title: Label-free quantitative mass spectrometry reveals novel pathways involved in LL-37 expression.
abstract: 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.
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Cederlund
authors.forename: Frank
authors.initials: F
authors.lastname: Nylén
authors.forename: Erica
authors.initials: E
authors.lastname: Miraglia
authors.forename: Peter
authors.initials: P
authors.lastname: Bergman
authors.forename: Gudmundur H
authors.initials: GH
authors.lastname: Gudmundsson
authors.forename: Birgitta
authors.initials: B
authors.lastname: Agerberth
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D004357:Drug Synergism; D005786:Gene Expression Regulation; D019073:HT29 Cells; D006801:Humans; D007113:Immunity, Innate; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000276:immunology; D007785:Lactose / Q000378:metabolism; D013058:Mass Spectrometry; D010654:Phenylbutyrates / Q000378:metabolism; D040901:Proteomics; D018055:Receptors, Eicosanoid / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000378:metabolism; D047488:Retinoid X Receptors / Q000378:metabolism; D015398:Signal Transduction; D013256:Steroids; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D010654:Phenylbutyrates; D018055:Receptors, Eicosanoid; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; D013256:Steroids; D014284:Triiodothyronine; D007785:Lactose; D013974:Thyroxine; D054804:Cathelicidins