3 4 5 dimethylthiazol 2 yl 2 5 diphenyltetrazolium bromide mtt α melanocyte stimulating hormone α msh

Dulbecco's modified Eagle's medium (DMEM), fetal bovine serum (FBS), penicillin and streptomycin were purchased from Gibco BRL (Carlsbad, CA, USA). OEA, kojic acid, MK886, L-DOPA, dimethyl sulfoxide (DMSO), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), α-melanocyte-stimulating hormone (α-MSH), PD98059 and PTU were purchased from Sigma-Aldrich Co. (St Louis, MO, USA). Antibodies against MC1R (1:1000, Cell Signaling Technology, Boston, USA), MITF (1:1000, Cell Signaling Technology), TRP-1 (1:1000, Cell Signaling Technology), Tyrosinase (1:1000, Cell Signaling Technology), PPARα (1:1000, Abcam, Cambridge, UK), total-ERK (1:1000, Cell Signaling Technology), phospho-ERK (Thr202/Thr204) (1:1000, Cell Signaling Technology), total-Akt (1:1000, Cell Signaling Technology), phospho-Akt (Ser473) (1:1000, Cell Signaling Technology), total-CREB (1:1000, Cell Signaling Technology), phospho-CREB (Ser133) (1:1000, Cell Signaling Technology), total-p38 (1:1000, Cell Signaling Technology), phospho-p38 (1:1000, Cell Signaling Technology) and mouse monoclonal anti-β-actin (1:10000, Sigma) were obtained from the indicated manufacturers. OEA, kojic acid, MK886, PD98059 and PTU were dissolved in dimethyl sulfoxide (DMSO), and the final DMSO concentration was less than 0.05%. L-DOPA was dissolved in phosphate buffered saline (PBS).