Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) in the etiology of contact vitiligo

Abstract

Phenolic and Catecholic compounds that behave as substrates of tyrosinase have been implicated in the etiology of contact vitiligo. In this study we determined the role of the commercially used phenolic antioxidants, BHT and BHA that are not substrates of tyrosinase, in the etiology of contact vitiligo. Approximately 105 darkly pigmented SK-MEL-23 and lightly pigmented SK-MEL-19 melanoma cells maintained in minimum essential media with supplements were seeded in 96-well plates. After 24 hr, cells were exposed to increasing concentrations (0–250 uM) of BHT and BHA alone and in combination. The effects on cell viability, cell proliferation rate, tyrosinase expression / activity, and melanin content were determined and compared to hydroquinone (HQ), a known melanocyte specific toxin. Increasing concentrations of BHT, BHA and HQ for up to 96 hours resulted in corresponding decreases in cell viability as determined by cell counts and trypan blue exclusion method. At 96 hours, 250 uM BHT was significantly more toxic to pigmented SK-MEL-23 as compared to lightly pigmented SK-MEL-19 melanoma cells by this assay. However BHT and BHA did not have any significant effects on cell proliferation rate as measured by CellTiter 96 Aqueous One solution cell proliferation assay kit. Moreover, BHT and BHA did not affect tyrosinase expression and activity nor melanin content in both melanoma cell lines. Thus, BHT and BHA are relatively non-toxic to both dark and lightly pigmented melanoma cells and may not be involved in etiology of contact vitiligo.