Protective effects of scoparone against lipopolysaccharide-induced acute lung injury

doi:10.1016/j.intimp.2014.08.014

International Immunopharmacology

Volume 23, Issue 1, November 2014, Pages 127-133

https://doi.org/10.1016/j.intimp.2014.08.014 Get rights and content

Highlights

•
Scoparone has a protective effect on LPS-induced ALI.
•
Scoparone inhibits LPS-induced TNF-α, IL-6 and IL-1β production in vivo and in vitro.
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Scoparone inhibits LPS-induced TLR4 expression and NF-κB activation.

Abstract

The purpose of this study was to investigate the protective effects and molecular mechanisms of scoparone on lipopolysaccharide (LPS)-induced acute lung injury in mice. Mice model of acute lung injury (ALI), induced by intranasal instillation of LPS, was used to investigate the protective effects of scoparone in vivo. The alveolar macrophages were used to investigate the molecular mechanisms of scoparone in vitro. The results showed that scoparone treatment remarkably attenuated LPS-induced pulmonary edema, histological severities, myeloperoxidase activity, and TNF-α, IL-6 and IL-1β production in vivo. We also found that scoparone inhibited LPS-induced TLR4 expression, NF-κB activation, TNF-α, IL-6 and IL-1β production in alveolar macrophages in vitro. In conclusion, our results suggest that scoparone has a protective effect on LPS-induced ALI via suppression of TLR4-mediated NF-κB signaling pathways.

Introduction

Acute respiratory distress syndrome (ARDS) is characterized by overwhelming lung inflammation and increased microvascular permeability [1]. ARDS often results in multi-organ failure with high mortality in critically ill patients [2]. Most causes such as sepsis, trauma and burn could induce ARDS and the most common cause of ARDS is sepsis resulting from bacterial infection [3]. Current treatments such as surfactants, glucocorticoids, and stem cells do not significantly reduce lung injury and mortality [4]. Therefore, the developments of new and effective strategies to treat ARDS are urgently needed.

LPS, the outer membrane of gram-negative bacteria, has been reported to be an important risk factor of ALI [5], [6], [7]. LPS stimulates alveolar macrophages to induce TLR4 activation, which finally induces the production of inflammatory cytokines, such as TNF-α, IL-6 and IL-1β [8], [9], [10]. These cytokines amplify the inflammatory responses and lung injury [11]. The pathophysiological mechanism of ARDS is believed to be associated with the uncontrolled inflammatory response in lungs [12]. Nowadays, studies showed that treatments aimed at modulating TLR4 signaling pathway to alleviate inflammatory response may have potential therapeutic advantages for ARDS [13].

Scoparone, a major component of the shoot of Artemisia capillaris, has been reported to have anti-inflammatory and anti-tumor effects [14], [15]. Several studies showed that scoparone inhibited IL-8 and MCP-1 production in U937 cells and TNF-α, IL-6 and IL-1β production in LPS-stimulated RAW264.7 cells [16], [17]. Furthermore, scoparone was found to have a protective effect on d-galactosamine/lipopolysaccharide-induced hepatic failure in mice [18]. However, the anti-inflammatory effect of scoparone on LPS-induced ALI has not been reported. The aim of this study was to investigate the protective effects and molecular mechanisms of scoparone on lipopolysaccharide (LPS)-induced acute lung injury.

Section snippets

Reagents

Scoparone and LPS (Escherichia coli 055:B5) was purchased from Sigma Chemical Co. (St. Louis, MO, USA). Mouse TNF-α, IL-6 and IL-1β assay kits were purchased from R&D Systems (Minneapolis, MN). Anti-pNF-κB p65, anti-NF-κB p65, anti-TLR4, and anti-β-actin monoclonal antibodies were purchased from Santa Cruz Biotechnology Inc (Santa Cruz, CA, USA). All other chemicals were of reagent grade.

Animals

Male BALB/c mice weighing 18–22 g were obtained from the Center of Experimental Animals of Peking University

Effects of scoparone on LPS-induced lung wet/dry weight ratio in mice

As shown in Fig. 1, LPS challenge produced a significant increase in the lung wet/dry weight ratio compared to the control group. Scoparone and DEX significantly reduced the lung wet/dry weight ratio compared to those in the LPS group (P < 0.05).

Effects of scoparone on LPS-mediated lung histopathologic changes

Lung histological changes were detected in this study. As shown in Fig. 2A, normal pulmonary histology was seen in the control group. Lung tissues from LPS group were significantly damaged, including interstitial edema, hyperemia, thickening of the

Discussion

The acute respiratory distress syndrome is an important cause of acute respiratory failure that is characterized by overwhelming lung inflammation [20]. Scoparone, a major component of the shoot of Artemisia capillaris, has been reported to have anti-inflammatory effects [16], [17]. In this study we found that scoparone had a protective effect on LPS-induced ALI. The anti-inflammatory mechanism of scoparone is by suppression of TLR4-mediated NF-κB signaling pathways.

Excessive neutrophil

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Subsequently, nuclear factor kappa B (NF-κB) signaling transduction pathway is activated, stimulating releases of inflammatory cytokines and chemokines (TNF-α, IL-6, IL-1β, MIP-2) (Dolinay et al., 2012), which could recruit inflammatory cells (neutrophils and macrophages) to initiate inflammatory process (Togbe et al., 2007). Meanwhile, it has been reported that NF-κB activation would up-regulate MMP-9 expression in the pathogenesis of ALI (Niu et al., 2014). MMP-9, a calcium- and zinc-dependent endoproteinase, is released from activated neutrophils and contributes to the degradation of capillaries and alveolar epithelial basement membrane (Hoffmann et al., 2006), resulting in extensive alterations of lung architecture and eventually amplifying airways inflammation (Hoshino et al., 1998).
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Protective effects of scoparone against lipopolysaccharide-induced acute lung injury

Highlights

Abstract

Introduction

Section snippets

Reagents

Animals

Effects of scoparone on LPS-induced lung wet/dry weight ratio in mice

Effects of scoparone on LPS-mediated lung histopathologic changes

Discussion

Biochem Pharmacol

Biochem Pharmacol

Biochem Pharmacol

Biochem Pharmacol

J Lipid Res

J Lipid Res

Life Sci

Food Chem Toxicol

J Pharmacol Toxicol Methods

Life Sci

J Lipid Res

Pharmacol Ther

J Lipid Res

J Lipid Res

Biochem Pharmacol

Mechanisms of acute lung injury/acute respiratory distress syndrome

Clin Chest Med

Acute respiratory distress syndrome in critically ill patients with severe acute respiratory syndrome

JAMA