Digoxin, an Overlooked Agonist of RORγ/RORγT

Digoxin was one of the first identified ROR gamma T receptor inverse agonists inhibiting the differentiation of Th17 cells. However, this compound exhibits inhibitory activity at relatively high concentrations that mediate cytotoxic effects. We previously identified several cardenolides that are structurally similar to digoxin that were able to induce ROR gamma/ROR gamma T-dependent transcription. These observations encouraged us to reanalyze the effects of digoxin on ROR gamma/ROR gamma T-dependent transcription at low, noncytotoxic concentrations. Digoxin induced ROR gamma/ROR gamma T-dependent transcription in HepG2 and Th17 cells. Furthermore, analysis of the transcriptomes of Th17 cells cultured in the presence of digoxin revealed the induction of the expression of numerous Th17-specific genes, including IL17A/F, IL21, IL22, IL23R, CCR4, and CCR6. Thus, our study, which includes data obtained from intact cells, indicates that digoxin, similar to other cardenolides, is a potent ROR gamma/ROR gamma T receptor activator and that its structure may serve as a starting point for the design of dedicated molecules that can be used in the development of adoptive cell therapy (ACT).