Management of Acute Lung Injury: Palmitoylethanolamide as a New Approach

Abstract

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. Lipopolysaccharide (LPS) is usually used intratracheally to induce ALI in mice. The aim of this study was to examine the effects of an ultramicronized preparation of palmitoylethanolamide (um-PEA) in mice subjected to LPS-induced ALI. Histopathological analysis reveals that um-PEA reduced alteration in lung after LPS intratracheal administration. Besides, um-PEA decreased wet/dry weight ratio and myeloperoxidase, a marker of neutrophils infiltration, macrophages and total immune cells number and mast cells degranulation in lung. Moreover, um-PEA could also decrease cytokines release of interleukin (IL)-6, interleukin (IL)-1β, tumor necrosis factor (TNF)-α and interleukin (IL)-18. Furthermore, um-PEA significantly inhibited the phosphorylation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation in ALI, and at the same time decreased extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38/MAPK) expression, that was increased after LPS administration. Our study suggested that um-PEA contrasted LPS-induced ALI, exerting its potential role as an adjuvant anti-inflammatory therapeutic for treating lung injury, maybe also by p38/NF-κB pathway.

Keywords: acute lung injury; cytokines; inflammation; palmitoylethanolamide; ultramicronized.

Figure 1

The effects of um-PEA on histological damage after LPS i.t. injection. Histological analysis was evaluated in sham (A), sham + um-PEA (B), LPS (C), LPS + um-PEA (D) groups. Lung inflammation scores were assessed from 0 to 5 points for all of the following parameters: alveolar congestion, hemorrhage, infiltration or aggregation of neutrophils in airspace or vessel wall, and thickness of alveolar wall/hyaline membrane formation (E), lung edema (W/D) (F) and MPO activity (G). Images are figurative of at least three independent experiments. Values = means ± SEM of six animals in each group; *** p < 0.001 vs. sham; ### p < 0.001 vs. LPS.

Figure 2

Effect of um-PEA on cell infiltration and proinflammatory cytokine expression in BALF: total cells (A); macrophages (B) and neutrophils (C); IL-6 (D); IL-1β (E); TNF-α (F) and IL-18 (G) levels in BALF. Values = mean ± SEM of six animals in each group; *** p < 0.001 vs. sham, ## p < 0.01 vs. LPS and ### p < 0.001 vs. LPS.

Figure 3

The presence of mast cells is indicated by toluidine blue staining: Sham (A), LPS (B), LPS + um-PEA (C); mast cell count (D) in lungs. Figures are representative of at least 3 independent experiments. Values are means SEM of 6 animals for each group; *** p < 0.001 vs. sham, ### p < 0.001 vs. LPS.

Figure 4

Effect of um-PEA on chymase: Sham (A), LPS (B), LPS+um-PEA (C) for image 10× magnification, and Sham (D), LPS (E), LPS+um-PEA (F) for 40× magnification in lungs. The results are expressed as % of positive pixels (G). Images are figurative of at least three independent experiments. Values = means ± SEM of six animals in each group; *** p < 0.001 vs. sham, ### p < 0.001 vs. LPS.

Figure 5

Effect of um-PEA on tryptase: Sham (A), LPS (B), LPS+um-PEA (C) for image 10× magnification, and Sham (D), LPS (E), LPS + um-PEA (F) for 40× magnification in lungs. The results are expressed as % of positive pixels (G). Images are figurative of at least three independent experiments. Values = means ± SEM of six animals in each group; *** p < 0.001 vs. sham, ### p < 0.001 vs. LPS.

Figure 6

Western blots for IKB-α, NF-kB, pJNK, pERK1/2 and p38MAPK, (A). Representative Western blots for cytoplasmic IKB-α degradation (A,B), nuclear NF-κB translocation (A,C), cytoplasmic pJNK (A,D), cytoplasmic pERK1/2 (A,E) and cytoplasmic p-p38 (A,F). A demonstrative blot of lysates (six animals/group) with a densitometric analysis for all animals is shown. The results in (B–F) correspond to means ± SEM of six animals in each group; *** p < 0.01 vs. sham, ### p < 0.001 vs. LPS.