Phosphodiesterase-4 Inhibitors Increase Pigment Cell Proliferation and Melanization in Cultured Melanocytes and within a 3-Dimensional Skin Equivalent Model.

Vitiligo is a common chronic autoimmune disease characterized by white macules and patches of the skin, having a negative impact on patients' life and without any definitive cure at present. Identification of new compounds to reverse depigmentation is therefore a pressing need for this disease. The pharmacologic compounds phosphodiesterase-4 inhibitors (PDE4is) are small molecules with immunomodulatory properties used for treatment of inflammatory dermatoses. PDE4is have shown repigmentation effects in patients with vitiligo, in some case reports. We characterized the proliferative and melanogenic potential of 2 known PDE4is-crisaborole and roflumilast-and of a more recently designed compound, PF-07038124. We used 2 in vitro model systems-the primary human melanocyte culture and a 3-dimensional cocultured skin model (MelanoDerm)-with an exploratory testing platform composed of complementary assays (spectrophotometry, melanin and proliferation assays, immunostaining, Fontana-Masson staining, RT-qPCR, western blot, and whole-transcriptome RNA sequencing). We identified that treatment with PDE4is was associated with increased melanocyte proliferation and melanization in both in vitro models and with increase in the melanogenic genes and proteins expression in cultured melanocytes. These effects were found to be enhanced by addition of α-melanocyte-stimulating hormone. Our findings support the further evaluation of PDE4is with or without α-melanocyte-stimulating hormone agonists in vitiligo trials.