MiR-21 is continually elevated long-term in the brain after exposure to ionizing radiation

Area of Science:

• Neuroscience
• Radiation Biology
• Molecular Biology

Background:

• Ionizing radiation is known to stimulate microRNA-21 (miR-21) expression in cultured mammalian cells.
• The effect of radiation on miR-21 expression in brain cells and its long-term persistence remains largely uncharacterized.

Purpose of the Study:

• To investigate the impact of different types of radiation on miR-21 expression in mouse hippocampal cells and brain tissue.
• To determine the duration of miR-21 upregulation following radiation exposure.
• To explore the relationship between miR-21 and Epidermal Growth Factor Receptor (EGFR) in the irradiated brain.

Main Methods:

• Mice were exposed to whole-body X rays (low linear energy transfer, LET) or (56)Fe ions (high LET) at 0.5 Gy.
• miR-21 levels in hippocampal cells and brain tissue were measured at various time points up to 1 year post-irradiation.
• EGFR expression was also assessed in irradiated brain tissue.

Main Results:

• Radiation exposure stimulated miR-21 expression in mouse hippocampal cells.
• miR-21 levels gradually increased within 1 year after irradiation, irrespective of radiation LET.
• Elevated miR-21 expression in the brain correlated with increased EGFR expression, suggesting a positive regulatory loop.

Conclusions:

• Radiation induces sustained miR-21 upregulation in the mouse brain.
• A positive feedback loop exists between EGFR and miR-21 in irradiated brain tissue.
• Investigating miR-21 and its targets could provide novel approaches to understanding radiation-induced brain pathologies.