PNNL

Abstract

Gene expression changes in primary human uroepithelial cells exposed to arsenite and its methylated metabolites were evaluated to identify cell signal pathway perturbations potentially associated with bladder carcinogenicity. Cells were treated with mixtures of inorganic arsenic and its pentavalent or trivalent metabolites for 24 hours at total arsenic concentrations ranging from 0.06 [mu]M to 18 [mu]M. One series (five samples) was conducted with arsenite and pentavalent metabolites and a second (ten samples) with arsenite and trivalent metabolites. Similar gene expression responses were obtained for pentavalent or trivalent metabolites. A suite of eight gene changes was consistently identified across individuals that reflect effects on key signaling pathways: oxidative stress, protein folding, growth regulation, metallothionine regulation, DNA damage sensing, thioredoxin regulation, and immune response. No statistical significance of trend (NOSTASOT) analysis of these common genes identified lowest observed effect levels (LOELs) from 0.6 – 6.0 [mu]M total arsenic and no observed effect levels (NOELs) from 0.18 – 1.8 [mu]M total arsenic. For the trivalent arsenical mixture, benchmark doses (BMDs) ranged from 0.13– 0.92 [mu]M total arsenic; benchmark dose lower 95% confidence limits (BMDLs) ranged from 0.09 – 0.58 [mu]M total arsenic and from 0.53 – 2.7 [mu]M and 0.35– 1.7 [mu]M, respectively, for the pentavalent arsenical mixture. Both endpoints varied by a factor of three across individuals. This study is the first to examine gene expression response in primary uroepithelial cells from multiple individuals and to identify no effect levels for arsenical-induced cell signaling perturbations in normal human cells exposed to a biologically plausible concentration range.