Precocious gut maturation and immune cell expansion by single dose feeding the lectin phytohaemagglutinin to suckling rats

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

The gastrointestinal tract (GIT) is the first point of contact for ingested substances and thus represents a direct interface with the external environment. Apart from food processing, this interface plays a significant role in immunity and contributes to the wellbeing of individuals through the brain-gut-microbiota axis. The transition of life from the in utero environment, to suckling and subsequent weaning has to be matched by phased development and maturation of the GIT; from an amniotic fluid occupancy during gestation, to the milk in the suckling state and ultimately solid food ingestion at weaning. This phased maturation of the GIT can be affected by intrinsic and extrinsic factors, including diet. Despite the increasing dietary inclusion of medicinal plants and phytochemicals for health benefits, a dearth of studies addresses their impact on gut maturation. In this review we focus on some recent findings mainly on the positive impact of medicinal plants and phytochemicals in inducing precocious maturation of the GIT, not only in humans but in pertinent animals. We also discuss Paneth cells as mediators and potential markers of GIT maturation.

Impact of dietary induced precocious gut maturation on cecal microbiota and its relation to the blood-brain barrier during the postnatal period in rats

BACKGROUND

Precocious maturation of the gastrointestinal barrier (GIB) in newborn mammals can be induced by dietary provocation, but how this affects the gut microbiota and the gut-brain axis remains unknown. The objective of this study was to investigate effects of induced GIB maturation on gut microbiota composition and blood-brain barrier (BBB) permeability.

METHODS

Suckling rats were studied at 72 h after gavage with phytohemagglutinin (PHA) or microbial protease (PT) to induce maturation of GIB. For comparison, untreated suckling and weaned rats were included (n = 10). Human serum albumin (HSA) was administered orally and analyzed in blood to assess permeability of the GIB, while intraperitoneally injected bovine serum albumin (BSA) was measured in the brain tissue for BBB permeability. The cecal microbial composition, plasma lipopolysaccharide-binding protein (LBP) levels and short-chain fatty acids in serum and brain were analyzed.

KEY RESULTS

Cessation of HSA passage to blood after PHA or PT treatment was similar to that seen in weaned rats. Interestingly, concomitant increases in cecal Bacteroidetes and plasma LBP levels were observed after both PHA and PT treatments. The BBB passage of BSA was surprisingly elevated after weaning, coinciding with lower plasma LBP levels and specific microbial taxa and increased acetate uptake into the brain.

CONCLUSIONS & INFERENCES

This study provides evidence that the gut microbiota alteration following induced precocious GIB maturation may induce low-grade systemic inflammation and alter SCFAs utilization in the brain which may also play a potential role in GIB-BBB dysfunction disorders in neonates.

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

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.

Induction of precocious intestinal maturation in T-cell deficient athymic neonatal rats

AIM

To investigate whether gut maturation could be induced precociously in an athymic T-cell deficient neonatal rat model.

METHODS

Fourteen day-old athymic (nude) rats (NIH-Foxn1^rnu) were gavaged with either phytohaemagglutinin - a lectin from red kidney beans (PHA); trypsin - a protease (Prot); or water - vehicle (control) as a single dose on one day or once a day for 3-day. The nude rats were either nurtured by their mothers or cross-fostered by conventional foster dams of the Sprague-Dawley strain from days 3-5 after birth. At 17 d of age, 72 h after administration of the first treatment, intestinal macromolecular permeability was tested in vivo, prior to euthanasia, after which blood and gut organs were sampled.

RESULTS

Provocation with both, PHA and protease, resulted in increased gut growth and maturation in nude rat pups independent of nursing. Foetal-type enterocytes were replaced by non-vacuolated adult-type enterocytes in the distal small intestine epithelium. Decreased intestinal macromolecular permeability (gut closure) was observed, with reduced permeability markers (BIgG and BSA, P < 0.001) in circulation. Increased pancreatic function, with an increased trypsin to protein ratio in pancreas homogenates, was observed independent of nursing in the nude pups. Immunostaining showed the presence of a few CD3⁺-cells in the intestinal mucosa of the nude pups. The number of CD3⁺-cells remained unaltered by provocation and no differences were observed between the nursing sets. Growth and vitality of the nude pups were dependent on nurturing, since cross-fostering by conventional dams increased their macromolecular absorptive capacity (BSA, P < 0.05), as well as their passive immunity (RIgG, P < 0.05).

CONCLUSION

Precocious gut maturation can be induced by enteral provocation in athymic rat pups, similarly to in euthymic pups, thus showing an independence from thymus-derived T-cells.

Spray-dried porcine plasma and yeast derived protein meal influence the adaption to weaning of primiparous and multiparous sow progeny in different ways

Pigs from 154 litters (n = 1132, 19 ± 3 days of age, 4.9 ± 1.1 kg of bodyweight) were used in a 3 × 2 factorial design to evaluate two raw materials with nutraceutical properties being used in feeds, spray-dried porcine plasma (SDPP) and a yeast protein meal, and their effects on growth performance, immune parameters and gastrointestinal adaption of piglets to weaning. Factors included dietary treatments being (1) 5% SDPP (PLA), (2) 3.5% yeast protein meal (NUP) and (3) medicated control (TMC) and parity (primiparous versus multiparous). The treatment groups were imposed from Day 19 through to weaning at Day 27. Selected pigs (n = 720, 28 ± 3 days of age, 7.4 ± 1.0 kg of bodyweight) were weaned and remained on their respective diets from Day 28 to Day 34. From Day 35 to Day 48 all group-housed pigs were offered a commercial weaner 1 diet, and from Day 49 to Day 68 pigs were offered a commercial weaner 2 diet. Growth performance, survival, and serum immunoglobulin G were monitored throughout the nursery phase (Day 28 to Day 68). Adaptation of the gastrointestinal tract in the acute post-weaning phase (Day 28 to Day 34) was assessed in 36 individually housed male weaners, with the effects of feed on structural, digestive, microbial and immune parameters along the gastrointestinal tract determined at Day 34. Pre-weaning feed disappearance was greater (P < 0.01) in multiparous litters independent of diet. In the commercial nursery, total removals (mortality and morbidity) were highest (P < 0.01) in primiparous sow progeny, with pigs offered NUP having greater (P ≤ 0.05) total removals. Pigs offered PLA had superior average daily gain, average daily feed intake and feed conversion ratio from Day 28 to Day 34 (P < 0.05). Pigs offered NUP tended to (P = 0.07) have superior average daily gain from Day 35 to Day 49. Pigs offered NUP had higher (P < 0.05) serum immunoglobulin G concentrations at Day 68 compared with pigs offered TMC, with the effect most pronounced in primiparous sow progeny. Individually housed weaners offered PLA consumed more (P < 0.05) feed on Day 30 to Day 31, had shorter relative intestine length (P < 0.05), greater villous height in the medial jejunum (P < 0.10) and lower immuno-pathology scores along the intestine. Pigs offered PLA also tended (P < 0.10) to have increased pancreatic-specific lipase and amylase activity compared with pigs offered NUP. Pigs offered NUP had a higher ratio of E. coli : coliforms in the colon (P < 0.01) and more counts of β-haemolytic bacteria in the medial jejunum (P < 0.05) and colon (P < 0.10). Diets containing either SDPP or NUP offered pigs benefits beyond nutrition relative to the medicated control diet. The benefits of SDPP were highly effective but transient, while the yeast derived protein had a successive or accumulative effect which was more pronounced in primiparous sow progeny.

Immune suppression by cyclosporin A inhibits phytohemagglutinin-induced precocious gut maturation in suckling rats

OBJECTIVES

Enteral exposure to the lectin phytohemagglutinin (PHA) provokes precocious gut maturation in suckling rats coinciding with an early expansion of intestinal mucosal T and B lymphocytes. Here, the role of the immune system in neonatal gut growth and maturation was further studied.

MATERIALS AND METHODS

The effects of immunosuppression by cyclosporine A (CyA), 7.5 microg/g of body weight, injected 12 hours before and then daily after the intragastric gavage of PHA, 100 microg/g body weight, to 14-day-old suckling rats were studied after 4 and 12 hours and later after 72 hours.

RESULTS

At 4 hours after PHA feeding, an early rapid increase in the intestinal levels of the proinflammatory cytokines interleukin-6, interleukin-1beta, and tumor necrosis factor was obtained, and the CyA treatment did not prevent the temporary PHA-induced intestinal disturbance seen at 12 hours. Later, at 72 hours after PHA gavage the CyA treatment significantly counteracted the PHA-induced gut changes with a decrease in small intestinal growth, a delay in the appearance of adult-phenotype enterocytes in the distal small intestinal, and total inhibition of the PHA-induced pancreas development. Additionally, the increase in plasma level of the acute phase protein, haptoglobin, after PHA feeding was dampened by CyA.

CONCLUSIONS

The results indicate that proinflammatory cytokines are involved in the early recruitment of lymphocytes to the gut after PHA challenge, and that the ensuing precocious gut maturation is dependent on activation of the immune system, presumably T cells, in suckling rats.