Elsevier

Toxicology Letters

Volume 87, Issues 2–3, October 1996, Pages 139-145
Toxicology Letters

Research article
Hepatocytes from metallothionein-I and II knock-out mice are sensitive to cadmium- and tert-butylhydroperoxide-induced cytotoxicity

https://doi.org/10.1016/0378-4274(96)03770-8Get rights and content

Abstract

Metallothionein (MT) has been proposed to play an important role in heavy metal detoxication and in the scavenging of free radicals. Effects of MT on the cytotoxicity of cadmium (Cd), tert-butylhydroperoxide (t-BHP) and N-methyl-N-tro-N'-nitrosoguanidine (MNNG) were examined using primary hepatocyte cultures from control (C57BL/6J) and MT-I and II knock-out (MT-null) mice. Compared to control hepatocytes, MT-null hepatocytes had minimal Cd-binding proteins (MT equivalents), but cellular glutathione concentration was similar to the control hepatocytes. MT-null hepatocytes were more sensitive than controls to the cytotoxic effects of Cd (50–300 μM) and f-BHP (125–500 μM), as indicated by the levels of lactate dehydrogenase released into the medium. Cd and (-BHP also produced more lipid peroxidation in MT-null hepatocytes than in control cells, as demonstrated by the abundance of thiobarbituric acid-reactive substances. However, MT-null hepatocytes were equally sensitive as controls to the cytotoxicity of MNNG (0.5–2.0 mM), suggesting that MT does not protect against MNNG-induced cytotoxicity. These results support the hypothesis that constitutive MT levels affect the sensitivity of mammalian cells to Cd and oxidative stress.

References (31)

Cited by (46)

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    And the location pattern in the chromosome is conservative in the Drosophila genus (Luo et al., 2020). Based on in vivo and in vitro studies on MTs of both vertebrates and invertebrates as well as plants, two major cellular functions of MT system were found: regulating the metal ion homeostasis and maintaining redox balance (Thornalley and Vašák, 1985; Lazo et al., 1995; Zheng et al., 1996; Kumari et al., 1998; Fabisiak et al., 1999; Colangelo et al., 2004; Achard-Joris et al., 2007; Jia et al., 2012; Takahashi, 2015). In D. melanogaster, the protective function of MTs against metal toxicity was elucidated in detail through studies of polymorphisms in naturally duplicated loci, knockout, and overexpression of certain MT genes.

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  • Metallothionein-I/II null cardiomyocytes are sensitive to Fusarium mycotoxin butenolide-induced cytotoxicity and oxidative DNA damage

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    In contrast, induction or overexpression of MT effectively protected against the oxidative injuries associated with streptozotocin (Cai et al., 2005), doxorubicin (Shuai et al., 2007) and ethanol (Zhou et al., 2002). Cells overexpressing MT or cells isolated from MT null mice displayed similar responses to oxidizing agents (Lazo et al., 1995; Zheng et al., 1996; Wang et al., 1999; Wang and Kang, 1999). In summary, our present study clearly shows that MT-I/II null cardiomyocytes are more sensitive than wild-type cardiomyocytes to the toxic effects of BUT, confirming basal expression of MT protects cardiomyocytes against BUT-induced cytotoxicity via inhibition of ROS production and the associated DNA damage.

  • Basal expression of metallothionein suppresses butenolide-induced oxidative stress in liver homogenates in vitro

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    Many in vivo studies have demonstrated that MT null mice are more sensitive than wild-type mice to the toxic effects of oxidative stress-inducing agents such as acetaminophen (Liu et al., 1999b), carbon tetrachloride (Davis et al., 2001), doxorubicin (Kimura et al., 2000) and dimethylarsinic acid (Jia et al., 2004), and the mechanisms may be associated with the antioxidant activity of MT. In contrast, several studies have also proven that MT overexpression provides effective protection against the oxidative injuries associated with ethanol (Zhou et al., 2002), acetaminophen (Liu et al., 1999b), streptozotocin (Cai et al., 2005), and doxorubicin (Kimura et al., 2000; Shuai et al., 2007). Furthermore, experiments with cultured cells transfected with MT genes and cells isolated from MT transgenic or knockout mice produced similar results to oxidative stress-inducing agents (Schwarz et al., 1994; Lazo et al., 1995; Zheng et al., 1996; Wang et al., 1999; Kimura et al., 2000). Therefore, our present study is designed to reveal the antioxidant potential of basal expression of MT against butenolide-induced hepatic oxidative stress using MT-I/II null mice and the corresponding wide type mice.

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    The 75-aa-long CgMT1 isoform contains 21 Cys residues arranged in a typical Cys-X(1–3)-Cys motifs, whereas the 107-aa-long CgMT2 isoform displays an uncommon tri-domained α-β-β structure and contains 30 Cys residues [3,4]. MTs display in vitro antioxidant function [5–7], and in vivo experimental evidence has used cultured cells from transgenic MT-null mice deficient in mt-1 and mt-2 genes [8–10]. MT antioxidant properties may derive both from sulfhydril nucleophilicity and from metal complexation.

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Present address: Cancer Center-0812, School of Medicine, University of California, San Diego, 9500 Oilman Drive, La Jolla, CA 92093-0812, USA.

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