Impact of synthetic surfactant CHF5633 with SP-B and SP-C analogues on lung function and inflammation in rabbit model of acute respiratory distress syndrome

Abstract

Acute respiratory distress syndrome (ARDS) is associated with diffuse inflammation, alveolar epithelial damage, and leakage of plasma proteins into the alveolar space, which together contribute to inactivation of pulmonary surfactant and respiratory failure. Exogenous surfactant delivery is therefore considered to hold potential for ARDS treatment, but clinical trials with natural derived surfactant or synthetic surfactant containing a surfactant protein C (SP-C) analogue have been negative. Synthetic surfactant CHF5633, containing analogues of SP-B and SP-C, may be effective against ARDS. The aim here was to compare treatment effects of CHF5633 and animal-derived surfactant poractant alfa in animal model of ARDS. ARDS was induced in adult New Zealand rabbits by mild lung lavages followed by injurious ventilation until respiratory failure (P/F ratio <26.7 kPa). The animals were then treated with intratracheal bolus of 200 mg/kg CHF5633 or poractant alfa (Curosurf^® ), or air as control. The animals were subsequently ventilated for an additional 4 hr and respiratory parameters were recorded regularly. Postmortem, histological analysis, degree of lung edema, and levels of the cytokines TNFα, IL-6, and IL-8 in lung homogenates were evaluated. Both surfactant preparations improved lung function, reduced the levels of pro-inflammatory cytokines, and degree of lung edema to very similar degrees versus the controls. No significant differences in any of the analyzed parameters were observed between the CHF5633- and poractant alfa-treated groups. This study indicates that single dose of CHF5633 improves lung function and attenuates inflammation as effectively as poractant alfa in experimental ARDS caused by injurious ventilation.

Keywords: ARDS model; CHF5633; inflammation; lung function; synthetic pulmonary surfactant.

FIGURE 1

Respiratory parameters. (a) The ratio of arterial oxygen partial pressure to fraction of inspired oxygen (P/F, kPa), (b) oxygenation index (OI), (c) alveolar–arterial gradient (AaG, kPa) before (basal value, BV), at established ARDS, and during 4 hours after administration of surfactant therapy (marked with an arrow head). Data are presented as mean ±SD. Statistical comparisons: α for poractant alfa and β for CHF5633 represent p < 0.001 and βi for CHF5633 represent p < 0.01 vs. Control

FIGURE 2

Inflammatory markers. Concentrations of cytokines (a) TNFα, (b) IL‐6, and (c) IL‐8 (all in pg/mL) in right and left lung tissue homogenates of untreated control group, and groups treated with poractant alfa or CHF5633 surfactant. Data are presented as individual values with mean ±SD. Statistical comparisons: for poractant alfa and CHF5633 vs. control *p < 0.05, **p < 0.01, ***p < 0.001

FIGURE 3

Histological analysis. Lung sections of untreated control group (a, a1), group treated with poractant alfa (b, b1), or CHF5633 surfactant (c, c1); total inflammation score (d), total atelectasis score (e), and inflammation score in apical, medial, and caudal regions of lungs (f). In control group, the pulmonary parenchyma displays a diffuse inflammatory cell infiltrate in alveoli and collapsed alveoli. Two bronchioles with prominent bronchial‐associated lymphoid tissue and small‐sized arteriole with a perivascular inflammatory cell infiltrate are observed (a). Alveoli with inflammation display numerous polymorphs, predominantly neutrophils and also some macrophages. Alveolar septa are markedly thickened with membranous deposits of eosinophilic proteinaceous material (a1). In the poractant alfa‐treated group, leukocytes are not visible at low power. The lung shows normal appearance, and consolidated areas are not observed (b). The central part shows membranous deposits of eosinophilic material in the alveolar septa. Scattered polymorphs also are visible (b1). In the CHF5633 treatment group, the pulmonary parenchyma shows normal alveoli with thin septa, and consolidated areas are not visible (c). The arteriole displays intravascular leukocytes, predominantly polymorphs, some of which adhere at the vascular endothelium. The pulmonary parenchyma is normal, with an occasional macrophage in the alveolar lumen (c1). The scale bars represent 200 μm in pictures a, b, and c and 50 μm in a1, b1, and c1. Data are presented as individual values with mean ±SD. Statistical comparisons: for poractant alfa and CHF5633 vs. control *p < 0.05, **p < 0.01, ***p < 0.001

FIGURE 4

Lung edema formation. (a) Total lung edema expressed as wet‐dry (W/D) lung weight ratio, (b) W/D of apical, medial, and caudal regions of lungs of untreated control group, and groups treated with poractant alfa or CHF5633 surfactant. Data are presented as individual values with mean ±SD. Statistical comparisons: for poractant alfa and CHF5633 vs. control *p < 0.05, **p < 0.01, ***p < 0.001