Induction of NF-kappaB nuclear translocation in human respiratory epithelial cells by group A streptococci

The activation of the transcription factor NF-kappaB and the production of inflammatory mediators play an essential role in the host response to pathogenic organisms. The objective of this study was to investigate the ability of group A streptococci (GAS) to stimulate the nuclear translocation of NF-kappaB in cultured human epithelial (HEp-2) cells. Infection of HEp-2 cells with a strain of Streptococcus pyogenes capable to efficiently internalize HEp-2 cells (strain A40) resulted in translocation of NF-kappaB during the first 15 min of infection, reaching a peak after 30 min that persisted at slightly lower levels 1h thereafter. Inhibition of bacterial internalization by cytochalasin D resulted in lower levels of nuclear NF-kappaB at 30 min and 1h of infection, however, it did not affect the initial nuclear translocation of NF-kappaB observed at 15 min postinfection. These results suggest that adhesion of S. pyogenes alone might be sufficient to stimulate nuclear translocation of NF-kappaB, however, bacterial internalization is required for a sustained nuclear translocation of this transcriptional factor.