ABSTRACT
Nickel compounds are carcinogenic to humans and to experimental animals. In contrast to their weak mutagenicity, they have been shown previously to increase UV-induced cytotoxicity and mutagenicity and to interfere with the repair of UV-induced DNA lesions by disrupting DNA-protein interactions involved in DNA damage recognition. In the present study we applied cisplatin, transplatin and mitomycin C to investigate whether these enhancing effects and DNA repair inhibition are also relevant for other DNA damaging agents. Nickel(II) at non-cytotoxic concentrations of 50 microM and higher caused a pronounced increase in cisplatin-, transplatin- and mitomycin C-induced cytotoxicity, which was neither due to an altered uptake of cisplatin or transplatin nor to an increase in DNA adduct formation. However, nickel(II) inhibited the repair of cisplatin- and transplatin-induced DNA lesions. In combination with transplatin, it decreased the incision frequency, indicating that the DNA damage recognition/incision step during nucleotide excision repair is affected in general by nickel(II). In support of this, concentrations as low as 10 microM nickel(II) decreased binding of the xeroderma pigmentosum complementation group A protein to a cisplatin-damaged oligonucleotide. When combined with cisplatin, the incision frequency was affected only marginally, while nickel(II) led to a marked accumulation of DNA strand breaks, indicating an inhibition of the polymerization/ligation step of the repair process. This effect may be explained by interference with the repair of DNA-DNA interstrand crosslinks induced by cisplatin. Our results suggest that nickel(II) at non-cytotoxic concentrations inhibits nucleotide excision repair and possibly crosslink repair by interference with distinct steps of the respective repair pathways.
Subject(s)
Cisplatin/toxicity , Cross-Linking Reagents/toxicity , DNA Repair/drug effects , Nickel/pharmacology , Animals , Antineoplastic Agents/pharmacokinetics , Antineoplastic Agents/toxicity , Cell Line , Cisplatin/pharmacokinetics , Cricetinae , Cross-Linking Reagents/pharmacokinetics , DNA Adducts/biosynthesis , DNA-Binding Proteins/metabolism , Dose-Response Relationship, Drug , Drug Synergism , Electrophoresis, Polyacrylamide Gel , Intracellular Fluid/metabolism , Mitomycin/toxicity , Protein Binding/drug effects , Xeroderma Pigmentosum Group A ProteinABSTRACT
The miniaturized heart-lung machine consists of commercially available roller pumps, a flexible heat exchanger, a newly devised bubble oxygenator, and polyethylene cannulas and silicone tubes. The minimum and maximal priming volume of the entire system is 4.7 and 16.7 mL, respectively. The efficiency of the system is reflected in an heat transfer coefficient ranging from 0.96 to 0.31 at flow rates between 1 and 20 mL/min, a high value of oxygen uptake in the range of 0.061 mL O2/min mL blood-1, and low blood trauma with plasma hemoglobin concentrations of 47.5 +/- 5.0 mg/dL after 60 min of in vitro perfusion. The system is a simple, reliable, and efficient miniaturized heart-lung machine for use in small animals.
