title: Interleukin-8 secretion of cortical tubular epithelial cells is directed to the basolateral environment and is not enhanced by apical exposure to Escherichia coli.
abstract: In upper urinary tract infections, tubular epithelial cells (TEC) may play a pivotal role in the initiation of the renal inflammatory response. They exert crucial immunological functions such as processing and presentation of foreign antigen, secretion of proinflammatory cytokines (interleukin-6 [IL-6] and tumor necrosis factor alpha) and chemokines (IL-8, MCP-1, ENA-78, and RANTES). Since monolayer cultures are a limited model for polarized tubular epithelial cells, we studied the side-dependent IL-8 secretion of TEC by using cell culture inserts as a basement membrane imitation. Primary cultures of proximal TEC were stimulated with differently fimbriated mutants of Escherichia coli, E. coli LPS, S-fimbria isolates, and IL-1alpha. IL-8 protein was measured by enzyme-linked immunosorbent assay, and IL-8-like biological activity was tested by measuring elastase release from polymorphonuclear cells in supernatants of the upper and lower compartments. IL-8 mRNA was compared by competitive PCR. IL-8 secretion by TEC into the basolateral environment was significantly higher than secretion into the apical compartment, representing the tubular lumen. However, stimulation of IL-8 secretion by TEC was restricted to IL-1alpha and was not inducible by E. coli mutants, S fimbriae, or lipopolysaccharide. With this in vitro model of polarized TEC, we show that luminal contact of TEC with uropathogenic E. coli does not result in enhanced IL-8 secretion. The basolaterally directed production of the neutrophil chemotactic factor IL-8 by TEC after stimulation with IL-1alpha might play an important role in the initiation of inflammatory cell influx into the renal parenchyma.
authors.affiliation: Department of Internal Medicine I, Medical University of Lübeck, D-23538 Lübeck, Germany. sskrueger@aol.com
authors.forename: S
authors.initials: S
authors.lastname: Krüger
authors.forename: E
authors.initials: E
authors.lastname: Brandt
authors.forename: M
authors.initials: M
authors.lastname: Klinger
authors.forename: B
authors.initials: B
authors.lastname: Kreft
mesh_terms: D001483:Base Sequence; D016764:Cell Polarity; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000276:immunology; D010861:Fimbriae, Bacterial / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D007375:Interleukin-1 / Q000494:pharmacology; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D007672:Kidney Cortex / Q000276:immunology / Q000382:microbiology / Q000648:ultrastructure; D007684:Kidney Tubules / Q000276:immunology* / Q000382:microbiology / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000633:toxicity; D008854:Microscopy, Electron; D009154:Mutation; D011704:Pyelonephritis / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D017931:DNA Primers; D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D012333:RNA, Messenger