Asoprisnil, a Selective Progesterone Receptor Modulator (SPRM), Inhibits Melanosome Export in B16F10 Cells and HEMn-DP Melanocytes

Abstract

Previous studies have reported that estrogen hormone promotes melanogenesis while progesterone inhibits it. A selective estrogen receptor modulator (SERM), tamoxifen, has been shown to promote melanogenesis; however, to date, there have been no reports on the effects of a selective progesterone receptor modulator (SPRM) on melanogenesis. In the present study, we hypothesized that asoprisnil (AP), a SPRM, inhibits melanogenesis. AP was tested for cytotoxicity to B16F10 mouse melanoma cells for screening the nontoxic concentrations using MTS cytotoxicity assay. Extracellular and intracellular melanin levels were estimated at nontoxic concentrations of AP. To evaluate the direct effect of AP on tyrosinase enzyme, tyrosinase activity and copper chelating activities were measured. Next, the effects of AP on melanogenesis were tested in normal human melanocytes, neonatal, darkly pigmented (HEMn-DP). Our results demonstrate that AP was nontoxic at a concentration range of 10–50 μM in B16F10 cells; AP at 50 μM significantly suppressed extracellular melanin levels comparable to kojic acid at 500 μM, with no significant effect on intracellular melanin levels. The mechanism of melanogenesis inhibition was studied to assess if AP downregulated tyrosinase activity in cell lysates or in a cell-free system. However, AP was found to increase intracellular tyrosinase activity without any effect on tyrosinase enzyme activity or copper chelating activity in a cell-free system, indicating that AP inhibits melanogenesis by mechanisms other than direct effects on tyrosinase enzyme activity. The capacity of AP to inhibit melanosome export was further validated in HEMn-DP cells; AP significantly suppressed dendricity at concentrations of 20 and 30 μM in the absence of effects on melanin synthesis or intracellular tyrosinase activity. In addition, AP was nontoxic to human keratinocytes (HaCaT) at these concentrations, validating its safety for topical use. Taken together, our preliminary results demonstrate that AP might be repurposed as a candidate therapeutic for treatment of hyperpigmentation disorders via a unique mechanism, which encompasses a selective inhibition of melanosome export.

Novel Chemically Modified Curcumin (CMC) Analogs Exhibit Anti-Melanogenic Activity in Primary Human Melanocytes

“…For the efficient export of melanosomes by melanocytes, both the dendrite length and number of dendrites are critical components, as melanocytes can branch out by increasing their number of dendrites to contact multiple keratinocytes that are in close proximity and can also elongate their dendrites to export pigment to multiple keratinocytes surrounding them in the suprabasal layers of the epidermis. The inhibition of melanosome export is emerging as a novel target when designing inhibitors of excessive pigmentation and a large number of reports [ 6 , 7 , 8 , 9 ], including our previous studies [ 10 , 11 , 12 ], have described compounds which can inhibit dendricity and thus have the potential to suppress export of melanosomes.…”

CMT-308, a Nonantimicrobial Chemically-Modified Tetracycline, Exhibits Anti-Melanogenic Activity by Suppression of Melanosome Export

“…Currently, several reports have documented novel compounds that have shown efficacy in reducing melanogenesis by inhibiting melanosome export through the reduction in dendricity [29][30][31]. Additionally, we have previously reported on a synthetic steroidal compound, asoprisnil [32], and a fungal-derived natural antibiotic, Thermorubin (TR) [33], both of which suppressed dendricity as one of the modes of inhibition of melanosome export. MITF, one of the key transcription factors which controls tyrosinase and other melanogenesis-related enzymes [34,35], also regulates melanocyte dendricity [36].…”

Comparative Study of Δ9-Tetrahydrocannabinol and Cannabidiol on Melanogenesis in Human Epidermal Melanocytes from Different Pigmentation Phototypes: A Pilot Study

“…HEMn-LP cells (1.5 × 10 5 cells/well) or HEMn-DP cells (1.2 × 10 5 cells/well) were cultured in 6-well plates for 24 h followed by the addition of test compounds and further cultured for 6 d. The relative levels of cellular melanin were determined in a manner similar to the method reported in previous studies [ 30 , 31 ]. Briefly, the cells were harvested, washed in PBS, and 150 μL of 1 N NaOH was added and heated to 70 °C to solubilize melanin.…”