We have studied the effect of human bacterial pathogen Neisseria gonorrhoeae (Ngo) on the activation of nuclear factor (
NF)-kappaB and the transcriptional activation of inflammatory
cytokine genes upon
infection of epithelial cells. During the course of
infection, Ngo, the etiologic agent of
gonorrhea, adheres to and penetrates mucosal epithelial cells. In vivo, localized gonococcal
infections are often associated with a massive inflammatory response. We observed upregulation of several inflammatory
cytokine messenger RNAs (mRNAs) and the release of the
proteins in Ngo-infected epithelial cells. Moreover,
infection with Ngo induced the formation of a
NF-kappaB DNA-
protein complex and, with a delay in time, the activation of
activator protein 1, whereas
basic leucine zipper transcription factors binding to the cAMP-responsive
element or
CAAT/enhancer-binding protein DNA-binding sites were not activated. In supershift assays using
NF-kappaB-specific
antibodies, we identified a
NF-kappaB p50/p65 heterodimer. The
NF-kappaB complex was formed within 10 min after
infection and decreased 90 min after
infection. Synthesis of
tumor necrosis factor alpha and interluekin (IL)-1beta occurred at later times and therefore did not account for
NF-kappaB activation. An analysis of transiently transfected
IL-6 promoter deletion constructs suggests that
NF-kappaB plays a crucial role for the transcriptional activation of the
IL-6 promoter upon Ngo
infection. Inactivation of
NF-kappaB conferred by the
protease inhibitor N-tosyl--
phenylalanine chloromethyl
ketone inhibited
mRNA upregulation of most, but not all, studied cyctokine genes. Activation of
NF-kappaB and
cytokine mRNA upregulation also occur in Ngo-infected epithelial cells that were treated with
cytochalasin D, indicating an extracellular signaling induced before invasion.