Targeting cholinergic dysfunction and neuroinflammation through rationally designed Thieno[3,2-d]pyrimidine hybrids

Neurodegenerative diseases involve the convergence of cholinergic dysfunction, neuronal loss, and sustained neuroinflammatory responses, necessitating the development of multifunctional therapeutic agents. In this study, a series of novel thieno[3,2-d]pyrimidine-phenolic Mannich base hybrids were rationally designed, synthesized, and evaluated as dual cholinesterase inhibitors with neuroprotective and anti-neuroinflammatory potential. The synthesized compounds exhibited potent inhibition against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), with inhibition constants in the low nanomolar range. Among them, compounds 5 and 9 emerged as the most active derivatives, displaying K_i values of 8.79 and 14.11 nM for AChE and 7.04 and 11.75 nM for BChE, surpassing the reference inhibitors tacrine and donepezil. Molecular docking and molecular dynamics simulations supported the experimental findings, and Molecular Mechanics-Generalized Born Surface Area (MM-GBSA) binding free energy calculations further confirmed their superior binding affinities compared with donepezil. Cytotoxicity profiling in SH-SY5Y neuronal cells and RAW 264.7 and THP-1 immune cells identified a narrow sub-cytotoxic concentration window (EC₀₅-EC₁₀ = 1.2-2.1 μM), ensuring biological effects independent of nonspecific cell damage. Within this range, both compounds exerted pronounced anti-neuroinflammatory activity. Notably, compound 9 significantly downregulated pro-inflammatory mediators, reducing IL-1β, IL-6, and NF-κB1 gene expression by up to 2.78-, 3.37-, and 4.84-fold, respectively. Consistently, it suppressed nitric oxide production in LPS-stimulated macrophages to levels comparable with ascorbic acid and markedly decreased Iba1 expression in activated THP-1 cells. This integrated enzymatic, computational, and cellular investigation identifies compounds 5 and 9 as promising multifunctional lead combining dual cholinesterase inhibition with robust anti-neuroinflammatory activity. The results provide a strong foundation for future in vivo studies and further optimization toward disease-modifying agents for neurodegenerative disorders.