Enhanced LPS-induced peritonitis in mice deficiency of cullin 4B in macrophages

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Cullin 4B (CUL4B) is a scaffold protein in the CUL4B-RING-E3 ligase complex, involved in ubiquitinating intracellular proteins.
• CUL4B targets include cell cycle and DNA replication proteins, suggesting a role in cellular processes beyond protein degradation.

Purpose of the Study:

• To investigate the role of myeloid-specific Cullin 4B (CUL4B) deficiency in innate immunity.
• To determine the impact of CUL4B deficiency on macrophage function and response to lipopolysaccharide (LPS).

Main Methods:

• Generation of myeloid-specific Cul4b-deficient mice (Cul4b(f/y);LysM-Cre(KI/KI)).
• Intraperitoneal injection of lipopolysaccharide (LPS) to induce peritonitis.
• Analysis of body weight, leukocyte infiltrates, chemokines, and cytokines (IL-6, TNF-α) in peritoneal lavage fluid.
• Assessment of bone marrow-derived macrophages (BMDMs) for proliferation, chemokine, and cytokine production upon LPS stimulation.

Main Results:

• Cul4b-deficient mice exhibited decreased body weight and increased leukocyte infiltrates and chemokines post-LPS injection.
• Pro-inflammatory cytokines (IL-6, TNF-α) did not increase in Cul4b-deficient mice after LPS.
• Cul4b-deficient macrophages showed enhanced proliferation, increased chemokine secretion, and decreased TNF-α and IL-6 production upon LPS stimulation.
• Myeloid-specific Cul4b deficiency exacerbated LPS-induced peritonitis.

Conclusions:

• Myeloid-specific Cul4b deficiency impairs the innate immune response to LPS, worsening peritonitis.
• CUL4B deficiency in macrophages leads to enhanced proliferation and chemokine production, but suppressed pro-inflammatory cytokine release.
• This study reveals a novel role for CUL4B in regulating macrophage function and innate immunity.