Dual-Emission Fluorescent Probe for Simultaneous Visualization of Monoamine Oxidase A and Lysyl Oxidase in Alzheimer’s Disease Cell Models

Monoamine oxidase A (MAO-A) and lysyl oxidase (LOX) are two distinct amine oxidases that play crucial roles in many neurodegenerative diseases. Despite their similar enzymatic nature, their spatial distribution in different diseases and potential synergistic effects are poorly understood, partly due to the technical difficulties in detecting them concurrently. Herein, we designed and synthesized a series of dicyanoisophorone-based fluorescent probes, <b>MAP-X</b> (X = 2F, 2Cl, 2Br, F, Cl, Br), among which <b>MAP-2F</b> exhibits dual-emission fluorescence with high selectivity, enabling real-time visualization and simultaneous imaging of MAO-A (660 nm) and LOX (530 nm) in neuronal cells. By conducting experiments on neuronal cell models of Alzheimer's disease (AD) treated with Aβ₄₂ oligomers, aggregates, and glutamate, the probe successfully detected dynamic changes in MAO-A and LOX. Further screening of 20 AD-related natural products revealed that several of them exhibited significant inhibitory effects on MAO-A and LOX, and were associated with the production, clearance, or activity of Aβ protein. These results indicate a close relationship between the expression of MAO-A and LOX and changes in Aβ protein levels. The simultaneous detection of MAO-A and LOX in AD-model cells provides an approach for studying the pathological mechanisms of AD and developing potential therapeutic targets.