Historically, hydrogen (H2) was considered inert and nonfunctional. A study found that H2 could act as a therapeutic antioxidant by selectively reducing cytotoxic ROS/RNS. We now know that H2 can act as a cytoprotective anti-oxidation agent in isolated cells in culture. H2 acts by reducing the most reactive ROS and RNS oxidants, hydroxyl radical (•OH) and peroxynitrite (ONOO− ), but not the most plentiful ROS and RNS oxidants, hydrogen peroxide (H2O2) and nitric oxide (NO), in cells and tissues. Thus H2 can reduce oxidative stress and readjust the redox status of cells. As a result of its mild but efficient antioxidant properties, H2 can cause multiple effects in cells and tissues, including anti-apoptosis, anti-inflammation, anti-allergic and metabolic effects, in most cases by reducing oxidative stress and excess amounts of ROS/RNS.
Hydrogen can also affect gene regulation that is modified or initiated by ROS/RNS, such as gene regulation by p53, AP-1 and NF-κB. Hydrogen has the ability to modify signal transduction. Using a rat liver DNA microarray the effects of hydrogen were examined on general gene expression. After drinking H2- enriched water for 4 weeks, the DNA microarray was used to show that 548 genes were up-regulated and 695 genes were down-regulated in hepatic liver gene microarray. The genes encoding oxidoreduction proteins were enriched in the up-regulated genes. Thus hydrogen can have both specific and general effects on cells and tissues.