Concurrent suppression of Aβ aggregation and NLRP3 inflammasome activation for treating Alzheimer's disease

Alzheimer''s disease (AD) is a neurodegenerative illness accompanied by severe memory loss, cognitive disorders and impaired behavioral ability. Amyloid β-peptide (Aβ) aggregation and nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome play crucial roles in the pathogenesis of AD. Aβ plaques not only induce oxidative stress and impair neurons, but also activate the NLRP3 inflammasome, which releases inflammatory cytokine IL-1β to trigger neuroinflammation. A bifunctional molecule, 2-[2-(benzo[d]thiazol-2-yl)phenylamino]benzoic acid (BPBA), with both Aβ-targeting and inflammasome-inhibiting capabilities was designed and synthesized. BPBA inhibited self- and Cu²⁺- or Zn²⁺-induced Aβ aggregation, disaggregated the already formed Aβ aggregates, and reduced the neurotoxicity of Aβ aggregates; it also inhibited the activation of the NLRP3 inflammasome and reduced the release of IL-1β in vitro and vivo. Moreover, BPBA decreased the production of reactive oxygen species (ROS) and alleviated Aβ-induced paralysis in transgenic C. elegans with the human Aβ₄₂ gene. BPBA exerts an anti-AD effect mainly through dissolving Aβ aggregates and inhibiting NLRP3 inflammasome activation synergistically.

Bifunctional molecule BPBA inhibits Aβ aggregation and NLRP3 inflammasome activation, thereby decreasing ROS and IL-1β in vitro and vivo; it synergistically prevents Alzheimer''s disease via alleviating Aβ neurotoxicity and reducing neuroinflammation.     

Differentiating Aβ40 and Aβ42 in amyloid plaques with a small molecule fluorescence probe

Differentiating amyloid beta (Aβ) subspecies Aβ40 and Aβ42 has long been considered an impossible mission with small-molecule probes. In this report, based on recently published structures of Aβ fibrils, we designed iminocoumarin–thiazole (ICT) fluorescence probes to differentiate Aβ40 and Aβ42, among which Aβ42 has much higher neurotoxicity. We demonstrated that ICTAD-1 robustly responds to Aβ fibrils, evidenced by turn-on fluorescence intensity and red-shifting of emission peaks. Remarkably, ICTAD-1 showed different spectra towards Aβ40 and Aβ42 fibrils. In vitro results demonstrated that ICTAD-1 could be used to differentiate Aβ40/42 in solutions. Moreover, our data revealed that ICTAD-1 could be used to separate Aβ40/42 components in plaques of AD mouse brain slides. In addition, two-photon imaging suggested that ICTAD-1 was able to cross the BBB and label plaques in vivo. Interestingly, we observed that ICTAD-1 was specific toward plaques, but not cerebral amyloid angiopathy (CAA) on brain blood vessels. Given Aβ40 and Aβ42 species have significant differences of neurotoxicity, we believe that ICTAD-1 can be used as an important tool for basic studies and has the potential to provide a better diagnosis in the future.

A small molecule fluorescence probe ICTAD-1 was rationally designed for differentiating Aβ40 and Aβ42 in solutions and in Aβ plaques.     

Anionic Oligothiophenes Compete for Binding of X‐34 but not PIB to Recombinant Aβ Amyloid Fibrils and Alzheimer's Disease Brain‐Derived Aβ

Deposits comprised of amyloid‐β (Aβ) are one of the pathological hallmarks of Alzheimer's disease (AD) and small hydrophobic ligands targeting these aggregated species are used clinically for the diagnosis of AD. Herein, we observed that anionic oligothiophenes efficiently displaced X‐34, a Congo Red analogue, but not Pittsburgh compound B (PIB) from recombinant Aβ amyloid fibrils and Alzheimer's disease brain‐derived Aβ. Overall, we foresee that the oligothiophene scaffold offers the possibility to develop novel high‐affinity ligands for Aβ pathology only found in human AD brain, targeting a different site than PIB.     

Target-driven supramolecular self-assembly for selective amyloid-β photooxygenation against Alzheimer's disease

Photo-oxygenation of β-amyloid (Aβ) has been considered an efficient way to inhibit Aβ aggregation in Alzheimer''s disease (AD). However, current photosensitizers cannot simultaneously achieve enhanced blood–brain barrier (BBB) permeability and selective photooxygenation of Aβ, leading to poor therapeutic efficacy, severe off-target toxicity, and substandard bioavailability. Herein, an Aβ target-driven supramolecular self-assembly (PKNPs) with enhanced BBB penetrability and switchable photoactivity is designed and demonstrated to be effective in preventing Aβ aggregation in vivo. PKNPs are prepared by the self-assembly of the Aβ-targeting peptide KLVFF and an FDA-approved porphyrin derivative (5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin). Due to the photothermal effect of PKNPs, the BBB permeability of PKNPs under irradiation is 8.5-fold higher than that of porphyrin alone. Moreover, upon selective interaction with Aβ, PKNPs undergo morphological change from the spherical to the amorphous form, resulting in a smart transformation from photothermal activity to photodynamic activity. Consequently, the disassembled PKNPs can selectively oxygenate Aβ without affecting off-target proteins (insulin, bovine serum albumin, and human serum albumin). The well-designed PKNPs exhibit not only improved BBB permeability but also highly selective Aβ photooxygenation. Furthermore, in vivo experiments demonstrate that PKNPs can alleviate Aβ-induced neurotoxicity and prolong the life span of the commonly used AD transgenic Caenorhabditis elegans CL2006. Our work may open a new path for using supramolecular self-assemblies as switchable phototheranostics for the selective and effective prevention of Aβ aggregation and related neurotoxicity in AD.

Photo-oxygenation of β-amyloid (Aβ) has been considered an efficient way to inhibit Aβ aggregation in Alzheimer''s disease (AD). We present the first example of Aβ-responsive photodynamic therapy to treatment of AD by using PKNPs self-assemblies.     

One class classification as a practical approach for accelerating π–π co-crystal discovery

The implementation of machine learning models has brought major changes in the decision-making process for materials design. One matter of concern for the data-driven approaches is the lack of negative data from unsuccessful synthetic attempts, which might generate inherently imbalanced datasets. We propose the application of the one-class classification methodology as an effective tool for tackling these limitations on the materials design problems. This is a concept of learning based only on a well-defined class without counter examples. An extensive study on the different one-class classification algorithms is performed until the most appropriate workflow is identified for guiding the discovery of emerging materials belonging to a relatively small class, that being the weakly bound polyaromatic hydrocarbon co-crystals. The two-step approach presented in this study first trains the model using all the known molecular combinations that form this class of co-crystals extracted from the Cambridge Structural Database (1722 molecular combinations), followed by scoring possible yet unknown pairs from the ZINC15 database (21 736 possible molecular combinations). Focusing on the highest-ranking pairs predicted to have higher probability of forming co-crystals, materials discovery can be accelerated by reducing the vast molecular space and directing the synthetic efforts of chemists. Further on, using interpretability techniques a more detailed understanding of the molecular properties causing co-crystallization is sought after. The applicability of the current methodology is demonstrated with the discovery of two novel co-crystals, namely pyrene-6H-benzo[c]chromen-6-one (1) and pyrene-9,10-dicyanoanthracene (2).

Machine learning using one class classification on a database of existing co-crystals enables the identification of co-formers which are likely to form stable co-crystals, resulting in the synthesis of two co-crystals of polyaromatic hydrocarbons.     

Pseudosterins A–C,Three 1-Ethyl-3-formyl-β-carbolines from Pseudostellaria heterophylla and Their Cardioprotective Effects

Pseudostellaria heterophylla is used in China not only as a functional food but also as an herb to tonify the spleen, enhance immunity, and treat palpitation. Our previous investigation showed that a fraction enriched in glycosides obtained from the roots of P. heterophylla possessed pronounced protective effects on H9c2 cells against CoCl₂-induced hypoxic injury. However, the active compounds responsible for the observed effects were still unknown. In the current investigation, pseudosterins A–C (1–3), three new alkaloids with a 1-ethyl-3-formyl-β-carboline skeleton, together with polydatin, have been isolated from the active fraction. Their structures were elucidated on the basis of spectroscopic analysis and quantum chemical calculations. The four compounds showed cardioprotective effects against sodium hydrosulfite-induced hypoxia-reoxygenation injury in H9c2 cells, with the three alkaloids being more potent. This is also the first report of alkaloids with a β-carboline skeleton isolated from P. heterophylla as cardioprotective agents.     

Modulation of αVβ6 integrin in osteoarthritis-related synovitis and the interaction with VTN(381–397 a.a.) competing for TGF-β1 activation

Osteoarthritis is characterized by structural alteration of joints. Fibrosis of the synovial tissue is often detected and considered one of the main causes of joint stiffness and pain. In our earlier proteomic study, increased levels of vitronectin (VTN) fragment (amino acids 381–397) were observed in the serum of osteoarthritis patients. In this work, the affinity of this fragment for integrins and its putative role in TGF-β1 activation were investigated. A competition study determined the interaction of VTN_{(381–397 a.a.)} with α_Vβ₆ integrin. Subsequently, the presence of α_Vβ₆ integrin was substantiated on primary human fibroblast-like synoviocytes (FLSs) by western blot and flow cytometry. By immunohistochemistry, β₆ was detected in synovial membranes, and its expression showed a correlation with tissue fibrosis. Moreover, β₆ expression was increased under TGF-β1 stimulation; hence, a TGF-β bioassay was applied. We observed that α_Vβ₆ could mediate TGF-β1 bioavailability and that VTN_{(381–397 a.a.)} could prevent TGF-β1 activation by interacting with α_Vβ₆ in human FLSs and increased α-SMA. Finally, we analyzed serum samples from healthy controls and patients with osteoarthritis and other rheumatic diseases by nano-LC/Chip MS–MS, confirming the increased expression of VTN_{(381–397 a.a.)} in osteoarthritis as well as in lupus erythematosus and systemic sclerosis. These findings corroborate our previous observations concerning the overexpression of VTN_{(381–397 a.a.)} in osteoarthritis but also in other rheumatic diseases. This fragment interacts with α_Vβ₆ integrin, a receptor whose expression is increased in FLSs from the osteoarthritic synovial membrane and that can mediate the activation of the TGF-β1 precursor in human FLSs.Subject terms: Osteoarthritis, Cell culture     

Detection of Aβ Monomers and Oligomers: Early Diagnosis of Alzheimer's Disease

Alzheimer's disease (AD), as the most common progressive neurodegenerative disorder, is pathologically characterized by deposition of extracellular plaque composed of amyloid‐β peptide (Aβ). Different assembled states of Aβ have been considered as both important biomarkers and drug targets for the diagnosis and therapy of AD. Recent studies demonstrate that small, diffusible Aβ oligomers formed by aggregation of Aβ monomers are the major toxic agents in AD. Therefore, the development of reliable assays for Aβ (both monomers and oligomers) will be important for the early differential diagnosis of dementia, predicting the progression of AD, as well as monitoring the effectiveness of novel anti‐Aβ drugs for AD. In this review, we summarize the recent progress made in the development of techniques for detection of Aβ monomers and oligomers. In particular, the principles governing the design of these sensors are classified and summarized. Moreover, the advantages and disadvantages of the assays are evaluated. This review also discusses the improvements and challenges for application of these assays in the early diagnosis of AD.     

Eriodictyol and Homoeriodictyol Improve Memory Impairment in Aβ25–35-Induced Mice by Inhibiting the NLRP3 Inflammasome

(1) Alzheimer’s disease (AD) is a neurodegenerative disorder, and it is now widely accepted that neuroinflammation plays a key role in its pathogenesis. Eriodictyol (Eri) and homoeriodictyol (Hom), dihydroflavonoids extracted from a variety of plants, have been confirmed to display a relationship with neuroprotection. (2) Methods: An AD mouse model was constructed by intracerebroventricular (ICV) injection of the Aβ_25–35 peptide, and Eri and Hom were administered orally for 4 weeks. UPLC-MS/MS was used to determine whether Eri and Hom cross the blood–brain barrier to exert their therapeutic effects. Histological changes in the brain and levels of Aβ were evaluated, and Y-maze and new object recognition experiments were conducted to assess the effects of Eri and Hom on Aβ_25–35-induced memory impairment in mice. The levels of oxidative stress and apoptosis in peripheral immune cells and progenitor cells in the hippocampal region were analyzed by flow cytometry and in vitro assays. Western blotting and enzyme-linked immunosorbent assays (ELISA) were used to measure the expression levels of NLRP3 inflammasome-related proteins and inflammatory factors in the brain. The effect of nigericin (an agonist of the NLRP3 inflammasome) on Eri and Hom intervention in LPS-induced N9 microglia was examined using a High Content Screening System. (3) Results: Eri and Hom reduced neuronal damage in mouse brain tissue, decreased Aβ levels in the brain, downregulated oxidative stress and apoptosis levels, and improved learning and memory capacity by crossing the blood–brain barrier to exert its effects. Moreover, Eri and Hom inhibited NLRP3 inflammasome activation and ameliorated immune cell disorder. Furthermore, the effect of Eri and Hom on LPS-induced N9 microglia disappeared after the addition of nigericin to agonize NLRP3 receptors. (4) Conclusions: Eri and Hom improved Aβ_25–35-induced memory impairment in mice by inhibiting the NLRP3 inflammasome.     

An improved capillary electrophoresis method for in vitro monitoring of the challenging early steps of Aβ1–42 peptide oligomerization: Application to anti‐Alzheimer's drug discovery

We report an improved CE method to monitor in vitro the self‐assembly of monomeric amyloid β‐peptide (42 amino acids amyloid β‐peptide, Aβ_1–42) and in particular the crucial early steps involved in the formation of the neurotoxic oligomers. In order to start the kinetics from the beginning, sample preparation was optimized to provide samples containing exclusively the monomeric form. The CE method was also improved using a dynamic coating and by reducing the separation distance. Using this method, the disappearance of the monomer as well as the progressive formation of four species during the self‐assembly process can now be monitored and quantified over time. The hydrodynamic radius of the species present at the initial kinetics step was estimated around 1.8 nm by Taylor dispersion analysis while SDS‐PAGE analyses showed the predominance of the monomer. These results confirmed that the Aβ_1–42 species present at this initial time was the monomer. Methylene blue, an anti‐Alzheimer disease candidate, was then evaluated. In spite of an oligomerization inhibition, the enhanced disappearance of the Aβ_1–42 monomer provoked by methylene blue was demonstrated for the first time. This method, allowing the monomeric and smallest oligomeric species to be monitored, represents a new accurate and precise way to evaluate compounds for drug discovery.     

Metal-chelating benzothiazole multifunctional compounds for the modulation and 64Cu PET imaging of Aβ aggregation

While Alzheimer''s Disease (AD) is the most common neurodegenerative disease, there is still a dearth of efficient therapeutic and diagnostic agents for this disorder. Reported herein are a series of new multifunctional compounds (MFCs) with appreciable affinity for amyloid aggregates that can be potentially used for both the modulation of Aβ aggregation and its toxicity, as well as positron emission tomography (PET) imaging of Aβ aggregates. Firstly, among the six compounds tested HYR-16 is shown to be capable to reroute the toxic Cu-mediated Aβ oligomerization into the formation of less toxic amyloid fibrils. In addition, HYR-16 can also alleviate the formation of reactive oxygen species (ROS) caused by Cu²⁺ ions through Fenton-like reactions. Secondly, these MFCs can be easily converted to PET imaging agents by pre-chelation with the ⁶⁴Cu radioisotope, and the Cu complexes of HYR-4 and HYR-17 exhibit good fluorescent staining and radiolabeling of amyloid plaques both in vitro and ex vivo. Importantly, the ⁶⁴Cu-labeled HYR-17 is shown to have a significant brain uptake of up to 0.99 ± 0.04 %ID per g. Overall, by evaluating the various properties of these MFCs valuable structure–activity relationships were obtained that should aid the design of improved therapeutic and diagnostic agents for AD.

A series of multifunctional compounds and their ⁶⁴Cu complexes exhibit good affinity for Aβ aggregates and can also control Aβ toxicity.     

Bispidine as a β-strand nucleator: from a β-arch to self-assembled cages and vesicles

The development of synthetic scaffolds that nucleate well-folded secondary structures is highly challenging. Herein, we designed and synthesized a series of core-modified peptides (F1, F2, F3, and F4) that fold into β-strand structures. These bispidine-scaffolded peptides were studied by CD, IR, NMR, single crystal XRD, and Molecular Dynamics (MD) simulations to investigate their conformational preferences. Solid-state and solution studies revealed that bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating the β-strand structure. Scaffolds that nucleate an isolated β-strand conformation are rare. Bispidine placed at the C-terminus of the peptide chain could nucleate a β-strand conformation, while bispidine placed at the middle resulted in a β-arch conformation. This nucleation activity stems from the ability to restrict the psi torsion angle (ψ) through intramolecular C5 hydrogen bonding between the equatorial hydrogen(s) of bispidine and the carbonyl oxygen(s) of the amino acid close to the scaffold. Furthermore, the bispidine peptidomimetic with a super secondary structure, namely β-arch, assembled into single-hole submicron cages and spherical vesicles as evident from microscopic studies. The design logic defined here will be a significant strategy for the development of β-strand mimetics and super secondary structures.

Bispidine is a versatile scaffold that could be placed either at the terminal or at the middle of the peptide strand for nucleating β-strand structures. These β-strand mimetics self-assemble to single hole submicron cages and vesicles.     

Tetrapeptidic Molecular Hydrogels: Self‐assembly and Co‐aggregation with Amyloid Fragment Aβ1‐40

A new family of isomeric tetrapeptides containing aromatic and polar amino acid residues that are able to form molecular hydrogels following a smooth change in pH is described. The hydrogels have been studied by spectroscopic and microscopic techniques showing that the peptide primary sequence has an enormous influence on the self‐assembly process. In particular, the formation of extended hydrophobic regions and the appearance of π‐stacking interactions have been revealed as the driving forces for aggregation. Moreover, the interaction of these compounds with amyloid peptidic fragment Aβ1‐40 has been studied and some of them have been shown to act as templates for the aggregation of this peptide into non‐β‐sheet fibrillar structures. These compounds could potentially be used for the capture of toxic, soluble amyloid oligomers.     

Diazaphosphinyl radical-catalyzed deoxygenation of α-carboxy ketones: a new protocol for chemo-selective C–O bond scission via mechanism regulation

C–O bond cleavage is often a key process in defunctionalization of organic compounds as well as in degradation of natural polymers. However, it seldom occurs regioselectively for different types of C–O bonds under metal-free mild conditions. Here we report a facile chemo-selective cleavage of the α-C–O bonds in α-carboxy ketones by commercially available pinacolborane under the catalysis of diazaphosphinane based on a mechanism switch strategy. This new reaction features high efficiency, low cost and good group-tolerance, and is also amenable to catalytic deprotection of desyl-protected carboxylic acids and amino acids. Mechanistic studies indicated an electron-transfer-initiated radical process, underlining two crucial steps: (1) the initiator azodiisobutyronitrile switches originally hydridic reduction to kinetically more accessible electron reduction; and (2) the catalytic phosphorus species upconverts weakly reducing pinacolborane into strongly reducing diazaphosphinane.

Diazaphosphinyl radical-catalyzed chemo-selective deoxygenation of α-carboxy ketones with pinacolborane was achieved through the mechanism switch from direct to stepwise hydride transfer of diazaphosphinane.

The importance of reductive deoxygenation can be gauged by the wide use of Barton–McCombie deoxygenation in organic syntheses.¹ Such C–O bond cleavage is also a crucial step in the degradation of natural polymers (e.g., sugars and lignins) to recycle sustainable resources.² Consequently, a great variety of methodologies were explored for activation of these strong C–O bonds.³ Among them, deoxygenation of α-acyloxy ketones^3b,c,4 (represented by benzoin derivatives, stemming from simple aldehydes via benzoin condensation⁵) has attracted considerable attention, because it may provide a facile way for accessing commonly useful building blocks (aryl ketones).⁶ As known, benzoin derivatives bear two types of C–O bonds—the carbonyl π-C O bond and the benzyl σ-C–O bond (Scheme 1). While reduction of the carbonyl π-C O bonds has been well established through transition metal-⁷ or Lewis acid-mediated⁸ hydride transfers, chemo-selective cleavage of the benzyl σ-C–O bonds is challenging and has seldom been achieved.⁹ The later process is occasionally seen, however, in some radical or electron reductions, but toxic tin hydrides^1c or aggressive metal reagents (like Raney nickel,¹⁰ zinc dust,¹¹etc.) are inevitably employed.Open in a separate windowScheme 1Possible reactive sites for benzoin reduction.The recent successful development of super electron donors (SEDs),^4,12 which are defined as ground-state organic electron-donors capable of reducing aryl halides to aryl radicals or aryl anions,¹³ and photocatalytic systems^3b,c may provide alternative protocols for reductive cleavage of the σ-C–O bonds in O-acetylated benzoin. However, these electron transfer-initiated reductions also suffer from some drawbacks, such as, excessive use of SEDs and their tedious synthetic procedures, expensive photoredox catalysts and ligands, and group-tolerance issues. In fact, there have been few reports to date on metal-free systems for efficiently catalytic deoxygenation with commercially available inexpensive reductants.^3h Given the ubiquity of C–O bonds in nature, it is still an unmet need for development of efficient and economical methods for their degradation. N-Heterocyclic phosphines (NHPs)^8c,14 have recently found plentiful applications in hydridic reductions^8b,15 owing to their outstanding hydricity.¹⁶ However, this seems to blind one to search for their other promising reaction patterns, like radical and electron transfer reactivities. Up to now, the catalytic potential of NHPs in radical or electron reductions has never been explored. Given the logical understanding that a deliberately manipulated mechanism variation usually leads to diverse reactivity and selectivity, we anticipate that an intended mechanism switch for NHP-based reactions from the conventional hydride transfer to an alternative electron transfer might provide a chance for originally inaccessible chemo-selectivity in the reduction of the substrates bearing multiple reactive sites. As known from previous studies, NHPs could transfer a hydride ion to carbonyl C O bonds to deliver the corresponding alcohol counterparts (Scheme 2a).^8b This is indeed what we have seen. When NHPs are mixed with O-acetylated benzoins, an exclusive hydridic reduction of the carbonyl π-C O bonds is observed, leaving the benzyl σ-C–O bonds intact. How could we make the propensity of NHP reduction to switch from the original hydridic path to a radical one? Inspired by our recent findings that NHPs are also capable of serving as good hydrogen-atom donors (by P–H bond homolysis) and their corresponding phosphinyl radicals are excellent electron donors¹⁷ (Scheme 2b, bottom), we envisioned that if phosphinyl radicals can be in situ generated, their super electron-donicity may promote the initial electron transfer to benzoin, and trigger the subsequent benzyl σ-C–O bond scission. If this is realizable, chemo-selective deoxygenation of benzoin derivatives with NHPs may be achieved via such a mechanism switch.Open in a separate windowScheme 2Chemical transformations of N-heterocyclic phosphines NHPs in reduction reactions.It is noted that the phosphorus species NHP-OR′ is produced in either the hydride or electron reduction of benzoin derivatives (Scheme 2c). Based on the previous knowledge that NHP-OR′ can be recycled back to NHP through a σ-bond metathesis between its exocyclic P–O bond and the B–H bond of pinacolborane (HBpin),^8b we envisioned that the present deoxygenation may operate in a catalytic fashion with readily available HBpin as the terminal reductant to avoid the use of stoichiometric NHP. To verify this plot, we chose dimethyl 4,4′-(1-acetoxy-2-oxoethane-1,2-diyl)dibenzoate X as the testing substrate, and 1,3-di-tert-butyl-1,3,2-diazaphosphinane 1a as the catalyst based on its compatible reducing capacity (Scheme 3, for structure of 1a, cf.Table 1).^17a It is observed that, under the previously established catalytic conditions for carbonyl reduction (20 mol% of 1a and 1.2 equiv. HBpin),^8b the product X1 of hydridic reduction was obtained in 86% yield and 1 : 0.69 of diastereomer ratio in 12 h. On the other hand, when 10% azodiisobutyronitrile (AIBN) was added as a radical initiator, the σ-C–O bonds were, indeed, selectively cleaved to give the anticipated product X2 in 87% yield. This distinct chemo-selectivity did echo our proposed mechanism switch from the direct hydridic pathway to an electron reduction. In the following, we report this catalytic transformation in a more inclusive fashion. To our best knowledge, this is the first example of catalytic electron reduction mediated by NHPs.Optimization of reaction conditions for C–O bond cleavage

Modulation of amyloid-β aggregation by metal complexes with a dual binding mode and their delivery across the blood–brain barrier using focused ultrasound

One of the key hallmarks of Alzheimer''s disease is the aggregation of the amyloid-β peptide to form fibrils. Consequently, there has been great interest in studying molecules that can disrupt amyloid-β aggregation. While a handful of molecules have been shown to inhibit amyloid-β aggregation in vitro, there remains a lack of in vivo data reported due to their inability to cross the blood–brain barrier. Here, we investigate a series of new metal complexes for their ability to inhibit amyloid-β aggregation in vitro. We demonstrate that octahedral cobalt complexes with polyaromatic ligands have high inhibitory activity thanks to their dual binding mode involving π–π stacking and metal coordination to amyloid-β (confirmed via a range of spectroscopic and biophysical techniques). In addition to their high activity, these complexes are not cytotoxic to human neuroblastoma cells. Finally, we report for the first time that these metal complexes can be safely delivered across the blood–brain barrier to specific locations in the brains of mice using focused ultrasound.

We report a series of non-toxic cobalt(iii) complexes which inhibit Aβ peptide aggregation in vitro; these complexes can be safely delivered across the blood–brain barrier in mice using focused ultrasound.     

[124I]IBETA: A New Aβ Plaque Positron Emission Tomography Imaging Agent for Alzheimer’s Disease

Several fluorine-18-labeled PET β-amyloid (Aβ) plaque radiotracers for Alzheimer’s disease (AD) are in clinical use. However, no radioiodinated imaging agent for Aβ plaques has been successfully moved forward for either single-photon emission computed tomography (SPECT) or positron emission tomography (PET) imaging. Radioiodinated pyridyl benzofuran derivatives for the SPECT imaging of Aβ plaques using iodine-123 and iodine-125 are being pursued. In this study, we assess the iodine-124 radioiodinated pyridyl benzofuran derivative 5-(5-[¹²⁴I]iodobenzofuran-2-yl)-N,N-dimethylpyridin-2-amine ([¹²⁴I]IBETA) (Ki = 2.36 nM) for utilization in PET imaging for Aβ plaques. We report our findings on the radioiododestannylation reaction used to prepare [^124/125I]IBETA and evaluate its binding to Aβ plaques in a 5 × FAD mouse model and postmortem human AD brain. Both [¹²⁵I]IBETA and [¹²⁴I]IBETA are produced in >25% radiochemical yield and >85% radiochemical purity. The in vitro binding of [¹²⁵I]IBETA and [¹²⁴I]IBETA in transgenic 5 × FAD mouse model for Aβ plaques was high in the frontal cortex, anterior cingulate, thalamus, and hippocampus, which are regions of high Aβ accumulation, with very little binding in the cerebellum (ratio of brain regions to cerebellum was >5). The in vitro binding of [¹²⁵I]IBETA and [¹²⁴I]IBETA in postmortem human AD brains was higher in gray matter containing Aβ plaques compared to white matter (ratio of gray to white matter was >5). Anti-Aβ immunostaining strongly correlated with [¹²⁴/¹²⁵I]IBETA regional binding in both the 5 × FAD mouse and postmortem AD human brains. The binding of [¹²⁴/¹²⁵I]IBETA in 5 × FAD mouse and postmortem human AD brains was displaced by the known Aβ plaque imaging agent, Flotaza. Preliminary PET/CT studies of [¹²⁴I]IBETA in the 5 × FAD mouse model suggested [¹²⁴I]IBETA was relatively stable in vivo with a greater localization of [¹²⁴I]IBETA in the brain regions with a high concentration of Aβ plaques. Some deiodination was observed at later time points. Therefore, [¹²⁴I]IBETA may potentially be a useful PET radioligand for Aβ plaques in brain studies.     

Molecular mechanism of secreted amyloid-β precursor protein in binding and modulating GABABR1a

A recent phenomenal study discovered that the extension domain of secreted amyloid-β precursor protein (sAPP) can bind to the intrinsically disordered sushi 1 domain of the γ-aminobutyric acid type B receptor subunit 1a (GABA_BR1a) and modulate its synaptic transmission. The work provided an important structural foundation for the modulation of GABA_BR1a; however, the detailed molecular interaction mechanism, crucial for future drug design, remains elusive. Here, we further investigated the dynamical interactions between sAPP peptides and the natively unstructured sushi 1 domain using all-atom molecular dynamics simulations, for both the 17-residue sAPP peptide (APP 17-mer) and its minimally active 9 residue segment (APP 9-mer). We then explored mutations of the APP 9-mer with rigorous free energy perturbation (FEP) calculations. Our in silico mutagenesis studies revealed key residues (D4, W6, and W7) responsible for the binding with the sushi 1 domain. More importantly, one double mutation based on different vertebrate APP sequences from evolution exhibited a stronger binding (ΔΔG = −1.91 ± 0.66 kcal mol⁻¹), indicating a potentially enhanced GABA_BR1a modulator. These large-scale simulations may provide new insights into the binding mechanism between sAPP and the sushi 1 domain, which could open new avenues in the development of future GABA_BR1a-specific therapeutics.

A recent phenomenal study discovered that the extension domain of secreted amyloid-β precursor protein (sAPP) can bind to the intrinsically disordered sushi 1 domain of the γ-aminobutyric acid type B receptor subunit 1a (GABA_BR1a) and modulate its synaptic transmission.     

Chemical genetics: budding yeast as a platform for drug discovery and mapping of genetic pathways

The budding yeast Saccharomyces cerevisiae is a widely used model organism, and yeast genetic methods are powerful tools for discovery of novel functions of genes. Recent advancements in chemical-genetics and chemical-genomics have opened new avenues for development of clinically relevant drug treatments. Systematic mapping of genetic networks by high-throughput chemical-genetic screens have given extensive insight in connections between genetic pathways. Here, I review some of the recent developments in chemical-genetic techniques in budding yeast.     

Palladium-catalyzed synthesis of β-hydroxy compounds via a strained 6,4-palladacycle from directed C–H activation of anilines and C–O insertion of epoxides

A palladium-catalyzed C–H activation of acetylated anilines (acetanilides, 1,1-dimethyl-3-phenylurea, 1-phenylpyrrolidin-2-one, and 1-(indolin-1-yl)ethan-1-one) with epoxides using O-coordinating directing groups was accomplished. This C–H alkylation reaction proceeds via formation of a previously unknown 6,4-palladacycle intermediate and provides rapid access to regioselectively functionalized β-hydroxy products. Notably, this catalytic system is applicable for the gram scale mono-functionalization of acetanilide in good yields. The palladium-catalyzed coupling reaction of the ortho-C(sp²) atom of O-coordinating directing groups with a C(sp³) carbon of chiral epoxides offers diverse substrate scope in good to excellent yields. In addition, further transformations of the synthesized compound led to biologically important heterocycles. Density functional theory reveals that the 6,4-palladacycle leveraged in this work is significantly more strained (>10 kcal mol⁻¹) than the literature known 5,4 palladacycles.

The combined experimental and computational study on palladium-catalyzed regioselective C–H functionalization of O-coordinating directing groups with epoxides is described.