Research Project 2
Oxidative Stress and PCB Exposure in Mammalian Cells
In recent years, it has been suggested that oxidative stress could contribute to biological effects of polychlorinated biphenyl (PCB) exposures. During the previous period of support researchers used in vitro cultures of human non-malignant breast (MCF10A) and prostate (RWPE-1) epithelial cells to determine the cellular effects of PCB 3, PCB 77, PCB 153, Aroclor 1254, and 2-(4-chlorophenyl)benzo-1,4-quinone (4-CI-BQ, a metabolite of PCB 3). 4-CI-BQ and PCB 153 (3 pM, 3-5 d) significantly increased mitochondria-generated reactive oxygen species (ROS) levels resulting in DNA damage, changes in MnSOD activity and cyclin DI protein levels, inhibition in cell proliferation, and increased cytotoxicity. Antioxidant-treatment of cells prior to and following the PCB treatment ameliorated these effects. Interestingly, 1 micro molar of PCB 153 treatment decreased cyclin DI protein turnover, while higher concentrations (3-20 micro molar) enhancedcyclin DI degradation. This biphasic response of PCB 153 was associated with a small increase in cell number for the lower concentrations, and inhibition in cell proliferation for the higher concentrations. PCB 153-induced changes in cyclin DI protein levels were also associated with changes in pyruvate kinase and hexokinase II protein levels.
These results led Dr. Goswami to hypothesize that redox signaling mediated by ROS (O2 and H2O2) disrupts coordinate regulation of SOD2 and cyclin DI expression, which contributes to both stimulatory and cytostatic effects of PCBs on cellular proliferation. The aims for the 2010-15 project are to:
Aim 1: Determine if PCB-induced ROS-signaling perturbs transitions between quiescent (Go) and proliferative (Gi, S, G2, and M) growth in human epithelial (breast and lung), and lung fibroblasts cultured in vitro.
Aim 2: Determine the mechanisms regulating S0D2 activity in PCB-treated quiescent and proliferating epithelial and fibroblast cells cultured In vitro.
Aim 3: Determine the mechanisms regulating cyclin DI protein levels in PCB-treated epithelial and fibroblast cells cultured in vitro.
Aim 4: Determine whether loss of SOD2 expression perturbs PCB-induced alterations in cyclin DI expressions in vivo in breast, liver, and lung tissues of C57BL/6 Floxed S0D2 mice. Determine if application of small molecular weight antioxidants could suppress these effects.
Project Leader: Douglas R. Spitz, PhD
Dr. Spitz, the University of Iowa, is a well-established investigator in the field of Free Radical Cancer Biology and Radiation Biology. He is responsible for the overall direction of the project including experimental design, data interpretation, manuscript preparation, and supervision of all personnel involved with the studies.
Co-Project Leader: Prabhat C. Goswami, PhD
Dr. Goswami supervises and collaborates on all the experiments designed to determine if alterations in cell cycle checkpoints and redistribution contribute to the biological effects of PCBs. Dr. Goswami is a recognized expert on cell cycle regulation and the role of redox changes in cell cycle regulation.
Co-Project Leader: Frederick Domann, PhD
Professor, Radiation Oncology, The University of Iowa