Identification, biological evaluation, and crystallographic analysis of coumestrol as a novel dual-specificity tyrosine-phosphorylation-regulated kinase 1A inhibitor

Alzheimer's disease (AD) is an irreversible neurodegenerative disease, with tau pathology caused by abnormally activated dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) being one of the culprits. Coumestrol, a phytoestrogen and natural antioxidant found in various plants, has been reported to alleviate AD, but the underlying mechanism remains unclear. We confirmed coumestrol as a novel DYRK1A inhibitor through enzyme-based assays, X-ray crystallography, and cell line experiments. Coumestrol exhibited minimal cytotoxicity at concentrations up to 100 μM in cell types such as N2A and SH-SY5Y and reduced DYRK1A-induced phosphorylated tau protein levels by >50 % at 60 μM. In the tau protein phosphorylation and microtubule assembly assay, coumestrol at 30 μM reduced phosphorylated tau by >50 % and restored the microtubule assembly process. Coumestrol also significantly reduced amyloid-β (Aβ)-induced oxidative stress in microglia at 1 μM. In zebrafish larvae co-overexpressing DYRK1A and tau, coumestrol mitigated neuronal damage and protected motor function at 48 h-postfertilization. Our results suggest that coumestrol has potential therapeutic effects in AD by inhibiting DYRK1A, lowering p-Tau levels, restoring microtubule assembly, and protecting microglia cells from Aβ-induced cell death, providing new insights into the development of coumestrol as a potential AD treatment.