Isolation, identification and characterisation of a triterpenoid RORγ inverse agonist

The nuclear receptor RAR-related orphan receptor gamma (RORγ) plays a pivotal role in the differentiation of naïve CD4+T cells towards pro-inflammatory T helper 17 (Th17) cells [1]. This distinct lineage of T helper cells are important host defenders but also contribute to various autoimmune diseases like rheumatoid arthritis, multiple sclerosis, psoriasi and severe neutrophilic asthma [2] [3]. To improve treatment of these ailments, new innovative therapeutic approaches like RORγ inverse agonists are heavily sought after.

In this study, we have identified a triterpenoid RORγ inverse agonist by luciferase assays. This natural product demonstrated potent (IC₅₀=119 nM) and selective inhibition of the RORγ nuclear receptor over other nuclear receptors commonly modulated by triterpenes. To investigate the differences in binding mode between this new inverse agonist and weak RORγ inverse agonists such as oleanolic acid (IC₅₀=9 µM) [4], we conducted molecular docking, which revealed distinct binding modes. These results were further validated by using site-directed mutagenesis and luciferase assays. Furthermore, we conducted biological examinations on both gene (qPCR) and protein levels (flow cytometry): Upon treatment, we found a significant decrease in the expression of RORγ target genes glucose-6-phosphatase [5] and interleukin-17 [1] and showed a reduction in Th17 differentiation, further corroborating the potential of this unprecedented natural product.

In conclusion, we have successfully identified and characterised a new potent and selective natural triterpenoid RORγ inverse agonist, which could serve as a useful tool compound for future endeavours.

 

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Conflict of Interest

The authors declare no conflict of interest.

• References

• 1 Ivanov lIl. et al. The orphan nuclear receptor RORgammat directs the differentiation program of proinflammatory IL-17+Thelper cells. Cell 2006; 126 (06) 1121-33
• 2 Gege C.. Retinoic acid-related orphan receptor gamma t (RoRgammat) inverse agonists/antagonists for the treatment of inflammatory diseases – where are we presently?. Expert Opin Drug Discov 2021; 1-19
• 3 Ramakrishnan R.K., Al Heialy S., Hamid Q.. Role of IL-17 in asthma pathogenesis and its implications for the clinic. Expert Rev Respir Med 2019; 13 (11) 1057-1068
• 4 Kim S.H., Hong J.H., Lee Y.C.. Oleanolic acid suppresses ovalbumin-induced airway inflammation and Th2-mediated allergic asthma by modulating the transcription factors T-bet, GATA-3, RORgammatand Foxp3in asthmatic mice. Int Immunopharmacol 2014; 18 (02) 311-24
• 5 Takeda Y.. et al. Retinoic acid-related orphan receptor gamma (RoRgamma): a novel participant in the diurnal regulation of hepatic gluconeogenesis and insulin sensitivity. PLos Genet 2014; 10 (05) e1004331

Publication History

Article published online:
16 November 2023