The anti-inflammatory profile of inhaled corticosteroids: biopsy studies in asthmatic patients

The beneficial effects of inhaled corticosteroids in the treatment of asthma are well established. A potent topical anti-inflammatory action is assumed to underlie the therapeutic effect, given that these agents alter the number and function of a range of inflammatory cells and markers in airway biopsies. This activity profile is shown by all inhaled corticosteroids, in a variety of patient types and study designs. Thus, treatment with inhaled corticosteroids leads to consistent reductions in the number and activation of mast cells and eosinophils in biopsy specimens. Other relevant findings include reductions in T-lymphocytes, which contribute to chronic inflammation via the secretion of pro-inflammatory cytokines (some of which are responsible for eosinophil accumulation and activation). Inhaled corticosteroids may therefore act by down-regulating immunoreactivity, so reducing activation of T lymphocytes and (consequently) eosinophils. There is considerable interest in whether corticosteroids can inhibit or reverse some structural changes in the airways, including basement membrane thickening, collagen deposition and increased airway vascularity; it has been suggested that these changes may contribute towards airway hyperresponsiveness and irreversible airway obstruction. In summary, inhaled corticosteroids have a broad spectrum of anti-inflammatory activity in asthma patients, but the relationship between changes in clinical and immunopathological parameters, particularly in the long-term, requires further study.