Both Complexity and Location of DNA Damage Contribute to Cellular Senescence Induced by Ionizing Radiation

Area of Science:

• Radiation biology
• Cellular senescence
• DNA damage and repair

Background:

• Persistent DNA damage is a known inducer of cellular senescence following ionizing radiation exposure.
• The precise molecular mechanisms linking DNA damage to senescence, particularly the differences between radiation types, require further elucidation.

Purpose of the Study:

• To compare the effectiveness of heavy ions and X-rays in inducing cellular senescence in human uveal melanoma cells.
• To investigate the characteristics of DNA damage and repair kinetics following exposure to heavy ions versus X-rays.
• To elucidate the role of persistent DNA damage in radiation-induced senescence.

Main Methods:

• Human uveal melanoma 92-1 cells were exposed to heavy ions and X-rays.
• Senescence was assessed using senescence-associated β-galactosidase staining and cell proliferation assays.
• DNA damage and repair were analyzed, focusing on the complexity and location of irreparable lesions.

Main Results:

• Heavy ions induced cellular senescence more effectively than X-rays.
• DNA damage induced by heavy ions exhibited less efficient repair and consisted of complex single and double-strand breaks.
• X-ray induced DNA damage was largely repaired within 24 hours, with remaining damage predominantly associated with telomeric DNA.

Conclusions:

• Heavy ion radiation induces complex, persistent DNA damage that is difficult to repair, driving cellular senescence.
• X-ray induced senescence is linked to persistent DNA damage preferentially located at telomeres.
• These findings offer insights into the high relative biological effectiveness of heavy ions for cancer therapy and space radiation research.