Hacat cells

The human keratinocyte cell line HaCaT cells were purchased from the Korean Cell Line Bank (Republic of Korea). Cells were cultured in a Dulbecco’s modified eagle media (DMEM, Lonza) containing 10% fetal bovine serum (FBS, Gibco) and 1% penicillin/streptomycin (Gibco). HaCaT cells were cultured at 37°C in a humidified incubator with 95% air condition and 5% CO₂. Before UVB irradiation, and then immediately exposed to 40 mJ/cm² of UVB radiation (312 nm, G15T8E, 15 W, Sankyo Denki, Japan). After UVB irradiation, the media was changed to serum-free media and continued to be cultured in the incubator for 24 h.

The certified reference material, CRM No. 28 (Urban aerosols), was purchased from the Centre for Environmental Measurement and Analysis, National Institute for Environmental Studies, Ibaraki, Japan. The cell lines required for the experiments, HaCaT cells, and the human dermal fibroblast (HDF) were purchased from the Korean Cell line Bank (KCLB, Seoul, Korea). Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS), and antibiotics (penicillin and streptomycin) for growth medium were purchased from the GIBCO Inc. (Grand Island, NY, USA). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was obtained from Sigma-Aldrich (St. Louis, MO, USA). Antibodies used in the Western blot analysis were from Santa Cruz Biotechnology (Santa Cruz, CA, USA). The cytokine kits used in the experiments were purchased from eBioscience (San Diego, CA, USA), R&D Systems (Minneapolis, MN, USA), BD Opteia (San Diego, CA, USA), and Invitrogen (Carlsbad, CA, USA). All the organic solvents used in the experiments were of analytical grade unless specified and were purchased from Sigma-Aldrich.

HaCaT cells were obtained from the Korean Cell Line Bank (Seoul, Korea). The cells were cultured in high-glucose Dulbecco’s modified Eagle’s medium supplemented with 10% fetal bovine serum (FBS, Gibco, NY, USA) and 1% penicillin–streptomycin (WelGENE, Daegu, Korea) in 5% CO₂ at 37 °C.