Unfractionated Heparin Alleviates Sepsis-Induced Acute Lung Injury by Protecting Tight Junctions.

Background: Unfractionated heparin (UFH) has been shown to ameliorate lung edema and lung vascular leakage in lipopolysaccharide-induced lung injury. Impaired tight junction (TJ) function is a sign of sepsis-induced acute respiratory distress syndrome (ARDS) and acute lung injury (ALI), which is closely related to the downregulated expression of TJ-specific proteins or the upregulated expression of inflammatory cytokines. Because UFH has been intensively studied in modulating inflammation, we hypothesize that UFH may play a positive role in treating sepsis-induced ARDS/ALI by protecting TJs.
Material and Methods: Rat sepsis-induced lung injury was induced by cecal ligation and puncture and treated with UFH. Hematoxylin and eosin staining, lung wet/dry weight (W/D) ratio, and pulmonary microvascular leakage were evaluated to assess lung injury. Cytokines in bronchoalveolar lavage fluid were detected to determine lung inflammation. A transendothelial electrical resistance assay, a Transwell permeability assay, and transmission electron microscopy were used to study endothelial TJs in human lung microvascular endothelial cells. TJ protein expression was measured by western blotting or immunohistochemistry.
Results: UFH treatment alleviated lung injury in vivo by reducing IL-6 in bronchoalveolar lavage fluid and protecting TJs in LMVECs. UFH also protected TJs against lipopolysaccharide-stimulated damage and functioned upstream by inhibiting the ERK1/2 MAPK pathway to attenuate endothelial hyperpermeability and downregulating the expression of TJ proteins such as claudin-5, occludin, and ZO-1.
Conclusions: These findings suggested that UFH has therapeutic potential for sepsis-induced ARDS or ALI through protecting TJs in LMVECs.
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