title: The effect of ATM kinase inhibition on the initial response of human dental pulp and periodontal ligament mesenchymal stem cells to ionizing radiation.
abstract: OBJECTIVE
  This study evaluates early changes in human mesenchymal stem cells (MSC) isolated from dental pulp and periodontal ligament after γ-irradiation and the effect of ataxia-telangiectasia mutated (ATM) inhibition.
  
  
  METHODS
  MSC were irradiated with 2 and 20 Gy by (60)Co. For ATM inhibition, specific inhibitor KU55933 was used. DNA damage was measured by Comet assay and γH2AX detection. Cell cycle distribution and proteins responding to DNA damage were analyzed 2-72 h after the irradiation.
  
  
  RESULTS
  The irradiation of MSC causes an increase in γH2AX; the phosphorylation was ATM-dependent. Irradiation activates ATM kinase, and the level of p53 protein is increased due to its phosphorylation on serine15. While this phosphorylation of p53 is ATM-dependent in MSC, the increase in p53 was not prevented by ATM inhibition. A similar trend was observed for Chk1 and Chk2. The increase in p21 is greater without ATM inhibition. ATM inhibition also does not fully abrogate the accumulation of irradiated MSC in the G2-phase of the cell-cycle.
  
  
  CONCLUSIONS
  In irradiated MSC, double-strand breaks are tagged quickly by γH2AX in an ATM-dependent manner. Although phosphorylations of p53(ser15), Chk1(ser345) and Chk2(thr68) are ATM-dependent, the overall amount of these proteins increases when ATM is inhibited. In both types of MSC, ATM-independent mechanisms for cell-cycle arrest in the G2-phase are triggered.
authors: Department of Medical Biochemistry, Faculty of Medicine in Hradec Kralove,Charles University in Prague, Czech Republic. cmielovaj@lfhk.cuni.cz
authors: Jana
authors: J
authors: Cmielova
authors: Radim
authors: R
authors: Havelek
authors: Renata
authors: R
authors: Kohlerova
authors: Tomas
authors: T
authors: Soukup
authors: Lenka
authors: L
authors: Bruckova
authors: Jakub
authors: J
authors: Suchanek
authors: Jirina
authors: J
authors: Vavrova
authors: Jaroslav
authors: J
authors: Mokry
authors: Martina
authors: M
authors: Rezacova
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors*; D003782:Dental Pulp / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D010513:Periodontal Ligament / Q000166:cytology* / Q000502:physiology / Q000528:radiation effects*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011829:Radiation Dosage; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases