Ceramide-Induced Destruction in Emphysema

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Abstract A hallmark of emphysema is the net loss of cells that form alveolar units required for gas exchange, due to increased injury and impaired cell repair caused by inhalation of cigarette smoking (CS). Our proposal will focus on how to enhance the survival and repair of lung microvascular endothelial cells, which are essential for the maintenance of the alveolo-capillary membrane. To survive stress, injured cells engage a repair process, autophagy, characterized by a sequence of steps (flux) devoted to the lysosomal degradation of damaged proteins and organelles. Despite progress made in linking autophagy with COPD, little is known as to how CS disrupts autophagic flux and approaches to restore its proper function are lacking. We propose to fill this knowledge gap, by elucidating the regulation of lysosomal fitness and autophagic flux by sphingolipid metabolites during homeostasis and CS exposure. We uncovered two sphingolipid rheostats (sphingosine/S1P and ceramide/glucosylceramide) that control the autophagy flux, but are disturbed by CS. We hypothesize that restoration of the sphingolipid rheostat is required to complete lysosomal autophagy and repair cigarette smoke-induced lung microvascular endothelial cell injury and will alleviate emphysema. We will use complementary approaches of human lung primary endothelial cells in 2D and 3D models of repair, including co-cultured with alveolar type II epithelial cells, human precision cut lung slices, and mouse models of CS exposure, to pursue three specific aims. Completion of these aims will fill important knowledge gaps in emphysema pathogenesis, will mechanistically link targeted metabolomics with functional outcomes, and provide potential new targets for treatment of emphysema.