:
Radiation-induced lung injury is characterized by an acute pneumonia phase followed by a fibrotic phase. At
the time of irradiation, a rapid, short-lived burst of reactive oxygen species (ROS) such as hydroxyl radicals (•OH) occurs,
but chronic radiation-induced lung injury may occur due to excess ROS such as H2O2
, O2•−
, ONOO−
, and •OH. Molecular
hydrogen (H2
) is an efficient antioxidant that quickly diffuses cell membranes, reduces ROS such as •OH and ONOO−
,
and suppresses damage caused by oxidative stress in various organs. In 2011, through the evaluation of electron-spin
resonance and fluorescent indicator signals, we had reported that H2 can eliminate •OH and can protect against oxidative
stress-related apoptotic damage induced by irradiation of cultured lung epithelial cells. We had explored for the first time
the radioprotective effects of H2
treatment on acute and chronic radiation-induced lung damage in mice by inhaled H2 gas
(for acute) and imbibed H2
-enriched water (for chronic). Thus, we had proposed that H2 be considered a potential
radioprotective agent. Recent publications have shown that H2 directly neutralizes highly reactive oxidants and indirectly
reduces oxidative stress by regulating the expression of various genes. By regulating gene expression, H2
functions as an
anti-inflammatory and anti-apoptotic molecule and promotes energy metabolism. The increased evidence obtained from
cultured cells or animal experiments reveal a putative place for H2
treatment and its radioprotective effect clinically. This
review focuses on major scientific advances of in the treatment of H2 as a new class of radioprotective agents.
Preclinical models of radiation-induced lung damage: challenges and opportunities for small animal radiotherapy