Elsevier

Environmental Pollution

Volume 231, Part 1, December 2017, Pages 301-310
Environmental Pollution

Diallyl trisulfide (DATS) suppresses benzene-induced cytopenia by modulating haematopoietic cell apoptosis

https://doi.org/10.1016/j.envpol.2017.07.069Get rights and content

Highlights

  • The apoptosis of hematopoietic cells induced by benzene may be an important mechanism of benzene-induced cytopenia.

  • DATS can prevent the cytopenia induced by benzene.

  • The oxidative stress-mediated PI3K-Akt pathway played an important role in the preventive effect of DATS against benzene.

  • The data sets the stage for further developing effective pharmacological agents to prevent benzene toxicity.

Abstract

Benzene is a well-known occupational and environmental toxicant associated with cytopenia, which is characterized by a disorder in the peripheral blood cell counts. However, no effective preventive strategy has been developed yet to tackle the exposure to benzene in daily life. The aim of this study was to evaluate the protective effects of diallyl trisulfide (DATS) on benzene-induced haematopoietic damage and to reveal its potential mechanisms of action. In our study, male Sprague-Dawley rats were divided into six groups. Rats were administered with benzene (1.3 g/kg BW by gavage) to establish the benzene poisoning model, while the DATS treatment groups were treated with benzene plus DATS (15 mg/kg, 30 mg/kg, 45 mg/kg, respectively, by gavage) for 28 days. Our results demonstrated that the counts of peripheral blood WBC and RBC decreased to 31.0% and 79.2%, respectively, in the benzene poisoning model group compared to the control. However, blood cell counts were restored by DATS treatment (30 mg/kg, 45 mg/kg). The apoptosis rates of peripheral blood mononuclear cells (PBMCs) and bone marrow cells (BMCs) were increased to 274% and 284%, respectively, following benzene exposure. Furthermore, expression levels of Bcl-2, PI3K and p-Akt were downregulated and those of Bax were upregulated in both cell types. Moreover, the oxidative parameters (oxygen species, malonaldehyde) were significantly increased, while the non-enzymatic GSH/GSSG ratios and the activities of enzymatic antioxidants (superoxide dismutase, glutathione peroxidase and catalase) were decreased. Interestingly, DATS treatment can restore the WBC number by 267.1% and 304.8% while RBC number by 108.6% and 117.7% in 30,45 mg/k DATS treated groups. In summary, we demonstrated that benzene-induced cytopenia was related to the apoptosis of PBMCs and BMCs, and DATS treatment could prevent benzene-induced cytopenia by suppressing oxidative stress-mediated cell apoptosis via the PI3K/Akt pathway.

Introduction

Benzene is a well-known occupational and environmental toxicant. Haematological diseases, such as cytopenia, aplastic anaemia, leukopenia and leukaemia are associated with benzene exposure (Ahmad Khan, 2007, Smith, 2010). It is reported that low levels of benzene (<1 ppm) exposure affected the blood forming system; however, there is no evidence of a threshold. An epidemiological study claimed that the white blood cell and platelet counts in peripheral blood of workers exposed to benzene (even below 1 ppm in air) were significantly lower than those observed in a control group of people (Lan et al., 2004). In recent years, several epidemiological studies have demonstrated that exposure of the general population to environmental contamination of ambient air, such as cigarette smoke, gasoline vapours, and automobile emissions, increases the risk of cytopenia and leukaemia (Crosignani et al., 2004, Moorman et al., 2002). However, no effective preventive strategy has been developed to date. Therefore, benzene exposure has become an increasing environmental concern for the health of workers and the general public.

There is considerable evidence supporting the hypothesis that metabolism of benzene catalysed by cytochrome P450 (CYP) and myeloperoxidase (MPO) plays an important role in benzene toxicity. In these processes, superoxide anion radicals and reactive oxygen species (ROS) are continuously produced and targeting on peripheral blood cells and bone marrow cells to cause damage (Ross, 2000, Uzma et al., 2010). It has been demonstrated that benzene exposure may affect the formation and differentiation of various haematopoietic progenitor cells and erythroid colony-forming units in bone marrow, primarily characterized by a decrease in peripheral blood cell counts at an early stage of benzene exposure (Ahmad Khan, 2007). The potential mechanism of benzene-induced toxicity is the overloaded-oxidative stress induced by ROS production during bebzene metabolism and imbalance in the antioxidant status (Uzma et al., 2010).

Garlic and its active ingredients have been used as folk medicine and strengthen food to reduce the risk of chemical poisoning, stimulating the immune system and protecting against bacteria or virus infection for several centuries (Tsai et al., 2013). The organosulfur compounds derived from garlic have been proved to possess antioxidant properties, such as allicin, diallyl sulfide (DAS), diallyl disulfide (DADS), diallyl trisulfide (DATS), dithiins, and ajoene (Amagase, 2006, Ho and Su, 2014, Tsai et al., 2013). And also it has been suggested that the number of sulfur atoms is critical in the biological activities of organosulfur compounds in garlic (Tsai et al., 2013). Garlic oil as the mainly effective products of garlic is a liposoluble extract primarily containing DAS, DADS and DATS (Zeng et al., 2013). Our previous study demonstrated that garlic oil efficiently inhibited the decrease in peripheral white blood cell count induced by CTX (cyclophosphamide)/radiation and benzene (Xu et al., 2014, Zeng et al., 2013). However, the effective compound in garlic oil responsible for the protective effect against leukopenia and its underlying mechanisms remain unclear. It was reported that DATS–one of the major liposoluble organosulfur components in the garlic oil–is responsible for some of the pharmacological effects of garlic (Gu and Zhu, 2011, Keles et al., 2014). Modern pharmacological studies support the hypothesis that DATS possesses the antioxidative property against several hepatotoxins, such as carbon tetrachloride (Shaik et al., 2008, Zhu et al., 2014). Hence, it implied that DATS–the organosulfur compound with the most sulfur atoms in garlic oil–might be a promising compound used as medication for the prevention or treatment of blood-system disorders induced by benzene.

The aim of the current study was to decipher the potential mechanisms of benzene-induced damage of peripheral blood mononuclear cells (PBMCs) and bone marrow cells (BMCs), and further reveal the effect of DATS anaginst blood toxicity. We observed that DATS inhibited benzene-induced oxidative stress by stimulating antioxidant enzymes and elevating the contents of non-enzymatic antioxidants, such as GSH in PBMCs and BMCs isolated from rats exposed to benzene. Furthermore, DATS inhibited oxidative stress-mediated cell apoptosis through the Akt/PI3K pathway.

Section snippets

Reagents

DATS (purity>97%) was purchased from Jiang Su Chiatai Qingjiang Pharmaceutical Co., Ltd. (Nanjing, China). The antibodies used in the study included Bcl-2, Bax, caspase-3, phosphatidylinositol 3-kinases (PI3K) p85, Akt (Thr308), β-actin, peroxidase-conjugated goat anti-rabbit IgG purchased from Abcam Co., Ltd. (Shanghai, China). Annexin V-FITC apoptosis detection kit was purchased from Vazyme Biotech Co., Ltd (Nanjing, China). Rat blood cells isolation kit was obtained from TBD Science Inc.,

DATS protected the haematopoietic system against benzene-induced toxicity in rats

Benzene is known to have toxic effects on blood cells and bone marrow, leading to haematopoietic progenitor cell injury and disorder in the peripheral blood cell counts. In the current study, mammalian model was established by oral injection of benzene in rats to evaluate the protective effect of DATS against benzene-mediated haematopoietic toxicity. We observed that exposure of benzene resulted in a dramatic decrease in the counts of WBC and RBC in peripheral blood, to 31.0% and 79.2%,

Discussion

Cytopenia, especially the decrease of peripheral blood WBC and RBC, is the early symptom of benzene poisoning that is observed clinically (Peng et al., 2013). In this study, the WBC count of benzene model group was statistically significantly decreased compared to those in the control group. This suggested that the benzene poisoning model was successfully established (Xiaojiang Tang et al., 2006). It was previously reported that garlic may promote leucopoiesis and increase the

Conflict of interest

The authors declare that they have no conflict interest.

Acknowledgements

The author thanked K.X. for designing research and supervising the project, W.H. and L.J. for analysing data and revising the paper, W·H., S·W., M.L., X.W. and H.W. for performing the molecular analyses and animal experiments. This work was supported by the grants from National Natural Science Foundation of China (No. 81373044).

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