Presence of secretory leukocyte protease inhibitor in human endometrium and first trimester decidua suggests an antibacterial protective role

Secretory leukocyte protease inhibitor (SLPI) is a neutrophil elastase inhi bitor which also has antibacterial and anti-inflammatory properties. It is found associated with mucosal membranes. Although SLPI has been reported in the cervix it has not thus far been reported in human endometrium. This st udy investigates the presence of SLPI in endometrium, first trimester decid ua and trophoblast. Cultured first trimester decidua was found to produce 4 .7 +/- 2.0 ng/mg/24 h of SLPI. Endometrium and trophoblast were both found to secrete significantly lower amounts of SLPI (P < 0.01) although endometr ial expression was menstrual cycle dependent with increased secretion in th e secretory phase. Although relatively low concentrations of SLPI were rele ased from the endometrium during culture, most of the SLPI remained associa ted with the tissue and could be recovered with mild acid extraction. This is in agreement with the high isoelectric point (pI) for SLPI, associated w ith high solubility at low pH. The main site of SLPI synthesis in endometri um and decidua was found to be the glandular epithelium. An antibiotic role for SLPI in the endometrium and decidua during implantation and pregnancy would be consistent with the expression profile and localization of SLPI.