[Effects of hydrogen on lung injury in wild-type and Nrf2 gene knockout mice: relationship with Nrf2/HO-1/HMGB1 pathway].

Objective To investigate the key role of nuclear factor E2-related factor 2 (Nrf 2) in the treatment of lung injury in sepsis mice by regulating Nrf 2/heme oxygenase-1 (HO-1)/high mobility group protein B1 (HMGB1) pathway. Methods 120 male wild type (WT) and 120 Nrf 2 knockout (Nrf 2-KO) ICR mice were randomly divided into Sham group, H2 control group (Sham+H2 group), cecal ligation and puncture (CLP) induced sepsis model group (CLP group) and H2 intervention group (CLP+H2 group), with 30 mice in each group. The sepsis model was reproduced by CLP. The same operation was done in Sham group and Sham+H2 group except CLP. The mice in Sham+H2 group and CLP+H2 group were challenged by 2% H2 for 1 hour at 1 hour and 6 hours after operation respectively, while the mice in Sham group and CLP group only inhaled air. Twenty mice in each group were collected to observe the 7-day survival. The other mice were sacrificed at 24 hours after the reproduction of model, and the lung tissues were harvested. The activities of superoxide dismutase (SOD) and catalase (CAT) and malondialdehyde (MDA) contents were determined by enzyme-linked immunosorbent assay (ELISA). The expressions of HO-1 and HMGB1 were determined by Western Blot, and the positive expression of HO-1 was also detected by immunofluorescence. Results Compared with Sham groups, the 7-day survival rates of WT and Nrf 2-KO mice in CLP groups were significantly lowered [WT: 0% (0/20) vs. 100% (20/20), Nrf 2-KO: 0% (0/20) vs. 100% (0/20), both P 0.05]. In WT mice, compared with Sham group, the activities of SOD and CAT in lung tissue of CLP group were decreased significantly [SOD (kU/g): 131.30±28.21 vs. 251.00±22.84, CAT (kU/g): 13.43±1.52 vs. 20.76±1.63, both P 0.05). There was no significant difference in above parameters between CLP+H2 group and CLP group. Conclusions H2 inhibits lung injury in septic mice through Nrf 2/HO-1/HMGB1 pathway. Nrf 2 plays a major role in the treatment of septic lung injury by H2. Key words: Lung injury; Sepsis; Hydrogen; Nuclear factor E2-related factor 2 gene knockout