Surfactant Protein B and the Lung-HDL-Vascular Axis: Linking Pulmonary Injury to Cardiovascular Risk.

PURPOSE OF REVIEW: Pulmonary surfactant protein B (SFTPB) is a lung-specific protein essential for surfactant function. This review summarizes its biology, circulation during pulmonary injury, association with high-density lipoprotein (HDL), and emerging links to cardiovascular disease (CVD). RECENT FINDINGS: Alveolar–capillary barrier disruption in heart failure, valvular disease, acute respiratory distress syndrome, and smoking permits immature SFTPB (pro-SFTPB) to enter the bloodstream. Circulating pro-SFTPB binds predominantly to HDL, impairing antioxidant capacity while largely preserving cholesterol efflux and endothelial anti-inflammatory functions. HDL-bound SFTPB reflects pulmonary–vascular stress and predicts incident CVD independently of traditional risk factors. These observations support a “lung–HDL–vascular” axis in which alveolar–capillary injury is encoded in circulating HDL. SFTPB functions as a sensitive biomarker of lung–vascular crosstalk, and future studies should clarify its functional relevance, temporal dynamics, and translational potential.