A) PARP-1 activity restoration by scavenging peroxynitrite. HEKn cells were treated by 10 μM SIN-1 (peroxynitrite donor), 1 μM AsIII, or co-treated with 100 μM Uric Acid for 24 h. PARP-1 activity was then measured as described in the methods section. Scavenging peroxynitrite significantly rescued AsIII-inhibited PARP-1 activity. Bar charts show mean ± SD. *, p < 0.05, n = 3. B) Scavenging peroxynitrite restored AsIII-induced zinc loss on PARP-1 protein. HEKn cells were treated as described in panel A. Zinc content in PARP-1 protein was then measured as described in the methods section. Scavenging peroxynitrite restored zinc loss induced by AsIII. *, p < 0.05, n = 3.