Effects of pine needle essential oil on melanin synthesis in B16F10 cells and its mechanism

The present study aimed to investigate the melanin synthesis effect of pine needle essential oil (PNEO) extracted using microwave-assisted extraction on α-MSH-induced B16F10 melanoma cells and its molecular mechanism of action. Cell Counting Kit-8 was used to measure the safe concentration of B16F10 cells after 24 and 48 h post-treatment. Tyrosinase (TYR) activity assay was used to examine intracellular enzyme viability; western blotting (WB) and reverse transcription-quantitative (RT-qPCR) assays were utilized to assess the transcription and expression of genes and proteins associated with melanogenesis. Relevant targets in the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway were verified by the addition of target inhibitors or activators. Results showed that PNEO decreased the levels of melanin and the activity of TYR in B16F10 cells. RT-qPCR and WB results showed that PNEO downregulated the expression of melanogenesis-related genes and proteins such as microphthalmia-associated transcription factor, TYR, TYR-related protein-1 and melanocortin 1 receptor, and reduced the levels of phosphorylated PKA and phosphorylated cyclic-AMP response binding protein. These results suggested that the inhibitory effect of PNEO on melanin production may be related to the cAMP/PKA pathway. Verification through the addition of target inhibitors or activators confirmed that PNEO regulates melanin synthesis and TYR activity through the cAMP/PKA signaling pathway.