Tranexamic acid inhibits melanogenesis partially via stimulation of TGF-β1 expression in human epidermal keratinocytes.

BACKGROUND Oral tranexamic acid (TA) has been an effective treatment for melasma with unclear mechanism. OBJECTIVE The present study aimed to demonstrate the effect of TA on melanogenesis via regulation of TGF-β1 expression in keratinocytes. METHODS We firstly determined the expression level of TGF-β1 in TA-treated keratinocyte-conditioned medium (KCM). Then the mRNA and protein levels of microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), and tyrosinase-related protein-1 (TRP-1) of human epidermal melanocytes (NHEMs) in presence of TA-treated KCM were evaluated via RT-PCR and Western blot analysis. Moreover, melanin content and tyrosinase activity were quantified. TGF-β1 gene was knocked down by small interfering RNA (siRNA) in keratinocytes. RESULTS The mRNA and protein levels of TGF-β1 in keratinocytes were significantly increased after TA treatment. Melanin contents, tyrosinase activity, protein and mRNA levels of TYR, MITF, and TRP-1 were downregulated in NHEMs in the presence of TA-treated KCM. Knockdown of TGF-β1 in keratinocytes could attenuate the inhibitory effect of TA-treated KCM on melanogenesis. CONCLUSION TA could stimulate TGF-β1 expression in keratinocytes, which further inhibits melanogenesis through the paracrine signaling.