Combination inhalers of long-acting β2 agonists (LABAs) with inhaled corticosteroids (ICSs) are now widely used for the treatment of asthma. However, corticosteroid (CS) insensitivity can be a major barrier for the treatment of chronic obstructive pulmonary disease (COPD). Existing ICSs are less beneficial on the decline of lung function in the long term. Even at the cellular level, CSs are less effective in primary cells, peripheral blood mononuclear cells (PBMCs) obtained from COPD patients

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... mpared to PBMCs from healthy volunteers. High levels of oxidative stress in COPD have been reported to be involved in CS insensitivity. In addition, oxidative stress has been reported to affect the β2 adrenergic receptor (β2AR) signalling itself. Here I hypothesise that oxidative stress affects the function of CSs and LABAs and/or their combination. Clarifying the molecular mechanism of this defect, will give new insights for the optimisation of the ideal CS/LABA combination therapy for the treatment of COPD. Primarily, pharmacological effects of fluticasone furoate (FF), a novel CS, were evaluated in various inflammation systems in respiratory cells and compared with those of currently available fluticasone propionate (FP) and budesonide (Bud). In the course of this study, FF was found to be a potent and long-acting CS. More importantly, the anti-inflammatory effects of FP were reduced under oxidative stress, whereas the effects of FF were not affected by oxidative stress. FF was also more effective on inhibiting cytokine release in PBMCs from COPD patients. Hence, this study demonstrated that FF is an oxidative stress insensitive CS. Furthermore, effects of oxidative stress on the function or signalling of LABAs were investigated. Salmeterol (SM)-induced cyclic AMP (cAMP) production was reduced under H2O2 treatment, while the effects of formoterol (FM) were not affected by H2O2. Under conditions of oxidative stress, SM also induced β2AR internalisation, whereas FM did not. Cell signalling analysis showed that FM partiall [...]