Effects of prenatal lipopolysaccharide exposure on epithelial development and function in newborn rat intestine.

Background: Maternal infection during pregnancy is associated with several neonatal morbidities, including periventricular leukomalacia and lung maldevelopment and injury.

Objective: To test the hypothesis that responses to prenatal maternal exposure to lipopolysaccharide (LPS) alter intestinal epithelial development and function in newborn rats.

Design/methods: Timed-pregnancy female Sprague-Dawley rats were administered either 2 mg LPS or an equal volume of isotonic saline by intraperitoneal injection at E16 and allowed to deliver naturally. Pups were weighed and then killed at days of life (DOL) 0, 3, 7 and 14. Morphometric parameters were measured on standard hematoxylin and eosin-stained sections using ImagePro software. Immunohistochemistry was performed with antibody specific for inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine on distal ileal intestinal samples analyzed at each time point. Optical density was determined and quantified for site-specific regions of intestinal sections. On DOL 14, in vivo mucosal permeability was measured by feeding rats fluorescein isothiocyanate (FITC) via orogastric tube; and then serum FITC was measured.

Results: There were no significant differences in pup weights. Mucosal thicknesses were significantly less in the distal ileum from pups born to LPS-exposed dams on DOL 0, 3 and 7 (P < 0.001). On DOL 0, iNOS protein concentrations in the prenatal LPS treatment group were significantly greater than iNOS protein concentrations in the distal villus (P < 0.001), proximal villus/crypts (P < 0.01), submucosa (P < 0.001) and muscularis (P < 0.01) in the distal small intestine of the control group. On DOL 3, 7 and 14, significant differences were observed in iNOS protein concentrations in the distal villus and submucosal regions between groups (P < 0.001). On DOL 0, 3, 7 and 14, 3-nitrotyrosine immunostaining was significantly elevated in the prenatal LPS-exposed pups in the distal villus on (P < 0.001) as well as in the submucosa on DOL 3 (P < 0.001). Serum FITC measurement was significantly greater in prenatal LPS exposure group at DOL 14 (P < 0.001).

Conclusions: Maternal exposure to LPS during pregnancy alters intestinal growth and regulation of iNOS in the newborn rat intestine.