FIGURE 2.

Arsenite inhibition of UVR-induced PARP-1 activation. A, HaCaT cells were exposed to 8 J/cm² UV radiation on ice, and then rinsed and incubated with serum-free medium for the indicated times. Subsequently, PARP-1 activity was detected by in situ immunochemical detection of poly(ADP-ribose). Results are representative of at least three experiments. B, HaCaT cells were incubated with the indicated concentrations of arsenite in serum-free medium for 24 h, then exposed to 8 J/cm² UV radiation and placed on ice. After UVR exposure, cells were rinsed and incubated with serum-free medium for 20 min, and PARP-1 activity was detected as in A. Images were obtained using an Olympus BH2-RFCA fluorescence microscope and Omegafire digital camera with MagnaFire 2.1 software and quantified as described under “Experimental Procedures.” ^*, p < 0.05 compared to UVR alone. C, HaCaT cells were incubated with the indicated concentrations of arsenite in serum-free medium for 24 h, and then exposed to UVR as described above. Cells were incubated for 20 min following UVR exposure, and cell protein extracts were assayed for PARP activity assessed using the HT Colorimetric PARP/Apoptosis Assay kit (Trevigen, Inc., Gaithersburg, MD) according to the manufacturer's instructions. NT = untreated.