Fig. 5.

Nicotine and NNK reduce DNA-repair activity and the level of repair proteins XPC and hOGG1/2 in cultured human lung and bladder epithelial cells. Cell-free cell lysates were isolated from human lung (BEAS-2B) and bladder epithelial (UROtsa) cells treated with different concentrations of nicotine and NNK 1 h at 37 °C. The NER and the BER activity in the cell lysates were determined by the in vitro DNA damage-dependent repair synthesis assay as described in Fig. 3. (A) Ethidium bromide-stained gels (Upper) and autoradiograms (Lower) are shown. (B) Quantifications results. The radioactive counts in the autoradiograms were normalized to input DNA. The relative repair activity was calculated using the control band as 100%. (C) The effect of nicotine and NNK treatment on abundance of XPC and hOGG1/2 in human lung and bladder urothelial cells were determined as described in Fig. 3.