Changes in Intestinal Glucocorticoid Sensitivity in Early Life Shape the Risk of Epithelial Barrier Defect in Maternal-Deprived Rats

Abstract

Glucocorticoids (GC) contribute to human intestine ontogeny and accelerate gut barrier development in preparation to birth. Rat gut is immature at birth, and high intestinal GC sensitivity during the first two weeks of life resembles that of premature infants. This makes suckling rats a model to investigate postpartum impact of maternal separation (MS)-associated GC release in preterm babies, and whether GC sensitivity may shape MS effects in immature gut. A 4 hours-MS applied once at postnatal day (PND)10 enhanced plasma corticosterone in male and female pups, increased by two times the total in vivo intestinal permeability (IP) to oral FITC-Dextran 4 kDa (FD4) immediately after the end of MS, and induced bacterial translocation (BT) to liver and spleen. Ussing chamber experiments demonstrated a 2-fold increase of permeability to FD4 in the colon immediately after the end of MS, but not in the ileum. Colonic permeability was not only increased for FD4 but also to intact horseradish peroxidase 44 kDa in MS pups. In vivo, the glucocorticoid receptor (GR) antagonist RU486 or ML7 blockade of myosin light chain kinase controlling epithelial cytoskeleton contraction prevented MS-induced IP increase to oral FD4 and BT. In addition, the GR agonist dexamethasone dose-dependently mimicked MS-increase of IP to oral FD4. In contrast, MS effects on IP to oral FD4 and BT were absent at PND20, a model for full-term infant, characterized by a marked drop of IP to FD4 in response to dexamethasone, and decreased GR expression in the colon only compared to PND10 pups. These results show that high intestinal GC responsiveness in a rat model of prematurity defines a vulnerable window for a post-delivery MS, evoking immediate disruption of epithelial integrity in the large intestine, and increasing susceptibility to macromolecule passage and bacteremia.

Chronic Early-life Stress in Rat Pups Alters Basal Corticosterone, Intestinal Permeability, and Fecal Microbiota at Weaning: Influence of Sex

“…Other studies performed in male rats indicate an alteration of the intestinal barrier at weaning in the maternal separation model 23 that was detected by the significant increase of colonic short-circuit current and horseradish peroxidase flux along with increased intestinal permeability that was still maintained in adulthood. 6,34 Glucocorticoids play a role in the increased intestinal permeability induced by a short acute maternal separation stress in PND10 pups 17 but not in adult rats subjected to repeated maternal separation. 36,37 In the present study, we found no correlation between corticosterone plasma levels and intestinal permeability at weaning, either in LNS or BMS models, suggesting that glucocorticoids are not involved in the mechanisms contributing to the altered permeability.…”

“…14,17 Samples were centrifuged (10 minutes, 2500 g) and plasma was stored at -80 o C until assay. Plasma corticosterone concentration was determined by enzyme immunoassay (Cayman Chemical, Ann Arbor, MI, USA) according to the manufacturer's instructions.…”

“…14,17 Briefly, at 9 AM pups received oral gavage (70 µL) of fluorescein isothiocyanate (FITC) labeled 4 kDa dextran (FD4) (4 kDa; Sigma, Milwaukee, WI, USA), at the dose of 750 mg/kg body weight in 0.9% NaCl. After 4 hours, a sufficient transit time for FD4 to be recovered into the colon lumen, 17 rats were lightly hand restrained and blood (200 µL) was withdrawn from the facial vein using heparin-coated capillaries (SARSTEDT, Saint James Church Road, NC, USA).…”

“…3C). This included fiber-degrading microbes such as Oscillospira (47 OTUs), Ruminococcus (17), and Lachnospira (3); butyrate-producing microbes such as Roseburia (27), Coprococcus (10), and Eubacterium dolichum; and the mucus-resident bacteria Akkermansia mucinophila and Mucispirillum schaedleri. There was increased abundance of 20 genera (representing 204 enriched OTUs), of which 8 were Gram positive cocci: Enterococcus (6 OTUs), unclassified Enterococcaceae (2), Streptococcus (4), unclassified Streptococcaceae (1), Peptococcus (2), Aerococcus (3), Jeotgalicoccus (2), and Facklamia (1).…”

“…14 At weaning, the HPA axis is still in development 15,16 and the intestinal barrier permeability to macromolecules is high and declines thereafter although it remains more permeable up to PND40. [17][18][19] During this period, bacterial colonization is in process and promotes the development of food tolerance and immune function. 20 Of importance, recent reports in rodents indicate that early-life stress may influence the microbiota which could be associated with long lasting effects.…”