title: Recognition of intestinal epithelial HIF-1alpha activation by Pseudomonas aeruginosa.
abstract: Human intestinal epithelial cell monolayers (Caco-2) subjected to hypoxia and reoxygenation release soluble factors into the apical medium that activate the virulence of the opportunistic pathogen Pseudomonas aeruginosa to express the potent barrier-dysregulating protein PA-I lectin/adhesin. In this study, we defined the role of hypoxia-inducible factor (HIF)-1alpha in this response. We tested the ability of medium from Caco-2 cells with forced expression of HIF-1alpha to increase PA-I expression in P. aeruginosa and found that medium from Caco-2 cells overexpressing HIF-1alpha increased PA-I expression compared with medium from control cells (P < 0.001, ANOVA). To identify the components responsible for this response, medium was fractionated by molecular weight and subjected to mass spectroscopy, which identified adenosine as the possible mediator. Both adenosine and its immediate downstream metabolite inosine induced PA-I expression in P. aeruginosa in a dose-dependent fashion. Because inosine was not detectable in the medium of Caco-2 cells exposed to hypoxia or overexpressing HIF-1alpha, we hypothesized that P. aeruginosa itself might metabolize adenosine to inosine. Using mutant and parental strains of P. aeruginosa, we demonstrated that P. aeruginosa metabolized adenosine to inosine via adenosine deaminase and that the conditioned medium enhanced the extracellular accumulation of inosine. Together, these results provide evidence that P. aeruginosa can recognize and respond to extracellular end products of intestinal hypoxia that are released after activation of HIF-1alpha. The ability of P. aeruginosa to metabolize adenosine to inosine may represent a subversive microbial virulence strategy that deprives the epithelium of the cytoprotective actions of adenosine.
authors.affiliation: Department of Surgery, University of Chicago, Chicago, Illinois, USA.
authors.forename: Nachiket J
authors.initials: NJ
authors.lastname: Patel
authors.forename: Olga
authors.initials: O
authors.lastname: Zaborina
authors.forename: Licheng
authors.initials: L
authors.lastname: Wu
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Wang
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Wolfgeher
authors.forename: Vesta
authors.initials: V
authors.lastname: Valuckaite
authors.forename: Mae J
authors.initials: MJ
authors.lastname: Ciancio
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Kohler
authors.forename: Olga
authors.initials: O
authors.lastname: Shevchenko
authors.forename: Sean P
authors.initials: SP
authors.lastname: Colgan
authors.forename: Eugene B
authors.initials: EB
authors.lastname: Chang
authors.forename: Jerrold R
authors.initials: JR
authors.lastname: Turner
authors.forename: John C
authors.initials: JC
authors.lastname: Alverdy
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D018938:Caco-2 Cells; D015687:Cell Hypoxia; D017930:Genes, Reporter; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000502:physiology*; D007288:Inosine / Q000378:metabolism; D007413:Intestinal Mucosa / Q000382:microbiology / Q000502:physiology*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics*; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D017395:Plasminogen Activator Inhibitor 1; D011994:Recombinant Proteins; C051321:SERPINE1 protein, human; D007288:Inosine; D000241:Adenosine