Hydrogen gas alleviates Lipopolysaccharide-induced Acute Lung Injury and inhibits inflammatory response

Background: The two main causes of body inflammation caused by lipopolysaccharide (LPS) -induced acute lung injury (ALI) are chronic inflammation and oxidant / antioxidant imbalances. Hydrogen (H2), a gaseous molecule without known toxicity, could react with hydroxyl radical to remove the reactive oxygen species (ROS). Both in vivo and vitro studies support the protective effect of hydrogen on injuries caused by oxidative stress and inflammations. Methods: In vivo study, mice were randomly divided into three groups: H2 control group, LPS group and LPS+H2 group. The mice were euthanized at the indicated time points and the specimens were collected. The 72h survival rates, cytokines contents, pathological changes, expression of Toll-like receptor 4(TLR4) and oxidative stress indicators were observed. In vitro study, according to different culture conditions, RAW 264.7 mouse macrophages were divided into the following groups: PBS group, LPS group and LPS+H2 group. The cell Viability, intracellular ROS, cytokines and expression of TLR4 and nuclear factor kappa-B (NF-κB) were observed. Results: In vivo, the 72h survival rate of hydrogen inhalation mice was increased to 80%, and H2 significantly lighten LPS-induced lung damages and decreased inflammatory cytokine release. Besides, H2 showed remarked anti-oxidative activity to reduce the MDA and NO contents in lung. In vitro, H2 down-regulated the levels of ROS, NO, TNF-α, IL-6 and IL-1β in LPS-stimulated macrophages. Second, H2 inhibited the expression of TLR4 and the activation of nuclear factor kappa-B (NF-κB). In summary, these findings supported that H2 attenuates LPS-induced inflammatory responses, which may be mediated by TLR4-NF-κB pathway.