Role of Glucosylceramide in Lung Endothelial Cell Fate and Emphysema

• Published in: American journal of respiratory and critical care medicine Vol. 200; no. 9; pp. 1113 - 1125
• Main Authors: Koike, Kengo, Berdyshev, Evgeny V, Mikosz, Andrew M, Bronova, Irina A, Bronoff, Anna S, Jung, John P, Beatman, Erica L, Ni, Kevin, Cao, Danting, Scruggs, April K, Serban, Karina A, Petrache, Irina
• Format: Journal Article
• Language: English
• Published: United States American Thoracic Society 01.11.2019
• Subjects: Animals; Apoptosis; Autophagy; Cell Culture Techniques; Cell Death; Chronic obstructive pulmonary disease; Disease Models, Animal; Endothelial Cells - pathology; Glucosylceramides - metabolism; Lung cancer; Lungs; Mice; Original; Pulmonary Emphysema - etiology; Pulmonary Emphysema - metabolism; Pulmonary Emphysema - pathology; Smoking - adverse effects; endothelium; apoptosis; autophagy; sphingolipids; chronic obstructive pulmonary disease
• ISSN: 1073-449X; 1535-4970
• DOI: 10.1164/rccm.201812-2311OC

The loss of pulmonary endothelial cells in emphysema is associated with increased lung ceramide. Ceramide perturbations may cause adaptive alterations in other bioactive sphingolipids, with pathogenic implications. We previously reported a negative correlation between emphysema and circulating glycosphingolipids (GSLs). Glucosylceramide (GlcCer), the initial GSL synthesized from ceramide by GCS (GlcCer synthase), is required for embryonic survival, but its role in the lung is unknown. To determine if cigarette smoke (CS) alters lung GlcCer and to elucidate the role of GCS in lung endothelial cell fate. GlcCer was measured by tandem mass spectrometry in BAL fluid of CS- or elastase-exposed mice, and GCS was detected by Western blotting in chronic obstructive pulmonary disease lungs and CS extract-exposed primary human lung microvascular endothelial cells (HLMVECs). The role of GlcCer and GCS on mTOR (mammalian target of rapamycin) signaling, autophagy, lysosomal function, and cell death were studied in HLMVECs with or without CS exposure. Mice exposed to chronic CS or to elastase, and patients with chronic obstructive pulmonary disease, exhibited significantly decreased lung GlcCer and GCS. In mice, lung GlcCer levels were negatively correlated with airspace size. GCS inhibition in HLMVEC increased lysosomal pH, suppressed mTOR signaling, and triggered autophagy with impaired lysosomal degradation and apoptosis, recapitulating CS effects. In turn, increasing GlcCer by GCS overexpression in HLMVEC improved autophagic flux and attenuated CS-induced apoptosis. Decreased GSL production in response to CS may be involved in emphysema pathogenesis, associated with autophagy with impaired lysosomal degradation and lung endothelial cell apoptosis.