title: A novel role of a lipid species, sphingosine-1-phosphate, in epithelial innate immunity.
abstract: A variety of external perturbations can induce endoplasmic reticulum (ER) stress, followed by stimulation of epithelial cells to produce an innate immune element, the cathelicidin antimicrobial peptide (CAMP). ER stress also increases production of the proapoptotic lipid ceramide and its antiapoptotic metabolite, sphingosine-1-phosphate (S1P). We demonstrate here that S1P mediates ER stress-induced CAMP generation. Cellular ceramide and S1P levels rose in parallel with CAMP levels following addition of either exogenous cell-permeating ceramide (C2Cer), which increases S1P production, or thapsigargin (an ER stressor), applied to cultured human skin keratinocytes or topically to mouse skin. Knockdown of S1P lyase, which catabolizes S1P, enhanced ER stress-induced CAMP production in cultured cells and mouse skin. These and additional inhibitor studies show that S1P is responsible for ER stress-induced upregulation of CAMP expression. Increased CAMP expression is likely mediated via S1P-dependent NF-κB-C/EBPα activation. Finally, lysates of both ER-stressed and S1P-stimulated cells blocked growth of virulent Staphylococcus aureus in vitro, and topical C2Cer and LL-37 inhibited invasion of Staphylococcus aureus into murine skin. These studies suggest that S1P generation resulting in increased CAMP production comprises a novel regulatory mechanism of epithelial innate immune responses to external perturbations, pointing to a new therapeutic approach to enhance antimicrobial defense.
authors.affiliation: Department of Dermatology, School of Medicine, University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, California, USA.
authors.forename: Kyungho
authors.initials: K
authors.lastname: Park
authors.forename: Peter M
authors.initials: PM
authors.lastname: Elias
authors.forename: Kyoung-Oh
authors.initials: KO
authors.lastname: Shin
authors.forename: Yong-Moon
authors.initials: YM
authors.lastname: Lee
authors.forename: Melanie
authors.initials: M
authors.lastname: Hupe
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Borkowski
authors.forename: Richard L
authors.initials: RL
authors.lastname: Gallo
authors.forename: Julie
authors.initials: J
authors.lastname: Saba
authors.forename: Walter M
authors.initials: WM
authors.lastname: Holleran
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Uchida
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000276:immunology; D054804:Cathelicidins / Q000235:genetics / Q000276:immunology*; D002478:Cells, Cultured; D002518:Ceramides / Q000276:immunology; D059865:Endoplasmic Reticulum Stress; D005786:Gene Expression Regulation; D006801:Humans; D007113:Immunity, Innate; D015603:Keratinocytes / Q000276:immunology* / Q000382:microbiology; D008246:Lysophospholipids / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000276:immunology; D012867:Skin / Q000276:immunology* / Q000382:microbiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000276:immunology; D013203:Staphylococcal Infections / Q000276:immunology; D013211:Staphylococcus aureus / Q000254:growth & development / Q000276:immunology
chemical_list: D023181:Antimicrobial Cationic Peptides; D022763:CCAAT-Enhancer-Binding Protein-alpha; D054804:Cathelicidins; D002518:Ceramides; D008246:Lysophospholipids; D016328:NF-kappa B; C060506:sphingosine 1-phosphate; D013110:Sphingosine