Listeria monocytogenes infection of Caco-2 human epithelial cells induces activation of transcription factor NF-kappa B/Rel-like DNA binding activities.

The effect of Listeria monocytogenes infection on the cellular level of transcription factor NF-kappa B in the human epithelia-like cell line Caco-2 was investigated. Infection with L. monocytogenes or treatment with lipoteichoic acid induced the formation of three NF-kappa B-like DNA-protein complexes C1, C2, and C3, which were identified as containing either, RelA and p50, RelB and p50, or p50, respectively. NF-kappa B activation in L. monocytogenes-infected Caco-2 cells was distinct from NF-kappa B activation in infected P388D1 macrophages concerning the NF-kappa B complexes formed and the kinetics of the induction.

Listeria monocytogenes infection of P388D1 macrophages results in a biphasic NF-kappaB (RelA/p50) activation induced by lipoteichoic acid and bacterial phospholipases and mediated by IkappaBalpha and IkappaBbeta degradation.

As previously reported, Listeria monocytogenes infection of P388D1 macrophages results in a rapid induction of NF-kappaB DNA-binding activity. Here we show that this induction of NF-kappaB activity occurs in a biphasic mode: first, a transient, IkappaBalpha degradation-dependent phase of activity, also induced by the nonvirulent species Listeria innocua, which is mediated by binding of the bacteria to the macrophage, or by adding Listeria-derived lipoteichoic acid to the macrophage; the second persistent phase of activation is only markedly induced when the bacteria enter the cytoplasm of the host cell and express the virulence genes plcA and plcB, encoding two phospholipases. We suggest that products of the enzymatic activity of phospholipases directly interfere with host cell signal transduction pathways, thus leading to persistent NF-kappaB activation via persistent IkappaBbeta degradation.

Listeria monocytogenes infection enhances transcription factor NF-kappa B in P388D1 macrophage-like cells.

In the present study, we investigated the effect of Listeria monocytogenes infection on the cellular level of the transcription factors NF-kappa B, AP-1, and NF-IL6 in the macrophage-like cell line P388D1 by using electrophoretic mobility shift assays. Infection with L. monocytogenes enhanced the formation of two NF-kappa B-like DNA-protein complexes, C1 and C2, whereas the concentration of AP-1 and NF-IL6 complexes remained unaffected. In supershift assays using NF-kappa B-specific antibodies, complex C2 was identified to be a p50 homodimer (KBF1) and complex C1 was identified as a p50/p65 heterodimer. Both complexes were formed within 10 min after addition of the bacteria. Since the synthesis of tumor necrosis factor alpha and interleukin-1 occurs at later times, these cytokines cannot be the mediators of enhanced NF-kappa B formation. Infection experiments with different nonhemolytic mutants of L. monocytogenes and the use of the phagocytosis inhibitor cytochalasin B suggest that events prior to invasion and escape of the bacteria from the phagosome into the cytoplasm enhance the nuclear transport of p50/p65 NF-kappa B components.