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EXERCISE AND RESPIRATORY PHYSIOLOGY

Differences in lung glutathione metabolism may account for rodent susceptibility in elastase-induced emphysema development

Departments of ¹Respiratory Diseases, ²Hematology, and ³Nutrition and Diabetes, and ⁴Medical Research Center, School of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile

Submitted 16 April 2008 ; accepted in final form 9 January 2009

Syrian Golden hamsters develop more severe emphysema than Sprague-Dawley rats after intratracheal instillation of the same dose of elastase/body weight. Although species variations in antielastase defenses may largely explain these results, other variables, such as differences in lung antioxidants, cannot be overlooked since oxidative stress modulates antiprotease activity. We propose that elastase instillation might affect lung glutathione (GSH) metabolism differently in these species. Our aim was to study in hamsters and rats, lung glutathione metabolism at different times, from the stage of diffuse alveolar damage to advanced emphysema. We measured total and oxidized glutathione content as well as activity and expression of enzymes related to GSH synthesis and redox cycling: -glutamylcysteine synthetase, glutathione peroxidase, and glutathione reductase. Whereas rats showed no significant changes in these measurements, hamsters showed significant derangement in GSH metabolism early after elastase instillation: 25% fall in total GSH (P < 0.05) with no increase in oxidized glutathione associated with reduced enzyme activities 24 h after elastase [60% for -glutamylcysteine synthetase (P < 0.01), 30% for glutathione peroxidase (P < 0.01), and 75% for glutathione reductase (P < 0.001)]. GSH homeostasis was restored at the end of the first week, involving transient increased expression of these enzymes. We conclude that elastase induces significant alterations in GSH metabolism of hamster lungs and no overall change in rat lungs. Although differences in disease severity may account for our findings, the hamster becomes vulnerable to functional inhibition of ₁-antitrypsin by oxidants and thus, even more susceptible to injury than it would be, considering only its low ₁-antitrypsin level.

diffuse alveolar damage; -glutamyl-cysteine synthetase; glutathione peroxidase; glutathione reductase; lung susceptibility to elastase; pulmonary emphysema