LAUSR

ABSTRACT In this study, we aimed to investigate precise mechanism(s) of sphingolipid‐imbalance and resulting ceramide‐accumulation in COPD‐emphysema. Where, human and murine emphysema lung tissues or human bronchial epithelial cells (Beas2b) were used for experimental analysis. We found that lungs of smokers and COPD‐subjects with increasing emphysema severity demonstrate sphingolipid‐imbalance, resulting in significant ceramide‐accumulation and increased ceramide/sphingosine ratio, as compared to non‐emphysema/non‐smoker controls. Next, we found a substantial increase in emphysema chronicity‐related ceramide‐accumulation in murine (C57BL/6) lungs, while sphingosine levels only slightly increased. In accordance, the expression of the acid ceramidase decreased after CS‐exposure. Moreover, CS‐induced (sub‐chronic) ceramide‐accumulation was significantly (p < 0.05) reduced by treatment with TFEB/autophagy‐inducing drug, gemfibrozil (GEM), suggesting that autophagy regulates CS‐induced ceramide‐accumulation. Next, we validated experimentally that autophagy/lipophagy‐induction using an anti‐oxidant, cysteamine, significantly (p < 0.05) reduces CS‐extract (CSE)‐mediated intracellular‐ceramide‐accumulation in p62 + aggresome‐bodies. In addition to intracellular‐accumulation, we found that CSE also induces membrane‐ceramide‐accumulation by ROS‐dependent acid‐sphingomyelinase (ASM) activation and plasma‐membrane translocation, which was significantly controlled (p < 0.05) by cysteamine (an anti‐oxidant) and amitriptyline (AMT, an inhibitor of ASM). Cysteamine‐mediated and CSE‐induced membrane‐ceramide regulation was nullified by CFTR‐inhibitor‐172, demonstrating that CFTR controls redox impaired‐autophagy dependent membrane‐ceramide accumulation. In summary, our data shows that CS‐mediated autophagy/lipophagy‐dysfunction results in intracellular‐ceramide‐accumulation, while acquired CFTR‐dysfunction‐induced ASM causes membrane ceramide‐accumulation. Thus, CS‐exposure alters the sphingolipid‐rheostat leading to the increased membrane‐ and intracellular‐ ceramide‐accumulation inducing COPD‐emphysema pathogenesis that is alleviated by treatment with cysteamine, a potent anti‐oxidant with CFTR/autophagy‐augmenting properties. Graphical abstract Our study verifies that smokers and COPD subjects as well as mice exposed to cigarette smoke (CS) have alveolar sphingolipid‐imbalance (elevated ceramide/sphingosine ratio). Mechanistically, we demonstrate that CS‐exposure impairs autophagy/lipophagy in human and murine airway via activation of reactive oxygen species (ROS). This leads to intracellular ceramide‐accumulation into p62 + aggresome‐bodies. Additionally, CS‐induced acquired CFTR‐dysfunction results in ASM‐mediated membrane‐ceramide release. This unrestricted ceramide‐accumulation further aggravates airway homeostasis, especially in settings of chronic CS‐exposure, leading to COPD‐emphysema pathogenesis. As a proof of concept, cysteamine, an anti‐oxidant and autophagy‐inducing drug shows promise in controlling both membrane‐ and intracellular‐ ceramide accumulation as well as COPD‐emphysema pathogenesis. Figure. No Caption available. HighlightsCS‐exposure induces ROS‐mediated autophagy/lipophagy‐impairment that results in sphingolipid‐imbalance in the airway.CS‐exposure results in membrane‐ and intracellular‐ ceramide accumulation.Sphingolipid‐imbalance is elevated in the lungs of smokers and COPD‐emphysema subjects as compared to non‐smokers or control subjects.Cysteamine, an anti‐oxidant and autophagy‐inducing drug, corrects CS‐induced sphingolipid‐imbalance involved in COPD‐emphysema pathogenesis.