Deletion and single nucleotide substitution at G:C in the kidney of gpt delta transgenic mice after ferric nitrilotriacetate treatment

Abstract

An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces oxidative renal proximal tubular damage that subsequently leads to a high incidence of renal cell carcinoma in rodents, presenting an intriguing model of free radical-induced carcinogenesis. In the present study, we used gpt delta transgenic mice, which allow efficient detection of point mutations and deletions in vivo, to evaluate the mutation spectra, in association with the formation of 8-oxoguanine and acroleinmodified adenine during the first 3 weeks of carcinogenesis. Immunohistochemical analysis revealed the highest levels of 8-oxoguanine and acrolein-modifed adenine in the renal proximal tubules after 1 week of repeated administration. DNA immunoprecipitation and quantitative polymerase chain reaction analysis showed that the relative abundance of 8-oxoguanine and acroleinmodified adenine at the gpt reporter gene were increased at the first week in the kidney. Similarly, in both 6-thioguanine and Spi -selections performed on the renal specimens after Fe-NTA administration, the mutant frequencies were increased in the Fe-NTAtreated mice at the first week. Further analyzes of 79 mutant clones and 93 positive plaques showed a high frequency of G:C pairs as preferred targets for point mutation, notably G:C to C:G transversion-type mutation followed by deletion, and of largesize (>1 kilobase) deletions with short homologous sequences in proximity to repeated sequences at the junctions. The results demonstrate that the iron-based Fenton reaction is mutagenic in vivo in the renal tubular cells and induces characteristic mutations.

Iron and cancer: more ore to be mined

“…Direct analysis of chromatin from the kidneys of rats treated with FeNTA revealed the presence of 8-hydroxy-2′-deoxyguanosine (8-OH-dG) and other modified DNA bases that are hallmarks of oxidatively damaged DNA 142 . When the mutation range induced by FeNTA in vivo was evaluated, transversions, substitutions and deletions were identified, as well as the loss of CDK inhibitor 2A ( Cdkn2a ; which encodes the tumour suppressors ARF and INK4A) 143,144 . High-resolution microarray comparative genomic hybridization of renal tumours that were induced by FeNTA in rats revealed extensive genomic alterations, including amplifications and deletions, with Met amplification and Cdkn2a and Cdkn2b deletion being the most common alterations 145 .…”

Molecular mechanisms of oxidative stress‐induced carcinogenesis: From epidemiology to oxygenomics

“…At an early stage of this rat carcinogenesis model, increased numbers of oxidatively modified DNA bases including 8‐oxoguanine79, 80 and a major lipid peroxidation product, 4‐hydroxy‐2‐nonenal, and its modified proteins81–84 are observed. We recently showed using gpt delta transgenic mice that deletion and single nucleotide substitutions at G:C sites are the preferred mutations in the kidney after Fe‐NTA administration85.…”

Proteomics-based safety evaluation of multi-walled carbon nanotubes

“…In fact, the carcinogenic potency of asbestos is increased by iron, which accelerates the generation of oxygen radical species (Gulumian and van Wyk, 1987;Jiang et al, 2006). Recently, we have proposed a proteomics-based method to evaluate the safety of nanomaterials (Haniu et al, 2009).…”