at micromolar concentrations. Electrophoresis of DNA extracted from maltol-intoxicated cells showed a laddering pattern, suggestive of apop-totic cell death. In the maltol-exposed hippocampal neuronal cultures, fragmented DNA ends were visualizedin situin morphologically condensed nuclei by terminal deoxynucleotidyl transferase with digoxigenin-labelled UTP and subsequent immunohistochemistry. Collectively, our findings suggest that the toxic effect of maltol is mediated through apoptosis. Further toxicological investigations are warranted, since maltol is found in the daily diet of humans.

Our research has shown that the tolerance of Alzheimer's disease (AD) patients for anti-dementia compounds is frequently higher but occasionally lower than the tolerance of healthy young or elderly populations. Such differences can either pose safety problems in later efficacy studies if patients cannot tolerate the dosages previously deemed ‘safe’ in healthy populations, or interfere with determining efficacy if inadequate doses are employed. We recommend use of a ‘bridging study’, which optimizes dosage early in development by determining the maximum tolerated dose of a compound in patients. Consecutive panels of patients each receive higher doses of study drug until a minimum intolerated dose is reached. The dose immediately below this one is then considered the maximum tolerated dose. Careful subject selection, adequate facilities, and highly qualified, experienced personnel, are critical to the successful implementation of a bridging study. Correctly done, bridging can streamline the overall drug development process while making Phase II and III trials safer for patients, and has immense potential for accelerating the search for compounds that have efficacy in AD.

The neurotoxin MPTP has been used to create an animal model of Parkinson's disease in the mouse, in part, because it causes a significant loss of dopaminergic neurons in the substantia nigra (nucleus A9). The purpose of the present study was to determine whether MPTP also causes degeneration of midbrain dopaminergic neurons in nuclei A8 and A10 in the mouse, as occurs in humans with Parkinson's disease. Two commonly used strains of mice were used: FVB/N and C57BL/6. MPTP was administered in cumulative doses of 50—300 mg/kg. Seven days later, dopamine concentrations were measured in the striatum using high performance liquid chromatography, and midbrain dopaminergic neurons were identified using an antibody against tyrosine hydroxylase. The cell locations were mapped with a computer imaging system. In the FVB/N strain, there was a dose-dependent decrease in striatal dopamine concentrations. Although the highest dose (300 mg/kg) caused an 86% reduction in striatal dopamine concentrations, there was only a moderate and non-significant loss of midbrain dopaminergic neurons. In the C57BL/6 strain, however, a high dose of MPTP (240 mg/kg) caused a significant reduction in both striatal dopamine concentrations (95%), and midbrain dopaminergic cells; 69% loss of nucleus A8 cells, 75% loss of nucleus A9 cells, and in nucleus A10 subnuclei there was 42% loss of ventral tegmental area cells, 55% loss of interfascicular nucleus cells, and no loss of cells in the central linear nucleus. These data (1) provide further evidence for differential susceptibility to MPTP toxicity among different mouse strains, (2) indicate that a significant depletion of striatal dopamine is not necessarily due to degeneration of midbrain dopaminergic neurons, (3) provide the precise locations of midbrain dopaminergic cells that are vulnerable to MPTP, which will aid future studies that seek to determine the mechanism/s by which MPTP selectively destroys only certain midbrain dopaminergic neurons, and (4) indicate that MPTP produces midbrain dopaminergic neuronal degeneration in the same nuclei in the C57BL16 mouse that degenerate in humans with Parkinson's disease..

The neuroprotective effects of recombinant neutrophil inhibitory factor (NIF) have been assessed with temporary (2 h) middle cerebral artery (MCA) occlusion in the rat using the intraluminal suture technique. Administration of NIF (1.5 mg/kg, i.v.) immediately after the onset of reperfusion and at 4 and 6 h post-MCA occlusion significantly reduced both hemispheric infarct volume (P< 0.001) and brain swelling (P< 0.001), and improved neurological outcome (P< 0.02) when assessed at 24 h. These results demonstrate the marked neuroprotective efficacy of NIF in a rat model of transient focal cerebral ischaemia

Studies of the neurochemical pathology of AD have indicated that early in the course of the disease, abnormalities of relatively few neurotransmitters are obvious. The most reliable and consistent changes are those seen in the cholinergic innervation of the cortex and the cortical pyramidal neurones. However, by the time of death there is usually considerable involvement of other neurones.

The hypothesis that the distribution of neurodegeneration in Alzheimer's disease results from the spread of the pathology via anatomical connections is reviewed in the light of recent advances in knowledge of the connectivity of the cerebral cortex. Current understanding of cortical connections allows a more detailed examination of the distribution of pathology, particularly neurofibrillary tangles, in relation to this hypothesis. In particular, quantitative assessment of corticocortical pathways opens up the possibility of specific testing of the hypothesis. Theoretical considerations are discussed, and a predicted spread of pathology beginning in the olfactory centres of the medial temporal lobe and spreading retrogradely via known pathways is presented.

In this report we focus on the characterization of appican, the chondroitin sulfate proteoglycan form of amyloid precursor protein (APP), and the role that it and other proteoglycans may play in AD. Appican is expressed by certain transformed cell lines of neural origin, namely C6 cells and N2a neuroblastomas. It is detected in both human and rat brain and in primary cultures is expressed by astrocytes, but not neurons. The core protein of appican has been shown to be an alternatively spliced isoform of APP, lacking exon 15 of the APP gene, originally identified in leukocytes (L-APP). Splicing out of exon 15 results in the joining of exons 14 and 16, and formation of an Asp-Xaa-Ser-Gly consensus sequence for chondroitin sulfate chain attachment to serine 619 of L-APP, which lies 16 amino acids upstream of the A β peptide sequence. Mutation of this serine residue to an alanine prevented chondroitin sulfate chain addition to the core protein. Levels of appican expression could be regulated by growth conditions independently of APP, suggesting that these molecules may serve distinct physiological roles within the cell. Morphological changes were also observed in both astrocytic and transformed cell cultures, that appeared to reflect changes in levels of appican expression. Preliminary data suggest that appican may be a strong cell adhesion molecule. Transfected C6 glioma cells overexpressing appican remained attached to tissue culture dishes markedly better than either C6 cells over-expressing exon-15 containing APP or WT C6 cells. Appican-enriched extracellular matrix (ECM) was also observed to serve as a much better substrate for attachment of N2a neuroblastomas, pheocromocytoma PC12 cells and primary astrocytes compared to APP enriched ECM.

Platelet monoamine oxidase activity levels have been evaluated in several neuropsychiatric disorders, to identify biochemical markers for pathological brain functioning. In the present work, we assayed both total and molecular monoamine oxidase activity in platelets of parkinsonian and demented patients: both showed significantly higher enzyme activity values than healthy controls. Thus, high platelet monoamine oxidase activity levels seem to be related to an increased intrinsic activity of single enzyme molecules. A significant positive correlation was found between platelet monoamine oxidase activity and severity of illness in both disorders: monoamine oxidase activity, therefore, may be considered as a state-dependent marker for neuro-degeneration. Such findings are discussed with reference to central nervous system biochemical abnormalities in parkinsonian and demented subjects; it might be that in both Parkinson's Disease and in dementia of Alzheimer type some central biochemical changes are reflected in certain peripheral tissues (thrombocytes, for instance), or that a systemic derangement accompanies the cerebral involvement.

Cerebrospinal fluid (CSF) concentrations of somatostatin-like immunoreactivity (SLI), high molecular weight form somatostatin (HMV-SST), somatostatin-25/28 (SST-25/28), somatostatin–14 (SST-14), Des-ala-somatostatin (Des-ala-SST), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5–HIAA) were measured in 21 patients with Binswanger's dementia (BD). Patients were classed into three stages of intellectual deterioration according to the Global de-terioration scale (GDS). Levels of SLI were significantly decreased in patients suffering from BD, compared to a control group (19.7 ± 11.6 fmol/ml vs. 30.5 ± 8.6 fmol/ml,P< 0.01). There was no correlation with dementia scores (r= 0.34,P= 0.51). The observed qualitative and quantitative changes in the molecular pattern of SLI suggest the occurrence of a dysregulated posttranslational processing in patients with BD. Whereas 5-HIAA levels were not significantly changed in patients with BD, HVA was significantly increased in mild to moderate dementia (GDS 2-4) and significantly decreased in severe cases (GDS 7) (224.3 ± 69.9 nmol/ml vs. 364.9 ± 103.8 nmol/ml,P< 0.01); this correlated with dementia scores (r= −0.59,P< 0.01). The existence of significant correlations between SLI, 5-HIAA and HVA in BD point to a heterogeneous and generalized neurochemical process affecting several transmitter systems and functions.