Oxidant stress suppresses CFTR expression.
Epithelial mucous membranes are repeatedly exposed to oxidants and xenobiotics. CFTR plays a role in glutathione transepithelial flux and in defining the hydration and viscoelasticity of protective mucus. We therefore hypothesized that CFTR expression and function may be modulated by oxidant stress. A sublethal oxidant stress (tert-butylhydroquinone, BHQ) in CFTR-expressing epithelial cells (T84) induced a significant increase in cellular glutathione that was associated with an increase in expression of the gene encoding the heavy subunit of the rate-limiting enzyme for glutathione synthesis, gamma-glutamylcysteine synthetase (gamma-GCShs). CFTR gene expression was markedly decreased according to a time course that mirrored the changes in gamma-GCShs. Western blot analysis confirmed that the decrease in CFTR gene expression was associated with a decrease in CFTR protein. cAMP-dependent iodide efflux was also decreased by the oxidant stress. Nuclear run-on assays indicated that the oxidant stress had no effect on CFTR gene transcription, but the mRNA stability in the oxidant-stressed cells was markedly reduced. Furthermore, BHQ increased gamma-GCShs mRNA while decreasing CFTR mRNA in Calu-3 cells, and taurine chloramine induced similar effects in T84 cells. We conclude that suppression of CFTR expression may represent an adaptive response of mucosal epithelium to an exogenous oxidant stress.
Cantin
André M
AM
Pulmonary Research Unit, Faculty of Medicine, Univ. of Sherbrooke, 3001, 12ième Ave. Nord, Sherbrooke, QC, Canada J1H 5N4. Andre.Cantin@USherbrooke.ca
Bilodeau
Ginette
G
Ouellet
Cristine
C
Liao
Jie
J
Hanrahan
John W
JW
D000230:Adenocarcinoma; D000975:Antioxidants / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D000242:Cyclic AMP / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D004347:Drug Interactions; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D005721:Glutamate-Cysteine Ligase / Q000235:genetics; D005978:Glutathione / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006873:Hydroquinones / Q000633:toxicity; D007457:Iodine Radioisotopes; D009077:Mucins / Q000494:pharmacology; D016877:Oxidants / Q000633:toxicity; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D013654:Taurine / Q000031:analogs & derivatives / Q000235:genetics / Q000633:toxicity
D000975:Antioxidants; D006873:Hydroquinones; D007457:Iodine Radioisotopes; D009077:Mucins; D016877:Oxidants; D012333:RNA, Messenger; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D013654:Taurine; C043410:N-chlorotaurine; C018855:2-tert-butylhydroquinone; D000242:Cyclic AMP; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione