Protection of hippocampal neurogenesis from toll-like receptor 4-dependent innate immune activation by ablation of prostaglandin E2 receptor subtype EP1 or EP2

Am J Pathol. 2009 Jun;174(6):2300-9. doi: 10.2353/ajpath.2009.081153. Epub 2009 Apr 23.

Abstract

Prostaglandin E2 is one of several eicosanoid products of the cyclooxygenase isozymes and is a key regulator of innate immune responses; it also possesses paracrine effects on mature neurons. The prostaglandin E2 receptor family consists of four subtypes of which EP1 and EP2 are known to be expressed by microglia. Lipopolysaccharide (LPS)-induced innate immune activation leads to the degeneration of intermediate progenitor cells (IPCs) that are destined for neuronal maturation in the hippocampal subgranular zone (SGZ); these cells can be identified by the expression of the transcription factor T-box brain gene 2 (Tbr2). Importantly, depletion of LPS-induced IPCs from the SGZ is suppressed by cyclooxygenase inhibitors. We therefore tested the hypothesis that either EP1 or EP2 is critical to LPS-induced depletion of Tbr2+ IPCs from the SGZ. Expression of either EP1 or EP2 was necessary for Toll-like receptor 4-dependent innate immune-mediated depletion of these Tbr2+ IPCs in mice. Moreover, EP1 activation was directly toxic to murine adult hippocampal progenitor cells; EP2 was not expressed by these cells. Finally, EP1 modulated the response of murine primary microglia cultures to LPS but in a manner distinct from EP2. These results indicate that prostaglandin E2 signaling via either EP1 or EP2 is largely to completely necessary for Toll-like receptor 4-dependent depletion of IPCs from the SGZ and suggest further pharmacological strategies to protect this important neurogenic niche.

Publication types

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

MeSH terms

  • Animals
  • Fluorescent Antibody Technique
  • Hippocampus / cytology*
  • Hippocampus / immunology
  • Hippocampus / metabolism
  • Immunity, Innate
  • Lipopolysaccharides / immunology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • Neurogenesis / immunology*
  • Neurons / immunology
  • Neurons / metabolism
  • Receptors, Prostaglandin E / metabolism*
  • Receptors, Prostaglandin E, EP1 Subtype
  • Receptors, Prostaglandin E, EP2 Subtype
  • Reverse Transcriptase Polymerase Chain Reaction
  • Stem Cells / cytology
  • Stem Cells / immunology
  • Stem Cells / metabolism*
  • T-Box Domain Proteins / biosynthesis
  • Toll-Like Receptor 4 / immunology
  • Toll-Like Receptor 4 / metabolism*

Substances

  • Eomes protein, mouse
  • Lipopolysaccharides
  • Ptger1 protein, mouse
  • Ptger2 protein, mouse
  • Receptors, Prostaglandin E
  • Receptors, Prostaglandin E, EP1 Subtype
  • Receptors, Prostaglandin E, EP2 Subtype
  • T-Box Domain Proteins
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4