Differential effects of selected natural compounds with anti-inflammatory activity on the glucocorticoid receptor and NF-kappaB in HeLa cells

Abstract

Natural compounds have been used in the treatment of various diseases for centuries. Herein, we investigated the effects of structurally diverse alkaloids with anti-inflammatory activity (berberine, sanguinarine, chelerythrine, and colchicine) on two important anti-inflammatory and pro-inflammatory players, i.e. glucocorticoid receptor (GR) and nuclear factor kappa B (NF-kappaB), respectively. Sanguinarine and chelerythrine elicited nuclear translocation of the p65 subunit of NF-kappaB. The nuclear import of p65 was strongly augmented by these akaloids in non-stimulated cells as well as in cells challenged with tumor necrosis factor alpha (TNFalpha). Colchicine and berberine had no effect on p65 nuclear translocation regardless of the presence or absence of TNFalpha. Colchicine caused rapid degradation of the GR protein, whereas berberine had no effect on GR content or cellular localization. Sanguinarine and chelerythrine induced accumulation of GR in the nucleus with concomitant diminution of cytosolic GR. Analyses on the transcriptional activity of GR and NF-kappaB monitored by reporter assays using HeLa cells transiently transfected with glucocorticoid response element (pGRE-LUC) and/or NF-kappaB elements fused to luciferase gene (pNF-kappaB-luc) showed that none of the compounds tested had the capability to trigger GR and/or NF-kappaB transcriptional activities, respectively. The ligand binding assay showed that colchicine and berberine are not GR ligands whereas sanguinarine and chelerythrine significantly decreased binding of (3)H-labelled dexamethasone to GR. In conclusion, structurally diverse natural antiflogistics displayed differential effects on GR and NF-kappaB in HeLa cells.