Crocus-derived compounds alter the aggregation pathway of Alzheimer's Disease: associated beta amyloid protein.

Natural products have played a dominant role in the discovery of lead compounds for the development of drugs aimed at the treatment of human diseases. This electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS)-based study demonstrates that dietary antioxidants, isolated components from the stigmas of saffron (Crocus sativus L.) may be effective in inhibiting Aß fibrillogenesis, a neuropathological hallmark of Alzheimer's Disease (AD). This study reveals a substantial alteration in the monomer/oligomer distribution of Aß1-40, concomitant with re-direction of fibril formation, induced by the natural product interaction. These alterations on the Aß1-40 aggregation pathway are most prominent for trans-crocin-4 (TC4). Use of ESI-IMS-MS, electron microscopy alongside Thioflavin-T kinetics, and the interpretation of 3-dimensional Driftscope plots indicate a correlation of these monomer/oligomer distribution changes with alterations to Aß1-40 amyloid formation. The latter could prove instrumental in the development of novel aggregation inhibitors for the prevention, or treatment of AD.

Baicalin prevents the production of hydrogen peroxide and oxidative stress induced by Aß aggregation in SH-SY5Y cells.

Alzheimer's disease (AD) is a common form of neurodegenerative disease. Mounting evidence suggests that metal ions play a key role in the aggregation of amyloid ß peptide (Aß), which acts as a factor or cofactor in the etiopathogenesis of AD. Therefore, inhibition of Aß aggregation emerges as a potential approach for the treatment of AD. We have found that baicalin can interact with copper directly and inhibits Aß1-42 aggregation. In addition, baicalin protects SH-SY5Y cells from oxidative injuries induced by Aß1-42 aggregation through decreasing H(2)O(2) production that is normally formed as a deleterious by-product of beta amyloid aggregation and the formation of plaques. Taken together, these data indicate that baicalin may be a potential agent to inhibit Aß aggregation and thereby delay, mitigate or modify the progression of neurodegenerative diseases such as AD.

Insights into the oligomerization process of the C-terminal domain of human plasma membrane Ca²+-ATPase.

Plasma membrane calcium pumps (PMCAs) sustain a primary transport system for the specific removal of cytosolic calcium ions from eukaryotic cells. PMCAs are characterized by the presence of a C-terminal domain referred to as a regulatory domain. This domain is target of several regulatory mechanisms: activation by Ca²+-calmodulin complex and acidic phospholipids, phosphorylation by kinase A and C, proteolysis by calpain and oligomerization. As far as oligomerization is concerned, the C-terminal domain seems to be crucial for this process. We have cloned the C-terminal domain of the human PMCA isoform 1b, and characterized its properties in solution. The expressed protein maintains its tendency to oligomerize in aqueous solutions, but it is dissociated by amphipathic molecules such as diacylglycerol and sodium dodecyl sulphate. The presence of sodium dodecyl sulphate stabilizes the domain as a compact structure in monomeric form retaining the secondary structure elements, as shown by small angle neutron scattering and circular dichroism measurements. The importance of oligomerization for the regulation of PMCA activity and intracellular calcium concentration is discussed.

Truncated beta-amyloid peptide channels provide an alternative mechanism for Alzheimer's Disease and Down syndrome.

Full-length amyloid beta peptides (Abeta(1-40/42)) form neuritic amyloid plaques in Alzheimer's disease (AD) patients and are implicated in AD pathology. However, recent transgenic animal models cast doubt on their direct role in AD pathology. Nonamyloidogenic truncated amyloid-beta fragments (Abeta(11-42) and Abeta(17-42)) are also found in amyloid plaques of AD and in the preamyloid lesions of Down syndrome, a model system for early-onset AD study. Very little is known about the structure and activity of these smaller peptides, although they could be the primary AD and Down syndrome pathological agents. Using complementary techniques of molecular dynamics simulations, atomic force microscopy, channel conductance measurements, calcium imaging, neuritic degeneration, and cell death assays, we show that nonamyloidogenic Abeta(9-42) and Abeta(17-42) peptides form ion channels with loosely attached subunits and elicit single-channel conductances. The subunits appear mobile, suggesting insertion of small oligomers, followed by dynamic channel assembly and dissociation. These channels allow calcium uptake in amyloid precursor protein-deficient cells. The channel mediated calcium uptake induces neurite degeneration in human cortical neurons. Channel conductance, calcium uptake, and neurite degeneration are selectively inhibited by zinc, a blocker of amyloid ion channel activity. Thus, truncated Abeta fragments could account for undefined roles played by full length Abetas and provide a unique mechanism of AD and Down syndrome pathologies. The toxicity of nonamyloidogenic peptides via an ion channel mechanism necessitates a reevaluation of the current therapeutic approaches targeting the nonamyloidogenic pathway as avenue for AD treatment.

Influence of phosphorus dendrimers on the aggregation of the prion peptide PrP 185-208.

Inhibition of fibril assembly is a potential therapeutic strategy in prion diseases. The effect of cationic phosphorous dendrimers on the aggregation process of the prion peptide PrP 185-208 was studied using a spectrofluorometric assay with thioflavin T (ThT) and Fourier transformed infrared spectroscopy in order to monitor the kinetics of the process and the changes in the peptide secondary structure. The results show that phosphorous dendrimers are able to clearly interfere with PrP 185-208 aggregation process by both slowing down the formation of aggregates (by causing a decrease of the nucleation rate) and by lowering the final amount of amyloid fibrils, a common hallmark of conformational diseases. The dendrimers effect on the aggregation process would imply their interaction with peptide monomers and oligomers during the nucleation phase.

[Comparison of the inhibitory activities of salvianolic acid B and Ginkgo biloba extract EGb 761 on neurotoxicity of beta-amyloid peptide].

AIM: To compare the effects of salvianolic acid B (Sal B) and Ginkgo biloba extract EGb 761 on beta-amyloid peptide (beta-AP) fibril formation and cytotoxicity to PC12 cells. METHODS: The inhibitory effects of Sal B and EGb 761 on beta-AP1-40 fibril formation were determined by using fluorescence analysis with Thioflavin T (ThT) and electron microscopic image. beta-AP25-35 was aged by incubating at 37 degrees C for 7 d, then the protein was incubated with PC12 cells. The protective effects of Sal B and EGb 761 against cytotoxicity induced by aged beta-AP25-35 in PC12 cells were evaluated by MTT reduction assay and flow cytometric analysis. beta-AP25-35-induced accumulation of intracellular reactive oxygen species (ROS) was determined by fluorescence analysis. RESULTS: Both Sal B and EGb 761 inhibited the formation of amyloid fibrils, protected PC12 cells from beta-AP25-35-induced cytotoxicity, and decreased ROS accumulation caused by beta-AP25-35. The effective doses of Sal B were far lower than those of EGb 761. CONCLUSION: Sal B was much more efficient than EGb 761 in inhibiting beta-AP aggregation and in protecting PC12 cells from beta-AP-induced cytotoxicity.

[Inhibiting effect of ethanol extract from Achyranthes bidentata on A beta 42 aggregation].

OBJECTIVE: To observe inhibiting effect of ethanol extract from Achyranthes bidentata (Nx-E) on A beta 42 on (beta-amyloid protein 42) aggregation and fibril formation. METHODS: A beta 42 and Nx-E were incubated in 37 degrees C, 5%, CO2 incubator first, fibril formation was monitored by thioflavine-T fluorescence and was observed with transmission electron microscopy. RESULTS: At 7 days, 1 microgram.microL-1 A beta 42 fluorescence intensity was significantly increased, and much amyloid-like fibril was observed. A beta 42 co-incubated with 15 and 30 micrograms.microL-1 Nx-E for 7 days, their fluorescence intensities were remarkably reduced, few fibrils but an amorphous material were often observed. CONCLUSIONS: After 1 microgram.microL-1 A beta 42 was incubated alone up to 7 days, A beta 42 aggregated and amyloid-like fibril formed. 15 and 30 micrograms.microL-1 Nx-E can prevent A beta 42 from polymerizing to some extent.

Effect of ADP and ionic strength on the kinetic and motile properties of recombinant mouse myosin V.

Mouse myosin V is a two-headed unconventional myosin with an extended neck that binds six calmodulins. Double-headed (heavy meromyosin-like) and single-headed (subfragment 1-like) fragments of mouse myosin V were expressed in Sf9 cells, and intact myosin V was purified from mouse brain. The actin-activated MgATPase of the tissue-purified myosin V, and its expressed fragments had a high V(max) and a low K(ATPase). Calcium regulated the MgATPase of intact myosin V but not of the fragments. Both the MgATPase activity and the in vitro motility were remarkably insensitive to ionic strength. Myosin V and its fragments translocated actin at very low myosin surface densities. ADP markedly inhibited the actin-activated MgATPase activity and the in vitro motility. ADP dissociated from myosin V subfragment 1 at a rate of about 11.5 s(-1) under conditions where the V(max) was 3.3 s(-1), indicating that, although not totally rate-limiting, ADP dissociation was close to the rate-limiting step. The high affinity for actin and the slow rate of ADP release helps the myosin head to remain attached to actin for a large fraction of each ATPase cycle and allows actin filaments to be moved by only a few myosin V molecules in vitro.

Inhibition of fibril formation in beta-amyloid peptide by a novel series of benzofurans.

A series of benzofuran derivatives have been identified as inhibitors of fibril formation in the beta-amyloid peptide. The activity of these compounds has been assessed by a novel fibril-formation-specific immunoassay and for their effects on the production of a biologically active fibril product. The inhibition afforded by the compounds seems to be associated with their binding to beta-amyloid, as identified by scintillation proximity binding assay. Binding assays and NMR studies also indicate that the inhibition is associated with self-aggregation of the compounds. There is a close correlation between the activity of the benzofurans as inhibitors of fibril formation and their ability to bind to beta-amyloid. Non-benzofuran inhibitors of the fibril formation process do not seem to bind to the same site on the beta-amyloid molecule as the benzofurans. Thus a specific recognition site might exist for benzofurans on beta-amyloid, binding to which seems to interfere with the ability of the peptide to form fibrils.