Evaluating glucocorticoid resistance in Asthma by analyzing peripheral blood mononuclear cells with FENO

Glucocorticoids(GC) have been extensively used in treating asthmatic patients. However, there is a small portion of these patients (10%-20%) do not respond to glucocorticoids well and thus their disease can not be controlled. The goal of the present study was to use Peripheral Blood Mononuclear Cells (PBMCs) from asthmatics to determine whether this in vitro model can inform us on the in vivo sensitivity status of patients to glucocorticoid therapy. First, we assessed the production of different T helper 2 (TH2) and non-TH2 cytokines such as interleukin-5(IL5), IL13 and IL17 by PBMCs stimulated by TCR(T cell receptor) engagement (dual stimulation anti-CD3 and anti-CD28 antibodies). Second, the in vitro sensitivity of PBMCs to dexamethasone(DEX) was determined by its ability to inhibit TCR-induced cytokine production. Association studies were then performed between the in vitro sensitivity of PBMC data and in vivo sensitivity to glucocorticoids by using fractional exhaled nitric oxide (FENO) suppression test. Our studies show that PBMCs isolated from patients stimulated by anti-CD3 and anti-CD28 antibodies for 24, 48 and 72h can produce both TH2 (IL5, IL13) and non-TH2 (IL17) cytokines which were optimum after 72h stimulation. Dexamethasone (10^-10- 10^-6M) dose-dependently inhibited TCR-induced cytokine production with different potency (IC50) and efficacy (Imax) values. Dexamethasone nearly produced 100% suppression of IL5 and IL13 at 10^-6M and that of IL17 10^-7M, indicating IL17 production by PBMCs was somewhat more sensitive to dexamethasone. Comparison of the IC50 values for IL5, IL13, IL17 between patients with FENO high>45ppb and those with FENO low<45ppb indicate a wide heterogeneity in asthmatic patients but no significant differences between groups. Suppression of IL13 by dexamethasone (IC50) negatively correlated with LOG10(delta FENO). Lower IL13 DEX IC50 in FENO high>45 ppb than FENO low<45 ppb patients, indicating FENO high patients are more sensitive to GC than FENO low patients.