Inhaled sphingosine reduces bronchial Pseudomonas aeruginosa burden during porcine ex vivo lung perfusion and shows tissue delivery in explanted human lungs

Abstract

Abstract Pseudomonas aeruginosa infection remains a major challenge in donor lung management and post-transplant respiratory care, particularly in the setting of antimicrobial resistance. Ex vivo lung perfusion (EVLP) provides an opportunity for localized antimicrobial intervention before transplantation and allows detailed assessment of infection-associated lung injury under controlled conditions. In this study, we evaluated inhaled sphingosine in a porcine EVLP model of acute P. aeruginosa airway contamination using three experimental groups: uninfected controls, infected lungs treated with 0.9% NaCl, and infected lungs treated with sphingosine. This design allowed us to assess both the impact of P. aeruginosa infection on EVLP physiology and the effects of sphingosine on bacterial burden and infection-associated lung changes. Infected porcine lungs showed greater declines in dynamic and static compliance than uninfected controls, whereas pulmonary artery pressure, peak airway pressure, oxygen-exchange capacity, lactate accumulation, lung weight gain, and histological injury scores were not significantly worsened under the present experimental conditions. Inhaled sphingosine reduced bronchial P. aeruginosa CFU counts, whereas 0.9% NaCl did not. Sphingosine treatment did not further impair lung physiology, oxygenation, lactate accumulation, histological injury, or lung weight gain. Mechanistic analyses showed association of sphingosine with bacterial cardiolipin and increased colocalization of sphingosine with P. aeruginosa , consistent with a membrane-associated antibacterial mechanism described in previous studies. In exploratory experiments using four explanted human recipient lungs, sphingosine inhalation increased sphingosine levels in bronchial and parenchymal tissue and altered related sphingolipid metabolites, including sphingosine-1-phosphate, ceramide, and sphingomyelin, without apparent acute histological damage in assessed airway samples. One of the four human specimens showed bacterial colonization, in which a marked reduction in detectable bacterial growth after sphingosine inhalation was observed as a hypothesis-generating finding. Together, these data suggest that inhaled sphingosine can reduce acutely accessible bronchial P. aeruginosa burden during porcine EVLP without detectable short-term adverse effects and provide a basis for further investigation of sphingosine-related lipid metabolism and local antimicrobial strategies during EVLP.