title: Epigenetic changes in p21 expression in renal cells after exposure to bromate.
abstract: This study tested the hypothesis that bromate (KBrO3)-induced renal cell death is mediated by epigenetic mechanisms. Global DNA methylation, as assessed by 5-methylcytosine staining, was not changed in normal rat kidney cells treated with acute cytotoxic doses of KBrO3 (100 and 200 ppm), as compared with controls. However, KBrO3 treatment did increase p38, p53 and histone 2AX (H2AX) phosphorylation, and p21 expression. Treatment of cells with inhibitors of DNA methyltransferase (5-azacytidine or 5-Aza) and histone deacetylase (trichostatin A or TSA) in addition to KBrO3 increased cytotoxicity, as compared with cells exposed to KBrO3 alone. 5-Aza and TSA co-treatment did not alter p38 or p53 phosphorylation, but slightly decreased H2AX phosphorylation and significantly decreased p21 expression. We also assessed epigenetic changes in cells treated under sub-chronic conditions with environmentally relevant concentrations of KBrO3. Under these conditions (0-10ppm KBrO3 for up to 18 days), we detected no increases in cell death or DNA damage. In contrast, slight alterations were detected in the phosphorylation of H2AX, p38, and p53. Sub-chronic low-dose KBrO3 treatment also induced a biphasic response in p21 expression, with lower concentrations increasing expression, but higher concentrations decreasing expression. Methylation-specific PCR demonstrated that sub-chronic KBrO3 treatment altered the methylation of cytosine bases in the p21 gene, as compared with controls, correlating to alterations in p21 protein expression. Collectively, these data show the novel finding that KBrO3-induced renal cell death is altered by inhibitors of epigenetic modifying enzymes and that KBrO3 itself induces epigenetic changes in the p21 gene.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, 30602, Georgia.
authors.forename: N E
authors.initials: NE
authors.lastname: Scholpa
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, 30602, Georgia.
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, 30602, Georgia.
authors.forename: R T
authors.initials: RT
authors.lastname: Kolli
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, 30602, Georgia bsc@rx.uga.edu.
authors.forename: B S
authors.initials: BS
authors.lastname: Cummings
mesh_terms: D000818:Animals; D001959:Bromates / Q000633:toxicity*; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics* / Q000378:metabolism; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D044127:Epigenesis, Genetic / Q000187:drug effects*; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D056572:Histone Deacetylase Inhibitors / Q000633:toxicity; D006657:Histones / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D001959:Bromates; C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D016159:Tumor Suppressor Protein p53; C019536:potassium bromate; D015254:DNA Modification Methylases; D048051:p38 Mitogen-Activated Protein Kinases
keywords: bromate; epigenetics; kidney; nephrotoxicity; p21; water disinfection byproducts