O0028 NEONATAL MATERNAL SEPARATION INDUCES LONG-LASTING DISTAL COLONIC MUCOSAL BARRIER DYSFUNCTION AND ALTERED BACTERIAL-EPITHELIAL INTERACTIONS IN RAT PUPS

Abstract

Introduction: Our previous studies have shown that early life stress in the form of intermittent maternal separation (MS) predisposes adult rats to develop intestinal mucosal dysfunction, specifically defective barrier function, following exposure to a mild acute stressor. Despite such findings, the immediate consequences of early life stress in neonatal rat pups have not been examined. Methods: Sprague-Dawley (SD) rat pups were individually separated from their mother for 3h/day from 4–20 days of age, while control non-separated pups (NS) remained with their dam. Studies were conducted on days 19–20, 24–25 and 29–30 when blood was collected for corticosterone measurement, and colonic tissues were removed for functional and morphological assessment. Tissues were mounted on Ussing chambers where baseline ion transport (indicated by short circuit current, Isc), and macromolecular permeability (flux of horseradish peroxidase, HRP) were assessed. Electron microscopy (EM) photomicrographs were analyzed for epithelial abnormalities. Results: Intermittent separation caused stress as indicated by elevated corticosteroid levels in serum of MS pups compared to controls. There was a higher baseline value for Isc in the distal region of the colon compared to the proximal region in all pups. Ion secretion in the distal colon was stimulated significantly in MS pups compared to controls at 19–20 and 24–25, but not at 29–30 days of age. More dramatically macromolecular uptake was enhanced 3-fold in the distal colon of MS pups compared to NS controls at 19–20 days of age, with normalization occurring by 29–30 days of age. EM studies of this region showed bacteria adhering to and penetrating into the epithelium of the MS pups, while such organisms were absent in the NS group in all age groups. Conclusion: Early psychological trauma predisposes pre-weanling rat pups to develop mucosal barrier dysfunction which involves lack of protection from adhering/internalizing bacteria. This dysfunction persists long after weaning. We speculate that abnormal bacterial-epithelial interactions in early life may result in altered tolerance to commensal flora and may predispose affected individuals to develop microbial-induced inflammation in later life.