Label-free quantitative mass spectrometry reveals novel pathways involved in LL-37 expression

J Innate Immun. 2014;6(3):365-76. doi: 10.1159/000355931. Epub 2013 Nov 16.


Antimicrobial peptides are important for a healthy host-microbe homeostasis. In infections characterized by low levels of the human cathelicidin, LL-37, induction of its expression increases clearance of pathogens. Our aim was to discover signaling pathways and compounds capable of affecting the expression of LL-37. We recently observed a synergistic induction of LL-37 expression by stimulating the colonic epithelial cell-line HT-29 with lactose and phenylbutyrate (PBA). Here, we studied regulatory circuits mediating this synergism in HT-29 cells stimulated with lactose (60 g/l) and PBA (2 mM) for 24 h by using mass spectrometry and pathway analyses. Selected pathways were evaluated for their involvement in LL-37 regulation in a CAMP gene-luciferase reporter system. Three pathways were examined in detail: thyroid hormone receptor and retinoid X receptor (TR/RXR) activation, eicosanoid signaling and steroid biosynthesis. Induced expression of LL-37 was observed upon stimulation with triiodothyronine (T3, 2.5 nM-1 µM for 3-30 h) and thyroxine (T4, 2.5-10 nM for 24 h). Furthermore, the synergism of lactose and PBA was reduced in cells coincubated with inhibitors of phospholipase A2, cyclooxygenase 2 or HMG-CoA reductase. Based on these results, we conclude that proteomics and pathway analyses are valuable tools for dissecting the regulatory networks involved in LL-37 expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / metabolism*
  • Cathelicidins
  • Computational Biology
  • Drug Synergism
  • Gene Expression Regulation*
  • HT29 Cells
  • Humans
  • Immunity, Innate
  • Intestinal Mucosa / drug effects*
  • Intestinal Mucosa / immunology
  • Lactose / metabolism
  • Mass Spectrometry
  • Phenylbutyrates / metabolism
  • Proteomics
  • Receptors, Eicosanoid / metabolism
  • Receptors, Thyroid Hormone / metabolism
  • Retinoid X Receptors / metabolism
  • Signal Transduction*
  • Steroids
  • Thyroxine / metabolism
  • Triiodothyronine / metabolism


  • Antimicrobial Cationic Peptides
  • Phenylbutyrates
  • Receptors, Eicosanoid
  • Receptors, Thyroid Hormone
  • Retinoid X Receptors
  • Steroids
  • Triiodothyronine
  • Lactose
  • Thyroxine
  • Cathelicidins