Influence of phytogenics on recovery of the barrier function of intestinal porcine epithelial cells after a calcium switch.

BACKGROUND: The gut barrier is essential for animal health as it prevents the passage of potentially harmful foreign substances. The epithelial tight junctions support the intestinal barrier and can be disrupted by stress caused, for example, by pathogens or dietary or environmental factors, predisposing the host to disease. In animal husbandry, phytogenics (plant-derived feed additives) are used to support and maintain growth, feed efficiency and health. Therefore, several phytogenics were tested in vitro for their influence on the barrier function recovery of intestinal porcine epithelial cells (IPEC-J2) after disruption, particularly on the abundance of tight junction proteins. RESULTS: IPEC-J2 treated with 1,000 µg/ml liquorice root extract, 80 µg/ml plant powder mix, or 80 µg/ml angelica root powder showed significantly higher trans-epithelial electric resistance (TEER) 24 hr after tight junction disruption via a calcium switch assay than the control. In contrast, cells treated with 1,000 µg/ml oak bark extract showed a significantly lower TEER after 6 hr but not at later time points. The increased TEER caused by the liquorice root extract correlated with an increase in the abundance of the tight junction protein claudin-4. CONCLUSIONS: This study suggests potential beneficial effects of liquorice and angelica root extracts on the gut barrier function when used as feed additives for livestock. Further studies, especially in vivo, are necessary to confirm these findings.

Effects of phytogenic feed additives on cellular oxidative stress and inflammatory reactions in intestinal porcine epithelial cells1.

Due to increasing concerns about the use of antibiotic growth promoters (AGP) in livestock production and their complete ban in the European Union in 2006, suitable alternatives are urgently needed. Among others, anti-inflammatory activities of AGP are discussed as their putative mode of action. As numerous phytochemicals are known to modulate the cellular antioxidant capacity and immune response, we studied the antioxidative and anti-inflammatory properties of a phytogenic (plant-derived) feed additive (PFA) in intestinal porcine epithelial cells (IPEC-J2). The effects of the PFA were compared with those of selected phytogenic ingredients (grape seed extract [GRS], licorice extract [LIC], menthol [MENT], methyl salicylate [MES], oak bark extract [OAK], oregano essential oil [ORE], and a plant powder mix [PLA]), and with the effects of the AGP tylosin (TYL). Oxidative or inflammatory stress was induced by stimulating IPEC-J2 with hydrogen peroxide (H2O2; 0.5 mM) or tumor necrosis factor alpha (TNF-α; 10 ng/mL), respectively. The antioxidative effects of feed additives were assessed with a reactive oxygen species (ROS)-sensitive probe and by measuring the expression of 6 antioxidative target genes via quantitative real-time PCR (RT-qPCR). Anti-inflammatory potential was analyzed using a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) reporter gene assay. Moreover, the expression levels of 6 NF-κB target genes were measured using RT-qPCR analysis, and the release of IL-6 was analyzed via ELISA. Significant decreases in cellular ROS upon H2O2 treatment were observed for the PFA (P < 0.001), LIC (P < 0.001), ORE (P < 0.05), and GRS (P < 0.01). No significant changes in the expression of antioxidative genes were found. NF-κB activation upon TNF-α treatment was significantly inhibited by the PFA (P < 0.05) and by ORE (P < 0.001). Moreover, the PFA and ORE significantly reduced the gene expression of IL-6 (P < 0.001), IL-8 (P < 0.001), and C-C motif chemokine ligand 2 (CCL2; P < 0.05), as well as the release of IL-6 (P < 0.05). The other phytogenic compounds as well as the AGP TYL did not significantly affect any of the inflammatory parameters. In summary, we revealed the antioxidative properties of the PFA, LIC, ORE, and GRS, as well as anti-inflammatory properties of the PFA and ORE in IPEC-J2, providing a better understanding of the mode of action of this PFA under our experimental conditions.