Inflammatory neutrophils secrete annexin 1 during experimentally induced colitis in rats

Immunoblotting and immunohistochemical analysis were performed to identify the cells expressing and secreting annexin 1 during experimental rat coliti s induced by trinitrobenzene sulfonic acid. Annexin 1 expression was increa sed during the inflammation. Likewise, annexin 1 secretion was induced in i nflamed colons at one, three, six, and nine days after trinitrobenzene sulf onic acid treatment but was not detected in colons from controls and rats s t 12 days. Immunohistochemistry showed that the rise in annexin 1 expressio n resulted from the infiltration of two types of leukocytes highly positive for annexin 1: neutrophils (the most abundant) and macrophages. At day 1 a fter treatment, neutrophils of the inflammatory site, in mucosa and submuco sa, are the only cells expressing annexin 1, Immunoblotting showed that the y secreted annexin 1 whereas neutrophils from blood or tunica muscularis di d not, This indicates that, during this colitis, annexin 1 can be secreted by neutrophils located in the inflammatory site.