Nrf2 protects against acute lung injury and inflammation by modulating TLR4 and Akt signaling

Lung injury, which is associated with systemic inflammatory responses, is a common problem with significant morbidity and mortality. Here, we examined the involvement of toll-like receptor 4 (TLR4) and nuclear factor erythroid 2-related factor 2 (Nrf2) on intestinal ischemia-reperfusion (I/R)-induced lung injury in vivo and in vitro. Analysis of lung tissues in Nrf2-knockout mice by western blotting, immunohistochemistry, and TUNEL assay, and analysis of bronchoalveolar lavage fluid showed that Nrf2 deficiency upregulated TLR4, enhanced I/R-induced lung injury, apoptosis, inflammation, and autophagy, and increased the I/R-induced inactivation of Akt. In mouse lung epithelial cells subjected to oxygen and glucose deprivation/reperfusion (OGD/Rep), Nrf2 silencing increased the OGD/Rep-induced upregulation of TLR4 and MyD88 and downregulation of HO-1, and exacerbated OGD/Rep-induced apoptosis, autophagy, and the downregulation of phospho-Akt. TLR4 silencing and Akt inhibition experiments indicated that OGD/Rep-induced cell death by suppressing Akt signaling, and Nrf2 protected lung cells by modulating TLR4 and Akt signaling. These results indicated that the Nrf2/TLR4/Akt axis plays a role in inflammation-associated lung damage, suggesting potential therapeutic targets for the treatment of lung injury.