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.