Increased peripheral blood T-cell apoptosis and decreased Bcl-2 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory airway disease, usually associated with cigarette smoking. Stimulated peripheral blood T cells from patients with COPD have an increased propensity to undergo apoptosis. The mitochondrial apoptotic pathway is regulated by pro-apoptotic proteins (including p53 and Bax) as well as anti-apoptotic proteins (e.g. Bcl-2) and cytokines (IL-2, IL-4 and IL-7). We hypothesized that alterations in expression of these apoptosis-related proteins, cytokines and cytokine receptors may be important in determining the susceptibility of T cells to undergoing apoptosis in COPD. We further hypothesized that inhaled corticosteroids (GCS) contribute to the increased rates of T-cell apoptosis observed in COPD. The process of apoptosis (assessed by Annexin V and ssDNA staining), as well as Bcl-2, Bax, p53, IL-2, IL-4 and receptors IL-7R, IL-4R and IL-2R gamma were investigated in PHA-stimulated peripheral blood-derived T cells, using flow cytometry. Fifteen patients with COPD receiving inhaled GCS (four of who received additional prednisolone), eight patients with COPD receiving symptom control medication, and 16 control subjects were studied. T cells (CD4(+) and CD8(+)) from GCS-treated COPD patients showed an increased propensity to undergo apoptosis, associated with significantly decreased Bcl-2 and IL-7 receptor expression. No significant differences were observed for the COPD patients who were receiving symptom control medication. These findings may suggest a negative peripheral effect of inhaled GCS on the immune system in COPD, although the clinical significance of these effects remains uncertain.