Inhibition of the Receptor for Advanced Glycation End-Products in Acute Respiratory Distress Syndrome: A Randomised Laboratory Trial in Piglets

Abstract

The receptor for advanced glycation end-products (RAGE) modulates the pathogenesis of acute respiratory distress syndrome (ARDS). RAGE inhibition attenuated lung injury and restored alveolar fluid clearance (AFC) in a mouse model of ARDS. However, clinical translation will require assessment of this strategy in larger animals. Forty-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), or (iii) recombinant soluble (s)RAGE. The primary outcome was net AFC at 4 h. Arterial oxygenation was assessed hourly and alveolar-capillary permeability, alveolar inflammation and lung histology were assessed at 4 h. Treatment with either RAP or sRAGE improved net AFC (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), oxygenation and decreased alveolar inflammation and histological evidence of tissue injury after ARDS. These findings suggest that RAGE inhibition restored AFC and attenuated lung injury in a piglet model of acid-induced ARDS.

Figure 1

RAGE inhibition restores alveolar fluid clearance after acid-induced lung injury. Measurement of net alveolar fluid clearance (AFC) rate as a marker of epithelial function in uninjured (Sham), acid-injured (HCl) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group at each time point). Values are reported as box and whisker plots. The Kruskal-Wallis test, with post-hoc Bonferroni test for pairwise comparisons were used. P = 0.02 for the overall multiple group test; no statistical difference was found in post-hoc tests.

Figure 2

RAGE inhibition improves arterial oxygenation after acid-induced lung injury. Arterial oxygen tension (PaO₂)/inspiratory oxygen fraction (FiO₂) in uninjured (Sham), acid-injured (HCl) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group at each time point). Individual values are reported. Time × group interaction and post-hoc comparisons were verified using random effects models to analyse longitudinal evolution of variables.

Figure 3

RAGE inhibition decreases alveolar-capillary permeability after acid-induced lung injury. Values are reported as box and whisker plots. (A) Level of total protein in the bronchoalveolar lavage (BAL) fluid from uninjured (Sham), acid-injured (HCl) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group). The Kruskal-Wallis test, with post-hoc Bonferroni test for pairwise comparisons were used. (B) Extravascular lung water, as measured by transpulmonary thermodilution (Picco + , Pulsion SA) and indexed to body weight, in uninjured (Sham), acid-injured (HCl) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group at each time point). Time × group interaction and post-hoc comparisons were verified using random effects models to analyse longitudinal evolution of variables.

Figure 4

RAGE inhibition decreases alveolar inflammation after acid-induced lung injury. Measurement of bronchoalveolar lavage (BAL) levels of (A) tumour necrosis factor (TNF)-α, (B) interleukin (IL)-6, (C) IL-1β and (D) IL-18 in uninjured (Sham), acid-injured (HCl) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group). Values are reported as box and whisker plots. The Kruskal-Wallis test, with post-hoc Bonferroni test for pairwise comparisons were used.

Figure 5

(A) RAGE inhibition decreases histological features of lung injury. Lung injury scores were higher in acid-injured (HCl) than in uninjured piglets (Sham) and acid-injured piglets treated with RAGE antagonist peptide (HCl + RAP) or recombinant sRAGE (HCl + sRAGE) (n = 12 per group). Values are reported as box and whisker plots. The Kruskal-Wallis test, with post-hoc Bonferroni test for pairwise comparisons were used. (B–E) Representative hematoxylin and eosin–stained sections at x20 original magnification of (B) uninjured piglets (Sham), (C) acid-injured piglets (HCl), acid-injured piglets treated with (D) RAGE antagonist peptide (HCl + RAP) or (E) recombinant sRAGE (HCl + sRAGE). There was greater cellularity consisting mainly of neutrophils (black arrowheads), more alveolar wall thickening (white arrowheads), and more areas of atelectasis and increased alveolar disruption, proteinous debris, and hemorrhage (black arrows) in untreated, acid-injured than in uninjured or treated piglets. Scale bars, 100 µm.