5-Ethyl-2'-deoxyuridine. Cytotoxicity and DNA incorporation demonstrated with human leukemic cells and PHA-stimulated lymphocytes in vitro

Evaluating the Genotoxic and Cytotoxic Effects of Thymidine Analogs, 5-Ethynyl-2'-Deoxyuridine and 5-Bromo-2'-Deoxyurdine to Mammalian Cells

BrdU (bromodeoxyuridine) and EdU (ethynyldeoxyuridine) have been largely utilized as the means of monitoring DNA replication and cellular division. Although BrdU induces gene and chromosomal mutations and induces sensitization to photons, EdU's effects have not been extensively studied yet. Therefore, we investigated EdU's potential cytotoxic and mutagenic effects and its related underlying mechanisms when administered to Chinese hamster ovary (CHO) wild type and DNA repair-deficient cells. EdU treatment displayed a higher cytotoxicity and genotoxicity than BrdU treatment. Cells with defective homologous recombination repair displayed a greater growth delay and severe inhibition of clonogenicity with EdU compared to wild type and other DNA repair-deficient cells. Inductions of sister chromatid exchange and hypoxanthine phosphorybosyl transferase (HPRT) mutation were observed in EdU-incorporated cells as well. Interestingly, on the other hand, EdU did not induce sensitization to photons to the same degree as BrdU. Our results demonstrate that elevated concentrations (similar to manufacturers suggested concentration; >5-10 μM) of EdU treatment were toxic to the cell cultures, particularly in cells with a defect in homologous recombination repair. Therefore, EdU should be administered with additional precautions.

An in vitro study of ophthalmic antiviral agent toxicity on rabbit corneal epithelium

Using an in vitro system we measured the corneal epithelial cytotoxicity and the antiviral activity of the antiviral agents idoxuridine (IDU), trifluridine (TFT), ethyldeoxyuridine (EDU), and (E)-5-(2-Bromovinyl)-2'-deoxyuridine (BVDU). Confluent rabbit corneal epithelial cell cultures were established, and the antiviral agents were added for 5, 30, or 60 min at a range of concentrations including that used clinically (IDU 0.1%, TFT 1.0%, BVDU 0.1%, EDU 2.0%). Twelve hour [3H]thymidine incorporation then was measured and expressed as % inhibition of control cultures. In separate experiments confluent corneal epithelial cell monolayers were inoculated with 10(4) plaque forming units (PFU) of HSV type 1 (McKrae strain) for 1 h, and IDU 0.1%, TFT 1.0%, and BVDU 0.1% were added to the culture for determination of PFU inhibition. Significant dose-, but not time-dependent, toxicity was observed at the clinical concentrations of IDU, TFT, and EDU. Toxicity was absent for BVDU. TFT and IDU were the most toxic, and EDU was of intermediate toxicity. IDU, TFT, and BVDU showed significant antiviral activity in this corneal epithelial cell culture system (TFT greater than BVDU greater than IDU). The results of this in vitro study paralleled the findings of previous in vivo corneal epithelial toxicity studies of IDU, TFT, and BVDU. Our data, however, suggest that EDU has a potential for clinical toxicity and further studies are recommended. Our model may be useful in the future toxicologic study of new antiviral agents.