Aryl hydrocarbon receptor protects against bacterial infection by promoting macrophage survival and reactive oxygen species production.

Aryl hydrocarbon receptor (AhR) is crucial for various immune responses. The relationship between AhR and infection with the intracellular bacteria Listeria monocytogenes (LM) is poorly understood. Here, we show that in response to LM infection, AhR is required for bacterial clearance by promoting macrophage survival and reactive oxygen species (ROS) production. AhR-deficient mice were more susceptible to listeriosis, and AhR deficiency enhances bacterial growth in vivo and in vitro. On the other hand, pro-inflammatory cytokines were increased in AhR-deficient macrophages infected with LM despite enhanced susceptibility to LM infection in AhR-deficient mice. Subsequent studies demonstrate that AhR protects against macrophage cell death induced by LM infection through the induction of the antiapoptotic factor, the apoptosis inhibitor of macrophages, which promotes macrophage survival in the setting of LM infection. Furthermore, AhR promotes ROS production for bacterial clearance. Our results demonstrate that AhR is essential to the resistance against LM infection as it promotes macrophage survival and ROS production. This suggests that the activation of AhR by its ligands may be an effective strategy against listeriosis.