Immobilized Amyloid Hexamer Fragments to Map Active Sites of Amyloid-Targeting Chemicals

Chemically Driven Clearance of Amyloid Aggregates by Polyfunctionalized Furo[2,3-b:4,5-b']dipyridine-Chalcone Hybrids to Ameliorate Memory in an Alzheimer Mouse Model

The aberrant assembly of amyloid-β (Aβ) is implicated in Alzheimer's disease (AD). Recent clinical outcomes of Aβ-targeted immunotherapy reinforce the notion that clearing Aβ burden is a potential therapeutic approach for AD. Herein, to develop drug candidates for chemically driven clearance of Aβ aggregates, we synthesized 51 novel polyfunctionalized furo[2,3-b:4,5-b']dipyridine-chalcone hybrid compounds. After conducting two types of cell-free anti-Aβ functional assays, Aβ aggregation prevention and Aβ aggregate clearance, we selected YIAD-0336, (E)-8-((1H-pyrrol-2-yl)methylene)-10-(4-chlorophenyl)-2,4-dimethyl-7,8-dihydropyrido[3',2':4,5]furo[3,2-b]quinolin-9(6H)-one, for further in vivo investigations. As YIAD-0336 exhibited a low blood-brain barrier penetration profile, it was injected along with aggregated Aβ directly into the intracerebroventricular region of ICR mice and ameliorated spatial memory in Y-maze tests. Next, YIAD-0336 was orally administered to 5XFAD transgenic mice with intravenous injections of mannitol, and YIAD-0336 significantly removed Aβ plaques from the brains of 5XFAD mice. Collectively, YIAD-0336 dissociated toxic aggregates in the mouse brain and hence alleviated cognitive deterioration. Our findings indicate that chemically driven clearance of Aβ aggregates is a promising therapeutic approach for AD.

Early onset diagnosis in Alzheimer's disease patients via amyloid-β oligomers-sensing probe in cerebrospinal fluid

Amyloid-β (Aβ) oligomers are implicated in the onset of Alzheimer's disease (AD). Herein, quinoline-derived half-curcumin-dioxaborine (Q-OB) fluorescent probe was designed for detecting Aβ oligomers by finely tailoring the hydrophobicity of the biannulate donor motifs in donor-π-acceptor structure. Q-OB shows a great sensing potency in dynamically monitoring oligomerization of Aβ during amyloid fibrillogenesis in vitro. In addition, we applied this strategy to fluorometrically analyze Aβ self-assembly kinetics in the cerebrospinal fluids (CSF) of AD patients. The fluorescence intensity of Q-OB in AD patients' CSF revealed a marked change of log (I/I0) value of 0.34 ± 0.13 (cognitive normal), 0.15 ± 0.12 (mild cognitive impairment), and 0.14 ± 0.10 (AD dementia), guiding to distinguish a state of AD continuum for early diagnosis of AD. These studies demonstrate the potential of our approach can expand the currently available preclinical diagnostic platform for the early stages of AD, aiding in the disruption of pathological progression and the development of appropriate treatment strategies.

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.

4-Acyl-3,4-dihydropyrrolo[1,2-a]pyrazine Derivative Rescued the Hippocampal-Dependent Cognitive Decline of 5XFAD Transgenic Mice by Dissociating Soluble and Insoluble Aβ Aggregates

Cerebral amyloid-β (Aβ) deposition is a representative hallmark of Alzheimer's disease (AD). Development of Aβ-clearing small molecules could be an advantageous therapeutic strategy for Aβ clearance considering the advantages in terms of side effects, cost-effectiveness, stability, and oral bioavailability. Here, we report an Aβ-dissociating small molecule, YIAD-0121, a derivative of 4-acyl-3,4-dihydropyrrolo[1,2-a]pyrazine. Through a series of anti-Aβ screening assays, YIAD-0121 was identified to inhibit Aβ aggregation and dissociate preformed Aβ fibrils in vitro. Furthermore, the administration of YIAD-0121 in 5XFAD transgenic AD mice inhibited the increase of cerebral Aβ aggregation and progression of hippocampus-dependent cognitive decline, with ameliorated neuroinflammation.

Glycosylated and Succinylated Macrocyclic Lactones with Amyloid-β-Aggregation-Regulating Activity from a Marine Bacillus sp

Two new glycosylated and succinylated macrocyclic lactones, succinyl glyco-oxydifficidin (1) and succinyl macrolactin O (2), were isolated from a Bacillus strain collected from an intertidal mudflat on Anmyeon Island in Korea. The planar structures of 1 and 2 were proposed using mass spectrometric analysis and NMR spectroscopic data. The absolute configurations of 1 and 2 were determined by optical rotation, J-based configuration analysis, chemical derivatizations, including the modified Mosher's method, and quantum-mechanics-based calculation. Biological evaluation of 1 and 2 revealed that succinyl glyco-oxydifficidin (1) inhibited/dissociated amyloid β (Aβ) aggregation, whereas succinyl macrolactin O (2) inhibited Aβ aggregation, indicating their therapeutic potential for disassembling and removing Aβ aggregation.