<i>Laetiporus sulphureus</i> Mycelial Extract Promotes Melanogenesis via p38 MAPK-Mediated Activation of β-Catenin/MITF and Rho Family Proteins in B16F10 Cells

<i>Laetiporus sulphureus</i> mycelial extract (LSM) has shown potential as a pigmentation modulator. This study investigated the effects of LSM on melanogenesis in B16F10 cells. LSM significantly increased both extracellular and intracellular melanin content. It also upregulated tyrosinase protein expression and activity, along with MITF and β-catenin levels. LSM activated ERK1/2, p38, and JNK phosphorylation; however, only p38 inhibition suppressed LSM-induced melanin synthesis and the expression of melanogenesis-related proteins. Moreover, LSM increased the protein levels of Rho family GTPases (Cdc42, Rac1, RhoA), which was also blocked by p38 inhibition. These findings suggest that LSM promotes melanogenesis through p38 MAPK-dependent activation of β-catenin/MITF/tyrosinase axis and Rho GTPases, highlighting its potential as a natural pigmentation enhancer.