Ceramide-Driven Mechanisms in Pulmonary Fibrosis.

Pulmonary fibrosis, particularly idiopathic pulmonary fibrosis (IPF), is a chronic and progressive interstitial lung disease characterized by alveolar epithelial injury, fibroblast activation, and excessive extracellular matrix deposition, which collectively lead to respiratory failure. Despite the availability of antifibrotic agents, disease-modifying therapies remain limited. Emerging evidence has identified dysregulated sphingolipid metabolism, especially ceramide accumulation, as a key driver of fibrotic pathogenesis. Ceramide is a central bioactive lipid in the sphingolipid pathway that regulates multiple cellular processes, including apoptosis, inflammation, endothelial barrier dysfunction, and fibroblast activation, all of which contribute to pulmonary fibrosis. This review is a narrative review that systematically summarizes the biosynthetic and metabolic pathways of ceramide, with an emphasis on chain length-specific functions and the ceramide to S1P rheostat. We further discuss the mechanistic roles of ceramide in alveolar epithelial cell apoptosis, inflammatory responses, and vascular barrier disruption in fibrotic lung disease. Finally, we highlight emerging therapeutic strategies that target ceramide metabolism, including inhibitors of acid sphingomyelinase (ASMase) and serine palmitoyltransferase (SPT), and propose future directions for clinical translation.