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Protein kinase Cepsilon is required for macrophage activation and defense against bacterial infection
A Castrillo1, D J Pennington, F Otto
1Instituto de Bioquímica (Centro Mixto Consejo Superior de Investigaciones Cientificas-UCM), Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain.
Abstract:
To assess directly the role of protein kinase C (PKC)epsilon in the immune system, we generated mice that carried a homozygous disruption of the PKCepsilon locus. PKCepsilon(-/-) animals appeared normal and were generally healthy, although female mice frequently developed a bacterial infection of the uterus. Macrophages from PKCepsilon(-/-) animals demonstrated a severely attenuated response to lipopolysaccharide (LPS) and interferon (IFN)gamma, characterized by a dramatic reduction in the generation of NO, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-1beta. Further analysis revealed that LPS-stimulated macrophages from PKCepsilon(-/-) mice were deficient in the induction of nitric oxide synthase (NOS)-2, demonstrating a decrease in the activation of IkappaB kinase, a reduction in IkappaB degradation, and a decrease in nuclear factor (NF)kappaB nuclear translocation. After intravenous administration of Gram-negative or Gram-positive bacteria, PKCepsilon(-/-) mice demonstrated a significantly decreased period of survival. This study provides direct evidence that PKCepsilon is critically involved at an early stage of LPS-mediated signaling in activated macrophages. Furthermore, we demonstrate that in the absence of PKCepsilon, host defense against bacterial infection is severely compromised, resulting in an increased incidence of mortality.
Insights
Protein kinase C (PKC)epsilon is crucial for immune responses. Mice lacking PKCepsilon show impaired responses to bacterial infections and reduced survival rates, highlighting its role in host defense.
Area of Science:
- Immunology
- Cellular Signaling
- Molecular Biology
Background:
- Protein kinase C (PKC)epsilon is a signaling molecule.
- Its specific role in the immune system requires direct investigation.
Purpose of the Study:
- To elucidate the function of PKCepsilon in immune responses.
- To determine the impact of PKCepsilon deficiency on host defense against bacterial infections.
Main Methods:
- Generation of PKCepsilon knockout (PKCepsilon(-/-)) mice.
- Assessment of macrophage responses to lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma).
- Evaluation of survival rates following bacterial challenge.
Main Results:
- PKCepsilon(-/-) mice exhibited impaired macrophage responses to LPS and IFN-gamma, with reduced production of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1beta (IL-1beta).
- LPS-stimulated macrophages from PKCepsilon(-/-) mice showed defective induction of nitric oxide synthase-2 (NOS-2), decreased IkappaB kinase activation, reduced IkappaB degradation, and diminished nuclear factor-kappaB (NF-kappaB) nuclear translocation.
- PKCepsilon(-/-) mice displayed significantly reduced survival rates after intravenous administration of Gram-negative or Gram-positive bacteria.
Conclusions:
- PKCepsilon plays a critical role in early lipopolysaccharide (LPS)-mediated signaling in activated macrophages.
- The absence of PKCepsilon severely compromises host defense against bacterial infections, leading to increased mortality.