Protective effect of naringenin against experimental colitis via suppression of Toll-like receptor 4/NF-κB signalling

Br J Nutr. 2013 Aug;110(4):599-608. doi: 10.1017/S0007114512005594. Epub 2013 Mar 18.

Abstract

Naringenin, one of the most abundant flavonoids in citrus, grapefruits and tomatoes, has been used as a traditional anti-inflammatory agent for centuries. However, the molecular mechanism of naringenin in intestinal inflammation remains unknown so far. The present study investigated a molecular basis for the protective effect of naringenin in dextran sulphate sodium-induced murine colitis. Pre-administration of naringenin significantly reduced the severity of colitis and resulted in down-regulation of pro-inflammatory mediators (inducible NO synthase (iNOS), intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), cyclo-oxygenase-2 (Cox2), TNF-α and IL-6 mRNA) in the colon mucosa. The decline in the production of pro-inflammatory cytokines, specifically TNF-α and IL-6, correlated with a decrease in mucosal Toll-like receptor 4 (TLR4) mRNA and protein. Phospho-NF-κB p65 protein was significantly decreased, which correlated with a similar decrease in phospho-IκBα protein. Consistent with the in vivo results, naringenin exposure blocked lipopolysaccharide-stimulated nuclear translocation of NF-κB p65 in mouse macrophage RAW264.7 cells. In addition, in vitro NF-κB reporter assays performed on human colonic HT-29 cells exposed to naringenin demonstrated a significant inhibition of TNF-α-induced NF-κB luciferase expression. Thus, for the first time, the present study indicates that targeted inhibition of the TLR4/NF-κB signalling pathway might be an important mechanism for naringenin in abrogating experimental colitis.

Publication types

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

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology
  • Cell Line
  • Colitis / chemically induced*
  • Colitis / prevention & control*
  • Cytokines / metabolism
  • Dextran Sulfate / pharmacology
  • Dietary Supplements
  • Female
  • Flavanones / pharmacology*
  • Flavonoids / pharmacology
  • Inflammation
  • Luciferases / metabolism
  • Mice
  • Mice, Inbred C57BL
  • NF-kappa B / metabolism*
  • Signal Transduction
  • Toll-Like Receptor 4 / metabolism*

Substances

  • Anti-Inflammatory Agents
  • Cytokines
  • Flavanones
  • Flavonoids
  • NF-kappa B
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Dextran Sulfate
  • Luciferases
  • naringenin