ffinized and rehydrated tissue sections were permeabilized with 30 mg/ml Proteinase K for 1 h at 37uC. Then, the sections were quenched of endogenous peroxidase activity in 3% hydrogen peroxide for 10 min. After a thorough washing with 16 PBS, the sections were incubated with equilibration buffer for 10 min, and Effects of Afzelin on UVB-Induced Cell Damage 6 Effects of Afzelin on UVB-Induced Cell Damage then the TdT reaction mixture was added to the sections, except for the negative control, and incubated at 37uC for 1 h. The reaction was stopped by immersing the sections in 26 salinesodium citrate buffer for 15 min. Streptavidin-HRP was added to the sections for 30 min at room temperature, and after repeated washings, sections were incubated with substrate DAB until the color developed. The sections were mounted after rehydration and observed for TUNEL-positive cells. Mitochondrial Redox Status and Damage The JC-1 fluorescent probe was used to estimate mitochondrial membrane potential. JC-1 was added to the cells and incubated at 37uC for 30 min. The ratio of the intensity of green fluorescent monomers to the intensity of JC-1 aggregates is directly related to mitochondrial membrane potential. The levels of mitochondrial hydrogen peroxide were determined with the DHR 123 oxidant-sensitive fluorescent probe using a fluorescent fluorometer. Cells pre-loaded with 10 mM DHR123 for 30 min 7 Effects of Afzelin on UVB-Induced Cell Damage 8 Effects of Afzelin on UVB-Induced Cell Damage were exposed to UVB and were then lysed with 0.1% Triton X100. The fluorescence intensity of each lysate was measured at an excitation wavelength of 485 nm and an emission wavelength of 530 nm using a fluorometer. Cytochrome c ELISA An ELISA kit was used to quantify cytochrome c in subcellular fractions. After pretreatment with UVB, HaCaT cells were incubated for 9504387 12 h with afzelin, harvested with trypsin, centrifuged briefly at 8006g, and the supernatant was discarded. The 9751179 cell pellet was resuspended and washed with PBS. Cells were pelleted at 1,0006g for 
5 minutes, and the supernatant was discarded. The cell pellet was resuspended with Digitonin Cell Permeabilization Buffer, vortexed, and incubated on ice for 5 minutes. The cells were then centrifuged at 10006g for 5 minutes at 4uC. The supernatants were saved, as they contained the cytosolic fraction with cytochrome c. The remaining pellet was resuspended in RIPA Cell Lysis Buffer 2 ), vortexed, and incubated on ice for 5 minutes. The lysate was centrifuged at 10,0006g for 10 minutes at 4uC, and the supernatant was collected and protein was quantified. The samples were then treated with a conjugate reagent, transferred to microwell strips coated with anti-cytochrome c antibody, and incubated for 60 minutes at room temperature. The samples were then treated with a peroxidase substrate reagent and incubated for 15 minutes at room temperature. After adding a stop solution, the optical density of each well was measured at 450 nm. The cytochrome c concentration was determined from a standard curve. Fractions were run in the assay and the resulting picogram determinations were divided by the protein concentration. The resulting values are expressed as pg/mg of total protein from each fraction. solution was added. Finally, the samples were incubated in the dark, and absorbance was read at 450 nm. PGE2 TG100 115 concentrations in the supernatants were analyzed with a high sensitivity PGE2 ELISA. Culture supernatants were added
