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Protopanaxatriol restores cognitive function in okadaic acid-treated mice via direct inhibition of pathological CDK5 activity

Acta Pharmacologica Sinica (2026)Cite this article

Abstract

Alzheimer’s disease (AD), a prevalent neurodegenerative dementia, presents therapeutic challenges due to safety concerns about amyloid-targeting strategies. Traditional Chinese medicine (TCM) may offer alternative avenues for exploration. Ginsenoside Rg1, a key bioactive component of ginseng, has shown neuroprotective potential in okadaic acid (OKA)-induced rat model, its limited brain bioavailability suggests that its metabolite protopanaxatriol (Ppt) may exert these effects. In this study, we investigated the therapeutic effects of Ppt on OKA-induced mice model and the underlying mechanisms. Cultured hippocampal neurons were treated with OKA (0.5 nM) with or without Ppt co-treatment for 24 h. We showed that Ppt (1.25–40 nM) exerted dose-dependent neuroprotection against OKA-induced cytotoxicity, with the maximal protection observed at 10 nM. The suppressed tau aggregation by Ppt was confirmed using a Venus-tau bimolecular fluorescence complementation (BiFC) system. Molecular dynamics simulations and microscale thermophoresis (MST) revealed that Ppt bound to the catalytic domain of CDK5 at Cys83, destabilizing the CDK5/p25 complex. Co-immunoprecipitation (Co-IP) assays with CDK5 mutants (S159T, C83A, F80A and D86A) validated this interaction. In vivo mice were treated with Ppt (10 mg/kg, i.g.) for 25 days. On D8 and D9, the mice were bilaterally microinjected with OKA into the cerebral ventricles. We showed that Ppt administration improved spatial memory deficits in Novel Object Recognition and Barnes Maze tests; these effects were abolished in mice expressing a lentivirus-mediated CDK5[C83A] mutant. Hippocampal transcriptomic profiling in OKA-challenged mice following Ppt intervention revealed that Ppt modulated Drp1-mediated mitochondrial fission/fusion dynamics, mitigating OKA-induced mitochondrial homeostasis disruption. Collectively, these results demonstrate that Ppt attenuates tau pathology by selectively targeting CDK5 at Cys83, thereby reducing pathological kinase activity, rebalancing mitochondrial function, and improving cognitive outcomes in an OKA-induced mice neurodegeneration model. The study underscores the therapeutic potential of Ppt in AD treatment and supports CDK5 modulation as a strategic approach for addressing tau-related neurodegeneration.

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Fig. 1: The effects of Ppt on OKA-induced tau pathology.
Fig. 2: The effects of Ppt on OKA-induced abnormal hyperphosphorylation of CDK5.
Fig. 3: PPT inhibits OKA-induced tau pathology and memory impairment is CDK-Cys83-dependent in vivo.
Fig. 4: Gene expression analysis of hippocampus in OKA-induced AD mice model treated with Ppt.
Fig. 5: Ppt as a CDK5 inhibitor improves OKA-induced mitochondrial dysfunction.
Fig. 6: The effects of Ppt inhibition on OKA-induced mitochondrial fragmentation.
Fig. 7: Ppt inhibits Drp1 phosphorylation and protects mitochondrial damage.
Fig. 8: Schematic illustrating the neuroprotective actions of Ppt.

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Acknowledgements

This work was supported by the CAMS Innovation Fund for Medical Sciences (CIFMS) (2021-I2M-1-020), the Opening Program of the Shanxi Key Laboratory of Chinese Medicine Encephalopathy (2022JD-KF-20), the Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Guangxi Institute of Chinese Medicine & Pharmaceutical Science (GZZK) (202401), the Provincial Natural Science Foundation of Hunan (2025JJ60645). We sincerely appreciate Prof. Yun Kyung Kim and Dr. Lim Sungsu at the Korea Institute of Science and Technology for their generous donation of pCMV6-htau40-VN173 and pCMV6-htau40-VC155 plasmids.

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  1. These authors contributed equally: Ye Peng, Sha-sha Wang, Ke-dao Lai

Authors and Affiliations

  1. College of Pharmacy, Hunan University of Chinese Medicine, Changsha, 410208, China

    Ye Peng, Sha-sha Wang & Nai-hong Chen

  2. State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica & Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100050, China

    Ye Peng, Sha-sha Wang, Jun-rui Ye, Xu Yan, Zhao Zhang, Shi-feng Chu & Nai-hong Chen

  3. Guangxi Key Laboratory of Traditional Chinese Medicine Quality Standards, Guangxi Institute of Chinese Medicine & Pharmaceutical Science, Nanning, 530022, China

    Ye Peng & Ke-dao Lai

  4. Shanxi Key Laboratory of Chinese Medicine Encephalopathy, National International Joint Research Center for Molecular Chinese Medicine, Shanxi University of Chinese Medicine, Taiyuan, 030024, China

    Wen-bing He

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Contributions

NHC, ZZ, and YP designed the study. YP, SSW, KDL, JRY, and XY performed the experiments and drafted the manuscript; YP, SSW, ZZ, SFC, and NHC participated in data analysis; SFC, WBH, and KDL were involved in discussion of the experiments. All authors read and approved the final manuscript.

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Correspondence to Zhao Zhang, Shi-feng Chu or Nai-hong Chen.

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Peng, Y., Wang, Ss., Lai, Kd. et al. Protopanaxatriol restores cognitive function in okadaic acid-treated mice via direct inhibition of pathological CDK5 activity. Acta Pharmacol Sin (2026). https://doi.org/10.1038/s41401-025-01709-1

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