Annexin 1 is Overexpressed and Specifically Secreted During Experimentally Induced Colitis in Rats

Annexin 1 is a protein induced by glucocorticoids endowed with extracellular anti-inflammatory properties. In this study, the local expression and secretion of annexins 1–6, in rat proximal colon, were studied at different times after intracolonic administration of 30 mg trinltrobenzenesulfonic acid in 50% ethanol. Secretion was identified by incubating colonic tissues in a culture medium. The expression of annexins was detected by immunoblotting in tissue homogenates and incubation media. Inflammatory stages were evaluated by measuring myeloperoxidase activity. Annexin 1 expression in colons increased after trinitrobenzenesulfonic acid treatment and was maximal between days 1 to 9, during the cellular stage of the inflammation that corresponded to maximal myeloperoxidase activity. From 12 h to 9 days after trinitrobenzenesulfonic acid/ethanol treatment, annexin 1 was specifically secreted. Annexin 3 was also overexpressed during the cellular stage, but the expression of annexins 2, 4, 5, and 6 was unchanged; none of these annexins were secreted. Annexin 1 was shown to be physiologically secreted because its release was specific, abundant, and not correlated with cellular lysis. Annexin 1 may be considered as a putative candidate in the control of the gut inflammatory processes.