Protopine promotes the proteasomal degradation of pathological tau in Alzheimer's disease models via HDAC6 inhibition

Sravan Gopalkrishnashetty Sreenivasmurthy, Ashok Iyaswamy, Senthilkumar Krishnamoorthi, Sanjib Senapati, Sandeep Malampati, Zhou Zhu, Cheng Fu Su, Jia Liu, Xin Jie Guan, Benjamin Chun Kit Tong, King Ho Cheung, Jie Qiong Tan, Jia Hong Lu, Siva Sundara Kumar Durairajan*, Ju Xian Song*, Min Li*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Background

Collective evidences have indicated that intracellular accumulation of hyperphosphorylated tau forms neurofibrillary tangles in the brain, which impairs memory, cognition and affects social activities in Alzheimer's disease (AD). 

Purpose

To investigate the tau-reducing, and memory-enhancing properties of protopine (PRO), a natural alkaloid isolated from Chinese herbal medicine Corydalis yanhusuo (Yanhusuo in Chinese). 

Study design

By using Histone deacetylase 6 (HDAC6) profiling and immunoprecipitation assays, we assessed that PRO mediated the heat shock protein 90 (HSP90) chaperonic activities for the degradation of pathological tau in AD cell culture models. To study the efficacy of PRO in vivo, we employed 3xTg-AD and P301S tau mice models. 

Methods

Liquid chromatography/quadrupole time-of-flight mass spectrometry was used to analyze the pharmacokinetic profile of PRO. Seven-month-old 3xTg-AD mice and 1.5-month-old P301S mice were administered PRO (1 and 2.5 mg/kg) orally every day. Morris water maze, contextual fear conditioning and rotarod assays were applied for studying memory functions. Sarkosyl differential centrifugation was used to analyze soluble and insoluble tau. Immunohistochemical analysis were performed to determine tau deposits in AD mice's brain sections. Molecular docking, binding affinity studies and primary cell culture studies were performed to demonstrate the mechanism of action of PRO in silico and in vitro. 

Results

Our pharmacokinetic profiling demonstrated that PRO significantly entered the brain at a concentration of 289.47 ng/g, and specifically attenuated tau pathology, improved learning and memory functions in both 3xTg-AD and P301S mice. Docking, binding affinity studies, and fluorometric assays demonstrated that PRO directly bound to the catalytic domain 1 (CD1) of HDAC6 and down-regulated its activity. In primary cortical neurons, PRO enhanced acetylation of α-tubulin, indicating HDAC6 inhibition. Meanwhile, PRO promoted the ubiquitination of tau and recruited heat shock protein 70 (HSP70) and heat shock cognate complex 71 (HSC70) for the degradation of pathological tau via the ubiquitin-proteasomal system (UPS). 

Conclusion

We identified PRO as a natural HDAC6 inhibitor that attenuated tau pathology and improved memory dysfunctions in AD mice. The findings from this study provides a strong justification for future clinical development of plant-derived protopine as a novel agent for the treatment of tau-related neurodegenerative diseases.

Original languageEnglish
Article number153887
JournalPhytomedicine
Volume96
Early online date8 Dec 2021
DOIs
Publication statusPublished - Feb 2022

Scopus Subject Areas

  • Molecular Medicine
  • Pharmacology
  • Pharmaceutical Science
  • Drug Discovery
  • Complementary and alternative medicine

User-Defined Keywords

  • 3xTg-AD mice
  • Alzheimer's disease
  • HDAC6
  • P301S-tau mice
  • Phospho-tau
  • Protopine

Fingerprint

Dive into the research topics of 'Protopine promotes the proteasomal degradation of pathological tau in Alzheimer's disease models via HDAC6 inhibition'. Together they form a unique fingerprint.

Cite this