Anti-inflammatory mechanism of simvastatin in mouse allergic asthma model

https://doi.org/10.1016/j.ejphar.2006.11.027Get rights and content

Abstract

Statins have anti-inflammatory property and immunomodulatory activity. In this study we aimed to investigate the inhibitory mechanism of simvastatin in allergic asthmatic symptoms in mice. BALB/c mice were sensitized and challenged by ovalbumin to induce asthma. Ovalbumin-specific serum IgE levels were measured by enzyme-linked immunosorbent assay (ELISA), and the recruitment of inflammatory cells into bronchoalveolar lavage fluid or lung tissues was measured by Diff-Quik staining and hematoxylin and eosin (H&E) staining, respectively, the expressions of CD40, CD40 ligand (CD40L), and vascular cell adhesion molecule-1 (VCAM-1) by immunohistochemistry, the mRNA and protein expressions of cytokines in lung tissues by reverse transcriptase-polymerase chain reaction (RT-PCR) or ELISA, epithelial hyperplasia by periodic acid-Schiff (PAS) staining, activities of matrix metalloproteinases (MMPs) by zymography, the activities of small G proteins, mitogen-activated protein (MAP) kinases and nuclear factor-kappa B (NF-κB) in bronchoalveolar lavage cells and lung tissues by western blot and EMSA, respectively. Simvastatin reduced ovalbumin-specific IgE level, the number of total inflammatory cells, macrophages, neutrophils, and eosinophils into bronchoalveolar lavage fluid, the expressions of CD40, CD40L or VCAM-1, the mRNA and protein levels of interleukin (IL)-4, IL-13 and tumor necrosis factor (TNF)-α, the numbers of goblet cells, activities of MMPs, and further small G proteins, MAP kinases and NF-κB activities in bronchoalveolar lavage cells and lung tissues increased in ovalbumin-induced allergic asthma in mice. Our data suggest that simvastatin may be used as a therapeutic agent in asthma, based on reductions of various allergic responses via regulating small G proteins/MAP kinases/NF-κB in mouse allergic asthma.

Introduction

Statins, such as atorvastatin, cerivastatin, fluvastatin, pravastatin, lovastatin, and simvastatin, are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in cholesterol biosynthesis and have numerous beneficial pleiotropic effects. Because they are known to reduce atherogenesis and cardiovascular morbidity, they have also been used as cholesterol lowering agents in coronary artery disease (Albert et al., 2001, Joukhadar et al., 2001, Shepherd et al., 1995). It has also been reported that statins have anti-inflammatory property independent of plasma cholesterol lowering (Crisby et al., 2001, Joukhadar et al., 2001, Sparrow et al., 2001) and immunomodulatory activities (Takemoto and Liao, 2001).

Although the mechanism underlying the anti-inflammatory action of statins is not known, it may involve the inhibition of a variety of inflammatory intermediate substances called isoprenoids, which are formed during the endogenous biosynthesis of cholesterol. Statins inhibit the interaction between cellular adhesion molecules, such as lymphocyte function-associated antigen (LFA)-1, and intracellular adhesion molecule (ICAM)-1 (Weitz-Schmidt et al., 2001). More recently, it has been reported that simvastatin reduces the secretion of inflammatory cytokines, but does not alter serum total IgE or ovalbumin-specific IgG1 and IgG2a levels in allergic asthma mouse model (McKay et al., 2004).

Allergic asthma is a chronic inflammatory disease of the lung characterized by reversible obstruction of airway hyperresponsiveness, infiltration of inflammatory cells into lung tissues, mucus overproduction (Kon and Kay, 1999), the over-expressions of Th2-mediated cytokines including interleukin (IL)-4, IL-5, IL-13 and tumor necrosis factor (TNF)-α, and chemokines such as eotaxin and RANTES in the airways of allergic asthmatics (Berkman et al., 1996, Zimmermann et al., 2003). It has been increasing in prevalence, morbidity, and mortality over the last two decades (Umetsu et al., 2002). Despite the prevalence of this disease, its source and mechanism remain unclear. It has also been reported that inflammatory and structural cells contribute to the increased bronchoconstriction chronically, to airway remodeling. Current asthma therapy does not inhibit these features satisfactorily. Recently, Rho family kinases as a potential drug target were introduced because of increasing evidences which have a central role for this pathway in acute and chronic airway hyperresponsiveness (Blease, 2005, Gosens et al., 2006). These Rho family kinases regulate mitogen-activated protein (MAP) kinases (Hall et al., 2001) and many functions of leukocytes (Ridley, 2001).

As the pathophysiological mechanism mitigating the effects of simvastatin on asthma is not known, we aimed to investigate whether simvastatin reduces ovalbumin-specific allergic asthma symptoms in mice, and to investigate the inhibitory mechanism of simvastatin in ovalbumin-specific allergic asthma.

Section snippets

Sensitization, challenge and experimental protocol

Specific pathogen free female BALB/c mice, 6–8 weeks of age were divided into four groups (8 mice/group). Control, mice sensitized and nebulized with phosphate buffered saline (PBS, negative control); general sensitized mice, mice sensitized with ovalbumin and nebulized with PBS (general sensitization); ovalbumin-challenged mice, mice sensitized and nebulized with ovalbumin (local challenge); simvastatin treatment, ovalbumin-challenged mice treated with simvastatin. Hereafter, we used these

Ovalbumin-specific serum IgE levels

Antigen-specific Th2 responses are known to induce antigen-specific IgE antibody production. Therefore, we examined whether simvastatin influenced ovalbumin-specific IgE production in allergic asthma mouse model using ELISA. Serum ovalbumin-specific IgE levels were elevated in general sensitized mice (156.8 ± 1.27 ng/ml) and ovalbumin-challenged mice (203.0 ± 11.00 ng/ml) versus control mice (0.5 ± 0.23 ng/ml). Simvastatin (150.6 ± 2.39 ng/ml) treated mice showed ovalbumin-specific IgE antibody

Discussion

It is important to understand the pathogenesis of allergic asthma because it is one of the most common diseases encountered in the clinic, and because the mortality associated with allergic asthma has increased worldwide over the last two decades (Umetsu et al., 2002). However, the mechanisms involved have not been completely elucidated. Moreover, there are difficulties in the drug development process because of the limited understanding of molecular pathogenesis of allergic asthma. Therefore,

Acknowledgments

This work was funded by Samsung biomedical Research Institute, Sungkyunkwan University School of Medicine (Grant no. #SBRI S-M 200106).

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