Abstract
BackgroundMethionine sulfoxide reductase A (MsrA) is a potent intracellular oxidoreductase and serves as an essential factor that protects cells against oxidative damage. However, therapeutic use of exogenous MsrA in oxidative stress-induced diseases is limited, because it cannot enter the cells. The aim of this study is to investigate whether MsrA with PEP-1, a cell penetrating peptide, fused to its N-terminus can protect against oxidative stress in macrophages and can attenuate atherosclerosis in apolipoprotein E deficient (apoE−/−) mice.MethodsMsrA and the fusion protein PEP-1-MsrA were expressed and purified using a pET28a expression system. Transduction of the fusion protein into macrophages was confirmed by Western blot and immunofluorescence staining. Intracellular reactive oxygen species (ROS) and apoptosis levels were measured by flow cytometry. In in vivo study, MsrA or PEP-1-MsrA proteins were intraperitoneally injected into apoE−/− mice fed a Western diet for 12 weeks. Plasma lipids levels, inflammatory gene expression, and paraoxonase-1 (PON1) and superoxide dismutase (SOD) activities were assessed. Atherosclerotic lesions were analyzed by Oil Red O staining and immunohistochemistry.ResultsPEP-1-MsrA could penetrate the cells and significantly reduced intracellular ROS levels and apoptosis in H2O2-treated macrophages. It also decreased TNFα and IL-1β mRNA levels and increased the IL-10 mRNA level in lipopolysaccharide-treated macrophages. In in vivo study, PEP-1-MsrA injection significantly increased plasma PON1 and SOD activities and decreased plasma monocyte chemoattractant protein 1 (MCP-1) level compared to the injection of vehicle control or MsrA. In PEP-1-MsrA injected mice, hepatic PON1 levels were increased, while the expression of TNFα and IL-6 mRNA in the liver was suppressed. Although plasma total cholesterol and triglyceride levels did not change, the aortic atherosclerosis in PEP-1-MsrA treated mice was significantly reduced. This was accompanied by a reduction of total and apoptotic macrophages in the lesions.ConclusionOur study provides evidence that PEP-1-MsrA may be a potential therapeutic agent for atherosclerosis-related cardiovascular diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0677-8) contains supplementary material, which is available to authorized users.
Highlights
Methionine sulfoxide reductase A (MsrA) is a potent intracellular oxidoreductase and serves as an essential factor that protects cells against oxidative damage
The goal of this study is to investigate whether the fusion protein PEP-1-MsrA can efficiently enter cells to protect against oxidative stress and to attenuate atherosclerosis in apolipoprotein E deficient mice, providing evidence that PEP-1-MsrA may be a potential therapeutic agent for atherosclerosis-related cardiovascular diseases
We found that plasma PON1 and superoxide dismutase (SOD) activities were significantly increased, while the plasma inflammatory factor monocyte chemoattractant protein 1 (MCP-1) level was decreased in PEP-1-MsrA injected mice compared to the respective levels in control mice or MsrA injected mice (Fig. 4a–c)
Summary
Methionine sulfoxide reductase A (MsrA) is a potent intracellular oxidoreductase and serves as an essential factor that protects cells against oxidative damage. Therapeutic use of exogenous MsrA in oxidative stress-induced diseases is limited, because it cannot enter the cells. The aim of this study is to investigate whether MsrA with PEP-1, a cell penetrating peptide, fused to its N-terminus can protect against oxidative stress in macrophages and can attenuate atherosclerosis in apolipoprotein E deficient (apoE−/−) mice. Cells contain a series of antioxidant defenses such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase that directly detoxify ROS and reduce their effects. There is increasing evidence that a therapeutic approach targeting antioxidant enzymes could decrease the progression of atherosclerosis [7]. Recent studies have demonstrated that MsrA is involved in oxidative stress and age associated diseases [9], and enhanced MsrA might be an important approach for the prevention of many oxidative stress-induced diseases, such as hypoxia/reoxygenation and ischemia/reperfusion injury [10, 11], cataracts [12], diabetes mellitus [13], Alzheimer’s disease [14, 15] and atherosclerosis related coronary artery disease [16, 17]
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