Identification of phenanthridine derivatives Wnt agonists and their effects on melanin levels
Phenanthridines have been identified as specific Wnt/β -catenin signalling agonists. To identify more potent Wnt agonists, we designed and synthesized phenanthridine derivatives as Wnt agonists and performed studies on their structural optimization and structure-activity relationships (SAR). Thus, we identified additional potent Wnt agonists, including HCJA121, HCJA404, and compounds 1–6 (Fig. 1a, Fig. S1).
The effects of these eight phenanthridine derivatives on the levels of melanin were initially evaluated in B16-F10 cells treated with Wnt3a-conditioned media, using 8-methoxypsoralan (8-MOP) (Lerner, Denton & Fitzpatrick, 1953) as a positive control. The absorbance of the same number of cells treated with phenanthridine derivatives at 50 μ M indicated that HCJA121 and HCJA404 strongly promoted melanin synthesis compared to 8-MOP (Fig. 1b). Particularly, among these compounds, HCJA121 and HCJA404 performed the best, promoting melanogenesis in a dose-dependent manner, with EC50 values of 4.68μ M and 7.12 μ M, respectively, which were considerably better than that of 8-MOP (EC50 = 24.36 μ M). Therefore, HCJA121 and HCJA404 were deemed suitable for further bioassays, and 20 μ M was chosen as an effective treatment concentration. The effect of HCJA121 and HCJA404 on tyrosinase was measured by ʟ-DOPA oxidation. Compared with treatment with DMSO alone (untreated condition), treatment with 20 μ M HCJA121 and HCJA404 resulted in an increase in tyrosinase activity in the B16 cells (Fig. 1c), which suggested that HCJA121 and HCJA404 exhibit good potential for improving vitiligo symptoms.