Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada; Centre for Heart Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia, Canada. Electronic address: [Email]
Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in fibrillin-1 (Fbn1). Although aortic rupture is the major cause of mortality in MFS, patients also experience pulmonary complications, which are poorly understood. Loss of basal nitric oxide (NO) production and vascular integrity has been implicated in MFS aortic root disease, yet their contribution to lung complications remains unknown. Because of its capacity to potentiate the vasodilatory NO/cyclic guanylate monophosphate signaling pathway, we assessed whether the phosphodiesterase-5 inhibitor, sildenafil (SIL), could attenuate aortic root remodeling and emphysema in a mouse model of MFS. Despite increasing NO-dependent vasodilation, SIL unexpectedly elevated mean arterial blood pressure, failed to inhibit MFS aortic root dilation, and exacerbated elastic fiber fragmentation. In the lung, early pulmonary artery dilation observed in untreated MFS mice was delayed by SIL treatment, and the severe emphysema-like alveolar destruction was prevented. In addition, improvements in select parameters of lung function were documented. Subsequent microarray analyses showed changes to gene signatures involved in the inflammatory response in the MFS lung treated with SIL, without significant down-regulation of connective tissue or transforming growth factor-β signaling genes. Because phosphodiesterase-5 inhibition leads to improved lung histopathology and function, the effects of SIL against emphysema warrant further investigation in the settings of MFS despite limited efficacy on aortic root remodeling.