Chronic airway inflammation is the key characteristic common to COPD and asthma. However, different cellular mechanisms are involved in the pathophysiology of both airway diseases. In COPD, prominent pro-inflammatory effector cells are CD8+ T-cells, neutrophils, and macrophages, whereas in asthma, CD4+ T-cells, eosinophils, and dendritic cells are relevant to the inflammatory process. Phosphodiesterase 4 (PDE4) is expressed in all inflammatory cells and degrades cAMP, an intracellular modulator of various pro-inflammatory responses. Thus, PDE4 inhibition represents a key target for anti-inflammatory therapies. We examined the in vitro effects of roflumilast, an investigational PDE4 inhibitor, on human inflammatory cells.
Cells were isolated from human peripheral blood of healthy donors. Release of cytokines was determined using ELISA. Reactive oxygen species (ROS) were measured using a luminol-enhanced chemiluminescence assay. Leukotrienes were analyzed by HPLC. Cell proliferation was determined by incorporation of [3H] thymidine.
In CD8+ T-cells, roflumilast reduced the anti-CD3 induced release of granzyme B and interleukin (IL)-2 in the presence of a PDE3-selective inhibitor with IC50 values of 2.7nM and 8.5nM, respectively. Roflumilast almost completely inhibited leukotriene B4 synthesis in neutrophils (IC50=2nM) whereas ROS formation was reduced up to 70% with an IC35 value of 4nM. Additionally, roflumilast inhibited TNFα release from monocyte-derived macrophages by about 70% (IC35=13nM) when tested in the presence of a PDE3-selective inhibitor and 1nM PGE2. In CD4+ T-cells, roflumilast inhibited cell proliferation by about 60% (IC30=7nM) as well as IL-2, IL-4, and IL-5 synthesis (IC values ranged from 1 to 13nM). Further, roflumilast suppressed fMLP-induced ROS release from eosinophils by about 70% (IC35=7nM). Lipopolysaccharide-induced release of TNFα from monocyte-derived dendritic cells was partially inhibited by roflumilast (IC20=5nM).
Roflumilast has shown effective inhibition of human inflammatory cell functions in vitro, which are involved in the pathogenesis of COPD and asthma.
The PDE4 inhibitor roflumilast may provide anti-inflammatory treatment for patients with chronic inflammatory airway diseases such as COPD and asthma.
Shahin Sanjar, Employee The presenting author S Sanjar is employee of ALTANA Pharma AG, Florham Park, NJ, USA. The authors H Tenor, A Hatzelmann, and C Schudt are employees of ALTANA Pharma AG, Konstanz, Germany.; Product/procedure echnique that is considered research and is NOT yet approved for any purpose. The authors have been involved in the presented research on the investigational product roflumilast, which is in clinical development and sponsored by ALTANA Pharma AG.