Activation of the Keap1/Nrf2 pathway for neuroprotection by electrophilic [correction of electrophillic] phase II inducers

Proc Natl Acad Sci U S A. 2006 Jan 17;103(3):768-73. doi: 10.1073/pnas.0505723102. Epub 2006 Jan 9.

Abstract

Electrophilic neurite outgrowth-promoting prostaglandin (NEPP) compounds protect neurons from oxidative insults. At least part of the neuroprotective action of NEPPs lies in induction of hemeoxygenase-1 (HO-1), which, along with other phase II enzymes, serve as a defense system against oxidative stress. Here, we found that, by using fluorescent tags and immunoprecipitation assays, NEPPs are taken up preferentially into neurons and bind in a thiol-dependent manner to Keap1, a negative regulator of the transcription factor Nrf2. By binding to Keap1, NEPPs prevent Keap1-mediated inactivation of Nrf2 and, thus, enhance Nrf2 translocation into the nucleus of cultured neuronal cells. In turn, Nrf2 binds to antioxidant/electrophile-responsive elements of the HO-1 promoter to induce HO-1 expression. Consistent with this notion, NEPP induction of an HO-1 reporter construct is prevented if the antioxidant-responsive elements are mutated. We show that NEPPs are neuroprotective both in vitro from glutamate-related excitotoxicity and in vivo in a model of cerebral ischemia/reperfusion injury (stroke). Our results suggest that NEPPs prevent excitotoxicity by activating the Keap1/Nrf2/HO-1 pathway. Because NEPPs accumulate preferentially in neurons, they may provide a category of neuroprotective compounds, distinct from other electrophilic compounds such as tert-butylhydroquinone, which activates the antioxidant-responsive element in astrocytes. NEPPs thus represent a therapeutic approach for stroke and neurodegenerative disorders.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cerebral Cortex / cytology
  • Cerebral Cortex / physiology
  • Enzyme Induction
  • Heme Oxygenase-1 / biosynthesis
  • Heme Oxygenase-1 / genetics
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Kelch-Like ECH-Associated Protein 1
  • Metabolic Detoxication, Phase II / physiology*
  • NF-E2-Related Factor 2 / metabolism
  • NF-E2-Related Factor 2 / physiology*
  • Neurons / enzymology*
  • Neuroprotective Agents / metabolism*
  • Neuroprotective Agents / pharmacology
  • Oxidative Stress / physiology*
  • Proteins / metabolism
  • Proteins / physiology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*

Substances

  • Intracellular Signaling Peptides and Proteins
  • KEAP1 protein, human
  • Kelch-Like ECH-Associated Protein 1
  • NF-E2-Related Factor 2
  • NFE2L2 protein, human
  • Neuroprotective Agents
  • Proteins
  • Heme Oxygenase-1