共查询到11条相似文献,搜索用时 15 毫秒
1.
Shahdat Hossain† Michio Hashimoto Masanori Katakura Koji Miwa Toshio Shimada‡ Osamu Shido 《Journal of neurochemistry》2009,111(2):568-579
The mechanism of the effect of docosahexaenoic acid (DHA; C22:6, n -3), one of the essential brain nutrients, on in vitro fibrillation of amyloid β (Aβ1–42 ), Aβ1–42 -oligomers and its toxicity imparted to SH-S5Y5 cells was studied with the use of thioflavin T fluorospectroscopy, laser confocal microfluorescence, and transmission electron microscopy. The results clearly indicated that DHA inhibited Aβ1–42 -fibrill formation with a concomitant reduction in the levels of soluble Aβ1–42 oligomers. The polymerization (into fibrils) of preformed oligomers treated with DHA was inhibited, indicating that DHA not only obstructs their formation but also inhibits their transformation into fibrils. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (12.5%), Tris–Tricine gradient(4–20%) gel electrophoresis and western blot analyses revealed that DHA inhibited at least 2 species of Aβ1–42 oligomers of 15–20 kDa, indicating that it hinders these on-pathway tri/tetrameric intermediates during fibrillation. DHA also reduced the levels of dityrosine and tyrosine intrinsic fluorescence intensity, indicating DHA interrupts the microenvironment of tyrosine in the Aβ1–42 backbone. Furthermore, DHA protected the tyrosine from acrylamide collisional quenching, as indicated by decreases in Stern–Volmer constants. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide-reduction efficiency and immunohistochemical examination suggested that DHA inhibits Aβ1–42 -induced toxicity in SH-S5Y5 cells. Taken together, these data suggest that by restraining Aβ1–42 toxic tri/tetrameric oligomers, DHA may limit amyloidogenic neurodegenerative diseases, Alzheimer's disease. 相似文献
2.
Hiroyuki Kobayashi Koji Ogawa Rong Yao Olivier Lichtarge Michel Bouvier 《Traffic (Copenhagen, Denmark)》2009,10(8):1019-1033
Site-directed mutagenesis guided by evolutionary trace analysis revealed that substitution of V179 and W183 within a cluster of evolutionarily important residues on the surface of the fourth transmembrane domain of the β1 -adrenergic receptor (β1 AR) significantly reduced the propensity of the receptor to self-assemble into homodimers as assessed by bioluminescence resonance energy transfer in living cells. These results suggest that mutation of V179 and W183 result in conformational changes that reduce homodimerization either directly by interfering with the dimerization interface or indirectly by causing local misfolding that result in reduced self-assembly. However, the mutations did not cause a general misfolding of the β1 AR as they did not prevent heterodimerization with the β2 AR. The homodimerization-compromised mutants were significantly retained in the endoplasmic reticulum (ER) and could not be properly matured and trafficked to the cell surface. Lipophilic β-adrenergic ligands acted as pharmacological chaperones by restoring both dimerization and plasma membrane trafficking of the ER-retained dimerization-compromised β1 AR mutants. These results clearly indicate that homodimerization occurs early in the biosynthetic process in the ER and that pharmacological chaperones can promote both dimerization and cell surface targeting, most likely by stabilizing receptor conformations compatible with the two processes. 相似文献
3.
Abstract: β-Amyloid peptide (Aβ), a proteolytic fragment of the β-amyloid precursor protein, is a major component of senile plaques in the brain of Alzheimer's disease patients. This neuropathological feature is accompanied by increased neuronal cell loss in the brain and there is evidence that Aβ is directly neurotoxic. In the present study reduced cell viability in four different neuroblastoma cell types was observed after treatment with human Aβ1–42 for 1 day. Of the cell types tested rat PC12 and human IMR32 cells were most susceptible to Aβ toxicity. Chromosomal condensation and fragmentation of nuclei were seen in PC12, NB2 a, and B104 cells but not in IMR32 cells irrespective of their high sensitivity to Aβ. Electrophoretic analysis of cellular DNA confirmed internucleosomal DNA fragmentation typical for apoptosis in all cell types except IMR32. These findings suggest that the form of Aβ-induced cell death (necrosis or apoptosis) may depend on the cell type. 相似文献
4.
Abstract: Tolerance to and withdrawal from pentobarbital were induced in rats by continuous intracerebroventricular infusion via subcutaneously implanted osmotic minipumps. In situ hybridization of GABAA receptor α1 - and β3 -subunit mRNA was conducted using synthetic 3'- end 35 S-dATP-labeled oligodeoxynucleotide probes. Results were quantified by film densitometry. In animals that were tolerant to pentobarbital, levels of α1 -subunit mRNA were decreased in hippocampus, superior colliculus, and inferior colliculus, but levels of β3 -subunit mRNA were not affected. Dramatically increased levels of GABAA receptor subunit mRNA were observed in animals 24 h after withdrawal from chronic pentobarbital treatment. These increases occurred in cerebral cortex and cerebellum for the α1 subunit and in cerebral cortex only for the β3 -subunit. These data provide further support to the structural and pharmacological GABAA receptor heterogeneity in discrete brain areas. The observed changes of subunit expression may underlie, at least in part, the receptor up- and down-regulation observed in receptor ligand binding studies. 相似文献
5.
Christopher M. Lauderback † Janna M. Hackett Feng F. Huang ‡ Jeffrey N. Keller ‡§ Luke I. Szweda William R. Markesbery§¶ D. Allan Butterfield†§ 《Journal of neurochemistry》2001,78(2):413-416
Glutamate transporters are involved in the maintenance of synaptic glutamate concentrations. Because of its potential neurotoxicity, clearance of glutamate from the synaptic cleft may be critical for neuronal survival. Inhibition of glutamate uptake from the synapse has been implicated in several neurodegenerative disorders. In particular, glutamate uptake is inhibited in Alzheimer's disease (AD); however, the mechanism of decreased transporter activity is unknown. Oxidative damage in brain is implicated in models of neurodegeneration, as well as in AD. Glutamate transporters are inhibited by oxidative damage from reactive oxygen species and lipid peroxidation products such as 4-hydroxy-2-nonenal (HNE). Therefore, we have investigated a possible connection between the oxidative damage and the decreased glutamate uptake known to occur in AD brain. Western blots of immunoprecipitated HNE-immunoreactive proteins from the inferior parietal lobule of AD and control brains suggest that HNE is conjugated to GLT-1 to a greater extent in the AD brain. A similar analysis of beta amyloid (Abeta)-treated synaptosomes shows for the first time that Abeta1-42 also increases HNE conjugation to the glutamate transporter. Together, our data provide a possible link between the oxidative damage and neurodegeneration in AD, and supports the role of excitotoxicity in the pathogenesis of this disorder. Furthermore, our data suggests that Abeta may be a possible causative agent in this cascade. 相似文献
6.
Regulation of Cyclic AMP Formation in Cultures of Human Foetal Astrocytes by β2 -Adrenergic and Adenosine Receptors 总被引:1,自引:1,他引:0
Mary D. Woods R. Ian Freshney Stephen G. Ball† Peter F. T. Vaughan 《Journal of neurochemistry》1989,53(3):864-869
Two cell cultures, NEP2 and NEM2, isolated from human foetal brain have been maintained through several passages and found to express some properties of astrocytes. Both cell cultures contain adenylate cyclase stimulated by catecholamines with a potency order of isoprenaline greater than adrenaline greater than salbutamol much greater than noradrenaline, which is consistent with the presence of beta 2-adrenergic receptors. This study reports that the beta 2-adrenergic-selective antagonist ICI 118,551 is approximately 1,000 times more potent at inhibiting isoprenaline stimulation of cyclic AMP (cAMP) formation in both NEP2 and NEM2 than the beta 1-adrenergic-selective antagonist practolol. This observation confirms the presence of beta 2-adrenergic receptors in these cell cultures. The formation of cAMP in NEP2 is also stimulated by 5'-(N-ethylcarboxamido)adenosine (NECA) more potently than by either adenosine or N6-(L-phenylisopropyl)adenosine (L-PIA), which suggests that this foetal astrocyte expresses adenosine A2 receptors. Furthermore, L-PIA and NECA inhibit isoprenaline stimulation of cAMP formation, a result suggesting the presence of adenosine A1 receptors on NEP2. The presence of A1 receptors is confirmed by the observation that the A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine reverses the inhibition of isoprenaline stimulation of cAMP formation by L-PIA and NECA. Additional evidence that NEP2 expresses adenosine receptors linked to the adenylate cyclase-inhibitory GTP-binding protein is provided by the finding that pretreatment of these cells with pertussis toxin reverses the adenosine inhibition of cAMP formation stimulated by either isoprenaline or forskolin. 相似文献
7.
Yansheng Du Kelly R. Bales ‡§Richard C. Dodel Xiaodong Liu Michele A. Glinn †Jeffrey W. Horn Sheila P. Little ‡ Steven M. Paul 《Journal of neurochemistry》1998,70(3):1182-1188
Abstract: β-Amyloid peptides (Aβ) are deposited in an aggregated fibrillar form in both diffuse and senile plaques in the brains of patients with Alzheimer's disease. The neurotoxicity of Aβ in cultured neurons is dependent on its aggregation state, but the factors contributing to aggregation and fibril formation are poorly understood. In the present study, we investigated whether α2 -macroglobulin (α2 M), a protein present in neuritic plaques and elevated in Alzheimer's disease brain, is a potential regulatory factor for Aβ fibril formation. Previous studies in our laboratory have shown that α2 M is an Aβ binding protein. We now report that, in contrast to another plaque-associated protein, α1 -antichymotrypsin, α2 M coincubated with Aβ significantly reduces aggregation and fibril formation in vitro. Additionally, cultured fetal rat cortical neurons are less vulnerable to the toxic actions of aged Aβ following pretreatment with α2 M. We postulate that α2 M is able to maintain Aβ in a soluble state, preventing fibril formation and associated neurotoxicity. 相似文献
8.
Regulation of β1 -Adrenergic Receptor mRNA and Ligand Binding by Antidepressant Treatments and Norepinephrine Depletion in Rat Frontal Cortex 总被引:1,自引:1,他引:0
Abstract: The number of β1-adrenergic receptor (β1AR) binding sites is decreased by chronic antidepressant treatments, including electroconvulsive seizure (ECS) and imipramine, whereas administration of agents that deplete norepinephrine (NE) increases the number of β1AR binding sites in cerebral cortex. The present study was carried out to examine the influence of these treatments on levels of β1 AR mRNA in frontal cortex to study the molecular mechanisms that underlie the regulation of β1 ARs in brain. Levels of β1 AR mRNA were measured by RNase protection analysis using a riboprobe derived from rat β1AR cDNA, and the levels of βAR binding were measured using the nonselective ligand [3H]CGP-12177. Studies to verify the specificity of the RNase protection assay revealed that the distribution of β1AR mRNA was in agreement with the reported distribution of β1AR ligand binding: Levels of β1AR mRNA were highest in cerebral cortex or frontal cortex, intermediate in neostriatum, hippocampus, lung, and heart, and lowest in cerebellum, kidney, and liver. Chronic ECS treatment (once daily for 10 days) significantly decreased levels of βAR ligand binding and resulted in a corresponding, time-dependent down-regulation of β1AR mRNA levels in frontal cortex. However, imipramine administration regulated levels of β1AR mRNA in a biphasic manner, with treatments for 7–14 days increasing and treatments for 18–21 days decreasing levels of β1AR mRNA in frontal cortex. In contrast, levels of [3H]CGP-12177 ligand binding were decreased at all time points examined (3–21 days). The influence of NE depletion, using the neurotoxin 6-hydroxy-dopamine (6-OHDA), on levels of β1AR mRNA was also examined. Three days after 6-OHDA treatment, levels of [3H]CGP-12177 ligand binding were not altered, but 7–14 days after neurotoxin treatment, levels of ligand binding were significantly increased. In contrast, 3–9 days after 6-OHDA treatment, levels of β1AR mRNA were significantly decreased, and 14 days after treatment, levels of β1AR mRNA returned to control values. The results demonstrate that β1AR mRNA and ligand binding are regulated in parallel by ECS treatment but that levels of receptor mRNA are regulated in a complex manner by imipramine or 6-OHDA treatments, not predicted by changes in ligand binding. 相似文献
9.
Akiko Yamada Hidetoshi Akimoto Syota Kagawa Gilles J. Guillemin† Osamu Takikawa 《Journal of neurochemistry》2009,110(3):791-800
Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting enzyme of the kynurenine pathway of tryptophan metabolism, ultimately leading to production of the excitotoxin quinolinic acid (QUIN) by monocytic cells. In the Tg2576 mouse model of Alzheimer's disease, systemic inflammation induced by lipopolysaccharide leads to an increase in IDO expression and QUIN production in microglia surrounding amyloid plaques. We examined whether the IDO over-expression in microglia could be mediated by brain proinflammatory cytokines induced during the peripheral inflammation using THP-1 cells and peripheral blood mononuclear cells (PBMC) as models for microglia. THP-1 cells pre-treated with 5–25 μM amyloid β peptide (Aβ) (1–42) but not with Aβ (1–40) or Aβ (25–35) became an activated state as indicated by their morphological changes and enhanced adhesiveness. IDO expression was only slightly increased in the reactive cells but strongly enhanced following treatment with proinflammatory cytokine interferon-γ (IFN-γ) but not with interleukin-1β, tumor necrosis factor-α, or interleukin-6 at 100 U/mL. The concomitant addition of Aβ (1–42) with IFN-γ was totally ineffective, indicating that Aβ pre-treatment is prerequisite for a high IDO expression. The priming effect of Aβ (1–42) for the IDO induction was also observed for PBMC. These findings suggest that IFN-γ induces IDO over-expression in the primed microglia surrounding amyloid plaques. 相似文献
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