Hydrogen therapy attenuates irradiation-induced lung damage by reducing oxidative stress

Abstract

Molecular hydrogen (H2) is an efficient antioxidant that diffuses rapidly across cell membranes, reduces reactive oxygen species (ROS), such as hydroxyl radicals and peroxynitrite, and suppresses oxidative stress-induced injury in several organs. ROS have been implicated in radiation-induced damage to lungs. Because prompt elimination of irradiation-induced ROS should protect lung tissue from damaging effects of irradiation, we investigated the possibility that H2 could serve as a radioprotector in the lung. Cells of the human lung epithelial cell line A549 received 10 Gy irradiation with or without H2 treatment via H2-rich PBS or medium. We studied the possible radioprotective effects of H2 by analyzing ROS and cell damage. Also, C57BL/6J female mice received 15 Gy irradiation to the thorax. Treatment groups inhaled 3% H2 gas and drank H2-enriched water. We evaluated acute and late-irradiation lung damage after H2 treatment. H2 reduced the amount of irradiation-induced ROS in A549 cells, as shown by electron spin resonance and fluorescent indicator signals. H2 also reduced cell damage, measured as levels of oxidative stress and apoptotic markers, and improved cell viability. Within 1 wk after whole thorax irradiation, immunohistochemistry and immunoblotting showed that H2 treatment reduced oxidative stress and apoptosis, measures of acute damage, in the lungs of mice. At 5 mo after irradiation, chest computed tomography, Ashcroft scores, and type III collagen deposition demonstrated that H2 treatment reduced lung fibrosis (late damage). This study thus demonstrated that H2 treatment is valuable for protection against irradiation lung damage with no known toxicity.