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Role of thioredoxin in ETS-induced pulmonary airway injury

Institution: University of California, Davis
Investigator(s): Reen Wu, Ph.D.
Award Cycle: 1998 (Cycle 7) Grant #: 7RT-0145 Award: $425,665
Subject Area: Pulmonary Disease
Award Type: Research Project Awards
Abstracts

Initial Award Abstract
Epidemiological studies have linked the causes of various illnesses in the human lung with cigarette smoke. The toxicity of mainstream smoke, and the health effects caused by smoking, are well recognized. By contrast, the toxicity of environmental tobacco smoke (ETS, or secondhand smoke) on the lung is less clear. This is partly due to the diluted nature of secondhand smoke or ETS. However, previous studies from researchers at this campus and elsewhere have demonstrated the toxicity of ETS on developing airways in the lung, and the associated induction of several genes, including the thioredoxin (TRX) gene, in airway epithelial (surface-lining) cells. Although induction of the TRX gene (and the resulting cellular production of thioredoxin, which can act as an antioxidant) may be part of a protective response by airway epithelial cells against exposure to ETS, the significance of this association remains unclear. Since ETS contains numerous free radicals as well as reactive oxygen and nitrogen species that could cause injury and alter the normal patterns of gene expression in airway epithelial cells, we plan to determine the functional role of antioxidant TRX, in ETS mediated injury. Based on the data obtained from preliminary experiments, we propose to test a hypothesis that a difference in the amount of protein (thioredoxin) produced by induction of the TRX gene (in response to ETS exposure) plays a critical role in ETS induced airway injury. Using a transgenic mouse model, the levels of TRX gene product in airway epithelial cells will be manipulated, using a specific genetic promoter that targets the TRX gene. Those mice whose TRX gene expression levels are artificially altered, and control groups (i.e., “normal” mice with no altered TRX gene expression) will then be exposed to ETS. The effects of ETS on airway epithelial cells will be assessed. Lastly, we will use the primary airway epithelial cell culture model to assess whether these changes in vivo can be controlled and whether these changes are due solely to the difference in TRX levels in these cells. Information obtained from these in vivo and in vitro studies will provide a better understanding of how a naturally occurring antioxidant-production pathway can protect airway epithelial cells from exposure to ETS.

Final Report
Conducting airway epithelial cells are primary targets of injury by inhaled mainstream (MS) and environmental tobaccos smoke (ETS). A subsequent of the smoke-related diseases and injuries are the induction of various lung diseases, including emphysema, bronchitis and lung cancer. Both ETS and MS smokes contain numerous free radicals, reactive oxygen species, and reactive nitrogen species that can present an “oxidative stress” to the conducting airway epithelia. These highly reactive elements in smoke will facilitate antioxidant oxidation, lipid peroxidation, protein modification and DNA oxidation, nitration, and adduct formation. These changes, if occur in airway epithelia, may direct changes in gene expression pattern, impair the mucociliary function and lead to the persistent airway inflammation. In this proposal, we focus on the role of thioredoxin (TRX) on ETS-induced lung injury. TRX is a ubiquitous protein and has been implicated in a variety of cellular activities, such as DNA replication, antioxidant activity, and regulation of gene expression. In this study, (1) we demonstrated an abundant presence of TRX gene products in airway epithelia, especially in the ciliated cell type. We have demonstrated that vitamin A and its metabolites (retinoids) enhance TRX the transcription of TRX gene. This enhancement is mediated through the classical interactions between retinoic acid nuclear receptors (RAR/RXRs) and the 4 retinoic acid-responsive elements (RAREs) located at the 5’-flanking region of TRX gene. (2) We have also demonstrated that TRX can serve as an antioxidant role. In vivo, it was rapidly oxidized in ozone-exposed airway epithelium. In vitro, an elevated expression of TRX in a human bronchial epithelial cell line, HBE1, also elevates the resistance of cultured cells to the hydrogen peroxide treatment and the smoke exposure. (3) We have also demonstrated that TRX modulates IL-8 production in cultured airway epithelial cells. IL-8 production by airway epithelial cells has been implicated as one of initial events that lead to the influx of neutrophil to the airway lumen after smoke or ozone exposure. Using various molecular and biochemical approaches, we determined that TRX is uniquely involved in the transcriptional regulation of IL-8 gene expression by restoring the activity of the key transcription factor, NF-B. This activity could not be demonstrated in other antioxidant chemicals, such as GSH and N-acetyl-cysteine. (4) Lastly, we demonstrated that TRX is translocated into the nucleus upon the oxidant treatment. The translocation is coincided with the activation of IL-8 gene expression. These results support an important role of TRX in the modulation of smoke-induced injury response. A further study at the in vivo level is needed. Such a study is important to determine whether TRX is an important target for the development of the antioxidant strategy or an important therapeutic target for modulating the inflammatory response after smoke inhalation.
Publications

Structure and organization of the gene encoding a mouse small proline-rich proteins, mSPRR1A and 1B
Periodical: Gene Index Medicus:
Authors: Reddy SPM, Konkin T, Wu R ART
Yr: 1998 Vol: 224 Nbr: Abs: Pg: 59-66

Differential expression of stress proteins in non-human primate lung and conducting airway after ozone exposure
Periodical: American Journal of Physiology Index Medicus:
Authors: Wu R, Zhao YH, Plopper CG, et al ART
Yr: 1999 Vol: 277 Nbr: Abs: Pg: L511-L522

A novel mechanism of retinoic acid-enhanced interleukin-8 gene expression in airway epithelium
Periodical: American Journal of Respiratory Cell and Molecular Biology Index Medicus:
Authors: Chang MMJ, Harper R, Hyde DM, Wu R ART
Yr: 2000 Vol: 22 Nbr: Abs: Pg: 502-510

Distinct roles for amino- and carboxyl-terminal sequences of SPRR1 protein in the formation of cross-linked envelopes of conducting airway epithelial cells
Periodical: Journal of Biological Chemistry Index Medicus:
Authors: Deng J, Pan R, Wu R ART
Yr: 2000 Vol: 275 Nbr: Abs: Pg: 5739-5747

Induction of cell cornification and enhanced squamous cell marker SPRR1 gene expression by phorbol ester are regulated by different signaling pathways in human conducting airway epithelial cells
Periodical: American Journal of Respiratory Cell and Molecular Biology Index Medicus:
Authors: Deng J, Chen Y, Wu R ART
Yr: 2000 Vol: 22 Nbr: Abs: Pg: 597-603

Mechanism of dexamethasone mediated interleukin-8 gene suppression in cultured airway epithelial cells
Periodical: American Journal of Physiology Index Medicus:
Authors: Chang MMJ, Juarez M, Hyde DM, Wu R ART
Yr: 2001 Vol: 280 Nbr: Abs: Pg: L107-L115

Characterization of human MUC5B gene expression in airway epithelium and the genomic clone of the amino-terminal and 5'-flanking region
Periodical: American Journal of Respiratory and Critical Care Medicine Index Medicus:
Authors: Chen Y, Zhao YH, Di P, Wu R ART
Yr: 0 Vol: Nbr: Abs: Pg:

Oxidative stress disrupts glucocordicoid hormone-dependent transcription of the amiloride sensitive epithelial sodium channel a-subunit in lung epithelial cells through ERK-dependent and thioredoxin-sensitive pathways
Periodical: Journal of Biological Chemistry Index Medicus:
Authors: Wang HC, Zentner MD, Deng HT, et al ART
Yr: 2000 Vol: 275 Nbr: Abs: Pg: 8600-8609

Phorbol ester-induced expression of airway squamous cell diffeeerentiation marker, SPRR1B, gene is regulated by PKC/Ras/Mekk1/Mkk1-dependent/AP-1 signal transduction pathway
Periodical: Journal of Biological Chemistry Index Medicus:
Authors: Vuong H, Patterson T, Shapiro P, et al ART
Yr: 2000 Vol: 275 Nbr: Abs: Pg: 32250-32259

Allergic asthma induced in rhesus monkeys by hosue dust mite
Periodical: American Journal of Pathology Index Medicus:
Authors: Schelegle ES, Gershwin LJ, Miller LA, et al ART
Yr: 2001 Vol: 158 Nbr: Abs: Pg: 333-341

Fishing for inflammatory cytokine-induced genes with an old trick
Periodical: American Journal of Physiology Index Medicus:
Authors: Wu R, Chen Y ART
Yr: 2001 Vol: 280 Nbr: Abs: Pg: L839-L840

Characterization of a novel airway epithelial cell-specific-chain alcohol dehydrogenase/reductase gene whose expression is upregulated by retinoids and is involved in the metabolism of retinol
Periodical: Journal of Biological Chemistry Index Medicus:
Authors: Cherly MS, Di YP, Hayden L, Zhao YH, Satre MA, Wu R ART
Yr: 0 Vol: Nbr: Abs: Pg: