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

The beneficial effects of inhaled corticosteroids in the treatment of asthm a are well established. A potent topical anti-inflammatory action is assume d to underlie the therapeutic effect, given that these agents alter the num ber and function of a range of inflammatory cells and markers in airway bio psies. This activity profile is shown by all inhaled corticosteroids, in a variety of patient types and study designs. Thus, treatment with inhaled co rticosteroids leads to consistent reductions in the number and activation o f mast cells and eosinophils in biopsy specimens. Other relevant findings i nclude reductions in T-lymphocytes, which contribute to chronic inflammatio n via the secretion of pro-inflammatory cytokines (some of which are respon sible for eosinophil accumulation and activation). Inhaled corticosteroids may therefore act by down-regulating immunoreactivity, so reducing activati on of T lymphocytes and (consequently) eosinophils. There is considerable i nterest in whether corticosteroids can inhibit or reverse some structural c hanges in the airways, including basement membrane thickening, collagen dep osition 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 spectr um of antiinflammatory activity in asthma patients, but the relationship be tween changes in clinical and immunopathological parameters, particularly i n the long-term, requires further study.