CD14- and Toll-like receptor-dependent activation of bladder epithelial cells by lipopolysaccharide and type 1 piliated Escherichia coli.
The gram-negative bacterium Escherichia coli is the leading cause of urinary tract infection. The interaction between type 1 piliated E. coli and bladder epithelial cells leads to the rapid production of inflammatory mediators, such as interleukin-6 (IL-6) and IL-8. Conflicting reports have been published in the literature regarding the mechanism by which uroepithelial cells are activated by type 1 piliated E. coli. In particular, the role of lipopolysaccharide (LPS) in these responses has been an area of significant debate. Much of the data arguing against LPS-mediated activation of bladder epithelial cells have come from studies using a renal epithelial cell line as an in vitro model of the urinary epithelium. In this report, we analyzed three bladder epithelial cell lines and demonstrated that they all respond to LPS. Furthermore, the LPS responsivity of the cell lines directly correlated with their ability to generate IL-6 after E. coli stimulation. The LPS receptor complex utilized by the bladder epithelial cell lines included CD14 and Toll-like receptors, and signaling involved the activation of NF-kappaB and p38 mitogen-activated protein kinase. Also, reverse transcription-PCR analysis demonstrated that bladder epithelial cells express CD14 mRNA. Thus, the molecular machinery utilized by bladder epithelial cells for the recognition of E. coli is very similar to that described for traditional innate immune cells, such as macrophages. In contrast, the A498 renal epithelial cell line did not express CD14, was hyporesponsive to LPS stimulation, and demonstrated poor IL-6 responses to E. coli.
Schilling
Joel D
JD
Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, Missouri 63110-1093, USA.
Martin
Steven M
SM
Hunstad
David A
DA
Patel
Kunal P
KP
Mulvey
Matthew A
MA
Justice
Sheryl S
SS
Lorenz
Robin G
RG
Hultgren
Scott J
SJ
D029721:Drosophila Proteins; D004847:Epithelial Cells / Q000187:drug effects; D004926:Escherichia coli / Q000472:pathogenicity*; D010861:Fimbriae, Bacterial / Q000502:physiology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis; D018950:Lipopolysaccharide Receptors / Q000502:physiology*; D008070:Lipopolysaccharides / Q000633:toxicity*; D008562:Membrane Glycoproteins / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D016328:NF-kappa B / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D051193:Toll-Like Receptors; D014407:Tumor Cells, Cultured; D001743:Urinary Bladder / Q000166:cytology* / Q000187:drug effects / Q000382:microbiology; D048051:p38 Mitogen-Activated Protein Kinases
D029721:Drosophila Proteins; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D011956:Receptors, Cell Surface; D051193:Toll-Like Receptors; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases