ABSTRACT: Acute lung injury (ALI), characterized by disruption of the lung alveolar-capillary membrane barrier and resultant pulmonary edema, and associated with a proteinaceous alveolar exudate, is a leading cause of morbidity and mortality. Currently, inflammation-oxidative stress interaction between TNF-? and NF-?B was identified as a key pathway of ALI. We hypothesized that a TNFR-Fc fusion protein would have beneficial effects in experimental ALI, and sought to test this idea in mice by blocking TNF-?.Intratracheal instillation of lipopolysaccharide (LPS) into the lungs of ALI mice led to histiocyte apoptosis, and detection of serum and bronchoalveolar lavage fluid (BALF) cytokines, feedback between NF-?B and TNF-?, lung albumin leakage, lung damage, I?B kinase (IKK) and NF-?B activation, I-?B degradation, and oxidative injury. LPS administration raised pulmonary inflammation as reflected by increased inflammatory cytokines, alveoli protein concentration, and ALI scores. IKK is phosphorylated following LPS challenge, leading to I-?B degradation and NF-?B p65 phosphorylation. Furthermore, NF-?B is translocated into the nucleus and up-regulates TNF-? gene transcription. Infusion of TNFR-Fc 24h before LPS challenge significantly abrogated the increase of inflammatory cytokines, especially serum TNF-? concentration, as well as pulmonary alveoli protein levels, and diminished IKK and NF-?B activation and I-?B degradation. The nuclear translocation of NF-?B was inhibited, following by down-regulation of TNF-? gene transcription. In addition, LPS intratracheal instillation induced marked oxidative damage, such as a decrease in total anti-oxidation products and an increase in malondialdehyde (MDA), as well as up-regulation of oxidation enzymes. Histologic analysis and apoptosis scores revealed that the extent of tissue lesions was significantly reduced, but not abrogated, by TNF-? blockade.Treatment with LPS alone increased inflammation and oxidative stress in ALI mice, while administration of TNFR-Fc 24h before LPS challenge broke the feedback between NF-?B and TNF-?, resulting in decreased pulmonary inflammation/oxidative damage and tissue destruction. These results suggest a potential role for TNF-? therapy to treat clinical ALI.