Expression of bactericidal/permeability-increasing protein requires C/EBP epsilon

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Bactericidal/permeability-increasing protein (BPI) is a key component of neutrophil antimicrobial defense against Gram-negative bacteria.
• The regulation of BPI gene expression is critical for effective innate immunity.

Purpose of the Study:

• To investigate the role of the myeloid-specific transcription factor CCAAT/enhancer binding protein epsilon (C/EBP epsilon) in regulating BPI gene expression.
• To elucidate the molecular mechanisms by which C/EBP epsilon controls BPI production.

Main Methods:

• Analysis of BPI and C/EBP epsilon expression in a patient with C/EBP epsilon deficiency.
• Treatment of myeloid cell lines (U937, NB4) with all-trans retinoic acid (ATRA) to induce differentiation and assess BPI/C/EBP epsilon levels.
• Chromatin-immunoprecipitation (ChIP) and electrophoretic mobility shift assays (EMSAs) to determine C/EBP epsilon binding to the BPI promoter.
• Gene expression studies in C/EBP epsilon-deficient mice and human cord blood cells.

Main Results:

• A patient with a C/EBP epsilon mutation exhibited severely reduced BPI mRNA and protein.
• ATRA treatment increased BPI protein and C/EBP epsilon expression in myeloid cell lines.
• C/EBP epsilon directly binds to the C/EBP-binding site in the BPI gene promoter.
• Overexpression of C/EBP epsilon significantly upregulated BPI mRNA levels.
• BPI mRNA expression was markedly reduced in C/EBP epsilon-deficient mouse bone marrow.

Conclusions:

• C/EBP epsilon is essential for mediating BPI gene expression in myeloid cells.
• These findings establish C/EBP epsilon as a critical regulator of BPI, impacting innate immune responses.
• The study provides in vitro and in vivo evidence for the regulatory role of C/EBP epsilon in BPI production.