title: Gene expression in benzene-exposed workers by microarray analysis of peripheral mononuclear blood cells: induction and silencing of CYP4F3A and regulation of DNA-dependent protein kinase catalytic subunit in DNA double strand break repair.
abstract: Benzene causes hematotoxicity and leukemia in humans. To analyze benzene-caused aberrant gene expression, we examined differential gene expression by microarray analysis of peripheral mononuclear blood cells from seven workers diagnosed with benzene poisoning and seven matched controls. Twenty-two genes were found up-regulated and 18 down-regulated in benzene patients compared with controls. Here we report the characterization of two benzene-regulated genes. CYP4F3A, which encodes the leukotriene B(4) (LTB(4)) omega-hydroxylase, is important for inactivation of LTB(4) in neutrophils. CYP4F3A mRNA was found elevated in all patients; moreover, CYP4F3A mRNA and protein were induced by benzene metabolite phenol in HL-60 and K562 cells as well as ex vivo in human peripheral neutrophils. Silencing of CYP4F3A in HL-60 cells by lentiviral delivery of CYP4F3A-specific siRNA reduced cell survival to 56%, 44%, 22%, 14%, and 3% at 3, 4, 5, 6, and 7 days, respectively; the results suggest that CYP4F3A is a critical positive regulator of HL-60 proliferation. DNA-dependent protein kinase catalytic subunit (DNA-PKcs) regulates non-homologous end joining (NHEJ) in DNA double strand break (DSB) repair. DNA-PKcs mRNA was found consistently increased in the patients and DNA-PKcs mRNA and protein were induced by hydroquinone in HL-60 cells. In a DSB model, hydroquinone induced the formation of gamma-H2AX foci, a marker of DSBs, in HL-60 cells. The findings indicate that hydroquinone induces DSBs and induction correlates with elevated levels of DNA-PKcs and NHEJ. Similar results were obtained in K562 cells treated with phenol. Since NHEJ is error-prone, induction of DNA-PKcs and NHEJ may contribute to mutagenesis and leukemia by benzene. To our knowledge, the study demonstrated for the first time that benzene and metabolites induce CYP4F3A and DNA-PKcs both in vivo and in vitro. Induction of the genes may play a role in the pathogenesis of benzene hematotoxicity and serve as biomarkers of benzene exposure.
authors.affiliation: School of Public Health, Wuhan University, 185 Donghu Rd, Wuhan, Hubei 430071, China. yongyib@yahoo.com.cn
authors.forename: Yongyi
authors.initials: Y
authors.lastname: Bi
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Li
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Kong
authors.forename: Xiao
authors.initials: X
authors.lastname: Xiao
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Zhao
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: He
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ma
mesh_terms: D001554:Benzene; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D000072470:Cytochrome P450 Family 4; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D051747:DNA-Activated Protein Kinase / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D020868:Gene Silencing / Q000187:drug effects; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000378:metabolism
chemical_list: D003577:Cytochrome P-450 Enzyme System; D000072470:Cytochrome P450 Family 4; C465349:CYP4F3 protein, human; D051747:DNA-Activated Protein Kinase; D001554:Benzene