Steroid-resistant inflammation in a rat model of chronic obstructive pulmonary disease is associated with a lack of nuclear factor-kappaB pathway activation

RATIONALE: Emphysema is one component of chronic obstructive pulmonary disease (COPD), a respiratory disease currently increasing in prevalence worldwide. The mainstay therapy adopted to treat patients with COPD is glucocorticoids; unfortunately, this treatment has limited impact on disease symptoms or underlying airway inflammation. OBJECTIVE: There is an urgent need to develop therapies that modify both the underlying inflammation, thought to be involved in disease progression, and the structural changes in the emphysematous lung. METHODS: We have characterized an elastase-driven model of experimental emphysema in the rat that demonstrates COPD-like airway inflammation and determined the impact of a clinically relevant glucocorticoid. MEASUREMENTS AND MAIN RESULTS: We observed an increase in lung neutrophils, lymphomononuclear cells, mucus production, and inflammatory cytokines. Also present were increases in average air space area, which are associated with emphysema-like changes in lung function, such as increased residual volume and decreased flow; these increases in area were maintained for up to 10 weeks. In addition, we observed that elastase-induced airway neutrophilia is steroid resistant. Interestingly, the inflammation observed after elastase administration was found to be temporally associated with a lack of nuclear factor-kappaB pathway activation. This apparent nuclear factor-kappaB-independent inflammation may explain why treatment with a glucocorticoid was ineffective in this preclinical model and could suggest parallels in the steroid-resistant human disease. CONCLUSION: We believe that this model, in addition to its suitability for testing therapies that may modify existing emphysema, could be useful in the search for new therapies to reduce the steroid-resistant airway inflammation evident in COPD.