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Glutathione Transferase P1

An Endogenous Inhibitor of Allergic Responses in a Mouse Model of Asthma

¹ Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia; ² Cancer Research UK, Molecular Pharmacology Unit, Ninewells Hospital and Medical School, Dundee, United Kingdom; ³ Priority Research Centre for Asthma and Respiratory Disease, Faculty of Health and Hunter Medical Research Institute, University of Newcastle, Newcastle, Australia

Correspondence and requests for reprints should be addressed to Dianne C. Webb, Ph.D., Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia. E-mail: dianne.webb{at}anu.edu.au

Rationale: Although epidemiological studies have linked asthma susceptibility and severity to polymorphisms in human glutathione transferase Pi (GSTP) 1, there is no direct evidence for a functional involvement of GSTP1 in processes that are pathognomic of asthma.

Objectives: To examine the role of GSTP1 in modulating the development of allergic airways disease.

Methods: Allergic airways disease was induced in wild-type (WT) and Gstp-null mice employing both acute and chronic models. Eosinophilia, goblet cells, and remodeling were quantified by histological assessment; respiratory function was determined using invasive methods. ELISA was used to evaluate Th2 cytokines, eotaxin, and phospho-c-Jun. Gstp1/2 expression was quantified by reverse transcriptase–polymerase chain reaction.

Measurements and Main Results: Compared with allergic WT mice, eosinophilia, goblet cell hyperplasia, airway remodeling, lung resistance, and IL-5 were enhanced in allergic Gstp-null mice. However, the protective efficacy of GSTP1 was mouse-strain dependent, and associated with inherent variation in expression of Gstp1. Although elevated levels of phospho-c-Jun were detected in Gstp-null mice, treatment of WT mice with a GSTP/c-Jun N-terminal kinase (JNK) inhibitory peptide enhanced phospho-c-Jun and significantly attenuated allergic responses.

Conclusions: GSTP1 attenuates the severity of allergic airways disease. However, the efficacy of GSTP1 correlated with mouse strain-dependent variation in Gstp1 expression. Although GSTP1 attenuated c-Jun phosphorylation, treatment with a GSTP/JNK inhibitory peptide revealed an inverse relationship between c-Jun phosphorylation and allergic responses, indicating that the mechanism by which GSTP attenuates allergic responses is not dependent on the JNK/c-Jun axis. Our data, together with epidemiological evidence, suggest variation in expression and/or function of this protein is an important determinant in asthma pathophysiology.

Key Words: asthma • oxidative stress • Th2 cytokines • JNK

AT A GLANCE COMMENTARY Scientific Knowledge on This Subject Although many epidemiological studies have linked polymorphisms in glutathione transferase Pi (GSTP) 1 with the development and severity of asthma, there is no direct evidence that this enzyme participates in the pathophysiological processes that underlie the clinical symptoms of asthma. What This Study Adds to the Field GSTP1 attenuates allergic inflammation, respiratory dysfunction, and remodeling. However, the effects are dependent on the level of Gstp1 expression, suggesting that factors that influence the function of GSTP1 contribute to the severity of asthma.

 

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