Cigarette smoke exposure alters phosphodiesterases in human structural lung cells

Cigarette smoke (CS), a highly complex mixture containing more than 4,000 compounds, causes aberrant cell responses leading to tissue damage around the airways and alveoli, which underlies various lung diseases. Phosphodiesterases (PDEs) are a family of enzymes that hydrolyze cyclic nucleotides. PDE inhibition induces bronchodilation, reduces the activation and recruitment of inflammatory cells, and the release of various cytokines. Currently, the selective PDE4 inhibitor roflumilast is an approved add-on treatment for patients with severe chronic obstructive pulmonary disease with chronic bronchitis and a history of frequent exacerbations. Additional selective PDE inhibitors are being tested in preclinical and clinical studies. However, the effect of chronic CS exposure on the expression of PDEs is unknown. Using mRNA isolated from nasal and bronchial brushes and lung tissues of never smokers and current smokers, we compared the gene expression of 25 PDE coding genes. Additionally, the expression and distribution of PDE3A and PDE4D in human lung tissues was examined. This study reveals that chronic CS exposure modulates the expression of various PDE members. Thus, CS exposure may change the levels of intracellular cyclic nucleotides and thereby impact the efficiency of PDE-targeted therapies.