Autophagy inducer can regulate skin pigmentation by melanosome degradation in both keratinocytes and melanocytes

Autophagy is a process that regulates cellular turnover by recycling or disassembling unnecessary or dysfunctional constituents. As a catabolic self-protective mechanism, autophagy is widely explored in various disease models. Recent studies have demonstrated that autophagy and its regulators can play a wide variety of roles in melanocyte biology. Activation of autophagy is known to induce melanogenesis in melanocytes. Also, autophagy induction was reported to regulate physiologic skin color via melanosome degradation, yet the downstream effectors are not clarified. To determine the role of autophagy as degradation machinery in melanocyte biology, we administered several autophagy inducers in human keratinocytes and melanocytes. Our results showed that a synthetic autophagy inducer stimulated autophagic flux within human melanocytes and keratinocytes with transferred melanosomes. Increased autophagic flux led to melanosome degradation without affecting the expression of MITF. Furthermore, the color of cell pellets of both melanocytes and keratinocytes were visibly lightened. Inhibition of autophagic flux by chloroquine treatment resulted in marked attenuation of melanosome degradation, which was triggered by an autophagy inducer, while the expression level of the melanogenesis pathway remained unaffected. Taken together, we suggest that the modulation of autophagy can contribute to regulating the complex process of melanocyte biology and skin pigmentation.