Intraluminal nutrients acutely strengthen rat intestinal MRP2 barrier function by a glucagon‐like peptide‐2‐mediated mechanism

Abstract

Aim MRP2 is an intestinal ABC transporter that prevents the absorption of dietary xenobiotics. The aims of this work were: (1) to evaluate whether a short‐term regulation of intestinal MRP2 barrier function takes place in vivo after luminal incorporation of nutrients and (2) to explore the underlying mechanism. Methods MRP2 activity and localization were assessed in an in vivo rat model with preserved irrigation and innervation. Nutrients were administered into distal jejunum. After 30‐minutes treatments, MRP2 activity was assessed in proximal jejunum by quantifying the transport of the model substrate 2,4‐dinitrophenyl‐S‐glutathione. MRP2 localization was determined by quantitative confocal microscopy. Participation of extracellular mediators was evaluated using selective inhibitors and by immunoneutralization. Intracellular pathways were explored in differentiated Caco‐2 cells. Results Oleic acid, administered intraluminally at dietary levels, acutely stimulated MRP2 insertion into brush border membrane. This was associated with increased efflux activity and, consequently, enhanced barrier function. Immunoneutralization of the gut hormone glucagon‐like peptide‐2 (GLP‐2) prevented oleic acid effect on MRP2, demonstrating the participation of this trophic factor as a main mediator. Further experiments using selective inhibitors demonstrated that extracellular adenosine synthesis and its subsequent binding to enterocytic A2B adenosine receptor (A2BAR) take place downstream GLP‐2. Finally, studies in intestinal Caco‐2 cells revealed the participation of A2BAR/cAMP/PKA intracellular pathway, ultimately leading to increased MRP2 localization in apical domains. Conclusion These findings reveal an on‐demand, acute regulation of MRP2‐associated barrier function, constituting a novel physiological mechanism of protection against the absorption of dietary xenobiotics in response to food intake.

The Art of Planning—How many samples are enough?

“…How big differences between samples generally are varied greatly between different fields of research. It is obvious that it is easier to tenfold a specific intracellular protein level than to tenfold muscular strength or diameter 23‐25 . Literature related to your research idea or preliminary experiments may give you a good indication about expected effects.…”

“…It is obvious that it is easier to tenfold a specific intracellular protein level than to tenfold muscular strength or diameter. [23][24][25] Literature related to your research idea or preliminary experiments may give you a good indication about expected effects. The spread of your data is important as well.…”

Tuning the intestinal barrier through the neuroendocrine control of ABC pumps expression

“…Based on their results obtained using wortmannin, Cheeseman suggested a role of phosphoinositide 3‐kinase (PI3K)‐dependent pathway in the activation of SGLT‐1 targeting to the apical membrane of epithelial cells in response to GLP‐2 administration. As discussed by Tocchetti et al in this issue, 2 it would be highly interesting to unravel whether other SLC transporters at the surface of the intestine are similarly regulated, improving nutrient absorption during the course of a meal.…”

“…The present editorial relates to the manuscript entitled "Intraluminal nutrients acutely strengthen rat intestinal MRP2 barrier function by a glucagon‐like peptide‐2‐mediated mechanism" published in Acta Physiologica by Prof. Mottino's group 2 3 the authors further investigated the impact of nutrients administered intraluminally in the rat distal jejunum on the function of MRP2 (gene symbol ABCC2 ) at the intestinal level.…”

“…The study by Tocchetti et al 2 is a typical example of an experimental approach with elegant design to elucidate a physiological question by combining in vitro models with well‐performed classical in vivo experiments. A valuable discovery of that study is the connection between the presence of nutrients in the intestinal lumen, such as oleic acid, and the response of the epithelial cells by tuning the efficacy of the intestinal barrier through the expression of MRP2.…”