Abstract B41: Depleted uranium-induced oxidative stress in human bronchial epithelial cells

Cancer and mortality rates are on the rise in many populations exposed to high deposits of uranium or tailings. There is an increased concern over environmental exposure to abandoned uranium mine tailings as well as occupational exposures to depleted uranium via military action. Cellular oxidative stress has been implicated in the genotoxicity of many heavy metals. The aim of this study is to evaluate the toxicity of depleted uranium (DU) in its soluble and insoluble forms in human bronchial epithelial cells (16HBE14o⁻). 16HBE14o⁻ cells were exposed to 30 ppb of soluble depleted uranium (uranyl acetate - UA) and insoluble depleted uranium (uranium trioxide - UO₃, uranium dioxide - UO₂, uranium oxide - U₃O₈) for 2 – 24 hr. Oxidative stress was assessed in vitro by 5(6)-carboxy-2′,7′ − dichlorofluorescein diacetate (H₂DCFDA) staining and visualized by live cell fluorescent microscopy and flow cytometry. DNA damage response was assessed in vitro via Western immunoblotting to determine phosphorylation of histone H2AX and RPA levels. Results indicate that 16HBE14o⁻ cells treated with UA and UO₃ induced oxidative stress compared to untreated cells at 3 – 4 hr time points. 16HBE14o⁻ cells treated with UA and UO₃ induced phosphorylation of histone H2AX. These results are consistent with previous studies that indicate DU induces DNA damage via strand breaks and uranium-DNA adducts in treated cells. Interestingly, there was no increase in RPA phosphorylation levels of DU treated cells compared to untreated cells. These results suggest that: (1) cellular oxidative stress may be a pathway of particulate DU genotoxicity, and (2) induced DNA damage by DU may activate base excision repair in vitro. We are currently examining additional DNA repair targets to better understand the DNA repair pathway(s) stimulated by exposure to DU.