Synthesis of Azuleno[2,1-b]quinolones and Quinolines via Brønsted Acid-Catalyzed Cyclization of 2-Arylaminoazulenes.

Quinolone and quinoline derivatives are frequently found as substructures in pharmaceutically active compounds. In this paper, we describe a procedure for the synthesis of azuleno[2,1-b]quinolones and quinolines from 2-arylaminoazulene derivatives, which are readily prepared via the aromatic nucleophilic substitution reaction of a 2-chloroazulene derivative with several arylamines. The synthesis of azuleno[2,1-b]quinolones was established by the Brønsted acid-catalyzed intramolecular cyclization of 2-arylaminoazulene derivatives bearing two ester groups at the five-membered ring. The halogenative aromatization of azuleno[2,1-b]quinolones with POCl3 yielded azuleno[2,1-b]quinolines with a chlorine substituent at the pyridine moiety. The aromatic nucleophilic substitution reaction of azuleno[2,1-b]quinolines bearing chlorine substituent with secondary amines was also investigated to afford the aminoquinoline derivatives. These synthetic methodologies reported in this paper should be valuable in the development of new pharmaceuticals based on the azulene skeleton.

Synthesis, Reactivity, and Properties of Benz[a]azulenes via the [8 + 2] Cycloaddition of 2H-Cyclohepta[b]furan-2-ones with an Enamine.

Starting with the reaction of 2H-cyclohepta[b]furan-2-ones with an enamine, which was prepared from 4-tert-butylcyclohexanone and pyrrolidine, benz[a]azulenes having both formyl and tert-butyl groups were obtained in the three-step sequence. Subsequently, both the formyl and tert-butyl groups were eliminated by heating the benz[a]azulene derivatives in 100% H3PO4 to give benz[a]azulenes without these substituents in high yields. In terms of product yield, this method is the best one ever reported for the synthesis of the parent benz[a]azulene so far. The conversion of the benz[a]azulene derivatives with a formyl group into cyclohept[a]acenaphthylen-3-one derivatives was also investigated via Knoevenagel condensation with dimethyl malonate, followed by Brønsted acid-mediated intramolecular cyclization. The structural features including the bond alternation in the benz[a]azulene derivatives were revealed by NMR studies, NICS calculations, and a single-crystal X-ray structural analysis. The optical and electrochemical properties of a series of benz[a]azulene derivatives were evaluated by UV/Vis, fluorescence spectroscopy, and voltammetry experiments. As a result, we found that some benz[a]azulene derivatives showed remarkable luminescence in acidic media. In addition, the benz[a]azulene derivatives with the electron-withdrawing group and cyclohept[a]acenaphthylen-3-one derivative displayed good reversibility in the spectral changes under the electrochemical redox conditions.

ApoE (Apolipoprotein E) in Brain Pericytes Regulates Endothelial Function in an Isoform-Dependent Manner by Modulating Basement Membrane Components.

OBJECTIVE: The ε4 allele of the APOE gene (APOE4) is the strongest genetic risk factor for Alzheimer disease when compared with the common ε3 allele. Although there has been significant progress in understanding how apoE4 (apolipoprotein E4) drives amyloid pathology, its effects on amyloid-independent pathways, in particular cerebrovascular integrity and function, are less clear. Approach and Results: Here, we show that brain pericytes, the mural cells of the capillary walls, differentially modulate endothelial cell phenotype in an apoE isoform-dependent manner. Extracellular matrix protein induction, tube-like structure formation, and barrier formation were lower with endothelial cells cocultured with pericytes isolated from apoE4-targeted replacement (TR) mice compared with those from apoE3-TR mice. Importantly, aged apoE4-targeted replacement mice had decreased extracellular matrix protein expression and increased plasma protein leakages compared with apoE3-TR mice. CONCLUSIONS: ApoE4 impairs pericyte-mediated basement membrane formation, potentially contributing to the cerebrovascular effects of apoE4.

Molecular Transformation to Pyrroles, Pentafulvenes, and Pyrrolopyridines by [2+2] Cycloaddition of Propargylamines with Tetracyanoethylene.

In this paper, we describe an efficient and atom-economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition-retroelectrocyclization of N-substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines.

Synthesis of phthalimides cross-conjugated with an azulene ring, and their structural, optical and electrochemical properties.

The preparation of phthalimides cross-conjugated with an azulene ring was established by a one-pot Diels-Alder reaction of the corresponding 2-aminofuran derivatives with several maleimides, without the isolation of the intermediately formed [4 + 2] cycloadducts. The structure, optical and electrochemical properties of the novel phthalimide derivatives were clarified by single-crystal X-ray analysis, UV/Vis and fluorescence spectra, spectroelectrochemistry and voltammetry experiments, and theoretical calculations. These results indicated that the substituents on the azulene ring greatly affect the optical and electrochemical properties of the molecules.

Selective loss of cortical endothelial tight junction proteins during Alzheimer's disease progression.

While the accumulation and aggregation of amyloid-ß and tau are central events in the pathogenesis of Alzheimer's disease, there is increasing evidence that cerebrovascular pathology is also abundant in Alzheimer's disease brains. In brain capillaries, endothelial cells are connected closely with one another through transmembrane tight junction proteins forming the blood-brain barrier. Because the blood-brain barrier tightly regulates the exchange of molecules between brain and blood and maintains brain homeostasis, its impairment is increasingly recognized as a critical factor contributing to Alzheimer's disease pathogenesis. However, the pathological relationship between blood-brain barrier properties and Alzheimer's disease progression in the human brain is not fully understood. In this study, we show that the loss of cortical tight junction proteins is a common event in Alzheimer's disease, and is correlated with synaptic degeneration. By quantifying the amounts of major tight junction proteins, claudin-5 and occludin, in 12 brain regions dissected from post-mortem brains of normal ageing (n = 10), pathological ageing (n = 14) and Alzheimer's disease patients (n = 19), we found that they were selectively decreased in cortical areas in Alzheimer's disease. Cortical tight junction proteins were decreased in association with the Braak neurofibrillary tangle stage. There was also a negative correlation between the amount of tight junction proteins and the amounts of insoluble Alzheimer's disease-related proteins, in particular amyloid-ß40, in cortical areas. In addition, the amount of tight junction proteins in these areas correlated positively with those of synaptic markers. Thus, loss of cortical tight junction proteins in Alzheimer's disease is associated with insoluble amyloid-ß40 and loss of synaptic markers. Importantly, the positive correlation between claudin-5 and synaptic markers, in particular synaptophysin, was present independent of insoluble amyloid-ß40, amyloid-ß42 and tau values, suggesting that loss of cortical tight junction proteins and synaptic degeneration is present, at least in part, independent of insoluble Alzheimer's disease-related proteins. Collectively, these results indicate that loss of tight junction proteins occurs predominantly in the neocortex during Alzheimer's disease progression. Further, our findings provide a neuropathological clue as to how endothelial tight junction pathology may contribute to Alzheimer's disease pathogenesis in both synergistic and additive manners to typical amyloid-ß and tau pathologies.

Tau and apolipoprotein E modulate cerebrovascular tight junction integrity independent of cerebral amyloid angiopathy in Alzheimer's disease.

INTRODUCTION: Cerebrovascular pathologies including cerebral amyloid angiopathy (CAA) and blood-brain barrier (BBB) dysregulation are prominent features in the majority of Alzheimer's disease (AD) cases. METHODS: We performed neuropathologic and biochemical studies on a large, neuropathologically confirmed human AD cohort (N = 469). Amounts of endothelial tight junction proteins claudin-5 (CLDN5) and occludin (OCLN), and major AD-related molecules (amyloid beta [Aß40], Aß42, tau, p-tau, and apolipoprotein E) in the temporal cortex were assessed by ELISA. RESULTS: Higher levels of soluble tau, insoluble p-tau, and apolipoprotein E (apoE) were independently correlated with lower levels of endothelial tight junction proteins CLDN5 and OCLN in AD brains. Although high Aß40 levels, APOE ε4, and male sex were predominantly associated with exacerbated CAA severity, those factors did not influence tight junction protein levels. DISCUSSION: Refining the molecular mechanisms connecting tau, Aß, and apoE with cerebrovascular pathologies is critical for greater understanding of AD pathogenesis and establishing effective therapeutic interventions for the disease.

Construction of a 2,2'-biazulene framework via Brønsted acid-promoted annulation of 2,3-di(1-azulenyl)benzofurans.

Dibenzofurans featuring a 2,2'-biazulene framework were prepared in good yields by Brønsted acid-promoted annulation of 2,3-di(1-azulenyl)benzofurans in 100% H3PO4. NMR, UV-Vis, and fluorescence spectroscopies were used to investigate the structural and optical properties of the products prepared. Remarkably, the annulated products exhibited fluorescence, with the longest wavelength of azulene derivatives reported to date, which extended into the near-infrared region under acidic conditions.

Peripheral apoE4 enhances Alzheimer's pathology and impairs cognition by compromising cerebrovascular function.

The ε4 allele of the apolipoprotein E (APOE) gene, a genetic risk factor for Alzheimer's disease, is abundantly expressed in both the brain and periphery. Here, we present evidence that peripheral apoE isoforms, separated from those in the brain by the blood-brain barrier, differentially impact Alzheimer's disease pathogenesis and cognition. To evaluate the function of peripheral apoE, we developed conditional mouse models expressing human APOE3 or APOE4 in the liver with no detectable apoE in the brain. Liver-expressed apoE4 compromised synaptic plasticity and cognition by impairing cerebrovascular functions. Plasma proteome profiling revealed apoE isoform-dependent functional pathways highlighting cell adhesion, lipoprotein metabolism and complement activation. ApoE3 plasma from young mice improved cognition and reduced vessel-associated gliosis when transfused into aged mice, whereas apoE4 compromised the beneficial effects of young plasma. A human induced pluripotent stem cell-derived endothelial cell model recapitulated the plasma apoE isoform-specific effect on endothelial integrity, further supporting a vascular-related mechanism. Upon breeding with amyloid model mice, liver-expressed apoE4 exacerbated brain amyloid pathology, whereas apoE3 reduced it. Our findings demonstrate pathogenic effects of peripheral apoE4, providing a strong rationale for targeting peripheral apoE to treat Alzheimer's disease.

Preparation of single cell suspensions enriched in mouse brain vascular cells for single-cell RNA sequencing.

Cerebral blood vessels supply oxygen and nutrients, remove metabolic waste, and play a critical role in maintaining brain homeostasis. Cerebrovasculature is composed of heterogeneous populations of brain vascular cells (BVCs). A major challenge in effective cerebrovascular transcriptional profiling is high-quality BVC procurement, permitting high sequencing depth. Here, we establish cell isolation procedures for glio-vascular cell-enriched single-cell RNA sequencing enabling unbiased characterization of BVC transcriptional heterogeneity. Our approach can be used to address vascular-specific contribution to brain diseases. For complete details on the use and execution of this protocol, please refer to Yamazaki et al. (2021).

Azulene-Substituted Donor-Acceptor Polymethines and 1,6'-Bi-, 1,6';3,6''-Ter-, and Quinqueazulenes via Zincke Salts: Synthesis, and Structural, Optical, and Electrochemical Properties.

Azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes composed of the 1,6'-biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40-92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation-cyclization with cyclopentadienide ions, so-called Ziegler-Hafner method, produced the corresponding 1,6'-biazulenes, 1,6';3,6''-terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene-substituted donor-acceptor polymethines, bi-, ter-, and quinqueazulenes were revealed by single-crystal X-ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties.

Vascular ApoE4 Impairs Behavior by Modulating Gliovascular Function.

The ε4 allele of the apolipoprotein E gene (APOE4) is a strong genetic risk factor for Alzheimer's disease (AD) and multiple vascular conditions. ApoE is abundantly expressed in multiple brain cell types, including astrocytes, microglia, and vascular mural cells (VMCs). Here, we show that VMC-specific expression of apoE4 in mice impairs behavior and cerebrovascular function. Expression of either apoE3 or apoE4 in VMCs was sufficient to rescue the hypercholesterolemia and atherosclerosis phenotypes seen in Apoe knockout mice. Intriguingly, vascular expression of apoE4, but not apoE3, reduced arteriole blood flow, impaired spatial learning, and increased anxiety-like phenotypes. Single-cell RNA sequencing of vascular and glial cells revealed that apoE4 in VMCs was associated with astrocyte activation, while apoE3 was linked to angiogenic signature in pericytes. Together, our data support cell-autonomous effects of vascular apoE on brain homeostasis in an isoform-dependent manner, suggesting a critical contribution of vascular apoE to AD pathogenesis.

Synthesis of thiophene-fused heptalenes by cycloaddition of azulenothiophenes with dimethyl acetylenedicarboxylate.

Heptalene has a fused structure of two cycloheptatrienes which is one of the non-aromatic bicyclic molecules with a 12π-electronic structure. We report herein the synthesis of thiophene-fused heptalene derivatives from the corresponding azulenothiophenes via cycloaddition reaction with dimethyl acetylenedicarboxylate. Their structure was clarified by single-crystal X-ray structural analysis. The electronic properties of the thiophene-fused heptalenes obtained by this study were characterized by UV/Vis and fluorescence spectroscopy measurements. The electrochemical features of these derivatives were also examined by voltammetry and spectroelectrochemical experiments.

Direct synthesis of 2-arylazulenes by [8+2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with silyl enol ethers.

We developed a procedure for the direct synthesis of 2-arylazulenes, which were obtained in moderate to excellent yields, by [8+2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with aryl-substituted silyl enol ethers. The structures of some 2-arylazulenes were clarified by single-crystal X-ray analysis. The 2-phenylazulene derivatives obtained by this study showed noticeable fluorescence in acidic media.

Alzheimer's Risk Factors Age, APOE Genotype, and Sex Drive Distinct Molecular Pathways.

Evidence suggests interplay among the three major risk factors for Alzheimer's disease (AD): age, APOE genotype, and sex. Here, we present comprehensive datasets and analyses of brain transcriptomes and blood metabolomes from human apoE2-, apoE3-, and apoE4-targeted replacement mice across young, middle, and old ages with both sexes. We found that age had the greatest impact on brain transcriptomes highlighted by an immune module led by Trem2 and Tyrobp, whereas APOE4 was associated with upregulation of multiple Serpina3 genes. Importantly, these networks and gene expression changes were mostly conserved in human brains. Finally, we observed a significant interaction between age, APOE genotype, and sex on unfolded protein response pathway. In the periphery, APOE2 drove distinct blood metabolome profile highlighted by the upregulation of lipid metabolites. Our work identifies unique and interactive molecular pathways underlying AD risk factors providing valuable resources for discovery and validation research in model systems and humans.