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Journal of Neural Transmission

, Volume 112, Issue 3, pp 331–347 | Cite as

Inhibition of microglial activation by the herbal flavonoid baicalein attenuates inflammation-mediated degeneration of dopaminergic neurons

  • F.-Q. Li
  • T. Wang
  • Z. Pei
  • B. Liu
  • J.-S. Hong
Article

Summary.

Accumulating evidence has suggested that inflammation in the brain participates in the pathogenesis of Parkinson’s disease (PD). Therefore, anti-inflammatory therapy has attracted much attention as novel interference to neurodegenerative diseases. Baicalein, a major flavonoid extracted from a traditional Chinese herb Scutellaria baicalensis Georgi (Huangqin), possesses potent anti-inflammatory and antioxidant properties. To test the potential neuroprotective effect of baicalein on dopaminergic neurons, primary midbrain neuron-glia cultures from E-14 rat embryos were used. Cultures were pretreated with baicalein for 30 min prior to stimulation with lipopolysaccharide (LPS, 10 ng/ml). LPS leads to massive activation of microglial cells revealed by OX-42 immunostaining, and produced excessive quantities of NO. Excessive elevation of superoxide level was also observed in enriched-microglia after stimulating with LPS. LPS-induced damage to dopaminergic neurons was evaluated by uptake capacity for [3H]dopamine and tyrosine hydroxylase (TH)-immunocytochemistry. Pretreatment with baicalein concentration-dependently attenuated LPS-induced decrease in [3H]dopamine uptake and loss of TH-immunoreactive (TH-ir) neurons, which the maximum protective effect was observed at the concentration of 5 µM. Post-treatment with baicalein (5 µM) was also shown to be effective even if baicalein administered up to 2 h later than LPS application. Morphological study shows that baicalein (5 µM) almost completely blocked LPS-induced activation of microglia. Excessive production of TNFα and free radicals such as NO and superoxide by LPS stimulation were also attenuated by baicalein at a concentration-dependent pattern. The present study indicates that baicalein exerts potent neuroprotective effect on LPS-induced injury of dopaminergic neurons. We hypothesize that the inhibition of LPS-induced production of NO and free radicals from microglia may underlie the mechanism of baicalein’s neuroprotection.

Keywords: Baicalein, neuroprotection, neurodegeneration, inflammation, microglia, Dopaminergic neuron. 

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Copyright information

© Springer-Verlag/Wien 2004

Authors and Affiliations

  • F.-Q. Li
    • 1
  • T. Wang
    • 1
  • Z. Pei
    • 1
  • B. Liu
    • 1
  • J.-S. Hong
    • 1
  1. 1.Neuropharmacology Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle ParkNorth CarolinaUSA

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