Design, synthesis, and biological evaluation of Benzimidazole-Aminopyrimidine hybrids as selective P38α MAPK inhibitors targeting Neuroinflammation in an AlCl-induced rat model of Alzheimer's disease.

Abstract

p38α MAP kinase is a key driver of neuroinflammation in Alzheimer's disease (AD). It plays a crucial role in initiating the release of proinflammatory cytokines such as TNF-α and IL-1β. A novel series of benzimidazole-aminopyrimidine-hybrids (4a-m) was designed and synthesized as selective p38α inhibitors by combining two purine isosteric scaffolds with a flexible methyl thioether linker. Targets 4a-m were synthesized in good to excellent yields, characterized using NMR spectroscopy and mass spectrometry, and their purity was confirmed using elemental analysis. Docking and molecular dynamics studies suggested that several compounds bind strongly to p38α. Enzyme assays confirmed that four derivatives (4c, 4d, 4i, and 4j) inhibit p38α in the low-nanomolar range (IC₅₀ ≈ 26-46 nM) with much weaker activity on p38β, p38γ, and p38δ, indicating an α-selective profile. Among them, 4i showed the lowest IC₅₀ value (≈26 nM). Predicted blood-brain barrier (BBB) permeability parameters highlighted 4c and 4d as the best candidates for in vivo testing. Their neuroprotective effects were examined in an AlCl₃-induced Alzheimer's-like rat model. Both compounds showed good in silico BBB permeability and were tested in an AlCl₃-induced rat model of Alzheimer's disease. Treatment with 4c and 4d significantly decreased brain concentrations of NF-κB p65 by 35 % and 25 %, respectively, TNF-α (33 % and 20 %, respectively), and IL-1β (39 % and 20 %, respectively), along with notable histopathological improvement in cortical and hippocampal tissues. These findings collectively designate 4c as a robust, brain-penetrable p38α-targeting inhibitor that mitigates AD-associated neuroinflammation, signifying it as a promising candidate for subsequent development.