Effects of mouse and human lipocalin homologues 24p3/lcn2 and neutrophil gelatinase-associated lipocalin on gastrointestinal mucosal integrity and repair.

Background & Aims: The lipocalin superfamily, including the mouse and human homologues 24p3/lcn2 and neutrophil gelatinase-associated lipocalin, show great functional diversity including roles in olfaction, transportation, and prostaglandin synthesis in mammals. Their potential role in maintaining gastrointestinal mucosal integrity and repair is, however, unclear.

Methods: Changes in 24p3/lcn2 expression in the mouse gut in response to various noxious agents were examined using Northern blot, in situ hybridization, and immunohistochemistry.

Tissue involution and the acute phase response.

After their roles in reproduction are completed, the mass of the uterus and the mammary gland decrease rapidly by the process of involution that involves an ordered series of events including apoptosis, neutrophil entry, the release of degradative enzymes, and phagocytosis of cellular debris. The acute phase proteins are produced by the liver and other tissues in response to inflammation or a toxic challenge. Uterocalin (SIP24/24p3) is one of these proteins.

High expression in involuting reproductive tissues of uterocalin/24p3, a lipocalin and acute phase protein.

During reproduction the mass and number of cells in the uterus and the mammary gland increase rapidly and then diminish more rapidly after their reproductive functions are completed. The diminishment of tissue mass, known as involution, involves an ordered series of events that includes apoptosis of resident cells, neutrophil invasion, the release of degradative enzymes and phagocytosis of cellular debris. Local signals are believed to regulate the progression of involution in each tissue.