Activation of Hif1α by the prolylhydroxylase inhibitor dimethyoxalyglycine decreases radiosensitivity.
Hypoxia inducible factor 1α (Hif1α) is a stress responsive transcription factor, which regulates the expression of genes required for adaption to hypoxia. Hif1α is normally hydroxylated by an oxygen-dependent prolylhydroxylase, leading to degradation and clearance of Hif1α from the cell. Under hypoxic conditions, the activity of the prolylhydroxylase is reduced and Hif1α accumulates. Hif1α is also constitutively expressed in tumor cells, where it is associated with resistance to ionizing radiation. Activation of the Hif1α transcriptional regulatory pathway may therefore function to protect normal cells from DNA damage caused by ionizing radiation. Here, we utilized the prolylhydroxylase inhibitor dimethyloxalylglycine (DMOG) to elevate Hif1α levels in mouse embryonic fibroblasts (MEFs) to determine if DMOG could function as a radioprotector. The results demonstrate that DMOG increased Hif1α protein levels and decreased the sensitivity of MEFs to ionizing radiation. Further, the ability of DMOG to function as a radioprotector required Hif1α, indicating a key role for Hif1α's transcriptional activity. DMOG also induced the Hif1α -dependent accumulation of several DNA damage response proteins, including CHD4 and MTA3 (sub-units of the NuRD deacetylase complex) and the Suv39h1 histone H3 methyltransferase. Depletion of Suv39h1, but not CHD4 or MTA3, reduced the ability of DMOG to protect cells from radiation damage, implicating increased histone H3 methylation in the radioprotection of cells. Finally, treatment of mice with DMOG prior to total body irradiation resulted in significant radioprotection of the mice, demonstrating the utility of DMOG and related prolylhydroxylase inhibitors to protect whole organisms from ionizing radiation. Activation of Hif1α through prolylhydroxylase inhibition therefore identifies a new pathway for the development of novel radiation protectors.
Division of Genomic Stability and DNA Repair, Department of Radiation Oncology, Dana-Farber Cancer Institutes, Harvard Medical School, Boston, Massachusetts, United States of America.
Marina K
MK
Ayrapetov
Chang
C
Xu
Yingli
Y
Sun
Kaya
K
Zhu
Kalindi
K
Parmar
Alan D
AD
D'Andrea
Brendan D
BD
Price
D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology*; D000818:Animals; D001324:Autoantigens / Q000235:genetics; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D057809:HEK293 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex / Q000235:genetics; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects* / Q000235:genetics; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
D000600:Amino Acids, Dicarboxylic; D001324:Autoantigens; C115323:CHD4 protein, human; D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C486657:MTA3 protein, human; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D011837:Radiation-Protective Agents; D011393:Procollagen-Proline Dioxygenase; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex; C040947:oxalylglycine