Apolipoprotein E3 and E4 isoforms exhibit differing effects in countering endotoxins

Area of Science:

• Biochemistry
• Immunology
• Molecular Biology

Background:

• Apolipoprotein E (APOE) is vital for lipid metabolism.
• Emerging evidence suggests APOE's role in host defense against bacterial infections.

Purpose of the Study:

• To investigate the antibacterial properties of APOE3 and APOE4 isoforms.
• To explore the interaction between APOE isoforms and bacterial lipopolysaccharides (LPS).

Main Methods:

• Antibacterial assays with Pseudomonas aeruginosa and Escherichia coli.
• Gel shift assays, CD, and fluorescence spectroscopy to study APOE-LPS interaction.
• Molecular dynamics simulations, amyloid staining, fluorescence and electron microscopy.

Main Results:

• APOE isoforms bind to LPS, with APOE4 showing higher affinity than APOE3.
• LPS induces APOE isoform aggregation, which neutralizes LPS and reduces inflammation in vivo.
• Both APOE3 and APOE4 inhibited the growth of P. aeruginosa and E. coli.

Conclusions:

• APOE isoforms possess antibacterial activity by binding and neutralizing LPS.
• APOE aggregation is a key mechanism for LPS neutralization and anti-inflammatory effects.
• These findings underscore APOE's significant role in innate immunity and host defense.