Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Enhanced micronucleus formation and modulation of Bcl-2 : Bax in MCF-7 cells after exposure to binary mixtures.
AU - Hewitt, Rebecca
AU - Forero, Albert
AU - Luncsford, Paz J.
AU - Martin, Frank L.
PY - 2007
Y1 - 2007
N2 - Background: Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure. Methods: In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21WAF1/CIP1) ], B-cell leukemia/lymphoma 2 (BCL-2) , BCL-2–associated X (BAX) , and isoforms of cytochrome P450 (CYP) , CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21Waf1/Cip1, Bcl-2 and Bax protein expression in MCF-7 cells were also carried out. Results: After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted ; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17β-estradiol (E2) . Although treatment with B[a]P alone was found to elevate expression of P21WAF1/CIP1and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10–8 M B[a]P plus 10–12 M lindane or 10–10 M E2 reversed B[a]P-induced reductions in the ratio of Bcl-2– to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E2 resulted in profound reductions in Bcl-2:Bax ratio. Conclusions: Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.
AB - Background: Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure. Methods: In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21WAF1/CIP1) ], B-cell leukemia/lymphoma 2 (BCL-2) , BCL-2–associated X (BAX) , and isoforms of cytochrome P450 (CYP) , CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21Waf1/Cip1, Bcl-2 and Bax protein expression in MCF-7 cells were also carried out. Results: After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted ; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17β-estradiol (E2) . Although treatment with B[a]P alone was found to elevate expression of P21WAF1/CIP1and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10–8 M B[a]P plus 10–12 M lindane or 10–10 M E2 reversed B[a]P-induced reductions in the ratio of Bcl-2– to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E2 resulted in profound reductions in Bcl-2:Bax ratio. Conclusions: Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.
KW - 17β-estradiol
KW - BAX
KW - Bcl-2
KW - benzo[a]pyrene
KW - binary mixture
KW - clonogenic assay
KW - cytokinesis-block micronucleus assay
KW - lindane
KW - micronucleus
KW - PhIP.
U2 - 10.1289/ehp.9361
DO - 10.1289/ehp.9361
M3 - Journal article
VL - 115
SP - 129
EP - 136
JO - Environmental Health Perspectives
JF - Environmental Health Perspectives
SN - 0091-6765
IS - Supple
ER -