Neuroprotective Effect of 6-paradol in Focal Cerebral Ischemia Involves the Attenuation of Neuroinflammatory Responses in Activated Microglia

PLoS One. 2015 Mar 19;10(3):e0120203. doi: 10.1371/journal.pone.0120203. eCollection 2015.

Abstract

Paradols are non-pungent and biotransformed metabolites of shogaols and reduce inflammatory responses as well as oxidative stress as shogaols. Recently, shogaol has been noted to possess therapeutic potential against several central nervous system (CNS) disorders, including cerebral ischemia, by reducing neuroinflammation in microglia. Therefore, paradol could be used to improve neuroinflammation-associated CNS disorders. Here, we synthesized paradol derivatives (2- to 10-paradols). Through the initial screening for anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated BV2 microglia, 6-paradol was chosen to be the most effective compound without cytotoxicity. Pretreatment with 6-paradol reduced neuroinflammatory responses in LPS-stimulated BV2 microglia by a concentration-dependent manner, which includes reduced NO production by inhibiting iNOS upregulation and lowered secretion of proinflammatory cytokines (IL-6 and TNF-α). To pursue whether the beneficial in vitro effects of 6-paradol leads towards in vivo therapeutic effects on transient focal cerebral ischemia characterized by neuroinflammation, we employed middle cerebral artery occlusion (MCAO)/reperfusion (M/R). Administration of 6-paradol immediately after reperfusion significantly reduced brain damage in M/R-challenged mice as assessed by brain infarction, neurological deficit, and neural cell survival and death. Furthermore, as observed in cultured microglia, 6-paradol administration markedly reduced neuroinflammation in M/R-challenged brains by attenuating microglial activation and reducing the number of cells expressing iNOS and TNF-α, both of which are known to be produced in microglia following M/R challenge. Collectively, this study provides evidences that 6-paradol effectively protects brain after cerebral ischemia, likely by attenuating neuroinflammation in microglia, suggesting it as a potential therapeutic agent to treat cerebral ischemia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Brain / drug effects
  • Brain / metabolism
  • Brain / pathology
  • Brain Ischemia / drug therapy
  • Brain Ischemia / metabolism
  • Brain Ischemia / pathology*
  • Cell Line
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Guaiacol / analogs & derivatives*
  • Guaiacol / chemical synthesis
  • Guaiacol / pharmacology
  • Guaiacol / therapeutic use
  • Interleukin-6 / analysis
  • Interleukin-6 / metabolism
  • Ketones / chemical synthesis
  • Ketones / pharmacology*
  • Ketones / therapeutic use
  • Lipopolysaccharides / toxicity
  • Male
  • Mice
  • Mice, Inbred ICR
  • Microglia / cytology
  • Microglia / drug effects*
  • Microglia / metabolism
  • Neuroprotective Agents / chemical synthesis
  • Neuroprotective Agents / pharmacology*
  • Neuroprotective Agents / therapeutic use
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / metabolism
  • Reperfusion Injury / pathology
  • Reperfusion Injury / prevention & control
  • Tumor Necrosis Factor-alpha / analysis
  • Tumor Necrosis Factor-alpha / metabolism
  • Up-Regulation / drug effects

Substances

  • Interleukin-6
  • Ketones
  • Lipopolysaccharides
  • Neuroprotective Agents
  • Tumor Necrosis Factor-alpha
  • Nitric Oxide
  • Guaiacol
  • 6-paradol
  • Nitric Oxide Synthase Type II

Grant support

This work was supported by the National Research Foundation of Republic of Korea (NRF-2013R1A1A1A05005520, NRF-2012R1A1A1007057); the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI13C18200000); Research program for Gachon Pharmaceutical Sciences. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.