Diphlorethohydroxycarmalol, isolated from the brown algae Ishige okamurae, protects against radiation-induced cell damage in mice

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Abstract

The aim of this study was to evaluate the radioprotective effects of diphlorethohydroxycarmalol (DPHC), isolated from the brown algae Ishige okamurae, in mice subjected to gamma irradiation.

DPHC significantly decreased the level of radiation-induced intracellular reactive oxygen species in cultured Chinese hamster lung fibroblast (V79-4) cells (p < 0.05), enhanced cell viability that decreased after exposure to γ-rays, and reduced radiation-induced apoptosis in the V79-4 cells.

Pretreatment with DPHC (100 mg/kg) in mice prior to irradiation significantly protected the intestinal crypt cells in the jejunum (p < 0.01) and maintained villi height (p < 0.01), compared with those of the vehicle-treated irradiated group. Mice pretreated with DPHC also exhibited dose-dependent increases in the bone marrow cell viability. The dose-reduction factor for gamma irradiation in the DPHC-pretreated mice was 2.05 at 3.5 days after irradiation.

These results suggest that DHPC plays a role in protecting cells from irradiation-induced apoptosis, through the scavenging of reactive oxygen species in vitro, and that DPHC significantly protected intestinal progenitor cells and bone marrows cells that were decreased by gamma irradiation in vivo.

Introduction

Ishige okamurae (Phylum Phaeophyta, Class Phaeophyceae, Order Chordariales, Family Ishigeaceae), an edible brown algae, has been collected from the coast of Jeju island, Korea (Lee and Kang, 1986). Recently, an ethanolic extract of I. okamurae was shown to have anti-inflammatory effects via the inhibition of nuclear factor kappa B (NF-κB) (Kim et al., 2009). Diphlorethohydroxycarmalol (DPHC), a phlorotannin isolated from I. okamurae, has been shown to have a variety of biological effects, including antioxidant effects (Heo et al., 2008, Zou et al., 2008), anti-viral effects (Ahn et al., 2006), and hypoglycemic effects (Heo et al., 2009). The biological activities of DPHC, described above, prompted us to examine its use in various types of inflammatory conditions, including radiation injury.

Irradiation has been widely used for the treatment of cancers, but the side effects reduce the patients’ quality of life, due to hematopoietic or gastrointestinal injury, apoptosis, and mutagenesis (Rzeszowska-Wolny et al., 2009). In the presence of H2O in organism, ionizing radiation including gamma ray leads to formation of reactive oxygen species such as superoxide anion, hydrogen peroxide, hydroxyl radical, and singlet oxygen (Hall et al., 1988). Because reactive oxygen species generated by ionizing radiation damages radiosensitive cells, leading to apoptosis (Moon et al., 2008, Potten and Grant, 1998, Weil et al., 1996), protection of tissues and cells, including intestinal progenitor cells, is an important issue in radiotherapy (Conklin and Walker, 1987, Hall et al., 1988, Weiss and Landauer, 2003).

The search for synthetic or natural compounds that can protect cells against ionizing irradiation is an important topic in radioprotection studies; radiation-induced cellular injury is linked to apoptosis, via oxidative injury, particularly in the proliferating progenitor cells in the small intestine and bone marrow (Moon et al., 2008, Weil et al., 1996). Many compounds with anti-oxidative and anti-inflammatory activities are known to be associated with radioprotection (Weiss and Landauer, 2003).

Recently, compounds from natural seaweed products, including fucoidan (Lee et al., 2008), phloroglucinol (Kang et al., 2010), triphlorethol-A (Kang et al., 2006), and eckol (Moon et al., 2008, Park et al., 2008) have been examined as radioprotectors because they are thought to be less toxic than synthetic peptides or amifostine (Santini and Giles, 1999, Weiss and Landauer, 2003).

The aim of this study was to evaluate the in vivo radioprotective effects of DPHC isolated from I. okamurae in mice after acute gamma irradiation.

Section snippets

Animals

BALB/c mice were purchased (Orient Bio, Gyunggi-do, Korea) and bred in our animal facility. Mice of both sexes, aged 8–12 weeks, were used. All experimental procedures were conducted in accordance with the Guidelines for the Care and Use of Laboratory Animals at Jeju National University. The experimental groups consisted of normal controls, the DPHC-only-treated group, the vehicle-treated irradiation group, and the DPHC-treated irradiation group.

Reagents and instruments

All solvents were of analytical grade. 1H (500 MHz)

DPHC scavenges ROS generated by γ-rays

The radical scavenging effect of DPHC (Fig. 2) on ROS generated by γ-rays was measured at 48 h after radiation exposure. As shown in Fig. 2, the level of ROS detected with a spectrofluorometer decreased in DPHC-treated irradiated cells, compared with the ROS level in irradiated cells (Fig. 2). These findings suggest that DPHC scavenges ROS generated by γ-rays.

DPHC protects cells against apoptosis induced by γ-rays

To investigate whether the protective effect of DPHC against cellular components damaged by γ-rays was associated with cell survival, the

Discussion

This study confirmed that DPHC, a compound from I. okamurae, has a radioprotective effect on whole-body gamma-ray irradiation in mice. Irradiation injury is known to be associated with the activation of pro-inflammatory mediators and increased oxidative stress (Ha et al., 2010), which induce cell death, particularly in proliferating cells. Thus, many antioxidants have been studied as candidates for radioprotective agents (Weiss and Landauer, 2003).

In the present study, DPHC demonstrated

Conflict of Interest

Some parts of this work were used for a patent application in the Republic of Korea (patent application number: 10-2010-0077439). All authors agree to the patent application and do not have any other competing interests.

Acknowledgements

This research was performed under the program of the Basic Atomic Energy Research Institute (BAERI), which is part of the Nuclear R&D Programs of the National Research Foundation, funded by the Ministry of Education, Science & Technology of Korea.

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    These authors contributed equally to this work.

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