A11-positive &#946;-amyloid Oligomer Preparation and Assessment Using Dot Blotting Analysis

&#946;-amyloid (A&#946;) is a hydrophobic peptide with an intrinsic tendency to self-assemble into aggregates. Among various aggregates, A&#946; oligomer ...

Ningbo University

Post-operative cognitive dysfunction (POCD) is associated with elderly patients undergoing surgery. However, pharmacological treatments for POCD are limited. In this study, we found that curcumin, an active compound derived from Curcuma longa, ameliorated the cognitive dysfunction following abdominal surgery in aged mice. Further, curcumin prevented surgery-induced anti-oxidant enzyme activity. Curcumin also increased brain-derived neurotrophic factor (BDNF)-positive area and expression of pAkt in the brain, suggesting that curcumin activated BDNF signaling in aged mice. Furthermore, curcumin neutralized cholinergic dysfunction involving choline acetyltransferase expression induced by surgery. These results strongly suggested that curcumin prevented cognitive impairments via multiple targets, possibly by increasing the activity of anti-oxidant enzymes, activation of BDNF signaling, and neutralization of cholinergic dysfunction, concurrently. Based on these novel findings, curcumin might be a potential agent in POCD prophylaxis and treatment.

Curcumin attenuates surgery-induced cognitive dysfunction in aged mice.

Abstract: A new cyclopentenone, 5-hydroxycyclopeni cillone (1), was isolated together with three known compounds, ar-turmerone (2), citreoisocoumarin (3), and 6-O-methyl-citreoisocoumarin (4), from a culture of the sponge-derived fungus Trichoderma sp. HPQJ-34. The structures of 1-4 were characterized using comprehensive spectroscopic analyses. The absolute configuration of 1 was determined by comparison of electronic circular dichroism (ECD) spectra with literature values used for the reported analogue, cyclopenicillone (5), which was not isolated in this research. Compound 1 was shown to scavenge 2,2-diphenyl-1-picrylhydrazyl free radicals, and decrease β-amyloid (Aβ) fibrillization in vitro. Moreover, 1 significantly reduced H₂O₂-induced neurotoxicity in SH-SY5Y cells. These findings suggested that compound 1, a newly discovered cyclopentenone, has moderate anti-oxidative, anti-Aβ fibrillization properties and neuroprotective effects, and might be a good free radical scavenger.

5-Hydroxycyclopenicillone, a New β-Amyloid Fibrillization Inhibitor from a Sponge-Derived Fungus Trichoderma sp. HPQJ-34.

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by neurofibrillary tangles, synaptic impairments, and loss of neurons. Oligomers of β-amyloid (Aβ) are widely accepted as the main neurotoxins to induce oxidative stress and neuronal loss in AD. In this study, we discovered that fucoxanthin, a marine carotenoid with antioxidative stress properties, concentration dependently prevented Aβ oligomer-induced increase of neuronal apoptosis and intracellular reactive oxygen species in SH-SY5Y cells. Aβ oligomers inhibited the prosurvival phosphoinositide 3-kinase (PI3K)/Akt cascade and activated the proapoptotic extracellular signal-regulated kinase (ERK) pathway. Moreover, inhibitors of glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase (MEK) synergistically prevented Aβ oligomer-induced neuronal death, suggesting that the PI3K/Akt and ERK pathways might be involved in Aβ oligomer-induced neurotoxicity. Pretreatment with fucoxanthin significantly prevented Aβ oligomer-induced alteration of the PI3K/Akt and ERK pathways. Furthermore, LY294002 and wortmannin, two PI3K inhibitors, abolished the neuroprotective effects of fucoxanthin against Aβ oligomer-induced neurotoxicity. These results suggested that fucoxanthin might prevent Aβ oligomer-induced neuronal loss and oxidative stress via the activation of the PI3K/Akt cascade as well as inhibition of the ERK pathway, indicating that further studies of fucoxanthin and related compounds might lead to a useful treatment of AD.

Fucoxanthin, a Marine Carotenoid, Attenuates β-Amyloid Oligomer-Induced Neurotoxicity Possibly via Regulating the PI3K/Akt and the ERK Pathways in SH-SY5Y Cells.

The oligomer of β-amyloid (Aβ) is considered the main neurotoxin in Alzheimer's disease (AD). Therefore, the inhibition of the formation of Aβ oligomer could be a target for AD therapy. In this study, with the help of the dot blotting assay and transmission electronic microscopy, it was have discovered that 5-hydroxycyclopenicillone, a cyclopentenone recently isolated from a sponge-associated fungus, effectively reduced the formation of Aβ oligomer from Aβ peptide in vitro. Molecular dynamics simulations suggested hydrophobic interactions between 5-hydroxycyclopenicillone and Aβ peptide, which might prevent the conformational transition and oligomerization of Aβ peptide. Moreover, Aβ oligomer pre-incubated with 5-hydroxycyclopenicillone was less toxic when added to neuronal SH-SY5Y cells compared to the normal Aβ oligomer. Although 5-hydroxycyclopenicillone is not bioavailable in the brain in its current form, further modification or encapsulation of this chemical might improve the penetration of 5-hydroxycyclopenicillone into the brain. Based on the current findings and the anti-oxidative stress properties of 5-hydroxycyclopenicillone, it is suggested that 5-hydroxycyclopenicillone may have potential therapeutic efficacy in treating AD.

5-Hydroxycyclopenicillone Inhibits β-Amyloid Oligomerization and Produces Anti-β-Amyloid Neuroprotective Effects In Vitro.

Indirubins are natural occurring alkaloids extracted from indigo dye-containing plants. Indirubins could inhibit various kinases, and might be used to treat chronic myelocytic leukemia, cancer and neurodegenerative disorders. 7-bromoindirubin-3-oxime (7Bio), an indirubin derivative derived from indirubin-3-oxime, possesses inhibitory effects against cyclin-dependent kinase-5 (CDK5) and glycogen synthase kinase-3β (GSK3β), two pharmacological targets of Alzheimer's disease (AD). In this study, we have discovered that 2.3-23.3 μg/kg 7Bio effectively prevented β-amyloid (Aβ) oligomer-induced impairments of spatial cognition and recognition without affecting bodyweight and motor functions in mice. Moreover, 7Bio potently inhibited Aβ oligomer-induced expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Furthermore, 7Bio significantly prevented the decreased expression of synapsin-1 and PSD-95, biomarkers of pre-synaptic and post-synaptic proteins in Aβ oligomer-treated mice. The mean optical density (OD) with hyper-phosphorylated tau (pTau), glial fibrillary acidic protein (GFAP) and CD45 positive staining in the hippocampus of 7Bio-treated mice were significantly decreased compared to those of Aβ oligomer-treated mice. In addition, Western blotting analysis showed that 7Bio attenuated Aβ oligomer-decreased expression of pSer9-GSK3β. Those results suggested that 7Bio could potently inhibit Aβ oligomer-induced neuroinflammation, synaptic impairments, tau hyper-phosphorylation, and activation of astrocytes and microglia, which may contribute to the neuroprotective effects of 7Bio. Based on these findings, we expected that 7Bio might be developed as a novel anti-AD lead compound.

Indirubin Derivative 7-Bromoindirubin-3-Oxime (7Bio) Attenuates Aβ Oligomer-Induced Cognitive Impairments in Mice.

Alzheimer's disease is a progressive neurodegenerative disorder that mainly affects the elderly. Soluble β-amyloid oligomer, which can induce neurotoxicity, is generally regarded as the main neurotoxin in Alzheimer's disease. Here we report that eckmaxol, a phlorotannin extracted from the brown alga Ecklonia maxima, could produce neuroprotective effects in SH-SY5Y cells. Eckmaxol effectively prevented but did not rescue β-amyloid oligomer-induced neuronal apoptosis and increase of intracellular reactive oxygen species. Eckmaxol also significantly reversed the decreased expression of phospho-Ser9-glycogen synthase kinase 3β and increased expression of phospho-extracellular signal-regulated kinase, which was induced by Aβ oligomer. Moreover, both glycogen synthase kinase 3β and mitogen activated protein kinase inhibitors produced neuroprotective effects in SH-SY5Y cells. Furthermore, eckmaxol showed favorable interaction in the ATP binding site of glycogen synthase kinase 3β and mitogen activated protein kinase. These results suggested that eckmaxol might produce neuroprotective effects via concurrent inhibition of glycogen synthase kinase 3β and extracellular signal-regulated kinase pathways, possibly via directly acting on glycogen synthase kinase 3β and mitogen activated protein kinase. Based on the central role that β-amyloid oligomers play in the pathogenesis of Alzheimer's disease and the high annual production of Ecklonia maxima for alginate and other nutritional ingredients, this report represents a new candidate for the treatment of Alzheimer's disease, and also expands the potential application of Ecklonia maxima and its constituents in the field of pharmacology.

Eckmaxol, a Phlorotannin Extracted from Ecklonia maxima, Produces Anti-β-amyloid Oligomer Neuroprotective Effects Possibly via Directly Acting on Glycogen Synthase Kinase 3β.

Huang Chunhui

Ningbo University

A11-positive β-amyloid Oligomer Preparation and Assessment Using Dot Blotting Analysis