A novel liquid plasma derivative inhibits melanogenesis through upregulation of Nrf2

Non-thermal plasma (NTP) is an emerging technology with extensive applications in biomedicine, including treatment of abnormal pigmentation. However, very few studies have investigated how plasma induces anti-melanogenesis. Here, liquid plasma was prepared by treating an NTP jet with helium and oxygen (as carrier gases) for 15 min in serum-free culture media. In the zebrafish model, pigmentation ratio was observed with or without liquid plasma. The anti-melanogenic effect of liquid plasma was evaluated in human melanocytes by assessing the expression of melanogenesis-related genes using western blotting, RT-PCR, and immunohistochemistry. Liquid plasma reduced pigmentation in the zebrafish model and inhibited melanin synthesis in primary human melanocytes. Intracellular reactive oxygen species levels decreased and Nrf2 expression increased in liquid plasma-treated melanocytes. Liquid plasma affected microphthalmia-associated transcription factor (MITF) and tyrosinase mRNA and protein levels, tyrosinase activity, and melanin content. Considering the role of Wnt/β-catenin and PI3K/Akt pathways in melanogenesis, the effect of liquid plasma on this pathway was determined; liquid plasma decreased active β-catenin, LEF1/TCF4, MITF, and tyrosinase levels in a time-dependent manner and inhibited the nuclear translocation of β-catenin. This inhibition subsequently suppressed melanogenesis by downregulating MITF and tyrosinase. These results suggest that liquid plasma may be used for treating pigmentary disorders.