Surfactant protein D expression and clinical value of hypobaric hypoxia-induced acute lung injury and acute respiratory distress syndrome patients.

BACKGROUND: Surfactant protein D (SP-D) has been widely studied in infectious diseases, yet its role in aseptic inflammation remains poorly understood. This study aims to evaluate the clinical and mechanistic relevance of SP-D in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) induced by hypobaric hypoxia. METHODS: A hypobaric hypoxia-induced ALI model was established in rats at different time intervals (24, 48, and 72 h). SP-D levels were measured in lung tissue, bronchoalveolar lavage fluid (BALF), and serum, alongside inflammatory markers and hypoxia-inducible factor-1α (Hif-1α) expression. Serum SP-D levels were also compared between ARDS patients and healthy controls. RESULTS: Hypobaric hypoxia-induced dose-dependent lung injury in rats, with elevated inflammatory cytokines, increased Hif-1α expression, reduced SP-D in lung tissue, and increased SP-D in BALF and serum. BALF SP-D positively correlated with lung injury severity, while lung SP-D levels showed a negative correlation. In ARDS patients, serum SP-D levels were significantly elevated and negatively correlated with the oxygenation index. CONCLUSION: SP-D exhibits dynamic expression changes in response to hypoxia-induced lung injury and holds potential as a biomarker for assessing lung injury severity and predicting outcomes in ARDS.