Silibinin attenuates amyloid beta(25-35) peptide-induced memory impairments: implication of inducible nitric-oxide synthase and tumor necrosis factor-alpha in mice

J Pharmacol Exp Ther. 2009 Oct;331(1):319-26. doi: 10.1124/jpet.109.155069. Epub 2009 Jul 28.


In Alzheimer's disease (AD), the deposition of amyloid peptides is invariably associated with oxidative stress and inflammatory responses. Silibinin (silybin), a flavonoid derived from the herb milk thistle, has potent anti-inflammatory and antioxidant activities. However, it remains unclear whether silibinin improves amyloid beta (Abeta) peptide-induced neurotoxicity. In this study, we examined the effect of silibinin on the fear-conditioning memory deficits, inflammatory response, and oxidative stress induced by the intracerebroventricular injection of Abeta peptide(25-35) (Abeta(25-35)) in mice. Mice were treated with silibinin (2, 20, and 200 mg/kg p.o., once a day for 8 days) from the day of the Abeta(25-35) injection (day 0). Memory function was evaluated in cued and contextual fear-conditioning tests (day 6). Nitrotyrosine levels in the hippocampus and amygdala were examined (day 8). The mRNA expression of inducible nitric-oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) in the hippocampus and amygdala was measured 2 h after the Abeta(25-35) injection. We found that silibinin significantly attenuated memory deficits caused by Abeta(25-35) in the cued and contextual fear-conditioning test. Silibinin significantly inhibited the increase in nitrotyrosine levels in the hippocampus and amygdala induced by Abeta(25-35). Nitrotyrosine levels in these regions were negatively correlated with memory performance. Moreover, real-time RT-PCR revealed that silibinin inhibited the overexpression of iNOS and TNF-alpha mRNA in the hippocampus and amygdala induced by Abeta(25-35). These findings suggest that silibinin (i) attenuates memory impairment through amelioration of oxidative stress and inflammatory response induced by Abeta(25-35) and (ii) may be a potential candidate for an AD medication.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid beta-Peptides / toxicity*
  • Animals
  • Antioxidants / pharmacology
  • Antioxidants / therapeutic use
  • Drug Synergism
  • Inflammation Mediators / therapeutic use
  • Male
  • Memory Disorders / chemically induced
  • Memory Disorders / enzymology
  • Memory Disorders / metabolism*
  • Memory Disorders / prevention & control*
  • Mice
  • Mice, Inbred ICR
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Nitric Oxide Synthase Type II / biosynthesis*
  • Nitric Oxide Synthase Type II / genetics
  • Peptide Fragments / toxicity*
  • RNA, Messenger / biosynthesis
  • Silybin
  • Silymarin / pharmacology
  • Silymarin / therapeutic use
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors
  • Tumor Necrosis Factor-alpha / biosynthesis*
  • Tumor Necrosis Factor-alpha / genetics
  • Tyrosine / analogs & derivatives
  • Tyrosine / biosynthesis
  • Up-Regulation / drug effects
  • Up-Regulation / genetics


  • Amyloid beta-Peptides
  • Antioxidants
  • Inflammation Mediators
  • Peptide Fragments
  • RNA, Messenger
  • Silymarin
  • Tumor Necrosis Factor-alpha
  • amyloid beta-protein (25-35)
  • 3-nitrotyrosine
  • Tyrosine
  • Silybin
  • Nitric Oxide Synthase Type II