ABSTRACTBackgroundThe receptor for advanced glycation end products (RAGE) modulates the pathogenesis of acute respiratory distress syndrome (ARDS). RAGE inhibition was recently associated with attenuated lung injury and restored alveolar fluid clearance (AFC) in a mouse model of ARDS. However, clinical translation will first require assessment of this strategy in larger animals.MethodsForty-eight anaesthetised Landrace piglets were randomised into a control group and three treatment groups. Animals allocated to treatment groups underwent orotracheal instillation of hydrochloric acid i) alone; ii) in combination with intravenous administration of a RAGE antagonist peptide (RAP), a S100P-derived peptide that prevents activation of RAGE by its ligands, or iii) in combination with intravenous administration of recombinant soluble (s)RAGE that acted as a decoy receptor. The primary outcome measure was net AFC at 4 h. Arterial oxygenation was assessed hourly for 4 h and alveolar-capillary permeability, alveolar inflammation, lung histology and lung mRNA expression of the epithelial sodium channel (α1-ENaC), α1-Na,K-ATPase and aquaporin (AQP)-5 were assessed at 4 h.FindingsTreatment with either RAP or sRAGE improved net AFC rates (median [interquartile range], 21.2 [18.8–21.7] and 19.5 [17.1–21.5] %/h, respectively, versus 12.6 [3.2–18.8] %/h in injured, untreated controls), improved oxygenation and decreased alveolar inflammation and histological evidence of tissue injury after acid-induced ARDS. RAGE inhibition also restored lung mRNA expression of α1-Na,K-ATPase and AQP-5.InterpretationRAGE inhibition restored AFC and attenuated lung injury in a piglet model of acid-induced ARDS.FundingAuvergne Regional Council, Agence Nationale de la Recherche, Direction Générale de l’Offre de Soins.Research in ContextEvidence before this studyThe acute respiratory distress syndrome (ARDS), a clinical syndrome of diffuse pulmonary oedema and inflammation, currently lacks effective therapies and is associated with high mortality and morbidity. The degrees of lung epithelial injury and of alveolar fluid clearance (AFC) impairment, as evaluated by plasma levels of soluble receptor for glycation end-products (RAGE), are major prognostic factors in ARDS and potential therapeutic targets for ongoing research. For example, targeting RAGE with recombinant sRAGE or an anti-RAGE monoclonal antibody has proven beneficial in a translational mouse model of acid-induced ARDS.Added value of this studyIn a piglet model of acid-induced ARDS, treatment with RAGE antagonist peptide or recombinant sRAGE restored AFC and attenuated the features of lung injury, thereby confirming, in the closest evolutionary model species to humans, previous evidence from rodent models that modulation of RAGE may be a therapeutic option for ARDS. Although this is an important step towards future clinical translation, future studies should assess the best methods to modulate RAGE and further confirm the safety of manipulating this pathway in patients with ARDS.
Focusing on the alveolar epithelium: Alveolar fluid clearance in diffuse versus focal acute respiratory distress syndrome
