Table 1.

Mechanisms and phenomena of radioadaptive response/radiation hormesis.

Level	Mechanism/Phenomenon
Molecular	Increase in antioxidative function - Induction of antioxidant enzymes like superoxide dismutase and catalase - Increase in glutathione and thioredoxin levels
	Increase in repair capacity - Increase in DNA repair enzymes - Activation of poly(ADP-ribose) polymerase
	Induction of protein synthesis - Expression of tumor suppressor gene p53 - Induction of stress proteins like HSP70
	Intensification of cellular membrane structure and function - Decrease in lipid peroxides - Increase in membrane fluidity - Increase in Na+/K+-ATPase activity
Cellular	Induction of adaptive response - Increase in cellular proliferation - Decrease in chromosome aberration
	Increase in immunological activity - Increase in blast transformation and cytokine production - Elimination of damaged cells by apoptosis - Apoptosis of lymphocytes
	Radioprotective bystander effects - Transmission of signaling molecules through gap junction - Interaction of factors secreted from irradiated cells - Association of protein kinase C, phospholipase C, nitric oxide, reactive oxygen species, etc.
	Endocrine response - Release of glucocorticoids