Histone H3K9 methylation regulates chronic stress and IL-6-induced colon epithelial permeability and visceral pain

Neurogastroenterol Motil. 2020 Dec;32(12):e13941. doi: 10.1111/nmo.13941. Epub 2020 Aug 2.

Abstract

Background: Chronic stress is associated with activation of the HPA axis, elevation in pro-inflammatory cytokines, decrease in intestinal epithelial cell tight junction (TJ) proteins, and enhanced visceral pain. It is unknown whether epigenetic regulatory pathways play a role in chronic stress-induced intestinal barrier dysfunction and visceral hyperalgesia.

Methods: Young adult male rats were subjected to water avoidance stress ± H3K9 methylation inhibitors or siRNAs. Visceral pain response was assessed. Differentiated Caco-2/BBE cells and human colonoids were treated with cortisol or IL-6 ± antagonists. Expression of TJ, IL-6, and H3K9 methylation status at gene promoters was measured. Transepithelial electrical resistance and FITC-dextran permeability were evaluated.

Key results: Chronic stress induced IL-6 up-regulation prior to a decrease in TJ proteins in the rat colon. The IL-6 level inversely correlated with occludin expression. Treatment with IL-6 decreased occludin and induced visceral hyperalgesia. Chronic stress and IL-6 increased H3K9 methylation and decreased transcriptional GR binding to the occludin gene promoter, leading to down-regulation of protein expression and increase in paracellular permeability. Intrarectal administration of a H3K9 methylation antagonist prevented chronic stress-induced visceral hyperalgesia in the rat. In a human colonoid model, cortisol decreased occludin expression, which was prevented by the GR antagonist RU486, and IL-6 increased H3K9 methylation and decreased TJ protein levels, which were prevented by inhibitors of H3K9 methylation.

Conclusions & inferences: Our findings support a novel role for methylation of the repressive histone H3K9 to regulate chronic stress, pro-inflammatory cytokine-mediated reduction in colon TJ protein levels, and increase in paracellular permeability and visceral hyperalgesia.

Keywords: chronic stress; epithelial cell tight junctions; histone methylation; pro-inflammatory cytokines; visceral hyperalgesia.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Caco-2 Cells
  • Chronic Disease
  • Colon / metabolism*
  • Epithelium / metabolism
  • Histones / antagonists & inhibitors
  • Histones / metabolism*
  • Humans
  • Interleukin-6 / biosynthesis*
  • Male
  • Methylation
  • Permeability*
  • Quinazolines / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Stress, Psychological / complications
  • Stress, Psychological / metabolism*
  • Stress, Psychological / psychology
  • Visceral Pain / etiology
  • Visceral Pain / metabolism*
  • Visceral Pain / psychology

Substances

  • Histones
  • Interleukin-6
  • Quinazolines
  • UNC0642