Regulation of glutathione in inflammation and chronic lung diseases

Oxidant/antioxidant imbalance, a major cause of cell damage, is the hallmark for lung inflammation. Glutathione (GSH), a ubiquitous tripeptide thiol, is a vital intra- and extra-cellular protective antioxidant against oxidative stress, which plays a key role in the control of signaling and pro-inflammatory processes in the lungs. The rate-limiting enzyme in GSH synthesis is glutamylcysteine ligase (GCL). GSH is essential for development as GCL knock-out mouse died from apoptotic cell death. The promoter (5′-flanking) region of human GCL is regulated by activator protein-1 (AP-1) and antioxidant response element (ARE), and are modulated by oxidants, phenolic antioxidants, growth factors, inflammatory and anti-inflammatory agents in various cells. Recent evidences have indicated that Nrf2 protein, which binds to the erythroid transcription factor (NF-E2) binding sites, and its interaction with other oncoproteins such as c-Jun, Jun D, Fra1 and Maf play a key role in the regulation of GCL. Alterations in alveolar and lung GSH metabolism are widely recognized as a central feature of many chronic inflammatory lung diseases. Knowledge of the mechanisms of GSH regulation could lead to the pharmacological manipulation of the production and/or gene transfer of this important antioxidant in lung inflammation and injury. This article describes the role of AP-1 and ARE in the regulation of cellular GSH biosynthesis and assesses the potential protective and therapeutic role of glutathione in oxidant-induced lung injury and inflammation.