Lead facilitates foci formation in a Balb/c-3T3 two-step cell transformation model: role of Ape1 function

• Published in: Environmental science and pollution research international 2018-04, Vol.25 (12), p.12150-12158
• Main Authors: Hernández-Franco, Pablo, Silva, Martín, Franco, Rodrigo, Valverde, Mahara, Rojas, Emilio
• Format: Article
• Language: English
• Subjects: 12-O-Tetradecanoylphorbol-13-acetate; Animals; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; BALB 3T3 Cells; Base excision repair; Bioassays; Cancer; carcinogenicity; Carcinogens; Carcinogens, Environmental - toxicity; Cell Proliferation - drug effects; Cell Survival - drug effects; Cell Transformation, Neoplastic - drug effects; chromosomal instability; Chronic exposure; Comet Assay; Damage accumulation; Damage detection; Deoxyribonucleic acid; DNA; DNA Damage; DNA repair; DNA-(Apurinic or Apyrimidinic Site) Lyase - biosynthesis; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; enzymes; Exposure; Gene expression; Gene Expression - drug effects; Genetic transformation; Genomic instability; Humans; lead; Lead - toxicity; lead acetate; Low concentrations; Methylnitronitrosoguanidine - pharmacology; Mice; mitogenesis; Models, Biological; N-methyl-N-nitrosoguanidine; Pretreatment; protein synthesis; Repair; Research Article; Stability; Tetradecanoylphorbol Acetate - pharmacology; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-018-1396-5

Several possible mechanisms have been examined to gain an understanding on the carcinogenic properties of lead, which include among others, mitogenesis, alteration of gene expression, oxidative damage, and inhibition of DNA repair. The aim of the present study was to explore if low concentrations of lead, relevant for human exposure, interfere with Ape1 function, a base excision repair enzyme, and its role in cell transformation in Balb/c-3T3. Lead acetate 5 and 30 μM induced APE1 mRNA and upregulation of protein expression. This increase in mRNA expression is consistent throughout the chronic exposure. Additionally, we also found an impaired function of Ape1 through molecular beacon-based assay. To evaluate the impact of lead on foci formation, a Balb/c-3T3 two-step transformation model was used. Balb/c-3T3 cells were pretreated 1 week with low concentrations of lead before induction of transformation with n-methyl-n-nitrosoguanidine (MNNG) (0.5 μg/mL) and 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.1 μg/mL) (a classical two-step protocol). Morphological cell transformation increased in response to lead pretreatment that was paralleled with an increase in Ape1 mRNA and protein overexpression and an impairment of Ape1 activity and correlating with foci number. In addition, we found that lead pretreatment and MNNG (transformation initiator) increased DNA damage, determined by comet assay. Our data suggest that low lead concentrations (5, 30 μM) could play a facilitating role in cellular transformation, probably through the impaired function of housekeeping genes such as Ape1, leading to DNA damage accumulation and chromosomal instability, one of the most important hallmarks of cancer induced by chronic exposures.