SERPINE1/PAI-1 contributes to an inflammatory capillary endothelial program and immune-cell adhesion during lung ischemia–reperfusion injury

Introduction Lung ischemia–reperfusion injury (LIRI) is characterized by rapid inflammatory activation and leukocyte–endothelial interactions that contribute to primary graft dysfunction after lung transplantation. However, the endothelial states coordinating these responses remain incompletely understood. We investigated whether SERPINE1 and its encoded protein, plasminogen activator inhibitor-1 (PAI-1), contribute to an inflammatory endothelial program associated with immune-cell adhesion during reperfusion. Methods We integrated paired human bulk transcriptomic datasets (GSE145989 and GSE18995) with single-cell RNA sequencing, interpretable machine learning, cell–cell communication inference, in silico network perturbation, and metabolic trajectory analysis. Complementary mouse whole-lung lipidomics provided pathway-level comparisons. The functional effects of SERPINE1 silencing and pharmacological PAI-1 inhibition with tiplaxtinin were evaluated in human pulmonary microvascular endothelial cells exposed to hypoxia/reoxygenation (H/R), using immunoblotting, immunofluorescence, and THP-1 cell adhesion assays. Results Bulk transcriptomic analyses identified 14 candidate genes, from which random-forest feature selection retained nine core features for a support vector machine classifier, with SERPINE1 making the largest contribution to reperfusion-status classification. Single-cell analyses localized SERPINE1 to a stress-responsive capillary endothelial state enriched for TNF/NF-κB, interferon, inflammatory/senescence-associated secretory phenotype, and adhesion-related programs. Inferred cell–cell communication suggested enhanced interactions involving NK cells, monocytes, and macrophages. In silico SERPINE1 perturbation identified ICAM1 as a network-sensitive node. In H/R-exposed endothelial cells, SERPINE1 silencing and PAI-1 inhibition reduced ICAM1 expression and THP-1 adhesion, attenuated senescence-like markers, and partially restored junction-associated proteins. Discussion These findings identify SERPINE1/PAI-1 as a component of a stress-responsive inflammatory capillary endothelial program during lung reperfusion and provide functional evidence supporting its contribution to inflammatory endothelial dysfunction and immune-cell adhesion.