PDE4B and chronic obstructive pulmonary disease: Collectively, we provided supportive evidence that the addition of Dex may improve the compromised anti-inflammatory effects of Roflumilast due to the up-regulated PDE4B and reduce the side effect of roflumilast through down-regulation of PDE4B expression in a GR-dependent manner in pulmonary diseases such as COPD and asthma (Figure 4D).