This study was carried out to investigate protective effect of chlorogenic acid against lipopolysaccharide-induced inflammation and oxidative stress in intestinal epithelial cells. As a marker of inflammatory response, IL-6, IL-8, TNF-α mRNA and protein levels, furthermore, COX-2 mRNA level were followed up. Intracellular redox status and extracellular H2O2 level were also monitored by two fluorescent assays (DCFH-DA, Amplex Red). Moreover, the effect of gut microbiota metabolites in the above mentioned processes was taken into account in our model using Lactobacillus plantarum 2142 bacterial strain. Our data revealed that chlorogenic acid had significant lowering effect on the inflammatory response. Treatment with chlorogenic acid (25–50 μM) significantly decreased gene expression and concentration of proinflammatory cytokines IL-6 and IL-8 compared to LPS-treated cells. COX-2 and TNF-α mRNA levels were also reduced. Furthermore, chlorogenic acid reduced the level of reactive oxygen species in IPEC-J2 cells. Simultaneous application of chlorogenic acid and Lactobacillus plantarum 2142 supernatant resulted protective effect against LPS-induced inflammation and oxidative stress as well.

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The in vitro anti-inflammatory effect of apigenin and its trimethylated analogue (apigenin-trimethylether) has been investigated in order to evaluate whether these flavonoids could attenuate LPS-induced inflammation in IPEC-J2 non-transformed intestinal epithelial cells. Levels of IL-6, IL-8, TNF-α, and COX-2 mRNA were measured as a marker of inflammatory response. The extracellular H2O2 level in IPEC-J2 cells was also monitored by Amplex Red assay. Our data revealed that both compounds had significant lowering effect on the inflammatory response. Apigenin (at 25 μM) significantly decreased gene expression of IL-6 in LPS-treated cells, while apigenin-trimethylether in the same concentration did not influence IL-6 mRNA level. Both apigenin and apigenin-trimethylether reduced IL-8 gene expression significantly. TNF-α mRNA level was decreased by apigenin-trimethylether, which was not influenced by apigenin. Treatment with both flavonoids caused significant reduction in the mRNA level of COX-2, but the anti-inflammatory effect of the methylated analogue was more effective than the unmethylated one. Furthermore, both flavonoids reduced significantly the level of extracellular H2O2 compared to the control cells. In conclusion, the methylated apigenin analogue could avoid LPS-induced intestinal inflammation and it could be applied in the future as an effective anti-inflammatory compound.

This study was based on our previously developed double-layered enterohepatic co-culture system, composed of nontumorigenic porcine intestinal epithelial cell line (IPEC-J2) and primary culture of porcine hepatocytes. The anti-inflammatory effect of spent culture supernatant of Lactobacillus plantarum 2142 (Lp2142; 13.3%) and sodium n-butyrate (2 mM) was tested on IPEC-J2 and hepatocyte monocultures as well as on the gut-liver co-culture. To mimic inflammation, lipopolysaccharide (LPS; 1 and 10 μg/mL) was applied. Production of IL-8 and IL-6 was measured as a marker of inflammatory responses. The paracellular permeability of the intestinal epithelium was also monitored by fluoresceinisothiocyanate-labeled dextran 4 assay. Significant increase of IL-8 concentration was observed in the IPEC-J2 monoculture (P < 0.01) while the level of IL-6 was not changed following LPS treatment. Concentration of IL-8 and IL-6 was grown significantly in hepatocyte monocultures (P < 0.05 and P < 0.001) as well as in the co-culture after 10 μg/mL LPS treatment (P < 0.001 and P < 0.001). One microgram per milliliter LPS caused elevated IL-8 level in the co-culture (P < 0.001) and in the hepatocyte monoculture (P < 0.01), while it caused increased IL-6 level only in the hepatocytes (P < 0.001). Production of IL-8 was significantly decreased by butyrate in case of 1 μg/mL as well as 10 μg/mL LPS exposure in the co-culture (P < 0.001). Application of butyrate also reduced IL-6 level in the co-culture after 10 μg/mL LPS treatment (P < 0.01). Lactobacillus plantarum 2142 decreased IL-8 level after incubation with 1 μg/mL LPS (P < 0.001), while in case of 10 μg/mL LPS treatment only a marginal lowering in IL-8 (P = 0.064) release was measured. The IL-6 concentration was significantly reduced (P < 0.01 in case of 1 μg/mL LPS treatment) by Lp2142 in the co-culture. Contrarily, the elevated IL-8 and IL-6 level of hepatocytes has not been reduced in case of either butyrate or Lp2142 addition. The enterohepatic co-culture model offers a possibility for fast and reliable screening of new candidates against enteric inflammation, which are of special interest in porcine medicine and health management. According to our results, Lp2142 and butyrate both seem to be effective as anti-inflammatory agents in LPS-triggered inflammatory response, tested in the gut-liver co-culture model.

A porcine enterohepatic co-culture system, with primary hepatocytes as bottom layer and IPEC-J2 epithelial cells as upper layer, was developed to study the effects of lipopolysaccharides (LPS) on the gene expression profile of pro-inflammatory cytokines (interleukin-8 (IL-8) and tumor necrosis factor-α) and CYP enzymes (CYP1A1, CYP1A2, CYP3A29). The barrier integrity of IPEC-J2 cells was investigated by transepithelial electrical resistance measurements and by fluorescein isothiocyanate-dextran-based test. Basolateral IL-8 production was significantly elevated in LPS-treated IPEC-J2 and primary hepatocyte mono-cultures as well as in the co-culture system, in a dose-independent manner. The LPS-induced changes in the expression of the CYP1A2 and CYP3A29 genes in hepatocyte mono-cultures differed from those in co-culture after LPS treatment on the apical side of the IPEC-J2 cell layer. CYP1A2 was downregulated by the LPS treatment in mono-cultures but upregulated at 10 μg/ml LPS in co-culture; gene expression of CYP3A29 showed no significant LPS-induced change in the hepatocyte mono-culture but was significantly downregulated in co-culture. The newly established co-culture system capable of mimicking enterohepatic interplay in LPS-induced inflammatory responses in vitro can be used in the future for reliable screening of potential anti-inflammatory compounds.