Aminostyrylbenzofuran derivatives as potent inhibitors for Aβ fibril formation

Dual-target inhibitors based on acetylcholinesterase: Novel agents for Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia among the elderly, accounting for 60 %-70 % of cases. At present, the pathogenesis of this condition remains unclear, but the hydrolysis of acetylcholine (ACh) is thought to play a role. Acetylcholinesterase (AChE) can break down ACh transmission from the presynaptic membrane and stop neurotransmitters' excitatory effect on the postsynaptic membrane, which plays a key role in nerve conduction. Acetylcholinesterase inhibitors (AChEIs) can delay the hydrolysis of acetylcholine (ACh), which represents a key strategy for treating AD. Due to its complex etiology, AD has proven challenging to treat. Various inhibitors and antagonists targeting key enzymes and proteins implicated in the disease's pathogenesis have been explored as potential therapeutic agents. These include Glycogen Synthase Kinase 3β (GSK-3β) inhibitors, β-site APP Cleaving Enzyme (BACE-1) inhibitors, Monoamine Oxidase (MAO) inhibitors, Phosphodiesterase inhibitors (PDEs), N-methyl--aspartic Acid (NMDA) antagonists, Histamine 3 receptor antagonists (H3R), Serotonin receptor subtype 4 (5-HT4R) antagonists, Sigma1 receptor antagonists (S1R) and soluble Epoxide Hydrolase (sEH) inhibitors. The drug development strategy of multi-target-directed ligands (MTDLs) offers unique advantages in the treatment of complex diseases. On the one hand, it can synergistically enhance the therapeutic efficacy of single-target drugs. On the other hand, it can also reduce the side effects. In this review, we discuss the design strategy of dual inhibitors based on acetylcholinesterase and the structure-activity relationship of these drugs.

Nickel-Catalyzed Regioselectivity-Switchable Hydroheteroarylation of Vinylarenes with Electron-Rich Heteroarenes

We report the first example of a regioselectivity switch in the hydroheteroarylation of vinylarenes with electron-rich heteroarenes, including benzofurans, benzothiophenes, and indoles, using an expedient ligand-controlled strategy. In the presence of NaOtBu, Ni(IMesMe)[P(OEt)3]Br2 yields C2-alkylated heteroarenes with high branched selectivity, whereas the use of Ni(IPr*OMe)[P(OEt)3]Br2 favors the formation of the corresponding linear products. This robust method also provides easy access to a range of C2-alkylated electron-rich heteroarenes without employing directing groups.

Benzo[d]imidazole-pyrrolo[1,2-a]pyrazine Hybrids Ameliorate Amyloid Aggregates in the Brain of Alzheimer Transgenic Mice

Abnormal assembly of amyloid β (Aβ) in the brain is implicated in Alzheimer's disease (AD) and is associated with cognitive impairments. Since Aβ accumulation occurs in advance of the onset of clinical symptoms, identifying preventable drug candidates regulating Aβ accumulation is regarded as a promising approach in AD therapeutic. Herein, we synthesized eight Yonsei Institute of pharmaceutical sciences Alzheimer's Drug (YIAD) compounds based on 5-benzyl-6-phenylbenzo[4,5]imidazo[1,2-a]pyrrolo[2,1-c]pyrazine structures. Subsequently, YIAD-0203 and YIAD-0205 were selected as effective candidates via thioflavin T assays and gel electrophoresis. The potential therapeutic effect of YIAD-0203 and YIAD-0205 on Aβ aggregates was investigated through an AD transgenic mouse model with five familial AD mutations (5XFAD) by oral gavage. Significant amounts of Aβ plaque and oligomer reduction were observed in the hippocampus region of both 4.3-month-old (early stage of AD) and 6.0-month-old (mid stage of AD) YIAD-0205-treated 5XFAD mice brains when compared to the nontreated brains. The ability of YIAD-0205 to ameliorate Aβ aggregates in the early and mid stages of AD progression supports the notion that YIAD-0205 could be utilized as a reliable scaffold for the development of preventive AD drug candidates.

Novel 3-aminobenzofuran derivatives as multifunctional agents for the treatment of Alzheimer’s disease

A novel multifunctional series of 3-aminobenzofuran derivatives 5a-p were designed and synthesized as potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The target compounds 5a-p were prepared via a three-step reaction, starting from 2-hydroxy benzonitrile. In vitro anti-cholinesterase activity exhibited that most of the compounds had potent acetyl- and butyrylcholinesterase inhibitory activity. In particular, compound 5f containing 2-fluorobenzyl moiety showed the best inhibitory activity. Furthermore, this compound showed activity on self- and AChE-induced Aβ-aggregation and MTT assay against PC12 cells. The kinetic study revealed that compound 5f showed mixed-type inhibition on AChE. Based on these results, compound 5f can be considered as a novel multifunctional structural unit against Alzheimer’s disease.

Design and synthesis of novel chalcone derivatives and evaluation of their inhibitory activities against acetylcholinesterase

According to the cholinergic hypothesis, an increase in the acetylcholine level in Alzheimer's disease patients relatively slows down the symptoms of the disease. The most commonly used drug, donepezil, is a cholinesterase inhibitor. In this study, 12 new chalcones (2a-l) were designed and synthesized. In biological activity studies, the acetylcholinesterase (AChE) and butyrylcholinesterase inhibitory potentials of all compounds were evaluated using the in vitro Ellman method. The biological evaluation showed that compounds 2d, 2f, 2j, and 2l displayed significant activity against AChE. The compounds 2d, 2f, 2j, and 2l displayed IC₅₀ values of 0.042, 0.024, 0.053, and 0.033 µM against AChE, respectively. The reference drug donepezil (IC₅₀  = 0.021 µM) also displayed significant inhibition of AChE. The inhibitory activities of these compounds for β-amyloid plaque aggregation were investigated. The enzyme kinetic study was performed to observe the effect of the most active compound 2f on the substrate-enzyme relationship, and a mixed-type inhibition of AchE was determined. Further, docking simulation also revealed that these compounds (2d, 2f, 2j, and 2l) interacted with the enzyme active site in a similar manner to donepezil. The most active derivative, compound 2f, interacted with the amino acids Trp286, Phe295, Tyr341, Trp86, and Glu202.

Synthesis, biological evaluation and molecular modeling of benzofuran piperidine derivatives as Aβ antiaggregant

A series of benzofuran piperidine derivatives were designed, synthesized and evaluated as multifunctional Aβ antiaggregant to treat Alzheimer's disease (AD). In vitro results revealed that all of them are very good Aβ antiaggregants and some of the compounds are potent acetylcholinesterase (AChE) inhibitors with moderate antioxidant property. Selected compounds were also tested for neuroprotection activity, LDH release, ATP production and inhibitory activity to prevent Aβ peptides binding to the cell membrane. The different modifications introduced in the structure of our lead compound 3 (hAChE IC₅₀ = 61 μM and self induced Aβ _25-35 aggregation 45.45%), to increase its activity toward AD related targets. The most interesting multifunctional Aβ antiaggregants were compounds 3a, 3h and 3i, highlighting 3h as potent Aβ antiaggregant and good antiacetylholinesterase inhibitor (self induced Aβ _25-35 aggregation 57.71% and hAChE IC₅₀ = 21 μM), with good neuroprotective and antioxidant activity. In addition, these three most promising compounds prevent intracellular reactive oxygen species (ROS) formation and cell apoptosis induced by Aβ_25-35 peptides in SH-SY5Y cells. Molecular docking studies were also accomplished to understand the binding interaction of these compounds on Aβ monomer, Aβ fibril and AChE. Based on all data, compounds 3a, 3h and 3i were concluded as potent multifunctional Aβ antiaggregant, useful candidate for the treatment of AD.

Amyloid binding and beyond: a new approach for Alzheimer's disease drug discovery targeting Aβo-PrPC binding and downstream pathways

Amyloid β oligomers (Aβo) are the main toxic species in Alzheimer's disease, which have been targeted for single drug treatment with very little success. In this work we report a new approach for identifying functional Aβo binding compounds. A tailored library of 971 fluorine containing compounds was selected by a computational method, developed to generate molecular diversity. These compounds were screened for Aβo binding by a combined 19F and STD NMR technique. Six hits were evaluated in three parallel biochemical and functional assays. Two compounds disrupted Aβo binding to its receptor PrPC in HEK293 cells. They reduced the pFyn levels triggered by Aβo treatment in neuroprogenitor cells derived from human induced pluripotent stem cells (hiPSC). Inhibitory effects on pTau production in cortical neurons derived from hiPSC were also observed. These drug-like compounds connect three of the pillars in Alzheimer's disease pathology, i.e. prion, Aβ and Tau, affecting three different pathways through specific binding to Aβo and are, indeed, promising candidates for further development.

Fluorescence Detection of Type III Secretion Using a Glu-CyFur Reporter System in Citrobacter rodentium

Enteropathogenic Escherichia coli (EPEC) is a major cause of infantile diarrhea worldwide. EPEC and the closely related murine model of EPEC infection, Citrobacter rodentium, utilize a type III secretion system (T3SS) to propagate the infection. Since the T3SS is not essential for the bacteria to survive or propagate, inhibiting the virulence factor with a therapeutic would treat the infection without causing harm to commensal bacteria. Studying inhibitors of the T3SS usually requires a BSL-2 laboratory designation and eukaryotic host cells while not indicating the mechanism of inhibition. We have designed a BSL-1 assay using the murine model C. rodentium that does not require mammalian cell culture. This CPG2-reporter assay allows for more rapid analysis of secretion efficiency than Western blotting and is sensitive enough to differentiate between partial and total inhibition of the T3SS. Here we present our method and the results of a small collection of compounds we have screened, including known T3SS inhibitors EGCG, regacin, and aurodox and related quorum sensing inhibitors tannic acid and ellagic acid. We have further characterized EGCG as a T3SS inhibitor and established its IC₅₀ of 1.8 ± 0.4 μM. We also establish tannic acid as a potent inhibitor of the T3SS with an IC₅₀ of 0.65 ± 0.09 μM.

Discovery and Characterization of Novel Naphthalimide Analogs as Potent Multitargeted Directed Ligands against Alzheimer's Disease

Current therapeutic drugs for Alzheimer's disease (AD) can only offer limited symptomatic benefits and do not halt disease progression. Multitargeted directed ligands (MTDLs) have been considered to be a feasible way to treat AD due to the multiple neuropathological processes in AD. Previous studies proposed that compounds containing two aromatic groups connected by a carbon chain should act as effective amyloid β (Aβ) aggregation inhibitors although the optimal length of the carbon chain has not been explored. In the current study, a series of naphthalimide analogs were designed and synthesized based on the proposed structure and multiple bioactivities beneficial to the AD treatment were reported. In vitro studies showed that compound 8, which has two aromatic groups connected by a two-carbon chain, exhibited significant inhibition of Aβ aggregation through the prevention of elongation and association of Aβ fibril growth. Furthermore, this compound also displayed antioxidative activities and neuroprotection from Aβ monomer induced toxicity in primary cortical neurons. The results of the present study highlight a novel naphthalimide-based compound 8 as a promising MTDL against AD. Its structural elements can be further explored for enhanced therapeutic capabilities.

Synthesis and biological evaluation of novel shikonin-benzo[b]furan derivatives as tubulin polymerization inhibitors targeting the colchicine binding site

A novel series of shikonin-benzo[b]furan derivatives were designed and synthesized as tubulin polymerization inhibitors, and their biological activities were evaluated. Most compounds revealed the comparable anti-proliferation activities against the cancer cell lines to that of shikonin and simultaneously low cytotoxicity to non-cancer cells. Among them, compound 6c displayed powerful anti-cancer activity with the IC₅₀ value of 0.18 μM against HT29 cells, which was significantly better than that of the reference drugs shikonin and CA-4. What's more, 6c could inhibit tubulin polymerization and compete with [³H] colchicine in binding to tubulin. Further biological studies depicted that 6c can induce cell apoptosis and cell mitochondria depolarize, regulate the expression of apoptosis related proteins in HT29 cells. Besides, 6c actuated the HT29 cell cycle arrest at G2/M phase, and influenced the expression of the cell-cycle related protein. Moreover, 6c displayed potent inhibition on cell migration and tube formation that contributes to the antiangiogenesis. These results prompt us to consider 6c as a potential tubulin polymerization inhibitor and is worthy for further study.

Insight into the PTP1B Inhibitory Activity of Arylbenzofurans: An In Vitro and In Silico Study

Protein tyrosine phosphatase 1B (PTP1B) plays a specific role as a negative regulator of insulin signaling pathways and is a validated therapeutic target for Type 2 diabetes. Previously, arylbenzofurans were reported to have inhibitory activity against PTP1B. However, detailed investigation regarding their structure activity relationship (SAR) has not been elucidated. The main aim of this work was to investigate the PTP1B inhibitory activity of 2-arylbenzofuran analogs (sanggenofuran A (SA), mulberrofuran D2 (MD2), mulberrofuran D (MD), morusalfuran B (MB), mulberrofuran H (MH)) isolated from the root bark of Morus alba. All compounds demonstrated potent inhibitory activity with IC₅₀ values ranging from 3.11 to 53.47 µM. Among the tested compounds, MD2 showed the strongest activity (IC₅₀, 3.11 µM), followed by MD and MB, while SA and MH demonstrated the lowest activity. Lineweaver-Burk and Dixon plots were used for the determination of inhibition type whereas ligand and receptor interactions were investigated in modeled complexes via molecular docking. Our study clearly supports 2-arylbenzofuran analogs as a promising class of PTP1B inhibitors and illustrates the key positions responsible for the inhibitory activity, their correlation, the effect of prenyl/geranyl groups, and the influence of resorcinol scaffold, which can be further explored in-depth to develop therapeutic agents against T2DM.

Inhibitory effects of oxidovanadium complexes on the aggregation of human islet amyloid polypeptide and its fragments

Human islet amyloid polypeptide (hIAPP) is synthesized by pancreatic β-cells and co-secreted with insulin. Misfolding and amyloidosis of hIAPP induce β-cell dysfunction in type II diabetes mellitus. Numerous small organic molecules and metal complexes act as inhibitors against amyloid-related diseases, justifying the need to explore the inhibitory mechanism of these compounds. In this work, three oxidovanadium complexes, namely, (NH₄)[VO(O₂)₂(bipy)]·4H₂O (1) (bipy = 2,2' bipyridine), bis(ethyl-maltolato, O,O)oxido-vanadium(IV) (2), and (bipyH₂)H₂[O{VO(O₂)(bipy)}₂]·5H₂O (3), were synthesized and used to inhibit the aggregation of hIAPP and its fragments, namely, hIAPP19-37 and hIAPP20-29. Results revealed that shortening the peptide sequence decreased the aggregation capability of hIAPP fragments, and the oxidovanadium complexes inhibited the fibrillization of hIAPP better than its fragments. Interestingly, the binding of oxidovanadium complexes to hIAPP and its fragments presented a distinct thermodynamic behavior. Oxidovanadium complexes featured the disaggregation capability against hIAPP, better than against its fragments. These complexes also decreased the cytotoxicity caused by hIAPP and its fragments by reducing the production of oligomers. 3 may be a good hIAPP inhibitor based on its inhibition, disaggregation capability, and regulatory effect on peptide-induced cytotoxicity. Oxidovanadium complexes exhibit potential as metallodrugs against amyloidosis-related diseases.

Development of coumarin-benzofuran hybrids as versatile multitargeted compounds for the treatment of Alzheimer's Disease

Alzheimer's disease (AD), the most common cause of dementia, is a neurodegenerative disorder characterized by progressive deterioration of memory and cognition. The evidenced multifactorial nature of AD has been considered the main reason for the absence of cure so far. Therefore, the development of novel hybrids to treat the disease is very much essential. Focusing on this, a novel series of coumarin-benzofuran hybrids have been designed and screened as anti-Alzheimer's disease agents. The strategy is to obtain an effective mimetic of donepezil, which is acetylcholinesterase inhibitor. Herein, the two main scaffolds namely coumarin and benzofuran are known pharmacophore moieties and we have performed their molecular design, pharmacokinetic descriptor studies for drug-likeliness. Further, in vitro studies such as antioxidant capacity, acetylcholinesterase (AChE) inhibition and amyloid-β (Aβ) self-aggregation inhibition have also been performed. Most importantly, these studies revealed that the newly synthesized hybrids can be versatile and promising drug-like moieties as efficient anti-AD agents.

Aminopyrimidine Class Aggregation Inhibitor Effectively Blocks Aβ-Fibrinogen Interaction and Aβ-Induced Contact System Activation

Accumulating evidence suggests that fibrinogen, a key protein in the coagulation cascade, plays an important role in circulatory dysfunction in Alzheimer's disease (AD). Previous work has shown that the interaction between fibrinogen and β-amyloid (Aβ), a hallmark pathological protein in AD, induces plasmin-resistant abnormal blood clots, delays fibrinolysis, increases inflammation, and aggravates cognitive function in mouse models of AD. Since Aβ oligomers have a much stronger affinity for fibrinogen than Aβ monomers, we tested whether amyloid aggregation inhibitors could block the Aβ-fibrinogen interaction and found that some Aβ aggregation inhibitors showed moderate inhibitory efficacy against this interaction. We then modified a hit compound so that it not only showed a strong inhibitory efficacy toward the Aβ-fibrinogen interaction but also retained its potency toward the Aβ42 aggregation inhibition process. Furthermore, our best hit compound, TDI-2760, modulated Aβ42-induced contact system activation, a pathological condition observed in some AD patients, in addition to inhibiting the Aβ-fibrinogen interaction and Aβ aggregation. Thus, TDI-2760 has the potential to lessen vascular abnormalities as well as Aβ aggregation-driven pathology in AD.

Synthesis and anti-obesity effects in vivo of Crotadihydrofuran C as a novel PPARγ antagonist from Crotalaria albida

Crotadihydrofuran C (CC) from the herbs of Crotalaria albida is able to inhibit adipocyte differentiation and lipid accumulation. However, the effects of CC on obesity and metabolic disorders have not yet been elucidated. In our study, the first enantioselective synthesis of the 2-isopropenyl dihydrofuran isoflavone skeleton (CC) is described. The convenient and efficient synthetic protocols developed skilfully solve the problems of the ortho-para directing group and Suzuki coupling reaction using a boronic acid pinacol ester that was more stable and easy to obtain. Furthermore, CC treatment of high-fat diet (HFD)-fed obese mice remarkably reduced their body weight, fat mass, and lipid level as well as improved insulin resistance and non-alcoholic fatty liver disease (NAFLD). A TR-FRET assay showed that CC was specifically bound to PPARγ LBD, which was further confirmed by the molecular docking study. These results suggest that CC could be a useful and potential natural product for treating metabolic diseases, including obesity, hyperlipidemia insulin resistance and NAFLD, without toxic side-effects.

Novel multitarget-directed tacrine derivatives as potential candidates for the treatment of Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disorder, which is complex and progressive; it has not only threatened the health of elderly people, but also burdened the whole social medical and health system. The available therapy for AD is limited and the efficacy remains unsatisfactory. In view of the prevalence and expected increase in the incidence of AD, the design and development of efficacious and safe anti-AD agents has become a hotspot in the field of pharmaceutical research. Due to the multifactorial etiology of AD, the multitarget-directed ligands (MTDLs) approach is promising in search for new drugs for AD. Tacrine, which is the first acetylcholinesterase (AChE) inhibitor, has been selected as the ideal active fragment because of its simple structure, clear activity, and its superiority in the structural modification, thus it could be introduced into the overall molecular skeletons of the multi-target-directed anti-AD agents. In this review, we have summarized the recent advances (2012 to the present) in the chemical modification of tacrine, which could provide the reference for the further study of novel multi-target-directed tacrine derivatives to treat AD.

Influence of oxodiperoxovanadate complexes on prion neuropeptide fibril formation

Different oxodiperoxovanadate complexes inhibit the fibril formation of prion neuropeptides by different action modes.

Novel Tacrine-Benzofuran Hybrids as Potent Multitarget-Directed Ligands for the Treatment of Alzheimer's Disease: Design, Synthesis, Biological Evaluation, and X-ray Crystallography

Twenty-six new tacrine-benzofuran hybrids were designed, synthesized, and evaluated in vitro on key molecular targets for Alzheimer's disease. Most hybrids exhibited good inhibitory activities on cholinesterases and β-amyloid self-aggregation. Selected compounds displayed significant inhibition of human β-secretase-1 (hBACE-1). Among the 26 hybrids, 2e showed the most interesting profile as a subnanomolar selective inhibitor of human acetylcholinesterase (hAChE) (IC50 = 0.86 nM) and a good inhibitor of both β-amyloid aggregation (hAChE- and self-induced, 61.3% and 58.4%, respectively) and hBACE-1 activity (IC50 = 1.35 μM). Kinetic studies showed that 2e acted as a slow, tight-binding, mixed-type inhibitor, while X-ray crystallographic studies highlighted the ability of 2e to induce large-scale structural changes in the active-site gorge of Torpedo californica AChE (TcAChE), with significant implications for structure-based drug design. In vivo studies confirmed that 2e significantly ameliorates performances of scopolamine-treated ICR mice. Finally, 2e administration did not exhibit significant hepatotoxicity.

QIAD assay for quantitating a compound's efficacy in elimination of toxic Aβ oligomers

Strong evidence exists for a central role of amyloid β-protein (Aβ) oligomers in the pathogenesis of Alzheimer’s disease. We have developed a fast, reliable and robust in vitro assay, termed QIAD, to quantify the effect of any compound on the Aβ aggregate size distribution. Applying QIAD, we studied the effect of homotaurine, scyllo-inositol, EGCG, the benzofuran derivative KMS88009, ZAβ3W, the D-enantiomeric peptide D3 and its tandem version D3D3 on Aβ aggregation. The predictive power of the assay for in vivo efficacy is demonstrated by comparing the oligomer elimination efficiency of D3 and D3D3 with their treatment effects in animal models of Alzheimer´s disease.

Methionine oxidation of amyloid peptides by peroxovanadium complexes: inhibition of fibril formation through a distinct mechanism

Peroxovanadium complexes inhibit the fibril formation of neurodegenerative amyloid peptides by oxidizing methionine residues.

Benzofuran-chalcone hybrids as potential multifunctional agents against Alzheimer's disease: synthesis and in vivo studies with transgenic Caenorhabditis elegans

In the search for effective multifunctional agents for the treatment of Alzheimer's disease (AD), a series of novel hybrids incorporating benzofuran and chalcone fragments were designed and synthesized. These hybrids were screened by using a transgenic Caenorhabditis elegans model that expresses the human β-amyloid (Aβ) peptide. Among the hybrids investigated, (E)-3-(7-methyl-2-(4-methylbenzoyl)benzofuran-5-yl)-1-phenylprop-2-en-1-one (4 f), (E)-3-(2-benzoyl-7-methylbenzofuran-5-yl)-1-phenylprop-2-en-1-one (4 i), and (E)-3-(2-benzoyl-7-methylbenzofuran-5-yl)-1-(thiophen-2-yl)prop-2-en-1-one (4 m) significantly decreased Aβ aggregation and increased acetylcholine (ACh) levels along with the overall availability of ACh at the synaptic junction. These compounds were also found to decrease acetylcholinesterase (AChE) levels, reduce oxidative stress in the worms, lower lipid content, and to provide protection against chemically induced cholinergic neurodegeneration. Overall, the multifunctional effects of these hybrids qualify them as potential drug leads for further development in AD therapy.

Efficient synthesis of mibefradil analogues: an insight into in vitro stability

This article describes the synthesis and biological evaluation of a chemical library of mibefradil analogues to investigate the effect of structural modification on in vitro stability. The construction of the dihydrobenzopyran structure in mibefradil derivatives 2 was achieved through two efficient approaches based on a diastereoselective intermolecular Reformatsky reaction and an intramolecular carbonyl-ene cyclization. In particular, the second strategy through the intramolecular carbonyl-ene reaction led to the formation of a key intermediate 3 in a short and highly stereoselective way, which has allowed for practical and convenient preparation of analogues 2. Using this protocol, we could obtain 22 new mibefradil analogues 2, which were biologically tested for in vitro efficacies against T-type calcium channels and metabolic stabilities. Among the synthesized compounds, we found that analogue 2aa containing a dihydrobenzopyran ring and a secondary amine linker showed high % remaining activities of the tested CYP enzymes retaining the excellent T-type calcium channel blocking activity. These findings indicated that the structural modification of 1 was effective for improving in vitro stability, i.e., reducing CYP inhibition and metabolic degradation.

Aminostyrylbenzofuran directly reduces oligomeric amyloid-β and reverses cognitive deficits in Alzheimer transgenic mice

Alzheimer's disease is an irreversible neurodegenerative disorder that is characterized by the abnormal aggregation of amyloid-β into neurotoxic oligomers and plaques. Although many disease-modifying molecules are currently in Alzheimer clinical trials, a small molecule that inhibits amyloid-β aggregation and ameliorates the disorder has not been approved to date. Herein, we report the effects of a potent small molecule, 6-methoxy-2-(4-dimethylaminostyryl) benzofuran (KMS88009), that directly disrupts amyloid-β oligomerization, preserving cognitive behavior when used prophylactically and reversing declines in cognitive behavior when used therapeutically. KMS88009 exhibited excellent pharmacokinetic profiles with extensive brain uptake and a high level of safety. When orally administered before and after the onset of Alzheimer's disease symptoms, KMS88009 significantly reduced assembly of amyloid-β oligomers and improved cognitive behaviors in the APP/PS1 double transgenic mouse model. The unique dual mode of action indicates that KMS88009 may be a powerful therapeutic candidate for the treatment of Alzheimer's disease.

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.

Curcumin promotes A-beta fibrillation and reduces neurotoxicity in transgenic Drosophila

The pathology of Alzheimer's disease (AD) is characterized by the presence of extracellular deposits of misfolded and aggregated amyloid-β (Aβ) peptide and intraneuronal accumulation of tangles comprised of hyperphosphorylated Tau protein. For several years, the natural compound curcumin has been proposed to be a candidate for enhanced clearance of toxic Aβ amyloid. In this study we have studied the potency of feeding curcumin as a drug candidate to alleviate Aβ toxicity in transgenic Drosophila. The longevity as well as the locomotor activity of five different AD model genotypes, measured relative to a control line, showed up to 75% improved lifespan and activity for curcumin fed flies. In contrast to the majority of studies of curcumin effects on amyloid we did not observe any decrease in the amount of Aβ deposition following curcumin treatment. Conformation-dependent spectra from p-FTAA, a luminescent conjugated oligothiophene bound to Aβ deposits in different Drosophila genotypes over time, indicated accelerated pre-fibrillar to fibril conversion of Aβ_1–42 in curcumin treated flies. This finding was supported by in vitro fibrillation assays of recombinant Aβ_1–42. Our study shows that curcumin promotes amyloid fibril conversion by reducing the pre-fibrillar/oligomeric species of Aβ, resulting in a reduced neurotoxicity in Drosophila.

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

Amyloids are protein fibrils of nanometer size resulting from protein self-assembly. They have been shown to be associated with a wide variety of diseases such as Alzheimer's and Parkinson's and may contribute to various other pathological conditions, known as amyloidoses. Insulin is prone to form amyloid fibrils under slightly destabilizing conditions in vitro and may form amyloid structures when subcutaneously injected into patients with diabetes. There is a great deal of interest in developing novel small molecule inhibitors of amyloidogenic processes, as potential therapeutic compounds. In this study, the effects of five new synthetic benzofuranone derivatives were investigated on the insulin amyloid formation process. Protein fibrillation was analyzed by thioflavin-T fluorescence, Congo red binding, circular dichroism, and electron microscopy. Despite high structural similarity, one of the five tested compounds was observed to enhance amyloid fibrillation, while the others inhibited the process when used at micromolar concentrations, which could make them interesting potential lead compounds for the design of therapeutic antiamyloidogenic compounds.

Kinetic characterization of amyloid-beta 1-42 aggregation with a multimethodological approach

Extensive evidence suggests that the self-assembly of amyloid-beta peptide (Aβ) is a nucleation-dependent process that involves the formation of several oligomeric intermediates. Despite neuronal toxicity being recently related to Aβ soluble oligomers, results from aggregation studies are often controversial, mainly because of the low reproducibility of several experimental protocols. Here a multimethodological study that included atomic force microscopy (AFM), transmission electron microscopy (TEM), fluorescence microscopy (FLM), mass spectrometry techniques (matrix-assisted laser desorption/ionization time-of-flight [MALDI-TOF] and electrospray ionization quadrupole time-of-flight [ESI-QTOF]), and direct thioflavin T (ThT) fluorescence spectroscopy were enabled to set up a reliable and highly reproducible experimental protocol for the characterization of the morphology and dimension of Aβ 1-42 (Aβ42) aggregates along the self-assembly pathway. This multimethodological approach allowed elucidating the diverse assembly species formed during the Aβ aggregation process and was applied to the detailed investigation of the mechanism of Aβ42 inhibition by myricetin. In particular, a very striking result was the molecular weight determination of the initial oligomeric nuclei by MALDI-TOF, composed of up to 10 monomers, and their morphology by AFM.

Novel imidazoline compounds as partial or full agonists of D2-like dopamine receptors inspired by I2-imidazoline binding sites ligand 2-BFI

Based on the well known biological versatility of the imidazoline nucleus, we prepared the novel derivatives 3a-k inspired by 2-BFI scaffold to assess imidazoline molecules as D(2)-like dopamine receptor ligands. Conservative chemical modifications of the lead structure, such as the introduction of an hydroxy group in the aromatic ring alone or associated with N-benzyl substitution, provided partial (3f) or nearly full (3e and 3h) agonists, all endowed with D(2)-like potency comparable to that of dopamine.

Development of chemical probes: toward the mode of action of a methylene-linked di(aryl acetate) E1

Analogues of the novel inhibitor of the PI3-K/PKB pathway, 2-[5-(2-chloroethyl)-2-acetoxy-benzyl]-4-(2-chloroethyl)-phenyl acetate (E1), have been prepared and preliminary SAR performed. This established that at least one of the chloroethyl para-substituents could be removed or modified and the ability to inhibit PKB/Akt activation retained. Synthetic methodologies were then developed to methylene-linked aryl acetates for use as molecular probes to identify the target of compound E1.

Clickable fluorescent dyes for multimodal bioorthogonal imaging

Bioorthogonal ligation with functionalized fluorescent dyes enables visualization of nuclei acids, proteins and metabolites in biological systems. Bright and modular azide- and alkyne-functionalized dyes are therefore needed to expand the fluorescence imaging capabilities of bioorthogonal ligation methods. We describe the concise synthesis of clickable fluorescent dyes based on 2-dicyanomethylene-3-cyano-2,5-dihydrofuran fluorophores and demonstrate their utility for multicolor imaging of azide- and alkyne-modified proteins as well as FRET studies.

The thioflavin T fluorescence assay for amyloid fibril detection can be biased by the presence of exogenous compounds

Thioflavin T (ThT) dye fluorescence is used regularly to quantify the formation and inhibition of amyloid fibrils in the presence of anti-amyloidogenic compounds such as polyphenols. However, in this study, it was shown, using three polyphenolics (curcumin, quercetin and resveratrol), that ThT fluorescence should be used with caution in the presence of such exogenous compounds. The strong absorptive and fluorescent properties of quercetin and curcumin were found to significantly bias the ThT fluorescence readings in both in situ real-time ThT assays and single time-point dilution ThT-type assays. The presence of curcumin at concentrations as low as 0.01 and 1 mum was sufficient to interfere with the ThT fluorescence associated with fibrillar amyloid-beta(1-42) (0.5 mum) and fibrillar reduced and carboxymethylated kappa-casein (50 mum), respectively. The ThT fluorescence associated with fibrillar amyloid-beta(1-42) was also biased using higher concentrations of resveratrol, a polyphenol that is not spectroscopically active at the wavelengths of ThT fluorescence, implying that there can be direct interactions between ThT and the exogenous compound and/or competitive binding with ThT for the fibrils. Thus, in all cases where ThT is used in the presence of an exogenous compound, biases for amyloid-associated ThT fluorescence should be tested, regardless of whether the additive is spectroscopically active. Simple methods to conduct these tests were described. The Congo red spectral shift assay is demonstrated as a more viable spectrophotometric alternative to ThT, but allied methods, such as transmission electron microscopy, should also be used to assess fibril formation independently of dye-based assays. Structured digital abstract: * MINT-7259867: RCMkappa-CN (uniprotkb:P02668) and RCMkappa-CN (uniprotkb:P02668) bind (MI:0407) by electron microscopy (MI:0040) * MINT-7258930: RCMkappa-CN (uniprotkb:P02668) and RCMkappa-CN (uniprotkb:P02668) bind (MI:0407) by fluorescence technologies (MI:0051) * MINT-7259878: Amyloid beta (uniprotkb:P05067) and Amyloid beta (uniprotkb:P05067) bind (MI:0407) by fluorescence technologies (MI:0051).