Introduction Hydrophobic bile acids have been identified as aetiological agents in inflammatory oesophageal diseases. Ursodeoxycholic acid (UDCA) has been shown to attenuate the inflammatory effects of hydrophobic bile acids in numerous cell lines. This has been shown to be partly mediated by UDCA activation of the glucocorticoid receptor (GR). Here, we investigate the potential role of UDCA in modulating the GR in oesophageal cell lines.
Methods Western blot analysis and RT-PCR were used to characterise GR expression in oesophageal cell lines (HET1A, SKGT-4). High Content Analysis (GE In-Cell analyser 1000) was used to investigate nuclear translocation of the GR in response to UDCA stimulation. Trans-activation of glucocorticoid response elements (GRE) was determined in a transient transfection assay using a construct of the human GRE promoter ligated to a firefly luciferase reporter gene Similarly trans-repression of NFKB was determined using a construct of the human NFKB promoter ligated to a luciferase reporter gene.
Results GR was found to be present in the oesophageal cell lines used at the mRNA and protein levels. No GRβ was expressed at the mRNA level suggesting that the GR present is GRα. UDCA induced translocation of the GR in a time- and concentration-dependent manner (EC50 of 298.68 μM in SKGT-4 and 320 μM in HET1A cell lines, 54% and 36% efficacy of dexamethasone 100 nM, respectively, both p<0.05 relative to untreated control). UDCA activated the GRE at 300 μM (22% efficacy of dexamethasone 100 nM, p<0.05). UDCA was found to inhibit TNF-α stimulated NFKB activation in HEK-293 cells at 300 μM (100% efficacy of dexamethasone 100 nM, p<0.05).
Conclusion Glucocorticoids are used as anti-inflammatory agents for treating a spectrum of diseases. Their chronic use is limited due to serious side effects, primarily thought to be due to GR-mediated transactivation. Here we show that UDCA can act as a GR modulator, with the ability to differentiate between transrepression and transactivation pathways. As a result UDCA may be of benefit in treating inflammatory conditions of the oesophagus.
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