Shock/Sepsis/Trauma/Critical Care
BML-111 attenuates acute lung injury in endotoxemic mice

https://doi.org/10.1016/j.jss.2015.09.005Get rights and content

Abstract

Background

BML-111 is a lipoxin receptor agonist that has protective effects in various lung injury models. We tried to elucidate whether BML-111 could mitigate lung injury in a mouse model of endotoxemia and endothelial hyperpermeability in vitro.

Methods

The effect of BML-111 on lung injury was evaluated using C57BL/6 mice and human umbilical vein endothelial cells (HUVECs). Male C57BL/6 mice were intraperitoneally injected with normal saline, BML-111, and/or the lipoxin receptor antagonist Boc-2. Then, either lipopolysaccharide (LPS) or normal saline was given intraperitoneally. Lung injury was assessed by a pathohistologic examination for neutrophil infiltration, pulmonary endothelial permeability, and inflammatory cytokines in lung tissue and bronchoalveolar lavage fluid. HUVECs were treated with or without BML-111 before incubation with LPS for 24 h. Boc-2 was also tested as a novel inhibitor of BML-111. A Transwell assay was used to evaluate the permeability of HUVECs. Junction protein expression was also assessed.

Results

BML-111 significantly improved the mouse survival rate, reduced body weight loss, attenuated the pulmonary pathologic changes, inhibited neutrophil infiltration and proinflammatory cytokine production, and mitigated endothelial hyperpermeability. The decreased expression of junction proteins induced by LPS in lung tissue and endothelial cells were upregulated by BML-111. In addition, BML-111 inhibited the activation of the Akt, ERK1/2, and p38 MAPK signaling pathways. However, the beneficial effects of BML-111 were abolished by Boc-2.

Conclusions

BML-111 attenuated lung injury in endotoxemic mice and mitigated endothelial hyperpermeability by upregulating the expression of junction proteins.

Introduction

Acute lung injury (ALI), or acute respiratory distress syndrome, is a clinical syndrome associated with respiratory dysfunction. It is a complication of sepsis and has a ∼50% mortality rate [1]. The administration of lipopolysaccharide (LPS), a gram-negative bacterial endotoxin, has been used as a model of sepsis-related lung injury in different studies [2], [3].

The endothelium plays a critical role in the pathophysiology of systemic inflammation, regulating cellular trafficking, maintaining blood fluidity, contributing to the local balance in pro- and anti-inflammatory mediators, participating in generation of new blood vessels, and undergoing programmed cell death [4]. The importance of endothelial barriers, which separate blood and air in the lung and increase vascular permeability in pulmonary edema, in ALI has been well established [5]. Endothelial cell junctions present a particularly complex network of adhesion proteins that are linked to the intracellular cytoskeleton and signaling partners. These proteins are organized into distinct structures called tight junctions (TJs) and adherens junctions (AJs) [6]. Defects in the organization of endothelial cell junctions are associated with many disease pathologies, such as vascular malformations, hemorrhage, and tissue edema. Thus, maintaining the endothelial cell junctions would be an effective therapeutic strategy for ALI in endotoxemic mice.

Lipoxins (LXs) are the first recognized lipid mediators. They have unique structures that are derived from arachidonic acid and dual anti-inflammatory and proresolution activities [7]. Proresolving mediators, such as LX and maresin 1, have been demonstrated to have protective effects in many inflammatory and organ-specific disease models, such as brain ischemia–reperfusion injury [8], [9], colitis [10], ALI [11], asthma [12], and so on. BML-111 (Fig. 1) is a stable biosynthesized agonist of the LXs receptor (formyl peptide receptor-2) [13] and displays proresolving and anti-inflammatory effects in carbon tetrachloride–induced liver injury [14], hemorrhagic shock–induced ALI [15], and ventilator-induced lung injury [16].

However, the protective effects of BML-111 in lung injury in a mouse model of endotoxemia remain unknown. To elucidate these effects, we carried out the present study with the hypothesis that BML-111 would mitigate lung injury in endotoxemic mice and alleviate endothelial hyperpermeability in vitro.

Section snippets

Animals

Two hundred male C57BL/6 mice (8–10-wk-old, 20–25 g) were purchased from Wuhan University Laboratory Center (Wuhan, China). All the animal experiments were approved by the Animal Care and Use Committee of Tongji Medical College of Huazhong University of Science and Technology. All the animal studies have been reported in accordance with the animal research: reporting in vivo experiments guidelines for reporting experiments involving animals [17]. Mice were maintained in a pathogen-free room.

BML-111 improved the survival rate and maintained the body weight

The severity of endotoxemia in this mouse model was evaluated by measuring the survival rate and rate of body weight loss. As shown in Figure 2A, the survival rate in the Control and BML-111 group was 100% at day 7. The mice in the BML-111 + LPS group had a lower survival rate at 37.5% compared with the mice in the LPS and Boc-2 groups, which displayed 0% survival at day 2 and day 3, respectively. Compared with the Control group, the body weight of the mice in the LPS group was significantly

Discussion

Female mice express a higher level of estrogen than male mice, and estrogen exerts a lung protection effect in different lung injury models [21], [22]. To eliminate the effect of estrogen and focus on the potential effect of BML-111 in this study, we chose a model of ALI in endotoxemic male mice. Our findings indicate that the administration of BML-111 in endotoxemic mice significantly prolonged survival, attenuated the histologic damage of the lung, reduced pulmonary proinflammatory cytokines

Conclusions

In summary, our findings demonstrated that BML-111 attenuated lung injury and alleviated endothelial hyperpermeability by upregulating the expression of endothelial cell junction proteins. The pretreatment of BML-111 in this study restricts its clinical translation, but our data still indicated that BML-111 could be a useful chemical reagent for the development of a new therapy for treating LPS-induced ALI.

Acknowledgment

This study was supported by grants from the National Natural Science Foundation of China (no. 30930089, 81372036, 81171790) and Key Clinical Project of Ministry of Health of China (2012-47).

Authors' contributions: M.T. and L.C. performed the research and wrote the article. B.L. and Y.W. made substantial contributions to the animal experiment. S.L. and A.W. performed the in vitro study and analyzed the data. S.Y. and Y.S. designed the experiment and revised the article.

References (35)

  • S.C. Su et al.

    Annexin 2 regulates endothelial morphogenesis by controlling AKT activation and junctional integrity

    J Biol Chem

    (2010)
  • C.Y. Wang et al.

    One-year mortality and predictors of death among hospital survivors of acute respiratory distress syndrome

    Intensive Care Med

    (2014)
  • M. Bucher et al.

    Endothelin-receptor gene-expression in rat endotoxemia

    Intensive Care Med

    (2002)
  • E. Dejana et al.

    The role of adherens junctions and VE-cadherin in the control of vascular permeability

    J Cell Sci

    (2008)
  • C.N. Serhan et al.

    Resolving inflammation: dual anti-inflammatory and pro-resolution lipid mediators

    Nat Rev Immunol

    (2008)
  • Y. Wu et al.

    A lipoxin A4 analog ameliorates blood-brain barrier dysfunction and reduces MMP-9 expression in a rat model of focal cerebral ischemia-reperfusion injury

    J Mol Neurosci

    (2012)
  • S. Fiorucci et al.

    A beta-oxidation-resistant lipoxin A4 analog treats hapten-induced colitis by attenuating inflammation and immune dysfunction

    Proc Natl Acad Sci U S A

    (2004)
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    M.T. and L.C. made equal contribution to this work.

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