Exploring the Effect of Aliphatic Substituents on Aryl Cyano Amides on Enhancement of Fluorescence upon Binding to Amyloid-β Aggregates

Green Synthesis of Alzheimer's Disease Probes Aftobetin and Analogues Enabled by Flow Technology and Heterogeneous Photocatalysis

Aftobetin is a non-invasive diagnosis of Alzheimer's disease, that can bind with aggregated β-amyloid peptide in eye's lenses, used for early diagnosis of Alzheimer's disease in a rapid and painless mode. The reported synthesis of this probe fell short in the aspects of greenness and economy due to the involvement of toxic Chromium(IV) oxidant, noble palladium catalyst, elevated reaction temperature, the long reaction time as well as the cumbersome workup. Herein, a holistic optimization of the synthetic process was achieved via the employment of flow technology and heterogenous photocatalysis. Firstly, the integration of heterogenous carbon nitrides photocatalysis and circulation flow technology furnished the air oxidation of alcohol and nickel catalyzed C-N coupling at 20 g scale, thus avoiding the use of toxic Chromium and precious palladium species respectively. Flow-intensified esterification between acyl chloride and alcohol, just taking 30 seconds replaced the Steglich esterification of 6 hours, also avoiding the generation of difficult-to-remove dicyclohexylurea. Finally, C-N coupling, esterification and Knoevenagel condensation were telescoped together, thus simplifying the reaction workup. This fully-flow protocol led to the on-demand synthesis of eight probes.

The dopamine analogue CA140 alleviates AD pathology, neuroinflammation, and rescues synaptic/cognitive functions by modulating DRD1 signaling or directly binding to Abeta

BACKGROUND

We recently reported that the dopamine (DA) analogue CA140 modulates neuroinflammatory responses in lipopolysaccharide-injected wild-type (WT) mice and in 3-month-old 5xFAD mice, a model of Alzheimer's disease (AD). However, the effects of CA140 on Aβ/tau pathology and synaptic/cognitive function and its molecular mechanisms of action are unknown.

METHODS

To investigate the effects of CA140 on cognitive and synaptic function and AD pathology, 3-month-old WT mice or 8-month-old (aged) 5xFAD mice were injected with vehicle (10% DMSO) or CA140 (30 mg/kg, i.p.) daily for 10, 14, or 17 days. Behavioral tests, ELISA, electrophysiology, RNA sequencing, real-time PCR, Golgi staining, immunofluorescence staining, and western blotting were conducted.

RESULTS

In aged 5xFAD mice, a model of AD pathology, CA140 treatment significantly reduced Aβ/tau fibrillation, Aβ plaque number, tau hyperphosphorylation, and neuroinflammation by inhibiting NLRP3 activation. In addition, CA140 treatment downregulated the expression of cxcl10, a marker of AD-associated reactive astrocytes (RAs), and c1qa, a marker of the interaction of RAs with disease-associated microglia (DAMs) in 5xFAD mice. CA140 treatment also suppressed the mRNA levels of s100β and cxcl10, markers of AD-associated RAs, in primary astrocytes from 5xFAD mice. In primary microglial cells from 5xFAD mice, CA140 treatment increased the mRNA levels of markers of homeostatic microglia (cx3cr1 and p2ry12) and decreased the mRNA levels of a marker of proliferative region-associated microglia (gpnmb) and a marker of lipid-droplet-accumulating microglia (cln3). Importantly, CA140 treatment rescued scopolamine (SCO)-mediated deficits in long-term memory, dendritic spine number, and LTP impairment. In aged 5xFAD mice, these effects of CA140 treatment on cognitive/synaptic function and AD pathology were regulated by dopamine D1 receptor (DRD1)/Elk1 signaling. In primary hippocampal neurons and WT mice, CA140 treatment promoted long-term memory and dendritic spine formation via effects on DRD1/CaMKIIα and/or ERK signaling.

CONCLUSIONS

Our results indicate that CA140 improves neuronal/synaptic/cognitive function and ameliorates Aβ/tau pathology and neuroinflammation by modulating DRD1 signaling in primary hippocampal neurons, primary astrocytes/microglia, WT mice, and aged 5xFAD mice.

Excited State Rotational Freedom Impacts Viscosity Sensitivity in Arylcyanoamide Fluorescent Molecular Rotor Dyes

The microviscosity of intracellular environments plays an important role in monitoring cellular function. Thus, the capability of detecting changes in viscosity can be utilized for the detection of different disease states. Viscosity-sensitive fluorescent molecular rotors are potentially excellent probes for these applications; however, the predictable relationships between chemical structural features and viscosity sensitivity are poorly understood. Here, we investigate a set of arylcyanoamide-based fluorescent probes and the effect of small aliphatic substituents on their viscosity sensitivity. We found that the location of the substituents and the type of π-network of the fluorophore can significantly affect the viscosity sensitivity of these fluorophores. Computational analysis supported the notion that the excited state rotational energy barrier plays a dominant role in the relative viscosity sensitivity of these fluorophores. These findings provide valuable insight into the design of molecular rotor-based fluorophores for viscosity measurement.

Fluorescent molecular rotors as versatile in situ sensors for protein quantitation

Accurate protein quantitation is essential for many cellular mechanistic studies. Existing technology relies on extrinsic sample evaluation that requires significant volumes of sample as well as addition of assay-specific reagents and importantly, is a terminal analysis. This study exploits the unique chemical features of a fluorescent molecular rotor that fluctuates between twisted-to-untwisted states, with a subsequent intensity increase in fluorescence depending on environmental conditions (e.g., viscosity). Here we report the development of a rapid, sensitive in situ protein quantitation method using ARCAM-1, a representative fluorescent molecular rotor that can be employed in both non-terminal and terminal assays.