Role for Cystic Fibrosis Transmembrane Conductance Regulator Protein in a Glutathione Response to Bronchopulmonary Pseudomonas Infection

Abstract

The lung maintains an elevated level of glutathione (GSH) in epithelial lining fluid (ELF) compared to serum. The mechanism(s) by which the lung maintains high levels of ELF GSH and factors that modulate them are largely unexplored. We hypothesized that lung cystic fibrosis transmembrane conductance regulator protein (CFTR) modulates GSH efflux in response to extracellular stress, which occurs with lung infections. Mice were challenged intratracheally with Pseudomonas aeruginosa, and on the third day of infection bronchoalveolar lavage fluid was obtained and analyzed for cytokines and antioxidants. Lung tissue antioxidants and enzyme activities were also assessed. P. aeruginosa lung infection increased levels of inflammatory cytokines and neutrophils in the ELF. This corresponded with a marked threefold increase in GSH and a twofold increase in urate levels in the ELF of P. aeruginosa-infected wild-type mice. A twofold increase in urate levels was also observed among lung tissue antioxidants of P. aeruginosa-infected wild-type mice. There were no changes in markers of lung oxidative stress associated with the P. aeruginosa lung infection. In contrast with wild-type mice, the CFTR knockout mice lacked a significant increase in ELF GSH when challenged with P. aeruginosa, and this correlated with a decrease in the ratio of reduced to oxidized GSH in the ELF, a marker of oxidative stress. These data would suggest that the lung adapts to infectious agents with elevated ELF GSH and urate. Individuals with lung diseases associated with altered antioxidant transport, such as cystic fibrosis, might lack the ability to adapt to the infection and present with a more severe inflammatory response.

Glutathione Transport Is a Unique Function of the ATP-binding Cassette Protein ABCG2

“…Identifying compounds that increase the ABCG2-mediated GSH efflux may provide a pharmaceutical approach for increasing GSH concentrations in diseases associated with decreased extracellular GSH. A number of lung diseases such as cystic fibrosis (4,49) and idiopathic pulmonary fibrosis (50) are associated with low extracellular GSH levels.…”

“…mented (3)(4)(5)(6)(7)(8). For the purpose of detoxification and to respond to extracellular oxidative stress, cells express membrane proteins capable of transporting GSH, glutathione disulfide (GSSG), and GSH conjugates (GS-X).…”

Antioxidants preserve macrophage phagocytosis of Pseudomonas aeruginosa during hyperoxia

“…Even though prolonged exposure to hyperoxia does not suppress the level of SOD expression in macrophages [59], excessive levels of superoxide generated during hyperoxia may require high levels of SOD. In addition to rescuing macrophage function resulting from oxidative stress during hyperoxia, administration of antioxidants may also be useful in reducing ROS generated by bacteria themselves that are harmful to the host defense system [60,61].…”

Oxidative stress in cystic fibrosis lung disease: an early event, but worth targeting?

“…Previous reports supported the concept that the cystic fibrosis transmembrane conductance regulator (CFTR) itself transports glutathione, providing a potential explanation for the low glutathione levels in CF airways [9][10][11]. Alternatively to this CFTR-linked mechanism, activated neutrophils are also capable of oxidising and thereby disabling glutathione [12].…”