Culture Collection (USA) and maintained in Dulbecco's modified Eagle's medium (DMEM;
Gibco BRL, USA) supplemented with 10% fetal bovine serum (FBS; Gibco BRL) and 100
µg/mL penicillin-streptomycin at 37°C in a humidified atmosphere containing 5%
CO2. Cells were seeded on six-well culture plates at an initial density
of 1×105 cells/mL and grown to approximately 80% confluence. For treatment
with 6-gingerol, MG-63 cells were pretreated with 1% FBS DMEM for 16 h, and then
treated with TNF-α (10 ng/mL) followed by exposure to 6-gingerol (Sigma, USA) with
serial concentrations (0-50 µM) in serum-free DMEM for 24 or 48 h. After the
6-gingerol treatment, the cells were washed with phosphate-buffered saline (PBS; 25
mM sodium phosphate, 150 mM NaCl, pH 7.2) and collected for the following
analyses.