Sodium butyrate converts Caco-2 monolayers into a leaky but healthy intestinal barrier resembling that of a newborn infant

Abstract

A simple and reliable in vitro model of the infant intestinal barrier is needed to study nutrient absorption and drug permeability specifically for this life stage. This study investigated the treatment of 20 day old differentiated Caco-2 monolayers with sodium butyrate at various concentrations (0–250 mM). Monolayer integrity, cytotoxicity, permeability and inflammatory response were tracked. An intestinal barrier model, with infant gut characteristics, was developed based on the treatment of mature monolayers with 125 mM sodium butyrate for 24 h. Such treatment was not cytotoxic but caused a stable transepithelial electrical resistance value of 408 ± 52 Ω cm². The ratio of lactulose to mannitol transport across the intestinal barrier increased 1.79-fold. Redistribution of the tight junction proteins, occludin and ZO-1, in response to sodium butyrate treatment was visualized with immunofluorescence. Levels of the cytokines, TNF-α and IL-6, although modestly increased did not indicate an inflammatory response by Caco-2 to sodium butyrate. This intestinal barrier demonstrated physiologically relevant transport rates for dairy protein of 0.01–0.06%, suggesting it may be used to track permeability of proteins in infant nutritional products.