Noblesse oblige: NRF2 functions in the airways.

The transcription factor, nuclear factor (NF), erythroid-derived 2-related factor 2 (NRF2), was discovered nearly 2 decades ago. Since then, over 4,000 papers have been published on NRF2 function in diverse biological systems, and it has been found to be a critical regulator of antioxidant and defense genes with antioxidant response elements in their promoters. NRF2 is particularly important in protecting cells and tissues under highly oxidative microenvironments, including the airways that interface with the external environment and are exposed to pollutants and other oxidant stressors. Using mice with targeted deletion of Nrf2, a protective role for this transcription factor has been determined in many model diseases, including acute lung injury, emphysema, allergy and asthma, pulmonary fibrosis, and respiratory syncytial virus disease. Recent studies have also found that murine Nrf2 is important in lung development and protection against neonatal lung injury. Moreover, functional polymorphisms in human NRF2 have been known to associate with disease severity, indicating a potentially important protective function. However, there is also a "dark side" to NRF2 function, as it has been found to enhance advanced stages of carcinogenesis in the lung and some other tissues. NRF2 inducers such as phytochemical isothyocyanates and synthetic triterpenoids, have been discovered and used in model systems of oxidant-induced lung diseases, and data suggest a potential for clinical interventions. Future investigations of NRF2 should yield further insight into its contribution to normal and pathophysiological conditions in the airways, and alternative treatment strategies to protect against oxidative respiratory disease.