Nitric oxide is involved in arsenite inhibition of pyrimidine dimer excision

Abstract

Arsenite is a human carcinogen reported to inhibit DNA repair. The binding of arsenite to functional thiol groups of DNA repair enzymes has in the past been suggested as a possible mechanism for the effect of arsenite on DNA repair. However, recent studies indicate that reactive oxygen species and nitric oxide are involved in arsenite toxicity. This research aims to elucidate the role of these possible mechanisms in the inhibition of UV-induced DNA repair by arsenite. As arsenite inhibits UV-DNA repair in Chinese hamster ovary cells, and this is a commonly used cell line for UV repair experiments, we used these cells to examine the effect of arsenite on the expression of UV-irradiated reporter genes. The T4 UV endonuclease V-incorporated comet assay was used to examine specifically the effect of arsenite on pyrimidine dimer excision. We showed that inhibition of UV-DNA repair by arsenite was suppressed by nitric oxide synthase inhibitors. Arsenite increased nitric oxide production and nitric oxide generators inhibited UV-DNA repair. The involvement of nitric oxide in the inhibition of pyrimidine dimer excision by arsenite was also confirmed in human fibroblasts. Investigation into the effect of oxidant modulators did not give a clear indication that reactive oxygen species are involved in arsenite inhibition of UV-DNA repair. Phenylarsine oxide, a strong thiol-reacting agent, did not inhibit pyrimidine dimer excision and also did not increase nitric oxide production. Our results show conclusively that nitric oxide is involved in the inhibition of pyrimidine dimer excision by arsenite. Reactive oxygen species and the binding of arsenite to functional thiol groups of DNA repair enzymes do not appear to be involved.

Breast Cancer Risk and the DNA Double-Strand Break End-Joining Capacity of Nonhomologous End-Joining Genes Are Affected by BRCA1

“…The linearized DNA was subjected to phenol/ chloroform extraction, ethanol-precipitated, dissolved in sterilized water, and used to transfect cells using Lipofectamine 2000 following the procedures described by the supplier (Invitrogen). The transfectants were harvested 48 h after transfection and assayed for luciferase activity as described previously (22).…”

1α,25(OH)2-Vitamin D and a Nongenomic Vitamin D Analogue Inhibit Ultraviolet Radiation–Induced Skin Carcinogenesis

“…The increase in p53 could facilitate DNA repair (25). Because increased NO inhibits DNA repair (26,27), the 1,25 (OH) 2 D 3 -induced decrease in NO products may also contribute to better DNA repair. Photocarcinogenesis, however, is the result of chronic UVR exposure.…”

As(III) inhibits ultraviolet radiation-induced cyclobutane pyrimidine dimer repair via generation of nitric oxide in human keratinocytes

“…With respect to NER, As(III) impaired the incision step and ligation of repair patches after induction of UVR-induced DNA damage, affecting both global genome repair and transcription-coupled repair (23). CPDs are repaired primarily by NER and there is limited evidence indicating that As(III) interferes with repair of CPDs in Chinese hasmster ovary cells (24) and TK6 human lymphoblastoid cells (25), although As(III) interference with CPDs repair was not observed in mouse keratinocytes (26). Furthermore, the mechanism by which As(III) inhibits CPDs repair is unclear.…”