Project Summary (2005-2010)

Low-level exposure (1-50 ppb) arsenic causes a multitude of toxic effects. The new drinking water standard for arsenic (10 ppb) is based on the occurrence of bladder cancer. The mechanism(s) by which arsenic produces bladder cancer are unknown. Additionally the toxic effects of low-level arsenic exposure to produce bladder injury have not been adequately examined. Dr. Gandolfi’s studies examine mechanisms of low-level arsenic exposure to bladder tissue. An immortalized human epithelial cell line (UTOtsa) is the primary model system. In preliminary studies UROtsa cells were shown to be capable of biotransforming inorganic arsenic to more toxic methylated metabolites and low-level (1-50 ppb) arsenic chemical species were cytotoxic to the cells. The researchers’ objectives are to:

1. Determine the role of biotransformation of arsenic in bladder to produce sub-cytotoxic effects. The biotransformation of inorganic arsenic is manipulated to determine which arsenic metabolite is the ultimate toxicant.
2. Determine if the low-level arsenic exposure to the bladder is producing toxicity via proteotoxic mechanisms. This study examines if arsenic species produce toxic effects via direct interaction with critical sulfhydryl targets.
3. Determine if the low-level arsenic exposure to the bladder produces toxicity via an oxidative stress mechanism. The production of reactive oxygen species and the ensuing toxic effects are being profiled for various arsenic chemical species.
4. Determine if the low-level arsenic exposure to the bladder is affecting the ubiquitin pathway and its toxic consequences. Arsenic has been shown to alter the processing of proteins in a cell. The researchers’ studies show low-level arsenic to cause an accumulation of ubiquinated proteins. Their studies characterize this accumulation, identify if specific proteins are accumulated, and determine the impact of these accumulated proteins on cell viability.
5. Determine if biomarkers of arsenic toxicity to the bladder result from the preceding studies. Bladder samples from surgical patients are used for in vitro toxicity studies with arsenic to determine if the researchers see similar effects to those seen with the cells and if the potential biomarkers are present (ubiquinated proteins). Overall, these studies clarify the toxic effects of low-level arsenic in a human bladder model and provide potential biomarkers for arsenic-induced bladder injury.