We recently demonstrated the inhalation of hydrogen gas, a novel medical therapeutic gas, ameliorates ventilator-induced lung injury (VILI); however, the molecular mechanisms by which hydrogen ameliorates VILE remain unclear. Therefore, we investigated whether inhaled hydrogen gas modulates the nuclear factor-kappa B (NF kappa B) signaling pathway. VILI was generated in male C57BL6 mice by performing a tracheostomy and placing the mice on a mechanical ventilator (tidal volume of 30 ml/kg or W ml/kg without positive end-expiratory pressure). The ventilator delivered either 2% nitrogen or 2% hydrogen in balanced air. NF kappa B activation, as indicated by NF kappa B DNA binding, was detected by electrophoretic mobility shift assays and enzyme-linked immunosorbent assay. Hydrogen gas inhalation increased NF kappa B DNA binding after 1 h of ventilation and decreased NF kappa B DNA binding after 2 h of ventilation, as compared with controls. The early activation of NF kappa B during hydrogen treatment was correlated with elevated levels of the antiapoptotic protein Bcl-2 and decreased levels of Bax. Hydrogen inhalation increased oxygen tension, decreased lung edema, and decreased the expression of proinflammatory mediators. Chemical inhibition of early NF kappa B activation using SN50 reversed these protective effects. NF kappa B activation and an associated increase in the expression of Bcl-2 may contribute, in part, to the cytoprotective effects of hydrogen against apoptotic and inflammatory signaling pathway activation during VILI. (C) 2011 Elsevier Inc. All rights reserved.