Amyloid precursor protein expression modulates intestine immune phenotype.

Area of Science:

• Immunology
• Neuroscience
• Gastroenterology

Background:

• Amyloid precursor protein (APP) metabolism is well-studied in neurons, but its role in other cell types, like macrophages, is less understood.
• Prior research indicates APP influences monocytic cell activation, prompting investigation into its effects on macrophages in non-neuronal tissues.

Purpose of the Study:

• To investigate the role of Amyloid precursor protein (APP) in regulating macrophage activation phenotype within the small intestine.
• To determine if APP influences intestinal function, including absorption and motility.

Main Methods:

• Comparison of ileums from wild type and APP knockout (APP(-/-)) mice.
• Immunohistochemical analysis for markers like CD68, cyclooxygenase-2 (COX-2), CD40, CD11c, and βIII-tubulin.
• In vitro assessment of peritoneal macrophage migration and cytokine secretion (KC).

Main Results:

• APP(-/-) mice showed reduced CD68 immunoreactivity and lower levels of COX-2, CD68, CD40, CD11c, and βIII-tubulin in ileums.
• APP(-/-) macrophages exhibited decreased migratory ability and lower basal KC cytokine secretion in vitro.
• APP(-/-) ileums displayed altered cytokine profiles and impaired absorption with increased motility.

Conclusions:

• APP expression is critical for regulating immune cell phenotype, cytokine secretion, and intestinal function.
• These findings reveal a novel function for APP in the gut immune system, with implications for both Alzheimer's disease and immune-related disorders.