Benzofuranone derivatives as effective small molecules related to insulin amyloid fibrillation: a structure-function study

Synthesis and biological evaluation of 3-arylbenzofuranone derivatives as potential anti-Alzheimer's disease agents

Multi-target drugs can better address the cascade of events involved in oxidative stress and the reduction in cholinergic transmission that occur in Alzheimer’s disease than cholinesterase inhibitors alone. We synthesised a series of 3-arylbenzofuranone derivatives and evaluated their antioxidant activity, cholinesterase inhibitory activity, and monoamine oxidase inhibitory activity. 3-Arylbenzofuranone compounds exhibit good antioxidant activity as well as selective acetylcholinesterase inhibitory activity. The IC₅₀ value of anti-acetylcholinesterase inhibition of Compound 20 (0.089 ± 0.01 μM) is similar to the positive drug donepezil (0.059 ± 0.003 μM). According to the experimental results, Compounds 7, 13 show a certain effect in the in vitro evaluation performed and have the potential as drug candidates for the treatment of Alzheimer’s disease.

Insulin fibrillation: toward strategies for attenuating the process

The environmental factors affecting the rate of insulin fibrillation. The factors are representative.

Cuminaldehyde as the Major Component of Cuminum cyminum, a Natural Aldehyde with Inhibitory Effect on Alpha-Synuclein Fibrillation and Cytotoxicity

Fibrillation of alpha-synuclein (α-SN) is a critical process in the pathophysiology of several neurodegenerative diseases, especially Parkinson's disease. Application of bioactive inhibitory compounds from herbal extracts is a potential therapeutic approach for this cytotoxic process. Here, we investigated the inhibitory effects of the Iranian Cuminum cyminum essential oil on the fibrillation of α-SN. Analysis of different fractions from the total extract identified cuminaldehyde as the active compound involved in the antifibrillation activity. In comparison with baicalein, a well-known inhibitor of α-SN fibrillation, cuminaldehyde showed the same activity in some aspects and a different activity on other parameters influencing α-SN fibrillation. The presence of spermidine, an α-SN fibrillation inducer, dominantly enforced the inhibitory effects of cuminaldehyde even more intensively than baicalein. Furthermore, the results from experiments using preformed fibrils and monobromobimane-labeled monomeric protein also suggest that cuminaldehyde prevents α-SN fibrillation even in the presence of seeds, having no disaggregating impact on the preformed fibrils. Structural studies showed that cuminaldehyde stalls protein assembly into β-structural fibrils, which might be achieved by the interaction with amine groups through its aldehyde group as a Schiff base reaction. This assumption was supported by FITC labeling efficiency assay. In addition, cytotoxicity assays on PC12 cells showed that cuminaldehyde is a nontoxic compound, treatment with cuminaldehyde throughout α-SN fibrillation showed no toxic effects on the cells. Taken together, these results show for the first time that the small abundant natural compound, cuminaldehyde, can modulate α-SN fibrillation. Hence, suggesting that such natural active aldehyde could have potential therapeutic applications.

Injection of insulin amyloid fibrils in the hippocampus of male Wistar rats: report on memory impairment and formation of amyloid plaques

Amyloid fibrils result from a particular type of protein aggregation, and have been linked with various disorders, including neurodegenerative ones. In the case of Alzheimer's disease, amyloid beta (abeta) fibrils are detected in patients' brain, in the amyloid plaques. These fibrils can be produced in vitro, and their injection into animals' brains generates an animal model of Alzheimer's disease. Based on the structural similarity of amyloid fibrils that are formed from different proteins, we hypothesized that injecting insulin amyloid fibrils into rats' brains could result in amyloid plaque formation. Fourteen male Wistar rats were divided into control and experimental groups (n = 7). The experimental group was bilaterally injected with insulin amyloid in the hippocampus. Seven days after injection, a shuttle box test was performed and the experimental group's memory was found to be impaired. Histological investigation of these rats' brain showed the formation of amyloid plaques in the hippocampus. A limited test has provided preliminary evidence for the stability of these plaques up to 35 days. Further complementary studies are required to fully validate the proposed procedure, which is simple and relatively low cost, and could be suggested as an alternative to models generated with abeta fibrils.

The antihypersensitive and antiinflammatory activities of a benzofuranone derivative in different experimental models in mice: the importance of the protein kinase C pathway

BACKGROUND

Benzofuranone (BF1) was synthesized and its effects evaluated on mechanical hypersensitivity and paw edema models induced by different agents and on neuropathic pain induced by partial ligation of the sciatic nerve. An attempt was also made to elucidate the mechanism of action.

METHODS

Swiss mice were used for the tests. Hypersensitivity was induced by intraplantar injection of carrageenan, bradykinin (BK), prostaglandin E2 (PGE2), epinephrine, lipopolysaccharide, or complete Freund adjuvant or by using a neuropathic pain model (evaluated with von Frey filament 0.6 g). The antiinflammatory effects were investigated in a paw edema model induced by carrageenan, PGE2, and BK (measured with a plethysmometer). The involvement of protein kinase C (PKC) was investigated through a nociception model induced by phorbol myristate acetate.

RESULTS

BF1 inhibited the hypersensitivity and paw edema induced by intraplantar injection of carrageenan, BK, and PGE2 (P < 0.001), and it was effective in reducing the hypersensitivity evoked by complete Freund adjuvant or epinephrine (P < 0.001) but not by lipopolysaccharide (P = 0.2570). BF1 inhibited the licking behavior induced by phorbol myristate acetate (P < 0.001), suggesting involvement of the PKC pathway. A reduction in hypersensitivity of mice submitted to partial ligation of the sciatic nerve (P < 0.001) was observed, with inhibition of neutrophil migration and interleukin-1β production into the spinal cord. BF1 treatment did not interfere with locomotor activity (P = 0.0783) and thermal withdrawal threshold (P = 0.5953), which are important adverse effects of other analgesics.

CONCLUSIONS

BF1 has dose-dependent antihypersensitive and antiinflammatory effects in both acute and chronic models of pain and inflammation, possibly mediated through interference with the PKC activation pathway. The easy and fast synthesis of this compound, low-cost, low-concentration-requirement, and once-daily-administration drug suggest it as a candidate for future clinical studies.

Use of a small peptide fragment as an inhibitor of insulin fibrillation process: a study by high and low resolution spectroscopy

A non-toxic, nine residue peptide, NIVNVSLVK is shown to interfere with insulin fibrillation by various biophysical methods. Insulin undergoes conformational changes under certain stress conditions leading to amyloid fibrils. Fibrillation of insulin poses a problem in its long-term storage, reducing its efficacy in treating type II diabetes. The dissociation of insulin oligomer to monomer is the key step for the onset of fibrillation. The time course of insulin fibrillation at 62°C using Thioflavin T fluorescence shows an increase in the lag time from 120 min without peptide to 236 min with peptide. Transmission electron micrographs show branched insulin fibrils in its absence and less inter-fibril association in its presence. Upon incubation at 62°C and pH 2.6, insulin lost some α-helical structure as seen by Fourier transformed infra-red spectroscopy (FT-IR), but if the peptide is added, secondary structure is almost fully maintained for 3 h, though lost partially at 4 h. FT-IR spectroscopy also shows that insulin forms the cross beta structure indicative of fibrils beyond 2 h, but in the presence of the peptide, α-helix retention is seen till 4 h. Both size exclusion chromatography and dynamic light scattering show that insulin primarily exists as trimer, whose conversion to a monomer is resisted by the peptide. Saturation transfer difference nuclear magnetic resonance confirms that the hydrophobic residues in the peptide are in close contact with an insulin hydrophobic groove. Molecular dynamics simulations in conjunction with principal component analyses reveal how the peptide interrupts insulin fibrillation. In vitro hemolytic activity of the peptide showed insignificant cytotoxicity against HT1080 cells. The insulin aggregation is probed due to the inter play of two key residues, Phe(B24) and Tyr(B26) monitored from molecular dynamics simulations studies. Further new peptide based leads may be developed from this nine residue peptide.

Syntheses and structure-activity relationships of seven manganese-salen derivatives as anti-amyloidogenic and fibril-destabilizing agents against hen egg-white lysozyme aggregation

Accumulation of intra- and/or extracellular misfolded proteins as amyloid fibrils is a key hallmark in more than 20 amyloid-related diseases. In that respect, blocking or reversing amyloid aggregation via the use of small compounds is considered as two useful approaches in hampering the development of these diseases. In this research, we have studied the ability of different manganese-salen derivatives to inhibit amyloid self-assembly as well as to dissolve amyloid aggregates of hen egg-white lysozyme, as an in vitro model system, with the aim of investigating their structure-activity relationships. By coupling several techniques such as thioflavin T and anilinonaphthalene-8-sulfonic acid fluorescence, congo red absorbance, far-UV circular dichroism, and transmission electron microscopy, we demonstrated that all compounds possessed anti-amyloidogenic activities and were capable of dispersing the fibrillar aggregates. In addition, MTT assay of the treated SK-N-MC cells with the preformed fibrils formed in the presence of compounds at a drug-to-protein molar ratio of 5:1, indicated a significant increase in the viability of cells, compared to the fibrils formed in the absence of each of the compounds. Our spectroscopy, electron microscopy, and cellular studies indicated that EUK-15, with a methoxy group at the para position (group R(5)), had higher activity to either inhibit or disrupt the β-sheet structures relative to other compounds. On the basis of these results, it can be concluded that in addition to aromatic rings of each of the derivatives, the type and position of the side group(s) contribute to lower lysozyme fibril accumulation.