Age-associated changes in cellular response to (anti)-benzopyrene-7,8-diol-9,10-epoxide (BPDE) in human fibroblasts

Abstract

1196

There is considerable evidence showing that newborn and infant animals are more susceptible than adult animals to tumorigenesis induced by a broad spectrum of chemical carcinogens. The data of our previous studies have shown that freshly prepared precision-cut liver and lung slices of neonatal rats, compared to the tissue slices of adult rats, are more active in metabolizing BP to reactive metabolites resulting in greater DNA damage. In the present study, we have examined the age-associated changes in cellular response (e.g., expression of p53 and nucleotide excision repair [NER] proteins) to BPDE, an ultimate carcinogenic BP metabolite. Human dermal fibroblasts derived from one day-, one year-, and 33 year old donors were treated with 0.5 or 1 μM BPDE for 1 hr and after 16 hr, the cells were lysed and protein were extracted. Proteins were resolved by SDS-PAGE and the p53 and NER proteins (XPA, ERCC1, TFIIH p62) were detected by western immunoblotting using specific antibodies. Treatment with BPDE resulted in a dose-dependent up-regulation of p53 protein in cells from donors of different ages. However, the extent of p53 induction was lower in cells from adult donors than in cells from one day- and one year old donors, suggesting BPDE treatment causes greater damage to DNA in the cells from younger donors than in those from adult donors. The level of BPDE-DNA adducts both at 4 and 24 hr after treatment with BPDE was in the following order: one day old = one year old > 33 year old. These data are consistent with the data on the induction of p53 in these cells. The constitutive levels of NER proteins (XPA, ERCC1, TFIIH p62) were higher in one day old donor cells than in 33 year old donor cells. Interestingly, BPDE treatment caused a dose-dependent decrease in the levels of these NER proteins in cells from the one day old donor. In contrast, a slight increase in the level of NER proteins was observed in the 33 year old donor cells treated with BPDE. Since reduced DNA repair capacity is known to be associated with the reduced level of NER proteins, a decrease in the level of these proteins from the one day old donor suggests a compromised DNA repair capacity and possibly a greater susceptibility to PAH-induced carcinogenesis in newborn children than in young adults.