Inflammatory Neutrophils Secrete Annexin 1 During Experimentally Induced Colitis in Rats

Immunoblotting and immunohistochemical analysiswere performed to identify the cells expressing andsecreting annexin 1 during experimental rat colitisinduced by trinitrobenzene sulfonic acid. Annexin 1 expression was increased during theinflammation. Likewise, annexin 1 secretion was inducedin inflamed colons at one, three, six, and nine daysafter trinitrobenzene sulfonic acid treatment but wasnot detected in colons from controls and rats at 12days. Immunohistochemistry showed that the rise inannexin 1 expression resulted from the infiltration oftwo types of leukocytes highly positive for annexin 1: neutrophils (the most abundant) andmacrophages. At day 1 after treatment, neutrophils ofthe inflammatory site, in mucosa and submucosa, are theonly cells expressing annexin 1. Immunoblotting showed that they secreted annexin 1 whereasneutrophils from blood or tunica muscularis did not.This indicates that, during this colitis, annexin 1 canbe secreted by neutrophils located in the inflammatorysite.