Elsevier

Nutrition

Volume 29, Issue 1, January 2013, Pages 244-249
Nutrition

Basic nutritional investigation
Onion (Allium cepa) extract attenuates brain edema

https://doi.org/10.1016/j.nut.2012.02.017Get rights and content

Abstract

Objective

This study investigated the potential beneficial effects of onion extract on brain ischemia-induced edema and blood-brain barrier (BBB) dysfunction. The possible underlying mechanisms are investigated, especially those linked to the antioxidant effects of the onion extract.

Methods

Brain ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion in mice. Mice were treated intravenously with onion extract 30 min before MCAO. Brain edema and BBB hyperpermeability were evaluated by the measurement of the brain water content and Evans blue extravasation, respectively. The disruption of tight junction proteins was examined by immunohistochemical staining. The level of malondialdehyde was determined using the thiobarbituric acid method. The activities of glutathione peroxidase and catalase were determined by spectrophotometric assay.

Results

Brain water content in the ischemic hemisphere was significantly reduced by treatment with onion extract. Onion extract also had a significant effect on both the decrease in Evans blue extravasation and the inhibition of zonula occludens-1 and occludin disruption caused by brain ischemia. In addition, onion extract significantly prevented brain ischemia-induced reduction in catalase and glutathione peroxidase activities and elevation of malondialdehyde level in the brain tissue.

Conclusion

The results from this study demonstrate that onion extract prevents brain edema, BBB hyperpermeability, and tight junction proteins disruption, possibly through its antioxidant effects in the mouse MCAO model. This study suggests that onion extract may be a beneficial nutrient for the prevention of BBB function during brain ischemia.

Introduction

The blood-brain barrier (BBB) is a physical and metabolic barrier between the brain blood circulation and the central nervous system [1]. The proper functioning of the BBB is critical for maintaining brain homeostasis and protecting against many toxic compounds and pathogens [2], [3], [4]. During cerebral ischemia, BBB disruption is a critical event that induces an influx of water, leading to vasogenic edema [5], and causes secondary brain damage such as dementia through accumulation of β-amyloid peptide [6]. Brain edema aggravates the progression of infarct formation and causes herniation and death [7].

It has been reported that reactive oxygen species (ROS) exert deleterious actions, such as BBB disruption and BBB hyperpermeability, during vasogenic edema [8], [9]. Several studies have demonstrated that inhibition of ROS can attenuate brain edema and BBB disruption under various pathologic conditions including ischemia [8], [10], [11]. In addition, inhibition of ROS protects TJs against disruption during brain injury [12]. Moreover, amelioration of ischemia-induced BBB disruption and brain edema has also been demonstrated by using dietary antioxidants such as ginkgo biloba extract and olive leaf extract [13], [14], [15].

Onion (Allium cepa L.), one of the most widely consumed vegetables [16], is an important source of dietary antioxidants [17]. Various studies have shown that onion is associated with several health benefits such as protection against cardiovascular diseases [18], atherosclerosis [19], and cancer [20]. In addition, onion has a role in the prevention of brain damage such as neuronal death from transient cerebral ischemia [21], [22], [23]. However, to the best of our knowledge, little is known about the effect of onion extract on BBB dysfunction during brain ischemia.

In the present study, we investigated whether onion extract has beneficial effects on brain ischemia-induced edema and BBB dysfunction in mice. The possible underlying mechanisms are also investigated, especially those linked to the antioxidant effects of the onion extract.

Section snippets

Transient brain ischemia model

A total of 150 mice were used in this study. All experiments were performed in accordance with the approved animal protocols and guidelines established by the Ajou University School of Medicine Ethics Review Committee for animal experiments. All experiments were performed on male Institute of Cancer Research (ICR) mice weighing 30-35 g housed under a controlled temperature and humidity. ICR mice were purchased from Daehan Biolink (Eumseong, Korea). ICR mice (8 wk old) were anesthetized with

The effects of onion extract on water content in mouse brain ischemia model

In our previous rat study [29], [30] and the preliminary mouse study, we observed brain edema and BBB dysfunction at different time points after MCAO and found 24 h of reperfusion after MCAO as optimum injury time. Therefore, we chose 24 h of reperfusion in this study.

To measure the effects of onion extract on brain edema in the mouse brain ischemia model, we examined the brain water content using a wet-dry method at 24 h of reperfusion. As shown in Fig. 1, water content was greater in ischemic

Discussion

This study demonstrates that onion extract attenuates brain edema, BBB hyperpermeability, and TJs disruption, at least partially, through antioxidant effects in the mouse MCAO model. Brain edema has a crucial impact on morbidity and mortality after cerebral ischemia [6], [32]. It has been reported that the majority of cerebral ischemia-induced brain injuries are related to the disruption of the BBB, which results in edema and secondary damage such as dementia and herniation [6], [33], [34].

Conclusion

In recent years, there has been growing interest in natural substances and their presumed role in the prevention of various diseases [18], [49]. In addition, natural substances may have fewer side effects than do pharmaceuticals [50] and are easily available without prescriptions. Hence, the present study may provide extra motivation for the consumption of onions. The results from this study suggest that onion extract may be a beneficial nutrient for the prevention of ischemic BBB damage, and

Acknowledgments

This work was carried out with the support of “Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ005453)” Rural Development Administration, Republic of Korea. This research was also supported by Technology Development Program for Bio-industry, Ministry for Food, Agriculture, Forestry and Fisheries, Republic of Korea.

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