Early effects on the intestinal barrier and pancreatic function after enteral stimulation with protease or kidney bean lectin in neonatal rats

Abstract

Gut maturation naturally accelerates at weaning in altricial mammalian species, such as the rat. Mimicking this, gut development can also be induced precociously, 3-4 d earlier than it would occur naturally, by enteral exposure to phytohaemagglutinin (PHA), or various proteases. We investigated the early effects of gut provocation on intestinal barrier and pancreatic functions, to get a better understanding of the mechanisms that initiate gut maturation. The effects of oral administration of protease (trypsin) or PHA to 14-d-old suckling rats were studied during 24 h in comparison with water-fed controls. Intestinal in vivo permeability was assessed by oral administration of different-sized marker molecules and measuring their passage into the blood or urine 3 h later. A period of 24 h following oral administration, both PHA and protease provocation stimulated small intestinal (SI) growth and pancreatic secretion, as indicated by decreased pancreatic trypsin and increased luminal enzyme content. Within 1 h of oral administration, both treatments prevented the absorption of macromolecules to blood that was observed in controls. PHA treatment hindered the passage of fluorescein isothiocyanate-dextran (FD) 4 to blood, whereas protease treatment temporarily increased plasma levels of FD4, and the urine lactulose:mannitol ratio, indicating increased intestinal leakiness. Following protease treatment, fluorescence microscopy showed decreased vesicular uptake of FD70 in the proximal SI and increased epithelial fluorescence in the distal SI. In conclusion, PHA and protease differed in their early effects on the intestinal barrier; both exerted a blocking effect on epithelial endocytosis, whereas protease treatment alone temporarily increased epithelial leakiness, which seemed to be confined to the distal SI.

The Immature Gut Barrier and Its Importance in Establishing Immunity in Newborn Mammals

“…Hence, PHA is thought to have blocked epithelial "receptors" needed for endocytosis. In contrast, provocation feeding with a protease caused an instant decrease in receptor-mediated endocytosis, a gradual decrease in the non-specific endocytic pathway and a temporary increase in paracellular leakiness (147).…”

“…Experiments in neonatal rats have shown that anti-nutritional factors, such as lectins, block intestinal absorption (145), and oral provocation with the lectin PHA severely decreases endocytosis immediately after exposure (146,147), due to the binding to the epithelial surface (146,148,149). Hence, PHA is thought to have blocked epithelial "receptors" needed for endocytosis.…”

Medicinal Plants, Phytochemicals, and Their Impacts on the Maturation of the Gastrointestinal Tract

“…The natural process of gut maturation can be induced precociously by abrupt weaning (Lee and Lebenthal, 1983), corticosteroids (Martín et al, 1993), provocation with pancreatic or pancreatic-like proteases (Prykhodko et al, 2015;Sureda et al, 2018) and polyamines (Dufour et al, 1988;Bekebrede et al, 2020), amongst other factors. Additionally, several studies indicate that a diverse range of medicinal plants and phytochemicals have potential as maturational agents to the developing gut (Supplementary Table 1).…”

Monobutyrin and Monovalerin Affect Brain Short-Chain Fatty Acid Profiles and Tight-Junction Protein Expression in ApoE-Knockout Rats Fed High-Fat Diets

“…The intestinal in vivo permeability test in rats was conducted by measuring the absorption of lactulose and mannitol according to Meddings and Gibbons [22,23], as previously described [16]. Concentrations of lactulose and mannitol quantitatively collected in urine were analyzed with the EnzyChromTM Intestinal Permeability Assay Kit (EIPM-100) from BioAssay System (Hayward, CA, USA).…”

“…The mucosal thickness was measured in three parts of the small intestine, including the duodenum, middle part of the jejunum and ileum, and in the upper colon of the rats according to previous procedures with some modifications [23,24]. After fixation in 4% paraformaldehyde, all tissue samples were washed with phosphate-buffered saline and cryoprotected with 30% sucrose by incubation for 24 h. All tissues were embedded into cryo-moulds (Sakura, Torrance, CA, USA) using the optimal cutting temperature compound TissueTek®(HistoLab, Gothenburg, Sweden), immediately frozen on dry ice, and stored at −80 • C. The cryosection of animal tissues was performed on a Leica CM1860 Cryostat (Leica Microsystems AB, Germany).…”