Effects of Listeria monocytogenes and Yersinia enterocolitica on cytokine gene expression and release from human polymorphonuclear granulocytes and epithelial (HEp-2) cells

Abstract

The gene expression and cytokine release of the proinflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) after infection of human epithelial cells (HEp-2 cells) and polymorphonuclear granulocytes (PMNs) were investigated by using isogenic pairs of Listeria monocytogenes and Yersinia enterocolitica strains. By polymerase chain reaction-assisted mRNA amplification and RNA dot blot analysis, we showed that PMNs and HEp-2 cells expressed enhanced levels of mRNA encoding IL-1β, IL-6, and TNF-α after bacterial infection. Concomitant with the enhanced mRNA level, an increased secretion rate of IL-1β, IL-6, and TNF-α from PMNs as assessed by enzyme-linked immunosorbent assay was observed. HEp-2 cells after infection also released IL-6 and TNF-α into the cell supernatant, while no IL-1β release was detected. Cellular coincubation experiments were carried out with Transwell chambers. Our studies revealed that the coculture of PMNs and HEp-2 cells led to an increased IL-1β and IL-6 release. In contrast, after infection with the invasive bacteria, reduced levels of TNF- α were measured. Our data show that PMNs secrete the proinflammatory cytokines IL-1β, IL-6, and TNF-α within some hours after infection with L. monocytogenes and Y. enterocolitica and that cellular interactions with epithelial cells alone via soluble mediators influence the net amount of released proinflammatory cytokines.