The cardenolides strophanthidin, digoxigenin and dihydroouabain act as activators of the human RORγ/RORγT receptors

Two isoforms of a ligand-activated nuclear receptor, ROR gamma and ROR gamma T, have been implicated in various physiological functions, including energy metabolism, circadian rhythm and immune system development. Using a stably transfected reporter cell line, we screened two chemical libraries and identified three cardenolides (natural, plant-derived pesticides) as activators of ROR gamma-dependent transcription. These compounds increased G6PC and NPAS2 expression in HepG2 cells, accompanied by increased occupancy of RORy within the promoters of these genes. Further, strophanthidin, digoxigenin and dihydroouabain upregulated IL17A and IL17F expression and enhanced IL17 secretion in Th17 human lymphocytes. Molecular docking analyses of these compounds to the ROR gamma LBD showed favorable docking scores, suggesting that cardenolides may act as agonists of the receptor. Thus, our results provide new chemical structures for further development of ROR gamma-selective modulators with virtual therapeutic potential.