Secretion of cytokines by uroepithelial cells stimulated by Escherichia coli and Citrobacter spp.

Urinary tract epithelial cells (T 24/83) are able to express interleukin (IL)-6, IL-8, platelet-derived growth factor (PDGF) and tumour necrosis factor-alpha, but not IL-1 beta, IL-2, IL-4 and IL-10 in response to an infection with uropathogenic bacteria. The process of cytokine secretion is time dependent, with a significant increase in the cytokine activity after 60 min. The expression of virulence factors of the bacteria does not seem to play a role. The interaction between bacterial products (e.g. lipopolysaccharide) and/or bacterial adhesion mediated by adhesins and specific receptor molecules of cell surfaces may be responsible for the activity of mediator protein expression in the epithelial cells. The release of PDGF and IL-8 was found to be higher when due to Escherichia coli HB 101 (rough form) than that caused by other bacterial strains. Citrobacter CB 3009 provoked the highest level of IL-6. The PDGF level correlated significantly with IL-6 and IL-8 values (P<0.001). There was a significant correlation between the time-dependent release of IL-6 and IL-8 (P<0.05). In epithelial cytokine response to bacterial infection, the reaction of the epithelial cells may modify themselves (e.g. internalization of bacteria) and the immuno-regulatory processes that are caused by infection and responsible for parenchymal injury.