Attenuation of Aβ25-35-induced parallel autophagic and apoptotic cell death by gypenoside XVII through the estrogen receptor-dependent activation of Nrf2/ARE pathways

Toxicol Appl Pharmacol. 2014 Aug 15;279(1):63-75. doi: 10.1016/j.taap.2014.03.026. Epub 2014 Apr 12.

Abstract

Amyloid-beta (Aβ) has a pivotal function in the pathogenesis of Alzheimer's disease. To investigate Aβ neurotoxicity, we used an in vitro model that involves Aβ25-35-induced cell death in the nerve growth factor-induced differentiation of PC12 cells. Aβ25-35 (20μM) treatment for 24h caused apoptotic cell death, as evidenced by significant cell viability reduction, LDH release, phosphatidylserine externalization, mitochondrial membrane potential disruption, cytochrome c release, caspase-3 activation, PARP cleavage, and DNA fragmentation in PC12 cells. Aβ25-35 treatment led to autophagic cell death, as evidenced by augmented GFP-LC3 puncta, conversion of LC3-I to LC3-II, and increased LC3-II/LC3-I ratio. Aβ25-35 treatment induced oxidative stress, as evidenced by intracellular ROS accumulation and increased production of mitochondrial superoxide, malondialdehyde, protein carbonyl, and 8-OHdG. Phytoestrogens have been proved to be protective against Aβ-induced neurotoxicity and regarded as relatively safe targets for AD drug development. Gypenoside XVII (GP-17) is a novel phytoestrogen isolated from Gynostemma pentaphyllum or Panax notoginseng. Pretreatment with GP-17 (10μM) for 12h increased estrogen response element reporter activity, activated PI3K/Akt pathways, inhibited GSK-3β, induced Nrf2 nuclear translocation, augmented antioxidant responsive element enhancer activity, upregulated heme oxygenase 1 (HO-1) expression and activity, and provided protective effects against Aβ25-35-induced neurotoxicity, including oxidative stress, apoptosis, and autophagic cell death. In conclusion, GP-17 conferred protection against Aβ25-35-induced neurotoxicity through estrogen receptor-dependent activation of PI3K/Akt pathways, inactivation of GSK-3β and activation of Nrf2/ARE/HO-1 pathways. This finding might provide novel insights into understanding the mechanism for neuroprotective effects of phytoestrogens or gypenosides.

Keywords: Alzheimer's disease; Apoptosis; Autophagy; Nuclear factor-erythroid 2-related factor 2; Oxidative stress; Phytoestrogen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid beta-Peptides* / antagonists & inhibitors
  • Amyloid beta-Peptides* / toxicity
  • Animals
  • Apoptosis* / drug effects
  • Autophagy* / drug effects
  • Blotting, Western
  • Caspase 3 / metabolism
  • Cell Differentiation / drug effects
  • Cell Survival / drug effects
  • Fluorescent Antibody Technique
  • Gynostemma
  • Heme Oxygenase-1 / biosynthesis
  • Membrane Potential, Mitochondrial / drug effects
  • NF-E2-Related Factor 2 / physiology
  • Neuroprotective Agents* / pharmacology
  • Oxidative Stress / drug effects
  • PC12 Cells
  • Peptide Fragments* / antagonists & inhibitors
  • Peptide Fragments* / toxicity
  • Phosphatidylinositol 3-Kinases / metabolism
  • Plant Extracts / pharmacology
  • Rats
  • Reactive Oxygen Species / metabolism
  • Receptors, Estrogen* / drug effects
  • Signal Transduction
  • Transfection

Substances

  • Amyloid beta-Peptides
  • amyloid beta-protein (25-35)
  • Caspase 3
  • gypenoside
  • Heme Oxygenase-1
  • Neuroprotective Agents
  • Peptide Fragments
  • Phosphatidylinositol 3-Kinases
  • Plant Extracts
  • Reactive Oxygen Species
  • Receptors, Estrogen
  • NF-E2-Related Factor 2
  • Nfe2l2 protein, rat