Protein Kinase Cϵ Is Required for Macrophage Activation and Defense Against Bacterial Infection

To assess directly the role of protein kinase C (PKC)ϵ in the immune system, we generated mice that carried a homozygous disruption of the PKCϵ locus. PKCϵ^−/− animals appeared normal and were generally healthy, although female mice frequently developed a bacterial infection of the uterus. Macrophages from PKCϵ^−/− animals demonstrated a severely attenuated response to lipopolysaccharide (LPS) and interferon (IFN)γ, characterized by a dramatic reduction in the generation of NO, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β. Further analysis revealed that LPS-stimulated macrophages from PKCϵ^−/− mice were deficient in the induction of nitric oxide synthase (NOS)-2, demonstrating a decrease in the activation of IκB kinase, a reduction in IκB degradation, and a decrease in nuclear factor (NF)κB nuclear translocation. After intravenous administration of Gram-negative or Gram-positive bacteria, PKCϵ^−/− mice demonstrated a significantly decreased period of survival. This study provides direct evidence that PKCϵ is critically involved at an early stage of LPS-mediated signaling in activated macrophages. Furthermore, we demonstrate that in the absence of PKCϵ, host defense against bacterial infection is severely compromised, resulting in an increased incidence of mortality.