*2.1. Reagents and Antibodies*

Ectoine (Product no: 81619, purity ≥ 95%) was purchased from Sigma-Aldrich (Taufkichen, Germany). Fetal bovine serum (FBS), penicillin/streptomycin, Dulbecco's modified Eagle's medium (DMEM) and l-glutamine were bought from Invitrogen/Gibco BRL (Carlsbad, CA, USA). l-DOPA, melanin, 3-4,5-dimethyl-2-yl-2,5-diphenyl tetrazolium bromide (MTT), and α-MSH were procured from Sigma Chemical Co (St. Louis, MO, USA). *N*-acetylcysteine (NAC) and 2,7-dichlorofluorescein-diacetate (DCFH2-DA) were procured from Sigma-Aldrich (St. Louis, MO, USA). All pharmacological inhibitors required for JNK (SP600125), ERK1/2 (PD98059), p38 (SB203580), PKC (GF109203X), and CKII were obtained from Calbiochem (La Jolla, CA, USA) PI3K/AKT inhibitor (LY294002) was obtained from Sigma-Aldrich (St. Louis, MO, USA). All antibodies for POMC, CREB, β-actin, tyrosinase, Nrf2, p-CREB, NQO-1, PKC, Kelch-like ECH-associated protein-1 (Keap-1), and TRP-1, TRP-2 were obtained from Santa Cruz Biotechnology Inc. (Heidelberg, Germany). Antibodies against γ-GCLC and HO-1 were procured from Gene Tex Inc. (San Antonio, TX, USA). We obtained antibodies against c-AMP protein kinase and CKII from Abcam (Cambridge, MA, USA). Histones, MITF, p-p38, p38, p-AKT, and AKT were obtained from Cell Signal Technology (Beverly, MA, USA). Enhanced chemiluminescence (ECL) detection reagents were obtained from Millipore, (Billerica, MA, USA). All other reagents (at HPLC grade) were either purchased from Sigma-Aldrich or Merck & Co., Inc. (Darmstadt, Germany).
