scholarly journals Glucocorticoids Facilitate Astrocytic Amyloid-β Peptide Deposition by Increasing the Expression of APP and BACE1 and Decreasing the Expression of Amyloid-β-Degrading Proteases

Endocrinology ◽  
2011 ◽  
Vol 152 (7) ◽  
pp. 2704-2715 ◽  
Author(s):  
Yanyan Wang ◽  
Maoquan Li ◽  
Jun Tang ◽  
Min Song ◽  
Xueqing Xu ◽  
...  
Keyword(s):  
Molecular Mechanism ◽  
Primary Cultures ◽  
Amyloid Β ◽  
The Elderly ◽  
Stress Factors ◽  
Amyloid Β Peptide ◽  
Insulin Degrading Enzyme ◽  
Basal Cortisol ◽  
Metalloproteinase 9

In most cases, the molecular mechanism underlying the pathogenesis of sporadic Alzheimer's disease (AD) is unknown. Elevated basal cortisol levels in AD patients suggest that glucocorticoids (GC) may contribute to the development and/or maintenance of AD. Amyloid plaques are the hallmark of AD, and they are considered to play an early role in the AD process. However, little is known about how their formation is regulated by stress and GC. Astrocyte accumulation is one of the earliest neuropathological changes in AD. Here, we report that GC elevated amyloid-β (Aβ) production in primary cultures of astrocytes by increasing amyloid precursor protein (APP) and β-site APP-cleaving enzyme 1 gene expression. Notably, GC administered to normal, middle-aged mice promoted the expression of APP and β-site APP-cleaving enzyme 1 in astrocytes, as determined by double immunofluorescence. Additionally, confocal microscopy and ELISA revealed that GC markedly reduced Aβ degradation and clearance by astrocytes in vitro, indicating a decreased neuroprotective capacity of the astrocytes. This may have been due to the decrease of several Aβ-degrading proteases, such as insulin-degrading enzyme and matrix metalloproteinase-9. These effects occurred through the activation of GC receptors. Taken together, our results demonstrate that GC can enhance the production of Aβ, reduce its degradation in astrocytes, and provide a molecular mechanism linking stress factors to AD. Our study suggests that GC can facilitate AD pathogenesis and that reducing GC in the elderly and early AD patients would be beneficial.

Amyloid β peptide cleavage by kallikrein 7 attenuates fibril growth and rescues neurons from Aβ-mediated toxicity in vitro

2014 ◽  
Vol 395 (1) ◽  
pp. 109-118 ◽  
Author(s):  
Tyler D. Shropshire ◽  
Jack Reifert ◽  
Sridharan Rajagopalan ◽  
David Baker ◽  
Stuart C. Feinstein ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Amyloid Β ◽  
Amyloid Β Peptide ◽  
Hydrophobic Core ◽  
Insulin Degrading Enzyme ◽  
Core Motif ◽  
Peptide Cleavage ◽  
Bacterial Display ◽  
Clearance Mechanism

Abstract The gradual accumulation and assembly of β-amyloid (Aβ) peptide into neuritic plaques is a major pathological hallmark of Alzheimer disease (AD). Proteolytic degradation of Aβ is an important clearance mechanism under normal circumstances, and it has been found to be compromised in those with AD. Here, the extended substrate specificity and Aβ-degrading capacity of kallikrein 7 (KLK7), a serine protease with a unique chymotrypsin-like specificity, was characterized. Preferred peptide substrates of KLK7 identified using a bacterial display substrate library were found to exhibit a consensus motif of RXΦ(Y/F)↓(Y/F)↓(S/A/G/T) or RXΦ(Y/F)↓(S/T/A) (Φ=hydrophobic), which is remarkably similar to the hydrophobic core motif of Aβ (K16L17V18F19F20 A21) that is largely responsible for aggregation propensity. KLK7 was found to cleave after both Phe residues within the core of Aβ42 in vitro, thereby inhibiting Aβ fibril formation and promoting the degradation of preformed fibrils. Finally, the treatment of Aβ oligomer preparations with KLK7, but not inactive pro-KLK7, significantly reduced Aβ42-mediated toxicity to rat hippocampal neurons to the same extent as the known Aβ-degrading protease insulin-degrading enzyme (IDE). Taken together, these results indicate that KLK7 possesses an Aβ-degrading capacity that can ameliorate the toxic effects of the aggregated peptide in vitro.

Phenolic Acids Exert Anticholinesterase and Cognition-Improving Effects

2018 ◽  
Vol 15 (6) ◽  
pp. 531-543 ◽  
Author(s):  
Dominik Szwajgier ◽  
Ewa Baranowska-Wojcik ◽  
Kamila Borowiec
Keyword(s):  
Phenolic Acids ◽  
Ex Vivo ◽  
Amyloid Β ◽  
Inhibitory Effect ◽  
In Vivo Studies ◽  
Amyloid Β Peptide ◽  
Beneficial Effects ◽  
Aβ Fibrils

Numerous authors have provided evidence regarding the beneficial effects of phenolic acids and their derivatives against Alzheimer's disease (AD). In this review, the role of phenolic acids as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is discussed, including the structure-activity relationship. In addition, the inhibitory effect of phenolic acids on the formation of amyloid β-peptide (Aβ) fibrils is presented. We also cover the in vitro, ex vivo, and in vivo studies concerning the prevention and treatment of the cognitive enhancement.

scholarly journals Repeated electromagnetic field stimulation lowers amyloid-β peptide levels in primary human mixed brain tissue cultures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Felipe P. Perez ◽  
Bryan Maloney ◽  
Nipun Chopra ◽  
Jorge J. Morisaki ◽  
Debomoy K. Lahiri
Keyword(s):  
Electromagnetic Field ◽  
Late Onset ◽  
Amyloid Β ◽  
Clinical Settings ◽  
Amyloid Β Peptide ◽  
Field Stimulation ◽  
Amino Acid Residues ◽  
Hyperphosphorylated Tau Protein ◽  
Magnetic Resonance Imaging Mri

AbstractLate Onset Alzheimer’s Disease is the most common cause of dementia, characterized by extracellular deposition of plaques primarily of amyloid-β (Aβ) peptide and tangles primarily of hyperphosphorylated tau protein. We present data to suggest a noninvasive strategy to decrease potentially toxic Aβ levels, using repeated electromagnetic field stimulation (REMFS) in primary human brain (PHB) cultures. We examined effects of REMFS on Aβ levels (Aβ40 and Aβ42, that are 40 or 42 amino acid residues in length, respectively) in PHB cultures at different frequencies, powers, and specific absorption rates (SAR). PHB cultures at day in vitro 7 (DIV7) treated with 64 MHz, and 1 hour daily for 14 days (DIV 21) had significantly reduced levels of secreted Aβ40 (p = 001) and Aβ42 (p = 0.029) peptides, compared to untreated cultures. PHB cultures (DIV7) treated at 64 MHz, for 1 or 2 hour during 14 days also produced significantly lower Aβ levels. PHB cultures (DIV28) treated with 64 MHz 1 hour/day during 4 or 8 days produced a similar significant reduction in Aβ40 levels. 0.4 W/kg was the minimum SAR required to produce a biological effect. Exposure did not result in cellular toxicity nor significant changes in secreted Aβ precursor protein-α (sAPPα) levels, suggesting the decrease in Aβ did not likely result from redirection toward the α-secretase pathway. EMF frequency and power used in our work is utilized in human magnetic resonance imaging (MRI, thus suggesting REMFS can be further developed in clinical settings to modulate Aβ deposition.

Effects of Hydrated Forms of C60 Fullerene on Amyloid β-Peptide Fibrillization In Vitro and Performance of the Cognitive Task

2007 ◽  
Vol 7 (4) ◽  
pp. 1479-1485 ◽  
Author(s):  
I. Ya. Podolski ◽  
Z. A. Podlubnaya ◽  
E. A. Kosenko ◽  
E. A. Mugantseva ◽  
E. G. Makarova ◽  
...  
Keyword(s):  
Cognitive Task ◽  
Amyloid Β ◽  
C60 Fullerene ◽  
Amyloid Β Peptide ◽  
And Performance

Gallotannins and Tannic Acid: First Chemical Syntheses and In Vitro Inhibitory Activity on Alzheimer’s Amyloid β-Peptide Aggregation

2015 ◽  
Vol 54 (28) ◽  
pp. 8217-8221 ◽  
Author(s):  
Tahiri Sylla ◽  
Laurent Pouységu ◽  
Grégory Da Costa ◽  
Denis Deffieux ◽  
Jean-Pierre Monti ◽  
...  
Keyword(s):  
Tannic Acid ◽  
Inhibitory Activity ◽  
Amyloid Β ◽  
Amyloid Β Peptide ◽  
Peptide Aggregation
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