Escherichia coli-induced productions of pro-inflammatory cytokines are regulated by MAP kinases and G-protein but not by Akt: Relationship with phylogenetic groups and resistance patterns

Introduction

We investigated the role of PI3-K, MAP kinases, and heterotrimeric G proteins in inducing cytokines production in human whole blood cultures stimulated by viable Escherichia coli (E. coli) clinical strains.

Materials and methods

We used eight E. coli strains that belong to different phylogenetic groups and presented by different antibiotic resistance patterns. Whole blood from healthy volunteers was incubated at 37 °C for 150 min, with lipopolysaccharide (LPS) from E. coli O111:B4 or selected viable E. coli clinical strains, with or without SB202190 (p38 inhibitor), PD98059 (ERK inhibitor), PTX (pertussis toxin; heterotrimeric G proteins inhibitor), wortmaninn (PI3-K inhibitor). The TNF-α, IL-1β, IL-10 and IFN-γ concentrations were measured in culture supernatants (ELISA).

Results

IL-10 and IFN-γ were not detectable. Susceptible strains induced higher TNF-α and IL-1β productions than β-lactam resistant strains (p < 0.05), with no difference between phylogenetic groups. A transformed strain carrying a plasmid-mediated AmpC-β-lactamase gene (CMY-2) induced lower TNF-α and IL-1β production than the parent wild type strain (p < 0.05). SB202190 (p38 inhibitor) and PD98059 (ERK inhibitor) reduced TNF-α concentrations by, respectively, 80% (p < 0.05) and 50% (p < 0.05). Wortmaninn (PI3-K inhibitor) had no significant effect. PTX (heterotrimeric G proteins inhibitor) altered TNF-α production after viable bacteria stimulation (1.7-fold increase; p < 0.05) but not after LPS (TLR-4) stimulation. Regarding IL-1β, wortmaninn, SB202190 and PTX had no significant effect whereas PD98059 significantly decreased production in whole cell cultures (p < 0.05).

Conclusion

Susceptible strains induce greater TNF-α and IL-1β productions than resistant strains. ERK kinase plays a major role in viable E. coli strains inducing TNF-α and IL-1β production. E. coli exerts an effect on the pertussis toxin-sensitive G-protein through a TLR-4-independent mechanism.