The Role of Sphingolipids and Ceramide in Pulmonary Inflammation in Cystic Fibrosis

Abstract

Sphingolipids and in particular ceramide have been shown to be critically involved in the response to many receptor-mediated, but also receptor-independent, mainly stress stimuli. Recent studies demonstrate that ceramide plays an important role in the pathogenesis of cystic fibrosis, a hereditary metabolic disorder caused by mutations of the Cystic Fibrosis Transmembrane Conductance Regulator. Patients with cystic fibrosis suffer from chronic pulmonary inflammation and microbial lung infections, in particular with Pseudomonas aeruginosa. Chronic pulmonary inflammation in these patients seems to be the initial pathophysiological event. Inflammation may finally result in the high infection susceptibility of these patients, fibrosis and loss of lung function. Recent studies demonstrated that ceramide accumulates in lungs of cystic fibrosis mice and causes age-dependent pulmonary inflammation as indicated by accumulation of neutrophils and macrophages in the lung and increased pulmonary concentrations of Interleukins 1 and 8, death of bronchial epithelial cells, deposition of DNA in bronchi and high susceptibility to Pseudomonas aeruginosa infections. Genetic or pharmacological inhibition of the acid sphingomyelinase blocks excessive ceramide production in lungs of cystic fibrosis mice and corrects pathological lung findings. First clinical studies confirm that inhibition of the acid sphingomyelinase with small molecules might be a novel strategy to treat patients with cystic fibrosis.