• Ken R Bracke, Guy F Joos, Guy G Brusselle, Constantinos Glynos, Lisa L Dupont, Theodoros Vassilakopoulos, Andreas Papapetropoulos, Peter Brouckaert, and Athanassios Giannis.
• 1 Laboratory for Translational Research in Obstructive Pulmonary Diseases, Department of Respiratory Medicine, Ghent University Hospital, Ghent, Belgium.
• Am. J. Respir. Crit. Care Med.. 2013 Oct 1;188(7):789-99.

RationaleSoluble guanylyl cyclase (sGC), a cyclic guanosine 5'-monophosphate-generating enzyme, regulates smooth muscle tone and exerts antiinflammatory effects in animal models of asthma and acute lung injury. In chronic obstructive pulmonary disease (COPD), primarily caused by cigarette smoke (CS), lung inflammation persists and smooth muscle tone remains elevated, despite ample amounts of nitric oxide that could activate sGC.ObjectivesTo determine the expression and function of sGC in patients with COPD and in a murine model of COPD.MethodsExpression of sGCα1, α2, and β1 subunits was examined in lungs of never-smokers, smokers without airflow limitation, and patients with COPD; and in C57BL/6 mice after 3 days, 4 weeks, and 24 weeks of CS exposure. The functional role of sGC was investigated in vivo by measuring bronchial responsiveness to serotonin in mice using genetic and pharmacologic approaches.Measurements And Main ResultsPulmonary expression of sGC, both at mRNA and protein level, was decreased in smokers without airflow limitation and in patients with COPD, and correlated with disease severity (FEV1%). In mice, exposure to CS reduced sGC, cyclic guanosine 5'-monophosphate levels, and protein kinase G activity. sGCα1(-/-) mice exposed to CS exhibited bronchial hyperresponsiveness to serotonin. Activation of sGC by BAY 58-2667 restored the sGC signaling and attenuated bronchial hyperresponsiveness in CS-exposed mice.ConclusionsDown-regulation of sGC because of CS exposure might contribute to airflow limitation in COPD.

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