TY - JOUR
T1 - In silico studies with human DNA topoisomerase-II alpha to unravel the mechanism of in vitro genotoxicity of benzene and its metabolites
AU - Pandey, Alok Kumar
AU - Gurbani, Deepak
AU - Bajpayee, Mahima
AU - Parmar, Devendra
AU - Ajmani, Subhash
AU - Dhawan, Alok
N1 - Funding Information:
Funding by Council of Scientific and Industrial Research, New Delhi under its Networked project—NWP 0034, SIP 008 and to AD (HRD-YSA-99/Project/99), MB (Senior Research Fellowship), and DG (Junior Research Fellowship) is gratefully acknowledged.
PY - 2009/2/10
Y1 - 2009/2/10
N2 - Exposure of humans to benzene present in environment may lead to adverse chronic effects-even at the genetic level. However, the mechanism of its genotoxicity is not well understood. In the present study, in vitro genotoxicity of benzene (BZ) and its major metabolites [p-benzoquinone (BQ), hydroquinone (HQ), catechol (CT), 1,2,4-benzenetriol (BT) and trans-trans muconic acid (MA)] at concentrations 0.5-50 μM, was assessed in Chinese hamster ovary (CHO) cells employing the alkaline Comet assay, cytokinesis blocked micronucleus (CBMN) assay, flow cytometric analysis of micronucleus (flow MN) and chromosome aberration (CA) test. The data revealed significant (P < 0.05) concentration-dependent response in all end points. HQ was found to be the most potent DNA damaging metabolite in the Comet assay followed by BQ > BT > CT > BZ > MA. Both CBMN and flow MN assays revealed a good correlation in their results, where BQ and MA exhibited maximum and minimum micronucleus induction respectively. Significant chromosomal aberrations were induced mainly by BQ, BT and HQ, with moderate response shown by CT and BZ and least by MA. The results demonstrated the utility of sensitive techniques like Comet assay and flow cytometry for determination of MN, to quantify in vitro genotoxicity at low levels and also suggested that partly non-repaired DNA damage could cause adverse health effects in human population exposed to benzene. In silico studies using different endpoints of genotoxicity and molecular docking studies with human topoisomerase-II alpha, a major DNA repair enzyme were also conducted. These corroborated the results obtained from the in vitro data, pointing to a direct relationship of the observed genotoxicity with the structural properties and various interactions of metabolites with the enzyme. This comprehensive study demonstrated that genotoxicity of benzene in mammalian cells is mainly due to the inhibition of topoisomerase by the metabolites.
AB - Exposure of humans to benzene present in environment may lead to adverse chronic effects-even at the genetic level. However, the mechanism of its genotoxicity is not well understood. In the present study, in vitro genotoxicity of benzene (BZ) and its major metabolites [p-benzoquinone (BQ), hydroquinone (HQ), catechol (CT), 1,2,4-benzenetriol (BT) and trans-trans muconic acid (MA)] at concentrations 0.5-50 μM, was assessed in Chinese hamster ovary (CHO) cells employing the alkaline Comet assay, cytokinesis blocked micronucleus (CBMN) assay, flow cytometric analysis of micronucleus (flow MN) and chromosome aberration (CA) test. The data revealed significant (P < 0.05) concentration-dependent response in all end points. HQ was found to be the most potent DNA damaging metabolite in the Comet assay followed by BQ > BT > CT > BZ > MA. Both CBMN and flow MN assays revealed a good correlation in their results, where BQ and MA exhibited maximum and minimum micronucleus induction respectively. Significant chromosomal aberrations were induced mainly by BQ, BT and HQ, with moderate response shown by CT and BZ and least by MA. The results demonstrated the utility of sensitive techniques like Comet assay and flow cytometry for determination of MN, to quantify in vitro genotoxicity at low levels and also suggested that partly non-repaired DNA damage could cause adverse health effects in human population exposed to benzene. In silico studies using different endpoints of genotoxicity and molecular docking studies with human topoisomerase-II alpha, a major DNA repair enzyme were also conducted. These corroborated the results obtained from the in vitro data, pointing to a direct relationship of the observed genotoxicity with the structural properties and various interactions of metabolites with the enzyme. This comprehensive study demonstrated that genotoxicity of benzene in mammalian cells is mainly due to the inhibition of topoisomerase by the metabolites.
KW - Benzene and metabolites
KW - CHO cell line
KW - Chromosomal aberration
KW - Comet assay
KW - In silico
KW - Micronucleus test
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U2 - 10.1016/j.mrfmmm.2008.11.006
DO - 10.1016/j.mrfmmm.2008.11.006
M3 - Article
C2 - 19059273
AN - SCOPUS:58549092955
SN - 0027-5107
VL - 661
SP - 57
EP - 70
JO - Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
JF - Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
IS - 1-2
ER -