Protective Effect of 20(S)-Protopanaxadiol on D-Gal-Induced Cognitively Impaired Mice Based on Its Target Protein Brain-type Creatine Kinase.

Ginseng is an important medicinal herb consumed as dietary supplements. Ginsenosides and their metabolites have been reported to enhance cognitive performance, but their underlying mechanisms remain unclear. Brain-type creatine kinase (CK-BB) was previously screened out as one of the potential targets in brain tissues. In vitro, the strongest direct interaction between 20(S)-protopanaxadiol (PPD), a ginsenoside metabolite, and CK-BB was detected using biolayer interferometry (BLI). Drug affinity responsive target stability, cellular thermal shift assay, BLI, and isothermal titration calorimetry were subsequently used, and the binding of PPD to CK-BB was verified. The binding sites of the CK-BB/PPD complex were clarified by molecular docking and site-directed mutagenesis. Enzyme activity assay showed that the binding of PPD to CK-BB in vitro enhanced its activity. In vivo, PPD increased CK-BB activity in D-gal-induced mice. PPD also improved the D-gal-induced cognitive deficits and ameliorated alterations in oxidative stress and hippocampal synaptic plasticity. Therefore, the integration of PPD with its target protein CK-BB may promote CK-BB activity, thereby ameliorating hippocampal synaptic plasticity and cognitive deficits in D-gal-treated mice.