BETA-AMYLOID PRECURSOR PROTEIN (BETA-APP) IN HUMAN GUT WITH SPECIAL REFERENCE TO THE ENTERIC NERVOUS-SYSTEM

The distribution of the beta-amyloid precursor protein (beta APP) in t he human gastrointestinal tract, from esophagus trough rectum, was stu died using immunoblotting, as well as combined immunohistochemical and image analysis (optic microdensitometry) techniques. The study was fo cused on the enteric nervous system, beta APP was detected by means of a monoclonal antibody (22C11), which recognizes all beta APP isoforms as well as beta APP-like proteins. Immunoblotting revealed two main p rotein bands, one corresponding to full-length beta APPs (estimated mo lecular masses of similar to 97-115 kDa); the other corresponded to a protein with estimated molecular masses of 55 kDa, Specific beta APP i mmunoreactivity (IR) was found in the submucous and myenteric plexuses localized in the supporting glial cells rather than in neurons. Diffe rences were encountered neither in the localization nor in the intensi ty of immunostaining among different segments of the gastrointestinal tract. Moreover, no age-dependent changes were found, beta APP IR was also regularly observed in blood vessels, primarily labelling endothel ial cells. Our results provide evidence for the occurrence of beta APP in human gastrointestinal tract of healthy people in both neuronal an d nonneuronal tissues. Whether or not these findings have functional o r clinical relevance remains to be clarified in future studies.