Melanocytes Sense Blue Light and Regulate Pigmentation through Opsin-3

Abstract

The shorter wavelengths of the visible light spectrum have been recently reported to induce a long-lasting hyperpigmentation but only in melano-competent individuals. Here, we provide evidence showing that OPN3 is the key sensor in melanocytes responsible for hyperpigmentation induced by the shorter wavelengths of visible light. The melanogenesis induced through OPN3 is calcium dependent and further activates CAMKII followed by CREB, extracellular signal-regulated kinase, and p38, leading to the phosphorylation of MITF and ultimately to the increase of the melanogenesis enzymes: tyrosinase and dopachrome tautomerase. Furthermore, blue light induces the formation of a protein complex that we showed to be formed by tyrosinase and dopachrome tautomerase. This multimeric tyrosinase/tyrosinase-related protein complex is mainly formed in dark-skinned melanocytes and induces a sustained tyrosinase activity, thus explaining the long-lasting hyperpigmentation that is observed only in skin type III and higher after blue light irradiation. OPN3 thus functions as the sensor for visible light pigmentation. OPN3 and the multimeric tyrosinase/tyrosinase-related protein complex induced after its activation appear as new potential targets for regulating melanogenesis but also to protect dark skins against blue light in physiological conditions and in pigmentary disorders.

Effects of blue light on inflammation and skin barrier recovery following acute perturbation. Pilot study results in healthy human subjects

“…It might be tempting to speculate that irradiation with blue light generated immediate pigment darkening (IPD), a phenomenon which has already been reported for UVA irradiation (315‐400 nm) . Indeed, human epidermal melanocytes are known to express OPN2, OPN3, and OPN5: while OPN2 was previously shown to mediate UV response leading to melanogenesis, very recent evidence demonstrated the impact of blue light on the increase in skin pigmentation, mediated by OPN3 . This finding could potentially explain the effect observed in this study.…”

Melasma: Updates and perspectives

“…Photoprotection is critical in preventing relapse or exacerbation of melasma. In addition to the conventional UVA and UVB protection, visible light should be avoided in melasma patients since shorter wavelengths of visible light (blue light) promote hyperpigmentation through opsin 3 in melanocyte . Sunscreens that contain iron oxide, which blocks shorter wavelength of visible light and broad‐spectrum UVA/UVB filters, significantly lowered the relapse of melasma during summer when compared with broad‐spectrum UVA/UVB protection alone …”

Differential response of human dermal fibroblast subpopulations to visible and near‐infrared light: Potential of photobiomodulation for addressing cutaneous conditions

“…Traditionally, cytochrome c oxidase and nitrozated proteins were considered as the major targets of light . Recently, there has been increasing evidence that cryptochromes and opsins , mediate the cell's response to visible and UV light. All this suggests that there are several molecular targets, which could intercept a photon of light and trigger multiple signaling cascades.…”