[A study on the heterogeneous apoptosis of lymphocytes, eosinophils, and neutrophils from peripheral blood of asthmatic patients].

Objectives: To observe different responsiveness of lymphocytes, eosinophils, and neutrophils from peripheral blood of asthmatic patients to dexamethasone and montelukast-induced apoptosis and to explore the roles of Fas antigen and caspase-3 in the heterogeneity of cell apoptosis.
Methods: Lymphocytes, eosinophils, and neutrophils were isolated from peripheral blood of 18 asthmatic patients. Cells were incubated in vitro and treated with dexamethasone and leukotriene receptor antagonist montelukast respectively. Cell apoptosis rates and Fas expression rates were examined by flowcytometry whereas caspase-3 levels in these cells were detected by enzyme linked immunosorbent assay (ELISA).
Results: (1) Apoptosis rates: in vitro lymphocytes, eosinophils and neutrophils were compromised of spontaneous apoptosis at lower rates [(6.9 +/- 0.7)%, (31 +/- 11)% and (32 +/- 30)%, respectively]. With induction of dexamethasone, the apoptosis rates were (17.1 +/- 10.8)%, (44 +/- 22)% and (35 +/- 24)%. Montelukast markedly elevated the apoptosis rates of these three cells [(22.5 +/- 17.6)%, (50 +/- 27)% and (55 +/- 22)%, respectively] (compared to control, P < 0.01, < 0.05, > 0.05, respectively). (2) Fas expression: lymphocytes, eosinophils and neutrophils expressed low levels of Fas antigen at baseline [(1.50 +/- 0.07)%, (2.20 +/- 0.10)% and (1.21 +/- 0.09)%, respectively]. Dexamethasone induced Fas antigen expression levels of these cells of (6.58 +/- 2.10)%, (7.52 +/- 3.20)% and (3.24 +/- 2.34)%, and montelukast induced the expression levels of (5.06 +/- 1.66, 7.45 +/- 2.63, 3.03 +/- 2.47, P < 0.01, < 0.01, > 0.05, respectively). (3) caspase-3 levels: lymphocytes, eosinophils and neutrophils expressed constitutive caspase-3 levels of [(3.3 +/- 2.9) ng/L, (5 +/- 4) ng/L and (4.3 +/- 2.6) ng/L, respectively]. The dexamethasone induced caspase-3 levels were (6.7 +/- 3.1) ng/L, (6 +/- 3) ng/L and (3.1 +/- 1.8) ng/L. The montelukast induced levels were (5.2 +/- 3.7) ng/L, (8 +/- 4) ng/L, and (3.1 +/- 2.0) ng/L (compared to control, P < 0.01, < 0.01, > 0.05, respectively). It was demonstrated that dexamethasone and montelukast significantly induced apoptosis of lymphocytes and eosinophils which were assocreased with increased expression of Fas antigen and caspase-3. Dexamethasone was incapable of inducing neutrophils to apoptosis and had no significant effects on Fas expression and caspase-3 activity. Neutrophils underwent significant apoptosis after montelukast treatment, however, the induction was unlikely to be regulated by Fas and caspase-3 pathway.
Conclusions: In asthmatic inflammatory modulating and effective cells, neutrophils is distinct from lymphocytes and eosinophils in profile of apoptosis induced by glucocorticoids and leukotriene receptor antagonist. The signal pathway contributing neutrophil apoptosis heterogeneity may involve deficient caspase cascade or Fas/FasL.