title: Decreasing peroxiredoxin II expression decreases glutathione, alters cell cycle distribution, and sensitizes glioma cells to ionizing radiation and H(2)O(2).
abstract: Glioblastomas are notorious for their resistance to ionizing radiation and chemotherapy. We hypothesize that this resistance to ionizing radiation is due, in part, to alterations in antioxidant enzymes. Here, we show that rat and human glioma cells overexpress the antioxidant enzyme peroxiredoxin II (Prx II). Glioma cells in which Prx II is decreased using shRNA exhibit increased hyperoxidation of the remaining cellular Prxs, suggesting that the redox environment is more oxidizing. Of interest, decreasing Prx II does not alter other antioxidant enzymes (i.e., catalase, GPx, Prx I, Prx III, CuZnSOD, and MnSOD). Analysis of the redox environment revealed that decreasing Prx II increased intracellular reactive oxygen species in 36B10 cells; extracellular levels of H(2)O(2) were also increased in both C6 and 36B10 cells. Treatment with H(2)O(2) led to a further elevation in intracellular reactive oxygen species in cells where Prx II was decreased. Decreasing Prx II expression in glioma cells also reduced clonogenic cell survival following exposure to ionizing radiation and H(2)O(2). Furthermore, lowering Prx II expression decreased intracellular glutathione and resulted in a significant decline in glutathione reductase activity, suggesting a possible mechanism for the observed increased sensitivity to oxidative insults. Additionally, decreasing Prx II expression increased cell cycle doubling times, with fewer cells distributed to S phase in C6 glioma cells and more cells redistributed to the most radiosensitive phase of the cell cycle, G2/M, in 36B10 glioma cells. These findings support the hypothesis that inhibiting Prx II sensitizes glioma cells to oxidative stress, presenting Prxs as potential therapeutic targets.
authors: Department of Radiation Oncology and Brain Tumor Center of Excellence, Comprehensive Cancer Center, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
authors: Pameeka S
authors: PS
authors: Smith-Pearson
authors: Mitra
authors: M
authors: Kooshki
authors: Douglas R
authors: DR
authors: Spitz
authors: Leslie B
authors: LB
authors: Poole
authors: Weiling
authors: W
authors: Zhao
authors: Mike E
authors: ME
authors: Robbins
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D005910:Glioma / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects; D018384:Oxidative Stress / Q000502:physiology*; D054464:Peroxiredoxins / Q000378:metabolism*; D011836:Radiation Tolerance / Q000502:physiology*; D011839:Radiation, Ionizing; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000528:radiation effects
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D054464:Peroxiredoxins; D005978:Glutathione